hardra

I have heard of a technique for sheeting foam wings that involves spraying the foam with cyano-accrylate and then pressing the sheeting into place. Apparently this give the lightest possibly bond because the foam actually melts a little and soaks up into the balsa, so the builder can use less adhesive than would be needed to actually glue the balsa in place.

I think I read a post about it on this forum, but I have been searching all night and can’t find it again.

Has anyone ever heard of this technique and can anyone direct me towards information regarding it?

Thanks anyway,

Hardra

TexasAirBoss

My Feedback: (22)

Sounds mighty risky to me. You better try it on a piece of scrap.

I use contact cement, you know that stuff you brush on the wood and the wing , let dry. Touch the two together and they are bonded for ever.

I have heard guys say they prefer to use glue, like Epoxy or white glue and simply glue the sheeting on.

EASYTIGER

My Feedback: (119)

Don't beleive everything you read on the internet...spraying CA onto foam cores is a BAD idea. Go try putting CA onto some foam, it melts more than "a little!"

hardra

Thanks for your response.

I used ProBond on my last plane, and it is really strong but kind of heavy. I am trying to build a very lightweight plane, but I am not quite ready for built-up wings, so I am looking for other ways to cut weight. I read about this technique, and want to make sure I remember correctly before I start testing.

Some people say the contact cement delaminates in high heat, some say it is fine, but I would rather stick with ProBond if I can’t find a better way.

People suggest a thinner adhesive layer and more clamping weight, so if I can’t find the article on melting the sheeting on, it is ProBond and sand bags, I guess. The idea of low-weight glueless bonding intrigues me, though, so I am still looking.

EASYTIGER

My Feedback: (119)

Less glue is the ticket, you are on the right track.
Contact cement may be lighter.
I use only epoxy, it works for me, and you really only need the tiniest amount.
Think about cutting some lightening holes in the cores to save some weight.
And giving yourself a fixed amount of glue in a cup to do the job. Like just an ounce, and you NEED to cover everyhting with just that one ounce, that makes you spread it thin.
The CA thing, well...you read some crazy stuff on these sites, it's about 50% BS, people will tell you to dip your canopy in brake fluid to clean it, or tell you to CA your foam cores into place!

SST

My Feedback: (2)

Believe me, Polyurethane glue can be used and kept light. I made some balsa ply by spreading Elmers Ultimate with a PUTTY KNIFE! I used just enough to dampen the surface of the wood, and scraped the excess off with the straitedged blade, sprayed water directly onto the glued surface and set my crossgrain stock in place and weighed it down. Moisture is the key to maximum expansion of PU glue, and the more it expands, the less you need and the better penetration you get. I've pretty much quit using epoxy on any high-stress joint I can clamp.

BadBill

My Feedback: (89)

There was a technique that one of the mags had an article on many moons ago, about covering balsa or foam with fiberglass cloth and CA. They then scraped the surface with a razor blade to finish it?? I'm sure my recollection may be a bit off here, but I think that was basically it.

Easytiger, c'mon man you haven't heard of foam safe CA? Long as you've been around?? LOL! [&:]

LuckyArmpit

I've covered foam with Econokote covering. To get it to adhere well, spray the foam with 3M 77 spray. But, spray it from about 2 feet.
This will allow the acetone chemicals to evaporate off. If you spray it too close, the foam will melt slightly. True for foam thats made from EPS. EPP foam is different in that you can spray the crap out of it and it aint gonna melt. I suppose you could try this method with the balsa sheeting.

Dave...