[misteryu]

Posted this on other forums to generate as much advice as possible:

Hello,

I have a fiberglass hood that was rough to begin with. From the top to the bottom of the hood it has a gradual curve down to the headlights. Seems like whatever block i use or make, it will put a flat spot somewhere. I have used alot of filler to fill in the huge dips it had and 2k primered it. After i was done there were still waves in areas that are too deep to fill with more 2k so i used some Evercoat glaze. Well now it's basically all skim coated but i can still feel small waves. I just can't get the filler work perfect. I was planning on purchasing that AFS sander, but also looked into the polyester filler primer.

So my question is, should i try to use that AFS sander first and get it as straight as possible, or would it be better to use the polyester spray filler over the whole hood to get a uniform surface? Is it ok to spray poly. fill primer over alot of filler?? Thanks!

Chris

[BarryK]

Your getting into a pack of problems here.
First a hood not only being a flat surface and exposed to full sunlight it also is getting heated up by the engine.
So with all this in mind, you have fiberglass expanding and contracting at one rate and polyester and 2K primer at another.
If you dump polyester primer over the 2K at this point its just not going to last past late spring when the temp gets back up there.

At this point start blocking until most of the 2K is off than if you want go to the polyester primer.
Don't just strip the 2K off, block and its OK to leave some but hopefully when your done blocking the hood will straighten itself out a bit.

[misteryu]

Barry,

Thanks for responding!

I stated that i had glaze coat over the entire hood basically so i wouldn't be applying the polyester over the 2k. I was told that spraying polyester over a panel that had extensive filler work over the whole panel was the way to go. Then after i block , to 2k primer it and bc/cc

Thanks

[BarryK]

Your right,
Thats the best way.

[misteryu]

barry,

What would actually happen if i applied the poly. primer over the 2k? You said it wouldnt last till next spring? Thanks

Chris

[willys36@aol.com]

Maybe it all sounds worse that it is. How thick is the thickest part of your fill sandwich? If it is on the order of 0.01", should be no problem, the various layer will likely stretch and contract together. If it is +1/8", then the different composition of K2 vs polyester products may cause bubbles, delamination, or peeling due to differential thermal expansion and contraction.

[BarryK]

Willy, has a point, I think you made it sound worse in your first question then it really was.
To answer your question as long as the 2K is cured the polyester primer will go over no problem.

On a hood you want to avoid a lot of different products as well as a very high build and this is most true on fiberglass / SMC.

My statement was based on the assumption you tried to block with glaze, than tried to fill with 2K and now wanted to fill more with Polyester. I had visions of a cake 2 inches thick.

[willys36@aol.com]

Originally posted by BarryK
I had visions of a cake 2 inches thick.

So did I at first but since he started out w/ a fiberglass part, that usually means a bunch of shallow but noticeable waves that don't take much over a gallon of bondo to fill!