That time I stopped using primer on composite patches and it held better

I work on Gulfstreams out of Savannah, and we had this recurring issue with composite fairings delaminating after repairs. The standard manual says to use primer before applying the patch, but I noticed it was flaking off after a few months. So I tried skipping the primer on one repair back in March, just cleaned the surface with acetone and sanded it rough. The patch bonded straight to the base layer. Eight months later that same fairing is still solid with zero signs of separation. My lead mechanic saw it and gave me this look like I was crazy. He checked the bond line and said it actually looked cleaner than the primered ones. Now I do it on non-structural stuff where the manual allows discretion. Has anyone else messed with skipping steps that supposedly matter? I want to know if I'm just getting lucky or if primer is overrated for certain layups.

2 comments

2 Comments

kaiharris2d ago

Wait, you skipped primer and it held better? That's wild.

julia_hayes2d ago

My dad used to swear by always doing the prep work for everything, and then one day he just painted a fence without sanding it first and it lasted three winters longer than the other one. Makes you wonder how many "rules" we follow without thinking.