The cult of the Proper Flanged Thru-hull

[s/v Jedi]

Originally Posted by Wotname

Here are two, Google will help you find countless others.
https://redfluid.es/en/differences-b...t-npt-threads/

https://en.wikipedia.org/wiki/British_Standard_Pipe

Does ABYC cite BSP or only NPT?

I only claim what I put in my post, nothing more and nothing less. The first link will give you variations of joints using BSP.

Both of your citations -clearly- state that a BSPP thru hull fitting may only screw into a BSPP valve. The only combination of tapered with straight is when the tapered part is the male/external thread and the straight is the female/internal thread.

This clearly demonstrates that the EU production yachts have a ticking time bomb for every thru-hull fitting installed.

Also, ISO seacock citation still missing.

[Dockhead]

Originally Posted by s/v Jedi

Both of your citations -clearly- state that a BSPP thru hull fitting may only screw into a BSPP valve. The only combination of tapered with straight is when the tapered part is the male/external thread and the straight is the female/internal thread.

This clearly demonstrates that the EU production yachts have a ticking time bomb for every thru-hull fitting installed.

Also, ISO seacock citation still missing.

Sorry, Nick, you are again jumping to wrong conclusions.

U.S. mushroom fittings are straight -- NPS.

But BSP mushroom fittings are taper -- BSPT. The ball valves are straight -- BSPP.

So BSP flangeless underwater fittings are compatible. Do you think all these boats would be certified if they were "ticking time bombs"? Swan and Halberg Rassey have been selling "ticking time bombs" for half a century?

Come on.

[goboatingnow]

Originally Posted by s/v Jedi

Both of your citations -clearly- state that a BSPP thru hull fitting may only screw into a BSPP valve. The only combination of tapered with straight is when the tapered part is the male/external thread and the straight is the female/internal thread.

This clearly demonstrates that the EU production yachts have a ticking time bomb for every thru-hull fitting installed.

Also, ISO seacock citation still missing.

Bspt and bspp are regularly connected and provide good thread dealing , widely used on copper compression fittings

It should be remembered that “ BSP “ is s deprecated term widely replaced by ISO “ G”

All G fittings are parallel threads

[s/v Jedi]

Originally Posted by goboatingnow

Bspt and bspp are regularly connected and provide good thread dealing , widely used on copper compression fittings

It should be remembered that “ BSP “ is s deprecated term widely replaced by ISO “ G”

All G fittings are parallel threads

Only when the tapered part is the external thread or male thread and the parallel part is the internal or female thread, not the other way around.

[OneBoatman]

An Answer to MicHughV's post
First I will say your boat probably was built with some of the best seacocks ever made. Bronze, rebuildable, wih an adjustable tapered seat. I believe it is tragic that they pitted and were damaged beyond salvage by galvanic corrosion. The cause I say is the very fact that they were bonded to the boats grounding plate. This is I believe is a big mistake. The bronze plate is a ground, and not meant for galvanic protection nor can anyone confidently assure you with certainty that it will behave preferentially anodic to protect your "thru hulls" from corroding prematurely. In fact, it is most likely to do exactly the opposite which is what happened. Had they been left on their own, each to act independently, they would in all likelihood still be fine. After all, expecting bronze to protect other nearby bronze in an electrolyte, (seawater) is not logical. I would look to see and probably find that your engine ground may also have been connected electrically to that plate. Use a meter to check for continuity between the grounding plate and drive shaft. Again if my suspicion is true, I would disconnect it from this as it is an "improper bonding approach" because you are without reason inviting the seacock materials to interact galvanicly with the shaft metal, propellor and zincs which should be left independent. Also, once your zincs are tired or if they fall off, and left connected to that plate, now you definitely the stainless steel or Monel of shaft tied in which are both cathodic to bronze and a bad recipe for trouble. So says the old sailor.

[s/v Jedi]

Originally Posted by Dockhead

Sorry, Nick, you are again jumping to wrong conclusions.

U.S. mushroom fittings are straight -- NPS.

But BSP mushroom fittings are taper -- BSPT. The ball valves are straight -- BSPP.

So BSP flangeless underwater fittings are compatible. Do you think all these boats would be certified if they were "ticking time bombs"? Swan and Halberg Rassey have been selling "ticking time bombs" for half a century?

Come on.

Really? So explain how you cut the fitting to size so that the valve is within 1/2” to the nut of the fitting? You can not cut down a tapered fitting.

Also, explain how you can screw the nut that secures the fitting down to the hull when the fitting is tapered? This is BS.

The US fittings have combination thread, so tapered at the end and parallel further down.

[s/v Jedi]

I checked a detail picture of one and there is no taper. The nut can screw down all the way to the outside flange of the fitting. This is BSPP.

So can any Euro brass BSP fitting fan accurately explain how this really works or is it all just a blurp of whatever comes to mind?

[s/v Jedi]

I am not done with this yet. Attached some images from Truedesign. The first one that is lacking from so many others: proof that they conform to ISO (note that the 1/2” fittings do not meet ISO)

The second, proof that their fittings are BSPP thread, not BSPT as claimed here. Furthermore, a clear indication that a valve with tapered thread is NOT to be used and that a BSPP to BSPP must be done, using a thread sealant to prevent leaks.

Still never seen proof from production boats conforming to ABYC or ISO standards. I still believe that they claim conformity when using a fitting and valve that meets specs, while installation does not meet requirements.

[Bowdrie]

Most of the seacocks on my boat are the Wilcox-Crittenden "Sea-Valves", and are of the tapered cone, flanged, (like a Spartan,) the 2 that are not Wilcox-Crittenden are Groco.
The female threads that accept the thru hull are NPT.
The male threads on top are NPTS, this allows the use of the "swivel nut" tailpiece that used, (originally,) a leather washer, (or now,) a rubber flat washer or a big O-ring.
The NPTS on top can also accept an NPT female fitting.
The thru hulls are of 3 brands, Wilcox-Crittenden/Groco/Perko.
All have NPTS threads and will only screw into the seacocks a certain amount before they meet the resistance of the female NPT threads.
This requires calculation of hull and backing plate thickness, and thread depth into the seacock.
Then the thru hulls are cut to proper length for installation.
I've done it myself probably some 250>300 times or so.
This is the way I've seen it on multiple hundreds of boats, some dating to the 1930s, and in production boats up into the '80s before the almost universal switch to ball valves.
Europe? they have always walked to the beat of a different drummer.
I don't care what they do, and as Rhett Butlers line in "Gone with the Wind"; "Frankly my dear, I don't give a damn".

[HopCar]

Bowdrie, none of the seacocks you mentioned came with tapered female threads. Why would they? They were all designed to be used with straight thread thru-hulls.

[Bowdrie]

Originally Posted by HopCar

Bowdrie, none of the seacocks you mentioned came with tapered female threads. Why would they? They were all designed to be used with straight thread thru-hulls.

Might the threads get shallower as they near the end of the bore?
With just hand tightening they always seemed to meet resistance before the bottom end of the bore.
Never having actually measured for internal taper, I guess over the years I just assumed they were NPT.
See, even an old fart can learn something,

[s/v Jedi]

Originally Posted by Bowdrie

Might the threads get shallower as they near the end of the bore?
With just hand tightening they always seemed to meet resistance before the bottom end of the bore.
Never having actually measured for internal taper, I guess over the years I just assumed they were NPT.
See, even an old fart can learn something,

You may have BSPP thread on the seacock? This gives the same feeling of resistance for 3/4” size.

I believe that all flanged valves, nuts etc. are always straight or parallel thread, because if not then the flange may not make it down to the hull before the thread stops further tightening.

New Groco fittings have a combination thread. Tapered at the end and straight all the way down. But that should go all the way into a straight female thread.

From these discussions it is clear that there is way too much confusion. So much so, that we don’t even know for sure what is straight threads and what is tapered. This is bad, we should know exactly how this works because the seacocks are primary systems; they can potentially sink the boat.

For US it is clear: parallel thread both sides for flanged adapters/valves and a male NPT into a female NPT for a valve straight onto a fitting (because the fitting has a combination thread… can not be cut down to size in that case). For EU boats, with flanged adapters and valves it is BSPP into BSPP, much like the US does, but they claim to cut the skin fittings down to size which means they have parallel thread which they then put a nut on to fasten it to the hull (still okay) but then continue to put a valve with a female tapered BSPT thread on, which is not allowed for ISO compliance, so that’s what we have it seems…

[HopCar]

Originally Posted by Bowdrie

Might the threads get shallower as they near the end of the bore?
With just hand tightening they always seemed to meet resistance before the bottom end of the bore.
Never having actually measured for internal taper, I guess over the years I just assumed they were NPT.
See, even an old fart can learn something,

It would make sense that the last thread or two might be shallower. I guess it would depend on how the threads were cut.

[MicHughV]

An Answer to MicHughV's post
First I will say your boat probably was built with some of the best seacocks ever made. Bronze, rebuildable, wih an adjustable tapered seat. I believe it is tragic that they pitted and were damaged beyond salvage by galvanic corrosion. The cause I say is the very fact that they were bonded to the boats grounding plate. This is I believe is a big mistake. The bronze plate is a ground, and not meant for galvanic protection nor can anyone confidently assure you with certainty that it will behave preferentially anodic to protect your "thru hulls" from corroding prematurely. In fact, it is most likely to do exactly the opposite which is what happened. Had they been left on their own, each to act independently, they would in all likelihood still be fine. After all, expecting bronze to protect other nearby bronze in an electrolyte, (seawater) is not logical. I would look to see and probably find that your engine ground may also have been connected electrically to that plate. Use a meter to check for continuity between the grounding plate and drive shaft. Again if my suspicion is true, I would disconnect it from this as it is an "improper bonding approach" because you are without reason inviting the seacock materials to interact galvanicly with the shaft metal, propellor and zincs which should be left independent. Also, once your zincs are tired or if they fall off, and left connected to that plate, now you definitely the stainless steel or Monel of shaft tied in which are both cathodic to bronze and a bad recipe for trouble. So says the old sailor.

Thanks for that post. I don't have that boat anymore. It was a C&C Landfall 42. The only zinc on the boat was on the prop shaft, but yes, even the engine was bonded to the dynaplates. The prop zinc was replaced from time to time, when I had a diver go down to clean the hull, but it was often missing, so what you say makes sense.

[boatpoker]

Originally Posted by MicHughV

An Answer to MicHughV's post
First I will say your boat probably was built with some of the best seacocks ever made. Bronze, rebuildable, wih an adjustable tapered seat. I believe it is tragic that they pitted and were damaged beyond salvage by galvanic corrosion. The cause I say is the very fact that they were bonded to the boats grounding plate. This is I believe is a big mistake. The bronze plate is a ground, and not meant for galvanic protection nor can anyone confidently assure you with certainty that it will behave preferentially anodic to protect your "thru hulls" from corroding prematurely. In fact, it is most likely to do exactly the opposite which is what happened. Had they been left on their own, each to act independently, they would in all likelihood still be fine. After all, expecting bronze to protect other nearby bronze in an electrolyte, (seawater) is not logical. I would look to see and probably find that your engine ground may also have been connected electrically to that plate. Use a meter to check for continuity between the grounding plate and drive shaft. Again if my suspicion is true, I would disconnect it from this as it is an "improper bonding approach" because you are without reason inviting the seacock materials to interact galvanicly with the shaft metal, propellor and zincs which should be left independent. Also, once your zincs are tired or if they fall off, and left connected to that plate, now you definitely the stainless steel or Monel of shaft tied in which are both cathodic to bronze and a bad recipe for trouble. So says the old sailor.

Thanks for that post. I don't have that boat anymore. It was a C&C Landfall 42. The only zinc on the boat was on the prop shaft, but yes, even the engine was bonded to the dynaplates. The prop zinc was replaced from time to time, when I had a diver go down to clean the hull, but it was often missing, so what you say makes sense.

Neither the Landfall nor any other Canadian built C&C were bonded at the factory. None left the factory with Dynaplates. Who knows who played with the electrical system over the years or the quality/rationality of the work that was done.