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Repairing Spiderweb Cracks

Spiderweb cracks (aka gelcoat crazing, stress cracks) are all cracks through the gelcoat and resin in a GRP layup, often as a result of impact.  The often take for form of a spiderweb, hence the name.  These cracks are a big problem in a restoration, because unless properly repaired they will inevitibly find their way through your expensive paint job.  I was told by maany sources that the only sure way to repair these cracks is to grind them out and overlay them with fiberglass mat or preferably a very thin material callled finishing veil.

My plan is to circle the affected area, trace that circle to the finishing veil, then grind the crack out to the edge of the mark and lay the veil on top.

Finding them is not always easy, and I'm sure I'll miss some.  Shining a light from behind can help.

Here are all the cracked areas I  found.

Plus some on the roof. 

I laid the veil over top of the red-circled problem areas and traced the outline of the affected area onto the veil with a carpenhter's pencil, then cut it out with scissors.  Then the area within the circles was carefully ground out using 80 grit discs on an angle grinder.  You can work very carefully with such a setup and I ground away the resin-rich layer on top of the original glasswork, stopping before taking out too much glass.  I wonder if I went deep enough? 

I then laid the cut pieces of veil into the ground area and wetted it out with resin, with a result like this.

A light sanding, then filling and blocking out the body ought to do it!