Question on shrinkage

slammed57

Newbie
After blasting the cab I ran 80 grit over it and sealed in epoxy (spi of course) then did filler work over the epoxy and finished it in 180 , some areas in 150 and then put 2 more coats of epoxy on top of the filler . Iam getting ready to spray the cab in polyester . but I just was reading somewhere where that I may have some shrinking issues due to epoxy over filler with sanding scratches. its been about 3 weeks now and I pushed it in and out of the garage to bake in the sun hoping to help cycle any shrinking. I was looking on your thoughts on this. Iam tryin to do the best I can and now thinking I screwed up due to misreading somethin .
 

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Has it been in epoxy for 3 weeks? In and out of the sun? It needs to be sanded with 180 and reshot with epoxy before polyester. 180, 1 coat epoxy, 48hrs.+, then polyester.
from my understanding I thought you just need to scuff it with a red pad and them apply the poly? correct me if Iam wrong pls
 
from my understanding I thought you just need to scuff it with a red pad and them apply the poly? correct me if Iam wrong pls

For maximum adhesion you need to do what TK said.

From the Tech Manual:
"After 7 days, the epoxy should be sanded with 180 grit and recoated with
epoxy for best adhesion."
 
Epoxy over and under filler is best practice. Nine times out of ten shrinkage comes from rushing some part of the process, and it is almost always from abusing the 2K step. 1) Not taking the time to finish the filler with 180, 2) not allowing enough flash time in between coats, 3) not spraying the first coat of 2K wet enough, causing the primer to "bridge" over the scratches instead of filling them, and 4) not allowing the 2K to fully cure before sanding and painting. Be careful where you get information, and if you are not sure, ask on this forum, or call Barry directly.
 
Also what you are hearing could be true, as there are a 100 ways to make epoxy and not all are good.
With SPI four coats and no flash (not recommended), after 4 hours left over shrinkage you cannot see with naked eye
 
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