Marine-installing DOT studs into the gel coat

[Jasmin]

I was looking for any tips or advice regarding the installation of the DOT studs into a boat's gel coat. I have done a little looking around this forum and am finding few posts about this part of the bow and cockpit cover  installation.

Concerns-
installing the studs without cracking the gel coat (stuff chips like glass).
installing solid studs that don' t come off when the cover is removed.

After marking the stud locations around the perimeter or the boat, I proceed to drill the holes-
should you remove enough gel coat around each pilot hole so the stud threads don't cut into it's gel coat finish?
should you NOT pilot drill the fiberglass underlay at all?
if there is no pilot hole in the fiberglass, could that damage the gel coat ?
Does the clear plastic washer that goes between the stud and the gel coat make a diff?
should silicone fill the stud hole?



Jasmin

[Peppy]

I drill a 1/8" pilot and ream the gel coat out with a countersink. I remove enough gel coat to see the fiberglass around the pilot hole a little bit. I actually have a countersink/counterbore dooiey that drills the hole and reams at the same time (or with the same bit anyway). I use marine silicone but not the washer things.

I worked with a guy who was fresh from the boat factory. He (and they) drilled a pilot then ran the screw backwards with a drill a bit then drove it in. I don't like that way but it sort of works-ish.

As a side note, I've found if you countersink a pilot hole a little it makes driving a SS screw into aluminum MUCH easier.

[regalman190]

If you don't have the combo bit, drill your pilot hole first, then use a larger drill IN REVERSE to countersink. If you don't, the gel coat will shatter.

[SHHR]

I agree with peppy, it's easiest to drill a pilot hole. I use the self tapping studs and I have and it's tempting to just run them in with a drill/driver. The problem is you'll often times twist the snap heads off leaving the stud in the 'glass, aluminum, or whatever.

The hardest one I ever did was on a local hydroplane raceboat. I was installing a cover over the enclosed cockpit, and those boats are made out of kevlar and carbon fiber instead of fiberglass (they skip along the course close to 200 mph). I used cobalt drill bits for the pilots and still went through 9 bits for 25 studs.
Kyle

[Mike8560]

if you dont have a countersink, after you drill your 1/8" just ream it with your screwgun tip to bevel the edge before you install the stud.