So Dave,
With all that said, what do you think of this installation? (Port cockpit drain with sink connecting in "T")
The wood blocks were preexisting. The faint greenish color on the hull below the block is stain from corrosion from the old bronze seacocks. The wood blocks seem to be attached to the hull with some form of semi-hard tan stuff. I don't know what it is, but the yard drilled the blocks for one and a half inch thru-hulls an reused them, tan stuff and all. The old cockpit drain, through-hulls and seacocks were bedded with silicon and some of this tan stuff. (The head through hulls by-the-way were bedded solely with silicon.)
The white goop in the photo is 3M 4200. The through-hulls was bedded in 4200, and most of the hose connections also use it liberally. The vertical hose is that white santition hose we have been discussing on this thread, and the black striped hose connecting the sink is one and a half inch hose that West Marine sells as bilge pump hose. That is a West Marine nylon "T".
Note that the valve is mounted on the threads of the through-hull stem. It is not a traditional seacock.
After I saw the installation, I was surprised that they had not instaleld seacocks, sicne that si whatthey had removed. I discussed the installation with the yard manager, and he told me that this is their SOP, although they will install the flanged sea cocks if a client specifically requests them to do so. They feel that there is no difference in safety or durability of the through- hull, although they predict a shorter life for the valve than with traditional seacocks. They don't even seem to stock traditional seacocks in their chandlery.
With the exception of the flange and the fact that the sea cocks sold by West Marine have drain plugs, the valve mechanism itself appears to be very similar: Bronze with an electrically isolated stainless steel ball. So the main issue is flange with bolts or screws into the backing plate vs. tightening nut on the through-hull as a means of attachment to the hull.
On the one hand, it seems to me that a through- bolted sea cock adds three more holes to the hull but it is a very secure fitting, Screwing a traditional seacock into a wooden backing plate would prevent the seacock from rotating and there by loosening, but seems less secure than through bolting, and it would be impossible to tighten if the bedding fails below the block, without unscrewing the seacock screws.
Now these older primarily-mechanical systems were developed before 3m 4200 and similar adhesives were invented. With the advent of new adhesive bedding compounds, perhaps a tightening nut on a through hull and inline valves is a satisfactory or even a better approach, since one can tighten the nut if necessary.
However being the kind of guy who like traditional boats, I am the kind of guy who would sleep better with traditional seacocks. Any thoughts?
Absent an existing backing plate in good condition, the yard uses fiberglass backing plates. They did this on my head through hulls.
This installation conforms to nothing that I have seen in any book on the topic that I have read. but then again, I read mostly old books or those by traditionalists. My yard says they do this type of ball valve installation regularly and the installations work just fine, and last for many years.
This isssue alone would make a good topic for a thread. The cockpit drain system is now different than what I had before Before I had traditional sea cocks that were merely screwed into the backing plate with half-inch screws, and not through bolted.
My two head sea cocks were solid bronze tapered plug style valves with an integral flange on the base of each seacock, and no backing plates. They were bedded with nothing but silicon. Once the exterior mushrooms were cut away, they just lifted off the hull. This was probably an original installation folks. Spooky as that seems
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