----- 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
