by jspbtown » 22 Sun Feb, 2009 5:08 pm
The best answer is....it depends.
It depends on how deep your cracks are. Are they through the gelcoat and into the glass? Are they through the glass as well?
If they are just surface hairline cracks I would just spray a good two part high build primer, block sand, and finish with your choice of top coats. I personally like Evercoat G2.
If they are through the gelcoat but not through the glass I would router them out (I use a dremel tool) and then fill them with a high quality filler like Rage Gold. You could also use some reinforced filler like 3m High Strength Reinforced Filler (HSRF). Its pricey, but is is TOUGH stuff. Only use it in the cracks that contact the fiberglass and not on the gelcoat. I would only recommend this if you are a crazy fanatic that is looking for a show car.
If they extend through the gelcoat and the underlying glass is fractured I would grind them out, lay in some mat & resin, then finish with the Rage Gold.
For the screwholes I would enlarge them to about the size of a 1/2 dollar with a grinder. Taper them from shallow on the perimeter, then almost all the way through toward the center. Fill with matt and resin, sand with 80 grit to shape, and finish with Rage.
To prevent an uneven finish sand with a longboard in a diagonal pattern. Criss cross your sanding strokes. This, along with blocking your primer, will help achieve a flat finish.
After all body work I suggest the G2 as your primer.