Fiberglass cloth, is it needed?
 

I have been doing research on glassing my Yellow Aircraft P-40 wings. All of the newest threads and videos of instructions say the same thing. That glassing the wings adds very little if any strength to the wing. It is used as a platform for the paint. I know that glassing gives the balsa wood a hard shell and helps to keep hangar rash down. But the hardness comes from the (in my case) Z-poxy and not the cloth. So is the cloth really needed? What if I just apply the Z-poxy as if the cloth was there? No weave to fill, no worry about sanding through the cloth, and less weight. OK, the weight savings is really not a worry on a 27 lbs airplane, but it is something. I made two test squares, one with glass cloth and one without. Both sanded between coats, and I cant tell the difference. The only difference is when I broke them. The glass cloth held the parts together, sort of. The breaking force was the same. On my first two P-40s, I just monocoated them. No strength problems with either one. But I want to add panel lines, and I think they will look better if the wing is glassed. So is the fiberglass cloth really needed? Thanks for your thoughts.

It will be more work and more weight without the cloth. The wood alone will soak up more resin and require more of it to get the wood grain filled.

OK...so would it be a bad idea to use a wood sealer first? That would keep the resin from soaking in as much.

Wood sealer adds weight too.

Good point.

I tried just epoxy resin once as a base for paint without the glass cloth. I will never do that again! It wasn't long until I had all manner of cracks in the paint.

now that is interesting. Do you think the cloth keeps it from "flexing" in some way? I guess I will add the cloth to the wings. Thanks for the information.

I finished a plane with resin over bare balsa years ago. What a mess. The glass cloth will add some strength (a little) but it will also help to keep the surface level which will reduce the amount of sanding. If you paint epoxy or resin over the bare balsa, it's not going to be very level. That means a ton of body work.

Put the cloth down over the balsa, paint on some resin then squeegee it back off with one of those cheapie plastic autobody spreaders you see in walmart or the auto parts store. When cured, sand the excess cloth from the perimeter and put down a second coat of resin only. You will not have a whole lot of sanding to do. Scrape the resin off the cloth pretty aggressively the first time. It sticks better if it's not thick.

Tip: sand your sheeting prior to gluing it on the plane. Once the sheeting is in place, don't touch it until the 2nd coat of resin has cured.

carl

Hi!
First of all use a profesional type of 24 hour epoxy and not the hobby type!
Epoxy and 25g glas fibre is going to make the plane a little heavier compared to a plastic film covered one but if you want panel lines and paint the plane with automotive 2-part acrylics (Which are the best) you must use epoxy and glasfiber.
Here is how you do it.
For a plane the size off a Top Flite Mustang you lay out, spread out the 25g glasfiber over one of the wing surfaces (Right or left side), either the upper or the under surface.
Then you pour epoxy on it and spread the epoxy with a thin plastic spreader (Not a gaming card which is too small). A brush also works fine. When you have done this ,take a paper towel and roll it over the wing panel soaking up as much epoxy resin as possible. Now you have done one panel! After it has cured for a couple of days ,do the same with the three other wing panels.
Then you lightly sand the wing and then make a mix of both brown microballons and 24 hour epoxy to a slurry and pour it over the complete wing, spreading it thinly over the entire wing with a plasic spreader.
When this has dried after a couple of days it can easily by sanded to a smooth surface.A surface that is much easier to sand then just an epoxy surface.
https://cimg8.ibsrv.net/gimg/www.rcu...4e512ac389.jpg
https://cimg0.ibsrv.net/gimg/www.rcu...6308267040.jpg

I normally just use polyester resin instead of epoxy. Mostly because it is around. I like the idea of mixing the microballoons. Might try that next time. I don't usually try for a professional finish, but would not complain if it looks good. Sometimes I just use the light cloth on the joints and just use the resin for a sealer. The grain usually shows.and two coats is normally all I use before paint. Again, it is not great, but it seems better to me than using a film on the fuselage especially. Film is best for wings IMHO.

My thanks to everyone for the insight. The reason for the question of no fiberglass is that I only have one lung left, and can not risk getting fiberglass into it due to sanding. I know that there are masks and filter systems. But to me its not worth the risk. I guess I will just use coveriing and do the best I can. Thanks again.

I suppose in that case most epoxies and for sure polyester may be off the list anyway. There are threads on water based polyurethane WBPU finishes. They are often clear coated with a two part automotive clear which may be a bad thing too. There is a clear WBPU option. The plastic films can be good though.

I don't see how the presence or absence of fabric will affect your lung issue. That being said, ANY sanding you do should be done with a full respirator with pre filters such as we use for painting cars. A touch uncomfortable perhaps, but 100% protection. When sanding balsa I just turn on a fan behind my shoulder and let it blow the dust away from me, but I have both functioning lungs. I broke my neck in 5 places and my back in 3, so I have other issues to worry about....

Scott

Scott, stay out of those places!