Safe way to cut a fiberglass hull for speakers

Bayliner175xt

Petty Officer 2nd Class
Joined
Mar 20, 2010
Messages
130
Hi just wondering if anyone has used a jigsaw with a fine blade to cut out holes for a pair of 6" speakers in the front of a bow-rider (Fiberglass).

Pre drill then jigsaw !!!

Your thoughts people.

thanks :cool:
 

dsiekman

Senior Chief Petty Officer
Joined
Jul 7, 2010
Messages
798
Re: Safe way to cut a fiberglass hull for speakers

Sounds like it would work. Might try a dremel, too. Or a Rotozip...

I'd say cut the hole small and come back with a file or dremel to clean it up. You'll be surprised how quickly a file will take down fiberglass!
 

kenmyfam

Supreme Mariner
Joined
Aug 10, 2006
Messages
14,385
Re: Safe way to cut a fiberglass hull for speakers

Start small and work gently toward the size you need.
 

Mr_Shamrock

Petty Officer 2nd Class
Joined
Oct 8, 2009
Messages
127
Re: Safe way to cut a fiberglass hull for speakers

They sell hole saws that give a clean perfect circle.
 

a70eliminator

Captain
Joined
Sep 9, 2007
Messages
3,688
Re: Safe way to cut a fiberglass hull for speakers

Jigsaw with composite blade works great, I drill my starter hole so it lands right on the circumference, then cut slowly and carefully right dead on my mark.
Make sure to do a dry run, just go through the motions without a blade just to see that you have clearance all around.
Oh one other important thing, protect your skin or you will itch like crazy.
 

Mr_Shamrock

Petty Officer 2nd Class
Joined
Oct 8, 2009
Messages
127
Re: Safe way to cut a fiberglass hull for speakers

If your going to use a jig saw make sure you either tape up the bottom (foot) of the saw or tape way around your cut out area or both. The jig saw foot will scratch your fiberglass.
 

scca vette

Petty Officer 1st Class
Joined
Feb 23, 2009
Messages
293
Re: Safe way to cut a fiberglass hull for speakers

I used a Jig Saw with a pretty agressive bit and had no problems. I do suggest using a little smaller blade than I sed however it worked fine for me. Just drill a hole to start and follow the line you traced. I just installed the 2 6x9 speakers and lights in my engine cover and had 0 issue. I do agree with the comment that it will scratch or leave some marks on the foberglass. This was no big deal for me do to I was going to wetsand and buff the piece after all the holes were cut anyways.

Here is a photo of mine installed in the engine cover.
IMGP5513.jpg
 

RoryDominick

Seaman Apprentice
Joined
Mar 7, 2010
Messages
32
Re: Safe way to cut a fiberglass hull for speakers

I used a dremel tool, it worked great. It has a blade that looks like a drill bit. Just wear a dust mask.
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
27,036
Re: Safe way to cut a fiberglass hull for speakers

Cutting and grinding fiberglass is easy. Sanding is easy as well. Use any king of tool that cuts wood. A finer blade is better for finish work. Jigsaw, sawzall, skilsaw all work fine.

The itching effect is overrated. However, if you get a lot of the FG powder on you take a shower and use a washcloth on arms, neck and legs if necessary.
 

H20Rat

Vice Admiral
Joined
Mar 8, 2009
Messages
5,199
Re: Safe way to cut a fiberglass hull for speakers

I've cut A LOT of holes in fiberglass, as well as made a fair number of my own speaker boxes out of fiberglass. (used to compete in car audio) Anyway, a rotozip with a fiberglass cutting bit is by far the best/easiest/most pain free way of doing it. Doesn't even have to be a true rotozip, I use a cheap harbor freight clone.

Jigsaws are ok, unless you are cutting into an area that might have wood backing behind it. They will tend to scratch the gelcoat though if you don't protect it, as well as break it on the cut line.
 

seabob4

Lieutenant Commander
Joined
Jun 10, 2008
Messages
1,603
Re: Safe way to cut a fiberglass hull for speakers

These work great, get a cheap one from HF...
HighSpeedMetalSaw.jpg
 

ajgraz

Lieutenant Commander
Joined
Mar 1, 2010
Messages
1,858
Re: Safe way to cut a fiberglass hull for speakers

Dunno what all you got in the way of tools, but here's what I'd do with what I have if faced with that task:

Make a wooden round on a router table (or with a hole saw if have one large enough), small hole in middle, radius equal to radius of hole minus radius of dremel 565 multiprpose cutting attachment:
http://www.tylertool.com/drem565mulcu.html
tylertool_2113_223430126


Bolt the round through the center, centered on the fiberglass to be cut out. Drill a starter hole, then cut the round out with the dremel and the cutting bit, using the wood round as a template, making at least 3 or 4 total passes.
 
Joined
Oct 24, 2009
Messages
50
Re: Safe way to cut a fiberglass hull for speakers

a 5" hole saw and a corded power drill will give you a perfect fit, no exceptions. Because it has a drill bit through the center it won't wander and at $4.99 at harbor freight, it's the cheapest insurance you'll ever buy. I used it to install all of the speakers off my dual stereo from west marine.
Just remember, measure twice and make sure you know exactly where you want them.
 
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