Best way to cut fiberglass

[jbpatents]

Forgive me if this was discussed already, but I tried to search the forum and didn't find it. I saw many mods that require cutting into fiberglass. Frankly, the cuts I've seen look rather ugly. I'm sure there's a "best practice" for cutting fiberglass so that at least the cut is straight. I would appreciate any suggestions. Thanks,

[Chinook]

I've mostly used a sabersaw (jigsaw), which works fine if used with care. I pad the bottom plate of the saw with masking tape, to avoid scratches. The blade is important. Best is a fine chisel tooth blade, with no set. That will give a clean cut. If you use a blade with a set, it will tend to chip the edges of the cut. There is a lot of friction in the cutting, and blades will dull quickly. Expect to go through several if you're making a big cut. If you have room, a router with a trim cutting bit will do a nice job. To use the router, you'll need to be able to clamp an edge guide or template, which can be difficult to arrange. I used the router to cut a circular hole in the lexan window in the head, when I installed a solar Nicro vent fan there.

[yukonbob]

Dremels and grinders work well but as Chinook says the type of blade is what's really important

[topcat0399]

Be aware - anytime you put a rotary tool to fiberglass be prepared for the AWFUL fiberglass
dust that gets everywhere and causes all kinds of itching.

[RobertB]

Best to use a multitool (Fein is the original, many copies including my new Milwaukee M18 cordless version) and hold a vacuum cleaner to the cut. No dust and exact cut.
http://www.amazon.com/Fein-72293768090- ... B00B4OCTX2

[jbpatents]

Thanks Robert, holding a vacuum is a good idea to avoid the mess. I never used this kind of tool - it just never seem to me to be good for anything. So which blade would you use? And how would you make sure the cut is straight. To be more specific, the first thing I'd like to do is make access hatches to the storage so I don't have to lift the cushions to reach the storage.

[kmclemore]

I've done a lot of work with fiberglass over the years, both on boats and cars, as many here know. Here's a couple of tips beyond those stated already...

- Use a good dust mask... ALWAYS. The stuff is deadly. Change to a new mask often if you're working with it for a while.

- Wear good, full eye-cover safety glasses. The kind that look like a snorkeling mask work best.

- I don't care how hot it is.. wear a long sleeve shirt and long pants... but try to cut 'glass on a cool day to avoid the fibers sticking to your sweaty skin.

- Before dressing, dust your skin with talcum powder - it will help prevent the fibers from sticking to your skin and getting into your pores (from whence comes the terrible itching). Pay particular attention to any exposed areas like face and also to any joint areas like the inside of elbows, backs of knees, neck, etc.

- Clean up immediately after cutting, using a good bag-type vacuum and a brush. Vacuum yourself off, too.

- Immediately take a COLD shower afterwards... NOT hot. This closes the pores and prevents entry of the fibers as you wash them off.

- Dump your clothes right into the washer and wash with plenty of soap. Best to wash them without anything else in there, too.

[kmclemore]

As far as cutting, I find using a Dremel tool with the router attachment (aka "565 Multi-Purpose Cutting Kit")and one of those carbide "RotoZip" cutter bits works great. The Dremel is easy to control, you can easily see what you're doing though the attachment's openings, it leaves perfectly smooth edges, there's nearly zero gel-coat chipping and the tool takes it slow enough that things can't get too out of hand too quickly. If you want it particularly straight, fasten a straight edge (can be just a piece of wood or a long level) to the work and then run the Dremel down the edge... the outside of the router attachment will slide nicely down the guide. The Dremem attachment also allows you to control the depth of the cut, particularly important when working on bits that have other things behind them - like the boat's hull!

[RobertB]

Thanks Robert, holding a vacuum is a good idea to avoid the mess. I never used this kind of tool - it just never seem to me to be good for anything. So which blade would you use? And how would you make sure the cut is straight. To be more specific, the first thing I'd like to do is make access hatches to the storage so I don't have to lift the cushions to reach the storage.

After owning one of these (now two) tools, I wonder how I ever made difficult and accurate cuts. Yes, there are many tools that work (I probably have most of them) but this one is unmatched for ability to just cut where you intend. Straight cuts can be with a steady hand or you can clamp/tape a guide in place. Use the blade that fits the cut you intend to make. The standard eCut blades (bimetal blades) should work. you can always clean up you cut with a file or sandpaper.
If you are using commercial covers (and I am looking to make the same mod), your cut will be covered by the hatch structure).

[Highlander]

If I,m cutting from the outside I install a plastic shopping bag around the cutout area with masking tape that will catch most of the dust , but it is impossible to catch it all I usually duct tape a shop vac hose end as close too the cut as possible to help catch the dust between the liners , then shop vac around the cutout along the cutout edges then wash everything down after the job is done I usually vac the whole boat & complete inside wash down sponge all carpet with wet sponge & lavender scented pine-sol

Here u can see 2 plastic bags masking taped one on the cabin roof liner where my dorade box vents went & the other opposite the head where I installed two 3x10" port lights
http://i844.photobucket.com/albums/ab1/ ... f89b6f.jpg

here,s how I started the cut out drilled 4 holes where the corners were & 2 hole,s where the drains go , I used the port light outer ring as a temp. plate for my cutout & drilled out all the mounting holes @ the same time
http://i844.photobucket.com/albums/ab1/ ... fb3676.jpg

masking tape around the cutout helps prevent marking the gel-coat
http://i844.photobucket.com/albums/ab1/ ... 9eb313.jpg

Here,s the finished install in the head & opposite side
http://i844.photobucket.com/albums/ab1/ ... 7032a6.jpg

http://i844.photobucket.com/albums/ab1/ ... 9ab2d5.jpg

Here,s the aft opening ports
http://i844.photobucket.com/albums/ab1/ ... 74e2de.jpg

http://i844.photobucket.com/albums/ab1/ ... 606758.jpg

outside aft port before clean up
http://i844.photobucket.com/albums/ab1/ ... 31aa2a.jpg

I drilled 2 very small holes in the out ring while duct taped to the cabin hull then took the ring inside & fitted it to the cabin wall with 2 very small screws to make sure they where cosmetically correct & aligned with the inside liner , once that I was satisfied with the fit location I marked with black liner my cutout , & drill locations were drilled
http://i844.photobucket.com/albums/ab1/ ... b19045.jpg

Cabin roof cutouts for dorade boxes
http://i844.photobucket.com/albums/ab1/ ... b33025.jpg

notice I did not cut out the re-enforcement ribs
http://i844.photobucket.com/albums/ab1/ ... 67e920.jpg

http://i844.photobucket.com/albums/ab1/ ... f7ecd0.jpg

http://i844.photobucket.com/albums/ab1/ ... 9c6ab7.jpg

http://i844.photobucket.com/albums/ab1/ ... fca6e8.jpg

http://i844.photobucket.com/albums/ab1/ ... cf295f.jpg

as u can see I have done extensive cutting into my boat so if u r unsure if their is something u need to watch out for in a certain location just ask before u cut
http://i844.photobucket.com/albums/ab1/ ... da5e21.jpg

Like when I cutout here for my cabin hatches the bottom cut is very close too the ballast tank so just saying double check before u cut or ask here & maybe someone can help u out u did not say where u were planning on cutting !!
http://i844.photobucket.com/albums/ab1/ ... 836f0a.jpg

I used a holesaw for small tight corner & a short jigsaw blade for bigger corners & a 4" grinder with a very thin cutoff blade , I now have of of these new style cutters mentioned above but yet to try it out , but that should not be too long LOL
Hope this helps u out , hope I did not take over this post was not my intention

J
PS all the above posts before mine r all good advise

[kmclemore]

One other note... on any cuts, make sure the corners are rounded (radiused), NOT at a sharp angle. Sharp angled corners can lead to stress cracks radiating out from them. This is another reason for using the Dremel with the round bit - it always leaves a rounded corner.

[RobertB]

Ditto on the round inside corners, I typically drill these with the largest bit that is appropriate and then cut between the holes.

[Russ]

I have learned so much from the folks on this forum. As well as increased my tool box.

--Russ