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Old Jan 24, 2012, 01:28 PM
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1/35 Vospers MTB

Hey guys, I'm building the new Italeri kit to sculpt masters for crew figures. Instead of sending this to the shelf afterwards, I want to convert it to RC. I have the Tx/Rxs and plenty of 7.2 NiCads (lipos too, but no reason to use them that I can think of). I want to keep the running gear as faithful to scale as possible (for use in small reservoirs), so I'd like to recreate the static in working form.

Off the bat, I have a few questions.

The deck and hull meet nicely, there's a beveled slot with 7 spots to screw it down. I have Grade N52 Neodymium magnets I use to hold wings on aircraft (magnet to metal). I was thinking 14 of them in the 7 spots, going magnet to magnet would be strong enough to hold the deck in place and I could vaseline the channel if there was any seepage. Any concerns or experience using magnets on boats?

In terms of running gear, Any problem trying to duplicate the three screw in brass? I have plenty of 7.2 v brushed motors here from planes. I can mold and vacuum/pressure cast the props in resin, but I don't know if there are any concerns (I know there are no motor details) regarding 3 shafts (I intend wired together, single esc) or resin props (I have quite a few different types)?

Any help or ideas would be much appreciated. I'll be building the deck straight away for work, but have the luxury of the winter on the conversion. If you guys are interested, I'll post progress pics of the superstructure.
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Last edited by ausf; Jan 24, 2012 at 01:35 PM.
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Old Jan 24, 2012, 01:52 PM
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Glad to see another Vosper build

Hi: I've built a 1/14.6 scale Vosper MTB and also wanted to keep it true to scale running on 3 motors, direct drive. My boat is 60 inches long and made from balsa, plywood and brass and weighs only 17 pounds. I use 3, 4200mAh 9.6V NiMH battery packs. I'd look for brass 3-bladed props for your boat. They look better and can take a little more abuse. I've set my boat up with 3 Proboat ESCs operating on three independent channels. Most guys don't do this kind of set-up. There are several ways to set up a 3-motor configuration. A major concern for smaller scale PTs and MTBs is weight- build as light as possible. You might want to consider brushless outrunners or brushless can motors and LiPO battery packs. The other benefit derived from going brushless/LiPOs is space. Things are going to get a bit crowded under the deck of a 1/35th scale MTB with three motors in there. Going this route is not going to be cheap, however. I have a build log and videos of the boat on my website at: web.me.com/hookpilot Then click on "Hobbies" and take a look at the Vosper build log stuff. One more thought- If you really like this model and might want to build it bigger, use the kit as a model and scale everything up to a bigger size. This is what I did. I took a Revell 1/72 Vosper plastic model and scaled it up from one foot to 5 feet. Just get out your calipers and start drawing. Making a new model twice the size would give you a 1/17.5 scale model around 50 inches long. Keep the plastic kit for the fireplace mantle display. Bigger MTB models look so much better on the water too.

Good luck with your build.

Mike in Edmonds
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Last edited by hookpilot; Jan 24, 2012 at 02:03 PM. Reason: add more info
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Old Jan 24, 2012, 02:28 PM
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That's an impressive build Mike, I love it. A little too big for me at this point, although someday I'd like to build a 1/16 LCT for my Sherman.

The torpedo is great too, beautiful work.

I'll search around for brass prop once I get some measurements, etc. My first shot here with boats, I want to keep things tame.
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Old Jan 24, 2012, 03:24 PM
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Quote:
Originally Posted by ausf View Post
That's an impressive build Mike, I love it. A little too big for me at this point, although someday I'd like to build a 1/16 LCT for my Sherman.

The torpedo is great too, beautiful work.

I'll search around for brass prop once I get some measurements, etc. My first shot here with boats, I want to keep things tame.
I believe that the actual MTB props were about 22~25 inches in diameter. Converting that to metric ( for searches on European sites) at your scale comes out to around 15.7 mm to 17.8mm in diameter. Take a look at Prop Shop propellers from Harbor Models at:
http://www.harbormodels.com/site08/m...s_propshop.htm
Their .7" dia 3-blade prop might work out for you.

Mike in Edmonds
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Old Jan 24, 2012, 06:28 PM
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Shouldn't be hard to do... just follow one of the earlier build logs for Italeri's 1:35 Elco 80' PT or S-100 buy doing a search on the forum & you'll find great info such as Stu's thread to work from. As Mike mentioned, brass props are available.

http://www.rcgroups.com/forums/showthread.php?t=688351
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Old Jan 24, 2012, 08:12 PM
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Thanks, that thread is a goldmine of info and links. I was wondering if I could use K & S to make shafts and stuffing boxes but before I even got that far all my questions have been answered.
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Old Jan 24, 2012, 11:24 PM
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Keep it as light as possible. I am going to do my Elco, as a single screw, to aid with this issue. CB
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Old Jan 25, 2012, 12:46 AM
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G Factor makes a set of brass props for the Elco PT. I have not used these for operating models, so be careful. And I agree with previous posts. Keep your build light. If you must go with three, brushless and lipo is a must, in my opinion.
http://store.spruebrothers.com/135-g...01-p19496.aspx

Dave
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Old Jan 26, 2012, 12:44 AM
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Opinions Everywhere: Here's mine

This is just my opinion, but PT/MTBs represent a unique breed of model boat. For most kinds of models, who cares what it looks like below the waterline, 1 or 2 propellers, Korts, etc., but for PTs, having 3 engines is part of the magic. It was those 3, V12 Packard aircraft engines screaming away that got the adrenalin flowing. And when you lift off the deck, it will be the first thing people notice. “Look at that, 3 engines, just like the real thing.” A PT/MTB is a red-blooded can of Whoop-Ass in a small package. One engine in a PT is like putting a Smart Car engine in a Ferrari. Rise to the challenge. Put at least 2 engines in your 1/35th scale MTB. Brushless outrunners are so small and powerful that they beg to be stuffed in a small scale MTB. It will lighten the boat and give you flexibility. When you wrap up a plastic bag in one wheel, you still have the other motor to get you home. I had considered replacing my 3 Johnson can motors with some brushless outrunners and may still do it. Although I don’t need the power vs. weight advantage of going brushless and LiPOs. I built my boat extremely light- 60” length and 17- pounds all up weight. I have a friend in our club who modified the Midwest 48” PT installing the same set-up as I have. His boat is too heavy, actually more than mine, and it performs poorly. In the final analysis it is your build. Once you plop it in the pond and hit “GO” no one will notice how many motors are at work below deck. One more thought: most model PT Boats are over-powered producing speeds that are well above scale. At 1/35th scale, 40 knots seems very slow. My boat runs at a scale speed of 60+Knots wide open or about 10 knots in the real world and I wouldn’t want it going any faster. Choose your motor size carefully. Brushless outrunners, even small ones produce a lot of torque. Take a look at the E-Flight outrunners like the Park 250, only $32 apiece and weigh .5oz. Remember, you can run these on NiMH or LiPOs. You are going to be spinning some small props (18mm or so) with moderate pitch. I think you’ll be surprised at how fast your boat will go on a couple of these little motors. If you have access to a hobby shop, see if you can have them run a can motor or two and then run a couple of brushless motors of slightly smaller size. Use the old ‘try and stop the shaft from turning using fingers, torque measuring system.’ What makes this hobby so interesting and fun is experimenting to get what you want out of a model.
Above all else, have fun.

Mike in Edmonds
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Old Jan 26, 2012, 02:26 AM
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Weight, weight, weight!

THE PROBLEM, for those that don't have one is, the ready to run weight for the 1/35 Elco is just over 3lbs. Just weight the plastic parts, and you will find, that there isn't much room left, for running gear. So while 2-3 motors is COOL, it's just not practical. Care, and careful choices are needed, for it to work on a single screw, and, not set real deep in the water. CaptCB
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Old Jan 26, 2012, 09:59 AM
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HOOKPILOT, They were not aircraft engines. They were Packard marine engines and the only relation to aircraft was they were V-12's and used 100 oct av gas. They came from a long line of Packard marine racing engines. Just a bit of useless trivia.
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Old Jan 26, 2012, 11:25 AM
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Hookpilot...do you have brushless motors in your MTB and if so what are the KV of each one? I figure about 3000 watts for a 60" Boat, MTB or ELCO type would be in the right ballpark. Yes no?????
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Old Jan 26, 2012, 12:10 PM
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I'm going to complete the superstructure first (as I need to to pay the bills ), then I'll set it in the water, etc. to get an idea of where I sit.

Boats are new to me, so I have to wrap my head around a few things. I do love the idea of tinkering with brass and keeping it true to scale. I'll run some tests with the motors and batteries on hand and take it from there.

Thanks for the replies and discussion, the more debate there is the better my understanding of what this'll entail.
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Old Jan 26, 2012, 02:36 PM
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I have the Elco and the MAS kits, haven't built them as yet but they are great kits.
AUSF keep us current on your progress.
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Old Jan 26, 2012, 03:37 PM
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OK, great loking kit-what on line hoby shop has the best price?? Found one listed at 161.10$ +s/h any better deals out there??
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