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Brian,
I agree with Jim on the clearance, and you'd be surprised how much water
can squirt through only .050 inch clearance. Don't forget, in a P-sub you
don't have many pounds of wiggle room for being to heavy to get back to the
surface and even less wiggle room to get unseated, turned around and contorted
into position to deal with a water leak.
Once I was submerging in the passenger position with someone else in the
pilots seat of my sub. I was instructing the guy through a dive. He
secured the hatch dogs when I told him, but barely tightened
them. When the hatch seal submerged a thin spray of water wafted down on
both of us. It happened so fast, even with the hatch in less then a
foot of water, that neither of us could react until we were pretty wet. I
grabbed for the MBT blow valves and brought us back up really quick. We
only took on about a quart of water plus what was dripping from
our pants. Some of those drips had a yellowish tint, I might
add.
Immediately after the incident I realized if we submerged any deeper the
pressure on the hatch cover would have sealed the leak, but there was no time to
think that through with water spraying in.
Dan H.
----- Original Message -----
Sent: Tuesday, January 06, 2009 7:32
AM
Subject: Re: [PSUBS-MAILIST] Soft ballast
venting valve
Hi Brian,
I agree with your concept about shaft/ fitting and thats my reason for
being very comfortable with it while Frank is not.
I have to take exception to your clearance. Mayby it's a typo, but 50
thousanths is WAY to loose for ANY O ring seal in mu opinion and extrusion is
expected.
I will hace about 5 -10 thousandths. I do this by boring the sleeve
slightly undersized then welding the sleeve in place. After welding ream to
size with a propersized reamer.
I wish I could get tighter, but doing the reaming freehand that's the
best result I can get.
I am also using a Block V seal which I feel is better than an
oring.
The idea ame from Gary Sluis.
Best Regards,
Jim K
----- Original Message -----
Sent: Tuesday, January 06, 2009 12:53
AM
Subject: RE: [PSUBS-MAILIST] Soft
ballast venting valve
Hi Frank,
When you figure the diameter of the
shaft and the diameter of the shaft fitting, that the shaft goes into, there
is only a difference of like 50 thousandths of an inch. Even if you
forgot to put the O ring in that fitting, it's not like going to be Niagra
falls coming into your boat. You could probably put some bubble gum on
it and the leak would stop. You would be able to address a
problem like that as soon as it occured. The hydrolics would
add too much of an extra thing for me to deal with. I wonder if
there is a way to smooth out those cast fittings so they could be
polished? I will probably put a T into my ballast vent valve
inbetween the valve and the ferro body for HP air. It would be nice to
have a LP air generator for "topping off" the ballast air so as
to float yourself higher on the surface. I seem to remember the Tang
would do that to try and get maximum speed on the surface, they would
run the compressors into the ballast and the exess air coming out the bottom
of the ballast would cut down on the friction against the water.
giving them an extra knot per hour speed.
Brian
Hi Brian. That makes good sense. Save a few bucks and go with what
works. As for matching up the two materials, There's always going to be
the corrosion factor to deal with. Zinc sacrificial anodes will help but
not eliminate the problem. On the plus side, bronze and stainless won't
"gall" when screwed together. I'm using a lot of brass bolts mated to
stainless lock nuts. Although replacement of the brass will be needed
sooner than stainless bolts would, at least I know I'll be able to get
them apart without a big hassle. Some places I'll be using stainless bolts
and brass nuts, because I need the extra shear strength of the stainless,
but again, it comes apart easily after a long time in salt water.
I too am going with the bronze valves. They are
pressure rated to 600 psi, are cheap to replace, and when polished they
look really good. Very "Capt. Nemo" like. Also, the highly polished
surface corrodes much slower than the regular cast surface. I've got quite
a few of the interior valves, unions, elbows, nipples, and related
bushings and adaptors and when polished, they look really good. The HP air
will be like yours, Swagelock and stainless tube.
I haven't cut in any through-hulls yet, but those
will all be stainless nipples. Then a bronze ball valve on each one where
it enters the sub. Complete shut-off at every penetration if a problem
develops. Even the electrical through-hulls will be valved off. I want to
get all the components mounted before I start cutting in the nipples. The
largest is 2 inch, while the smallest is 3/8 inch. The main ballast will
all be 1 inch. Maybe a little slow to submerge but I don't expect that to
be a problem.
You said you're using rod linkage to operate
your valves? Wouldn't a small hydraulic cylinder work just as well?
When the weather gets a little better, I'll
cruise down on my bike for a visit and a cold beer. Frank
D.
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