Tench745
Master member
There are generally two reasons to fiberglass.
1) Establishing a nice, smooth surface to paint over.
2) Adding strength.
If all you're looking for is #1, then some 1/2 oz or 3/4 oz glass coated in water based polyurethane (WBPU for short) works well. The resulting finish is also more resistant to hangar rash, but it adds very little strength to the plane. I have glassed three foam planes like this and I did a balsa seaplane with 1/2 oz glass and epoxy for slightly more durability than the WBPU.
If you're looking to add strength like they did in the FT video, then I have much less experience with that on model aircraft.
I have, however, built two rowing dinghies that I covered in epoxy and glass.
I would not recommend using a polyester resin like Bondo on foam board. It will almost definitely eat the foam. Use epoxy. I have used West System, Total Boat, and Silver Tip epoxies and they all work fine. You can get an 8oz finishing resin kit from Z-poxy for $25. I think that should be enough to coat an Arrow, but I never remember how much I end up using. If you want to hedge your bets and get extra, you can buy a pint kit (16oz) of Total Boat's High Performance epoxy for $41. Then you'll have to buy some glass cloth. You want a woven cloth not chopped-strand mat. You'll probably have to order it online as most stores only carry 6oz or heavier fiberglass. 2 oz cloth seems about right for this job. Heavier cloth will be stiffer, but also heavier and require more epoxy to get it to wet out correctly. In the past I bought rolls of glass from thayercraft.com but that's way more money than you want to spend, and way more glass than you'll need for one plane. I'm afraid I don't have a source for small quantities of light glass, so you'll have to source that on your own, or try the 6oz stuff you can get in most hardware stores.
When you glass you want to apply enough epoxy to fully wet out the cloth, and then you want to squeegee off any excess to get a nicer finish and keep added weight to a minimum. I use old playing cards as spreaders when applying glass to models.
These are just the materials and techniques I have experience with. There are other options out there and other methods that can work.
1) Establishing a nice, smooth surface to paint over.
2) Adding strength.
If all you're looking for is #1, then some 1/2 oz or 3/4 oz glass coated in water based polyurethane (WBPU for short) works well. The resulting finish is also more resistant to hangar rash, but it adds very little strength to the plane. I have glassed three foam planes like this and I did a balsa seaplane with 1/2 oz glass and epoxy for slightly more durability than the WBPU.
If you're looking to add strength like they did in the FT video, then I have much less experience with that on model aircraft.
I have, however, built two rowing dinghies that I covered in epoxy and glass.
I would not recommend using a polyester resin like Bondo on foam board. It will almost definitely eat the foam. Use epoxy. I have used West System, Total Boat, and Silver Tip epoxies and they all work fine. You can get an 8oz finishing resin kit from Z-poxy for $25. I think that should be enough to coat an Arrow, but I never remember how much I end up using. If you want to hedge your bets and get extra, you can buy a pint kit (16oz) of Total Boat's High Performance epoxy for $41. Then you'll have to buy some glass cloth. You want a woven cloth not chopped-strand mat. You'll probably have to order it online as most stores only carry 6oz or heavier fiberglass. 2 oz cloth seems about right for this job. Heavier cloth will be stiffer, but also heavier and require more epoxy to get it to wet out correctly. In the past I bought rolls of glass from thayercraft.com but that's way more money than you want to spend, and way more glass than you'll need for one plane. I'm afraid I don't have a source for small quantities of light glass, so you'll have to source that on your own, or try the 6oz stuff you can get in most hardware stores.
When you glass you want to apply enough epoxy to fully wet out the cloth, and then you want to squeegee off any excess to get a nicer finish and keep added weight to a minimum. I use old playing cards as spreaders when applying glass to models.
These are just the materials and techniques I have experience with. There are other options out there and other methods that can work.
