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Old 14-10-2018, 09:12   #1
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Thru hull counts

We have always entertained ourselves when we are in a boatyard walking around the hauled out boats looking at dumb design "features" on boats. You know the ones, the prop shaft that can not be removed without pulling the engine, the rudder with the gap that was perfectly designed to catch a pot line, etc, etc.

But our favorite is counting underwater thru-hull fittings. Recently we set a new record. It was a new boat, just being commissioned, built by a major manufacturer you have all heard of, about 48 feet long with 28 holes in the hull below the water line, and that was not even counting things like transducers! WTF???? How can a boatbuilder (or boat buyer) think this is even remotely a good idea? Have people no respect for the ocean? Hell, you could own the boat for ten years and still need a map to find them all. What on god's blue ocean do you even DO with that many???

I used to be mystified reading the stories, and there are many of them, about the boats that founder while the crew frantically, and unsuccessfully, search for the source of the incoming water. No impact, so it must be a failed thru-hull or some attached plumbing. I now understand. With 28 thru-hulls there is NO WAY you could find the problem before the boat sank.

We have a large, well appointed boat, with three holes below the water line, and three either just above or right at the water line. That's it. And we have two heads, a full galley, air conditioners, watermaker, clothes washer, genset, and a washdown pump.

I guess it is harder to think about good design than to point and say, "Drill another hole here."
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Old 14-10-2018, 09:46   #2
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Re: Thru hull counts

I hear you Billkny!... but I'm curious about how you've managed to get down to just 3 through hulls below the waterline.

I've been eliminating through hulls below the waterline whenever possible. I'm down to 5: galley sink drain, head sink drain, engine raw water intake and 2 cockpit scupper drains. One of the advantages of installing a composting head was that I could glass over another through hull. On my last haul out I glassed over the old transducer hole. I now rely on 2 fishfinders that shoot through the hull. Simplicity is my mantra
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Old 14-10-2018, 09:49   #3
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Re: Thru hull counts

I've counted over 20. Boggles the mind.
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Old 14-10-2018, 09:56   #4
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Re: Thru hull counts

Wow. And here I thought my 15 (excluding transducers) on a 47'er was bad! Well, it kinda is, isn't it?

Eng, genset, 2 a/c's, refrig, anchor wash, 2 cockpit drains, 2 deck drains, 3 sinks, 2 heads. One of the first things I did after buying the boat was replace & double-up on hose clamps (and use the proper ABA ones), along with a few hoses. All the thru-hulls/seacocks are bronze Spartans and so pretty bulletproof. More maintenance but worth it, imo. And yes, I do have a map posted prominently showing each locale.

Does your boat have standpipes or a box which eliminates thru-hulls? Considering that I've been consistently told by surveyors that the great majority of sinkings occur at the dock, I'm surprised that the industry hasn't moved on to a safer, more manageable system.
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Old 14-10-2018, 09:59   #5
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Re: Thru hull counts

Interesting - could you list the 3 through holes you have and how all the internal equipment must share some of the ports both in and out. When ports are shared they usually need check valves to prevent one device robbing water flow from another. Also you might not want to share your water maker inlet with a head inlet irrespective of check valve efficiency.



On face value if each device has its own supply then through hulls would normally be:


2 inputs for 2 heads

2 exits for 2 heads
1 input for generator
1 input for water maker
1 input for wash down
1 input for engine cooling
1 input for each conditioner
_
9



I guess to get the number down one could install composting or chemical cassette type heads, an air cooled generator, use an outboard, a rainman type water maker with an inlet hose over the side and same for wash down pump - then you would have zero through hulls below the water line.



I agree that 28 seems high for a 48 ft monohull - must have a lot of heads and airconditioners.
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Old 14-10-2018, 10:10   #6
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Re: Thru hull counts

Quote:
Originally Posted by Bean Counter View Post
Interesting - could you list the 3 through holes you have and how all the internal equipment must share some of the ports both in and out. When ports are shared they usually need check valves to prevent one device robbing water flow from another. Also you might not want to share your water maker inlet with a head inlet irrespective of check valve efficiency.



On face value if each device has its own supply then through hulls would normally be:


2 inputs for 2 heads

2 exits for 2 heads
1 input for generator
1 input for water maker
1 input for wash down
1 input for engine cooling
1 input for each conditioner
_
9



I guess to get the number down one could install composting or chemical cassette type heads, an air cooled generator, use an outboard, a rainman type water maker with an inlet hose over the side and same for wash down pump - then you would have zero through hulls below the water line.



I agree that 28 seems high for a 48 ft monohull - must have a lot of heads and airconditioners.
A boat with freshwater heads can eliminate input thru-hulls. Some boats also have either standing pipes (that terminate above the waterline) or a common "box" (can't recall the name for it at the moment) which feed all the r/w to appliances via one common thru-hull.
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Old 14-10-2018, 18:56   #7
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Re: Thru hull counts

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Originally Posted by Copacabana View Post
I hear you Billkny!... but I'm curious about how you've managed to get down to just 3 through hulls below the waterline.
Underwater thruhull #1 is a seachest that supplies raw water to the engine, genset, watermaker, and two AC cooling pumps. All this is contained in the watertight engine room compartment.

Underwater thruhull #2 feeds raw water to the forward head toilet and the anchor/deck wash down pump.

Underwater thruhull #3 feeds raw water to the aft head toilet.

Forward head toilet gravity discharges from the holding tank at water line. As does the aft head toilet.

Head and galley sinks, clothes washer, shower pans, and bilge drain to a sump, where a diaphragm pump disharges overboard to thruhull above the waterline shared with the two AC cooling loop discharges, watermaker reject line, and manual bilge pump.

Engine, and genset exhaust discharge above the water line as well.

I might have missed something, but you get the idea. If NOT putting holes in the bottom of the boat is a priority, it CAN be done.
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Old 14-10-2018, 19:13   #8
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Re: Thru hull counts

We had 18 when I bought this boat (60' Seaton Ketch); even the bilge pumps discharged underwater! Now have ... intake for Aux engine, Genset, House Aft (AC/WM/Galley), House Fwd (alternate head for SW flush, SW washdown); two head discharges, one galley discharge; all the rest into sumps and pumped out above the nominal heeled waterline. Took a while to glass them over but we worry less!
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Old 14-10-2018, 19:34   #9
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Re: Thru hull counts

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Originally Posted by billknny View Post
Underwater thruhull #1 is a seachest that supplies raw water to the engine, genset, watermaker, and two AC cooling pumps. All this is contained in the watertight engine room compartment.

Underwater thruhull #2 feeds raw water to the forward head toilet and the anchor/deck wash down pump.

Underwater thruhull #3 feeds raw water to the aft head toilet.

Forward head toilet gravity discharges from the holding tank at water line. As does the aft head toilet.

Head and galley sinks, clothes washer, shower pans, and bilge drain to a sump, where a diaphragm pump disharges overboard to thruhull above the waterline shared with the two AC cooling loop discharges, watermaker reject line, and manual bilge pump.

Engine, and genset exhaust discharge above the water line as well.

I might have missed something, but you get the idea. If NOT putting holes in the bottom of the boat is a priority, it CAN be done.
I did miss two.. sort of.

The cockpit drains are technically holes in the bottom, but they have no hoses connected, rather they are thick and heavy solid fiberglass tubes 3" diameter (yes, BIG!) glassed in top and bottom that are actually stiffeners for the cockpit structure. Not even equipped with seacocks. You can decide for yourself if they "count" or not.
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Old 14-10-2018, 20:56   #10
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Re: Thru hull counts

I have three as well

Engine intake, galley sink, watermaker input. If you include the cockpit drains that is two more - although they are copper tubes encased in fiberglass
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Old 14-10-2018, 20:56   #11
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Re: Thru hull counts

Quote:
Originally Posted by billknny View Post
Underwater thruhull #1 is a seachest that supplies raw water to the engine, genset, watermaker, and two AC cooling pumps. All this is contained in the watertight engine room compartment.

Underwater thruhull #2 feeds raw water to the forward head toilet and the anchor/deck wash down pump.

Underwater thruhull #3 feeds raw water to the aft head toilet.

Forward head toilet gravity discharges from the holding tank at water line. As does the aft head toilet.

Head and galley sinks, clothes washer, shower pans, and bilge drain to a sump, where a diaphragm pump disharges overboard to thruhull above the waterline shared with the two AC cooling loop discharges, watermaker reject line, and manual bilge pump.

Engine, and genset exhaust discharge above the water line as well.

I might have missed something, but you get the idea. If NOT putting holes in the bottom of the boat is a priority, it CAN be done.
"Seachest" was the term I couldn't remember -- thanks. Seems like a great solution and makes me wonder why more boats don't have them built in. If part of the design process I wouldn't think it would add a lot of mfg. costs but I could be wrong. I would also think it'd be quite difficult to install retroactively, but perhaps not.
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Old 14-10-2018, 23:06   #12
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Re: Thru hull counts

Our boats have at least twenty thruhulls, nerver been a problem. Yes we’ve sprung a leak a few times when a hose clamp let loose, never a problem to locate and repair. Some were eliminated on the 62 by using a manifold,
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Old 16-10-2018, 19:11   #13
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Re: Thru hull counts

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Our boats have at least twenty thruhulls, nerver been a problem. Yes we’ve sprung a leak a few times when a hose clamp let loose, never a problem to locate and repair. Some were eliminated on the 62 by using a manifold,
We obviously have different things we expect from our boats.

If my boat "sprung a leak" EVER, it would ALWAYS be a problem. Springing a leak a "few times?" WTF? Totally NOT acceptable!

My boat's FIRST job and far and away its most important is keeping the ocean on the outside--always. Fortunately for my mental health, it seems to be doing that job a lot better than your boat does.

Maybe you need to inspect and change hose clamps more often and/or use better clamps?
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Old 16-10-2018, 19:15   #14
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Re: Thru hull counts

We have 0 thruhulls on our 38’ catamaran. Also no metal below the waterline.
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Old 16-10-2018, 19:18   #15
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Re: Thru hull counts

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We have 0 thruhulls on our 38’ catamaran. Also no metal below the waterline.
I assume you have no inboard engines then?
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