drilling in fiberglass
 

I need to install a water dump off the transom or starboard side. Whats the proper way to drill a hole through without splitting or cracking the glass? Also what do you use to seal/treat the inside of the hole and seal from water intrusion? Thanks in advance, Derrick

two things I have always been told
heavy tape over the area to drill. inside and out

second, reverse drill to start with
prevents the gellcoat from chipping. Almost like sanding a hole first.

OH, MOST IMPORTANT

measure three times before you drill once :)

make sure you seal it afterwards

All good hints. Most most most important to check what's on the other side of and how thick where you're drilling in to. Sounds obvious I know, but not many thread mounts have >3" of nut travel! .:(

And clean everthing wit acetone, acrisol or somesuch.

A hole saw is needed, go slow so it does not melt the glass, you want shavings. Start outside so that any chips are inside. These have large trim/flanges so you can hide things. I used a one inch and had to use a half circle file to get the exact fit. I could have gotten away without silicone it was so tight.:cool:

racinbird.

If you can find one, use a forsner bit. (mostly found at a woodworking shop). It has a center point, and two cutting edges (versus a "V" like a regular bit). So it basically is touching on 3 points when you start. Run it in reverse first and you will get a perfect pre-cut circle. Gives a square cut hole.

Then run some 3m 4200/5200 in the hole along with the screw you plan to use.



Bob

.....Brad Point. (sorry)....... Plus it centers well and wont travel.

I forgot about those, nice tool to have, I need to get one, they do work well and can make a perfect size hole. Remember to keep checking so you don't go too large.

thx for the info guys

oversize the holes for the mounting screws just thru the gel about 1/8 to 1/4" otherwise when the screws go in you could crack the gel

Go to any local plumbing supply house and sk for a Lenox Carbide tipped hole saw. No matter how you hit the fiberglass or at what speed yo will not chip it. Most normal holesaws will but carbide will not - they are not that expensive.

Ditto on the reverse running, go slow in reverse and get through the gel. Once you are through the gel chamfer the gel cut with some sandpaper so your saw cannot catch an edge. A hole saw will get hot going through the transom and a cheap one will start to deform from the heat which will cut an oval or ugly hole. Once the pilot bit comes through the inside start form the inside and cut a relief about an 1/8 of an inch or so. Go back to the outside and finish the cut. This will prevent splinters when coming through from the outside to the inside. Take your time and don't let it get hot.

All that stuff. And coat the inside with polyester resin or epoxy. If you keep the boat you'll thank me!
Seal the fitting with silicon or use 5200 if you never plan to remove it.
Gary