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Fixing a cracked fiberglass hardtop

8K views 5 replies 5 participants last post by  **DONOTDELETE** 
#1 ·
After searcing forever I found a really good deal on a CJ-7 hardtop for my street jeep. The glass and hinges and rear door are in great shape. It does have a crack in the top on the driver side extending in about 8 inches. It's above where the middle of the door would be. I haven't done much fiberglass repair (put it in the floorboards of my old body and it flexed and started poping out). I was thinking about taking it to a boat place but figured I would ask to see how easy people thought it was to do...

TIA

GreenMachine
 
#2 ·
Here's what I'd do (This is a case of the blind leading the blind):

1. Drill the end of the crack with a small diameter drill to relieve the stress.
2. Sand the area of the crac, and around the crack, top AND bottom.
3. Get some fiberglass cloth and resin.
4. Put some Duct tape on the UNDERSIDE of the crack.
5. Pour resing the length of the crack.
6. Imbed fiberglass soaked resing into, onto, and around the crack.
7. When hardended trim.
8. Turn the top over and repeat steps 2 - 7 (minus step 4).

The problem as I see it is reproducing the factory finish.

 
#3 ·
If it is just a crack, you could drill the hole, "V" out the crack with a dremel, then put some 3M 5200 in there. The 3M 5200 is a white adhesive for fiberglass that a lot of boat companies use to attach top decks to hulls. It is waterproof, dries in 24 hrs, can be painted,is applied like caulk, and works really good. I used it on JetSki repairs when I used to race them, and it held up to ocean wave jumping.

pbm
There is a difference between being Educated and Intelligent!
 
#4 ·
It probably cracked because it flexes at that point, and will need significant reinforcing if it's not to occur again soon. Is there a corresponding crack or loose joint on the inside as well? Use fibreglass mat and polyester resin. Finish the surface afterwards with a thin layer of body filler. As others mentions, grind out the crack, don't be afraid to open it up say 1/4 inch, bevelling the edges, and grinding down for clearance for several layers of mat for about 6 inches wide. You will be able to figure out how thick it is when you grind open the crack and bevel that edge. Grind with a course sanding disc to make for good bite. Wear a dust mask to avoid inhaling the dust. When finished, sand it down smooth and apply thin layer of lighweight body filler and sand to perfection. Luckily the top of a jeep isn't subject to that much scrutiny. My top was in several peices and the hinges pulled out with the plates when I got it, but it looks as good as new now. Best to soak the matt strips in the resin after mixing with hardener, then apply the stips one or two at a time (you don't need to repair it in a single application of mat), brushing or rolling out any air bubbles or pockets. Remember, it's the glass that gives it the strenght, so use more glass, minimal resin to get the job done. Sand between layers to get best adhesion. It will be as good as new.

Tim

84 CJ7, 258, HEI, M/C 2100 carb, 5 inch lift, RS9000's, 33x12.5 BFG M/T's, 4.56's and Detroit softlocker, full cage & belts, Xenon flares, Dana 44 rear, GM dual diaphragm brake booster
 
G
#6 ·
The previous lists of repairs all have bits and pieces of the total picture.
You need to determine if the crack goes all of the way through the top fisrt of all.
If so you'll need to pay attention to both sides. If it is only top side you need to prep the area surrounding the crack itself within a couple of inches on each side of the crack, sanding through the top layer. You can drill at the end of the crack as Leve said to do for the obvious reasons. You'll need to cut several pieces of the fiberglass cloth approximately the same size as the sanded (prepped) area. Then you need to mix the resin and hardener and soak the "glass" cloth on both sides and the lay the stips in the prepped area using a spreader to wipe the cloth flat and to remove air pockets in the mix. Let it cure then sand as needed. There are many other ways, steps and techniques that could be used but this should be all that is needed. I've also used various products to duplicate the texture is so desired. Just in case you're wondering I previously worked for Hairy Glass.

JpShp
http://www.jeep-shop.com
 
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