When drilling or cutting gelcoat...

[bigdaddy_houseboater]

I just noticed a thread that showed a ballast install. The author cut a 1" hole using a holesaw in the side of his boat and installed a bulkhead fitting. Very clean cut.... except I didn't see any bevel in the gelcoat. Without a bevel, he will experience cracking in the gelcoat. Always, when drilling or cuting a hole in a gelcoat surface, bevel back the gelcoat. For drilled holes, use a countersink and bevel just past the gel into the fiberglass. For holesawed holes, use a fine half-round file, and bevel just past the gel to the fiberglass. This breaks the sharp edge of the hole and prevents the brittle gelcoat from stress cracking.

[duffymahoney]

Also I know people say to run the hole saw backwards till the hole saw is through the gel coat.

[bigdaddy_houseboater]

Good point. I do this as well. This prevents chipping during the drilling. Gelcoat is extremely brittle as plastics go, and it chips and cracks if given the right situation.

[G-MONEY]

Also use tape over the place you are going to drill through...

[IDBoating]

All good pieces of advice. I just cut eight one inch holes this afternoon (for drains and vents) and all went well thanks to the above steps.

I used to run the drill/saw in reverse all the way through, but a while back I moved to the "just through the gelcoat" approach. It works fine and is MUCH faster. Then a little emery paper to bevel the edge and you're good to go!

I'll add one more: If you're using a hole saw and care about what the backside of the hole will look like, cut about halfway through and then finish by cutting from the other side. The pilot bit in the hole saw will insure you line up perfectly, and you'll get a nice clean edge on both sides.

[bigdaddy_houseboater]

Arent we all just the hole-sawing experts of the world now? LOL

[Dave K]

All good pieces of advice. I just cut eight one inch holes this afternoon (for drains and vents) and all went well thanks to the above steps.

I used to run the drill/saw in reverse all the way through, but a while back I moved to the "just through the gelcoat" approach. It works fine and is MUCH faster. Then a little emery paper to bevel the edge and you're good to go!

I'll add one more: If you're using a hole saw and care about what the backside of the hole will look like, cut about halfway through and then finish by cutting from the other side. The pilot bit in the hole saw will insure you line up perfectly, and you'll get a nice clean edge on both sides.

Heres a further tip...when your drill for your discharge thru hull hole just drill enough to have the 1/4" pilot bit to go all the way through the hull. Now from inside if you have access, use a 2" hole saw JUST TO CUT THE CARPET, then go back to the outside just to finish your original 1' hole. You now have a very professional looking job and your thru hull nut can be screwed down right the hull. How many times have you seen a crappy looking square notch of carpet cut for the round nut??

(NB. You may need one of those 90 deg chucks.)

[bigdaddy_houseboater]

Hey Dave, do you run the holesaw backwards to cut carpet? I think it would get all torn and pulled if you went forward.