huminski

My Feedback: (23)

So I'm considering fiberglassing and painting the wings and tail on the byron extra 300S I'm working on.

The fuselage, cowl and wheelpants are already fiberglass. the wings, and tail (except vertical stabilizer) are foam cored and balsa sheeted.

How much weight would I be adding, roughly, if I fiberglased the wings and tail and painted them, as opposed to covering them with heat shrink film?

It's a 64" wing.

Live Wire

The first thing to take into mind is how do you want it to fly, then ease of repairs, then detail. You are going to have more weight with glass and a lot more work. And engine change out for larger engine for weight.[:@] Now War birds are a different animal.
Larry K

Deadeye

On my TF Cessna, from bare wood to clear coated added 11 ounces. I used 3/4 cloth, and water based polyurethane, not epoxy.

R8893

My Feedback: (20)

I wanted to quantify the answer to your question so I made up a couple test pieces a while back. Disclaimer: your results will vary. My wood, my technique, my elbow grease (most significant factor), my electronic balance, my arithmetic.
Piece of Monocoat: 2.64 ounces per square yard
Balsa glassed with 3/4 oz cloth and Zap finishing epoxy, sanded. Average of two separate pieces: 1.90 ounces per sq yard added weight.
After second coat of resin was sanded, both pieces weighed less than before.
Two coats of epoxy primer sanded between each. Final weight is less than balsa and cloth step 1 by a couple tenths of a gram.
Have not painted yet, but at this point I have sanded through 400 wet, and the surface is like the proverbial baby's bum. I don't intend to mix the epoxy paint I use just for this experimentwill have to wait until the next model is ready for paint to see the final total weight gain.
I suspect that working on the curved surfaces of a model results in more weight buildup than what I have on these flat pieces.
So when starting with a solid balsa surface, glass and paint does not need to be significantly heavier than film. Of course the film finish will weigh significantly less over an open structure.
Chuck

huminski

My Feedback: (23)

That's not too bad then, considering I'm only fiberglassing the wings and the horizontal tail surfaces, plus the rudder. Maybe I can get by under 8oz which would not impact the all up weight all that much then. Still deciding whether or not to do it. I like the polyurethane idea too, how does it hold up when compared to resin?

huminski

My Feedback: (23)

R8893, so you're saying that properly applied fiberglass ended up weighing less than monokote??

Gray Beard

My Feedback: (-1)

I glassed my Extra with 1/2oz glass and a sanding type of Poly-U, I mixed the stuff 50/50 with baby powder to fill the weave the last two coats, almost everything sands off so there isn't much weight added at all. I painted with Klass Kote mixed about 50/50 with thinner. The plane came in at the same weight as my other Extra so it really didn't add and weight.

FallDownGoBoom

My Feedback: (1)

I wouldn't go so far as to completely state that a fiberglass based finish is always going to be lighter than plastic film, but doing it properly shouldn't result in a significant weight gain. Where you can pick up weight is leaving too much resin on the surface, not sanding off enough of the primer, and putting on heavier coats of paint than necessary. The real payoff of using fiberglass is the seamless painted finish that will hold up to daily use. But the prime/sand/redo cycle takes more work to than a film based covering.

As for the toughness difference between epoxy and WPU, I think the epoxy finish is slightly tougher. But neither will totally prevent hangar rash.

R8893

My Feedback: (20)

Steve H.,
Yes, it is less than monocoat at this stage without the pigmented paint. I don't have a figure for the paint yet, but I have been able to paint my models with only one coat of Klass Kote.

A long time ago an excellent C/L stunt flyer made this comment about finishing: "Your objective is not to fill in the low spots; each coat of dope brings out the high spots and you sand them off." NOt exactly applicable to a glass and epoxy finish, but that mind set seems to help keep the weight down.
Chuck