The cult of the Proper Flanged Thru-hull

[goboatingnow]

Originally Posted by s/v Jedi

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.

Yes that’s the common arrangement

[goboatingnow]

Originally Posted by 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".

I’m sorry it’s you new countries that have lost your way with all this NPT stuff. The new king needs to straighten out a few things it seems

[MicHughV]

Yes, my Landfall 42 had an interesting history. The prior owner was a elderly guy with lots of money, that had no particular interest in sailing what so ever, but enjoyed putzing around with boats. This particular Landfall was hauled out and put into a shed, where it remained for about a year.

The entire interior of the boat was gutted and rebuilt, the hull was spray painted with polyurethane, engine redone, a generator installed, Marine SSB installed, new a/c units, new upholstery, new canvas, etc, the rig came off off course, all rod rigging, hydraulic backstay, all serviced, repaired, etc. The thing was better than new.

I had a friend that worked at this yard and from time to time, when I would visit him, I was allowed on the boat and would climb on this boat to see what was going on. A lot of money was thrown at this boat. A lot.

One day, shortly after the boat had been relaunched, my friend called me and told me the owner thought he was dying and wanted to sell the boat asap. The asking price was way beyond my means, so I declined. About a week went past, and my friend called again, and asked me how much cash I could assemble. I threw an embarrassing pitiful small number at him. A hour later he calls back and tells me...have that money here by noon and the boat is yours. So that is how I became the new owner of this boat.

[Bowdrie]

Originally Posted by goboatingnow

I’m sorry it’s you new countries that have lost your way with all this NPT stuff.

We only lost our way when we depended upon Lucas Electric to light our path.
God save the King, now you just need a Churchill at 10 Downing.

[Dockhead]

Originally Posted by s/v Jedi

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.

You don't cut them -- you order them in the right length to begin with.


I have written, however, to Maestrini to ask them to confirm how they are threaded, and I will post their answer. The Maestrini technical materials state that with some exceptions all of their products have taper external threads and parallel internal threads to make a UNI EN 10226-1 standard joint.

However, I note that Groco BSP fittings are parallel for both through hull fitting (https://www.groco.net/products/fitti...th-series-bspp) and ball valve (https://www.groco.net/products/valve...es-bspp-thread), which is also a compatible combination. Also, they sell "combination thread" ball valves in NPT which is compatible with NPS through hulls.


So, your idea that all these flangeless assemblies have dangerous and incompatible threads is simply wrong, as we've been telling you. One way or another, I guarantee that the Maestrini assemblies used on all high end European boats have compatible threads. I'm still baffled that you could think that the entire European boat industry could be making boats which all fail the very stringent and detailed ISO 9093:2020 standard which is a legal requirement. Just imagine the lawsuits. This is, of course, nonsense.

[goboatingnow]

Originally Posted by Dockhead

You don't cut them -- you order them in the right length to begin with.


I have written, however, to Maestrini to ask them to confirm how they are threaded, and I will post their answer. The Maestrini technical materials state that with some exceptions all of their products have taper external threads and parallel internal threads to make a UNI EN 10226-1 standard joint.

However, I note that Groco BSP fittings are parallel for both through hull fitting (https://www.groco.net/products/fitti...th-series-bspp) and ball valve (https://www.groco.net/products/valve...es-bspp-thread), which is also a compatible combination. Also, they sell "combination thread" ball valves in NPT which is compatible with NPS through hulls.


So, your idea that all these flangeless assemblies have dangerous and incompatible threads is simply wrong, as we've been telling you. One way or another, I guarantee that the Maestrini assemblies used on all high end European boats have compatible threads. I'm still baffled that you could think that the entire European boat industry could be making boats which all fail the very stringent and detailed ISO 9093:2020 standard which is a legal requirement. Just imagine the lawsuits. This is, of course, nonsense.

As usual dockhead you are a paragon of wisdom and common sense.

[s/v Jedi]

Originally Posted by Dockhead

You don't cut them -- you order them in the right length to begin with.


I have written, however, to Maestrini to ask them to confirm how they are threaded, and I will post their answer. The Maestrini technical materials state that with some exceptions all of their products have taper external threads and parallel internal threads to make a UNI EN 10226-1 standard joint.

However, I note that Groco BSP fittings are parallel for both through hull fitting (https://www.groco.net/products/fitti...th-series-bspp) and ball valve (https://www.groco.net/products/valve...es-bspp-thread), which is also a compatible combination. Also, they sell "combination thread" ball valves in NPT which is compatible with NPS through hulls.


So, your idea that all these flangeless assemblies have dangerous and incompatible threads is simply wrong, as we've been telling you. One way or another, I guarantee that the Maestrini assemblies used on all high end European boats have compatible threads. I'm still baffled that you could think that the entire European boat industry could be making boats which all fail the very stringent and detailed ISO 9093:2020 standard which is a legal requirement. Just imagine the lawsuits. This is, of course, nonsense.

Wonderful so before when people wrote that Rod’s videos were wrong because he didn’t cut the skin fitting to size, they were wrong because the fitting can’t be cut to size for EU installations?

Please explain how you screw the nut all the way down to the hull when the skin fitting has tapered thread? This is simply impossible. Even when the nut has parallel thread, the skin fitting’s tapered thread will make a metal to metal seal after which you can thread it on further.

Also pretty sure that flanged valves have parallel thread, even in Europe.

[s/v Jedi]

Originally Posted by goboatingnow

As usual dockhead you are a paragon of wisdom and common sense.

Hahaha

[goboatingnow]

Originally Posted by s/v Jedi

Wonderful so before when people wrote that Rod’s videos were wrong because he didn’t cut the skin fitting to size, they were wrong because the fitting can’t be cut to size for EU installations?



Please explain how you screw the nut all the way down to the hull when the skin fitting has tapered thread? This is simply impossible. Even when the nut has parallel thread, the skin fitting’s tapered thread will make a metal to metal seal after which you can thread it on further.



Also pretty sure that flanged valves have parallel thread, even in Europe.

The ball valve has a parallel thread and the mush room has a tapered. The valve will engage for almost all the available valve thread.

You don’t cut mushrooms you order them in the correct length.

I keep laughing at people questioning European plumbing standards without any obvious understanding of the standards or custom and practice

[deblen]

Thanks to EU posters,I have learned:


Groco sells BSPP (parallel/straight threaded) mushroom thru hulls.
https://www.groco.net/products/fitti...-hull-fittings


Groco sells BSPP inline ball valves to fit the above.
https://www.groco.net/products/valve...es-bspp-thread


Perhaps N.Americans should be using this combo if you are going with the nutted mushroom with inline ball valve route.


Groco also sells a combi thread mushroom that uses NPS(straight thread) on area of stem close to hull and NPT(tapered thread) on the end threads that is a proper match for a NPT inline ball valve.
https://www.groco.net/products/fitti...ings/th-series


Groco recommends using proper flanged,bolted seacocks or flanged, bolted adapter with inline ball valve for strongest installation.
https://www.groco.net/products/valve...flanged-valves


Groco recognizes the proliferation of nutted mushroom head plus ball valve as being acceptable as a seacock by many users. Their comments:
ibv-fbv-tech-blltn.pdf


Finally,I submit Maine Sails pic of a mis-matched taper to straight/parallel thread installation. I leave it to you to decide if this is a strong enough joint for underwater "seacocks",especially if they may be subject to loose equipment/cargo crashing into them.


https://marinehowto.com/seacock-thru-hull-primer/



Cheers/Len

[s/v Jedi]

Originally Posted by goboatingnow

The ball valve has a parallel thread and the mush room has a tapered. The valve will engage for almost all the available valve thread.

You don’t cut mushrooms you order them in the correct length.

I keep laughing at people questioning European plumbing standards without any obvious understanding of the standards or custom and practice

You shouldn’t be laughing at others, it’s a false sense of superiority.

It’s only now that you start to post information that makes sense; I think it is my comments that made you research this and learn, as I do. It has been posted again and again that the valves have tapered thread and the skin fittings have parallel thread. Only after I posted that this is not a safe thread engagement, it got turned around and now we suddenly can not cut skin fittings anymore and need to order the right size. I’m sure there’s not so many sizes available that you can always keep the exposed fitting between nut and valve under 1/2” like previously preached when it was still to be cut down to size. I’m sure you can read back and find that.

You still don’t explain how the nut that comes with the tapered skin fitting can screw down all the way onto the tapered thread. By now, if it’s true that the skin fitting is tapered and the valve is parallel, I’m convinced that the skin fitting is a combination thread just like the Groco fittings (tapered at the end, straight all the way down). It seems it doesn’t matter at all if you use NPS/NPT or BSPP/BSPT : it works exactly the same.

BSPP into BSPP or BSPT into BSPT is far superior to BSPT into BSPP, even though a thread sealant is required. This is why TruDesign, Groco etc. require or prefer these matching thread connections. When you use a BSPT fitting into a BSPP valve, like you praise the EU does, you only get one turn of thread engagement. Not only is this a minimum seal but also the mechanical strength is mediocre. I can believe it can survive the ISO test from a certain diameter up, but not without springing a leak.

I am very curious what info Maestrini returns with. Did you also ask about their testing and results like TruDesign shows?

Edit: it seems that TruDesign with their matching thread and collared valves are the #1 choice now for fittings 3/4” and larger in EU land. Groco can outperform with the same thread compatibility in proper bronze and real flanged valves and adapters.

[Manateeman]

Let’s get back to the basics please. What does a seacock do. It shuts off a hole in the hull. Some members don’t want any holes, some want just one or a standpipe or a seachest. I’ll confine this discussion to seacock valves alone. Not going to get into threads or thruhulls or flanges or lack thereof. Just the valve.
There are millions of valves in use made in different configurations but all ball valves sort of have four common parts. The body, the ball, the stem, the handle.
Some of the bodies come apart in pieces and it will give you a good idea of the construction. These are usually stainless, have easily replaced components, are typically used in industrial settings, can withstand pressure and nasty chemicals.
Expensive and very strong. Easily repaired to like new condition. If you examine enough valves from various manufacturers, you can easily see the more costly valves have substantial stronger stems. It’s simple. The force resisting the turning of the valve ball inside the body and the force on the handle applied to oppose this resistance are connected by the stem. The stem can break where it connects to the ball, or the handle or in the middle. It’s the key part. It fails and you cannot shut out the sea with the valve. (Of course you can plug it but that’s not the subject here)
So why would a stem fail. Something is preventing the ball from moving and a large force like a hammer or cheater bar is being applied. Enough force and something has got to give. If you can’t clear the obstruction you can only hope the force on the handle will not exceed the stem strength and the edge of the ball will cut the obstruction.
It’s just simple. Reinforced plastic stems cannot match the strength of metal in similar size valves.
Flanged Marelon valves cannot be changed out at sea. The Groco Adaptor plate means you change the valve completely or cap it off.
I’m not going to get into the silly thru hull with ball valve on top. The idea that just the few (what...4,5,or 6 max) threads of the nut holding the thru hull to our boat, is all that’s going to keep out the ocean. The nut fails and then what are you going to do. I’ve seen them strip threads and even break from corrosion underneath where it’s difficult to see. What do you do when the thru hullgets loose and turning the nut, doesn’t work. What do you do when the Marelon valve won’t close. In the real world, lots of stuff floats around in the ocean and you need a strong valve and a strong hull attachment to withstand enough force to cut through the obstruction. If it will not close, you need to ram a plug in and hope the thru hull nut doesn’t split and the thru hull pops out to sea.
The Groco Adaptor Plate is one of the best safety inventions in a long, long time.
Happy trails to you.
Mark and the manatee crew.

[OneBoatman]

Strange how the OP replies have drifted to become a discussion of thread types. So since not boaters know about differnt thread types, he goes regarding straight and tapered. In the US these are designated NPS for straight and NPT for Tapered. Tapered theads are designed to "self seal", that is why they have a taper. They rely on having sufficent engagement until there is interference to create a seal. Staight threads are used with either a gasket or an O-ring and are not meant to seal on their own. Without getting into what various manufacturers supply or what you can get away with, it is not a good practice to mix thread types. Fortunatley I can't swear to it but all thru-hull fittings and all seacocks have straight threads. Most but not all valves on the other hand have tapered threads. All through hull fittings have flanges and require a sealant such as a polysulfide, Boat Life, or a product like 3M's 5200. Flanged seacocks can be used alone that is without a separate thru-hull fitting but are more frequently mated to a thru-hull fitting where thread sealant should be used. Straight in straight. If you use ar using a seacock alone you absolutely need a seal between the flange and the hull. If a seacock is not used, thru-hull fittings below the waterline should always be connected to a valve not directly to a hose. Hoses should double clamped to a barb not clamped directly to the stem of through hull male thread. The merrits of using flanged sea cocks are clear in that they allow for a higher strength installation rather than relying solely on the strength of the stem of a thru hull fitting. They not only have a flange to spread out the force transmitted to the surrounding hull they can be securely fastened so as not to rotate. Small bronze sea cocks typically have an integral flange meant to be fastened with three flat head silicon-bronze screws. If you choose not to drill additional holes for the screws you can alternatively bury the screw heads behind a bonded plate from the inside to essentially create studs. This requires prefabricating a backing plate that once made, is bonded directly to the inside of the hull leaving the heads hidden and of course you need to create the larger center hole to allow access to the sea. Because the heads are now "permanently blind" they are apt to rotate so switching to hex heads or silicon bronze machine screws and glassing thenm into a pocket is advisable. The center hole must be large enough for the thru-hull stem to pass through to be connected to the sea cock. Some also make the hole large enough for the thru-hull flange nut such that it is seated on its own against the natural surface of the hull. This make determining the stack height a little easier. For maximum strength the trick is to predetermine the stack height so the thru-hull stem engagement is correct when the flange of the sea cock is flush against the plate and secured. Consider where the handle of the valve for ease of operation as this one of the first steps and bonding of the backing plate is done last.

[s/v Jedi]

Originally Posted by deblen

Perhaps N.Americans should be using this combo if you are going with the nutted mushroom with inline ball valve route.

If one uses bronze instead of plastic, it’s simply a no-brainer to use a Groco skin fitting with Groco flanged adapter. Both sides are NPS or BSPP for a perfect fit. The top of the flanged adapter has either NPT or BSPT thread on which a valve with tapered thread can be mounted for perfect thread engagement, or, when these supposedly exist in the EU, a valve with BSPP thread can be put on because a tapered male thread can go in a straight female thread, at cost of minimum thread engagement.

I still think valves in the EU have a tapered thread but of course a manufacturer can create special valves for these applications. I also still think that the EU skin fittings are parallel/straight thread and not tapered, but we’ll find out I guess.

Finally,I submit Maine Sails pic of a mis-matched taper to straight/parallel thread installation. I leave it to you to decide if this is a strong enough joint for underwater "seacocks",especially if they may be subject to loose equipment/cargo crashing into them.Attachment 264339

https://marinehowto.com/seacock-thru-hull-primer/

Yes, but that thread mismatch on the left side is a male straight thread into a female tapered thread, which is simply not allowed at all. What is claimed by the EU BSP thread fan boys is that their skin fittings are make tapered thread and the valves are female straight thread. How they magically screw the nut of the fitting all the way down to the hull on a tapered thread isn’t explained yet…

[Jammer]

I am surprised by the extent of the discussion and find the replies insightful.