GSJames

I REALLY hate film coverings for race plane wings. The 424/Q25 rules prohibit molded wings and tails, and covering the balsa sheeted wing with a "wet" glass layup really adds the weight. But what about "sheeting the sheeting"? I read the "paint the mylar" thread beginning to end and it's a great idea, but too hard for me. ACP sells 12" x 48" x 0.005" fiberglass sheets made from pre-preg. I bought one for use as skin hinge material. It's pretty light, and flexible, and SMOOTH. Has anyone ever tried to sheet the balsa skins with this pre-cured material? The technique would be just about the same as sheeting the foam core with the balsa in the first place and would provide a SMOOTH, no-filler-required, paintable surface for the wing. It's kinda expensive, but I think it would work well and would stick better than mylar skins

DMyer

My Feedback: (2)

The real key to building a lightweight glassed wing is controlling the weight of the balsa sheeting and the amount of glue used to attach the skins and reinforcing carbon/glass. The key item used to control the weight of everything going in, including glue and wood weights, is a good quality gram scale. I am not familiar with the material you are contemplating laminating/bagging onto the sheeted wing, however, I am familar with building high quality balsa sheeted/glassed/painted quickie 500 wings that weight 1 pound with servo. Just takes a little patience and attention to details. Good luck.


Dan

GSJames

I didn't explain the concept very well.

The idea would be to "glass" the balsa sheeted, foam-core wing with commercially available, pre-cured 0.005" glass sheets adhered with a small, controlled amount of resin as opposed to "glassing" the balsa sheeted wing with the traditional wet layup over the balsa sheeting. The pre-cured sheets are made from pre-preg glass and cured on a smooth surface, thus they are much lighter and smoother than a traditional wet layup due to less resin and the elimination of the need to use primer-filler to fill in the weave prior to painting. This "should" result in a wing that approaches molded 428-quality but is legal for 424 / Q25.

Has anyone ever tried this?

daven

My Feedback: (1)

I have never tried it, but it sounds plausable. I would assume you would attach it to the wood first, and then sheet the foam with the wood/laminate? Or maybe try to do it in the bag all in one step??

Give it a shot and let us know??

I think it may end up heavier than just glassing the wing with 3/4 oz, but maybe not??

Scorpion Racing

I use the .005 for the skin hinges too, but I never tried it as a wing covering! The thing I think will be hard to control is the amount of resin the balsa skin will absorb. The lighter contest balsa will absorb more resin, but the harder balsa weights more. You may want to experiment with your resin and some scrap balsa of different weights to see which works best and weighs less when finished. I build my wings and then cover with .5 oz cloth and squeegee it off with a credit card. The credit card pressure while you squeegee it presses the cloth down firmly, as well as removes excess resin. I cover a quickie wing with 15ml (1 tablespoon) of resin per side (30ml total) and still have excess from squeegeeing. You can then do the painted Mylar or whatever method you want to finish it with and top coat it with some more resin or clear paint. Pay very close attention to how much paint you use; you can use a lot less than you think to get a good finish. My wings come out right around 16oz, give or take an oz. Like Dan said, be very careful with all the components in the wing, and pay attention to weight and wood selection. I have found MGS or West give a much stiffer wing, and tend not to yellow as fast if you go for a clear look.

I hope it works out if you do try it, the only issue might be the sheet trying to separate from the wing. I will keep watching to se your out come. Good luck!

djlyon

I may try that myself. It may make the whole process of building a foam core wing faster. I do use the material to make my skin hinges ala Daven. But I must say I have never had a wet glassed wing come out heavier than a monokote wing.

Denis

diggs_74

I think the only problem you will run into is at the LE of the wing.. I will be hard to get a good bond there even in the vacuum bag.. You may have to work that by hand after the skin is on.. Just a thought.

Ed Smith

There is probably a very good reason that not too many wings are constructed this way. I have no idea what the cost would be for pre-finished skins. I have never had a problem with the traditional cloth/peel ply/breather cloth/vacuum bag method. To ensure that the finished skin is tight on to the wing surface, vacuum bag pressure would seem essential. I can forsee a danger of airbubbles under the skin as the glue/resin would have nowhere to leak out. Added to the aforementioned leading edge issue I do not see any advantages.

The closest I came to this type of construction was to sandwich the wet glassed wing with .015 mylar before placing in the bag. The leading edge and wing tips needed fixing and sure enough some air was trapped. The shiny gloss finish was very pleasing however.

Ed S

GSJames

That's what got me thinking about the idea. I just got some 0.010 and 0.005 glass for skin hinges and when I picked it up, and saw how flexible and smooth it was, it occurred to me that the 0.005 might be a substitute for a wet glass layup.

I weighed the stuff and it weighs 0.15579 gm/sq.in. Thus a 500 sq.in. wing (1000 sq.in of material) would weigh 155.8 gms or 5.495 oz. plus the adhesive. Since the glass is already cured, the glass would not absorb any additional resin. To adhere it to the balsa skin the glass would be "scuff sanded" on the bottom side and the epoxy adhesive applied to it and scraped thin. The balsa wouldn't absorb much resin because there wouldn't be any extra. It would be easy to control the amount of adhesive resin.

You all are right, the leading edge would be the tricky part.

I'm just making this up as I go along. Trying to "think outside the box" as it were and come up with a better method to do things. My original question was whether anyone had ever tried it, but from the feedback,I suspect that it has not. I MAY give it a try. If I do, I'll keep accurate notes and weights and let you know. If anyone else want's to beat me to the punch please go ahead and give it a try.

smacfe

This was tried a number of years ago, and was marketed by a company called GlasSkin. They actually did away with the balsa altogether and simply sheeted the foam with the glass skins, wrapping them around the l.e. This produed a really nice wing which was used pretty extensively in pattern airplanes and to a lesser extent in racers. I do remember a Miss Dara formula 1 done by them. The wings were somewhat heavy, susceptabe to hangar rash and of course, expensive. In those days, the glass skins were made with polyester resins instead of the epoxy resins used today, so revisiting the technique is probably warranted. I have ordered the glass skins and have been looking for the time to try the experiment but havn't gotten around to it yet. I would be interested to hear how yours turns out. Another technique that was simillar was the use of 1/64th plywood over the foam. This produced beautiful and strong wings that also were a bit heavy for a 3 1/2 pound airplane but might work now that the weight has been increased to 3.75 lbs.
Scott

freeair

if you dont like film covering have you thought of using the tissue / dope method and them spray paint over ? this is what we did many years ago before the word IRON ON FILM was discovered, rather than fill up all the balsa grain with heavy fillers etc we just applied a light layer of tissue paper with the good old Dope and then painted over. look at the foam / balsa sheeted wings which are very strong [ if done right ] add a layer of light weight tissue to the wing with dope as the glueing agent [ all grains gone ] give a light coat of sealer and finish off with a couple of light coats of the finsh paint. this will be alot lighter than using glass over.

djlyon

2 or 3 years ago I built a quickie that way to see how light I could get a 428 strong quickie (old rules 3.5lbs). It came out 3.2lbs with an ABC Nelson and bigger than necessary servos. I wouldn't do it again, there's no point anymore. I covered the fus with black silk and the wings and tail with 0.2oz carbon tissue and trimmed the plane with colored jap tissue all done with dope. Looked neat in an ugly sort of way. When it exploded in a midair going around 2 it looked like any other quickie.

Denis

GSJames

Yes, thanks, in fact I did the fuselage of my new Buckshot that way. I used "000" silkspan and I think I should have used a heavier grade since some grain was still visible. Perhaps "00" or "0" would be better. I tried both dope and thinned epoxy laminating resin as an adhesive (not on the same part). The dope worked better. I plan to do the Buckshot wing the same way, but am looking forward to building subsequent racers using different techniques.

Thanks to all for the suggestions / background.

Duane-RCU

My Feedback: (5)

Hey Gary, the Viper I raced Sunday has a glassed fuse. It was in need of repair, and after I fixed it I used some watered down craft paint my wife has to color the wood, then used
.75 cloth on it. I did one panel at a time, put the cloth on waxed paper (mylar would be better!) got most of the epoxy off it before I put it on. It is smooth, and looks pretty good, but I guess I could have made it look better, but you know the life span of these things.... I don't remember exactly, but it does weigh less than with monocote, and it doesn't peel or wrinkle!

daven

My Feedback: (1)

I was thinking about the leading edge. What if you taped two pieces of the .005 together on the long edge and wrapped it around the front of the wing like a book?? Open the book to apply your glue, then wrap the wing, pull tight at the TE and tape the outside holding the LE snug at the front and put in a vacumn bag at low pressure around 5-6".

GSJames

That sounds like a promising idea

freeair

with the chinese paper we use either light / medium / heavy grade, even the heavy grade is very light for this type of model. no need to use silkspan stuff .