A holesaw is the way to go. It would be the best tool for cutting a proper hole. They do make adjustable diameter hole saws, but if it is a standard diameter, a regular hole saw should do the trick. Hole saws have a central arbor that you set at the centerpoint of where you want the hole cut.
A three inch diameter hole saw will require a fairly powerful drill.
BTW, if you run the saw in reverse initially, you won't chip the gelcoat as much... then once you're through the gelcoat, switch the drill to forward operation. The idea of using the holesaw from both sides is also an excellent one, and I'd recommend it.
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.
—Cpt. Mal Reynolds, Serenity (edited)
If you're new to the Sailnet Forums... please read this To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Still—DON'T READ THAT POST AGAIN.