bonded-only spanwise wingtip rib

prkaye · #1 04-20-2009, 06:35 PM

For the wingtip rib that runs spanwise, the plans have you bond it first and then rivet it with 3/32 rivets. These rivets will have to be set with a rivet gun, because it's too deep for a squeezer to reach. I'm not crazy about smashing that thin fiberglass tip with a rivet gun, so I'm thinking about just relying on the epoxy to hold it in place. I would think with a sufficient amount of epoxy this would be more than strong enough. Thoughts?

BlackRV7 · #2 04-20-2009, 07:13 PM

Phil, if you are going to bond it, get some cotton flox and go ahead and drill some holes in the rib flange for the flox to flow through and have at it. The holes add some strength to the bond. Be sure and scuff the rib flange up nicely. The people in the plastic airplane world do it all the time.

Either that or Van's has soft rivets just for fiberglass.....

andrew phillips · #3 04-21-2009, 05:58 AM

set pop rivets just below the surface then cover later with microballoon mix or rage filler. Then you have rivets but you don't see them.

Dave Cole · #4 04-21-2009, 06:19 AM

If you bond the rib in place with an epoxy and cotton flox mixture, the result will be significantly stronger than plain epoxy with rivits. I would leave the rivits out provided you can devise a way to hold the rib in place while the epoxy cures.

f1rocket · #5 04-21-2009, 06:24 AM

There are a number of ways to attach it, some are more work than others. My suggestion is to Proseal it in and leave it at that. I don't think drilling holes are necessary, but they certainly won't hurt anything either. They do give you some extra grip but with Proseal, I don't think it's needed. Flox by itself is a weaker bond IMO without glass over the top of it.

Personally, I try not to pop rivet anything if I can help it but that's just a personal preference. When you bury pop rivets underneath Bondo, slurry, etc, they tend to vibrate and eventually crack through your paint. They just are not as tight as a solid rivet and I prefer to avoid their use if I can get away with it.

prkaye · #6 04-21-2009, 08:18 AM

Thanks guys. I do have a bag of cotton flock, so I'll use this with epoxy, and drill the holes in the rib as recommended.
I've actually become a huge fan of fiberglass... so versatile!

vonjet · #7 04-21-2009, 11:15 AM

I'd maybe look at using Hysol. Not sure about the bond quality with metal but its a heck of a lot better for fiberglass bonds. We bond all our fiberglass skins together with it in the Lancair and its incredible stuff. And you dont want to use excess epoxy for anything. Try and get your bond line thin but not to thin. Drilling holes in the rib is a good idea for the glue to flow out of and help grip.
Another great product for bonding disimilar materings is made by West Systems. Its called Gflex 650. Its strong and a little flexible.
"Toughness and Flexibility G/flex has been toughened. This gives G/flex the ability to make structural bonds that can absorb the stresses of expansion, contraction, shock, and vibration. G/flex is resilient and impact resistant. With a modulus of elasticity of 150,000 psi (WEST SYSTEM 105 Resin/205 Hardener has a modulus of elasticity of 450,000 psi), G/flex is more flexible and can deflect further than WEST SYSTEM 105/205, while being much stiffer than typical adhesive sealants."

Bryan