Cutting Hole in Fiberglass for Access Port: Methodology?

[PeteCress]

OC-1 cockpit, want to replace existing access port with a larger one.

Existing: https://photos.google.com/share/AF1Q...QzSWJaRW5TYzBR

Larger: https://photos.google.com/share/AF1Q...QzSWJaRW5TYzBR

This might seem like an inane post, but the consequences of error are fairly severe - as in a power tool catching on the material and spinning off into fiberglass that is not to be cut.

There is insufficient room for either a reciprocating saw or a jig saw.

I am thinking Dremel tool with a sanding head - applied so that, if it catches, it wants to spin away from the material instead of in to it.

That, plus time, patience, and care....

Does anybody have a better idea?

[mmd]

A straight router bit in a Dremel tool or similar will work better than a sanding head. Polyester resin and glass are hard - it will take a month of Sundays to sand your way through all that material, not to mention how many sanding heads you will go through. You will need a hardened carbide steel bit, not just plain tool steel. Make a template for your Dremel tool to follow, if you can.

This one is from Home Depot, but there are plenty other places to get them. Expect to pay $15-$25 for the bit, and it will be pretty much toast when you are done.

[navydog]

I think I would plug the hole and then cut if with a hole saw. either use a wood plug that snubs up just short of the existing hole or lay some impregnated fiberglass across the hole. when the glass hardens just mark the center and drill a new hole. It could also be done using a cutoff saw using a blade designed for metals.

[robm]

Use a jigsaw with a very short blade. Just break it off so it will clear. How much clearance below? Jigsaws have a 1" stroke, some are shorter. This won't work if the clearance beneath is <1".

There might not be enough side clearance to the baseplate to stay on the line. But this can be cleaned up later with the Dremel tool and router bit. There will be relatively little cleanup to do.

[PeteCress]

The clearance limitation is lateral, not up/down.

[PeteCress]

Sounds like I need to choose between the carbide router bit/Dremel tool and a 7" hole saw.

The downside exposures of the carbide router bit would seem to be burning the resin and the lack of room to accomodate a template.

The downside of the 7" hole saw would seem to be doubt as to whether the teeth can last long enough to make it through the glass.

The hole saw is attractive for it's controlability and lack of speed.

[Breakaway]

I'd get as much of it as I could with the jig saw and use the Dremel with a router bit for clean up--or even a bi-metal saw blade by hand. Make a handle out of scrap and duct tape ( Approved Use #1274 ). Stay inside your line. Not that I am encouraging sloppy work but the flange for the deckplate's mounting ring will cover most sins. Just be sure to leave enough material for the mounting screws.

Kevin

[navydog]

Sounds like I need to choose between the carbide router bit/Dremel tool and a 7" hole saw.

The downside exposures of the carbide router bit would seem to be burning the resin and the lack of room to accomodate a template.

The downside of the 7" hole saw would seem to be doubt as to whether the teeth can last long enough to make it through the glass.

The hole saw is attractive for it's controlability and lack of speed.

This is out of the boat right? just flip it over and you have all the access you want.

[Gib Etheridge]

Looks to me like you could do an excellent job of that with a trim router and a top bearing flush cut router bit.

[SMARTINSEN]

I have that little router, strong, smooth and quiet, perfect for this use, about $90 or so at Home Depot. Allow me to run out to the barn and measure the base to see if it will work for you. BRB...

...O.K.


The circular base is 1-3/4" radius.

[jackster]

A steady hand, a clear conscience, and a trim router!
But it is a freehand operation...no bearing on the bit!! Or adjusted up out if the way.
(Experience helps, too.)

[swoody126]

IT'Z SIMPLE!!!

get the 7" hole saw and cut a hole out of 1/2" plywood

take the cutout and screw it in place on the floor centered inside the pre-scribed 7" circle(shown in your pics)

the cutout will already have the correct sized center location hole in it

now just locate the pilot hole bit in the center hole of the cutout and keep on drilling

a really good quality hole saw will likely be all you can get in 7" size and it will cut one hole if you go carefully w/o overheating the metal

i use hole saws to cut thru HD p/u truck bumpers w/o any issues

have fun and wear full coverage clothing/eye protection, leaving no skin exposed(no need to ask why i say this)

sw

[Todd Bradshaw]

Do understand that gelcoat contains a high percentage of inert fillers, like talc and does not adhere to the lamination particularly well. It is often worth the trouble to cover the area with masking tape or similar and then make your cuts through the tape to prevent the gelcoat from delaminating and flaking off around the cut lines. Also keep in mind that cutting a foot or two of fiberglass is usually enough to take the teeth completely off of the average sabre saw blade - so whatever bits or blades you use will most likely be worthless after this project.

[openboater]

Maybe drill 80 quarter inch holes around the inside of the circle, then cut hole to hole using a jigsaw blade in a handle ( by hand). Sand ,grind or file what's needed to get a good fit. Good luck. What's the OC-1 ?

[Canoeyawl]

For little money you can buy a carbide burr esecially for cutting fiberglass.
You can mount it in a router or use it freehand in a die grinder (I have done both, they are pretty controllable by hand)



http://www.carbideprocessors.com/fib...yABEgJ4afD_BwE

[DeniseO30]

just mark right size with a marker and saw it out by hand! fine tooth push ..not pull, ya really don't have clearance for a even a small router.

put tape on the gel coat.. it tends to peall and break off

[Woxbox]

I'm with the do-it-by-hand school of thought here. I've cut lots of holes in fiberglass and there's no need to overthink it. Just do it, like the man said.

Here's a tale: When I got my F-27 trimaran, designer Ian (RIP) Farrier in the extensive owners guide suggested carrying a drywall saw in the emergency kit so that if the boat flipped, the saw could be used to cut an access hole big enough to get back inside (the inverted boat would float quite high). I was skeptical, but I bought a top-notch drywall saw and tested it on a panel of fiberglass that I'd cut out of another boat and had sitting in the basement. Sure enough, I was able to punch the saw (they have sharp tips on them) through the glass and then by hand cut away at a pretty decent rate.

So if a drywall saw will do it, clearly most any other cutting tool will. And if you do it by hand, the saw is moving too slow to mess up.

[DeniseO30]

I'm with the do-it-by-hand school of thought here. I've cut lots of holes in fiberglass and there's no need to overthink it. Just do it, like the man said.

Here's a tale: When I got my F-27 trimaran, designer Ian (RIP) Farrier in the extensive owners guide suggested carrying a drywall saw in the emergency kit so that if the boat flipped, the saw could be used to cut an access hole big enough to get back inside (the inverted boat would float quite high). I was skeptical, but I bought a top-notch drywall saw and tested it on a panel of fiberglass that I'd cut out of another boat and had sitting in the basement. Sure enough, I was able to punch the saw (they have sharp tips on them) through the glass and then by hand cut away at a pretty decent rate.

So if a drywall saw will do it, clearly most any other cutting tool will. And if you do it by hand, the saw is moving too slow to mess up.

Another very effective way would to be drill a circle of small holes and then saw between the holes( connect the dots)

Sent from my LG-M430 using Tapatalk

[Alan H]

Maybe drill 80 quarter inch holes around the inside of the circle, then cut hole to hole using a jigsaw blade in a handle ( by hand). Sand ,grind or file what's needed to get a good fit. Good luck. What's the OC-1 ?

This....

[JimConlin]

[P.I. Stazzer-Newt]

Tell us more about the boat.

Pictures would be nice.

[PeteCress]

Tell us more about the boat.

Pictures would be nice.

One-man outrigger canoe ("OC-1") with an 8-meter roller-reefing sail and a twist.

The twist is that, on ama-side tack, the ama is held down by a foil instead of somebody hiking out.

https://www.sailingworld.com/sites/s...?itok=URNFPDjn
https://youtu.be/MrF_dEmX8x4 (fast-forward to 01:30, then to 02:35)
http://www.raptor-uk.net/guests/stever/comments.html


EddyVB's Rudder at mooring stays up.jpg
UK Bruce Foil Line 2.jpg
Raptor16 under sail - Hawaii.jpg

Raptor 16 - Paddle Mode.jpg
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Only 62 made, and I wish my instance looked half as good as the ones in the pix above:
Raptor 16 - New Home2.jpg

[Breakaway]

Originally Posted by navydog

This is out of the boat right? just flip it over and you have all the access you want.

It's a hollow part. He needs the hole in the top to access the inside.

Kevin

[SchoonerRat]

A hole saw is the only thing I would even consider for this job.

Find a piece of scrap wood about 3/4" X 3" X 10" and slide it beneath the deck. Secure it under the deck by screwing through what will be the waste of your cut so that you can put the pilot drill of the hole saw solidly in the wood when you make your cut. That thin FRP deck will not be a problem for the hole saw. I've been able to make 3 cuts or more through similar material before tossing a hole saw. Use caution. When the hole saw breaks through the glass, the waste and the scrap wood will spin with your drill. If possible, the scrap wood should be short enough that it doesn't bang on the hull when it spins. You won't be able to get your finger off the trigger quick enough. You might want to do some padding, or bracing, or gluing to prevent the scrap wood from doing any damage. A little panel adhesive will stick it to the underside of the deck while still allowing you to easily remove it.

This will give you a clean round hole that will need no further clean-up or grinding. The time and grief that you'll save will MORE than make up for the cost of a "disposable" hole saw, and hole saws can be sharpened (might cost more than a replacement blade).

[jpatrick]

There have been several valid methods of cutting presented. Any of these will work. I'll add to any of them: Have an assistant there to hold a vacuum close by the cut to suck away the awful fiberglass dust. This should be a vac fitted with a hepa filter. The business end near the cutter ought to be plastic, not metal.

Jeff

[CundysHarbor]

A hole saw for such a large hole is going to be expensive. It will also require lots of torque. If something jams, large scale problems may ensue. Yes, I speak from experience using a 3 inch hole saw on fiberglass. I'd drill lots of small holes and connect them using a hacksaw blade - as has been mentioned several times above.

[Paul356]

I'd use a coping saw. I.e., do it by hand. And Maybe drill a series of holes like someone suggested, then connect them.

[willmarsh3]

I've cut 6" holes in wood and 5 1/2" holes in steel using a hole saw with a regular electric drill. The key is to go slow and really hold the drill firmly. I second the idea of mounting a piece of scrap wood behind the hole. Screw it in to holes drilled in the part of the fiberglass to be removed. This will hold the hole saw steady while it cuts.

[PeteCress]

Wound up using this bad boy after a little testing to make sure it would cut smoothly.

• Dremel tool at max rpm,
• Both hands on the tool
• Light touch,
• Went slow,
• Held it so that if something caught the tool would bounce away from the material instead of clawing it's way into it....
• Maybe a half inch at a time to minimize heat....

No sign of cooking the resin and the gel coat never felt warm to the touch.
Raptor 16 - Dremel+Bit.jpg

Trimmed the port's flange to make it fit in the flat area:
Raptor 16 - New access port installed.Closed.jpg
Raptor 16 - New access port installed.Open.jpg

[jackster]

Nicely done!! Cheers!

[swoody126]

BUENO

sw

[Gib Etheridge]

That cutter sure looks dull.

You must have good strong steady hands to do such a clean job.

[Lugalong]

Best tool of all for cutting holes in GRP is a compressed-air powered reciprocating hacksaw.
The hacksaw blade can be ground to a very short sharp point, for penetration anywhere in the panel, and can also be ground to a small enough size for small hole/ tight radius, or left as they come, for bigger holes.
Dust from sawing is also kept to a minimum

[PeteCress]

That cutter sure looks dull.

When I started, it was new and, IIRC, significantly larger - supporting MMD's and Todd's observations that whatever tool were used would be toast afterwards...-)

[mmd]

Sometimes I feel like Rodney Dangerfield around here... <grin>