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In a message dated 12/19/2009 2:34:25 P.M. Pacific Standard Time,
ojaivalleybeefarm@dslextreme.com writes:
Hi All, Hi Brian. Not expert advice but just a couple thoughts.
I think I remember hearing about a double valve system on the application.
There was a poppet valve to prevent "splash" from getting sucked into the intake
side, and it makes sense to have a similar set-up on the exhaust.
There was a hard "gate" valve for actual diving to lock out the pipes much
like any other hull penetration.
These valves were coupled with a "drain" bypass to dump any water that gets
in there before starting up the motor. Maybe like a water trap on a compressed
air system in a shop.
Depending on how deep you go, the intake and exhaust "pipes" need to be
sufficiently thick to withstand the pressure.
The water cooling system also has a set of valves to "lock-out" the system
when submerging.
If the fuel system is diesel then you need a means of evacuating water from
the lines, as the environment will be conducive to condensation with the heating
and cooling cycles experienced between surface ops and submerged ops. Big
temperature changes there.
A diesel motor vibrates and the vibration would need to be isolated
from the hard piped thru-hulls.
On the exhaust side, the temperature changes from a "long run time" to
"shut off and submerging" will make the exhaust pipe exposed to salt water
corrode fairly quickly. The exposed parts will need to be designed for
replacement when they get corroded. Even if it's stainless, the many cycles from
hot to cold will reduce the anti-corrosion properties of the metal. Bolt-up
stuff so it can be replaced without using a torch and welder.
The valves on the exhaust side will need to have seats and seals that can
take the many heat cycles.
It's fairly complicated but should be do-able.
On my little boat, I'm going with an outboard motor that will be mounted
and un-mounted so no extra thru-hulls are needed. The steering is controlled by
the same actuator that controls the submerged steering rudders. Throttle will be
another simple actuator or maybe just a quick disconnect cable running through a
small ( 3/8 inch ) thru-hull with a ball valve.
The outboard is small enough to fit through the hatch, and the fuel tank (
gasoline ) will be small too.
A 20 horse Mercury outboard looks to just fit, and is light enough to
pick up easily.
Typically the outboard will not be carried inside the sub but I want it to
fit just in case. I expect to always have a surface boat with me, unless it's
just playing around in a lake for the day. The outboard would be un-mounted from
the sub and placed in the surface boat when diving.
I've often thought about how to add a diesel powered "module" to my sub
that would be more or less self contained in it's own pressure vessel but
connected by a couple of electrical thru-hulls for engine controls and
system monitoring. In the current design it would be basically a pressure vessel
split in half with mating flanges, hard valves on intake/exhaust/cooling
water, and the prop would be on a magnetic coupler.
Of course, being the dreamer that I am, the concept quickly evolved into a
pressure cabin, fuel tanks, gen set, extra battery banks, bunks, galley, and
head stretching the thing to 24 feet long !
I think I showed you the concept sketch once when you visited.
Anyway, good luck with the diesel and keep us informed as the design
progresses. It sounds very interesting.
Frank D.
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