Drilling Fiberglass??

Discussion in 'Fiberglass and Composite Boat Building' started by Capt. Chris, Nov 15, 2007.

  1. Capt. Chris
    Joined: Feb 2005
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    Capt. Chris Junior Member

    I was recently asked to help install new electronics on a friends boat, only because he knows that I can fix fiberglass. I think avoiding the fixing part of the project is always the best coarse, so what's the best way to make nice smooth openings in this cored helm? Also some will be holes and some flush mount. Thanks for any imput! Chris
     
  2. marshmat
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    marshmat Senior Member

    What kind of core / how thick are the skins?

    I have tried quite a few power tools for cutting and drilling cored laminates. Most don't like it. Although to be fair, most of that work was either on heavy, cored hi-temp moulds, or on structural carbon fibre.
    - Angle grinders - burned up one (literally) on cored glass in a matter of minutes, best to use the highest power motor you can get and a thin-kerf abrasive cutting disc.
    - Sawzall or jigsaw - Bimetal or HSS blades don't last long on fibreglass, carbide-tipped might stand a chance.
    - Hole saw - again, bimetal or HSS teeth get worn to stubs in no time.
    - Spiral saw - slow going, but with the right bit might have a chance.

    Assuming you can cut a straight line, the hard part is twofold:
    (1) don't burn the laminate by overheating the cutter
    (2) don't chip or splinter the surface

    The burning problem is avoided by going slowly and doing cuts a little at a time, letting the tool cool down. To avoid chips and splinters, try laying an adhesive tape over the cut before marking the line; this can help protect the brittle outer gelcoat. Finer cutters or abrasive cutters are less likely to cause chips.

    You will have to seal the core in the cutouts against water. Otherwise, spray or rain will trickle in under the gauges, get absorbed by the core, and attack the laminate. Unsealed, exposed core edges, without fail, become a Very Bad Thing in a couple of seasons.
     
  3. charmc
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    charmc Senior Member

    I agree with Matt's thoughts. I ususally went with low cost hole saw and jigsaw blades, as I found that even the better ones became dull fairly quickly. Wasteful to turn blades into disposables, but it was a choice between high or low cost disposables. Fine teeth are very important, unless the edges of the hole will be covered for a good distance beyond the cut. Fine teeth will help prevent chipping the gelcoat, and masking the line to be cut does help.

    There are, I'm sure, high end blades that are designed specifically for holding up while cutting glass and carbon fibers, but they will be very pricey.
     
  4. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    If the surface is reasonably flat or a simple curve , you can use spray adhesive to hold down a piece of thin plywood (I use 1/8 and 1/4"). If using a hole saw, place a couple of screws inside the cut line, but not in way of the pilot. This will hold down the plywood tight without adhesive and protect the laminate. Carbide blades last longer, but will die just as uneasy a death.

    Routers used with a template, laminate trimmers with the same and Roto Zip saws also work reasonably well. The trick is to maintain enough pressure between the protecting piece of plywood and the laminate. On compound curves you don't have as many options. In most cases I use a high speed pencil grinder with carbide rotary cutter on these areas with tape to help the chip out issue. A good metal cutting blade in a jig saw, can do a pretty fair job if you go slow and work carefully.
     
  5. fiberglass jack
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    fiberglass jack Senior Member

    I tend to use a air powered die grinder with a 1/4 inch diamond striaght router bit works great, nice clean cuts. I also use a cordless rotorzip when out in the marinias with the same tip costs about 50 dollars but will last a long time, the general purpose blades will work aswell but tend to chip what i like to do is cut the opening smaller then needed this way you can get some practice , jigsaws works good, once had to cut a hole and all i had was a hand drill and a hacksaw blade it was a little bit like joining the dots
     
  6. KnottyBuoyz
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    KnottyBuoyz Provocateur & Raconteur

    I've had good luck with the jig-saw and "plastic" cutting blades. Can't remember where I got them but they're specifically designed to cut plastics. Had a few to cut some lexan and they worked great on fiberglass. I would think most blade mfgrs would have something similar. Other than that I've only used the trusty dremel tool which is much messier, filter mask req'd.
     
  7. Fanie
    Joined: Oct 2007
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    Fanie Fanie

    Work with the fiberglass like you're working with metal.
     
  8. Capt. Chris
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    Capt. Chris Junior Member

    Looks like the flat helm is white gelcoat with mat/ cloth then a plywood core and some woven roving on the inside. The total thickness is about 3/4". I like the idea of using cheap hole saws, I'm not ready to sacrifice my own good ones. I'll tape off, go slow, use the die grinder to clean up edges and tell my freind to look the other way when the cutting starts!

    Thanks for the input!
    Chris
     
  9. Fanie
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    Fanie Fanie

    Captain Chris, I have made a few holes in fiberglass using hole saws. The only ones that last are the good ones. Like I said if you treat it as steel you're going through, the hole saws can be re-used - slow turn speed and avoid heat.
     
  10. the1much
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    the1much hippie dreams

    the only thing i could add would be , take a razor to your hole,,just outline it, and dont try going to deep, just enough to score the gel coat
     
  11. ondarvr
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    ondarvr Senior Member

    You can buy grit edge saw blades and hole saws, the saw blades are easy find, the hole saws are a little tougher to get. Carbide tipped holes saws work very well and last much longer than typical bi-metal ones.

    If you use a hole saw (tooth type), run it backwards at first to start the hole, this will help to keep it from chipping the edge. Sharp hole saws tend to grab when they first make contact with the surface when run in the correct direction, so be careful.

    The type of gel coat and its thickness will also affect how the edge chips, so do a few cuts inside an area that will be removed to see what works best for you.

    You can make a templet with wood and cut all the holes in it prior to doing the dash, this way you can see exactly how everything lines up before ever starting on the boat. You can then use it to mark and cut the dash, tape helps too.
     
  12. Moosemiester
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    Moosemiester Junior Member

    Yet another way...

    I have good luck with a Roto-Zip (Also known as a plunge cutter) with a carbide bit. Very tricky to use, because the tool design makes it difficult to hold steady, but with practice it works exceptionally well.

    Mine is a Bosch unit from Home Depot. Funny thing it's useless for wood and drywall which is what it is sold for...
     
  13. Capt. Chris
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    Capt. Chris Junior Member

    I just tested reverse the hole saw method on some scap gelcoated cut-offs from "Project Topaz" and it works pretty good. Slow is the deal there, I ran the drill fast on foward, just to see what would happen... yeah chip city! My main concern was chipping on the holes for the round guages. The large square cut-outs I'll chicken out and just cut undersized openings then use the die grinder to open them up.

    Many thanks for the Input!!

    Chris
     
  14. Fanie
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    Fanie Fanie

    You can use a jigsaw with a steel blade as well, again slowish blade movement, preferably a jigsaw with a speed control. Masking tape the area so the jigsaw won't scrape the surface. Don't undercut too much, 1 to 2 mm should be ok.

    Pneumatic tools work best since they don't tend to force their spindels like electric tools does, instead they just brake or halt untill released. Much safer and less chance ofbuggering something up.
     

  15. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Since your gauge panel is reasonably flat, use the plywood (or solid wood) method I mentioned. It works great and you'll have no chip out, so long as the wood is in very firm contact with the gauge panel. Try this on some scrap 'glass, it works well. I prefer to use a couple of screws, within the diameter of the hole, when using a hole saw. It makes quick work of the task and holds wood firmly.
     
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