drilling through fiberglass for antennas and remotes

[mikeblas]

I'm an electronics wiz, and do a lot of my own work on my car. I'm unfamiliar with my new (to me) boat, though... I've never done any fiberglass work, nor have I done work on boats.

I want to install a VHF antenna mount, and maybe some other things that will require drilling through the deck or hull. For my VHF mount, I'll want four holes for the base plate, and another hole for the coax. I'm also thinking of a wired remote panel on the transom.

What can I expect when I drill?

What parts would you recommend to clamp the cables? Do I install nuts on the inside wall, or tapping screws to grab the fiberglass wall? Washers? Should I expect the deck to be very thick? What about the sides? Will they be single-walled, or double-walled? Should I use sealant around the screws, or just the vendor-supplied gasket for the base of the radio?

I think the transom is about two inches thick (because a mechanical diagram of my engine and stern drive says so, not because I measured it). What's the best way to drill a two- or three-inch hole for a radio remote? Just use a hole saw? Or am I better off with a high speed tool like a RotoZIP?

Thanks!

 

[Reel Poor]

Re: drilling through fiberglass for antennas and remotes

Before drilling or cutting any holes make sure you can access the area from the backside and that there is nothing there to interfere ie; wires, hoses, ect. If the fiberglass is 3/8 or thicker tapping screws will be fine, be sure to chamfer the holes through the gelcote right down to the fiberglass (use a chamfering bit, not a larger drill bit), this will keep the gelcote from hairline cracking. Also place a piece of masking tape over the area to be cut or drilled, this will help stop chipping caused by the drill bit and scratches if something slips. If it's thinner than 3/8 use thru bolts, flatwashers, and nylon locking nuts. When covering the coax, going thru the hull you can use something like this, Midget Clam Shell Cover or a Cable Outlet. Seal all screws/bolts and any thing that might let water in with 3M 4200 sealer.

When cutting large holes, drill holes at all corners(sufficient size for the template radius of corners). Then cut with a Jig Saw between the holes to finish. I don't recommend a RotoZip because they can run wild sometimes when you need a straight line. You might use it for some fine tunning of your holes.

Take your time and be sure of what is behind the area you want to cut or drill and use tape for safety.

 

[mikeblas]

Re: drilling through fiberglass for antennas and remotes

Seal all screws/bolts and any thing that might let water in with 3M 4200 sealer.

Thanks a million for the recommendations, Reel. I'll have to go get a tube of that goop. Does it fill the hole around the screw, or plug the hole from the back side?

When cutting large holes, drill holes at all corners(sufficient size for the template radius of corners). Then cut with a Jig Saw between the holes to finish.

What about round holes? Do you recommend trepanizing the hole, or just using a hole saw? What kind of hole saw -- wood, bimetal, or HSS?

Thanks again!

 

[KaGee]

Re: drilling through fiberglass for antennas and remotes

A hole saw is fine for the larger diameter.

 

[Reel Poor]

Re: drilling through fiberglass for antennas and remotes

When using the 4200 use libral amounts to seal all voids and possible places where water can intrude into the class. Wipe off excess with a damp cloth.

If you buy a set of holesaws, but the deep set, you'll be glad you did. Bimetal works great.

 

[mikeblas]

Re: drilling through fiberglass for antennas and remotes

Thanks again for your helpful responses, Reel!