Installing Seacocks - Follow Up Info !!

Ross · Jan 13, 2008

Mainesail The thru-hull that came with Bietzpadlin

mounted flush in a matching molded in place in the hull. All I have from the outside is a small hole. The sink drains that I installed are 1 1/2 inch pvc pipe glassed into the hull and carried up well above the water line and covered with glass cloth and chopped strand and resin with a ball valve on top. Nothing to break or corrode. Built it up as thick as the hull.

Ross · Jan 13, 2008

Mainesail The thru-hull that came with Bietzpadlin

mounted flush in a matching molded in place in the hull. All I have from the outside is a small hole. The sink drains that I installed are 1 1/2 inch pvc pipe glassed into the hull and carried up well above the water line and covered with glass cloth and chopped strand and resin with a ball valve on top. Nothing to break or corrode. Built it up as thick as the hull.

Tom S · Jan 13, 2008

I know Maine Sail is belts, suspenders & more

Any boat he fixed or redid any system on I am sure is done about as good as it gets and anybody would be happy to have a boat he once owned.I totally agree one must have a fully flanged seacock (with NPS threads everywhere

) but I am not totally sold on having to have through bolts all the way through the hull .The Bolts for the flanged seacock are there to prevent the Seacock from spinning off the thru-hull. While there is "some" structural strength from the bolts going all the way through the hull its minimal compared to that actual surface area of the flange sitting on the backing plate.I know Maine Sail conceded that even seacock wood screwed to the backing plate is going to be far stronger than a ball valve screwed directly to a thru-hull. But I disagree that you'd be fully cutting corners using a wood screw into a "Real" Fiberglass Epoxy backing plate. Even Groco and Forespar concede that not having through bolts ALL the way through the hull is not necessary and just secured into a proper backing plate is fine. Even ABYC is good with it. I guess the important thing is a good backing plate (which I totally agree with)http://www.groco.net/SVC-MAN-07/Sec4/BROWSER/tb-1-wv.htmhttp://www.forespar.com/onlineCatalog/2008/Marelon/marelon_flangeMountingSeacocks2008.shtmlI also want to make an observation of another downside of having those bolts ALL the way through the backing plate through the hull (other than 3 more holes in your boat). It will be virtually impossible to replace a bad Seacock without hauling your boat. Even if you tried to "beach" your boat for a few hours I think it would be nearly impossible to get those bolts out and change out the seacock in one tide cycle.I was able to change out a bad Flanged Seacock with the boat in the water by just backing out the wood screws keeping the seacock from spinning around. I would argue those through bolts are really not structual and most of what keeps the structural strength of the seacock is the flanged base of the seacock and the threads on the thru-hull.Just my humble opinion

Tom S · Jan 13, 2008

I know Maine Sail is belts, suspenders & more

Any boat he fixed or redid any system on I am sure is done about as good as it gets and anybody would be happy to have a boat he once owned.I totally agree one must have a fully flanged seacock (with NPS threads everywhere

) but I am not totally sold on having to have through bolts all the way through the hull .The Bolts for the flanged seacock are there to prevent the Seacock from spinning off the thru-hull. While there is "some" structural strength from the bolts going all the way through the hull its minimal compared to that actual surface area of the flange sitting on the backing plate.I know Maine Sail conceded that even seacock wood screwed to the backing plate is going to be far stronger than a ball valve screwed directly to a thru-hull. But I disagree that you'd be fully cutting corners using a wood screw into a "Real" Fiberglass Epoxy backing plate. Even Groco and Forespar concede that not having through bolts ALL the way through the hull is not necessary and just secured into a proper backing plate is fine. Even ABYC is good with it. I guess the important thing is a good backing plate (which I totally agree with)http://www.groco.net/SVC-MAN-07/Sec4/BROWSER/tb-1-wv.htmhttp://www.forespar.com/onlineCatalog/2008/Marelon/marelon_flangeMountingSeacocks2008.shtmlI also want to make an observation of another downside of having those bolts ALL the way through the backing plate through the hull (other than 3 more holes in your boat). It will be virtually impossible to replace a bad Seacock without hauling your boat. Even if you tried to "beach" your boat for a few hours I think it would be nearly impossible to get those bolts out and change out the seacock in one tide cycle.I was able to change out a bad Flanged Seacock with the boat in the water by just backing out the wood screws keeping the seacock from spinning around. I would argue those through bolts are really not structual and most of what keeps the structural strength of the seacock is the flanged base of the seacock and the threads on the thru-hull.Just my humble opinion

Don12364 · Jan 13, 2008

I had one break right off

Years ago, prior to my Hunter, I had a 1/2" bronze thru hull break off in my hand. It had a small strainer on it for the engine cooling raw water. Luckily I was alongside cleaning the filter at the time. It needed no force at all and could have broken off at any time. The cause was that the internal diameter was a little too large and the thread was cut into the external diameter too deeply.Looking at Mainsail's excellent cutaway photo reminds me of the plumbing training I had in my youth. It seems he used a tapered thread nipple on a parallel thread thru hull. We were never allowed to do this. Always two parallel threads with sealant (paste & hemp)and a back nut. This allowed plenty of thread engagement. Some nipples were made one end parallel and the other tapered but I doubt they would be available nowadays.Either way the main cause of failure is likely to be thru hull wall failure than disengagement of the threads. Depending on tolerances and how much torque had been applied to the parallel/tapered joint it would have given more engagement and a good fitter would have been aware that too little engagement had been achieved. Dieing down the thru hull only makes it weaker. They are made parallel to accept the back nut against the hull pad and so they can be shortened if necessary. A proper job needs a parallel thread ball valve and back nut as previously noted.Problem is the occasional boot with full weight of wearer applied inadvertently to the fitting. These tall assemblies are particularly vulnerable and this is why international racing rules require a suitably sized plug to be attached to every thru hull!My boat has ball valves and I wish it had seacocks - but I'm not going to change them all. Just live a little more dangerously!

Don12364 · Jan 13, 2008

I had one break right off

Years ago, prior to my Hunter, I had a 1/2" bronze thru hull break off in my hand. It had a small strainer on it for the engine cooling raw water. Luckily I was alongside cleaning the filter at the time. It needed no force at all and could have broken off at any time. The cause was that the internal diameter was a little too large and the thread was cut into the external diameter too deeply.Looking at Mainsail's excellent cutaway photo reminds me of the plumbing training I had in my youth. It seems he used a tapered thread nipple on a parallel thread thru hull. We were never allowed to do this. Always two parallel threads with sealant (paste & hemp)and a back nut. This allowed plenty of thread engagement. Some nipples were made one end parallel and the other tapered but I doubt they would be available nowadays.Either way the main cause of failure is likely to be thru hull wall failure than disengagement of the threads. Depending on tolerances and how much torque had been applied to the parallel/tapered joint it would have given more engagement and a good fitter would have been aware that too little engagement had been achieved. Dieing down the thru hull only makes it weaker. They are made parallel to accept the back nut against the hull pad and so they can be shortened if necessary. A proper job needs a parallel thread ball valve and back nut as previously noted.Problem is the occasional boot with full weight of wearer applied inadvertently to the fitting. These tall assemblies are particularly vulnerable and this is why international racing rules require a suitably sized plug to be attached to every thru hull!My boat has ball valves and I wish it had seacocks - but I'm not going to change them all. Just live a little more dangerously!

Tom S · Jan 13, 2008

Oh Cool !

That is new to me! That is the first I have seen those "flanged only" adapters.Are those threads on the top NPT for the Groco Ball Valves ??

Tom S · Jan 13, 2008

Oh Cool !

That is new to me! That is the first I have seen those "flanged only" adapters.Are those threads on the top NPT for the Groco Ball Valves ??