Quote Originally Posted by Shadowrider View Post
We are not talking heat from the sun warming up the wings, we are talking heat from the engine. I would to be worried about the wings if the wings where seeing heats as hot as the engine cowl where seeing. I can assure you the fiberglass on my cowl has seen more than 200f when the cherry red turbo is inches away. I am just passing on info that others have warned me about using hysol to bond the naca scoop. A friend had his come loose after awhile of flying. Using the same stuff the part is made out to "bond" it is a better option I think. I would just take a couple strips of fiberglass and lay over the edges to insure it doesn't separate down the road like others have had. It would take a couple mins to do.
Hi Dustin,

Point taken, but I respectfully suggest that the mating surfaces may not have been cleaned and roughed up properly for a good bond the first time. Again, the Hysol has a higher temperature rating than polyester resins used with fiberglass. As far as "using the same stuff the part is made out of" being a better option goes, it is well known that epoxy resin in general is much stronger than polyester resin for fiberglass repair work. There is a wealth of info about that available on the web. Just one quote I found with a quick search -

"Polyester resin is excellent for fiberglass lay-up — building a boat, for example. ... As a general rule, the tensile strength of a polyester bond will be around 20 percent weaker than the same bond made with epoxy. That makes epoxy resin usually the best choice for fiberglass repair work."

It would be good to add strips of cloth, &/or rivets if desired, but there is no question that the epoxy will be stronger than polyester. Again, I submit that the original bonded surfaces may not have been prepared properly, and after failure I'm sure that there was some serious cleaning, sanding, etc. done to remove the epoxy, probably leaving a good surface for the polyester resin, or epoxy for that matter, to be used. I don't mean to beat a dead horse nor be disrespectful, but I don't want people to incorrectly think that Hysol 9460 is not a good adhesive to use for this purpose. Like so many things done in building an airplane, it must be done properly for best results.