Cutting Fiberglass

Junkee · Posted: Feb 26, 2005 11:03 am Post subject: Cutting Fiberglass

i searched couldnt find what i needed. so i now pose the question.

I needed to cut into the fiberglass in the bow of the boat[01 moomba], to install 6.25'' speakers.

What is the best way to do this? i want it to look clean, and not damage the rest of the fiberglass in the bow.

TIA.

K-dub · Ladies Man Joined: 12 Jan 2003 Posts: 14760

hole saw.

138jobe · Outlaw Joined: 30 Jan 2005 Posts: 174 City: Calgary

Junkee, Just rember when your cutting into FG take some masking/scotch (the tan colored, rips easy) tape lay it on the area you want to cut,and draw your circle on the tape and cut it out, will help with controlling splintering.

I would say use a jig saw to do it. finding a 6.25" hole saw might be hard.

STALEFISH79 · Outlaw Joined: 19 Jun 2003 Posts: 200 City: CAPE CORAL

this is the best way....

draw your pattern out.... go around the circle and about every inch or so drill a whole , at least big enough to fit your scroll saw blade into.. this method will really keep you from doing more cutting than you have to and reduce the margin for error on a large circle such as one for speaker... using the right blade will help reduce splintering and the tap idea as stated above may work... never tried that for finish work. good luck!... have a couple drinks before you start to help steady your hand!!! lol

ballywho · Wakeboarder.Commie Joined: 05 Feb 2005 Posts: 1725

You want the best way, hire someone. I work in a marina and my parents own a boat repair shop. I have seen way too many do-it-yourselfers screw up and have to pay extra to get their damage fixed then do the job. Where you are planning to put the speakers has alot of vital supports (where the impact of the waves gets absorbed) and if you mess one up you're in deep stuff. There is a way around hireing someone or risking it but tis long so just pay someone to.
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-=LoneStar=- · Addict Joined: 20 Nov 2004 Posts: 751

RotoZip + Circle Cutting Attachment = $80 and you get to keep the tools.

Clean it up with a drum sander attachment on your drill.

ballywho · Wakeboarder.Commie Joined: 05 Feb 2005 Posts: 1725

one last time. PLEASE hire someone. Also think of where you're putting the speakers. What area takes the most pounding? the bow. What area gets the wettest, the BOW!!!!! They wont last a week.
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lee · Outlaw Joined: 13 Jan 2003 Posts: 196 City: USA

You can buy a hole saw that big and just run it in reverse to get through the gelcoat then flip it back to foward and happy cutting. Be sure to run the drill slow.

twitch88 · Posted: Feb 26, 2005 6:33 pm Post subject:

the first reply was the right one, a hole saw will take care of it.

Geoff Standish · Addict Joined: 13 Jan 2003 Posts: 843 City: Calgary

Junkee, I did the same thing with my'01 Mobius. I used the jig saw method. Make sure you mask off alot of the area. Measure lots! I under cut the hole and finished it off with a drum sander just as -=LoneStar=- mentioned.

I can appreciate the concerns ballywho is mentioning. But I don't think you need to worry about it too much. That space is designed for speakers, if I remember that area is only about 1/2" thick. \

There is a comfort that if a mistake happens with hiring someone they are on the hook for the bill. I think if you take your time you'll be fine. I know the first time I drilled into my boat I was beyond nervous...after the first one you'll do great.

If you can find a hole saw that would probably be the ideal.

Good luck!

-=LoneStar=- · Addict Joined: 20 Nov 2004 Posts: 751

twitch88,

The only problem with that is that you'll be spending $40-50 on a hole saw that you'll probably never use again. I'd much rather buy a versatile tool that will be only slightly more difficult to use.

ballywho,

Some people trust themselves more than the boat monkeys employed by some of the dealers. For a simple job like this, the key is being careful and patient. A typical owner is going to spend a lot more time making sure it's right.

STALEFISH79 · Outlaw Joined: 19 Jun 2003 Posts: 200 City: CAPE CORAL

finding a 6 inch hole saw may be a pain though?

lee · Outlaw Joined: 13 Jan 2003 Posts: 196 City: USA

http://www.grainger.com/Grainger/productdetail.jsp?xi=xi&ItemId=1611724625&ccitem=

bradb · Outlaw Joined: 09 Jan 2004 Posts: 204 City: Parksville

Drill a small hole in the middle and make sure nothing is behind where you are going to cut.
If it is gellcoat, you are probably best using the holesaw, but if it is just fiberglass, then use the jig saw and you will be fine. I've done both, and once you have done it, it is no prob.
Measure twice, cut once!
B

timmy · Addict Joined: 18 Jun 2003 Posts: 882 City: Jupiter, FL

sell the hole saw on ebay after you are done. someone will probably buy it

Junkee · Posted: Feb 28, 2005 6:45 am Post subject:

Thanks everyone. Very Happy

BIZ · Outlaw Joined: 19 Jan 2004 Posts: 184 City: Dallas

$71 for a hole saw w/ the arbor... NO Thanks! Buy a rotozip and take it slow, or an even cheaper way is a jigsaw. Check to make sure you have enough depth and then check again. Or have a shop cut the hole for you, this may be an even cheaper way to go and you don't get fiberglass on you.

Lcky275 · Posted: Feb 28, 2005 4:53 pm Post subject:

Borrow Lee's

lee · Outlaw Joined: 13 Jan 2003 Posts: 196 City: USA

Sure why not! Come and get it.

MobiusMan · Newbie Joined: 24 Feb 2005 Posts: 19 City: Lewisville

I agree with BIZ. Use a roto-zip. That is what I used to enlarge the six factory holes in my 2003 Mobius LSV last year to install my MB Quarts. Just take it slow and DO NOT RUSH. These power tools have a way of getting away from you if you are not careful. My installation turned out flawless and took just a weekend to complete. Just remember if you ever sell the boat, you will most likely have to keep the after-market speakers installed since the stock ones will no longer fit! Good Luck.

oshensurfer · Posted: Mar 01, 2005 9:25 am Post subject:

I'm surprised no one mentioned lube. I saw the tape suggested, which is good. Reduces splintering...

Here's the steps I take when cutting through fiberglass on my boat.

- Lay out and tape off the spot that will be cut, this is not absolutely necessary. It's a good suggestion though.
- Use a hole saw, spray it with silicone lube, run it in reverse to etch through the gel coat (until you see powder
- Run the drill forward and begin cutting, have someone spray silicone lube lightly onto the cut while making sure you are holding the drill steady. This will help the saw cut smoothly and not bind.
- TAKE YOUR TIME.
- After hole is cut, remove fiberglass and ease the edges with a barrel sander bit. This will help eliminate spider cracks. So the same thing for the screw holes.

Cutting fiberglass is not that difficult if you take your time. I'm like Lonestar, I trust myself more than some of the shops around.

chavez · RIP MHL 04/25/1958 - 01/11/2006

I used to use a "Circle Cutter" for large diameter openings back in my install days.

They were about 20$ at the hardware store and cut a perfect circle every time.

Several brands make them, and here is a pic for reference:

Also, see what oshensurfer said about lubricant & taking your time. A well lubed blade/drill/cutter is an efficient one.

MobiusMan · Newbie Joined: 24 Feb 2005 Posts: 19 City: Lewisville

I just have a small comment about the "circle cutter" or "hole saws". Those tools are excellant for making new holes, but it gets a little bit more tricky to use them when you are enlarging existing holes since you dont have a way to reference the center since the center is already cut out. However, you could temporarily install a board behind the hole and attach it with the screws that held the factory speaker in. Then you have a way to reference the center with the bit and keep the cut round and not oval. Just my two cents worth! Good Luck!

chavez · RIP MHL 04/25/1958 - 01/11/2006

MobiusMan, absolutely. Personally, I would use a jigsaw or rotozip to enlarge existing holes.

oshensurfer · Posted: Mar 01, 2005 10:54 am Post subject:

chavez,
A jigsaw or rotozip with a guide or stop. I don't think I'd freehand it.