About Fiberglass?

[SteveH]

I've done a little bit of fiberglass work...built some products for a guy using his molds. It was piece work, made a big mess, consumed a lot of my time and shop space, and made very little money. The pieces were for airplanes and needed to be light weight. As I remember, they were three layers thick.

My question is, how many layers of fabric would it take to make fiberglass strong enough for a structure, oh I don't know, let's say something the size and application of a small travel trailer, that looked like maybe a Scamp or something like that?

Just having some night mares over here.

[madjack]

Steve, I don't have the answer for you in my head, but here is an article that might
http://www.rqriley.com/frp-foam.htm
madjack

[toypusher]

Steve, I don't have the answer for you in my head........

Sure there is ever anything in there??????

[madjack]

Steve, I don't have the answer for you in my head........

Sure there is ever anything in there??????

...since thought moves thru my head faster than the speed of light, I have long assumed that it is filled with a very high quality of vacuum.....
madjack

[toypusher]

Mine too!

[angib]

This is one of those 'how long is the string' questions. Here are my guesses - someone else may be able to give you an accurate figure.

If you are going to make something the size of a Scamp in unstiffened CSM (chop strand mat), I would expect to see about 10 oz/ft2 of glass mat. This would be 5 layers of the heaviest commonly-used CSM (2oz/ft2). It would be a bit over 1/4" thick and, when laminated, would weigh about 2.2 lb/ft2.

I hope this is right - I have had to convert from the metric measurements I would normally use!

In practice no-one would laminate this sort of body in chopped strand mat (in mat form, that is), except as a one-off, or few-off. As soon as you've got any volume to make, you buy a 'chop gun' which sprays resin and chopped glass and allows this sort of work to be done with much, much less labour, although it needs a bit of skill.



Depending on the design of the body (eg, what internal structure it has, any reinforcing steps in the surface), other materials or stiffening might be used to allow the amount of glass/resin to be reduced.

Andrew

On edit: If you were building weight-conscious aeroplane parts, you would have been using a woven (or even stitched) fabric. This makes a thinner, lighter, stronger laminate, but is ususally too expensive for a trailer body, where the lower-tech chop mat is used.

[SteveH]

Andrew,

Yes, the chopper gun is the way to go, but that assumes you have a mold. It's also way to messy to do at home.

I was thinking about a lightweight frame made from 1 X material in a sort of rounded shape, covered with some sort of light fabric, and then layers of fiberglass on the outside. Know it's not the most efficient way to build as far as time goes, but it's a way that could be done easily at home with no special tools. Sort of like building a fabric canoe and then fiberglassing it.

I know, I've got way too much time on my hands.

[Steve Frederick]

Steve H.
Have you thought about 'glass over foam?
If you built with 'glass outside/1/8" ply-wood inside, you would have a nice, strong, monocoque structure. I've built floats for some large, say 1/8 scale r/c planes this way. I'm going to try fenders over the winter too.

[angib]

I was thinking about a lightweight frame made from 1 X material in a sort of rounded shape, covered with some sort of light fabric, and then layers of fiberglass on the outside.

Some one-off cars have had body panels made something like this. Wax-paper wrap the tube frame and then stretch good glass cloth over it. Wet out the cloth (only works with cloth and you actually want the stuff that's not easy to wet out so the resin doesn't go straight through!) and once it sets, lay up as many extra layers of chop or cloth that you want.

The tricks are:
a) how not to get the cloth stuck to the 1x framework, if you don't want to leave the framework in;
b) how to keep tension on the dry cloth so it holds its shape when you wet it out.

Apparently both of these can be overcome, though I don't know the details of how to deal with b). Do some small scale tests and let us know how you get on!

Andrew

[Gaston]

I am building a "foam and glass" teardrop 10'x5x5tall. The structure is 1x3" pine with 1/8 door skin on each side and filled with pink foam insulation board and bonded together with epoxy. The outer layer will be another layer of pink foam(1 1/2") that I'll form to the shape I want. the cover will be a glass sandwich of 1 layer heavy boat glass ,1 layer baltek filler fabric and a top layer of light wt. finishing cloth, them painted to match my Cruiser. Makes a real strong box but the cost is way out there!!
I'll have more money in just the glass workand paint then it would cost me to build 2 plywood and alumiun skinned tears