underside rear deck fiberglass repair

[Don W.]

I have a 69 coupe and just removed the gas tank in order to replace the tank. Looking at the bottom side of rear deck I see that there is a crack in the bottom of the fiberglass that extends all the way across the rear deck. Looking at it from the top, everything appears fine. Is there some type of quick fibergass glue that I should put a bead of along the crack to give some additional strength?

Thanks,

Don

[Keith B.]

Re: underside rear deck fiberglass repair

If it were me I would use fiberglass resin with fiberglass cut into very fine pieces integated into it. Take a small grinder on a dremmel and V the crack out ever so slightly. Mix up a small batch of resin and take fiberglass strands and cut them into tiny (as small as you can cut) pieces. Pour the fiberglass directly into the resin. Use a small brush and paint the resin/fiberglass resin into the grove. It might take more than one application if your cautious. Do not to get it all over everything or you can end up with a mess. The resin/glass is very strong and should create a nice bond. If you chose use 600 grit paper once done to blend in. Avoid sanding anything other than the resin you placed in the grove. I always have gone with theory --Do it once...do it right

Keith

[John H.]

Re: underside rear deck fiberglass repair

If it's indeed a long crack across that relatively flat panel, I'd scuff along both sides of the crack and reinforce it along its full length with resin and 'glass mat at least 1" wide; I wouldn't depend on applying a resin/chopped glass mixture only in the crack itself.

[Chuck S.]

Re: underside rear deck fiberglass repair

I'm with John on this one... V-grind it and laminate mat and resin across the "crack". If that "crack" is what I think it is, you may be able to prevent a much larger head/heart ache.

A crack across the rear deck in that location is unusual...in fact, I've never heard of one. Even more strange is how you can see no evidence of the crack on the top deck surface.

I suspect you are looking at a bad repair of the rear deck/spoiler from rear-end damage. Examine the crack closely: If it's pretty much in a straight line and equidistant from the tail light panel all the way across the deck, then you're probably looking at a mistake often made in fiberglass repair...if you want the repair to be as strong as the panel you have to laminate mat and resin on BOTH SIDES of the panel.

[Mark S. Lovejoy]

Re: underside rear deck fiberglass repair

I would be very careful with adding polyester resin to the underside of a painted surface.

When the resin 'kicks' it gets very hot, I would be concerned that it might effect the paint.

If it ain't broke....

[Chuck S.]

Re: underside rear deck fiberglass repair

The remedy for that is to not over catalyze the resin...always read the directions; 12-14 DROPS of MEKP per once of resin. If any of my repairs have had perceptable heat, I've never noticed. If he wants to be safe he can wait until this fall/winter; he'll have to build a fire under it to get it to kick off.

Now, I won't say problems can't happen if you over-catalyze the resin. I once witnessed three cocky machinists set a machinery base on fire by over-catalyzing two-part epoxy grout. (How could you screw this up??!!...Two equal volumes; you pour them together and mix? ) Several thousand dollars worth of epoxy grout and three man-weeks of labor went up in smoke. Plus, there was that tricky proposition of dealing with fire inside a petrochemical plant. It humbled them...for about 3 minutes after they left their boss' office post-reaming.

As for doing nothing, that is an option...but, I think you're forever waiting for the other shoe to fall; and when it falls, it's going to be loud. The proper steps taken now may keep the top side from ever showing the repair.