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Old 15-06-2012, 10:39   #1
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Seacock and thru-hull Poll

Poll on seacocks and thru-hulls
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Old 15-06-2012, 10:46   #2
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Re: Seacock and thru-hull Poll

yes!!!
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Old 15-06-2012, 10:55   #3
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Re: Seacock and thru-hull Poll

Sorry about that. I'm trying to do a multi part progressive poll and found that the how to information is a little lacking. I couldn't go back so you saw the results. And yes works fine. As I've long said you sometimes can't ask the question until you know the answer.

So my question is "Do you know how to do a multi-part poll or who might?
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Old 15-06-2012, 10:57   #4
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Re: Seacock and thru-hull Poll

I dont. But hopefully you can get it going. I was just being funny.... are you trying to poll what people have, prefer, or type of construction?
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Old 15-06-2012, 12:46   #5
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Re: Seacock and thru-hull Poll

I sort of guessed that. The directions in FAQ seem to be minimal, especially when I look at some of the multiple questionnaires I've seen on the site.


There seem to be some serious disconnects between what boaters say about the importance of thru-hulls and what they do. How many times have your heard cruisers say."I've used brand X for 25 years and never had a problem." When the fact is that from years 6 thru 25 the seacock balls had completely corroded out and their just lucky they didn't have a problem. It's amazing to me how many members have said they use PVC ball valves instead of seacocks and never had a problem.

Or, on one hand the new ABYC H-27 standard for seacocks allows for the use of a simple thru-hull fitting with a ball valve attached. Yet we have members on this site expounding on the need to thru bolt the seacock to the hull and are dead set against the thru-ball valve approach. I could go on.

I digress. I'm semi-retired and thought it would be interesting to figure out what boaters really want from their seacocks regarding safety. And then trying to figure out if they're getting it.

Then present the information and hopefully start a dialogue.

Sense you were so willing to respond to my question, would you be willing to help by responding to some test questions?

Aslo, what kinds of boats have you owned?

Fair winds,

jed Guertin
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Old 15-06-2012, 14:07   #6
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Re: Seacock and thru-hull Poll

Yeah, good post. I think many of today's "standards" are created by seller groups for seller groups , rather looking toward longevity and safety. A simple thru hull, with a nut and a ball valve on top is very cheap to install. The thickness of the bronze from bottom of the thread valley to the inside of the thru hull may be only 1/16"...or less.... and yet that is all that keeps the boat from sinking. Even worse, most thru hulls are cast and then machined so the material may have porosity in it to start with. I'm not sure in today's world, I would necessarily insist on a thru bolted flanged seacock.... but I would certainly want one with a flange and backing block stuck in place with 5200 if not.
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Old 15-06-2012, 15:18   #7
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Re: Seacock and thru-hull Poll

When I gutted and re-built Bluestocking in the '90s, I went back with 5/16" bronze bolts to Groco flanged seacocks, with seperately screwed in flush thru-hulls.
I build belt and braces.
But I really think the bolted flange installations harken back to wood construction, where the drying out swelling, and contracting of the plank and wood block combined thickness may have allowed the "nut on the thru-hull" configuration to slacken off.
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Old 15-06-2012, 17:28   #8
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Re: Seacock and thru-hull Poll

Cheechago and Blue Stocking,

Thanks for the input. And would you be willing to be try answering some of the questions I'd like to present.

I like the Murphy's constant quote. Murphy is always on steroids on a boat.

Here's my Murphy's other constant. On a boat, what ever you're looking for is at the bottom of, or back of, the storage space you're looking in. And the second item you discover you need is at the bottom of the pile you created to get the item you initially wanted.

Fair winds
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Old 15-06-2012, 18:28   #9
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Re: Seacock and thru-hull Poll

Quote:
Originally Posted by Blue Stocking View Post
When I gutted and re-built Bluestocking in the '90s, I went back with 5/16" bronze bolts to Groco flanged seacocks, with seperately screwed in flush thru-hulls.
I build belt and braces.
But I really think the bolted flange installations harken back to wood construction, where the drying out swelling, and contracting of the plank and wood block combined thickness may have allowed the "nut on the thru-hull" configuration to slacken off.
I think you're right to a large extent about the wood boats. even a flanged seacock , unbolted, gives some support when the handle is hard to turn... a ball valve on a exposed threaded pipe is stressing the pipe/thruhull right at the weakest threaded part.... at least that's my logic!
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Old 15-06-2012, 18:35   #10
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Re: Seacock and thru-hull Poll

Spartan
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Old 15-06-2012, 19:31   #11
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Re: Seacock and thru-hull Poll

Not so much a question as to the type of seacock but more an issue of the overall system arrangement.

Any seacock increases your risk of sinking sooner than later and I think is much higher than any other hole in the hull event -collision, prop and rudder shaft, saillog, transducer (Sail drive skirt maybe an exception -but I understand there is dual redundancy?) They are all bad - its a question of degree only.

The more of them obviously the higher the risk. Yes a good quality one will be better ( and I suspect what sort is where the poll interest may lie). However they generally present a single point of failure that more than likely will not just dribble but gush when it fails.

What to do?
1/ Reduce or eliminate. Ideally there should be never more than two, 1 inlet 1 outlet preferably zero. Gang them up to reduce number. Eliminate entirely? Have all outlets at least above waterline.
2/ Address that single point of failure so that it needs more than one thing to fail in succession. Add a Valve on top of another "independent" valve. Add Mechanical protection. Run via a seachest. A seachest could even facilitate servicing/replacing valves in water.
3/Preferably have inlet with a siphon arrangement and vent valve so that if seacock doesnt close properly then it should protect the down stream plumbing, at least when unattended.
4/ Use an external siphon inlet pipe -Ok maybe over the top for most.
5/If one must have them then I believe plastic is probably best. However good mechanical (and fire) protection is essential together with a redundant dual hull fastening arrangement. A bung or even better a 'pillow' that can securely placed over the entire cock if leaking should be readily available. A small cofferdam could be installed to make this more robust.
6/ also important is convenient access to allow inspection and maintenance

What have I done?
Paranoid as I am....
Log paddlewheel -gone
transducer -gone
cockpit drains -both gone
icebox drain - well gone
sink inlet outlet - both gone
head inlet outlet -both gone
engine inlet gone
Added cockpit drains above water outlet at stern (yes with cocks) plus ganged tee off for sink (pump out) and bilge pumps. I understand bilge pump should not connect to cockpit drain but it is valved off so could be independent leaving one remaining open cockpit drain. The loo - now a bucket later composting.
Inlet for engine and sink is a pipe over the stern integrated with the self steer blade. Siphon is vented when unattended. Sink pump and detachable hand pump provides for recharging the siphon so that the engine impellor doesn't work against a head on startup.

Got a couple of new bronze apollo 1-1/"2 + 1" ball valves going cheap if anyone wants -Aust.
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Old 15-06-2012, 19:37   #12
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Re: Seacock and thru-hull Poll

Looking forward. Good idea.

b.
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Old 15-06-2012, 20:46   #13
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Re: Seacock and thru-hull Poll

"Even worse, most thru hulls are cast and then machined so the material may have porosity in it to start with."
Absolutely right Cheechako. I know of at least one thru-hull fitting that broke for that exact reason. The boat was in danger of sinking because instead of using a real seacock, the guy had put a ball valve on a thru-hull. Another problem is that the threads on thru-hulls do not match threads on ball valves. Thru-hulls have straight threads and ball valves have tapered threads. You can't get enough thread engagement to ensure a good mechanical joint. It's weak. If you want to use a ball valve, buy a Groco Flanged Adapter. It solves both problems. Groco Flanged Adapter IBVF
I once shared a cab with a guy who worked for the ABYC. I kind of jumped on him about allowing thru-hull / ball valve combos. He said that the boat builders wanted it.
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Old 15-06-2012, 21:37   #14
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Re: Seacock and thru-hull Poll

HopCAr,

You started by talking about your concern about the strength of a thru-hull fitting being cast and than machined and the weakness caused by the machining. Not only is the threaded portion the thinnest section of the system, and therefore the most vunerable on that criteria alone, but as you say, you've also introduced a machined groove, making it even more susceptible to fracturing there.

I know that a thru-hull fitting is NPT threaded and a ball valve is NPS, not a healthy combination. But then again we've seen and heard of cruisers, on this website, stating that they use PVC and Nylon ball valves on their boats.

You suggest that the Groco flanged adapter is a good alternative to a real seacock. Doesn't the Groco set up have the same weakness at the threads. The ASTM NPT thread standard is approximately 5 turns, leaving about 3 or 4 threads vulnerable. Effectively no different that a Groco modified threaded thru-hull. Actually, the NPT thread is a deeper cut than the NPS.

Additionally, I saw a demonstration of a bronze thru-hull/ball valve assembly ( a Groco combination threaded thru-hull fitting I believe) and winch set up trying to replicate the ABYC H-27 500lb hanging weight test. I thought if the unit broke it would be at the base. It snapped right off at the top where the thru-hull and ball valve joined. At that first exposed thread.

While it may have a base and in some ways simplify life, in my opinion it doesn't really address the problem you very correctly present.

In fact, the only thing that fits your criteria is a full blown top quality seacock, whether it be a tapered cone or ball type seacock.

Is that a fair statement? If not could you explain why it isn't.
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Old 15-06-2012, 22:26   #15
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Re: Seacock and thru-hull Poll

Jedg, The Groco Flanged adapter eliminates the miss match between the NPT and NPS threads that you get with Ball Valve / Thru-Hull systems. Don't forget that you still have a NPT to NPT joint on a ball type seacock where the hose adapter screws in. Of course if the NPT to NPT joint breaks on a seacock, at least the break is on the right side of the valve. I feel comfortable with it because I've never seen a NPT to NPT joint break. If you're more comfortable using real seacocks, by all means do so. It might even be a little less expensive than buying the flanged adapter and a quality ball valve. The advantage of being able to change the valve is pretty small considering that a quality ball valve seacock should last a very long time. My boat was built in 1988 and I still have the original Apollo Conbraco seacocks and they still work. I had a couple of hoses off last week and they worked fine.
I probably will get booed for this but I really like Groco's chinese seacocks. There a couple of nice features. You can move the handle stops so that the handle can swing either way which makes some installations easier and they have a 3/8" square hole in the handle which allows you to use a 3/8" socket wrench to get more leverage on the handle for those times you have let it go unmoved a little too long. I have met Don Gross, president of Groco. He is an engineer by training. I'm sure he won't let the chinese slip in any more sub par material.
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