Model Boat Mayhem
The Shipyard ( Dry Dock ): Builds & Questions => Navy - Military - Battleships: => Topic started by: SinWin on September 21, 2009, 08:29:30 pm
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Hi!
I'm currently building a 1/20 model of KNM Knurr of the Norwegian Tjeld class MTB (http://en.wikipedia.org/wiki/Tjeld_class_patrol_boat), in use in the Norwegian Navy from 1959 until ca 1980. The class was constructed by Herman Linge, who also constructed many other designs, both for the Norwegian Navy and the civilian market. The boats were used not only in Norway, but also in the USA, Germany, Greece and Turkey. They were built of mahogny, had a depl. of 82 tonnes and a top speed of over 45 knots (unofficial record said to be over 50 knots). They were powered by two Napier Deltic Turboblown diesel engines, each producing 3100 horsepower.
In the Norwegian Navy, they were armed with 1x 40 mm Bofors gun, 1x 20 mm Oerlikon (later 12,7 M2 Browning) and four 21'' torpedoes (ex. German G7a torpedoes from WWII).
This is only my second ship model, my previous model is Smit Nederland from Billing Boats. I have bought a 'finished' fiberglass hull from the Norwegian Naval Museum, but everything else I have to build myself; a challenge I look forward, yet fear with my limited experience.
I'll post a picture of the original here, and then get on with some pics of my progress soon.
(http://arkitekturnytt.no/uploaded_images/tjeld_MTB-747193.jpg)
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Hi
Looks an interesting project!
Keep the pictures coming of your progress.
If you get stuck ask on here - someone will have an answer!!
Cheers
longshanks
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Thanks, Longshanks =)
Since I've never built a model from scratch before, I spent a long time wondering how I should build things. A 'manual' came with the hull, giving brief hints and ideas about how to do this and that. Unfortunately, I haven't a picture of the hull before I started construction, but this is as close as it gets to how it looked originally:
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_0188.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_0188.jpg)
I decided pretty early that I should try to make the superstructure out of metal, brass, that is. I thought that could be a great experience, and might be more fun than making it out of plywood. Fortunately, I have one of those small electric table top scroll saws, which can also cut thin metal, so all I needed to do was to scale down or up any drawings I could find, and cut out metal pieces. I then soldered them together, and I must say the result is pretty good - a lot of work went into this. The actual bridge is watertight, with a drainpipe soldered on to it, as to drain any water spraying up into it, or at least make it easier to remove any water.
This picture shows how the superstructure looked a few months ago:
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_0176_s.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_0176_s.jpg)
Of course, there are lights in both lanterns, and the top lantern. A modified servo will have the radar turning.
(I apologize for the poor quality of the photos, they are taken with my mobile phone... I promise to find some of better quality.)
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After a long time, I went ahead and ordered the RC equipment for the model. Limited budget meant that I could not buy exactly what I wanted, but I think it will work.
My plan is to be able to run the two engines individually, have a working radar, the ability to remotely turn the lights on and off, and a turnable 40 mm gun. Counting the servo for the rudders, that should call for 6 channels.
In addition, I bought two graupner speed turbo 700 9,6V motors (can anyone explain to me what the "700" and similar numbers (e.g. 400, 350) refer to?), which I think should give me adequate power. The shop I ordered from recommended some electronic speed controllers from Graupner, just too bad they did not work when I finally got to try them. More on the fitting of electronics etc. in my next post.
I'm currently having trouble finding suitable propellers for my model, and any help here would be appreciated. Currently, it features two 40 mm bronze propellers, but they are not made for high speed and the high rpm my engines produce (14800 rpm, 7700 under load according to the producer) . A photo of the propellers on the original boat can be seen below. Any suggestions here? I think what I'm looking for is some sort of speed propeller, but I'm lost in the propeller-jungle.
My fitting of shafts, propellers and rudders:
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_0191_s.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_0191_s.jpg)
Original propeller:
(http://i599.photobucket.com/albums/tt73/sinwin/th_Nastypropell.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=Nastypropell.jpg)
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If you would like scale propellers that match the appearance of the actual propellers you could contact George Sitek (www.gsitek-props.co.uk) and he will make them for you. He gives excellent service.
Roger.
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I'll check it out, thank you. But will propellers matching that of the original will be better for me than any other propellers?
Oh, and I might add that my shafts are 4 mm in size, with a threaded M4 attachment.
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George can make the props to fit an M4 attachment. I think scale props will look better, but you may get better performance from race props so it is up to you. (Here is another shop to try for scale props: www.prop-shop.co.uk)
Roger.
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Deans Marine do a good selection of Raboesch props
http://www.deansmarine.co.uk/html/propellers.html
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Thanks for all your suggestions. Deans Marine looks like a good place to start (I'm afraid specially built propellers might get a little costy), trouble is finding the right propeller for me. Perhaps the C-type propeller? And then there is the question about size.
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If you are using direct drive I think the general rule is your props should not be greater in diameter than your motor. Check out this link for information on the Raboesch 'C' type propellers: www.raboesch.com/propellers/4_c_l.htm
Roger.
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Yes, it is direct drive.
If the rule about propeller diameter is correct, my propellers can be no bigger than 42 mm. I guess that makes sense. Perhaps the RABOESCH C-type is the best bet? As opposed to the 3 blade A-type I have today.
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Inside the boat I had to mount the two Graupner 700 turbo C engines to something that would hold them tight, yet something to absorb vribrations and make them able to self-adjust to some degree. In my previous model, I had simply drilled two holes in a wooden beam, and mounted the engines (a pair of 400s) inside those, with some support on the back side. It works, but it is not a very effective cooling method... I sometimes smell burnt wood when I open up the deck of that boat. Oh, well.
In the Tjeld-boat, I wanted something that will make me able to cool the engines more efficiently - obviously there is going to be some more heat generated in this model with these larger engines. Still, though, I stuck to a wooden method. At first, I mounted the shafts, and then measured where the engines should sit. I then, again, found a wooden beam and drilled two holes, a little bit larger than the engines themselves. I then cut the beam in half, slicing it so that each of the two holes were now merely a "crib" for each engine. I then glued this in place, of course taking care to fix it in the right position.
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_1646.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_1646.jpg)
As couplings to the shafts I used some metal pieces joined by a heavy duty piece of rubber, which allows the engines to be a little bit off centre to the shafts. To fasten the engines, I laid a rubber mat in the bottom of each crib, to prevent them from turning themselves around, and then fastened them securely in place using pieces from a Meccano toy set I bought for this purpose. I also use meccano to link the servo to the rudders, and for a lot of other things in the inside of the boat, and I find it to be very efficient and durable.
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_0266.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_0266.jpg)
I bought four lead acid batteries, 12 V and 7,2 Ah. However, I found that I could only fit three inside the boat because of the wheight, there is ample space for plenty more. I placed them just forward of the engines. The speed controllers were fitted just beside the engines, so that the cooling fans I am going to point at the engines will also draw air over the speed controllers, and thereby cooling them as well.
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_8052_ed.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_8052_ed.jpg)
The fans are not in place at this picture, this is just me adjusting the mounting of the engines.
The speed controllers were a pair of Graupner Navy V30R.
The interior after test-fitting everything:
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_0012_org.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_0012_org.jpg)
The batteries are fitted inside 3 mm plywood, glued into place and strengthened by pieces from the Meccano set.
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A clever use of Meccano. Well done for thinking of it.
May I suggest laying the strips flat across the motors and bending down each side to secure them to the wood. This would improve the grip and secure the motors better. Let me know what you think.
I like the rubber pads underneath. This will smooth things out a treat.
ken
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Thank you!
Yes, I considered doing what you describe, but I'm afraid the Meccano steel is rather stiff, and such a solution would call for high accuracy in bending the steel, I think. I considered using - something I don' know what to call in English - but a softer strip of metal which bends fairly easy, but I have used Meccano in my tug model, and found it useful in may ways, so I went ahead and used it here too. (And, frankly, I did not have any of that softer metal around.)
I think, though, that you're right that it might secure the motors better, however, the Meccano is securely fastened to the wood by fairly long and strong screws, and I don't think they'll come off in a hurry. The engines are also tightly placed, and the forward Meccano strips are placed so that it rests in the cooling slots, making it very difficult for the engine to rotate very much. At the same time, that makes it very difficult for the engines to move up or down (in the direction of the shaft).
But, perhaps you're right, and I'll have to change the design some time in the future?
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My pleasure. :-))
The way the strips are (vertical) would certainly hold the motors down in those grooves, as they are at their strongest in this position, but I thought the motor might move forward or backwards against the bend of the steel, but you say they are difficult to bend. The steel must have improved since my days of Meccano, as I remember it was very bendable back in 1952. :embarrassed:
If you do find a weaker material strip (aluminium!) then flat would be the way go, as you suggest.
Watching with interest
ken
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My father was explaining to some people at his job the other day what Meccano was and how he wanted it when he was a child: one of them googled it, and said "oh, yes, here we are: Meccano: steel toy set from the beginning of the previous century" - what a punch. (Luckily, now he has a job which allows him to buy things like that with the excuse that it is used in education of teachers and such.)
The boats were originally fitted with one L/60 40 mm Bofors gun aft, and a 20 mm Oerlikon forward, in addition to four 21'' torpedo tubes.
I'm starting off with the 40 mm gun. The fist thing I had to do was to measure how much I had to scale down the drawing I had to fit it in 1/20 scale. I then started off by making the base of the 40 mm. When I had done that, I could go on with making the shield around the gun etc.
The base was created by cutting out a 40 cm long and 2 cm high strip of 0,2 mm thick brass, bending it carefully into a circle, and then soldering it together. I then soldered on some supports, lying them in a cross to keep the circle in shape. However, I want the gun to ble able to rotate from side to side, and if so, the cross of the tiny bar will be blocking access for the axle I need. I therefore soldered one of those key-rings on to the bars, and cut them so that an axle will have no obstructions in passing, whilst at the same time retaining the strength to support the circle.
The base:
(http://i599.photobucket.com/albums/tt73/sinwin/th_400bottom.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=400bottom.jpg)
I then cut out the "floor", "deck", or whatever you will call it in a gun, and fitted a ring slightly smaller in diameter to the bottom of this. The two rings fit tightly to each other, and assures that the top will keep in place on the basement. Later, I also discovered by accident that I had a ball bearing lying around which fitted exactly into the hole of the key ring (?) as if it was made for the purpose. I've had that ball bearing lying around for seven or eight years! This means the gun will be able to swing very smoothly, I assume.
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_1695.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_1695.jpg)
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Hello
Great fun to se a fellow norwegian modeller here. I have a half-finished mtb of the Hauk-class at home, and this gives a little inspiration to finish that one.
About the mecano: It is possible to use 'patentbånd' for the same purpose. ('Patentbånd' is a Norwegian word, don't know the english word for this. It is a flexible metal band with holes, directly translated it means 'patented band')
Could you also tell me how you got the hull from the Naval Museum? Do the produce and sell hulls?
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Yes, patentbånd, that's what I was thinking of.
Originally, the Naval Museum sold both Storm-class and Tjeld-class hulls, but when I was going to buy one, the Storm-class was sold out, so I bought the Tjeld instead. I don't think they have any hulls left now, I bought mine a few years ago. I think some person made them, sold them to the Naval Museum who in turn sold them through their website.
Building the Hauk class sounds very interesting, I would like to build that myself some time.
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SinWin....your electric motors are designed & provided with M3? tappings in the output shaft endcaps............these are designed to hold, secure & align the motors steady against motor vibration & hull resonance
It's not too late to redesign the motor mounting.....it would make for a stronger structure & eliminate future vibration issues.......................... Derek :-))
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Thanks for the tip, derekwarner_decoy - however, I've already tried to mount something here, but I needed some kind of metal bars to secure the engines, and once again I had to be very accurate to make it fit, and not fasten the motors correctly aligned with the shaft. This proved very difficult, so I had to abandon the idea - at least for the time being.
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derekwarner - now that I think about it, I think it would perhaps be a good idea to give those M3 tappings another go, I'll just have to be even more accurate when I bend the metal, I suppose...
The detail of the 40 mm gun and all those small parts I have to make for the gun frightens me a little - I'm not very good at details, I tend to be too impatient at times. However, making the shield for the gun should be straightforward:
I started by, once again, scaling down or up the measurements from a drawing I had, and putting this over to some cardboard, then drawing it all onto a sheet of metal. I try to make cardboard fittings of everything I cut out, so that I can easily remake some parts if something goes wrong.
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_1685.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_1685.jpg)
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_1686.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_1686.jpg)
Unfortunately, the shop where I buy my material stopped selling 0,2 mm thick brass plates, and now just sells 0,5. It's a bit too thick for comfort, but fortunately, my beloved saw handles it, the only problem is to bend it accurately.
I do much of my model work outdoors, as to minimize the noise and dust indoors. Fortunately there are few (actually just two) neighbours, and they don't complain about any noise, so my little saw is no problem for them.
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_1688.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_1688.jpg)
I don't think I would have gotten very far without this thing, it really makes accurate cutting both faster and much, much simpler.
Shield cut out and nearly ready for mounting:
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_1690.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_1690.jpg)
And finally, the shield is mounted, being soldered on to the base of the gun:
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_1692.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_1692.jpg)
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_1695.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_1695.jpg)
I soldered it on from the bottom, thus hiding the "weld" as best I could.
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SinWin...when I mentioned M3 tappings.....it was just a guess as the Graupner WEB site does not specify this threadform.....some European manufacturers use the American UN thread form of 2-56 which is 3.38 mm diameter ..so an e-mail to Graupner should resolve this
Another point for consideration is using the motor front endcap spigot to align the motor & simply use the two tapping's for final securing..... O0..........Derek
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Yeah, that's an idea. I'll have to see if the engines will vibrate or show any signs of "running away".
I'm employing a Graupner MX-12 sender for this boat. It gives me 6 channels, and the possibility of controlling both engines individually at the flick of a switch. It's not the best choice, but it works. I plan on having both the radar and the lights controllable from the sender.
Before installing all the radio equipment, I painted the hull and the deck. Originally, the boats were painted with a green hull and superstructure, and a grey deck, but were later given an all grey colour scheme. I want my model to be the green variant, so those were the colours I had to get. Finding them proved difficult, though: I had some colour codes for them, but were unable to "translate" them into humbrol colour codes, which I use for other models. Finally, I went to a local shop where they sell "everything" (=everything else than you need when you go there), but at least they had paint, and the colour codes were not unknown to them. I got hold of some outdoor paint in the right colours. Unfortunately, it is rather thick, and I was not able to use it in my airbrush, so I used a regular paintbrush instead... well, I guess the result is not at all perfect, but it works for me.
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_0264.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_0264.jpg)
Red paint added to the bottom...
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_1645.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_1645.jpg)
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_1648.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_1648.jpg)
And green paint added to the hull.
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I was thinking of ordering some propellers - I've decided to try the Raboesch C-type, and I'm thinking of 45 mm. However, I wonder: four or three blades? Any suggestions?
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I also painted the superstructure:
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_1697.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_1697.jpg)
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_1699.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_1699.jpg)
When this was done, it was time for the frist test drive...
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Unfortunately, the electronic speed controllers failed completely at the first test launch. When we arrived at the test site, I found that only one of the motors were turning - I blamed this on a malfunctioning sender, but after checking we found that not to be the case. We decided to try the boat with only one motor working, just to see how it behaved - about five metres out in the water, the last ESP too failed, but fortunately it was still able to run backwards, so we got the boat in to shore.
Returning home, we tested and found that the ESPs had failed. I returned them to the dealer, and were sent another type a few days afterwards.
Pity, but I guess something has to go wrong.
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_0025.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_0025.jpg)
Well, this was as far as it got before the remaining speed controller failed... Hope the new ones will be better.
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After long consideration, I finally thought of a plan how to fasten the deck to the hull. The deck totally covers the hull, and I've considered gluing the whole deck to the hull, and cut holes here and there for access, but I can't help thinking that it will really help being able to take off the whole deck.
What I'm thinking is to drill four holes in the deck, through which I'll stick four screws. On the hull, I'll fix four nuts, which the screws can be fastened to, thus holding the deck in place. It works in theory, but it was a bit difficult in practice.
I've tried to build the screws somewhat camouflaged:
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_0319.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_0319.jpg)
The holes where they will stand, is as close as possible to where these things stood on the original.
Underneath the deck, I once again used Meccano, glued in place and with the nut soldered on:
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_0320.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_0320.jpg)
And finally, I was able to mount the deck on to the hull, and get an impression of how it'll look some day. I've cut small pieces of a rubber mouse pad to fit under and around the screws, so that they won't destroy or scratch the deck, and keep it watertight.
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_0334.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_0334.jpg)
However: How on earth am I going to make this watertight? Have you any suggestions? I have to come up with something to put between the deck and the hull to seal it. I've tried some K-profile rubber used to seal windows and such, I glued it to the deck, but it did not work as intended.
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Before fitting the deck, I received two new speed controllers in return for the two faulty ones. These were of some other brand, and they actually work.
After fitting them, I had to wait long to find a day when the weather was suitable for a test run - and what a test! The boat performed perfectly, going fast and making beautiful waves.
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_1738_s.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_1738_s.jpg)
Full speed - however, this is with the original slower speed-propellers I had. I have now bought some new propellers, but I've not had a chance to test them yet. I suspect it will go even faster with the new ones.
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_1737_s.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_1737_s.jpg)
I also took some video of it, which can be seen here: http://www.youtube.com/watch?v=eT72zrfuMpE
However, I'm still wondering how to fit the deck... any suggestions at all?
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After reading my previous posts, I see that my language is not the best, and my questions are vague and open for interpretation. I'll try to put it straight:
The hull is one separate part, and the deck is another. The deck is designed so that it will fit over the hull, the deck resting over it with about half a cm sticking out all around the hull, and there is also a downward-facing edge on the deck, about half a cm.
I'm trying to think of a method to fix the whole deck to the hull. In order to do this, I have drilled four holes in the deck, and fitted four nuts to the hull, corresponding to the holes in the deck. Thus, I can fit four screws which will hold the deck in place.
As can be seen in the video and pictures in the previous posts, the boat makes a rather large bow spray, higher than the hull. When the deck is fitted, the bow sprays will reach up to the deck, but because of the edge on the deck, the bow spray will be directed to the inside of the hull, where it of course is not supposed to be. I have tried to fit a K-profile weather strip to the deck in the hope that it would make the connection watertight, but it did not work as intended, and the hull was filled with a litre of water after only a short time on the water.
The question is: how am I going to make the 'connetion' between the deck and the hull watertight? Any suggestions?
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If I was you I would permanently bond the deck to the hull to prevent water ingress. I would then cut a lift out section around the bridge in the deck (and fit the deck with flanges)for access to the batteries, speed controllers etc..
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Thank you for your reply! It is perhaps the best idea, and I guess the only way to make it completely watertight.
However, when you cut out parts of the deck, how do you make the gap between the lift out sections and the fastened deck watertight? Would a K-profile weather strip be any good there? I guess it will never be completely closed for any water ingress, but at least I want to prevent what ingress I can.
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If you fit flanges to the underside of the deck for the lift out section to sit on, you may be able to use a gasket formed from a thin layer of silicone rubber to waterproof the join. It should be reasonably watertight if the lift out section is held tightly in place.
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That sounds like a good idea. I think I'll try to cut the whole deck about 2-3 cm inboard from the sides, and glue what will remain as a frame to the hull. On that frame, I will fit some flanges and supports, and then use my screw-method of fixing the deck in four places, perhaps with the addition of some self-made 'sliding locks' or something. That way I can still have access to most of the interior, but will not have the problem with the bow spray.
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Rather than make an arbitrary cut - may I suugest you try and make the cut along a line in the deck so that the cut 'disappears'? Eg where the deck meets the superstructure.
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Nice model, I like your video of test drive. O0 O0 It also rememmbered me to run my KNM Snogg. ok2
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Thank you all for your suggestion and nice words, and thanks for the comment on the video.
I'm still thinking about how to make the cut gentle, and will hopefully come up with a solution soon. I tried another way of fitting the rubber weather strip today, but it did not work out, so I will definately have to glue the deck on to the hull in some way.
I changed the propellers today, and I must say, this is more like it:
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_0525.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_0525.jpg)
Comparison between the old propellers and the new ones:
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_0524.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_0524.jpg)
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Some photos from the test drive with the new propellers:
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_0573_s.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_0573_s.jpg)
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_0575_s.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_0575_s.jpg)
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_0576_s.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_0576_s.jpg)
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_0585_s.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_0585_s.jpg)
She rides a bit heavy in the water, and proves a little difficult to control, she leans to one side and can be hard to bring over in a turn. I would think that the weight affects the steering, so I'll try to remove one of the three batteries and see how it does. Going from 21,6 Ah to 14,4 Ah will reduce the running time, however, I could bring extra, charged, batteries along anyway.
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SinWin...yes the latest photographs suggest the hull has marginal bouyancy...however this was not 'as' apparent in the previous photographs.........
You suggest the only difference are the revised twin props?........ :o ...............Derek
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Yes, so it seems. I should have noticed when I installed the batteries, but I then thought that the hull should manage the extra wheight. It was "only" a cm or so over the waterline I had painted. I suppose the extra weight is the main reason for the 'sluggish' behaviour in the water?
And yes - the extra speed must be due to the new props alone: they are the only thing I changed from the last set of photos/video on the water. I can't help thinking what the speed and handling will be like when I remove one of the batteries, they weigh 2,7 kilos each.
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Having consulted the family's engineering expert and technician, we've agreed on where to cut the deck, and how to fasten it to the hull. With one exam remaining this semester, I'm looking forward to my Christmas holiday with time off to do some modelling. I'm still looking for cheap 40 mm computer fans, though. Perhaps I ought to scan ebay or dealextreme. Fans that size will be cooling the engines. I'm also working on an automatic bilge pump. I'm thinking of making one of the original exhaust vents double as an outlet for excess water, though I hope the pump will be redundant.
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Hello SinWin,
Great project. :-))
I have studied your photos with interest and if I may I might make a small suggestion to help your boat speed through the water faster and smoother.
The guy that taught me how to build boats when I was a young lad sailed motor torpedo boats using glow plug internal combustion engines.
The under side of the hulls were painted and then sanded with progressively finer wet and dry glass paper until they were highly polished.
Then on top of this he used car wax polish. :-))
All this effort made his torpedo boats ride over the water very smoothly and fast making beautiful clean bow waves.
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Thank you for your interest and kind words. Your proposal sounds like a very good idea. My paint now is not very smooth, so sanding it and using car polish just might do 'a', if not 'the', trick.
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SinWin....I understand & agree with the reduced water slip as offered by Greg.....but as %% as it may sound lets think
1) what happens if we consider that the hull is not travelling faster .....but the water covered per given time is greater O0....one may argue that these two comments contradict :-))
2) the result is for any given body of water.....is that technically the hull will sink "marginally" lower in the water :embarrassed: .......fact......Derek
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Perhaps - but would not the decreased drag make up for that? Or would it kill the speed, and make for worse handling in the water?
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Hi SinWin, I like your model ;)
How long/wide is the hull? Are your (3) batteries 12v 7Amp/hour rated? Are your 2 rudders to scale?
I may be able to help with the speed/handling problems but the questions above are important and your answers would help members. :-)
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Hi, Perkasaman! Thank you for your comments.
*The hull is in 1/20 scale, which makes it 122 cm long, and 37,5 cm wide.
*I'm going to take out one battery to help weight problems, leaving two 12 V 7,2 Ah lead-acid batteries. They weigh 2,7 kilos each.
*My two rudders are slightly larger than the original, as far as I can see from drawings and pictures. They are, though, those recommended for me by the museum I bought the hull from, and replicate the shape of the original rudders rather well.
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Hi SinWin, My Vosper 'Perkasa' is 124 cms long and very similar to your mtb. I put a lot of information/photos on the forum and it may be helpful.
Forum Section: DRY DOCK
Category: WARESHIPS & MILITARY
Thread: 'Perkasa restoration'
A member was restoring a 124 cm Perkasa model and we exchanged ideas/information. :-)
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Thank you so much for showing me that thread. I think many of your hints and tips there might help me. However, first I have to try the model with only two batteries and deck fitted, and see how it does.
That said, I'm sorry for my late reply, I'm currently enganged in preparing for my last exam this semester. Luckily it will be over soon.
For future reference, the thread in question is http://www.modelboatmayhem.co.uk/forum/index.php?topic=18030
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I'm currently scanning the web for a small continious rotation servo, which will be used for turning the radar. I've tried modifying three small servos myself, and it works, but they make a lot of noise and do not move even, so I think I have to go with a servo that was made to rotate all the way around.
Does anyone know of a reliable webshop who sells servos like that? Preferably one who ships internationally (i.e. Norway). The local shop where I live once again turned out to be useless...
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How about this instead of a servo?
http://www.action-electronics.co.uk/pdfs/M7G.pdf
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Looks interesting, as long as it can be remotely controlled in some way - I want to be able to switch it on and off from the transmitter, and I figured a premodified servo would be the simplest solution; just plug into the reciever and you're ready to go. I know these servos exist, but I'm unable to find a suitable and reliable (in other words a web shop I can trust) seller for these servos that ships internationally. Either they don't exist, or my google-skills are way below par...
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Hi Sinwin, :-)
'Robbe' sell modelkits and parts.......... They also 'sell mini geared motors' in many ratios - 100:1, 250:1, 500:1 and 1000:1 which run at 6volts. I bought one of these tiny 6v units ( model No. 4124 - 500:1 ) from a model shop in the UK to rotate the radar on my Perkasa. I never used it, but these are the units which are perfect for spinning radar. This unit is available/sells for £25 here in UK and should be easy to buy in Norway. My model shop sold me the 500:1 type but you can check that this ratio choice will give the speed you want from a supplier before you buy. ok2
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Thank you all for your help. I found a Norwegian supplier of Robbe-parts who were willing to help me, and have now ordered two on/off-switches for my reciever (to power on/off the lights and radar), and one mini geared motor - possibly a too slow, but we'll se (1000:1). I'm looking forward to seeing how well it works.
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I've just tested the small motor, and it spins too slowly, however, that was a perfect excuse for buying the 500:1 motor as well, so I've now ordered that one.
However, I did get two on/off-relays which can be used for switching on and off lights and such. I did not know those things existed prebuilt, so I'm happy I asked the shop if they had something like that before I ordered.
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I would like to have the Robbe + Graupner catalogues to find out exactly what other gizmos/fittings etc. are available - the items I have bought were expensive but good quality. :-)
The twin Napier Deltic diesel engines fitted to the Tjeld were amazing engines - 2 stroke/36 pistons/triple crankshafts - each! :o
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Indeed. When you think that those engines powered large locomotives designed to haul heavy loads on track, and you place two of those engines in a small, wooden hull - fit some torpedoes and a few guns - and there you have a powerful, fast and agile military vessel. I was not aware that the Hellenic Navy actually still uses four Tjeld-boats as patrol craft, but they do! Some links: http://www.hellenicnavy.gr/andromeda_p196.asp
http://www.hellenicnavy.gr/kyknos_p198.asp
http://www.hellenicnavy.gr/pigasos_p199.asp
http://www.hellenicnavy.gr/toksotis_p228.asp#a1
The design of the deltic engines are special - the triangle setup had me scratch my ear for some time to figure out how it could work.
I have always thought that one of the Tjeld-boats were preserved at the Norwegian Naval Museum, but my brother visited the museum the other day, and called me: no Tjeld-class were there. So, where is it? He was told the boat is somewhere here in Bergen (the Naval Museum is located in the eastern part of Norway, near Horten, as opposed to Bergen on the western coast), but I can't think of anywhere else it could be in Bergen but the Haakonsvern Naval base - off limits to civilians, of course...
I have today tried and tested a solution for an automatic bilge pump, but it did not work. It seems I just have to fit the pump, and make a switch for it so that I can easily operate the pump when I bring the boat up on dry land. I'm curious about the 500:1 engine. It's expensive, that is true. I hope it has the right speed for turning the radar, so I don't need to buy yet another motor :p
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Perkasaman says.... "The twin Napier Deltic diesel engines fitted to the Tjeld were amazing engines - 2 stroke/36 pistons/triple crankshafts - each!"
>>:-( <*< <:(...amazingly complicated may be a better description %% %% %%...however never designed for maintenance @ sea....... %) .......Derek
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I have always thought that one of the Tjeld-boats were preserved at the Norwegian Naval Museum, but my brother visited the museum the other day, and called me: no Tjeld-class were there. So, where is it? He was told the boat is somewhere here in Bergen (the Naval Museum is located in the eastern part of Norway, near Horten, as opposed to Bergen on the western coast), but I can't think of anywhere else it could be in Bergen but the Haakonsvern Naval base - off limits to civilians, of course...
i found some info about the remaining Tjelds:
There are three norwegian Tjeld-class boats left. One is owned by the naval museum in Horten and will be displayed in the museum (on land), one is in Fredrikstad and will be fixed up and running as a floating museum, and the last one is used as parts for the one that will be running.
more info (in norwegian) and some pictures can be found here: http://www.tmbk.no/delf1no.htm
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I hope they'll get it out for display soon, I wonder where it is for the time being. A good thing, though, that three of them are preserved!
I'm currently investigating (with a lot of help) ways of making an automatic bilge pump for the boat. I have the pump, and was planning on just placing it in the hull with a simple switch for on/off operation on land when the boat should be emptied of any water, but it would be great if I managed to have it work automatically. It's not my top priority, though.
It was my last day at work before Christmas today, at last there will be time for some building!
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Hi Sindre ,A car windsreen washer pump may be used - they are small and light BUT usually run on 12v??? - An inlet tube could remove water from water collected at the stern and pumped out through a side outlet fitting - when planing (bow lifts) water collects/flows there. A multi channel radio could operate the pump.................. or a pressure switch can be installed which is only pressed/activated by one of the rudder arm at full arc/swing- during either a full left or right turn - use during high speed run (when bow is lifted). Simple solutions are usually the best if possible. Your main batteries are 12v for pump power supply? good luck :-))
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A windscreen washer pump is exactly what I have bought =) It runs on 12 V, and I use one in my model of Smit Nederland, where I run it at six volts. It works very well, and makes it easy to drain the hull after use.
I have the possibility to use one of the channels on my sender to activate the pump, but I would also very much like it to be automatic! I'm therefore thinking of some way of building a small scale controller to activate the pump at a certain level of water, and deactivate it when the water level sinks below a certain level. It would be fun, but it is not my top priority. The main point is to hot have it go constantly on and off, which I'm worried would be the result of for example having the pump being activated by the rudder at full swing etc. My main problem is that I'm no electric engineer...
The plan is to use the internal 12V batteries, yes. I'm installing the pump anyway, with a simple switch for use when the boat is taken up on dry land. Priority number one, though, is to make the boat as watertight as possible.
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Sinwin.....I must agree....."Priority number one, though, is to make the boat as watertight as possible"
Also remember there are two types of windscreen washer pumps...one is a gear pump [positive displacement] the other is an impellor type...although either would be OK in this application...have you considered using the pump as a fire monitor?
Sorry.......but I don't understand why your Smit Nederland would also take in water...... %%..............Derek
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I think the one I've bought is of the impellor type. It is very cheap and not of the best quality, but it works.
My Smit Nederland is the first boat I built, and I have a feeling that some parts of the assembly manual were missing. A few drops of water enters through the shafts, but most of the water enters the hull via the cuts in the deck. Of course, that only happens when the boat is riding in «heavy» seas, but still.
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You mean like this?.......... :-)) these .jpgs are just normal life in our Sydney harbour........& not @ sea......
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Something like that - on a much smaller scale, of course :p I run it on small lakes and ponds, as well as in seawater; the latter of which offers somewhat larger waves and rough water.
So that is just in the harbour? Looks rough..
Does anyone know of a method of slowing down servos? I was thinking of slowing the one which are going to turn the 40 mm gun down. The gun was turned by hand on these boats, so I don't need a very quick servo. Would it work just fitting a resistor to one of the cables (that is, + or - and not the third "control"-cable)?
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SinWin ....there are purpose designed "electronic servo slowdown" components available............... suggest you contact [Action Electronics].......... FLJ here on Mayhem ...
With respect to the water conditions .....yes the .jpgs as shown are certailny a heavy water .....but can occur at any time of year in Sydney harbour when crossing between the North head & South head of Sydney harbour........
For the squimish........stay @ home.....for the lovers :-)).....get a return ticket & stay on board all day O0 {-) Derek
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That's an idea. I will have to see how much I'm going to fiddle with the servo for the 40 mm.
Today I finally made some progress again: with help from my brother (who is far more accurate and clever than me) we cut out a piece of the deck. It is so big there's no problem accessing the batteries, motors and servo, and yet I think it will be possible to make it fit very well. The cut has been made behind the superstructure, and in a place where it will be somewhat hidden by the two aft torpedo tubes.
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_2923_2.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_2923_2.jpg)
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_2925_s.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_2925_s.jpg)
I've also revised the rudder servo placement. Earlier, it rested in the bilge, making it vulnerable to water damage. I've lifted it up, using the longest bar from the meccano set.
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_2922_s-1.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_2922_s-1.jpg)
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A short video showing the radar: http://www.youtube.com/watch?v=FR0QtwMup_I
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Very impressive ok2
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Hi ya there SinWin
Having a look at your last two photographs and I noticed that around the edge of your hull, at deck level, you havent any support or a flange. Is this done purposely - do you have a mating flange which sits inside the hull on the underside of the deck? Because, with the thinness of the hull its giving you a very small cross-section contact area to seal on the underside of your deck.
It may pay you, if you wish, to have the whole deck removable all of the time, to fit some form of flange around the inside, and use a silicon sealer on the top. You have possibly already thought of this, but, it was just a thought whilst looking at your photographs.
aye
john
bluebird
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Thank you both for your comments. I haven't had the time to update the thread for a while, but some progress has been made. 40 cm of snow and lovely weather means most of the time is spent outdoors, though. It is not possible to ski here on the coast every year, but this winter has given us lots of snow and near perfect conditions. Last time people skied out here, I am told, was the winter of 1978/-79.
I would like to be able to remove the whole deck, but I have tried to make the seal watertight, and have not succeeded. After weeks of thinking, I decided to make a cut in the deck behind the superstructure, to give me access to batteries and electronics. The main part of the deck will be glued on to the hull with araldite, and a seal of silicone on the outside. The pictures above were taken just after the cut had been made: these next images will show the supports I have made underneath. It is aluminium, and gives me about one cm of support on each side of what is now the hatch. On top of these, I have placed a weather strip, which will have to be modified a little bit in order to fit well.
The longer aluminium bars are fastened by four screws, and the two smaller ones with two. In addition, all four bars have been rubbed with sandpaper, and glued with araldite.
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_2683.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_2683.jpg)
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_2680.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_2680.jpg)
This last image also shows one of what is to become the torpedo tubes.
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In addition to the progress under deck, my contractor for the 40 mm gun has been working hard this Christmas. Here's what he has come up with these last weeks:
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_3395.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_3395.jpg) (http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_3401.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_3401.jpg) (http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_3407.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_3407.jpg)
I must emphasize that I am not the person building this gun. This is a build from the same person who paints wristwatches on 1:87-scale people, and brass buttons on their jackets. I'm glad he agreed to build the gun for me. And no, it is not quite finished yet ok2
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The last thing I did before the holidays ended, was fastening the deck to the hull, and sealing the gap with silicone. I let it harden for a week before touching it at all, and it seems the silicone holds rather well. Perhaps it'll crack when I run the boat: after all, there are some vibration in the hull. The silicone is supposed to withstand changes in gaps up to 25 %, but: changes combined with vibrations. I wonder.
For the time being all open water apart from the sea is covered with ice and snow. It's beautiful, so I'm not complaining. Bad conditions for a test-run of model boats, though.
(http://th06.deviantart.net/fs71/300W/i/2009/357/e/1/Winter_wonderland_V_by_SinWin.jpg) (http://sinwin.deviantart.com/art/Winter-wonderland-V-147785038)
Not much open water on the little pond near our house.
Over to the boat:
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_2718.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_2718.jpg) (http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_2721.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_2721.jpg)
And yes: the silicone is black. It was the only thing they had in the shop I visited. Bad. Perhaps I'll try and paint over it, but I'm not sure that's a good idea.
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A long time since my last update here!
These past months I have mainly worked, studied and worked - though, alas, not on the boat in question.
However, some small improvements, or shall we say progress, has been made.
As mentioned earlier, I have sealed the gap between the deck and hull with silicone. I have not had the chance to test how good, or bad, this would work before now, simply because all small ponds have been covered with ice! When the ice finally melted, it rained - but a week ago, the weather was fair, and I charged my batteries, and went to the nearest pond to test the boat. Having fitted the batteries, turned on the transmitter and the receivers, I lifted the boat into the water - and just as I did that, I heard the sound of the transmitter telling me it had run out of battery. Argh!
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_3399.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_3399.jpg)
Oh, well, at least the boat still floats...
Yesterday, I tried once again. It rained, but I HAD to test. This time, I made sure I had charged both the lead acid batteries AND the transmitter batteries, before taking the boat down to the pond - and guess what, it worked! I ran the boat for half a minute on near-full power, and then sailed in to shore to chech if there had been any ingress of water. Before sealing with silicone, it would have been lots of water in the boat, but now it was perfectly dry! Success! No use for the pump I installed.
I then proceeded to sail the boat out on the water, but after a few seconds, only one engine would run - and only backwards, at a very, very slow speed. I finally got the boat inshore, and found that the 30 A fuse on the starboard engine (I have mounted a fuse between the motor and the speed controller) had blown. 30 A! I mounted a new fuse, but after a few seconds, this blew as well. I mounted yet another fuse, but after a few seconds, not the fuse, but apparently the speed controller blew! It now refuses to drive the engine anything but backwards.
What a blow: after all, it worked perfectly well before (just look at the videos I have posted), so what on earth has happened now?! I suspect that the starboard engine has a short somewhere - that might explain my earlier trouble with the first set of speed controllers (?). One other thing that I came to think of, is that my engines is held in place with steel bars which is connected to each other: this means that the caps of the engines are connected to each other, electrically speaking: however, I have seen many model boats where this is the case, so should this really be a problem?
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_1646.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_1646.jpg)
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After much effort, I have mounted a new speed controller to replace the one that melted on the starboard side.
Also, I spoke with the dealer, and he asked if I had cut the power supplied from the battery eliminator circuit from one of the speed controllers, so that only one controller supplied the receiver with power. From what I understood, he meant that if two speed controllers supplied the receiver with power, this could be the source of the problem. I really can't understand why, but did what he said: I cut the red cable running from one of the controllers to the receiver.
Having done all that, I went for a test run. 25 A fuses were mounted between the speed controllers and the engines: and guess what, the starboard fuse blew, AGAIN! And again, the port engine stopped working properly when the fuse for the other engine blew: the port engine would just run backwards, at a very limited speed.
A new speed controller obviously did not help, and cutting the BEC-power supply from one of the controllers did not help either.
Now I really wonder what is wrong!
Could it be something wrong with the engine itself? After all, it is just the starboard engine that, when under load (i.e. with the propeller under water), blows the fuse.
Below is a sketch of my electronics layout - I can't see that I've made any errors here?
(http://i599.photobucket.com/albums/tt73/sinwin/th_file.png) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=file.png)
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Do you have access to an ammeter to check the current draw of the motors.
Mechanical misalignment or a tight bearing can put excess load on the motor.
What voltage are you running her on?
Bob
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I did check the current at each motor before I fitted the deck, and when they were attached to the shafts and spinning the propellers (out of the water), they were well within what was written in their specs. Can't remember exactly how much, though. However, now that you mention it, a good ide might be to test this again, and see if there is a difference between the starboard and the port side engine.
Spinning the propeller and shafts when they are connected to the engines, I can't feel any heavy load, and no significant difference between the port and starboard side. In addition, I think 30 A is a ridiculous amount of current for one engine to draw - they should draw no more than 18 according to their specs.
The batteries fitted are 12 volts.
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hi ya there Sin Win
I noticed on your sketch that you have your 2 batteries connected together. Now, some speed controllers do not like a shared voltage between 2 batteries or a single battery. This is due to a curcuit which is built into them which creates a form of negative loop. In other words, one speed controller can supply the other one and also it interacts with it, causing the electrics inside it to short. Try running one speed controller off one battery. See what the amperage draw is. This may be the problem.
aye
john e
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Is that so? I never knew! I will have to test that as soon as possible. Thanks a lot!
I really hope that is the problem, so that I can go on with more interesting tasks than cheching the electronics over and over again for months!
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In order to test the engines and electronics, I need the propellers to run in water. The nearest pond is not so far away, but it is both slippery slopes and a highly trafficated road to cross before you get there, so to walk back and forth just for a little test is not that fun when everything works for just two seconds...
Well - we have a large garden here, so a small part of it has now been converted to a small pool to test model boats. I just built it from some old plaking we have, and will fit some plastic etc. inside it tomorrow to keep the water in, before i can go on with the testing.
(http://i599.photobucket.com/albums/tt73/sinwin/KNM%20Knurr/th_IMG_8854_s.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/KNM%20Knurr/?action=view¤t=IMG_8854_s.jpg)
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I may have found a solution! Or, perhaps, a workaround.
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_8872_s.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_8872_s.jpg)
Having fitted the pool with plastic and filled it with water, I ran the engines for a long time today, in order to find out what is going wrong. After having blown several fuses, I gave up - but looked briefly through the manual for the Graupner MX 12 transmitter that I use. There I found something called servo travel (I think), which basically gives an adjustable travel range of servos from 0-150 %. I set this to 80 % for both engines, and tried again: the 25 A fuses did not blow, and I was able to run for a long time without any blown fuses.
Success! At least I hope so.
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_8871.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_8871.jpg)
A few blown fuses from the testing...
The rest of the day was spent on painting details, and working on the mechanics for the turnable 40 mm gun.
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_8879_s.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_8879_s.jpg)
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_8879_s.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_8879_s.jpg)
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I had to go to work yesterday (I'm currently on a holiday, but a crisis emerged), but it was all right, as I then had access to a laser engraver/cutter. With that, I cut out the supports for the torpedo tubes. I'm afraid they're not 100 % accurate, but based on blurry and small photos and the single drawing I have, it was the best I could manage.
(http://i599.photobucket.com/albums/tt73/sinwin/KNM%20Knurr/th_IMG_8884_s.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/KNM%20Knurr/?action=view¤t=IMG_8884_s.jpg)
4 mm acrylic parts glued together.
(http://i599.photobucket.com/albums/tt73/sinwin/KNM%20Knurr/th_IMG_8885_s.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/KNM%20Knurr/?action=view¤t=IMG_8885_s.jpg)
.. and with the torpedo tube fitted.
And now, the whole boat looks like this, with the superstructure and 40 mm loosely fitted:
(http://i599.photobucket.com/albums/tt73/sinwin/KNM%20Knurr/th_IMG_8888_s.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/KNM%20Knurr/?action=view¤t=IMG_8888_s.jpg)
(http://i599.photobucket.com/albums/tt73/sinwin/KNM%20Knurr/th_IMG_8890_s.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/KNM%20Knurr/?action=view¤t=IMG_8890_s.jpg)
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Hi sinwin, This site contains a lot of detail/photographs of American PTF 'Nasty Class' survivors which might be useful, although torpedo tubes were'nt fitted. :-)
. http://www.ptfnasty.com/
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Thank you! I've glanced over the site, and it's gallery, but found few pictures of the torpedo tubes, since, as you say, they weren't fitted to the american models.
I have painted the torpedo tubes grey, but I'm not entirely sure that is correct. From the few colour pictures I have found, they appear grey, but might also be green - I've also seen both variants on model boats.
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Hi Sinwin, The Tjeld's torpedo tubes may be WW2 surplus from the Allies. Can you post best original photo? (They are unlikely to be Soviet %). ) :}
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The Tjeld class used 533 mm ex german G7a T1 torpedoes. I guess a lot of torpedoes were left in Norway after the German capitulation, and G7a torpedoes were used on many vessels, and at several coastal forts - up until 1999/2000. I don't know exactly when, but some modifications were made to some of the torpedoes to make them steerable via cable, these were called T1 mod 1.
They might have used some allied torpedoes as well, so long as they were 21''.
The pictures I have found showing the torpedo tubes are these:
http://arkitekturnytt.no/uploaded_images/tjeld_MTB-747193.jpg
http://upload.wikimedia.org/wikipedia/commons/a/a0/Norwegian_MTB_Nasty.jpg
http://img377.imageshack.us/i/knmgeirhf7.jpg/
Not very much to go on, but I don't think I am very much off in my modelling - though it could certainly have been better.
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The electronics certainly works! I went for a test run today, not only in the small pool I constructed, but in the pond close to the house.
After blowing one fuse on the starboard engine, I adjusted the servo travel on the transmitter to 70 %, after which I was able to run the boat for 15-20 minutes without any trouble at all.
At last!
(http://i599.photobucket.com/albums/tt73/sinwin/KNM%20Knurr/th_IMG_9807_s.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/KNM%20Knurr/?action=view¤t=IMG_9807_s.jpg) (http://i599.photobucket.com/albums/tt73/sinwin/KNM%20Knurr/th_IMG_9809_s.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/KNM%20Knurr/?action=view¤t=IMG_9809_s.jpg) (http://i599.photobucket.com/albums/tt73/sinwin/KNM%20Knurr/th_IMG_9847_s.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/KNM%20Knurr/?action=view¤t=IMG_9847_s.jpg)
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Hi sindre, It might be worth laying both batteries down on their sides to help lower the boats's c of g (centre of gravity). This may improve stability/reduce roll, especially in fast turns. Have you tried running the hull with the batteries in tandem (one behind the other).These heavy batteries can be mounted on 'velcro' or thin rubber mat to prevent slipping during running trials to trim for the boat. Although this is a big hull with a large 'wet area', it's worth moving these heavy batteries around/experiment to find best placement. :-)
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Hi! Thanks for the tip. I have experimented quite a lot with the placement of the batteries, but never in tandem. However, I feel the boat is much more stable now, after removing one of the originally three batteries, and she makes a turn rather well, although some speed is lost (which is quite normal, though). Of course, the overall top speed is greatly reduced when I have to reduce the power given to the engines by 20 %, but as that seems to be the only thing that works, I guess I shall have to live with it.
I think I'll have to glue all the superstructure and deck details in place before I can experiment more with the placement of the batteries - but I will sure look into it!
Thanks a lot for your comment, though!
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Hello SinWin
Maybe these pictures can be of some help. They where taken by a clubmember whos has planned to build the same model but has not statred yet. I used them to build similar torpedotubes for the Norwegian Elco class MTB's
HelgeBe
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Wow, that is fantastic! These are by far the best photos I've seen of the Tjeld class, thank you so very much! Now that I'm going to make the details on the deck etc, this is a great help! It also, at last, allows me to see which parts should be which colour!
Again, thank you - this is a really great help!
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I've received even more photos of the Tjeld class, and now I see several details that I've either missed or modelled wrongly. There is still a lot of deck fittings to model, though, so I guess it will look better when I make those.
Anyway, I have now fitted the superstructure, torpedo tubes and fitted a servo to turn the 40 mm gun. I have also mounted two antennas on the side of the superstructure.
(http://i599.photobucket.com/albums/tt73/sinwin/KNM%20Knurr/th_IMG_9435_s.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/KNM%20Knurr/?action=view¤t=IMG_9435_s.jpg) (http://i599.photobucket.com/albums/tt73/sinwin/KNM%20Knurr/th_IMG_9437_s.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/KNM%20Knurr/?action=view¤t=IMG_9437_s.jpg) (http://i599.photobucket.com/albums/tt73/sinwin/KNM%20Knurr/th_IMG_9440.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/KNM%20Knurr/?action=view¤t=IMG_9440.jpg)(http://i599.photobucket.com/albums/tt73/sinwin/KNM%20Knurr/th_IMG_9445_s.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/KNM%20Knurr/?action=view¤t=IMG_9445_s.jpg)
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Really, this is not fun anymore! I went for a test drive yesterday, and after a few minutes, the port speed controller failed, and now only allows the engine to run backwards. This is the exact same fault as I had with the original speed controllers, and a problem that I had hoped was solved. The fuse (25 A) did not burst. What on earth could be wrong?
Argh. I am sick and tired of buying new speed controllers, tweaking and fixing the propultion...
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1. What speed controller(s) were you using?
2. What size motor?
3. What size prop?
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First of all, editing my own post: fixing the propulsion*
And then: thanks for your reply. To answer your questions:
1. I'm using two speed controllers, "Graupner Profi 40 7,2-12V BEC". Each one drives one engine, and now draws current from one battery each. I have also cut the positive wire from one of the controllers to the receiver, to eliminate the risk of the two BECs interfering with each other.
2. The engines are two Graupner Speed 700 Turbo C 9,6V. They are mounted as shown in some pictures at the first page of this thread. As shown, the caps of the motors are in connection with each other, electrically speaking, but should that be a problem?
3. The propellers are two Raboesch "C"-type propellers, 45 mm in diameter.
On each positive wire leading from the speed controllers to the engines, there are one 25 A fuse. Because these fuses constantly burst, I have set the "servo travel" function on my transmitter to 70 % for both channels driving the speed controllers/engines. This worked fine a few weeks ago, when I ran the boat for two hours. The instability puzzles me.
Now that it seems I'll have to change a speed controller again, I might as well buy some completely new ones of another kind or brand, but I don't know if that will help (ref. the fact that I've already changed from one kind to another). I have also bought a brand new receiver, and installed it, in case there was something wrong with it - but to no avail.
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With this kind of spec. and they didn't blow the 25Amp fuses, I would say you have a very good case of getting your money back!
Graupner SPEED PROFI 40R BEC:
Overheating guard Specification
Operating voltage: 7.2 ... 12 V Cell count: 6 ... 10 NiCd, NiMH
Peak current: 200 A Cont. current, forward: 40 A
Pulse frequency: 1 kHz BEC: 5 V / 1 A
BEC current, peak: 1.5 A
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Try connecting an ammeter into the motor side of the circuit and then run the boat up to full power while in your test tank (This can make you very wet, so cover the electrics).
Just by looking at your equipment specification I think with those motors and large props you are probably pulling a lot of current under load. It may not immediately damage the controller, but fuses will be stressed and fail after a short period if you keep loading the controller with high loads, it could also fail.
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That is my thought as well! However, since this happens over and over again (this is the fourth speed controller I (or something else) break) with different speed controllers (first two Graupner Navy V30R, then one profi, and now the second profi) I am really wondering where the problem really is!
In addition, before I adjusted the servo travel function, I constantly blew both 25 and 30 A fuses when travelling at no more than two thirds speed.
And, for the record, I am using lead acid batteries - would that be a problem? They are 12 V, 7,2 Ah.
I would love to be able to measure the correct amount of current drawn by the motors, but I have no measuring equipment that is rated for more than about 10 A.
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The C type propellors will put quite a strain on the motors when run at great speed, I have never tried them on an MTB before, but have used them on a destroyer and they were very current hungry on that.
I think it maybe worth your while investing in a meter that can measure a higher current or look at different prop configurations.
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So I can imagine. The thing is that I had just the same problem with the type A-propellers, which I had installed before the C-type. Those propellers pushed the boat forwards all right, but much of the energy was used up in cavitation and nothing else. However, the fuses blew at higher speeds and I destroyed the first set of speed controllers with the A-type propellers.
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_0524.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_0524.jpg)
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SinWin
You should really invest in Wattmeter or something similar to check how many Amps you are pulling, relying on the fuse blowing is very hit and miss. I few years ago I invested in Wattmeter and it has repaid itself many times over in not blowing up motors, batteries and controllers as I know how much current I'm putting through the system. Giant Cod and many other place sell cheap Wattmeters like this one http://www.giantcod.co.uk/neodynm-multif-watt-meter-p-403851.html (http://www.giantcod.co.uk/neodynm-multif-watt-meter-p-403851.html)
Another thought is are you sure that your lead acids are capeable of providing enough power without stressing them? You might want to try NiMhi or Lipo as they can supply much more power.
Your boat looks very impressive, keep up the hard work :-))
Phil.
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Thank you so much!
That looks like a neat little instrument, and not all that expensive either. Perhaps I'll give it a go. After all, I have wanted something like that for some time.
However, even if my engines draw 20 amps or slightly more than that, I can't understand why the speed controllers should fail in the way they do. Every single one of them, that has been broken, has failed in the same way - they just quit to give the engine current forwards. If the engine should draw more than 25 A, the fuse would blow: both the engine and the speed controllers should be able to handle that amount of current.
Perhaps my setup is all wrong, but I am really not able to tell what is wrong. I mean: it worked for several hours a week ago, and then, yesterday, it just quit after two minutes on the water.
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I'm currently looking for new speed controllers - is there anything you out there would recommend? I am beginning to wonder if I should just cut out the luxury of controlling each engine separately, and just use one channel and one speed controller for it. Trouble is, as the engines draw so much power, I guess it will be difficult to find a speed controller that can handle the amount of current?
Should I buy some different style propellers? 4 blades? 5 blades? 2? Different pitch?
I also note that my receiver is placed rather close to the engines - this could be a problem, but I can't se why it should make the controllers fail?
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Hi SinWin contact Dave at ACTion Electronics he will help you out.
www.action-electronics.co.uk
He has designed many purpose made systems for boats.
He has just supplied Martin du in Australia with all the electrics for his very complicated 1:16 Brave Borderer.
http://www.modelboatmayhem.co.uk/forum/index.php?topic=9865.msg250599#msg250599
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Thanks for the tip. If he is willing to help me even without me nessecarily needing to buy something from him, I'll be sure to send him an email!
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SinWin
Before you buy any new speed controllers you still need to have an idea of how much current you are pulling, then you can order a ESC of the correct rating.
I have heard a lot of good reports of ACTion electronics but I have no personal experience of them. I do however own a couple of Mtoroniks controllers and are excellent brushed controllers. I had a problem with on of the controllers and it was probably my own fault, the controller was replaced promptly by Mtroniks, no questions asked.
Phil.
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I have now ordered the wattmeter linked above. Looking forward to receiving it! I have also sent an email to action electronics, perhaps Dave is able to help me out.
It is strange, though, that four ESCs should fail from too much current (I can't se why else it should fail in the way they did?), even when I have fuses installed, and fuses rated well below the maximum current for the ESCs?
Well, when the instrument arrives, we will find out how many watts the motors are consuming. Thank you all for your suggestions!
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SinWin ....some types of fuses are slow delay. >>:-(....& designed for robust applications...it is possible that a current spike could pass throught the fuse & destroy the electronic component prior to the fuse blowing ......Derek
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Oh, that is true. I did not think of that, stupid me. I have just bought some fuses made for cars, and I have no idea if they are slow or fast fuses. Most likely they are slow, if we are to judge by the amount of destroyed ESCs!
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Sinwin...I have near ZERO electrical knowledge {-) %% ....however even a new digital multimeter may not register a high amplidude ...short duration [milli/micro second] current spike...........
The popular reference here on Mayhem is to talk with FLJ..........I have ACTion components from the previous owner..... O0 ....& can only speak as a very satisfied customer........Derek
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I have had an E-Mail about this thread (which I confess I haven't been following) and I've replied to SinWin with my suggestions. Let's hope he can now sort it.
BTW it doesn't involve a wholesale refit with our stuff; that would just be gratuitious, wouldn't it? 8)
FLJ
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I guess you can't follow every thread =)
However, to sum up the email i received, FLJ concludes that my model is too heavy, the lead acid batteries unsuited for the task, and the propellers perhaps a little too big. Oh, and, that BEC is not the best thing in the world. I am inclined to agree with this (though, on the BEC-think I have nothing to say). As I have noted before, my only model previously has been a tug (Smit Nederland), where I would say lead acid batteries works like a charm, and the ESC did not fail from too much current, but because of my clumsy installation which allowed for short circuits. I blew four ESCs in that model, before I found out what the problem was; in other words, ESCs and me does not go very well together!
Based on FLJs recommendations I will buy new batteries (two large NiMH-battery packs), a receiver battery, and I still need another ESC. It means, though, that I can continue to use my engines, and now I also know, thanks to FLJ, that having the engine cases connected to each other in the way I have, is no problem.
I must thank you for showing me Action Electronics, and a special thanks to FLJ for his quick and very useful response!
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I've now ordered the two battery packs, 12 V 5Ah, and a separate receiver battery pack. Also, the wattmeter is on its way.
Now I'm looking forward to a model that works!
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SinWin
If you fit a separate receiver pack you will remember not to power the receiver by a BEC supply as well won't you :-))
Phil.
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Hehe, I will! Thanks for the reminder. I guess some red wires will suffer!
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Still waiting for all the new gear to arrive. I hope it arrives before Sunday!
I've also bought some lead, as I guess the 5 kg reduction in weight will make the boat ride too high in the water, and I want some weight in the middle, as low as possible. Not too much, though.
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Still waiting for all the new gear to arrive. I hope it arrives before Sunday!
That's now very much in the hands of Norwegian Customs and Royal Mail. We waved goodbye to our little contribution to the cause on Tuesday.
As I said, you should concentrate more on getting the model to sit level in the water than ballasting it down to the waterline. I think you will be very surprised at the difference in performance.
FLJ
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Of course! I ment no offense, my point was not to complain in any way, I am just very eager to get all the things I've ordered, put it together and see that it works!
And yes - I want do do like you said, make it sit level on the water, but not much more. I have not ordered any new propellers yet, I hope to be able to maintain the 45 mm, but perhaps they should be smaller.
I watched an old Norwegian movie the other day, where the Tjeld class plays a part. Some of the scenes shows the boats at full speed, and the bow lifts noticably more than I've been able to replicate in my model. I wonder, though, how stable it will be in a turn when 5 kg of weight disappears!
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Of course! I ment no offense, my point was not to complain in any way,
None taken, Sindre. It's like waiting for Christmas morning, isn't it ok2
FLJ
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Glad to hear it.
And yes, it is a little bit like waiting for Christmas! After all the problems I've encountered with something that should be simple, I'm looking forward to a fully functional vessel.
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I got my batteries today! And oh my, they are light! At least compared to the two lead acid batteries I have used. Now I just have to buy some male plugs so I can charge them.
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Just checked the mailbox, and my fuse holder from Action Electronics are here as well! A neat little installation.
I was going to charge my two battery packs the other day, but unfortunately, my NiMH-charger can only charge 8 cells, and not 12. This means I have to buy a new charger as well. Bah.
Now I need a new ESC, a new charger, and some 12 V fans as well, to cool the ESCs, which I will place differently than they are today. Oh, well. Have to wait until 15 September to buy any more stuff, though; payday.
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Do you not have an old computer?
They're a good source of fans.
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I don't, but I work in a place where used computer fans are all over the place, although not so many 40x40-size, which I would prefer - and my brother is an inexhaustible source of old computer components. If all fails, I would have to buy some.
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Hi Sindre, Enjoy:
http://www.britishpathe.com/results.php?search=motor+torpedo+boat&o=20 :-)
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He won't be the only one who enjoys it. Great bit of film for somebody who is building one of these.
They diont make newsreels like this anymore, mores the pity.
Geoff
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It's a good one Geoff. :-)
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I must say! That was most interesting. Thank you so much for sharing!
There has not been very much progress in the last weeks. I'm currently working on two film projects in addition to a miniature ROV.
However, I managed to change the batteries in the MTB the other day. It rides much higher in the water, and there is something odd with the balance: for some reason it leans to the starboard, but I think I will just counterbalance it, and leave it as it is, and see what happens.
As one can see, there is a "slight" difference in size between the batteries I had, and the ones I have now!
(http://i599.photobucket.com/albums/tt73/sinwin/KNM%20Knurr/th_IMG_9613_s.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/KNM%20Knurr/?action=view¤t=IMG_9613_s.jpg)
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Things are happening, although slowly.
Since one of the ESCs decided to blow, I have to buy a new one. Since they are rather expensive from my local dealer, I had to wait until I could afford yet another one. I searched ebay the other day, however, and found the exact same ESC from a German dealer at under half the price. I bought that, and am currently waiting for it to ship.
Apart from that, I used my little pool and balanced the boat with the new batteries. It will need half a kg of lead on one side to be properly balanced, but there will be some weight saving after all!
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I've been thinking a long time about having exhaust fumes coming from the real exhaust ports, those that were above the water, anyway. However, I don't know how much smoke came from these engines? And if, how visible was it, do you think?
I came across this "high output smoker" made for RC tanks the other day, and wondered about installing it in the MTB. http://www.rccommand.com/Whats_new.php
It is possible to run it on 12 V, and it will last for one hour, they say.
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Hi Sindre, the 2 stroke Deltics were definately 'smokers' on startup. Twin Deltics were used to power several of our diesel/electric locomotives and they were very big smokers on first startup when the engines were cold, especially during winter:
http://www.youtube.com/watch?v=c4sQqtaJKWw&feature=related
http://www.youtube.com/watch?v=pv_cGG56QA4&feature=related
http://www.youtube.com/watch?v=CG91fYHcm-k&NR=1
The large locomotives and Nasty/Tjeld both used twin 'blown' versions of the Deltic - enjoy their soundtrack on the loco clips above. Once they were warmed up the whistle and roar of the twin Napiers on full power was unique/dramatic and less smoky. %)
The smaller British Dark class mtb/mgb also used twin Deltics but they were not 'blown', however, black soot deposits on their rear hull sides was definately a problem, so the rear half of the hull was painted black to make the soot staining from their side mounted exhausts less noticeable.
Your Tjeld would demonstrate 'clagging' in Norway and sound amazing 'thrashing' up a fiord at 50 knots. :}
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Woah, that is some serious smoke! (And sounds, for that matter!) But if they were not "smokers" during normal operation, I guess a smoke generator would be out of place?
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In the colder climate of Norway they would smoke continuously as the exhaust condensed/chilled......................... order a smoke unit and add extra style to a very loud sound unit for a really authentic Deltic duet. The soot is excess fuel which is partially combusted/expelled in certain running conditions, and the white smoke is unburnt fuel during cold startup and condensation while running at normal temperature. The smoke is of coarse lost/mixed in the spray and left in the wake as the boat's speed increases. :}
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Hmm.. It is becoming more and more tempting to buy one! If it can be argued that they really did produce smoke also while running, I guess it would be pretty cool to have exhaust fumes coming from the real exhaust ports! A sound unit could be cool, too, I agree, but in some ways I think the sound (not that it's much) of the electric motors is cool enough :-)
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Your motors are a personal favourite of mine and I'm wondering if one can be persuaded or tweaked to whistle and roar like a blown Deltic............. Hmmmm. (The inbuilt cooling fan on the rear of the armature may have potential %). )
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He he he :-)
I can see why you like them, though - pure, raw power. But, may I ask what the difference between blown and not blown is when speaking of the Deltic?
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Deltics were originally intended for marine use and designed for extended or continuous high speed running. The turbo charged ( blown ) version was capable of 3700 bhp. Even higher outputs were possible but the engine was governed to 1800 rpm in order to extend it's service life and reliability.
The rail locomotive version was unblown (without a turbo charger) and de-rated to 1650 for use in rail locomotives, singly or in pairs to generate electricity for their electric motor drivetrain.
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Aha, I see! Thanks a lot for the info! I think I'll order one of those smoke generators after all. I really can't resist! (Who can?) Just have to wait until the 12th, which is payday!
I'm having great trouble with one of the channels on my sender, the left hand on/off-switch on top of the sender unit won't toggle anything. I tried the channel with different equipment attached, and I have changed the receiver (yes, the entire unit), but still no sign of functionality. I have checked the programming of the unit as well. I guess it's down to hardware failure, then?
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Hi Sindre, which TX - make/model are you enjoying?
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It is a Graupner MX-12. I'm thinking I could use one of the switches for the smoke generator, if I buy it.
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I received the new speed controller a few days ago, and yesterday I got the chance to change it. What I did not get a chance to test was the boat on the water, as I used the daylight for trying to get my helicopter in the air. (It did, eventually, before I crashed it into a hedge after a few seconds in the air. It was either that or some electric cables....)
Anyway. Having fiddled for a long time to get the old controller OUT, I fiddled for some time to get the new controller IN. I have not yet fitted the fuse holders I got from Action RC, but I will!
As one can see there is limited space for me trying to get hold of the controllers in their position.
(http://i599.photobucket.com/albums/tt73/sinwin/KNM%20Knurr/th_IMG_0248_s.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/KNM%20Knurr/?action=view¤t=IMG_0248_s.jpg)
But I managed it eventually, and mounted the new controller differently, in a more convenient spot for maintenance, if not for cooling.
(http://i599.photobucket.com/albums/tt73/sinwin/KNM%20Knurr/th_IMG_0251_s.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/KNM%20Knurr/?action=view¤t=IMG_0251_s.jpg)
The new speed controller is of the same type as the old one, but appears to be of some new and more fancy model: it has auto set up, which is a feature I really like.
Perhaps I'll get a chance to test the boat on Saturday, we'll see.
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Hi SirWin,
I just stumbled upon your build thread and I have a few remarks.
Before I say something, please understand I'm only trying to help, not putting you down, but you've made a number of newbie mistakes...
1) The propshaft angle is much too steep, this is one of the reasons you fried a number of ESC's last year, a MTB is basically a fast electric speedboat, or at least it can be, when it is set-up right.
(In the fast electric department I have a lot of experience, as I'm running my boats in competition for the better part of a decade now and my fast scale boats benefit from that experience.)
The propshaft angle needs to be as shallow as possible, the way your's are set-up, a lot of the thrust is angled down, lifting the rear end of the boat.
I watched your first video and I was amazed how 'wet' it ran, with the bow pressed down into the water pushing big masses of water to both sides. (when I saw the pictures of the propshaft, it was obvious why this happened.)
This may look impressive, but puts a heavy strain on the motors; you were 'lucky' to do the first runs on Lead acid batteries, which cannot deliver the current that the motors draw under these conditions.
(I've been running 700 motors on 12 cells NiMH in the past and they do draw up to 40A getting out of the hole; once the boat is on the plane, the current drops to an average of 20-25A)
I assume you have two Graupner Best.-Nr. 3308 motors; if you look at the specs, the current the motor draws when blocked to a standstill is 75A! So it's no wonder your ESC fried under the constant load of those big props trying to lift up the boat.
Basically you're overloading the drive train big time, and when you're using a powersource that really can deliver the current (like Lipo's), the motors will fry.
When you're 'abusing' the motors, like everyone does in fast electric boats, you need to watercool them, both can and brushtabs, or you'll be buying motors for ever...
To get the propshaft angle right, you'll need long (very long) propshafts, so the motors sit way forward in the hull allowing for a shallow propshaft angle.
2) The propshafts need to be supported, both outside the hull and inside, specially when using rubber couplers, the vibration can rip the propshaft right out of the hull if it's not properly supported.
3) The motors need to be mounted on a bulkhead, using the M4 threaded holes on the front of the motor.
This also gives you room for can cooling.
If you want to keep running large props, these motors are on the edge for such a large hull, two 800 motors would have been a better choice, as they don't have to work so hard and draw less current.
Watercooled (can- and brushtab cooling) they will just get handwarm.
I'm building a slightly smaller (110 cm) Italian MTB, which is going to be powered by a fanmotor from a car, made watercooled and slimmed down (it's a heavy motor), source: the scrapheap, costs next to nothing and has the torque to turn a big prop with very modest ampdraw.
I'll add some pictures of the things I mentioned, to give you an idea of how it can be done.
Regards, Jan.
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Pictures.
This is the boat I'm building, notice the propshaft angle.
(http://s3.postimage.org/2ca4owio4/M_A_S_JPEG.jpg) (http://postimage.org/image/2ca4owio4/)
For my model I will use an even longer shaft to get the angle even more shallow, as the water is not scaled down, the propangle has a big impacy on the running attitude.
More to come.
Regards, Jan.
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And more pictures:
Here's a motormount:
(http://s3.postimage.org/2ckigcy9w/Motorspant01.jpg) (http://postimage.org/image/2ckigcy9w/) (http://s3.postimage.org/2ckqq1oqs/Motorspant_02.jpg) (http://postimage.org/image/2ckqq1oqs/)
With a 700 motor flanged onto it:
(http://s3.postimage.org/2cl0n9rpg/Thick_Flash_motormount.jpg) (http://postimage.org/image/2cl0n9rpg/)
From left to right: Graupner 1700 Ultra, 800 motor, copier motor, fan motor.
(http://s3.postimage.org/2cliu6l50/PIC03442.jpg) (http://postimage.org/image/2cliu6l50/)
And the fan motor with the full jacket and brushcooling:
(http://s3.postimage.org/2clw2hd38/PIC04231.jpg) (http://postimage.org/image/2clw2hd38/) (http://s3.postimage.org/2clzdk22s/L_ftermotor_01.jpg) (http://postimage.org/image/2clzdk22s/)
A 700 motor with can and brushtab cooling:
(http://s3.postimage.org/2cme9e6is/Cooling_jacket_on_700_BB_1.jpg) (http://postimage.org/image/2cme9e6is/)
The long shaft for my M.A.S., the motor is going to be at bulkhead no.5:
(http://s3.postimage.org/2creiz0ck/Long_shaft.jpg) (http://postimage.org/image/2creiz0ck/)
Regards, Jan.
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Thanks a lot for all your pictures and hints! I take no offence from it, I'm glad for all the help I can get. I do sincerely hope that the lightened weight of the boat will do something good, though, for reading your suggestions I see a whole rebuild!
I guess I could change the shaft angle, although it would mean cutting out a large portion of the hull, because I've glued them rather extensively. When it comes to support for the shafts, they are supported on the outside, but not on the inside. Also, changing the motor mount would be quite a job. Oh dear! I see the mounts you show in the pictures are very elegant - I've never found things like that in the shops I've visited. Where do you get those?
As far as I can remember, I bought the longest shafts I could find in the shop, according to recommendations given by the people who sold me the hull. I might still have mounted them wrong, but this was as shallow angle as I thought I could go - but I guess you're right in that it could have been shallower.
But do you suggest even bigger motors? Wow. I would have thought a pair of 700s would do fine.
So, summing up you suggest:
- shallower angle on the shafts
- water cooled motors
And, perhaps:
- smaller propellers(?)
- larger motors
Again, thank you for your comments!
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Hi SirWin,
The motorflange propshaft are mainly used in raceboats, where alligning the motor and propshaft can be trickym due to space limitations.
Available here:
http://www.gundert.de/ka33.htm
Gundert also makes these on demand if what you need isn’t listed, such as a longer one, with a 4 mm shaft and multiple support bearing due to prevent the shaft from whipping.
If you have access to a lathe, or have a machineshop nearby, I have the drawings of such a coupling bell on my harddrive, the measurements can be adapted to your wishes, let me know if you want it.
You can make your own.
Removing a brass propshaft isn’t difficult, when you’ve used epoxy resin to glue it in.
Apply heat to the stuffing tube and the epoxy will get soft, allowing you to pull it out, or alter the angle.
With the latter, adding a bit of glassclotht and epoxy will seal the hull again.
I have a tutorial on my harddisk for the cancooling, with pictures, pm me your emailadress if you want it.
A pair of 700 should do the job in your boat, but you'll have little reserve in terms of thermal overhead due to the relative high current, this should improve once you have a better propshaft angle and fitting props for the motorsize.
Mind you, making the motors watercooled is intended to keep the windings and the magnets cool and should not be used as an excuse to overload the motor in terms of voltage and propsize, as they will burn up, regardless of the watercooling...
So, if the 700 motors turn out to be too small for the task, bigger motors are in order.
Regards, Jan.
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Hm, perhaps I can try and adjust the angle, if heat is the only thing that is needed. I could use the same motor mount that I have today, only modified: if I cut off a portion of the wooden beam, I could just use that to fasten some new motor mounts to it. That way the motors will run cooler as well (more air around them). Perhaps that would be sufficient both with regards to cooling and angle?
I do have access to a small 'workshop', the only thing I need to get hold of is the metal, and if so I guess I could make some simple mounts myself. I would think the main thing is to lift the motors so that they stand up from the "ground"?
I really hoped to avoid water cooling, because I'm afraid of leaks and such, but I don't know. Perhaps I'll have to do it.
When it comes to propellers, do you have any suggestions? I have two 45 mm propellers as of today, Raboesch type "C" (as can be seen to the left here (http://"http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_0524.jpg")) - they are perhaps a little too big?
In the same photo I guess you can see well enough that the angle of the shafts can be a lot shallower.
Again, thanks a lot for your replies!
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Hi Sinwin,
Making the angle more shallow will make a huge difference in how the boat will run, lowering the ampdraw.
I would make a new motormount in the form of a bulkhead where the motors can be bolted onto, leaving room for can- and brushtab cooling.
With the cooling in place, the motorcan should sit just clear of the bottom of the hull one millimeter will suffice, more will make the angle bigger.
Installing watercooling in- and outlets in a polyester hull is very easy and very waterproof, if done right.
All my fast boats have watercooled motors (and ESC if required), none of them leak.
On a 700 motor, driving a subsurface propellor, I have not gone bigger than 40 – 42mm, if the prop is high pitched.
With a low pitched prop the diameter can be 45-48 mm but not much bigger or the motor will start to draw a lot of current.
As it’s a fast boat I wouldn’t bother too much with scale props, you can mount them for when the boat is at display, for running the boat I prefer the more efficient two bladed props.
Graupner has a nice selection.
Low pitch serie:
http://www.graupner.de/de/products/1be70983-07b5-4873-80ae-f2ebea0d8f72/451.3/product.aspx
High pitch serie:
http://www.graupner.de/de/products/1be70983-07b5-4873-80ae-f2ebea0d8f72/455.5/product.aspx
Surface drive props 2318 serie:
http://www.graupner.de/de/products/1be70983-07b5-4873-80ae-f2ebea0d8f72/2318.40,5/product.aspx
The 2318.xx series are surface drive props with high pitch which actually perform really wel in a subsurface drive, but be aware of the fact that the blade surface it big and too big a diameter will fry your motor, ESC, battery, due to excessive ampdraw, so start small!
If you make the propshaft angle smaller, make sure a 45 mm will just clear the hull (1-1,5mm), you won’t use such a big prop in a high pitched version, so this amount of cleareance will do.
Regards, Jan.
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Hi Sindre, I do agree with pomplebled re. the need for much shallower angles on the prop shafts to improve efficiency and it would probably be well worth removing a suitable area of deck to allow the lowering and repositioning of your motors. I would buy a pair of alloy motor mounts to suit the turbo 700 motors and bolt them in position through the bottom of the hull but mounted on baseplates. It's worth remembering that prop thrust is linear and this hull is'nt a helicopter - planing requires only forward thrust. The bow will lift correctly as speed increases - true to the design of the hull. The present steep angled shafts have increased drag and obstruct water flow to the props. A much more horizontal alignment, using much longer shafts will reduce these problems and maximise thrust. I have used 45X props on these motors and cooling was not needed when running on 12 volts (twin 12v 7amp/hr sla's wired to deliver 14 amps).
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Smart! I'll have to get hold of a heat gun - will that be sufficient to make the epoxy weak and bendable?
The shafts I have now are 450 mm in length - would I really need even longer ones?
I think I'll start with removing the motors, cutting out the wooden beam they are resting on and then seeing how low I can mount the motors. Then I'll adjust the shafts accordingly.
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Hi SinWin,
An electric heat gun (for paint removal) will work fine.
Make sure to mainly heat the propshaft (stuffing tube) and not the surrounding hull, as the hull is much thinner than the glued joint and does require not a lot of heating up to deform.
I assume the hull is polyester, so once you deform it by heat the damage is irreversable, so keep an eye on it.
450 mm shaft is not a lot for the boat size, I have a 450 mm shaft in my 80 cm speedboat...
But a lot depends on the place where the shaft exits the hull and the hullshape in the aft section.
I would take out the woodblock completely and make a motormount out of 3 mm aluminum sheet.
I added a picture of what I mean;
The one on the left is a motormount that is shaped to fit into a single motor set-up, the one on the right is more universal and can be bolted into the boat on a bulkhead.
Notice the cooling slots for the motor, these are not to be blocked by the mount, as the fan inside the 700bb need to be able to draw air through the motor.
The motor should sit om the bottom with just a mm of space, no more.
The same goes for the prop, 2 mm cleareance of the hull is sufficient
Regards, Jan.
(http://s3.postimage.org/kjli2t38/Motor_mount.jpg) (http://postimage.org/image/kjli2t38/)
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Hi Sindre, I heat the propshaft tube with a mini/diy gas flame soldering torch. I always use this method to avoid/minimise heat damage to hull or interior spaces. You will be applying intense heat to a small area of the shaft tube OUTSIDE of the hull - much safer.
1. Disconnect/remove the motors/couplings and propellors.
2. Turn the hull on its side and get a friend to hold/support the hull firmly.
3. Firmly grip/clamp the propellor end of the shaft tube with pliers/molegrips (Leave shaft in.)
4. Apply heat to the shaft tube. (pointing flame in a direction away from the underside of the hull to avoid damaging it.) The heat will build up and transfer along the length of the tube and soften the epoxy jointing.
5. Gently/slowly....... twist/pull the shaft through/out of the hull using the pliers/grips. Apply heat carefully as needed until the shaft is out.
IMPORTANT: BEWARE of fumes - do this outside or in a very well ventilated area.
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Thanks a lot for all your help! I think I have an idea of how to do this now. I'll lend a heat gun from work, and try and get the shafts out. Perhaps I'll find some aluminium to make two motor mounts as well.
I looked over the instructions that were given alongside the hull, and I have actually followed them. I have bought the shafts that they specify, and mounted the motors like it says. Also, as far as I can see, I have mounted the shafts in the same angle as shown in several photographs! Ugh.
What I am really wondering is how to get that wooden beam out of there, though. It is a very small hole to fit a saw in, and I really don't want to remove the deck again.
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Hi Sindre, The angle of the props/shafts on the original boats was very steep and if you are happy with the performance of your boat then don't alter the shafts/motors alignment. Concentrate on your original plan ..... it's your build .... you are the boss. :-)
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Sindre,
That's the problem when an original drawing is converted for model use; the designer often hasn't got a clue on the effect of the propshaft angle on the not scaled down water.
On 'proper'(meaning practical) mopdel plans this has been take into account and changes have been made to the propshaft angle and sometimes even tt the underwater hull to improve the performance and handling of the model.
When this is done properly, the difference will not show immediately, unless you are very familiar with the 1:1 ship.
My Italian MTB originally has two motors, but as a single motor with a large prop is more efficient, I'm going with that, as it's going to be a model for running, rather that putting it on display.
Regards, Jan.
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Well, I can't say that I'm happy with the performance so far. Or - well - when it does work, it works well - but I can't live with the unreliability.
I might give it a try on the water, though, before adjusting the shafts. With 5 kgs missing it should draw less current? Perhaps I'll mount the wattmeter I bought and place a camera to record its readings on a little run, to see how many amps it does draw now.
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My pair of 700BB TURBO motors were running (often continuous at max power) with twin 30/40(burst) amp Mtronik speed controllers with a Futaba Skysport 6 (40mhz). I would now choose 40 amp min esc's.
Your video, posted earlier in the thread, shows the hull planing well and making a good speed and your new lighter,high capacity nimh packs should increase performance. Your hatch access in the deck may enlarge if you extend the opening forward to include the bridge (base area) and remount the bridge on an extended hatch. You could fit a raised 'combing' to locate the bridge at it's base and prevent spray from entering the hull. This larger opening in the deck could improve access for repairs/alterations.
I hope the test run shows that the electrical issues are solved........ I understand your frustration..... I've been there! %) :}
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With 5 kgs missing it should draw less current?
Hi Sindre,
Less weight means less work for the motors, so that's a 'yes', unfortunately a lighter hull will suffer more from the steep propangle shafts, meaning it will allow the motors to lift up the rear more easily, making the boat run very wet, which in turn causes the ampdraw to go up, as the hull will not get on the plane.
Now I'm not certain this particular type of MTB is supposed to plane out, but with shallow propshaft angles and the power you installed, it most likely will...
Regards, Jan.
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Finally the temperature has risen above freezing, and after months without any open water to test the boat with the new batteries installed, the day finally arrived.
After initially bringing the wrong receiver battery pack, and struggling with a servo cable that would not sit tight in its receiver socket, I got the boat on the water - and it ran beautifully!
Now, it has done that before, I admit, but this time I was able to run at full speed - or rather 80 % of full speed, due to me limiting the "servo travel" for the proper channels - for long periods of time. When I had the lead acid batteries fitted, I would most certainly not have been able to do that for more than a minute - by then some fuse would have blown, or an ESC.
I'll let these photos, taken by a very clever photographer accompanying me this day, speak for themselves:
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_4331_s.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_4331_s.jpg)
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_4288_s.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_4288_s.jpg)
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_4282_s.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_4282_s.jpg)
(http://i599.photobucket.com/albums/tt73/sinwin/th_IMG_4256_s.jpg) (http://s599.photobucket.com/albums/tt73/sinwin/?action=view¤t=IMG_4256_s.jpg)
When I took the boat out of the water afterwards, I was able to hold my fingers against the motor casings, without feeling any excessive heat. The ESCs were also just moderately warm. Before, the motors would be so warm I could smell burnt wood when I opened the hull, and the ESCs were so hot you could really feel the heat from them. I guess this shows that I'm really on to something - thanks to all the very kind people on this forum!
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Here is a short video as well of the test run, with some on board footage as well: http://www.youtube.com/watch?v=RFab0jQZMcU
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Some photos of the Nasty which is being buit. I am not sure that one is the same of Norwegian Tjeld class MTB.
An Pham
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Hi Sindre,
My appologies for the late response, I couldn't find this thread...
The pictures and the video clearly show the running attitude issues caused by the 'catastrofically' steep propshaft angle, ruining the handling , specially in the turns.
If you want to be amazed by your own boat running attitude and handling, change the propshaf angle to as shallow as possible.
Regards, Jan.
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That looks like a very impressive construction! Looks like a very detailed model.
I still haven't started on the operation of changing the shaft's angle. It seems like quite a task, and I must admit my motivation for removing the deck etc. is not very high. One day, however, I guess I'll do it.
For some reason the batteries I bought for the boat have died. I'll buy new ones, but that will have to wait a few months. I have also started building the forward 20 mm Oerlikon, but, alas, I haven't gotten very far yet.
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Complete model. This model is belong one of my friend from Norway.
An Pham