Seacock warning, probably most relevant to Australians

[s/v Jedi]

Originally Posted by Dockhead

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?

You’re now stuck in repeating something that is wrong. Everyone who handled these knows that and I guess you will need to have one in your own hands before you believe it because regardless of how many tell you (I included reasons you ignore), you don’t accept/believe it. They are rather cheap, easy to get first hand experience and know for sure

Meanwhile, when designed so that a person can never step onto it, I agree that such strength isn’t required. What stays are other faults, like a diesel motor coming off it’s mounts hanging by the water hose. All those need to have secondary safety mounting to deal with that as well (I have that anyway).

[Wotname]

Originally Posted by s/v Jedi

You’re now stuck in repeating something that is wrong. Everyone who handled these knows that and I guess you will need to have one in your own hands before you believe it because regardless of how many tell you (I included reasons you ignore), you don’t accept/believe it. They are rather cheap, easy to get first hand experience and know for sure

Meanwhile, when designed so that a person can never step onto it, I agree that such strength isn’t required. What stays are other faults, like a diesel motor coming off it’s mounts hanging by the water hose. All those need to have secondary safety mounting to deal with that as well (I have that anyway).

Dockhead has raised an interesting question and one I share.

I don't see him repeating some wrong fact. What he is doing is repeating a question, one which no one has answered; namely 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.

To simply say Everyone who handled these knows that and I guess you will need to have one in your own hands before you believe it is not an answer or at the best, it's a ludicrous answer. How does holding it give you any real indication of it's strength in comparison to the mushroom type skin fitting.

Certainly if one had a noticeably larger wall thickness, you reasonably estimate the thicker one is stronger but to date, no-one has made a positive statement about the wall thickness. From afar, the images suggest there is no substantial difference in wall thickness.

If it is stronger, surely there must be some straightforward engineering proof to substantiate the claim apart from everyones knows it.

[Dockhead]

Originally Posted by s/v Jedi

You’re now stuck in repeating something that is wrong. Everyone who handled these knows that and I guess you will need to have one in your own hands before you believe it because regardless of how many tell you (I included reasons you ignore), you don’t accept/believe it. They are rather cheap, easy to get first hand experience and know for sure

Meanwhile, when designed so that a person can never step onto it, I agree that such strength isn’t required. What stays are other faults, like a diesel motor coming off it’s mounts hanging by the water hose. All those need to have secondary safety mounting to deal with that as well (I have that anyway).

I am open minded about this, but the reasons you gave only spoke to the strength of the attachment to the hull, NOT the weak spot.


The whole construction will only be as strong as the weakest part -- basic engineering axiom, no? If the threaded neck is the same on both constructions then the strength will be the same. No one has offered even a theory why that wouldn't be the case. Maybe if the inside diameter of the threaded neck is less, so there is more material, but it doesn't look like that from photographs.


I don't believe "holding in your hand" is relevant -- you feel the strong hull connection of the flanged adapter and are subjectively impressed. The skin fitting seems light in comparison. But the skin fitting is embedded in a few inches of GRP and will be hella strong. And in any case, neither of these parts is the place where it will break, so it's not even relevant. Where is MaineSail? He could solve this in 5 minutes on his bench.





I certainly agree that stronger is better for something life and death critical like underwater fittings, and I don't actually like having 17 holes in the bottom of my boat. But I don't think the sea cock design is going to make a critical difference. Next boat will be metal and with a sea chest, and maybe will be done like the Sundeers with all the holes outside of the passenger volume. Now THAT is good design -- far better than any better or worse sea cock.

[s/v Jedi]

What you are saying is that the threaded neck is the same. What those who actually handled these are saying is that the threaded neck is very different; much, much stronger.

Unless you have first hand experience you will have to trust those who have, you can’t just say they are wrong and you are right because it is the same. That would not work for me

[Dockhead]

Originally Posted by s/v Jedi

What you are saying is that the threaded neck is the same. What those who actually handled these are saying is that the threaded neck is very different; much, much stronger.

Unless you have first hand experience you will have to trust those who have, you can’t just say they are wrong and you are right because it is the same. That would not work for me

If the threaded neck is different -- then what you say makes sense. However it doesn't look like that in the photos, and practically couldn't be different unless it had a smaller inner diameter, so color me skeptical.

[skipmac]

Originally Posted by s/v Jedi

Get the Groco flanged adapters, put a Groco valve on top. Can be ordered from Defender and shipped worldwide.

As my original WC tapered cone seacocks fail I've been replacing them with the Grocos. Good stuff.

If you really want to spend some money buy Spartan bronze tapered cone seacocks.

[s/v Jedi]

Originally Posted by Dockhead

If the threaded neck is different -- then what you say makes sense. However it doesn't look like that in the photos, and practically couldn't be different unless it had a smaller inner diameter, so color me skeptical.

Okay now we established that, let me show you the evidence the wall thickness of the threaded neck of the flanged adapter is double that of the skin fitting. This means it is 4 times as strong.
Rod Collins has measured and documented this. You can read all about it here but for the impatient, it is in the last paragraph
https://marinehowto.com/seacock-thru-hull-primer/

[s/v Jedi]

.........

.......... crickets chirping..........

[NevilleCat]

Back to the original post... The bronze ball valves at Whitworths in Melbourne have green handles and appear to have a brass shaft, s/s nut and handle. Don't know what the ball is... either chromed something I think, or doubtfully stainless in nylon/teflon insert. What could be going wrong to cause it to come apart I wonder?

[Don C L]

Here is a shot of the raw water intake valve from my friend's boat with an MD7A. We cursed that poor little engine, certain that the overheating was due to black ooze or some chunk of crud that had clogged all its pores, or so we thought. We pulled the engine out and rebuilt it. Then came the haul out and my friend decided to replace the valves because it was STILL overheating. In the photo you can see the valve handle is in the open position but a look inside shows it was far from open. And the handle FELT like it was opening and closing the valve. Sorry I don't know the brand.
Well, I am sure we did no harm rebuilding the whole engine anyway. Sure runs great now!
In the mean time the bronze seacocks in my nearly 60 year old boat still seem to be fine.

[leftbrainstuff]

There is so much junk sold and fitted to boats it's a wonder more don't sink. There is also widespread ignorance of metal composition, corrosion and reliance on marketing bs.

I have a masters in engineering materials, am a qualified airframe welder, have a mechanical engineering degree and two other trades. There are plenty of no name valves that I have trouble identifying their composition. Many can never be trusted.

For fittings below the waterline if it's not actual bronze, flanged and installed on a G10 or solid fibreglass base then it must be considered suspect.

I've only ever fitted Groco flanged valves on a properly bedded G10 base. This approach lets me sleep at night.

While synthetic valves tend to overcome the corrosion issue they suffer from stiction. The weaker designs can still fail catastrophically. Ergo back to actual bronze.

The sealing ball can also degrade due to scoring so no name bronze valves are to be avoided. The good ones are hard faced and sit in teflon seats.

[Wotname]

Originally Posted by leftbrainstuff

...........

The sealing ball can also degrade due to scoring so no name bronze valves are to be avoided. The good ones are hard faced and sit in teflon seats.

Is this hard facing chrome or something else?
If chrome, would that be chromed brass or (presumably better) chromed bronze or chromed something else?

[Dockhead]

Originally Posted by s/v Jedi

Okay now we established that, let me show you the evidence the wall thickness of the threaded neck of the flanged adapter is double that of the skin fitting. This means it is 4 times as strong.
Rod Collins has measured and documented this. You can read all about it here but for the impatient, it is in the last paragraph
https://marinehowto.com/seacock-thru-hull-primer/

At last an actual explanation with actual facts.



OK, now that makes perfect sense. Thanks.

[Dockhead]

Originally Posted by Wotname

Is this hard facing chrome or something else?
If chrome, would that be chromed brass or (presumably better) chromed bronze or chromed something else?

Typically chrome plated brass. The good ones have stainless steel shafts and handles.


That sounds galvanically bad, but the unlike metals don't touch. The balls and shafts run in PTFE seals.


If you don't "work" ball valves, marine growth can get jammed up between the seal and the ball, which can then get scored. I have made that mistake with deck drain valves which don't get shut off when I'm off the boat.



If you work them regularly -- and I always shut mine off (other than deck drains) every time I'm off the boat overnight -- they last for a long time.



I spray a bit of grease into mine on every haul-out, but I'm not actually sure whether that does any good or whether it might even do harm. I would be interested in others' views on that.


I think it's worthwhile regularly checking all underwater fittings of whatever design for dezincification.

[Wotname]

Originally Posted by Dockhead

.......
If you don't "work" ball valves, marine growth can get jammed up between the seal and the ball, which can then get scored. I have made that mistake with deck drain valves which don't get shut off when I'm off the boat.
.........

I have made the bold assumption that the fouling can only occur on the outside face of the ball (when the valve is closed) but I guess it is possible for some to occur of the inside face but if so, it must minor as there is no sunlight and minimal raw water of that side - yes????

If such an assumption is correct, then these face and seals should last a lot longer than the outside ones.

Like you, I always had mine closed unless in actual use in the moment. I guess if left open, stuff can grow on the bore of the ball but would that cause sale deterioration?