Best tool to use to cut fiberglass?

Best thing I have found is a nice sturdy pair of scissors.  Just be aware that FG is rough on cutting edges.

Swamp

Edit:  Wait do you mean FG cloth or FG composite (resin plus ply/foam/glass)?  If for composite then it depends on how "nice" of a cut you want.  For rough but very fast work I like an air hammer with a cutting chisel in it.  Otherwise an angle grinder with a cutting wheel works very well and still quickly, but you do burn through wheels.  I just started to use a cheap vibrating cutter with a diamond blade in it so far it is the best thing I have found for controlled clean cuts but it is slower.  The last is great for making flush cuts BTW.  Time will tell if I like the vibrating tool in the long run.

Swamp

 

Sawzall.
If your careful you can literally le the blade ride against the hull shell as you cut the bench seats out, greatly minimizing later grinding work.

 

i use an air powered hacksaw - "metal" blades - this works great for non cored thin glass skins

cored glass - i call them "dumpster saws",a "skill saw" circular saw - works great - the glass dust will kill it

cutting stringers,bulkheads - sawzall - i have a milwaukee - if i can't kill it - it won't break - just like the smart phone i have a "rugby smart"...

 

It depends on what your idea of "best results" is. For me, I like very little FG dust and a clean cut, so I'd use a multitool with a diamond or carbide grit blade. If you could care less about dust, a 4" grinder fitted with a thin kerf cutoff wheel would cut em' like butter.

 

Sawzall (preferrably a corded one), Skillsaw, and a Jigsaw...

The jigsaw will help you start a cut in some strange areas, the skillsaw is good for long straight cuts, and the sawzall is good for getting up close against the hull like cut runner said. Just make sure you wear eye protection

 

One of these types:
http://www.rockler.com/product.cfm?page=30593&site=ROCKLER
Low dust and clean cuts

 

Lots of ways to ruin your tools hacking on fiberglass.

Milwaukee makes the toughest 'sawz all' ever. It will outlast the others by far.

I have tried and killed off several (name brand) multi tools...of the affordable variety, I think the BOSCH is the best, great sanding pad attachment (bonus). $149 to $160. Not bad for a tool that you will use somewhat infrequently.

I wish we could all afford pneumatic equipment in our home shops. Sanders, buffers, cut-offs, spray rigs...oh well.

 

for fine work, the multi tool is the way to go, hard to fiu, but sawsasll for cutting out large portions like benches decks etc. saws all is best then finish up with the multi tool. Standard metal blade works just fine.

 

sawzall - you can "bend" the blade as you cut,"riding" the hull...after they're cut out,grind the area,lay some matting over it,to a level slightly higher than the surrounding area,after it kicks,grind it and fair it...

sand the inside out,use a good epoxy primer-2 part,let that kick,sand it,roll the inside out in awlgrip with grip tex - done !