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Go Back   SailNet Community > On Board > Gear & Maintenance > Drilling Hole in Fiberglass Hull
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Thread: Drilling Hole in Fiberglass Hull Reply to Thread

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Topic Review (Newest First)
03-17-2011 10:37 AM
Liquorice To make a hole bigger with a hole saw, you use 2 hole saws.
1 the same size as the old hole, 1 the size of the new hole.
Nest them together on the same arbour ( some arbours won't take 2 hole saws, but most will. Harbor Freight sells one that's a little longer)
Use the smaller hole saw as the guide - real easy.
03-15-2011 07:00 PM
ereiss Thanks, just ordered my dremel. Certain that it will be a very handy tool to have. Thank you all for the advice.
03-15-2011 06:58 PM
mitiempo My Dremel sees a lot of use. A sanding drum on a Dremel flexdrive and a vacuum in the other hand to catch the debris makes the job not much longer than the time it took to write this.
03-15-2011 02:23 PM
eherlihy I suspect that the ˝" hole prevents you from using the center drill in the hole saw as a guide. Here is what I have done;
  • Use the 1" saw to cut a hole in a piece of ˝" plywood.
  • Then take the piece of plywood (with the hole) and fasten it so that the 1" hole in the plywood is over the ˝" hole in the hull (use clamps, and/or a helper).
  • Use the plywood as a guide for the hole saw.. Simply place the 1" hole saw in the hole in the plywood, and run it in reverse to cut through the gelcoat, then forward to finish off the hole through the hull.

Take care and good luck!
03-15-2011 01:26 PM
tommays If the hull is not to thick you would be amazed what you can do with a pencil and a dremel with a good bit

you can also glue a plug into the hole and then holesaw to the new size
03-15-2011 12:45 PM
Drilling Fiberglass (hope I'm not dredging up a too old thread)

I need to enlarge the hole that my head vent goes through (vent tube is only 1/2 inch and need to go to 1"). So, obviously well above the water line.

1. Any secrets on how to "redrill" the existing small hole to the proper size?
2. Is there a best type or brand of hole saw? I bought a set from Harbor Freight and I guess they are worth what I paid for them (not much). I would think a fine toothed hole saw would be best.
3. A real "duh" I certainly believe one drills from the outside in. right?

As always,thank you for your help.
08-29-2010 09:01 PM
mitiempo Hole drilling is pretty straight forward. If I am using a dremel to prepare the core for epoxy I use a vacuum held in the other hand and there is little or no stray dust.
08-29-2010 08:53 PM
sailingdog Really don't need a tyvek suit for this job... a full face mask respirator is probably a good idea and far more protective and comfortable than a half-mask and goggles.
08-29-2010 04:52 PM
mitiempo The hole should be the size required for the through hull. If the area is cored you want to cut the core back a bit and replace it with thickened epoxy, leaving the inner and outer skin intact.

A face mask yes, but a tyvek suit to drill a hole?
08-29-2010 04:30 PM
bluwateronly I don't think you want the hole in the getcoat larger than the size of the thruhull. If the area is cored and not pure glass then you want to prepare it, think dremmel tool here, their are so many threads you can learn from here, really, that can say it much beter than I.Backing plates are easy to make since you have the epoxy and some fiberglass.I would use 4200 when installing thruhull, uv. Take care and the hardest part is drilling the hole!
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