The cult of the Proper Flanged Thru-hull

[HopCar]

Bad, too much thread showing. No backing plate. This is weak.
Better, threads have been cut off so only about 1/2” threads exposed.
Best, no threads exposed, flange spreads side loads over large area. Would still function if thru-hull was removed.

[s/v Jedi]

Originally Posted by HopCar

Bad, too much thread showing. No backing plate. This is weak.
Better, threads have been cut off so only about 1/2” threads exposed.
Best, no threads exposed, flange spreads side loads over large area. Would still function if thru-hull was removed.

The failure is right at the nut, not higher up. Of course the higher you attach the rope used in the test, the more moment you get so cutting the fitting down makes it stronger, but iirc the ABYC specifies a distance to be used for the test?

[mvweebles]

Originally Posted by s/v Jedi

The failure is right at the nut, not higher up. Of course the higher you attach the rope used in the test, the more moment you get so cutting the fitting down makes it stronger, but iirc the ABYC specifies a distance to be used for the test?

From memory, ABYC specifies ability to withstand a 500 lb side load for 30-seconds. Chance of a tall mushroom thru-hull enduring this compared to a flanged seacock is simply not a comparison.

[s/v Jedi]

Here is the relevant part from ABYC. So yes, cutting the fitting to size will make passing the test more likely.

[s/v Jedi]

And note that a ball valve with NPT thread may not be mounted onto a thru hull fitting (which is NPS thread).

Similarly, translated to EU hardware, a ball valve with BSPT thread may not be threaded onto a thru hull fitting (which is BSPP thread).

[s/v Jedi]

Here’s some eye opening info from Beneteau, published by Practical Sailor. Earlier in the article they confirm tests for ISO requirements are met in lab tests… but these are just for alloy and manufacturing quality, not for strength of installation in their boats (they sent just the fittings to the lab).

Also, note this comment I attached as well.

[deblen]

Brasses and bronzes – Cox Engineering

[goboatingnow]

Originally Posted by s/v Jedi

Here’s some eye opening info from Beneteau, published by Practical Sailor. Earlier in the article they confirm tests for ISO requirements are met in lab tests… but these are just for alloy and manufacturing quality, not for strength of installation in their boats (they sent just the fittings to the lab).



Also, note this comment I attached as well.

The nonsense never stops , iso has tests for both the fittings and the assembly in the boat. Hence you can’t pass iso just cherry picking tests.

I can say the number of boats having through hulls out At 7 years is minuscule and is more indicative of bonding or impressed current corrosion issues.

[goboatingnow]

Originally Posted by s/v Jedi

And note that a ball valve with NPT thread may not be mounted onto a thru hull fitting (which is NPS thread).

Similarly, translated to EU hardware, a ball valve with BSPT thread may not be threaded onto a thru hull fitting (which is BSPP thread).

This would not be correct. In Europe the mushroom with be typically BSPP and the female ball valve BSPT. You do need at least one taper thread to make a good tight fitting.

[boatpoker]

Originally Posted by goboatingnow

The nonsense never stops , iso has tests for both the fittings and the assembly in the boat. Hence you can’t pass iso just cherry picking tests.

I can say the number of boats having through hulls out At 7 years is minuscule and is more indicative of bonding or impressed current corrosion issues.

An impressed current is something that is purposely applied ...

"An impressed current cathodic protection controls the corrosion of a metal surface by making it the cathode of an electrochemical cell. The method of protection connects the metal to be protected to a more easily corroded "sacrificial metal" to act as the anode."

[goboatingnow]

Originally Posted by boatpoker

An impressed current is something that is purposely applied ...

"An impressed current cathodic protection controls the corrosion of a metal surface by making it the cathode of an electrochemical cell. The method of protection connects the metal to be protected to a more easily corroded "sacrificial metal" to act as the anode."

Impressed current corrosion ( or its reverse , protection ) is any external source of corrosion current accidentally or deliberately applied

In my experience vessels exhibiting serious underwater degradation within 7 years have such issues to deal with.

[boatpoker]

Originally Posted by goboatingnow

Impressed current corrosion ( or its reverse , protection ) is any external source of corrosion current accidentally or deliberately applied

In my experience vessels exhibiting serious underwater degradation within 7 years have such issues to deal with.

No. You are mistaken. Electrical terminology such as electrolysis, impressed current, galvanic current and stray current have very specific definitions that are important to the understanding of these processes.

Many of these terms are loosely thrown around by docktalkers who are not educated in these matters.

[chris95040]

Well *I'm* impressed.

[s/v Jedi]

Originally Posted by goboatingnow

This would not be correct. In Europe the mushroom with be typically BSPP and the female ball valve BSPT. You do need at least one taper thread to make a good tight fitting.

I’ve been telling you it’s wrong to do that all the time. When you put a female tapered thread onto a male straight thread, only one turn of thread, or only part of one turn of thread is sealing. It is not allowed.

When tapered thread meets tapered thread, all the turns of thread engage because the taper angle is the same, and a metal to metal seal is achieved.

The text is clear: threads must match and tapered may not be installed on parallel threads. See attachment for citation.

This is why Groco makes thru-hull fittings with combination thread and why these may not be cut down.

Every proper flanged seacock is therefor straight thread. The sealing of straight to straight thread is done using a thread sealant. Sometimes (not for through-hulls I think) an O-ring is used.

[Wotname]

Originally Posted by s/v Jedi

I’ve been telling you it’s wrong to do that all the time. When you put a female tapered thread onto a male straight thread, only one turn of thread, or only part of one turn of thread is sealing. It is not allowed.

When tapered thread meets tapered thread, all the turns of thread engage because the taper angle is the same, and a metal to metal seal is achieved.

The text is clear: threads must match and tapered may not be installed on parallel threads. See attachment for citation.

This is why Groco makes thru-hull fittings with combination thread and why these may not be cut down.

Every proper flanged seacock is therefor straight thread. The sealing of straight to straight thread is done using a thread sealant. Sometimes (not for through-hulls I think) an O-ring is used.

1. The attachment only references NP threads, it makes no comment about BSP threads.
2. Standard practice for the rest of the world using BSP threads is to mate BSPT with BSPP.

You don't have to like it or agree with but you should recognise it is allowed and it is how it done by zillions of pipe threaded unions.

It works!