Model Boat Mayhem
The Shipyard ( Dry Dock ): Builds & Questions => Navy - Military - Battleships: => Topic started by: Steven.T on August 24, 2013, 04:19:50 pm
-
Hi All,
Joined up on here a few weeks ago, been lurking for a while whilst I dug the boat out that I started 6 years ago, that still isn't finished! Mainly due to my main hobby being Railways, especially garden railway stuff recently, the boat was left to gather dust.
Anyway, I finally found it in me to get the thing off the shelf and dusted off, which is a Model Slipway RTTL. It still needs painting and the running gear installing, but everything else is pretty much there! Thinking of putting 2.4ghz in rather than 40 mhz which I had originally planned, seeing as though I use 2.4ghz for the railway stuff!
Some pictures of the boat so far:
(http://i602.photobucket.com/albums/tt102/ste234/P8240287.jpg) (http://s602.photobucket.com/user/ste234/media/P8240287.jpg.html)
(http://i602.photobucket.com/albums/tt102/ste234/P8240286.jpg) (http://s602.photobucket.com/user/ste234/media/P8240286.jpg.html)
Cheers,
Steven
-
Welcome to the forum, nice bunch on here and some great advice if you ever need any.
Very nice, will look rather good when all finished...reminds me I have umpteen projects to do...static, dioramas and a large RC boat that seems to taking for ever... :((
Si:)
-
Looks good so far!
Dust it down get it painted and out on patrol!
-
Cheers guys!
Still unsure how I'm going to paint it, thinking of spraying the hull and superstructure, and hand painting the deck. I've got a nut brown paint that I think will go well on the deck!
Steven
-
Does any one know if these are still available? I fear their not.Bob
-
They aren't listed on the model slipway site anymore Bob, don't know how long they have been off for, was a while since I bought mine!
-
Many thanks Steve.Have found something here WWW.Kitshackmodels.com (http://www.Kitshackmodels.com) that might be the bizzo...wood.Cheers.Bob.
-
Hi Bob,
I found this one as listed in stock:
http://www.agesofsail.com/ecommerce/model-slipways-ship-kits/model-slipway-vosper-rttl-rc-ready.html
Which model did you find on the WWW.Kitshackmodels.com (http://www.Kitshackmodels.com) site, if I may ask?
Regards, Jan.
-
Blimey thats expensive! I only paid something like £40 for mine... they are asking for £102? Must be because it's been imported to America?
-
Hi Pomp,these RTTL's don't appear on the Kitshack Web site from what i can see.I typed in Vosper RTTL Kitshack on Google and just down a bit you see it.There seems to be three different sizes,28,56 and 68 inches plus a 46 inch Crash Tender.They may be new?Hope this is of some help.Bob.
-
Hi Guys,
I think I've done enough work on my RTTL now to justify starting a topic about it.
For those who haven't seen my intro post, It's the Model Slipway Kit, I started this 6 years ago, and it got waylaid, but I've been cracking on with it over the weekend!
This was the boat the other day:
(http://i602.photobucket.com/albums/tt102/ste234/P8240286.jpg) (http://s602.photobucket.com/user/ste234/media/P8240286.jpg.html)
Which swiftly had a coat of primer and then red oxide primer on the hull:
(http://i602.photobucket.com/albums/tt102/ste234/IMAG1789.jpg) (http://s602.photobucket.com/user/ste234/media/IMAG1789.jpg.html)
The superstructure has been painted, still need to add details like ladders and handrails:
(http://i602.photobucket.com/albums/tt102/ste234/IMAG1790.jpg) (http://s602.photobucket.com/user/ste234/media/IMAG1790.jpg.html)
More later hopefully when the hull has dried...
Cheers,
Steven
-
Well, the red oxide on the hull has dried, the finish seems ok, probably not up to the standards of most of you guys but it will do me!
Still need to paint the black on the hull, and try and get the waterline straight. Any tips on how to do this when using masking tape, the tape always just curves off away from the line >>:-(
(http://i602.photobucket.com/albums/tt102/ste234/IMAG1794.jpg) (http://s602.photobucket.com/user/ste234/media/IMAG1794.jpg.html)
(http://i602.photobucket.com/albums/tt102/ste234/IMAG1792.jpg) (http://s602.photobucket.com/user/ste234/media/IMAG1792.jpg.html)
I've also painted the deck, not so sure about the colour though, maybe after a few more coats of paint?
(http://i602.photobucket.com/albums/tt102/ste234/IMAG1793.jpg) (http://s602.photobucket.com/user/ste234/media/IMAG1793.jpg.html)
Cheers,
Steven
-
Nice!
Now it starts to look the part.
Regards, Jan.
-
Cheers guys!
Still unsure how I'm going to paint it, thinking of spraying the hull and superstructure, and hand painting the deck. I've got a nut brown paint that I think will go well on the deck!
Steven
Thats how I did mine a few years back. It was my very first build and thoroughly enjoyed it.
www.modelboatmayhem.co.uk/forum/index.php/topic,7644.msg85083.html#msg85083
-
Thanks for the link Robert, your deck looks a lot better than mine at the moment, what paint did you use?. Also, how did you get on regarding the motor? I have had my suspicions before reading your thread that it doesn't look like a particularly fast one?
Cheers,
Steven
-
I was trying to remember, I followed the build in MB magazine, it was a tinlet of enamel. I switched the motor to a Graupner 400 and put in a universal coupling, as well as a mini-servo, cutout and installed just forward of the rudder post, all this made her much quicker and good scale speed and more responsive in turns.
Robert
-
Cheers Robert, I will wait till the pond an see how I feel about the speed then make a decision.
Done a bit more this evening, hull now fully painted, awaiting white stripe on waterline. The mast has been done (lost the parts for this!) with some spare pieces i had lying about, and I've clagged a handrail on one side of the superstructure:
(http://i602.photobucket.com/albums/tt102/ste234/IMAG1797.jpg) (http://s602.photobucket.com/user/ste234/media/IMAG1797.jpg.html)
(http://i602.photobucket.com/albums/tt102/ste234/IMAG1795.jpg) (http://s602.photobucket.com/user/ste234/media/IMAG1795.jpg.html)
(http://i602.photobucket.com/albums/tt102/ste234/IMAG1796.jpg) (http://s602.photobucket.com/user/ste234/media/IMAG1796.jpg.html)
Cheers!
Steven
-
Model Slipway are usually good for spare fittings, but I'm not sure if they still do this kit.
Robert
-
Which model did you find on the WWW.Kitshackmodels.com (http://www.kitshackmodels.com/) site, if I may ask?
Regards, Jan.
Go to "Search" bottom of list on LHS
Type RTTL in search box and enter.
Strange they're not listed in the main add.
Regards Ian.
-
Thanks Ian!
Both kits are a bit large for me (and my car...) though.
Regards, Jan.
-
Smaller one on this site Jan?
http://modelboats.hobby-site.com/ (http://modelboats.hobby-site.com/)
Regards Ian.
-
Anyone got any tips on how to stop the rubber flexible coupling from the motor to the prop from slipping off? Just tried it in the bath tub and it keeps slipping off once it gets to a certain speed?
Not sure what I'm doing in this instance!
Cheers
Steven
-
It's obviously stretched a bit. Can it be replaced ?
Marks Model bits do have these if you want to replace it.
Cheers
Ken
-
Great, thanks for the pointer.
I've just had a good look at the boat and I think I've found a bit of the problem...
The propshaft comes into the bottom of the hull quite close to the bottom, so theres quite an offset between the prop and the motor shaft. I can sort it by lifting the back of the motor slightly if I need to? I think this might help the problem?
Cheers,
Steven
-
Hi Steven,
That's not a 'bit of a problem', that's how a motor should be mounted; in perfect allignment with the propshaft without any angle to speak of.
The propshaft in my MAS has a 7-8° angle, so has the motormount:
(http://www.modelbouwforum.nl/forums/members/pompebled-albums-motoscafo-anti-sommergibile-picture156599-waterkoeling-03.jpg)
Regards, Jan.
-
Hi Jan,
thanks for your reply, I understand what you are saying, however, with my motor secured, this is how the coupling looks:
(http://i602.photobucket.com/albums/tt102/ste234/IMAG1810.jpg) (http://s602.photobucket.com/user/ste234/media/IMAG1810.jpg.html)
Which is why I think it keeps slipping off, it's basically getting pulled off?
However, if I prop the motor up from the rear, it makes the coupling look like this, should I do something to make it permanently like this?:
(http://i602.photobucket.com/albums/tt102/ste234/IMAG1811.jpg) (http://s602.photobucket.com/user/ste234/media/IMAG1811.jpg.html)
Cheers,
Steven
-
You need to lessen that angle as much as possible,but even if you take away the motor mount and can hopefully secure the motor, it looks like there will still be an angle on it...As the earlier post says the shaft and motor should be exactly in line.Can you alter the prop shaft angle?Good Luck with that one.Bob.
-
I could alter the angle, but it would mean cutting the propshaft out from where it's held on the outside of the hull, which may not be easy, then re-positioning it inside aswell. Looking at it I don't think I fancy trying it, and I don't think the angle will be that much better than propping the back of the motor up as best I can,should be easier aswell I think?
Cheers,
Steven
-
Thing to do Steven is secure the motor as in the 2nd picture,put the gear in and try it on the water.This is your main priority.If the tube falls off or vibration etc or generally 'no good',then i'm afraid.. <*< ....with patience the tube will come out and you can then get it properly in-line and all will be sorted.No way could you see it working as in the 1st picture.Again,all the best.Bob.
-
Cheers Bob, will hook it all up at the weekend and give it a spin :-))
-
I had a similiar problem with mine Steve. I molded some modelling clay in the motor mount to get the angle of the motor to sit true to the prop shaft and used wire to secure the motor in as it gets a bit warm and melts the rubber band they suggest, then put a proper universal coupling in as the rubber coupling kept slipping off, try this it worked week for mine. Almost classified as a fast electric. :-))
Robert
-
if you draw back the engine 1 inch you'll have a pus open angle.
You will not need to change the angle of the motor shaft
Buy a real coupling, you will not be bothered
your piece of rubber is of the breast, it is not reliable
-
Hi Steven,
Oh dear...
The rubber coupler will only work if motor and propshaft are alligned perfectly, this is easily acheived by taking a longer shaft.
With a longer shaft, the motor can slide forward until the allignment is 100%.
You'll need to make another motormount (preferably without using rubber bands, even household silicone would be preferable), but that's no problem for a modelbuilder. You can even use 3 mm thick styrene card to make a motormount, just don't block the cooling slots on the shaft side of the motor.
If a longer shaft isn't an option, you could go for a coupler like this:
http://www.robbe.de/navy-kardan-44.html?___store=en&___from_store=de
Available in the UK from Cornwall boats:
http://www.cornwallmodelboats.co.uk/acatalog/robbe-coupling-assemblies.html
This coupler is long enough to 'emulate' a longer shaft and also requires a new motormount.
Don't be tempted to use the coupler to compensate for the odd angles in the first picture, make sure things are alligned properly!
Regards, Jan.
-
Thanks again for the replies guys, I will try some of the ideas and see what I can do.
Jan, Unfortunately the motor mount is vac formed as part of the internal tray, so removing it would leave a big gap where it was. I'll try some other options first but will bear this in mind.
Hopefully I will have some good news tomorrow if I get time to look at it!
Cheers for the help everyone!
Steven
-
The internal tray with the motor mount in the right location
should allow the motor to align with the shaft in the right
location/angle.
The motor shaft and the prop shaft should align or you
will suffer vibration/overheating and more current drain.
Ned
-
Unfortunately the motor mount is vac formed as part of the internal tray, so removing it would leave a big gap where it was.
Hi Steven,
That's not really an issue, a cutting disk in a Dremel will take care of the plastic part and a couple of pieces of styrene sheet, cut to fit, will cover the gaps (or not, covering the gaps would be cosmetically, as there's the bottom underneath, isn't it?).
Having reasonable access should be more of a concern when fitting a new motormount.
Regards, Jan.
-
Strange one this.Were you aware of this situation when you first started the kit 6 years ago?Is it the original motor?The angle of the shaft in the previous picture from outside looks 'ok' as if it should line up with the motor/mount,no problem,yet doesn't.Surely,the motor mount has to be dremelled out and the motor lowered or the shaft re-aligned? Trying to help.Bob.
-
Would moving the motor as far back as possible and then link to the prop shaft with either a single or double coupling be better, from the picture the prop shaft entering appears to be a little 'low' and may explain why the angle is so sharp, or it's designed for a motor with a smaller external diameter?.
-
Or a motor with an offset drive?
If you need to move the motor forwards (Towards the front or Bow) you could connect with one of these :- http://miponline.com/store/page24.html
Regards Ian.
-
or move the motor further away vertically and use a geared setup or a vee belt drive, adjusting the tension by packing out the motor from underneath, just a thought
-
No space underneath without extending the shaft.
Would think the original build has been deviated from.
Regards Ian.
-
It does appear that the propshaft entering is too low. The hole should be 7-10mm from the bottom in order to lign up with the motor shaft.
Regards
Jackie
-
Ah right cheers Jackie, I see where I have gone wrong. It doesn't actually say about the 7-10mm in the instructions, just to use the skeg as a guide for the hole.
Right, looks like I'll have to remove the propshaft. Should be able to do it by taking a hacksaw in between the skeg and the shaft, that should free it off, and re work that bit then!
D'oh!
Cheers,
Steven
EDIT: I tell a lie! just had a look at the boat now, looking at the hole that comes through into the tray. By the looks of it, the glue that was holding the prop up into the correct position has given way somehow, thus letting the prop sit lower. I've just jacked it up by sliding some plasticard inderneath, and it now sits within a couple of mm of the shaft! Think I'll drop a spot of glue on it and try that first!
-
Wonder if you've stored the boat for six years in a hot summer loft,shaft sitting on hard surface...not on a stand... things on top of it...weight...the glue has softened,shaft shifted...maybe this is what's happened?.At least you're getting there.The motor and shaft have to line up exactly,then it will work...Good Luck.Bob.
-
Right, well. I've managed to line the shaft up with the motor by lifting the prop to the top of the hole and wedging it there and gluing it. But (and that's a big but!) the tube has now got a very slight bend in it, in between the hull entrance point and the end of the tube inside. Obviously this isn't right, and makes the propeller wobble when it's running, and when dropping the prop back in it stops at this point. Looks like the whole thing is coming out after all...
Looking at the hull outside, the prop-shaft and skeg aren't quite central, so I'm going to have to remove it, and re-drill the hole bit further over unfortunately!
Oh well!
Steven
-
It's not that bad. We've all had alignment problems but not as much advise as you've received.
Imagine how proud you'll be when you line up the new one. ok2
Cheers
Ken
-
Cheers Ken.
New prop has been ordered from Model Slipway, might aswell renew it, more for my piece of mind I think!
I think half the problem is this is my first working model boat build, I've never had to align the prop before!
Cheers
Steven
-
The new prop and bits arrived today from Model Slipway, (Thanks for the helps there guys!) so I proceeded to rip the old prop out. Thankfully it has come out without too much damage, the skeg is still intact and nothing else is damaged so it all looks good so far!
One question I do have, does it matter what angle the Prop comes out of the boat at? I mean, obviously 90 degrees would be no good, but is there a certain angle, or just whatever lines up with the motor best?
Cheers,
Steven
-
Hi Steven,
If it's a planing hull, 7° is regarded as the limit, less angle is better, but not always possible without resorting to a (much) longer propshaft and extensive surgery.
Regards, Jan.
-
Good luck with this Steven,you have persevered with this and should get it right now.Go carefully and think about it...post pics? Lots of interest as well.Bob.
-
Cheers Jan, I will have to see how well I can get the new one to line up, I doubt the motor will be powerful enough to allow it to plane anyway!
Bob, thanks, I'm going to take my time with this bit (albeit not 6 years again!). Ask and ye shall recieve:
This is how the propshaft "hung" when I cut it off, which probably shows how bent it must have been!
(http://i602.photobucket.com/albums/tt102/ste234/IMAG1821.jpg) (http://s602.photobucket.com/user/ste234/media/IMAG1821.jpg.html)
And looking from the stern towards the bow, not the best photo as its that fine its hard to capture, you can sort of see the hole (the white blob) where the prop enters is slightly off the center line, I think this is giving me some of the left to right alignment grief:
(http://i602.photobucket.com/albums/tt102/ste234/IMAG1823.jpg) (http://s602.photobucket.com/user/ste234/media/IMAG1823.jpg.html)
Thats all for now, won't be much progress this weekend as I'm away camping!
Cheers,
Steven
-
Hi Steve,
The skeg piece gives the proper angle for your prop shaft. You could cut a new piece as per the instructions when aligning your new shaft. File out the hole where the shaft enters the hull and where it enters the motor mount tray, once all is temporarily fitted it can then be epoxied in. By taping around the propshaft prior to applying the epoxy should prevent overflow and give a smoother finish.
Hopefully this helps.
Robert
-
Cheers Jan, I will have to see how well I can get the new one to line up, I doubt the motor will be powerful enough to allow it to plane anyway!
Bob, thanks, I'm going to take my time with this bit (albeit not 6 years again!). Ask and ye shall recieve:
This is how the propshaft "hung" when I cut it off, which probably shows how bent it must have been!
(http://i602.photobucket.com/albums/tt102/ste234/IMAG1821.jpg) (http://s602.photobucket.com/user/ste234/media/IMAG1821.jpg.html)
And looking from the stern towards the bow, not the best photo as its that fine its hard to capture, you can sort of see the hole (the white blob) where the prop enters is slightly off the center line, I think this is giving me some of the left to right alignment grief:
(http://i602.photobucket.com/albums/tt102/ste234/IMAG1823.jpg) (http://s602.photobucket.com/user/ste234/media/IMAG1823.jpg.html)
Thats all for now, won't be much progress this weekend as I'm away camping!
Cheers,
Steven
StevenT
From the above picture I would suggest that not only you remount the prop shaft at a shallower angle, but that you also give some consideration to relocating the prop farther to the rear of the boat. Not sure how you decided on the current location, bit it appears to me too far forward. Also when building a new boat, I locate the prop shaft first, including a shallow angle and then line the motors up with the shafts. The closer you are able to line the motors with the shafts, the less parasitic drag you will have and also less vibration.
Larry
-
Hi Larry, The prop is in the correct place according to the drawings, besides I don't think it would go any further back due to the limitations of the fixed motor mount.
In the news, I have finally got round to filing the two holes out, so I can now get the propshaft to line up with the motor properly!
Going to either fix it in place tonight or the weekend now.
Any ideas whats the best glue to use? and how to make sure it stays aligned whilst the glue dries? I was thinking of using a fast drying superglue to hold it then epoxy it into place after?
Cheers
Steven
-
I was thinking of using a fast drying superglue to hold it then epoxy it into place after?
Steven
Hi Steven,
That should do it.
Add glasscloth to the epoxy if required on the slot in the hull.
Regards, Jan.
-
Cheers Jan.
Just been looking at it again, and I've hit another (yes, another...) problem.
Basically, if i let the propshaft "hang" so that the coupling is straight, the shaft is no where near the skeg (which is the right size, in the right place according to the drawings). If I hold the shaft up to the skeg, the coupling gets a kink in it. Hope these pictures explain that better;
(http://i602.photobucket.com/albums/tt102/ste234/PA173111.jpg) (http://s602.photobucket.com/user/ste234/media/PA173111.jpg.html)
(http://i602.photobucket.com/albums/tt102/ste234/PA173112.jpg) (http://s602.photobucket.com/user/ste234/media/PA173112.jpg.html)
And with the shaft held against the skeg:
(http://i602.photobucket.com/albums/tt102/ste234/PA173113.jpg) (http://s602.photobucket.com/user/ste234/media/PA173113.jpg.html)
(http://i602.photobucket.com/albums/tt102/ste234/PA173114.jpg) (http://s602.photobucket.com/user/ste234/media/PA173114.jpg.html)
Any ideas guys? I'm thinking about making the skeg bigger so the shaft sits true with the motor, don't know if this causes any more problems, I can't see why it would?
Cheers,
Steven
-
hey steve,
just make that hole in the tray abit bigger, and then when everything is line up true, epoxy it all in.
robert
-
The Skeg looks a bit 'weedy'. Have you thought about making it a bit deeper, so as to come down to the prop tube ?
regards
ken
-
Isn't this where you started off?The shaft has to line up exactly with the motor spindle,the rubber will spin off like that....better to have a coupling.All the best with it.Bob.
-
Right, made up a bigger skeg today, new propshaft is fitted, lines up a lot better with the motor now! The angle of the skeg and shaft has increased, but I'm not concerned about this now it all lines up nicely!
Will put a photo on tomorrow!
Cheers for the tips again guys, feel like I'm getting somewhere with this now :D
Steven.
-
Keep in mind that with a prop shaft angle such as you presently have that boat will have a difficult time getting up on plane. The propeller is pushing the boat directly up the shaft, at the exaggerated angle you are presently running, the prop will be trying to push up on the hull as much as it is pushing forward. Optimum shaft angle is 10 degrees or LESS in relation to the keel, your present setup looks to have 20 or more degrees.
Just because you located the prop according to the instructions does not mean it is at the optimum angle or location. The guy who drew the plans may have had to make concessions in motor location and shaft angle due to size and/or shape of the hull and available space.
I still maintain for the best performance of your boat the prop should be moved rearward and the angle decreased to below 10 degrees. Get the shaft in the proper location, then align the motor to it.
-
Hi Bubbletop, To be honest I'm not too bothered if the hull doesn't come up onto the plane. I think what I'm going to do, seeing as though I've just refixed the shaft in place with the greater angle, I'll see how it goes when I get it on the water. If I feel it's not good enough then I'll strip it back down and see what I can do. I don't really want to strip it all down again now, to find out I'm not going to be able to get it right again!
Steven
-
Wouldn't it be better to get it right now given the advice,rather than be disappointed with the performance given they are fast-ish boats and then have to strip it all down again?Bob.
-
hi ya there
May I make a suggestion; carry on the way you are going; fit the propshaft the best you can at the angle you can and put the model in the water and enjoy the model. Keep one thing in mind, this is a semi scale model; and it will be a learning curve for you. It wont have any spectacular performance - no matter what you do with it's current prop shaft and motor alignment - the only way you would do that is if you want to spend some mega bucks and go brushless with lipo batteries. Does the model warrant this expense? If you like these type of models there are plenty true to scale kits out there - and plans - which you could build and have the correct prop shafts at the correct angles and get far better performance. I have built a number of air sea rescue craft and they are all documented on this forum so if you are looking for something else to do have a look at some of the postings on the forum here.
aye, John
-
Cheers John, Already thinking of doing something else but not sure yet, I was thinking the deans marines crash tender but need to look into it more!
Had the boat in the bathtub earlier this evening, and put it this way, the angle of the prop is staying as it is! In the relatively short length of the bath tub, it's just as fast as any of the larger "toy" rc speed boats I had as a kid, which is fast enough for me! Obviously it didn't really have chance to get to full speed, but still!
I have noticed one thing, theres a very, very small amount of water came up the propshaft as I put the boat in reverse, is there any particular reason for this or is it just one of those things?
Cheers
Steven.
-
...the provided shaft doesnt have any bearings, so will allow some water ingress, the solution, don't go in reverse, its meant to go scale speed, forward, which looks good. Get it sorted and out to the pond and you'll have loads of fun if you don't go in reverse {-) .
Robert
-
Hi Guys,
Over the past week I have bought a universal coupling and a Graupner speed 400 motor for this boat.
So today I took it for it's inaugural sailing.
Firstly, it didn't sink, which is always a good start!
Secondly, it planed rather nicely and the speed was more than acceptable until the battery started dropping off after about 1/12 hours of running! The motor did get rather hot, but after I found out what it was capable of I wasn't giving it an easy time either!
My friend who came to the lake with me reckons I should stick a brushless motor in which would solve the hot motor issue.
But anyway, heres a few pics and a half-hearted attempt at a video, The sun was in the wrong place aswell which didn't help with the camera!
(http://i602.photobucket.com/albums/tt102/ste234/PB163492.jpg) (http://s602.photobucket.com/user/ste234/media/PB163492.jpg.html)
(http://i602.photobucket.com/albums/tt102/ste234/PB163491.jpg) (http://s602.photobucket.com/user/ste234/media/PB163491.jpg.html)
(http://i602.photobucket.com/albums/tt102/ste234/94907b73-7a7b-4c62-bc22-244cb50e945b.jpg) (http://s602.photobucket.com/user/ste234/media/94907b73-7a7b-4c62-bc22-244cb50e945b.jpg.html)
(http://i602.photobucket.com/albums/tt102/ste234/33ec13c7-d00b-471c-ba24-f9f66005fcf2.jpg) (http://s602.photobucket.com/user/ste234/media/33ec13c7-d00b-471c-ba24-f9f66005fcf2.jpg.html)
(http://i602.photobucket.com/albums/tt102/ste234/f32e4674-9412-44db-9db5-ee5676bfd6a1.jpg) (http://s602.photobucket.com/user/ste234/media/f32e4674-9412-44db-9db5-ee5676bfd6a1.jpg.html)
http://www.youtube.com/watch?v=SLrYcEuAx1M (http://www.youtube.com/watch?v=SLrYcEuAx1M)
Cheers,
Steven
-
Well done Steve,that looks a treat after all your angst recently,great lake too.Bob.
-
nice steve, very nice. now lesson learnt, and so many kits to buy eh! have fun...that is a big lake :-))
-
Cheers guys :-)) I am very pleased with its performance. Think I have found a suitable brushless setup for it aswell now, this motor, which is the same size roughly as my current brushed:
http://www.hobbyking.com/hobbyking/store/__15187__S2838_2800_Brushless_Inrunner_2800kv_.html (http://www.hobbyking.com/hobbyking/store/__15187__S2838_2800_Brushless_Inrunner_2800kv_.html)
and a Speed controller:
http://www.hobbyking.com/hobbyking/store/__29430__HobbyKing_30A_Boat_ESC_3A_UBEC_UK_Warehouse_.html (http://www.hobbyking.com/hobbyking/store/__29430__HobbyKing_30A_Boat_ESC_3A_UBEC_UK_Warehouse_.html)
I think these should be suitable?
As for the lake, It's where Darlington Model boat club sail. Thinking of joining soon. It's an old reservoir and the water is crystal clear!
Cheers!
Steven
-
Hi Steven,
No at both items...
Assuming your boat runs on 7,2V, a 2800KV motor would give you 18.000 rpm under load, which would come close to strapping a blender under the hull, lots of foam and no forward speed to speak of.
You'd say: well I'll run half throttle...
That would mean overheating both motor and ESC as they don't respond well to continously running partial throttle.
Talking about overheating; the motor will need watercooling, which would require another motormount, without a longer propshaft you might have problems getting the proper allignment.
An 30A ESC for a 300W motor on 7,2V is too low (300 : 7,2 = 40A peak).
I'm going to watch the F1 qually now, I'll post some suggestions later.
Regards, Jan.
-
Hi Jan, would it not be that the 300W is produced when the motor is running at full voltage of 14.8v, so when it's running on 7.2v, it should in theory only be using around 150W, which would mean it would only be around 20A peak on 7.2v?
Cheers,
Steven
-
Hi Steven,
Wattage is V x A, if you lower the Voltage, the Amps go up under load.
As an example of how a continuous load heats things up:
The testruns with my MAS powered by a 1000W 800KV outrunner were made without watercooling, running on 14,8V, this meant a peak current of over 60A, so I used a 150A ESC.
I walked next to the boat along the canal, so the speed was a brisk walking pace, with the occasional burst of full throttle, but 90% of the runtime was at partial throttle.
After over an hour (it's a long canal), the boat stopped.
When it has floated back to me the motor was boiling hot as was the ESC, both items smelled slightly 'electric', I burnt my fingers on the motormount, so I didn't try to touch the motor...
Fortunately the ESC had shut down thermally, otherwise it would have burnt up.
Granted, the weather was warm, the unfinished hull (no deck yet) was exposed to direct sunlight and the runtime is rather extreme, compared to pottering around on the pond, but that's how I use my boats, as our town has a lot of canals, but no suitable model pond.
So, even with an ESC with an headroom of 100% compared to the max motorcurrent, it shut down eventually.
After watercooling was installed, both motor and ESC never exceeded 45°C, currently the boat runs on a watercooled 100A ESC and it stays cool.
------------------------------------------------------------------------------------------------------------------------------------------------------
Assuming you got this motor for your boat: http://www.graupner.de/en/products/1794/product.aspx (http://www.graupner.de/en/products/1794/product.aspx) I think I know why the motor got hot.
In the video the motor didn't sound like it was revving at 15000 rpm, half that is more likely, meaning you're bogging down the motor severely.
It'll still do it's best to get up to the rpm dictated by the Voltage applied and will draw quite a lot of current, heating things up.
As no brushtab or cancooling was installed, the heat build up has nowhere to go.
Another point (literally) is breaking in a brushed motor; new brushes have just two tiny contactpoints to the commutor.
When you apply full throttle, all current has to flow through these minute points, the brushes will arch badly and possible burn into the copper of the commutor, damaging it for the rest of its working life.
The arching also causes a lot of heat.
A new brushed motor should be broken in, running submerged in a glass of water, on an as low Voltage as possible (1,5 - 3V) to avoid arching.
When the water starts to get dark, check if the brushes have assumed the curve of the commutor, if so, dry out the motor (compressed air work well) in a warm place, put a tiny(!) drop of oil on the bushings and you're good to go.
Brushless thoughts:
For an underwater prop, rule of thumb is about 10.000 rpm under load.
Running on 7,2V, the math is simple and would mean a motor of about 1400 - 1500KV.
In-runners with such a low KV are often a Ø36 mm size, so fitting that into your boat would mean major surgery.
Also the low end performance of an in-runner is often non existant and the motor will burst into life at one third throttle, making crawling along an illusion.
As most outrunners have more poles, the low end response is much smoother (albeit brushed motors still do a better job in direct drive).
As cooling an outrunner has it's limits, it's wise to choose a bigger motor to have more headroom.
Something like this would work nicely, make sure it'll fit and include space for a watercooled motormount (bought, or DIY):
http://www.hobbyking.com/hobbyking/store/__16234__NTM_Prop_Drive_Series_35_30A_1400kv_560w.html (http://www.hobbyking.com/hobbyking/store/__16234__NTM_Prop_Drive_Series_35_30A_1400kv_560w.html)
Smaller and still plenty of power:
http://www.hobbyking.com/hobbyking/store/__25078__NTM_Prop_Drive_28_36_1400KV_560W.html (http://www.hobbyking.com/hobbyking/store/__25078__NTM_Prop_Drive_28_36_1400KV_560W.html)
To control it, a car ESC gives you a smoother low end than a boat ESC, something like this:
http://www.hobbyking.com/hobbyking/store/__17232__Hobby_King_60A_Sensored_Sensorless_Car_ESC_1_10_1_12_.html (http://www.hobbyking.com/hobbyking/store/__17232__Hobby_King_60A_Sensored_Sensorless_Car_ESC_1_10_1_12_.html)
The fan cooled heatsink isn't very effective in a closed hull, but taking off the fan and watercooling the ESC by making a watercooler, fitting on the same boltpattern as the heatsink is relatively easy to do.
If you don't want to go that route, Hobbyking also has the watercooled version available, but I have no experience with these (yet) so I can't say how well the low end response will be:
http://www.hobbyking.com/hobbyking/store/__28223__HobbyKing_90A_Boat_ESC_4A_SBEC.html (http://www.hobbyking.com/hobbyking/store/__28223__HobbyKing_90A_Boat_ESC_4A_SBEC.html)
Regards, Jan.
-
Right, thanks for that Jan, certainly something else to get my head round this brushless stuff!
Would a brushless that only does 10,000rpm be enough to bring my model up onto the plane? I believe the motor in the video should have been running at around the 15,000 rpm mark on the video, the battery was fully charged (7.2v, the same as the motor rating) and the throttle was fully open?
Also, I don't want to have to hack away the motor mount, I'm not confident enough that if I take it out (major surgery which is not reversible) I can make something suitable to go back in its place and space is tight in this model, so a bigger motor would make things rather awkward...
Watercooling would be tricky aswell, due to there being the internal tray, and again, limited room inside the model.
I think I may be best sticking with what I have got at the moment...?
Cheers,
Steven
-
Would a brushless that only does 10,000rpm be enough to bring my model up onto the plane?
Hi Steven,
An 800KV outrunner powers my 110 cm MAS, running on 4S (14,8V), turning a Ø60 mm prop, at about 10.000 rpm under load.
Watch the video and see if this answers your question:
http://www.youtube.com/watch?v=-igDcvLySEM&feature=youtu.be
Do turn up the sound (as high as you can) to hear the running noises, as my cameraman/nephew has muted the sound too much.
Regards, Jan.
-
Haha, only just then :-))
Just got back from the lake again, took my dad through to show him it running. The motor ended up getting very hot again, and partially deforming the motor mount, which is of course just plastic...
At a bit of a loss of what to do now, as either way I'm getting a warm running motor... The ESC is just fine, no problems there.
Looks like I might have to butcher the motor mount and make another with enough room to add water-cooling. It won't be easy mind, infact, I don't know if it can be done...
-
Just had the boat in the bath to see how much current its pulling. With just the motor, me holding it in my hand, no prop or anything, it pulls half an amp at full speed, which is what the motor spec says it will, with the motor just getting luke warm. With the prop connected via the uni joint and the motor in the boat, the consumption goes up to 7.5A, and the motor becomes very hot. I think I might try it with the old rubber coupling, just to see what sort of current it pulls with that on...
-
Is the prop the right type/size/pitch for the motor?
Ned
-
To be honest Ned, I don't really know. The prop is the same one that was supplied with the kit for the 385 motor, which I have changed to a 400 now. Anyway to tell if it is suitable?
Cheers,
Steven
-
Not sure.
But someone on here will know. :-)) :-))
Ned
-
Just had the original 385 motor in the boat with the same uni joint and prop, it only pulls around 1.5A at full speed, although the full speed is no where near that of the 400 motor, maybe it is the propeller?
Steven
-
I was once told that unless you're racing water cooling is the fallback for a badly matched prop and that's something I try to live by.
Can you measure the prop and put some photos up? Measure the diameter and try to guess the pitch of the blade. It's a large boat to move at any speed with a single 400 size motor so picking a small prop or one with a less aggressive pitch will probably help the current consumption and therefore heat. If your motor runs about 15krpm unloaded a 25mm prop with 1:1 ratio (pitch also of 25mm, blade angle 45 degree at the tip) would probably be about right. It's certainly a place to start. Be aware that water doesn't scale like props do, so a scale-looking brass prop is relatively inefficient compared to an efficient design at this size and you may need to compromise between scale-look and performance/efficiency.
-
If I'm measuring the diameter right, I think it's a 30mm prop, how would I measure/guess the pitch? What am I looking for?
(http://i602.photobucket.com/albums/tt102/ste234/PB173497.jpg) (http://s602.photobucket.com/user/ste234/media/PB173497.jpg.html)
Like I say it's just the prop that was supplied with the kit, for the 385 motor.
I have spoke to Robert (rem2007) who I got the idea of changing the motor from and he has kept the original prop. He says his gets warm, and that he lined the motor mount with modelling clay. Might have to give the clay a try, will probably act as a heatsink...
Cheers,
Steven
-
Assuming you got this motor for your boat: http://www.graupner.de/en/products/1794/product.aspx (http://www.graupner.de/en/products/1794/product.aspx) I think I know why the motor got hot.
In the video the motor didn't sound like it was revving at 15000 rpm, half that is more likely, meaning you're bogging down the motor severely.
It'll still do it's best to get up to the rpm dictated by the Voltage applied and will draw quite a lot of current, heating things up.
As no brushtab or cancooling was installed, the heat build up has nowhere to go.
Another point (literally) is breaking in a brushed motor; new brushes have just two tiny contactpoints to the commuter.
When you apply full throttle, all current has to flow through these minute points, the brushes will arch badly and possible burn into the copper of the commuter, damaging it for the rest of its working life.
The arching also causes a lot of heat.
A new brushed motor should be broken in, running submerged in a glass of water, on an as low Voltage as possible (1,5 - 3V) to avoid arching.
When the water starts to get dark, check if the brushes have assumed the curve of the commuter, if so, dry out the motor (compressed air work well) in a warm place, put a tiny(!) drop of oil on the bushings and you're good to go.
Hi Steven,
Sorry to hear the motor keeps overheating, I quoted my earlier message about why this may happen, if the motor is the one from the link, it may be toast by now...
You 'upgraded' to a hotter motor, didn't brake it in and kept the same prop as supplied for the stock motor.
I was once told that unless you're racing water cooling is the fallback for a badly matched prop and that's something I try to live by.
As mentioned above, the prop is too large and the motor can't rev out and runs (very) hot.
Watercooling is rarely necessary in scale boats, only the occasional over powered ones (like my MAS) may require some cooling assistance, but as StuartL correctly stated, it's not a bandaid for a poor setup.
Modeling clay will absorb some heat, but if the setup isn't sound, the motor will keep overheating until the magnets get demagnetized and the motor looses all power.
A Speed 400 revs too high for this application; a smaller prop will help a little, but the performance will suffer, as the mismatch remains.
Regards, Jan.