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HelicopterScale Model RC Helicopters › How to scratchbuild a canopy..... Epoxy????
01-15-2003 10:37 AM  15 years agoPost 1
Eddielawson

rrNovice

Australia

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I want to have a go at scratchbuilding my own fuselages using the lost foam technique. When I lay down the fibreglass (or carbon fibre) is it correct that I use Epoxy resin? Will it sand ok when set? Should it be thinned somehow? I realise that alot of chemicals will eat the foam and that is why someone suggested epoxy, I just thought it was hard to sand to a smooth surface.
Any comments?
Thanks
Eddie

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01-15-2003 02:09 PM  15 years agoPost 2
Malorie

rrElite Veteran

Paw squared, MI

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Your best bet, if you are going through all the trouble to model a fuse, is to go all the way and make a mold so that all your hard work can be easily repeated. It is going to be very difficult to model a fuse entirely of foam and have the right final shape close enough that you won't need to fill anything in. If you go through the process of building a mold, you can sand and fill and whatever you need to do to get the final shape exactly right and not have to worry about weight. Then when you have the mold, you can repeat the model as often as you like in a VERY short period of time. I mean a crash could ruin all your hard work and then where are you? Making a mold is actually quite simple and you can always sell copies of your final fuse if people like it.

Here's a page with some great advice on how to go about it.

I have been doing and learning quite a bit about this process lately as I have designed a new canopy that will be in production soon. We are near completeion of the molds now. Only 1 1/2 months from start to molds and first canopy. If you have questions as you get further along, feel free to PM me.

Best of luck,
Malorie

Life's a journey, NOT a destination.

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01-15-2003 05:10 PM  15 years agoPost 3
scaleone

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Lakeland, FL

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On the other hand, there's a lot to learn about tool-making(creating molds) before you start any lay-ups. You need to know where to part the sections, how to create the overlaps or butt joints, how to inset, and the biggie-how NOT to create negative drafts that will lock your parts into the tool forever unless you want to destroy them in the process of removing them. Anybody who gives you a simplistic explanation of creating a plug and the molds isn't being real honest. You're going to have to create the perfect plugs anyway-the very same thing you'll do in making one via the lost-foam method. The difference will be that the plug will be hard so it doesn't warp or change shape as you build the tools over it. You'll have to make the plugs in pieces that will give you molds that will yield sections that will mate together in a way that allows assembly, installation of the mechanics, replacement of broken parts, and so on. If it was my first time and I knew very little about making molds, I'd use the lost-foam method just as a proof-of-concept model that I'd fly and see if I liked everything about it before I invested the cash in plug and tool making.
I've been in that business for many years, have my own kit line, and have done both. While I prefer to make plugs and molds, I'm that way because that's how I was taught and have been doing it for so long. A lot of the finer models out there have been done with the lost-foam method. The epoxy CAN be sanded and filled very nicely and if you do the intial laminations right, it won't take all that much work. It certainly takes less work, and a WHOLE lot less money! Molds aren't anywhere near as thin as the bodies-they're laid up to be extremely rigid, and this means many layers of heavy cloth and resin.
For the first time, I'd go with the lost-foam method until I had some more experience working with the materials-you can waste a lot of time and cash if you jump right into it. If you want to do molds, by all means go ahead but read up on it first, contact WEST SYSTEMS or FIBERGLAST for instructional info, and ask questions of those who do it already.
jerry

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