Drilling thru fiberglass

[Dan(MI)]

I'm buying a fiberglass boat this week and the first thing to do is mount a compass and rodholders. I've heard a few ideas on how to such as placing tape down, or putting a board behind the backside. Can anyone share what has worked with them.
Its a Fisher FX 18.
Thanks in advance.
Dan

[Ernie Hamby]

The easiest way to cut down on the gel coat chipping of edges is to run the drill or hole cutter in reverse to get through the gell coat. www.hambys.com

[ebijack]

putting tape down does help..go slow because the drill will tend to want to grab and chip the glass. probably the best drill is a step-drill bit (such as uni-bit)(i believe sears has there own models) there not cheap, but they work great on everything upto 1/4 steel. depending on which ones you buy, they have many models. some go from 1/8 to 1/2 (same bit) 1/4 to 3/4, 1/2 to 1 inch. or if you know anyone who has access to drills (or sharpened) for drilling plastic. with a good grinding wheel it is possible to put the right taper on most any drill to make for a cleaner cut depending on what your drilling. hope that helps

[Bob Z]

If you will be driving screws through the fiberglass to a wood backing be sure to drill out the fiberglass to a slightly larger diameter than the diameter of the screw shank. Otherwise you will likely break off the screws in the hole.

[REW]

Dan,
Two things:
a. Put tape on the fiberglass before drilling.
b. Use a sharp bit.
c. After drilling the hole, but before putting in any screws, take a countersink, and bevel the top edge of the hole. Make sure that the edge of the bevel is a bit larger than the largest part of the screw or bolt hole. This will stop the gel coat from cracking.

Another nice reason for putting masking tape on the glass, before drilling, is that masking tape can be written on very well with a ball point pen - and if you have to mark a couple of times, before getting it exactly right - when the tape comes off, so do all the marks.

Also, if you happen to have to make a very large hole, and decide to use a scroll saw, or jig saw, the tape will protect the glass, from the hammering and marking effects of the bottom of the saw.

Take care

REW

[Stan]

Dan,

I would agree with all the others posts, but offer one additional hint. Use brad point drills. they cut the outer edge of the hole before removing the majority of the center, providing a much cleaner hole. Don't forget the masking tape, slow speeds, and even reverse direction at first.

You can even use Forstner bits for larger siameter holes.

Enjoy your new boat.

Stan

[woody]

Dan Please do everything all these people toldyou to do, and do it very carefully. They have some very good input and seem to know what their talking about. When your all done, please take it to a professional to fix all your mistakes before you sink your new boat. Dad

[PWaldow123]

HARSH!!!!!

[Pitts]

Stan and Dan I just mounted my new excel troller and the rubber mounts need a 1/2" hole. I couldn't find my 1/2" twist drill bit so I used a spade bit which cuts the outer edge of the hole befor removing the center. It cut about as smooth of and edge on the hole as you could ask for sharp and clean. Stan we must be talking about the same bit, brad point and spade. No tape used very nice hole I know if I drill again I have them down to 1/4" so thats what I'll be using.

Pitts

[WestCoaster]

If the holes are of any significant diameter, the use of masking tape and a hole saw works well. I run the hole saw in reverse much like you'd start a cut with a hacksaw. This technique has worked well without any chipping on three boats so far. Chamfering the OD of the hole will prevent chipout should you accidentally strike the edge of the hole with something. If you go thru fiberglass and then into structural wood, it would be a good idea to coat the wood inside your bore with a thin coat of catalyzed polyester resin or paint. This will help prevent wood rot should water penetrate that area. Good luck!

[Stan]

Pitts,
I'm glad everything has worked out for you. Spade bits are different than Forestner bits. Forestner bits are used a lot in finish wordworking where a very clean hole is desired with little/no splintering. They are expensive.
Cutting the outer edge of the hole first (with any bit) decreases the "tearing" that most standard drills do as they grab material in the center of the hole and try to cut or twist it out. Since the edges ona regular drill hole, are not yet defined, the splintering/tearing extends past the diameter of the bit.
Take Care

[Dan(MI)]

Thanks for the tips.
Dan
Go Fishin

[Pitts]

Stan I knew what a forestner bit was but I have never heard of the brad point bit thats what I was asking about.

Pitts