Seacock warning, probably most relevant to Australians

[Breaking Waves]

This is an area where it is unfortunate the standards are not publically available. We went through quite a process re seacocks when trying to get an aluminum boat to pass RINA (Italian) commercial code. Plastic was not allowed for fire reasons (in the machinery space), and any copper alloy (including bronze) was not allowed for galvanic reasons.

The strength standard was:

"To meet ISO 9093-2 the finished product must meet the following strength test, and still function:
A force of at least 1500 N applied a minimum of 10 cycles from a position 20mm off the end of the fitting. The fitting shall show no leakage to the outside of the assembly when subjected to an internal water pressure of 0.1 MPa (1 Bar) after this strength test - and will perform as intended."

I believe but am not 100% sure that when a bronze thru-hull and inline valve (just screwed on with no flange) are sideloaded it is the thru-hull which (generally) fails, and almost certaintly when the thru hull has had a bit of dezinc action (the inline valve is thicker).

[s/v Jedi]

Originally Posted by Breaking Waves

This is an area where it is unfortunate the standards are not publically available. We went through quite a process re seacocks when trying to get an aluminum boat to pass RINA (Italian) commercial code. Plastic was not allowed for fire reasons (in the machinery space), and any copper alloy (including bronze) was not allowed for galvanic reasons.

The strength standard was:

"To meet ISO 9093-2 the finished product must meet the following strength test, and still function:
A force of at least 1500 N applied a minimum of 10 cycles from a position 20mm off the end of the fitting. The fitting shall show no leakage to the outside of the assembly when subjected to an internal water pressure of 0.1 MPa (1 Bar) after this strength test - and will perform as intended."

I believe but am not 100% sure that when a bronze thru-hull and inline valve (just screwed on with no flange) are sideloaded it is the thru-hull which (generally) fails, and almost certaintly when the thru hull has had a bit of dezinc action (the inline valve is thicker).

You can use stainless steel with mica insulation. The Groco flanged adapters, skin fittings and ball valves are all available in stainless steel.

[s/v Jedi]

Originally Posted by Dockhead

I neither like nor dislike these but this is the universal system in Europe, used by Swan, HR, Contest, Oyster, etc. etc. etc. and it seems to work fine. I don't think I've ever heard of a boat sinking in European waters because a bronze skin fitting failed. Different matter is hoses and hose clamps, and those crappy brass fitting the mass builders were using, but that's a materials and not design issue.

The bronze skin fitting stuck through a few inches of GRP bottom, set in Sikaflex, and snugged down with that nut, is hella strong -- must be 10x or 100x stronger than the threaded neck, which is the obviously weak point. A flange which doesn't do away with the threaded neck couldn't possibly add any strength. Different matter of course would be an actual flanged sea cock where the whole ball valve is flanged -- that would be much stronger. But as I said, I'm not sure why that strength would be particularly needed.

The problem comes when the valve is screwed on top, then a 90 degree hose barb fitting and the hose attached. Stepping on that puts enough force on the skin fitting to leak or break. Mainsail has test videos on his YouTube account.
The list of EU manufacturers are all expensive boats but they care more about the 30 coats of varnish on the table than the seacocks.

[Breaking Waves]

Originally Posted by s/v Jedi

You can use stainless steel with mica insulation. The Groco flanged adapters, skin fittings and ball valves are all available in stainless steel.

yea, we used stainless (duplex actually) with fire-resistant g10 insulator - this project was done in a french yard, so we used euro supplier/brand (rather than Groco).

[s/v Jedi]

Originally Posted by Breaking Waves

yea, we used stainless (duplex actually) with fire-resistant g10 insulator - this project was done in a french yard, so we used euro supplier/brand (rather than Groco).

Great, G10 even better.

[Dockhead]

Originally Posted by s/v Jedi

The problem comes when the valve is screwed on top, then a 90 degree hose barb fitting and the hose attached. Stepping on that puts enough force on the skin fitting to leak or break. Mainsail has test videos on his YouTube account.
The list of EU manufacturers are all expensive boats but they care more about the 30 coats of varnish on the table than the seacocks.

Yes, I agree completely. My only comment is that the flanged adaptor for a ball valve will not increase the strength as the weak point is the same.


I think you may sell the premium Euro boat makers a little short. Many of these boats are well engineered and not just the table varnish. I know Oyster has slipped a few times recently, but the Swans I've been on have very thoughtful sea cock installations.


My Moody does not have any ball valve located where you can step on it, and furthermore has direct and complete access, mostly via dedicated access hatches, to all of them. There are no sea cocks with any long adapters on them which would increase the lever arm beyond the minimum.



I don't think these makers are generally doing this badly, although admittedly there have been some slips.

[s/v Jedi]

Originally Posted by Dockhead

Yes, I agree completely. My only comment is that the flanged adaptor for a ball valve will not increase the strength as the weak point is the same.

Sorry but no it’s not. The flanged adapter is many times as strong as a skin fitting with nut. If you step on the hose which is attached to a flanged seacock or a flanged adapter, then this will not lead to a failure of the skin fitting. If you do the same with a skin fitting / nut combo, then it fails every time. This has been tested many times.

[Dockhead]

Originally Posted by s/v Jedi

Sorry but no it’s not. The flanged adapter is many times as strong as a skin fitting with nut. If you step on the hose which is attached to a flanged seacock or a flanged adapter, then this will not lead to a failure of the skin fitting. If you do the same with a skin fitting / nut combo, then it fails every time. This has been tested many times.

I'm open minded about this but I'm not seeing it.


In MaineSail's testing, the threaded neck breaks off, just as you would expect. The nut stays in place and the skin fitting stays in place.



https://marinehowto.com/seacock-failure-testing/




The flanged adaptor has exactly the same threaded neck. Why would it fail any differently? What difference would it make?

[s/v Jedi]

Originally Posted by Dockhead

I'm open minded about this but I'm not seeing it.


In MaineSail's testing, the threaded neck breaks off, just as you would expect. The nut stays in place and the skin fitting stays in place.


Attachment 207732
https://marinehowto.com/seacock-failure-testing/


The flanged adaptor has exactly the same threaded neck. Why would it fail any differently? What difference would it make?

The test shows the skin fitting breaking. This happens every time, like I wrote. Now you have an open hole to close.

The tapered threaded stud on a flanged adapter is much, much stronger than a skin fitting. I do not believe there is a documented case of it breaking. The wall is thicker and threads engage deeper. This is why it is recommended by anyone who worked with both.
Is a flanged seacock better? Probably. It would suit Swan and Contest to use them. Is it so much better to be that more expensive? I don’t think so, and I don’t think anyone who has all go through their hands would opt for something else than the flanged adapter when it’s their wallet paying the bill

I have a Groco flanged seacock forward, but the flanged adapter everywhere else.

[deblen]

Dockhead I'm sorry-you are wrong about the Groco flanged adapter & Jedi is correct.
Here is a link to Groco with drawings of their flanged adapter.
You will see that the National Pipe Straight skin fitting is thru the hull & threaded up inside the National Pipe Straight Groco IBVF flanged adapter.


The externally threaded portion of the adapter is thicker & stronger than a normal skin fitting in it's externally threaded area.

Hope this explains things. / Len


https://www.groco.net/products/valve...flange-adaptor

[Dockhead]

Originally Posted by deblen

Dockhead I'm sorry-you are wrong about the Groco flanged adapter & Jedi is correct.
Here is a link to Groco with drawings of their flanged adapter.
You will see that the National Pipe Straight skin fitting is thru the hull & threaded up inside the National Pipe Straight Groco IBVF flanged adapter.


The externally threaded portion of the adapter is thicker & stronger than a normal skin fitting in it's externally threaded area.

Hope this explains things. / Len


https://www.groco.net/products/valve...flange-adaptor

So the inside diameter of that flanged adapter is SMALLER than the inside diameter of the skin fitting? That is the only way it could be stronger. It sure doesn't look like that to me. It looks the same. Do you have dimensions?

[s/v Jedi]

Did not find the test on Rod Collins’ YT channel. But the test of a bronze skin fitting + valve failed immediately at 400 pounds while the same setup in Marelon failed at 200 pounds. Both fail ABYC recommendation which is that they must stand 500 pounds for 30 seconds.

This is why this practice is not good enough for US build standards and flanged adapters or flanged seacocks are used

[er9]

Originally Posted by Breaking Waves

This is an area where it is unfortunate the standards are not publically available. We went through quite a process re seacocks when trying to get an aluminum boat to pass RINA (Italian) commercial code. Plastic was not allowed for fire reasons (in the machinery space), and any copper alloy (including bronze) was not allowed for galvanic reasons.

The strength standard was:

"To meet ISO 9093-2 the finished product must meet the following strength test, and still function:
A force of at least 1500 N applied a minimum of 10 cycles from a position 20mm off the end of the fitting. The fitting shall show no leakage to the outside of the assembly when subjected to an internal water pressure of 0.1 MPa (1 Bar) after this strength test - and will perform as intended."

I believe but am not 100% sure that when a bronze thru-hull and inline valve (just screwed on with no flange) are sideloaded it is the thru-hull which (generally) fails, and almost certaintly when the thru hull has had a bit of dezinc action (the inline valve is thicker).

I think your last statement pretty much sums up the need for a flanged adaptor through bolted through the hull, especially on thin skinned hulls. any accidental side load distributes the stress and loads across the wide flanged base which distributes it across a wide section of hull reducing the chance the thruhull will crack or fail, or even worse on a thin skin hull, damage the hull. probably not as much of an issue if your hull is 1" thick but theres no AAA out in the middle of an ocean.

I guess need really depends on use though. if you never plan on going more than a mile or two offshore, flanged seacocks may be a waste of money but personally I wouldn't want to cross an ocean without them.

also if European rules say you must replace thru-hulls every 5 years why would boat builders bother putting in thruhulls and valves that will last 50? it would be a waste of money.

[Dockhead]

Originally Posted by s/v Jedi

Did not find the test on Rod Collins’ YT channel. But the test of a bronze skin fitting + valve failed immediately at 400 pounds while the same setup in Marelon failed at 200 pounds. Both fail ABYC recommendation which is that they must stand 500 pounds for 30 seconds.

This is why this practice is not good enough for US build standards and flanged adapters or flanged seacocks are used

Nothing in this post states any reason why flanged adapters should be stronger, or gives any evidence that they are.



So the question still remains unanswered -- if the two constructions have precisely the same weak point, how can one of them be stronger than the other? The threaded part where the ball valve screws on is apparently the same in both constructions, and this is the place where the construction will break, as seen in Rod's test. The strength of the attachment to the hull is not the weak point, so this part being stronger in one case is not relevant.



Anyone have any test results, or even dimensions? Or is this a mere prejudice, as it increasingly seems to me?

[Dockhead]

Originally Posted by er9

I think your last statement pretty much sums up the need for a flanged adaptor through bolted through the hull, especially on thin skinned hulls. any accidental side load distributes the stress and loads across the wide flanged base which distributes it across a wide section of hull reducing the chance the thruhull will crack or fail, or even worse on a thin skin hull, damage the hull. probably not as much of an issue if your hull is 1" thick but theres no AAA out in the middle of an ocean.

I guess need really depends on use though. if you never plan on going more than a mile or two offshore, flanged seacocks may be a waste of money but personally I wouldn't want to cross an ocean without them.

Flanged sea cocks and flanged adapters are two completely different things.


Flanged sea cock is clearly much stronger than other constructions. Whether this strength is really needed if your through hulls are well located where you can't step on them, I don't know, but they look nice.


Flanged adapters do not appear to be any stronger than ordinary skin fittings. See discussion above. I believe they exist only to solve the NPT/NPF thread problem. They are unknown in Europe.

Originally Posted by er9

also if European rules say you must replace thru-hulls every 5 years why would boat builders bother putting in thruhulls and valves that will last 50? it would be a waste of money.

There is no such rule. The rule is that they must LAST at least 5 years, a different thing. Which led some penny-pinching mass producers (not naming any names, but Groupe B you know who you are) to use crappy brass through hulls and ball valves, which I think is criminal, especially since under some circumstances these won't last even 5 years.


Good bronze skin fittings last almost forever. Most of mine are original and 18 years old, although I have gradually replaced almost all of the ball valves. I inspect them every haul out for dezincification but I've never seen a trace of this. They are unbonded and there is no obvious way for this to happen.



Ball valves won't last 50 years, and it makes no difference whether they are installed in a flanged sea cock or on a skin fitting. If you want the valves to last 50 years, then you need the old fashioned tapered cone ones. I have had these on previous boats and they are pretty to look at but I don't have any particular love for them -- they require maintenance beyond greasing and working like ball valves, which I would be loathe to do unnecessarily on a boat with 17 through hulls like this one.



I prefer good quality bronze ball valves personally -- they have a better action than tapered cone valves, they are leak and dribble free, they are maintenance free other than spraying with grease inside every haul out, and they last 15 years or more. Good ones with stainless steel shafts and handles, with plugs for greasing the shafts, and made of proper 85-5-5-5 bronze. Maestrini in Italy, the OEM supplier to different high end European boat builders, make good ones, and they aren't horrendously expensive; maybe $150-$200 each for say a 1 1/2" BSP one. I don't mind spending that every 15 years or so to avoid the PITA of lapping in tapered cone valves and putting up with the dribbles.