(posted in the wrong place before)

Hey, i am building a Goldberg Ultimate 10 300 and currently the plan is to sheet and fiberglass the entire plane. Does anybody know how much weight it will add? I am looking at using either an OS FX.91 or an OS AX.95 currently leaning toward the AX .95 also i have the option of using either 3/4oz or 1/2oz fiberglass.

IMHO the best way to get a good guess at the weight would be to take a pc of wood 4"x4", measure how much it weighs, and then glass it, then reweigh it, subtract the first weight measurement and divide by 16 to get the weight per sq/in and then times it by the area you have to cover.

The resuts of fiberglassing can very greatly.

Wood prep to control epoxy absorbtion
Weight of cloth used
How well you control the application of the resin to minimize weight...

You can expect an average of double the weight of film covering, but it can be less or FAR more.

I've been intermittantly sanding off the excessive resin someone applied to a Sig Kougar for over 3 years... I've reduced the airframe weight by over 1 lb so far and haven't gotten to the wood...

Now what if instead of epoxy resin i used thin CA then finished with primer paint and clear? Ill be airbrushing the wing so the paint weight will be negligable maybe bordering 1/2 oz for the entire plane.

Originally Posted by Jwillecke

Now what if instead of epoxy resin i used thin CA then finished with primer paint and clear? Ill be airbrushing the wing so the paint weight will be negligable maybe bordering 1/2 oz for the entire plane.

you'll go broke buying CA and not save any weight. The fiberglass cloth and balsa under it will soak up CA like a sponge.

A couple of light spray coats of water based polyurethane (allow to dry 12 hours at least between coats) before applying the fiberglass and resin will prevent the balsa from soaking up as much resin and because its water based most of the weight of the polyurethane evaporates.

West Systems has a good finishing resin for keeping the weight down. I'll have to look up which resin/catalyst mix. Its a slow setting product...

There's a technique I haven't used yet where you apply microballoons with a sandable primer to fill the fiberglassed surface to make it smooth for painting.... one of the "local" (50 miles from me...) hobby shop owners and his son use this method to keep weight down for Pattern Aerobatics competition models, which have a strict weight limit.
I'll be picking thier brains about fiberglassing my 107 inch ME 262... Thier results are lighter than anything I have turned out.
I may have them spray the primer...