Thanks for giving this a serious look. While I hadn't planned to set
a record with this sub,
is fun to contemplate. I had planned to run the boat in the 200 to
500 ft depth range with
a rebreather. Composite/foam would seem to be a good choice.
As far as the mass of the boat, yes I understand a big wet bag of water
still weighs tons.
I confess I am fascinated with the record setting human power subs.
Still a lot of mass but
very fast for very little horse power. Maneuverability is another issue.
As far as pressurized
or not, I don't see how that affects the mass, wet is wet.
As far a pressurized hull failure, I don't see much difference dead wet or dry ;-)
I think you have expressed "THE" problem. What happens to a 1 atm "wet"
sub when you
open the valve at 10 atm? We have all been told water doesn't compress.
An yet you have
a container of un-pressurized water, surrounded by "pressurized" water.
Will the pressurized
water say outside even with the valve open? I think not. Would pressure
begin to build up
inside? I think so. Crazy? Perhaps. I little like diving "in" a hydraulic
accumulator.
It sound like I need to make a small experiment with a canister, a valve
and pressure gauge,
dive it and find out. I think the key is, is it controllable?
Keep up the good work on your web site! Do you have a license to have all that fun?
Mahalo for sharing your na'auao
Aloha, Michael
Captain Nemo wrote:
Aloha Michael, Curtis Uehara pointed out your thread about the sealed wetsub idea presently being discussed at PSUBS. I used to participate there, but am not on their list at present, so I thought I'd send you an email to share what I now about this concept. The idea is one I experimented with back in the 80's, though I never considered using concrete as the hull material. The concept seems to have merit because one could flood a wetsub, seal it, and essentially remain in shallow water while probing greater depths in a hull not effected by external pressure. Theoretically, such a sub might set a World solo depth record for a 1-atm sub (presently 3,000 feet by Graham Hawkes in a DEEP ROVER), unless something in the rules states the boat must be dry inside, which I doubt. If the boat were flooded at the surface, it would be essentially 1 atm; just wet inside is all. First problem to consider is the hull material. To me, a composite-and-foam sandwich construction seemed the best way to go, as it would have at least some buoyancy when flooded. Designed right, you could get it so it was about neutral when flooded, and dive it dynamically on the planes. One concern here is will the depth pressure compress the foam sandwich and alter the displacement buoyancy ratio? It might. Problematically, you'll find that when you're running a flooded hull that is also sealed (as opposed to a free-flooding hull where the water can move in and out unrestricted) you now encounter the added problems of maneuvering all that MASS underwater. To move or turn the boat, you'll also need to maneuver the weight of all the water inside it. (That's not obvious to some folks, but it's true.) So, to get moving, your electric motors will have to overcome the inertia of several tons of water inside the hull; and it will be equally as hard to stop or turn the vessel. Another concern is what will happen if we are at great depth and the hull fails at any point? Water being virtually non-compressible, the shockwave of the extreme overpressure outside suddenly meeting the lower pressure inside the hull would result in a catastrophic shock being delivered to the hull from within wherein the water acts like a hammer. (Sort of how a depth charge works to impart damage by using concussive force to slam water against a hull.) The result would be devastating! Or, let's say we were at depth and we wanted to pressurize the hull to get out and snoop around or recover something valuable: how are we going to do that? If we use compressed air to pressurize the hull from within, we could create a void which is instantly susceptible to the external depth pressure. If the depth pressure is greater than the hull strength: we have the possibility of a catastrophic failure. Could we just open a valve and let water in from outside? I don't think so; not without risking an implosion. Remember, water is not compressible. The water already inside the sub would not be able to yield to the incoming pressure; it would have nowhere to go to get out of the way, so to speak. Again, we might experience a CATO. If you're in a wetsub and you have a SCUBA failure, you can ditch the boat and free ascend. If you are at depth in a flooded hull, you will first have to escape, and as we have seen: changing the pressure variables before exiting might be a problem all in it's own. And you'll have to take care of it while working off your backup SCUBA. When I thought about it for a few months back in the 80's, and when I considered all the complexity of making the thing work and the problems involved, I came to the conclusion a wetsub would be better in most every respect except for extended depth and time, so I passed the idea by and went on to working with ambient pressure subs, and eventually dry subs. If you'd like you can check out my website, which I've only had back online for a couple months, but it's starting to grow. And if you would like to ask me any questions, you can always write. If there's a problem with this email address (some people have trouble replying to it: a glitch in RoadRunner, maybe) you can always reach me via the message board or webmaster email at the website (below). I'm on the Big Island. Take it you are on Kauai. Maybe one day we could do a dive together. Malama Pono, Pat Reganhttp://www.vulcaniasubmarine.com nemo@vulcaniasubmarine.com