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Old 29 June 2014, 13:38   #1
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Drill bit for hull drain?

What would be the best type of drill bit for enlarging an existing hole in the transom of my RIB? The boat is a Zodiac Hurricane 440 so fiberglass with wood core. Right now I have two hull drains that are about 3/4" dia and are unlined so water can to the wood. I want to enlarge these and seal them with new 1" hull drains.
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Old 29 June 2014, 14:08   #2
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Hi, you need one of those stepper drill bits, they are cone shaped and range from about 10mm upto 35mm,drill from both sides and a perfect fit should be possible

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Old 29 June 2014, 14:56   #3
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Quote:
Originally Posted by headdamage View Post
What would be the best type of drill bit for enlarging an existing hole in the transom of my RIB? The boat is a Zodiac Hurricane 440 so fiberglass with wood core. Right now I have two hull drains that are about 3/4" dia and are unlined so water can to the wood. I want to enlarge these and seal them with new 1" hull drains.
Drill it oversize with a hole saw. You can fill the existing hole (flush) with a bit of wood to facilitate the hole saw drill bit when drilling.

Then fill the oversize hole with fibreglass.

When dry drill the correct size through the fibreglass with another hole saw.



This process will ensure that the wood core is properly protected.

This video may also be of help

[video]
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Old 30 June 2014, 10:48   #4
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I assume you are talking the trunk drains o nthe transom as opposed to a tiddly little thing with a twistlock plug in the floor to stop it filling with water when it's on the trailer kind of thing?

IF we atre talking the transom drains:
One thing to be careful off is that the diameter of thiose holes is flush / tangentical with the floor of the boat - going in witha cone cutter will expand the diameter in all directions, so you may end up creating more problems than you solve.

At least with a holesawyou can tack a bit of ply across the old hole, then "pilot hole" it, so you can then drill in from the outsode (if you have one of these "cartridge" holesaws) - not an issue if you have the "can" type) where the O/D is the teeth (i.e no carrier protruding)
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Old 30 June 2014, 11:05   #5
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I assume you are talking the trunk drains o nthe transom as opposed to a tiddly little thing with a twistlock plug in the floor to stop it filling with water when it's on the trailer kind of thing?

IF we atre talking the transom drains:
One thing to be careful off is that the diameter of thiose holes is flush / tangentical with the floor of the boat - going in witha cone cutter will expand the diameter in all directions, so you may end up creating more problems than you solve.
Wouldn't that be true in either case?

jky
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Old 30 June 2014, 11:12   #6
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Tack on a sheet of plywood to the interior of the transom. The hole saw will wander all over without a pilot hole. Then use a hole saw from the inside out so the bottom of the new hole aligns with the floor (and doesn't gouge the floor)
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Old 01 July 2014, 13:38   #7
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Tack on a sheet of plywood to the interior of the transom. The hole saw will wander all over without a pilot hole. Then use a hole saw from the inside out so the bottom of the new hole aligns with the floor (and doesn't gouge the floor)
You may be able to use a larger piece of plywood and just clamp it to the transom firmly. That way no other penetrations are made.
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Old 02 July 2014, 14:37   #8
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The hull is split in two half’s length ways below the deck (Looking into the hull through the drain with an inspection camera) and appears to be full of foam other than a pair of small cavities at the rear of the hull against the transom. Each cavity has a approx. ” drain coming out of the transom below the water line. These holes are not glassed/lined and the wood is exposed to water. There is no deck access to these cavities. I’m thinking that I may need to install a pair of inspection hatches in the deck to access these drains to repair them properly. I want to dry and seal up the exposed transom wood and install properly installed drains.

Or would it be better to fill and seal the drain holes and just use the newly installed deck inspection hatches to remove any water when it does get in?

I don’t see any way of making sure the current drain holes are repaired properly without installing the hatches in the deck, or at least cutting through the deck and resealing the deck after the repair.

Longer term would it be worth installing a few hatches along the deck and trying to remove as much of the foam as possible or do I keep it in place?
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Old 02 July 2014, 14:58   #9
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Not sure I'm visualizing your hull correctly, do you have any pictures you could post?

You don't want to be ripping out deck foam without replacing it with plywood (a big job).
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Old 02 July 2014, 15:13   #10
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I'll try to get some photos up here in the next couple of days.
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