Can we talk about the old way we used to treat composite patches

For years I thought a quick sand and a fresh layer of epoxy was fine for small delaminations... then I saw a patch I did on a Cessna 172's winglet fail after about 18 months. The shop that fixed it showed me the core sample under a borescope... moisture had crept in from the edges because I didn't extend the dry-out zone far enough past the visible damage. Now I always go a full two inches past the last sign of any issue and use a proper heat blanket. Anyone else have a specific rule they changed after seeing a long-term failure?

2 comments

2 Comments

wright.michael10d ago

Man, that hits home. I used to be so sure a tight sand and patch was enough for small stuff, especially on rudders and fairings. Then I watched a repair on a Cherokee's elevator slowly turn into a sponge over three years, all from a tiny edge I didn't seal right. Seeing the wet core spread that far on an ultrasound changed my whole process. Now I treat every delam like it's twice as big as it looks.

jennifer35810d ago

Wasn't there a service bulletin from Piper a while back that basically said the same thing? I remember reading it stressed that any repair zone needs a big, dry border or you'll trap moisture against the good core. It made me start using a moisture meter on every single job now, even for tiny fixes.