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  #21  
Old 04-16-2013
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Re: Tips for cutting hole for flush mount through-hull

Quote:
Originally Posted by ccriders View Post
Did you happen to take photos to document your process? I guess you used one of those pistol grip hack saws, is that right? I'm faced with this problem right now.
Thanks
CC,

That is one install I didn't photograph. I can take a picture of the finished drain if you like. Yes, that is the saw I used. It is short and worked well. It was really as simple a process as it sounds. A bit tedious along the side next to the cockpit wall. I might have banged my knuckles a couple of times but it worked. A couple of hours. Sharp chisels.

My drain has a 90 degree L under the cockpit floor with a ball valve and a hose fitting. In the winter I fit a hose to it and run the hose down through my garboard plug in case I get water under my cover. We collect rain water when cruising. Sink stoppers cover the overboard drains and the hose runs into a container. When not in use the hose comes off and the ball valve is closed. I offset it to make access to the ball valve optimal.

My cockpit floor is not cored so I did not have to deal with sealing one. That would add a step if you have a cored floor.

It is a handy addition and I am glad to have it.

Good luck

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Last edited by downeast450; 04-16-2013 at 06:47 PM.
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  #22  
Old 04-17-2013
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Re: Tips for cutting hole for flush mount through-hull

I had to replace my cockpit drains earlier this year as one tailpipe busted off the original one. It appeared to be the plastic sink drain style and it was really thin and brittle. This could have been catastrophic. While we were concentrating on our race, unknown to us below the deck was the fact that the sea water coming over the rail was not only draining into the bilge, but on a port tack sea water was coming up the open through-hull since the hose had fallen into the bilge below the water line level. We were taking on water in two directions.

Something heavier duty is really called for. I wanted to put in the new Forespar Marleron flush mount, but couldn't find a tool to make the bevel. I had a race the next weekend and needed to get it fixed so I just settled for the marleron mushroom style. The problem with these as a drain is not so much a bit of standing water around the lip, as it will eventually dry... it's the dirt it leaves behind. Everything used to wash down the drain, now it all collects around it. So I don't recommend the high rimmed mushroom style. I was just pinched for time. But I do like the marleron fittings, they're beefy and likely to outlast the boat.

My drains are in the aft cockpit corners. There's no clearance to get a hacksaw at an angle. I really need to find a large tapered bit. It needs a 53 degree taper. Let me know if anyone know where to get one.
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  #23  
Old 04-17-2013
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Re: Tips for cutting hole for flush mount through-hull

Steve,

How about cutting off a piece of a large wooden fid and applying some adhesive backed abrasive to it? A centered bolt could be chucked into a hand drill and you could use it as a tapered grinder.

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  #24  
Old 04-17-2013
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Re: Tips for cutting hole for flush mount through-hull

It's not a big deal and very easy to do with a dremel. I used a sanding drum head.

Just drop in the hole, trace around the outside and cut to that new line as smoothly as you can. You just test fit until it looks acceptable and use 3M 4200 or something equivalent when you install. It is best to have someone help you so that the fitting doesn't turn as you screw on the nut beow deck.

You'll find that it does not need to be perfect as long as it is uniform. Even if the angle is slightly off, the contact and the sealer will keep it from leaking. I did this same thing to replace and enlarge my cockpit drains recently.

Murph

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  #25  
Old 04-19-2013
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Re: Tips for cutting hole for flush mount through-hull

I just did side-deck drains. There had been no such on my boat, and a bit of an engineering flub caused the boat to always hold water on the side decks, that would then get full of atmospheric crud, evaporate, and leave guck on the side decks. Hated it.

I bought 2 flush drains with 2-1/2 inch tops and 3/4 inch outlets. You'd obviously want bigger for cockpits. Though I was pretty sure there was adequate deck thickness in the installation spot, I first epoxied a 3/8" fibreglass backing plate underneath each future hole to ensure adequate strength and thickness. Luckily my side decks are not cored. If yours are, this whole narrative might be moot.

I took a 2-1/2" hole saw, and cut into the deck a little at a time, removing the material with a sharp chisel. This left me with a lot of glass fibres in my sleeves that drove me crazy for a couple of days. When I found I had had adequate depth, I switched to a 1" hole saw, using the same pilot hole to guide the cut. So I ended up with a squared, stepped hole. I masked the top of the drains and around the holes, gooped up the hole and the drains with a thick bead of 4000 (will not yellow) and dropped them in. I didn't even do up the backing nuts, just left them flat. They are now in there like concrete. I did up the backing nuts just for good measure, but I don't think they will ever come into play.

You see, I did not worry about a bevel, and I thought it would be beyond my ability and/or tools to cut one anyhow. The amount of gap in the bevel that is filled by the 4000 is relatively small, and there is a lot of surface area in there for the adhesive to do its job. The drains fit the 2-1/2' hole perfectly, there is less than a playing card gap filled with 4000 between drain and surrounding deck surface.

So now thinking about it, even if you have a cored deck or cockpit sole, you could cut out a larger hole, glass it in, and use the same method as above.
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Last edited by Ritchard; 04-19-2013 at 12:38 PM.
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  #26  
Old 04-19-2013
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Re: Tips for cutting hole for flush mount through-hull

I'm leaning towards marelon flush mount drains. I think that the area around the drains is solid glass (to be confirmed), which helps. The main thing is figuring out how best to cut the larger hole.

Ritchard, I can understand your point that it would probably work without being beveled. Just not sure how I feel about that. Something to think about.

Thanks!
-J
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  #27  
Old 04-20-2013
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Re: Tips for cutting hole for flush mount through-hull

We have the same challenge coming up when we replace our bronze thru-hulls with flush Marelon. We'll probably just rasp the solid glass to the approximate angle, perfect that using chalk or lipstick on the thruhull to mark high spots, and bed it in place. The seacock seal will do the rest.

For a thick deck, esp. cored, I'd go at it this way: overbore the outer skin, using a hole saw, dremel, or router, to a diameter slightly larger than the thruhull's maximum. Remove any core for a half inch or so around the opening. Wax and possibly PVA the thruhull; best to wrap the threads with tape or plastic. Fill the overbored cavity with MarineTex or thickened epoxy & bed in the waxed fitting, checking for flush & weighting it in place. Best to remove excess & fair the area now. When the epoxy cures, pop out the waxed thruhull & you will have a perfect socket cast into your hull or cockpit sole. De-wax everything & reassemble with sealant, & off ya go.

We may or may not bed our below-waterline fittings this way; since there are only two, we'll likely just rasp & sand a fair taper. Or use a chamfering bit on the router, tho that's a bit wonky on a curved hull.
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Last edited by bobmcgov; 04-20-2013 at 01:24 PM.
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  #28  
Old 04-20-2013
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Re: Tips for cutting hole for flush mount through-hull

Quote:
Originally Posted by bobmcgov View Post

For a thick deck, esp. cored, I'd go at it this way: overbore the outer skin, using a hole saw, dremel, or router, to a diameter slightly larger than the thruhull's maximum. Remove any core for a half inch or so around the opening. Wax and possibly PVA the thruhull; best to wrap the threads with tape or plastic. Fill the overbored cavity with MarineTex or thickened epoxy & bed in the waxed fitting, checking for flush & weighting it in place. Best to remove excess & fair the area now. When the epoxy cures, pop out the waxed thruhull & you will have a perfect socket cast into your hull or cockpit sole. De-wax everything & reassemble with sealant, & off ya go.
That's a really brilliant way to go about it; I wish I had thought of that. However, for my side drains, I think I'm okay, the above is more than is necessary.
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  #29  
Old 04-22-2013
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Re: Tips for cutting hole for flush mount through-hull

Hi all,
Just a quick "this is what happened" follow-up. I didn't end up installing the flush mount drains. I took a look at the existing deck there, and it's only about 1/2" thick. The head of the new drain was about 0.3" thick. So I was going to have to fiberglass more layers to the bottom, or epoxy a heavy backing plate. Not a huge deal, but I want to go sailing!

Anyway, I decided to take another crack at the original drains which have a thin flange and worked OK. Ultimately, I got the things in there, hoses attached, etc.

I'm still not a big fan of the cheap metal used on some of the sink drain hardware, but it lasted for 25 years the first go around.

Thanks for all the advice and tips on the flush mount issue. It's still great knowledge to have for next time.
Cheers,
J
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