JohnF

What is the best method, other than fiberglassing, to seal sheet balsa?

abufletcher

For what purpose? To make it fuel-proof? To make it (more or less) dent proof? It this "wood" area that will be left uncovered and unpainted on the model (for example the panels on a DIII)?

It takes an awful lot of work to make balsa wood look like anything other than balsa wood.

JohnF

Don, It just needs to look like painted ply wood. The glassing would add some strength and hardness to the balsa but I don't think it's worth the extra weight. Polycrylic will work just as well I think and not be as heavy?

abufletcher

I'd go with whatever these guys (the "two Daves") are using:

http://www.rcuniverse.com/forum/m_67..._7/key_/tm.htm

JohnF

Don, No doubt DJ is the man when it comes to finishing an Albatros but I am not staining the wood. It will be painted. So, I just am looking for a lite way to make it a little stronger and ding resistant. Someone else suggested using silk cloth and resin but again I think there is a weight penalty with that method. Have you ever tried just spreading thinned epoxy resin over balsa sheet without any cloth?

TFF

Most people use too much epoxy when they glass. A 1/4 scale plane fuse. should only use about one oz. of epoxy. 3/4 oz cloth is paper thin and when done right can be equal to weight as Monokote. Using the Poly with the glass can half the weight of the epoxy way and easy and less messy, but it is about 70% as hard. All will be more than 100% tougher than just painting balsa.

jtisch

I have to agree. The glass cloth, silk or silkspan is the lightest part. Instead of resin you can use polyurethane or even dope if weight is a concern,but if you go easy with the resin the weight gain shouldn't be too bad. Putting resin on bare balsa might actually add MORE weight.

J

JohnF

Thanks guy's I appreciate your feed back. I'll probably stick to the lite glass cloth I have with resin.

BobH

My Feedback: (2)

John, if you don't add light weight cloth or tissue or something similar the wood grain will open up. Even after it's painted.

JohnF

Hi Bob, Well, I know that Dave Johnson does not use any fabric at all on his Alb. fuselage and he never has that problem. He just stains it. I don't think he even puts a clear coat on it. All depends on the grade of balsa I believe.

squeakalong

My Feedback: (8)

Well....then just ask Dave Johnson HOW he does his finish...and have at it

And then...share the "secret" with the rest of us

Soft landings.

Joe

Sethhunter

I think it's important to decide what role the finish plays in (how much you need it to) strengthening the structure. Even a light cloth and resin adds significantly to the strength of the fuselage, etc. (I glassed the fuse, stab and fin on my Pfalz DIII and DXV, which were plywood on the originals). I factor the finish into deciding the weight/strength of the structure underneath - lighter/thinner balsa under glass, than say, fabric finishes. That helps offset some of the weight. I especially build light in the tail when I plan to glass. That is, I think of the finish as more than a seal, but part of the structure. I concur with comments above that the cloth weight is minimal, and even the resin weight can be kept pretty low. I think I used about 1.5 oz of resin on the fuse/tail of my Pfalz DXV (1/4 scale) and .7 oz cloth. I thin the resin about 10% with alchohol, and squeegee it on with a stiff plastic card, then put the glass down and let the cloth wick-up the resin from the balsa. After sanding etc. I squeegee another coat of resin, putting down another 1 oz or so. The tail was sheeted with 1/16 balsa, and the fuse with 3/32. 1/4 sq balsa stringers underneath. On fabric covered planes, I generally up the balsa thickness by a 32nd. Obviously flat versus round fuse sections make a difference in the strength /finish tradeoffs.

BobH

My Feedback: (2)

John if Dave's Albi is any thing like the Proctor Albi then the outer skin is thin ply and not balsa. With thin ply all you need to do is stain and seal it with a clear. The full Scale Albi was cleared over and since Dave competes with his I'd guess his is per the full scale plane. Wood will stay absorbent unless sealed. At least that's what I was taught. Let us know what you find out.

JohnF

Okay guy's, thanks for all the feed back. Seth, the tail is as light as possible I think. I'll probably stick with the lite fiberglass cloth I have and resin.

JohnF

Bob, Dave uses balsa to sheet his Alb. I know this for a fact. Just not sure if he uses anything on top of the stain. Maybe he'll chime in if he reads this.