----- Original Message -----
Sent: Monday, January 24, 2005
12:43 AM
Subject: Re: [PSUBS-MAILIST] Wetsub
carrier water transport systems
Dear Vance,
Your ideas on pontoon/pod combinations
certainly have merit and I will consider them as the modification and
refurbishment of my wetsub project ongoes.
I have purchased and plan to install a
single 74lb thrust minnkota electric motor.
Your suggestion is excellent regarding
putting in a forced vent system to rid hydrogen from the battery pod
while I am charging, I plan to do that.
You spoke of sea water creating "green gas"
from covering the batteries. I take it this is chlorine gas correct? I
know hydrogen is highly explosive, but is chlorine gas
explosive as well?
What I need suggestions on now is how to
rig the battery pod so I can recharge the batteries without removing the
large end cap
and disturbing the O ring. I imagine it
would be having some kind of waterproof cap that unscrews from a short
tube coming out of the battery pod,
wherein I could access the wires to the
batteries and hook them to the charger. Any suggestions on how to best
accomplish this would be greatly appreciated.
Your warning about trash getting between
the o ring and its bearing surface is one I will remember. I see from
your experience how important it
is.
I know how to hook up my scuba regulator to
equalize the battery pod and motor housing which will equalize together,
but what I have been reading
about and want to install is a leak
detector which will automatically detect any pod leaks and somehow warn
me with a guage or warning light and will
automatically vent air into the pod that
will force any water out thru the crack it came in or at least only
allow a small amount of water to remain inside
that will not endanger the batteries until
I could surface and get the pod out of the water. In order to stop any
water entering a crack on the pod the air
pressure inside the pod would have
to equal or exceed the outside water pressure and I need a leak
sensor that would somehow tell my regulator when to
force air into the pod and when to shut
off.
I have read and seen a drawing of a battery
pod with a open tube on the bottom of it (similiar to a upside down
glass underwater)
and the pod stays dry by the air pressure inside it always being greater than
the outside water pressure. Then as the water pressure increases on
diving, the water tries to go up further into
the tube under the pod, and as it does this
it contacts and completes the circuit between two wires which goes to a
device (what device? here is where I lose it) and this
device
then somehow instructs how much air should
be vented into the pod and when the air pressure blows the water down
beyond the exposed sensor wires the device then instructs the
air to shut off until the
water touches the wires again as you go deeper and water pressure
increases beyond what your pod air pressure is again. Any advice or
links or sites you or
anyone else knows of that has this kind of
information that you could send me would be appreciated as
well.
I had previously tried to post photos here
but when you include photos in this system it apparently not only does
not allow your photos to go thru but also blocks your text as well.
Twice before
I tried and neither the photos nor the e
mail text appeared in my e mail as my text e mails normally come to me
in my inbox when I send them out to the psubs mailist.
Bye the way Vance, what does "LRP"
that you referred to in Hawaii mean and what did they do? The only thing
I know about that term is "Long Range Patrol".
Kindest Regards,
Bill Akins.
Bill,
I think you're making too much of the various
complications. You're going to build pontoons, and battery pods, and a
compensation system anyway. It just seems like a reasonable alternative
to build them as a unit. If not, have a look at the LRPs they used so
successfully in Hawaii. If you're dealing with surface chop, then
submerging the pontoons on their own ballast system would let you garage
the wet sub without banging it up.
I don't know which design you
are using, but it doesn't take much to stick three or four batteries in
a tube for 50 to 75 psi service. If you are going to use one, and that
is certainly reasonable, then put it inside and sit on it, or do like
Perry and shove the whole thing aft and get it completely out of the
way. One nifty solution was to combine all this. We mounted a 3 hp
thruster on the back plate of the battery pod, sort of like a DPV on
steroids, and built it into the stern with just the prop sticking out of
a faired section and the rudder and nozzle mounted to that. It worked
(and still works) fine.
What kind of motors? The big Minn-Kotas
give you a lot of push, and they are cheap. A couple of those ought to
get you around pretty well. If you want a hot rod, try four. They put 4
of the 3/4 hp permanent magnet thrusters on the back of the Lotus wet
sub, and it ran great. Batteries were 4 X 6volt 220 amp Trojans in an
oil filled box with a couple of wraps of tygon tubing for compensation.
Cost about 500 bucks start to finish and never caused a problem.
However, I still prefer the dry pods. Put a forced vent system
on it, so that you can charge without disturbing the seals, and you'll
be a much happier camper. I once took a ride in the PC-9 with a leaky
pod. The fellow who was piloting on that dive was new, and had failed to
switch the leak detectors on--didn't realize it until we were on the
bottom. We got home without dropping the emergency weight, but it was a
near thing, and cost us fifteen out of twenty-four batteries on that
side. Sea water and batteries make green gas, and will turn the whole
thing into a gigantic bazooka, so keep that in mind. It made me very
cautious about my o-rings, I can tell you that. A piece of paper match
across the seating surface caused the leak--a very small piece, I might
add. It doesn't take much.
Vance
