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I'm in the process of attaching the lift strut attach brackets to the spars. I have the spars and the brackets sprayed with zinc primer. Should I rough sand both areas bare where the brackets contact the spars? I know I have to glue but I'm wondering if the painted surfaces will weaken the bond.
Bob.
Refer to the manual. I believe it states to add some glass beads to the adhesive befor attaching the steel brackets to the spars and using a boat load of SS riverts. (the Classic IV manual did).
So If the frame was powder coated, so were the steel brackets.
I think the idea of the glass beads is too prevent the steel contacting the aluminum spars, causing rust (inconpatible metals contact)
So when you think of it, the steel bracket could be sanded bare steel on that mating face, if you are suspiciouse of the adhesive quality of the primer you sprayed.
And If I remember correctly, DO NOT sand the aluminum spar. This is detrimental to the integrity of the aluminum (could be the cause of stress cracks) Like it stated, do not use a pencil to mark the spars but use a ink marker.
Do you have a bag of the micro glass beads as well as the flox with the kit?
it's called electrolysis when you have 2 unlike metal materials meeting and they corrode,..with exception ..stainless ,..that is why the rivets are stainless.
On page W-B-11 STEP (29) my Kitfox 4 manual says. Mix enough struc. adhesive and filler to coat the inner surfaces of the strut attach brackets. The primary purpose of the epoxy here is to add a barrier between the aluminum spars and the steel brackets, preventing dissimiilar metal corrosion. If the attach brackets are not powder coated they should be primed with epoxy zinc chromate. There you have it.... from the book. Jim Chuk