Originally Posted by
serious power
Hi Matt,
What do you think of this water based 'polycrylic' for glass or carbon veil ??
One advantage of epoxy is that it is hard/tough, so when sanding it is resistant to wearing through .
Is it possible to apply the glass etc with dope or that polycrylic and then fill it with epoxy ??
I suppose I'm asking what is the lightest and stiffest/strongest and or most stable combo to get a paint ready finish.
Brian
Brian,
I have used polycryllic before. It has advantages, mostly health related. No face mask required.
The issue with these water based materials is warps. No matter how I apply coverings, my balsa always warps using water. Especially the TE's...but I've also had whole panels bow from it. Not to belabor the obvious, with only two hands I can't work on both sides of a panel simultaneously. I don't use water based stuff until after the wood has been sealed with solvent based materials.....
Epoxy is much better regarding warps but will get heavy. I don't use epoxy for finishing; only for skinning. Nitrate dope is good, and is the lightest and thinnest so hanger rash is an issue. Klass Kote epoxy paint is similar to nitrate but also can get heavy if not really careful. I've found that every technique I have discussed has its strong points and they all have compromises.
The very lightest finish for wings, stabs, rudders is nitrate and lite silkspan or Japanese tisue. Lite silkspan and Jap tissue have their own tricks of application. The easiest way to work with these coverings is to hang them from a rafter or other frame and lightly spritz them with fine water spray. A mist only is needed to loosen and expand the fibers. Then the misted paper (never dripping wet...warps) is placed on the sealed surface and tacked on its perimeter only. Then the other surface is treated the same way.
The secured paper is allowed to fully dry. directly attached to each surface. Only after drying is the paper fully laid down with nitrate. See, as the paper dries, it shrinks and eliminates all creases/wrinkles. Also, there is no water left to warp my wings.
Jap tissue is superior to silkspan regarding strength and stiffness, but neither is as stiff as carbon veil. And none of these finishes is bullet proof because they are all very thin, thinner than wrinkle kotes (plastic films)....Good luck your learning curve. Technique isn't difficult (although it took some time to figure and work out lite silkspan) but is tedious.Lots of elbow grease required. But the painted finish is superior in my opinion.