danc24

I just acquired a new ACI L88 hood. It looks great, but is hand-laid and you can see the underside is a little rough.












I really want to make it look like what 13611 did, filling and sanding with VPA. As well as filling in the outer seam. See this thread. and this one.





I've been reading Dub's excellent Lingenfelter's 1973 Corvette drag car which probably makes body work look easier than it really is but has motivated me to try this myself.

What prep-work should I do before applying the VPA? Keep in mind I have very limited experience with fiberglass or bodywork. Is it simply a matter of doing light sanding prep, spread a thin layer of VPA, sand smooth, repeat as needed? Any tips or gotchas I need to be aware of?

DUB

You basically have answered your own questions.

YES...making sure that you prep the surface for maximum adhesion of the VPA is what is MOST important. Because if a person is not going to spend time to make sure it sticks...then why do it at all.

So...I use a Roloc grinding disc ( 24 or 36 grit) and the grinder to go over the underside and I am looking to make sure that there is NO SHINE on any area of the hand laid fiberglass/resin that I missed. I did do some sandblasting in some of the really tight areas that were hard to grind on and get cleaned up.

Then I apply the VPA and get into that process...which can be quite fun.

SO...if you get into doing this and need any verbal advice or help or how to work with the VPA and not kill yourself when using it due to it gettign hard and you are sanding so much you feel your arms are going to fall off of you....PM me and I will get you my shop phone number so I can let you in on some stuff instead of me typing my fingers to the bone here on this thread.

For what it is worth..I did the same thing to a L-88 reproduction hood for a 1969 that had the air cleaner in the hood itself ( correct set-up).....And when I was done..you could wipe the underside with a damp paper towel to keep it clean. Your hood is different...but I had 40 hours in reworking the underside of that hood and it was really screwed up when I got it...and it was brand new brand new.

DUB

danc24

I've been making progress on my hood. I've filled in the perimeter, slowly filling, then sanding. I have it rough sanded to 80-grit.








For the hood sub-frame (is that what it's called?), should I add a thin layer of VPA to the strip that goes across the rear of the hood? You can see in the pic below where I've stopped. This part of the sub-frame is very flexible so I'm worried about cracking the filler. Is it even necessary?





For the interior of the frame, should I also add a thin layer of VPA (after prepping/sanding) or is it possible to get the existing fiberglass smooth enough without filling?

DUB

Generally all you need to do to the black understructure is to scuff it and get it dull and not apply any VPA.

For what iot is worth i am concerned in what I saw in tha last photo.




Where the VPA stops where oyu seined it....and the black begins.....I can see a shiny line where they meet...which tells me that the black gelcoat was not prepped prior to the VPA being applied on it.... and the VPA can pop off due to improper adhesion....in time.

And the way the VPA is not giving you smooth transition and it looks kinda jagged on the edge of the VPA...is also letting me know that the VPA is not sticking and breaking off in pieces when sanded.

If you hvae not seen this thread...go to POST #26. I explain and show it also in that thread.
http://www.corvetteforum.com/forums/...rag-car-2.html

DUB

danc24

Thanks Dub. I did scuff the black frame with 36-grit, but I see what you are saying. That particular section was where I first started and I may not have done a good enough prep job. I'll just grind out over the black frame and reapply.

Another beginner question:
What about the rest of the hood? I've seen some threads here that applied filler over the rough fiberglass and then sanded, but is that really necessary? Can I just sand the fiberglass smooth? Is there any advantage to applying filler first?

DUB

If you are wanting to smooth out the hand laid fiberglass on the underside of the hood it WILL require that you sand or lightly grind on it without taking off too much material...becasue it does need to be prepped well so the VPA or whatever filler you choose to use can be applied and blocked out to get the underside smooth.

IF you choose to do this..I know I have and when I am prepping the underside of the hood I make sure that any small areas that still show shiny fiberglas MUST be dulled out...because I cannot take the chance that the VPA or polyester primer lets loose and comes off in time. If the panel is NOT dull..then stuff can not stick to it as well as if it were dull or scuffed and no shine showing on teh surface.

I have applied gelcoat...and/or polyester primer and I not apply VPA due to how the underside of the hood felt when I ran my hand across it. Sometimes there will be a few area that I need to get correct with the VPA but the rest of it done with polyester primer...and I may have to apply the polyester primer twice to get the build I need to get is all smooth. The reason I am using polyester primer is that it builds up really good and much thicker than a vast majority of the 2K primers on the market.

DUB