drilling gelcoat / fiberglass

[Meach]

OK so now that I have resigned myself to putting a big ole hole in my new (to me) boat..... on purpose I am asking you for help so I dont make the same mistakes others have made. When I put in screws for the top I drilled the pilot hole the instructions told me to and as soon as I started screwing in the screw the edges of the pilot hole exploded with big chunks flying off in all directions! OK so Im exaggerating but seriously the edges did crumble a little and I was glad the pole holder base covered it all up. Now for the transducer it calls for a one inch hole to get the cable through. I dont have a one inch steel bit but I do have a one inch spade bit for wood. Will this work well or would it be a disaster? Any advice on the one inch hole or how to keep the edges of the pilot holes from chunking off at the edges would be appreciated.

Thanks

Mark

 

[Dr Honda]

Yep... that's kind of normal for "Gel". What I do is a pilot that is opposite of normal.

SO... lets say you want a 1/8" inch hole for your screws. I will use a very sharp (new, good brand) 1/4" drill to open the top of the gel clean. Don't go all the way in... just a nice taper in the color coat, where the tip will just touch the fiberglass. Then, when you go in with the 1/8" drill... it will only chip away at the very thin edge.

If you do a typical "Pilot Hole"... then you are attacking the thick edge of the color coat, with no support in the center, and the bit will "Walk" inside the hole as it bites the edges to find center. And, that's what chips the gel.


Ultimately... it really doesn't mater since you will cover it with RTV and the mount... but doing it my way... it will keep a big chunk from coming out.

 

[Coastiejoe]

Place heavy masking tape over where you want to drill. Seems to help a lot.

 

[Sportster-2001-951C-Stock]

Yes, gelcoat is very brittle thus spider cracks easily so you must take appropriate precaution. Especially subject to cracking under distortion due to fastener clamping forces and brittleness increases in places where gelcoat is thickest, such as corners where it collects when sprayed into the layup mold.

Fortunately there are many sources available describing the best practices, consider seriously their suggestions.

 

[racerxxx]

To expand on Doc's method......I use a center drill on just about every hole I drill, gives you dead center and also will chamfer the hole for your next sizes. They don't flex like a small drill will. I'd hate to see that 1/4' drill hook and draw in and then you have the wrong size hole. These are cheap but would be perfect for what you need to do.


http://www.ebay.com/itm/5-Pc-Premiu...070716?hash=item1e96fb4dbc:g:-WAAAOxyx0JTfRe8

 

[Meach]

To expand on Doc's method......I use a center drill on just about every hole I drill, gives you dead center and also will chamfer the hole for your next sizes. They don't flex like a small drill will. I'd hate to see that 1/4' drill hook and draw in and then you have the wrong size hole. These are cheap but would be perfect for what you need to do.


http://www.ebay.com/itm/5-Pc-Premiu...070716?hash=item1e96fb4dbc:g:-WAAAOxyx0JTfRe8

I just love when someone gives me a solution tp a problem. ESPECIALLY when I get to buy new tools! Havent maxxed out that new Lowes card so I better get down and spend some money. Thank you all very much for the words of advice they are very much appreciated.

Mark

 

[Sportster-2001-951C-Stock]

A few references I find helpful, not sure if these discuss the wooden dowel plug coated in epoxy to hold screws that have stripped out of the glass but also on my list of repair methods.

http://www.boatus.com/magazine/trailering/archives/drilling-and-repairing-fiberglass.asp
http://www.boat-project.com/tutorials/drill.htm
http://www.pbase.com/mainecruising/installing_a_thruhull
http://www.yachtsurvey.com/hardware_attachments.htm
http://www.boatus.com/boattech/casey/bedding-deck-hardware.asp

This one sets us straight on downfalls of some of the above, this guy is great, he knows his stuff.

http://www.pbase.com/mainecruising/rebedding_hardware

 

[racerxxx]

I just love when someone gives me a solution tp a problem. ESPECIALLY when I get to buy new tools! Havent maxxed out that new Lowes card so I better get down and spend some money. Thank you all very much for the words of advice they are very much appreciated.

Mark

Lol, I'll start a project just to buy a specialty tool, or 3.

 

[Nike12000]

Anytime you drill gelcoat run the bit backwards for a few seconds till it makes a small spot in the gel and then forward will make a nice clean hole.

https://www.youtube.com/watch?v=9YsY9hMfcng

 

[Meach]

Great video. Im going to be drilling some holes tomorrow so I have a good supply of new tips and tricks to help me do a great job. Thank You all so much.

Mark