The cult of the Proper Flanged Thru-hull

[fourlyons]

Originally Posted by Cyrus Safdari

The rest of your boat includes a lead keel weighing several tons pulling your boat down glug glug glug
As more water enters the boat, it sinks lower. As it sinks lower, the hole is lower underwater too so the water pressure increases so more water gets in faster even if the hole size remains constant
At no point will a sailboat stop sinking unless it has special foamed or watertight compartments built in of sufficient size to hold afloat a flooded boat which do exist

Take a pail, put a brick in it just heavy enough to keep the pail bottom slightly under water. , and poke hole just below waterline on the side of the pail then try to float it in a pool or bathtub
What happens? Does the water at any time stop flowing in and equalize? Of course not, with a brick in it.. The more water enters, the deeper the pail sinks as it gets even heavier, the faster more water enters, until the pail sinks.

Boats with leaks below the waterline whether from a seacock leak or whatever don't just magically stay afloat unless they have built-in "inherent buoyancy"

No, not actually true. If as Tetepare alluded to, the leaking through hull is in an area, partitioned from the rest of the bilge by a partial bulkhead that is higher than the waterline plus the added weight of that compartment fully flooded. It's done all the time, I did the same in my boat, all of my through hulls could fail completely and not sink the boat.

[Cyrus Safdari]

Originally Posted by fourlyons

, partitioned from the rest of the bilge by a partial bulkhead that is higher than the waterline plus the added weight of that compartment fully flooded. .

Yup, sorry I didnt catch a reference to a bulkhead serving this purpose
Such a partitioned bulkhead would constitute a form of inherent buoyancy. It would have to be very specifically calculated & designed to serve this purpose.

I am no nautical engineer but I imagine for example you'd have to calculate not just the weight & volume & effect on momentum of the boat and build a bulkhead but then figure out how the boat will sit in the wavey water in a storm once a compartment is flooded and whether tbe water inside the partitioned bulkhead could spill past it

In other words NOT something an idiot like me can hope to figure out I'll stick to using a proper flanged seacock

I have yet to meet a Cap't that knows the actual displacement of their vessel with full tanks gear aboard nevermind being able to do all this

[Searles]

No ,to ,go boating now cw603n is not bronze it’s a brass with about 30% zinc ,while the composition may slow the breakdown ,in seawater of different levels of chemical make up ,I would not use or trust it ,bronze is NO zinc will out last most vsls in seawater ,do it once do it wright9

[deblen]

Originally Posted by goboatingnow

CW602N brass from good quality manufacturers is entirely suitable for seawater and will remain suitable for decades . This is behind the DNZ marking ( CR)

There’s no field evidence that flanges are needed

I googled "lifespan of DZR marine fittings" - 5 years
http://www.pcmarinesurveys.com/Paul%...20Seacocks.pdf

[AiniA]

I replaced my through-hulls, and added one, with TruDesign fittings from NZ. Good conceptually and well-made. Also, much cheaper than good bronze ones.
https://www.trudesign.nz/marine

[deblen]

If you read this carefully,the author has studied,tested & described the subject in sufficient detail to convince me of the dangers of poor thru hull/skin fitting/seacock practices.
Note toward the bottom of the article where he clearly explains the weakness of mismatched threads,too long,exposed to physical damage mushroom fittings,rough weather caused damage,thinness of mushroom fitting threaded area,combo tapered/straight threaded mushrooms,etc.
These weaknesses are identical to NPS(N.American) & BSPP(UK) mushrooms.


Confession: I have not replaced all my "bronze mushrooms & bronze marine ball valves" with Groco flanges yet but I'm working on it.
In the meantime,I give each of them a solid whack or two with a hammer each spring & keep tapered wooden plugs handy. / Len


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

[skipgundlach]

Did I somehow find an unobtanium?

Seems to me that all of my valves I've replaced have been marine; NPS on inlet, and NPT on outlet.

Made me nervous, in fact, when attaching to the TH, in that it never tightened, until the very end. Seems it/they should come with lock nuts like stuffing boxes...

So, I used 5200, and ran them all the way down; let them sit a good long while with both ends open before connecting the rest of the stuff, including the NPT nipple...

[jshukis]

Originally Posted by Jammer

...There is a case to be made that this arrangement isn't very strong...

On my Morgan I went through the laborious process of replacing the thru-hulls with Proper Flanged Thru-Hulls...

Was it necessary? I'm not sure.

Full-fledge cult member here! My 2008 Beneteau used the "standard" method for many euro production boats, which is DZR brass hardware, aka "marine brass", straight thread into tapered thread (yuck!), no flange, and no backing plate. In 2013 mine looked absolutely perfect, with no leaks or corrosion, but I decided to replace them all anyway because the Beneteau lawyers would, if yours were to fail, tell you that thru-hulls are a maintenance item with a limited service life.
I am glad that I replaced mine! Step one was to hacksaw through the old threads. This should have been difficult, but the "marine brass" was surprisingly soft, having been slowly de-zincified over time, with no visible change on the outside. And this is on a boat with a full isolation transformer and no history of burning through zincs quickly.

I replaced every thru-hull with a straight-threaded silicon bronze mushroom screwed into a straight-threaded silicon bronze combo flange and ball valve, into which I threaded the proper bronze hose adapter. The Buck Algonquin tri-flange ball valve was a key find - Real Bronze with straight threads on one end for the mushroom and tapered threads on the other for the pipe adapters.
A flanged thru-hull has to screw into something, so I made backing plates out of G10-FR4 and epoxied them to the hull with epoxy mixed with glass fiber.

I attached a photo of a sink drain for reference.

Oh and one more vote for making https://marinehowto.com/seacock-thru-hull-primer/ required reading!

[teneicm]

Mismatched threads and cheap plastic thru hulls are bad, 'proper" flanged thru-hulls are better, Tru-design composite thru-hulls are better still. Composite construction, the load bearing collars eliminate strength/ breakage concerns, no metal parts so no corrosion or need for bonding. Also typically easier to install than the flanged thru hull process.

[Colonel Bob]

Originally Posted by ItDepends

The logic for the flange is to make the entire fitting mechanically strong enough that it will not break off if somebody or something falls against it, or uses it as a step, or puts a 3 foot wrench on a stuck valve handle, or any number of other unforeseeable mechanical stresses are imposed on the fitting.

The standard for good practice also says that all seacocks should be easily accessible.

Most sailboats built in the last 30 years grossly violate the accessibility requirement with many of their seacocks, which--in a perverted way--makes the requirement for physical strength less important.

Does two wrongs make a right?

P.S.: Hopefully you didn't really use "brass" for your seacocks, but are using that as a generic term for any kind of vaguely yellowish metal.

Having just replaced six thru hulls on my Jeanneau 42DS, I say "amen" to the practice of inaccessibility. The crappy Beneteau/Jeanneau metallurgy will break off in your hand without warning. I am a big fan of the TruDesign family of composite valves, thru hulls and tailpieces, from NZ. The design is great. No problem with mismatched threads and if the matching collar for the ball valve is added it fully complies with ABYC for impact and weight bearing.

[teneicm]

Originally Posted by jshukis

I attached a photo of a sink drain for reference.

Holy smokes, you ARE a full-fledged cult member! You went to all that trouble for an above-waterline thru-hull? I mean, it's great, but a lot of work for something not nearly as critical as other thru-hulls.

[bcboomer]

+1 for Trudesign. I replaced the 3 bronze and 1 Marelon thru hulls and valves with Trudesign in 2013. No worries about corrosion or sticking. Do it once and forget about it.

[Jetx]

Our boat had DZR brass thru-hull fittings and ball valves from the factory. I didn’t trust them and decided to replace them wholesale when we bought the boat (15 years old at the time).

TWO of the thru-hulls snapped off completely as I was trying to coax the hose off of the attached barbed fittings. Very scary.

[Bowdrie]

Originally Posted by jshukis

Full-fledge cult member here!

You sir are in a proper frame of mind.

[jshukis]

Originally Posted by teneicm

Holy smokes, you ARE a full-fledged cult member! You went to all that trouble for an above-waterline thru-hull? I mean, it's great, but a lot of work for something not nearly as critical as other thru-hulls.

Oh no. All of the thru-hulls that I reworked are below the waterline, including the one pictured. Might I might be crazy enough to do the same for something above the waterline if given a chance? I plead the 5th.