best way to cut fiberglass.

S

starcrafttom

Active member
I have several projects this weekend to complete that involve me and power tools. I have to cut thru the front deck for the windlass and thru the v-berth bunk glass for biggger hatches that just came in. What is the best way to cut. I have read that I should cover the glass with tape to keep it from chipping.

I have seen pictures of folks using both jig saws and rotor type saws. Any opinon on which is better? any tips on making a smooth cut? What type of blades should I use for each? once I do something the first time I am dam near a expert, but I hate doing it the first time.
 
I have used a jig saw, which works great but you'll burn through the blades very fast. I always tape both sides of the cut (if the bottom is accessible) to keep the cut clean.

Outside of burning through the blades (it wears the teeth right off), the jig saw works great - slow, controllable, and clean cut.

Have a nice day.
 
Tom, if you use a jigsaw, use a metal cutting blade with very fine teeth. If you can find a hardened one, it'll last longer. Be sure to wear a mask if you have one, the dust is very fine and not good to inhale. Drill holes at each place where you have to make a sharp turn, that way you'll be cutting straight, or nearly straight lines.

Charlie
 
I like the way Thomas said he'd be dam near an expert - he must be like me - SHE'd be standing over my shoulder telling me where I screwed up - SHE must be an expert - and I'd be "near" and expert ...
 
I'm a believer in the circular hole saws for cutting larger holes in thick fiberglass. They make an accurate clean cut of exactly the dimension you want. Jigsaws will do the job but the up-down motion increases the likelihood of splintering. A moment's inattention can make for an embarassing "whoops!" moment and a new problem of repairing said fiberglass. The range of motion on most jigsaw blades is about 1"-1 1/4", the deck is about 7/8" thick so you are effectively moving the blade about 1/4" up and down in the cut area. If you choose to go with a jigsaw there are blades designed for fiberglass/tile, etc. They are the toothless carbide ones with what look like heavy grit brazed to the blade.
 
Thanks guys, anyone use the rotor saw? I know that who ever cut out port holes used one. Colobear, I have to much glass to use just a hole saw. I looked at your windlass model, which just needs one big round hole, and compared to mine which needs a much larger hole that is not round. the V700 has the chain falling Thur the motor mount as where the older sprint 600 does not. the motor and the chain go Thur the deck in different places.
 
Tom, from my posts about removing the bulkhead on my 16 is the following


DeWalt DW660 Cut Out Tool. About $40 on sale last month at the hardware store. There are a couple of different types of bits. One for drywall and one for fiberglass and other light stuff. I went through one bit for the whole job.
Click to expand...

I will be home from Maui on Thursday it you want to use it. I only used one bit for each of Pat and my 16s.
 
Dave, I did not follow that thread and will go back and look at it. Was the saw hard to control? I have one that I cut some wood with once and I may not have had the right blade, but it jumped around and was a pain. I may not have been using it right.
 
I found it fairly easy to use and it cuts a pretty accurate straight line. It is sort of like a small hand held router. I cut the whole bulkhead out in about 20 minutes. I am guessing the linear cut was about 6-7 feet. I penciled in the line I wanted to follow and just followed the line. Dust mask and ear protection should be used.
 
This what I use
Call it a Zip saw; Roto saw, what ever, it’s one of the best investments in my tool collection. Always use a fresh blade and cover the area you’re cutting with blue masking tape, unless it’s a razed diamond no-slip service.
Best part is you don’t have to turn the saw as you follow the cut. I’ve used to cut-out the polycarbonate in my hatch cover for vent, holes in dash for instruments, and other projects around the house.

Tried to post picture for album but having problem with that. Done many time but something up???
 
I usually use a saber saw--with bimetal blades, and use duct tape over the glass. I probably have at least 15 hole saws, and they seem to last very well--certainly great for things like the anchor windlass, guages, thru hulls etc--or rounded corners in straight line cuts.

I have also used the rotozip on some cuts. I find it a bit hard to control, and you have to go very slowly. I like to make a fence--as with a router to give a straight cut. This is fine if there is a way to secure the fence.

There is also the recropicating saws. Fein makes them, and Dremel is making them now. They will cut flush, have some very tough blades and are easy to control.

I have tried the diamond and carbide grit blades, but prefer a good quality bimetal blade. The bimetal are faster. A lot depends on how thick the glass is, and how much you have to cut. If I ever get around to putting in the second water tank in the Tom Cat, I will be using the recropicating saws.
 
Some general tips:

If at all possible, leave a radius in the corners rather than square corners. Square corners have a tendency over time to develop stress cracks in the gelcoat.

When I use a hole saw on fiberglass, I start off with the drill in reverse and let it dig down about a 1/16th to a 1/8". This seems to prevent chipping the gelcoat. I do this on both sides of the hole when access is available from below.

Don't forget to treat the balsa before installing your fixtures.

Don't cinch down the fixtures for 24 hours. This will allow the sealant to form a gasket.
 
ok I did some cutting today. First I had to get the old hatches out. I am replacing them with bigger ones. Nice hatches and easy to get out because the factory did not use anything to hold them in but screws. a little 4200 would have been nice.

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Here is a pic of the old and bigger new hatches. After I got the old ones out I taped off the cutting area.

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Then I get the tools ready. Dremel tool brand zip saw, tape, straight edge for a guide and a vacuum. The straight edge was a real help. being I was making the hole bigger I was able to get clamps on it. On one side the clamps would not reach so I just taped it in place. the corners I had to free hand but it worked out well.

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And of course you have to have safety gear.

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I used the vacuum to suck away the dust as I cut and it worked very well
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I think it came out pretty well
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