Ok, I recently bought a fiberglass trunklid (today actually) and when I opened the package...I noticed a crack on the underside of the lid. It is about 5 inches long and is located on a part of the underside bracing....meaning there is a hollow cavity between the crack and the bottom side of the actual fiberglass that you see on the outside. Sorry, I hope that makes sense to you!!! So what is the proper way to repair this crack?
Thanks
Ken

laminating epoxy resin ( no cheap polyester or vinylester resin or it may not hold/stick for long).. buy some fiberglass cloth 6oz to 8 oz weight. HomeDepot sells fiberglass cloth in a small package, but it's all folded up so it's really a lot of cloth in there. Pick up some cheap .60 cent throw away brushes from there too.. about 4 of them to be safe.

Sand the cracked area down real good to remove the gel coat finish ( wear a respirator while sanding). Sand the gel coat down at least one inch all the way around the crack. Now clean it with acetone and a clean rag. let it sit for 8 hours after that in a dust free area. acetone cleans the sanding dust off and creates a clean surface to bond to, problem is it can soften up the resin in the trunk or hood in that area.. so waiting 8 hours allows the resin to harden back up before you proceed.

Mix up your laminating resin in a cup ( EXACT RATIO is critical with epoxy mixing) mix it thouroughly for at least 3 minutes in a plastic cup. Don't use waxed paper cups for epoxy. cut 3 strips of fiberglass the size of the repair patch area.. no excess. now wet with your brush the patch area on the trunk/hood. lay a piece of fiberglass cloth ( not mat ) over the area and use your brush to wet out that piece of f/g...it will turn clear as it is wetted out properly. let that sit for 3-4 hours.. do the same with another layer of fiberglass cloth, wait 3-4 hours more then do your last , 3rd layer. once it is all cured ( generally wait 24-48 hrs with epoxy. sand it smooth around the edges of the patch. If you need to use a filler to smooth it perfect then use more epoxy, then sand smooth until desired look is achieved. Primer and paint after 4 days.

You can buy a 1.5 epoxy laminating kit from www.jgreer.com for around $20. Epoxy ain't cheap but it's much better than polyester resin. If you want to try using polyester resin you can.. but beware if your hood or trunk part was made using epoxy resin.. the new polyester resin will not stick for long.

So to clear things up... epoxy over cured epoxy resin is good.
epoxy over cured polyester resin is good.
polyester over cured epoxy resin is bad.

Fast7......thanks for the reply. I think I will try to follow the steps you outlined. Dont think I mentioned it, but the crack has actually gone completely through the fiberglass (if that makes a difference) I do have a couple of questions for you (1)Someone recomended drilling one tiny hole at each end of the crack to stop it from spreading. Does that sound like a good idea to you? Also since there is a hollow air cavity beneath the crack....(2)someone recommended drilling a small hole next to the crack and adding just a little expandable foam insullation for support to the back of the crack. Does that sound good to you as well? and finally (3) Do I need to grind out the crack or not.
Thanks
Ken

Drop,

I doubt your hood was made with epoxy resin, more likely polyester resin or SMC. Is the hood factory primed? Is the hood smooth on the back side as opposed to rough (hand layed fiberglass) If it's smooth, it's most likely SMC and will require SMC resin to repair. Can you post a picture?
Since it is a structural crack ( clear through ) it needs to be repaired on both sides. Yes it needs to be ground out. Rule of thumb is to taper out along the crack 1" on both sides. Do not use fiberglass cloth, it will show it's weave pattern down the road. Use 1 1/2 oz fiberglass mat. grind out the back side at least 1/2 way through the panel. Use 2 or 3 layers of glass and try to tap any air bubbles with a paint brush. Once this is cured, do the same on the front side. Grind down the crack until you can just see the patch you did on the back side and taper out 1" on both sides. after this cures, grind down slightly lower than level with the surrounding undamaged area. Apply your bondo and finish as needed.

Hope this helps

Dan

I am unable to post pics at this time. The only problem I have is that I am unable to patch the backside of the crack. The crack is located over a completely enclosed air cavity in the bracing. As for the material used to make the lid...I have emailed the manufacturer (HO Fibertrends..here in the U.S.). The lid is completely gelcoated except for the center section on the underside where you can see the actual fiberglass. Dont know if that helps at all, but will post more specifics when HO Fibertrends responds.
Thanks
Ken

Drop,
Since this is a structural repair requiring repair to both sides and you can't get to the back side because of the rib, I would send it back. Tell them to pack it better next time!

Dan