----- 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
