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Author Topic: Norwegian Tjeld class MTB  (Read 44057 times)

SinWin

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Norwegian Tjeld class MTB
« on: September 21, 2009, 08:29:30 PM »

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.


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longshanks

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Re: Norwegian Tjeld class MTB
« Reply #1 on: September 21, 2009, 09:24:03 PM »

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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SinWin

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Re: Norwegian Tjeld class MTB
« Reply #2 on: September 21, 2009, 10:07:26 PM »

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:



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:



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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SinWin

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Re: Norwegian Tjeld class MTB
« Reply #3 on: September 22, 2009, 08:37:08 AM »

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:

Original propeller:
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rsm

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Re: Norwegian Tjeld class MTB
« Reply #4 on: September 22, 2009, 08:50:27 AM »

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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SinWin

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Re: Norwegian Tjeld class MTB
« Reply #5 on: September 22, 2009, 08:54:34 AM »

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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rsm

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Re: Norwegian Tjeld class MTB
« Reply #6 on: September 22, 2009, 09:03:22 AM »

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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DickyD

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Re: Norwegian Tjeld class MTB
« Reply #7 on: September 22, 2009, 09:29:51 AM »

Deans Marine do a good selection of Raboesch props

http://www.deansmarine.co.uk/html/propellers.html
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SinWin

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Re: Norwegian Tjeld class MTB
« Reply #8 on: September 22, 2009, 09:33:21 AM »

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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rsm

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Re: Norwegian Tjeld class MTB
« Reply #9 on: September 22, 2009, 09:50:58 AM »

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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SinWin

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Re: Norwegian Tjeld class MTB
« Reply #10 on: September 22, 2009, 11:37:37 AM »

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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SinWin

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Re: Norwegian Tjeld class MTB
« Reply #11 on: September 22, 2009, 07:14:03 PM »

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.



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.



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.


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:

The batteries are fitted inside 3 mm plywood, glued into place and strengthened by pieces from the Meccano set.
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Tug-Kenny

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Re: Norwegian Tjeld class MTB
« Reply #12 on: September 22, 2009, 07:54:30 PM »


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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SinWin

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Re: Norwegian Tjeld class MTB
« Reply #13 on: September 22, 2009, 08:06:10 PM »

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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Tug-Kenny

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Re: Norwegian Tjeld class MTB
« Reply #14 on: September 22, 2009, 08:17:44 PM »


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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SinWin

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Re: Norwegian Tjeld class MTB
« Reply #15 on: September 22, 2009, 08:56:34 PM »

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:


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.

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Pale Horse

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Re: Norwegian Tjeld class MTB
« Reply #16 on: September 23, 2009, 09:05:42 AM »

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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SinWin

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Re: Norwegian Tjeld class MTB
« Reply #17 on: September 23, 2009, 10:11:37 AM »

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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derekwarner

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Re: Norwegian Tjeld class MTB
« Reply #18 on: September 23, 2009, 10:34:25 AM »

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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SinWin

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Re: Norwegian Tjeld class MTB
« Reply #19 on: September 23, 2009, 10:38:08 AM »

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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SinWin

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Re: Norwegian Tjeld class MTB
« Reply #20 on: September 23, 2009, 09:58:07 PM »

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.




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.

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:


And finally, the shield is mounted, being soldered on to the base of the gun:



I soldered it on from the bottom, thus hiding the "weld" as best I could.
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derekwarner

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Re: Norwegian Tjeld class MTB
« Reply #21 on: September 24, 2009, 07:54:32 AM »

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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SinWin

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Re: Norwegian Tjeld class MTB
« Reply #22 on: September 26, 2009, 08:45:10 PM »

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.


Red paint added to the bottom...



And green paint added to the hull.
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SinWin

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Re: Norwegian Tjeld class MTB
« Reply #23 on: September 27, 2009, 10:00:39 PM »

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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SinWin

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Re: Norwegian Tjeld class MTB
« Reply #24 on: September 30, 2009, 10:31:02 PM »

I also painted the superstructure:



When this was done, it was time for the frist test drive...
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