Originally Posted by aboutgone
I went with Conbraco Apollo flanged three hole valves and thru hulls...wanted to go with the flanged adapter plate which is NPS,but all the ball valves i found were NPT.
I cut epoxy fiberglass
phenolic backing plates
an inch bigger than the valve base, shaped them to the hull
and 5200 was applied to all surfaces....nice to get rid of thoes huge conical sea cocks on my 30 year old CSY
.....wanted to go with Marelon but Forespar didn't make thru hulls long enough for the thick glass hull
on the CSY's (2 1/2 '').........Ed
You probably should have read or researched a little further and you would have seen they do exactly as you wanted them to do.
The whole idea of the Groco flanged adapter is that the threads on the top of the flange, or inside of the hull, are NPT (tapered cut) just like a standard ball valve is.
The threads on the bottom of the flange, or facing the outside of the hull, are NPS (straight cut) to match the straight threads of a thru-hull.
The flanged adapter was invented for a number of reasons all of which make it one of the best inventions as of late for seacock technology.
Flanged Adapter Benefits:
#1 Matched threads between BV and adapter and thru-hull and adapter.
#2 Stronger than slapping a BV on a thru-hull and as strong as a flanged seacock as measured by cross sectional thickness.
#3 Saves money
down the road because the valve replacement, which is always the first to fail, takes less than five or ten minutes and can be done in the water
#4 Allows for easier plumbing
configuration when low internal height to cabin sole
etc. limit the total valve height.
#5 Can be permanently mounted to the hull and allows easy valve replacement in any location in the world without requiring a haul-out. NPT ball valves are easy to find anywhere in the world, even in remote
#6 Makes future valve replacements
far less expensive and considerably less invasive and time consuming.
#7 BV are less expensive than flanged seacocks so the second time you change a BV you are way ahead financially.
#8 Carrying one or two sizes of spare BV's, as a world cruiser, is much cheaper than carrying spare seacocks.
#9 Spare BV's can be used in a pinch for far more on your vessel than can a spare flanged seacock. A 3/4" BV is a good spare to have but a spare 3/4" flanged seacock is only a spare seacock.
#10 In a remote
location, when you can't find a replacement seacock, nor a place to haul out
or beach the vessel and wait for a tide, you can use any, brass, stainless, bronze or even copper NPT/NPT ball valve to get you back in business. Of course if you use sub par metals be sure to change it back out when you get to a local where bronze valves are available. If a flanged seacock fails to open or close you will need to replace the entire unit not just spin a valve off and replace it.
The #1 failure of BV's, as I have experienced, is the ball and seats not corrosion
of the bronze body or thru-hull. When folks do not open or close the valves enough growth attaches to the closed ball and when opened it digs up the phenolic valve seat or scores the ball. The same type of scoring can happen on tapered cone valves, seen it, and repaired it, if not used enough.
Having replaced hundreds of seacocks I can count half the fingers on one hand the number of times I saw a thru-hull that was not reusable if it had not been destroyed by removal
due to 5200 or similar. I have seen 35+ year old thru-hulls in perfect condition on numerous occasions. If you've had enough corrosion
to destroy your thru-hull then your prop, prop shaft, rudder
shoe or strut will also be quite damaged.
I have not yet seen a 35 year old BV, in the marine environment
, still operable. I'm sure there may be some out there that still work but I have not come across one. On the otehr hand I have seen hundreds of re-usable thru-hulls at the 30-35 year mark making them almost permanent or at least multiples more permanent than a BV. I have also seen 35 year old tapered cone seacocks still operable after re-lapping.
It is almost always the BV that fails and not the thru-hull unless it was broken off because it was not installed into a flanged seacock or flanged adapter.
I cracked a thru-hull on my own boat in a storm. This was a valve on a thru-hull with no flange. My boat was quickly hauled and every seacock converted to flanges and through bolts..