hey.i know this is a trad board but i'm workin on a porshe 944 that has hairline cracks in the fiberglass sunroof and i have never worked with fiberglass before so any suggestions as how to prep it to paint would be much appreciated thanks heather
sand all the cracks out and repair the spot, smooth out and prime and paint like normal. If ya don't get the cracks out they can only get worse.
There's a product on the market called "FeatherFill" (at least there used to be), that is an epoxy finish that was developed for early Corvettes. To prep the surface you sand with 36 grit, yes 36 grit, sandpaper and spray the FeatherFill on til it covers the sanded area. This is a two-part product that cures chemically. It is thick and hard as a rock. Looks like concrete when it dries but it will hold out all further cracking when applied correctly. Check with your autobody supplier if they don't have this product I'm sure they will have another just like it...
Switchblade and Charlieled are right on the money. Featherfill is a Polyester resin based primer (not epoxy) which is the same as fiberglass resin. It is made by the Evercoat or Fiberglass Evercoat company (they also make the Rage body filler that is very popular). This type of primer surfacer or filler is the reccommended material to use on bare fiberglass panels. There are other similar products made by other companies that are based with polyester or fiberglass resin and they use a hardner (usually liquid MEK peroxide) and need to be used in temperatures above 64 degrees F. but, probably not over 90 degrees F. The cracks are probably in the top layer or gelcoat of the panel. It's probably easier to do this right if the sunroof panel is out of the car. All the paint should be removed for the best results, and using 36 grit to take off the layer of gelcoat is a good idea but being careful not to gouge the panel. Three good coats of the primer filler should be good. It sands hard! Block flat first with 180 grit then 240 or 320 grit. Finish with 400 grit and she should be ready for any paint system. Check the directions, but I think on Featherfill wet sanding is NOT reccommended. overspray
excellent! thanks to all of you...i'll check out the featherfill deal at the paint store tomorrow ...wow 36 grit... makes me cringe
I think my sunroof is made of metal....just went outside with my trusty Acme do-it-yourself magnet to see if it's steel.........nope- but I think mine may be aluminum. Might try a foreign salvage yard to see if you can score an aluminum one. Here's my winter beater 944.
Yea the 36 grit make me cringe too. 36 or 40 is fine for v-ing out small cracks but 80 grit to rough up the surrounding area is what I would recommend. The small cracks in the gell coat need to be repaired. Just spraying fetherfill or any other polyester primer over them will cover them up for a very short period of time but they will show back up. Without seeing the actuall damaged area you are talking about it's really hard to give proper advise. Many different things happen with fiberglass. You may have a stressed area the actually needs to be repaired. You know.....like why did it crack! I think you need to have someone that has some experiance with glass repair at least look at it and then give you some advise. I fix fiberglass all the time Heather, let me know if I can help any further.
Roadstar is right. If the gelcoat is just age cracked and you remove it the featherfill will probably work. But if Large Lucy has parked her fanny on the top and stress cracked the panel itself, it should be repaired by grinding the area down and "veeing" out the cracks. Then repairing the area with fiberglass matt and resin will be in order. overspray
Double check and make sure that it is fiberglass. I think that the Glasurit/Sikkens paint (or whoever made it) of that era was lousy. The problem was that stuff wouldn't adhere properly to the primer, and would shrink and crack. Does it look a little like a dry lake bed? If it is fiberglass, the gel coat may be OK. You may be able to strip the paint and primer and reshoot it.
cool pic rocky..i'll throw one up when i'm done..didn't you give me some poncho advice awhile back? howdy roadstar...i don't think their stress cracks cause they don't go deep enough..their more toward the clear rather than down in the paint..but i'll just run by the shop and you can check it out ..haha..i'll be there about 10 in the morning...go ahead put the coffee on overspray you just creeped me out with that large lucy remark..i think i need to go wash my hands now.haha well deuce, most of the top surfaces had hairline cracks and when i took a grinder to the hood i had about 5 layers show up so i'm thinking bad mojo b/t paint layers and/or cheap clear. but it looks like the sunroof hasn't been repainted so i'm betting on your hypothesis about the primer and on a second look the sunroof is definetly not metal but now i'm a bit shaky on my fiberglass diagnosis..could it be just a plastic composite and how could i tell? and how to rememdy crack sitution ...sorry for the dumbness i've never worked with plastic parts before except bumpers
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