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drilling fiberglass?


Arctic Slalom

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planning to change out my original 3" vent covers (4) on the back of my boat.

bought these vents. they have (4) holes my current have just (2) on the sides. I should be fine just to use masking tape and predrill into my fiberglass prior to adding the (4) #8 screws, correct?

...I just don't want to crack the gelcoat!

any thoughts would be great.

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Tape

Run drill backwards until thru the gel (you can run it in reverse the entire time).

Chamfer/Ease the edges with either a slightly larger drill bit or a little sand paper to prevent spider cracks.

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martinarcher
Tape

Run drill backwards until thru the gel (you can run it in reverse the entire time).

Chamfer/Ease the edges with either a slightly larger drill bit or a little sand paper to prevent spider cracks.

Right on.....these holes are for #12 screws for underwater LEDs. Notice the chamfered edges.

post-7666-1250606495_thumb.jpg

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  • 2 weeks later...
Tape

Run drill backwards until thru the gel (you can run it in reverse the entire time).

Chamfer/Ease the edges with either a slightly larger drill bit or a little sand paper to prevent spider cracks.

Plus1.gif Drilling the holes running the drill backwards in the beginning is a great tip...worked awesome when I installed my tower.

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I'd like to piggyback on this thread for my project. I need to drill two through-hull fittings for drain and vent lines. I have spade drill bits, but I'm guessing that a hole saw would be better?

Also, the through-hull fittings (like this: http://www.bakesonline.com/detail.aspx?ID=1106) have 3/4" hose barbs, but the threaded portion looks larger than that. Anyone know what size hole I would need to drill? Looks like one inch maybe?

thanks,

Mike

Edited by MadDogMike
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Tape

Run drill backwards until thru the gel (you can run it in reverse the entire time).

Chamfer/Ease the edges with either a slightly larger drill bit or a little sand paper to prevent spider cracks.

Plus1.gif Drilling the holes running the drill backwards in the beginning is a great tip...worked awesome when I installed my tower.

Drilling a smaller pilot hole also is a good idea. For the chamfer, I went to ACE and bought a couple of counter sink bits. I drilled through the gunnel with the one that was 1/2" for my new tower base. It worked like a charm.

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guys,

thanks for the tips.

i got em all (4) installed and they look great.

the outside diameter of the new vent covers was just barely enough to cover the old screw holes....it was wicked close, like less than an 1/8" of play.

also, the part which I ordered from west marine DOES NOT have a flange on the back side for my vent hose to connect to....evidently it's a flush vent?! I talked to the sales rep about it and he thought it had a partial tube extension to hose clamp the vent tube on, he was wrong. anyway, a little epoxy and griding down the the old vents flange solved that.

later,

CR

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