Fiber glass/board repair help

LUCARO · Joined: 07 Dec 1997 Posts: 661

How successfully can a new layer of fiberglass be layered over existing cured glass?

Am i required to grind down all the glass to the Divinycell underneath or can i just go over the old layers?

DanWeiss · Joined: 24 Jun 2008 Posts: 2296 Location: Connecticut, USA

Without getting to technical, you can laminate over old glass without removing it. Whether you want to is determined by any number of factors, mostly relating the the condition of the laminate to which you wish to add.

Basic stuff applies. Sand the surface of the fiberglass laminate enough to "key" it for the new layers. Clean the old surface with an appropriate solvent. Tack cloth the dust. Don't try to laminate on top of paint.

swchandler · Joined: 08 Nov 1993 Posts: 10588

"Tack cloth the dust."

Dan, I have to question the use of a tack cloth. I can say from experience that use of a tack cloth when working with polyester resin is a really big mistake. You don't want to visit that nightmare. Maybe epoxy is different, but I would tend to doubt it.

To get the best results after sanding, I've found that you want a clean surface devoid of any dust or oils, to include fingerprints. Acetone is an excellent degreaser, but I try not to use it unless it's really necessary, and if I do, I use it very sparingly. The prep process that works best for me to remove dust is a sponge and water. Also, I've found that a toothbrush and water can be a handy tool to remove the dust in pinholes. I usually go through process two to three times to ensure a dust free surface.

bred2shred · Joined: 02 May 2000 Posts: 989 Location: Jersey Shore

Blow off the dust with compressed air or suck off with a shop vac after sanding. Then clean the surface with acetone or rubbing alcohol. Once you've cleaned the surface, don't touch it with bare hands.

You can laminate directly on top of the damaged glass, but it is a matter of asthetics. For any repair, you want to replace the damaged fibers with at least the same number of layers that were originally there. If you don't sand the surface down (at a taper), then you will end up with a "lump" where the repair is. It can still be plenty strong this way, it just won't look perfect.

sm

keycocker · Joined: 10 Jul 2005 Posts: 3598

If the top lamination is a piece of old sail window you can make a decent transition. Lay down just like cloth and squeegee out the extra resin.When you peel it the surface needs almost no sanding. If you don't do this you still shouldn't sand it through any glass layers no matter how bad it looks. Cutting through the layers ruins the strength.Epoxy and few layers is better than polyester and more layers because the resin adds strength and adheres better. It costs more but you don't use that much for a repair.

keycocker · Joined: 10 Jul 2005 Posts: 3598

Use cloth not mat
.Mat is sometimes used as top layer because it is no loss to sand it off.

bred2shred · Joined: 02 May 2000 Posts: 989 Location: Jersey Shore

LUCARO · Joined: 07 Dec 1997 Posts: 661

thanks guys for the tips

The board is pictured below. I just got it for a good price as it was in pretty bad shape. apparently it had come off a car roof while driving home. Repairs had been done by previous owner and he used it for a year at least. Some of the repairs were looking dubious so i thought i might have a crack at fixing it. A learning experience at the very least and its been very enjoyable so far.

I did much reading on the board ladies site and have made multiple trips to ship chandlers for supplies (more $ on supplies than i paid for the board). Any way as you can see from below i have completed a few steps

1) laminating divinycell in damaged areas
1.5) sanding down d-cell to match contours
2) used some q-cell to create a bog to fill some small areas

next comes (at least what i am planing on doing)

3) sanding down the Q cell
4) glassing over repair areas ( i was thinking 2 layers of glass most areas but probably just 1 layer on the very front of the nose where i did not grind down int the glass and that side ding near the deck pad
5) using a fairing compound to smooth out the glass job
6) unsure if it needs a layer of paint to protect epoxy from uv

If you have any tips for # 4 or # 6 or anything else i would appreciate it.

DanWeiss · Joined: 24 Jun 2008 Posts: 2296 Location: Connecticut, USA

swchandler · Joined: 08 Nov 1993 Posts: 10588

I remember your Alfa Romeo 164 photo some time earlier.

On the topic of Alfa Romeos, I did a photo shoot at the Briggs Cuttingham Auto Museum for an art project I was working on in 1971 while at the University of Calif. Irvine, and during the shoot the museum folks raced a 1934 award winning Alfa Romeo race car around the large parking lot. The event of sorts wasn't a lightweight affair, as it was quite fast and lively. These folks really stepped on it, and the sound of the engine was sublime.

The work I ultimately did was based on an outstanding 1937 Bugatti Atlantic, but the most impressive car that sticks in my mind over time was the 1938 powder blue Bugatti 57 Atlantic. Right out of a classic Buck Rogers scene. The 57 was for sale at the time for $160K. God, if I only had the money at the time, as the car was only one of three. Millions today.

Regarding the tack cloth, the result using polyester resin yielded a terribly pocked outcome that I couldn't accept, especially since it was a pigmented run. I had to sand it off, and completely re-do the schedule.

I think that your positive outcome was founded in using solvent afterwards, thereby removing the residual from the tack cloth. Frankly, I didn't, as I previously had great results with an oil based polyurethane. Just a stupid move on my part. Believe me, it won't happen again. I hate to mess up, but nobody is free from mistakes.