[PSUBS-MAILIST] Propane sub

[CWall@swri.edu]

Craig.

good evening.

1)you are designing a vessel capable to travel 200miles, but you do not give
depth ,(as far as i understand), importance, you do not plan to build to
have the capabilitie to dive deep ,

  That is correct. I do not plan to operate below 100 ft.


what will happend when you are travelling close to shore, but not so close
say, 12 miles, the situation look like this, is dark is fooggy, the seas
just went from 6 to 14 ft, because a front is aproaching, 

  Stop right there. This is an operational question; the correct answer is that
 you MUST pick your weather with a boat like this.   In this respect, the
situation is no different than with a small boat, except for the issue of
swamping through a hatch opening. I plan to have good ventilation via snorkels,
 and the swamping issue is met by keeping the hatch closed (and a kayak-style
gromment for those times when you do have to pass through in sloppy weather.
But the real answer is- don't get stupid where the weather is concerned.

you are on a
traffic area the draft of the container carriers are arround 12 ft, 20 if
the seas are moving. if they are a submersible will be pretty unconfortable
if sailing in less than 80 ft,

  That is true. Comfort is lacking in a vessel like this, but again- this is no
 different than small sngle-handers, which I am quite familiar with and willing
 to endure.  I suppose you are saying you wouldn't be. Again, you'd have to be
an idiot to choose lousy conditions, and this is an issue that can be avoided.
Discretion is the better part of valor.

 so the question is, how the fuel you are
carryng will react if a vessel collide whith you?
a) you are on the surface
b) you are underwater

  In both instances, because the propane is within the primary structure and in
 it's own DOT rated impact resistant bottle- 15 lb trailer bottles, at least in
 this first iteration, I suspect that I would have more to fear from a cranial
trauma than a hull impact severe enough to breach the propane tank.  And if it
did, please recall from my previous posts that the boat will be very near
neutral bouyancy with ALL ballast flooded, and I would need only drop lead shot
 or a keel weight to retain positive flotation.    As long as the crew
compartment is not breached, I see no reason to abandon ship. 

2) you are at the dock on the local marina ready to go for a day run, you
vent out to partyally submerge, as to check the systems, and because is
sunday and there is a lot of people arround , some idiot just trough a
cigarrete butt rigth by your vent, (you know murphy,dont you?)
a) what happend?

  It should have been clear that I'd have been using that propane to run a
generator to charge batteries- so there should be very little venting. But
vents would be led to a burnoff stack, and the propane simply ignited as it is
vented.  This is mainly because no one likes the smell of mercaptans, and when
they do smell it they become afraid.  Of course, I could always buy motor grade
 propane without mercaptan, but I think the odiferant is useful to the operator
 for detecting leaks.

3) you have been going for hours , and the conditions are bad, you want to
lay down and sleep some, when you are sleepping, propane sweepts in and
since is heavier than air, sinks and cover your breathing space, murphy
again

  Bad conditions are generally avoidable.  I also spend some long weekends in a
 confined space with propane plumbed in....in fact, I slept in such a place
last night: my little weekend trailer at the airport.   With no plumbing
entering the crew compartment, and an appropriate monitor in the crew space, I
think I'll sleep ok.

How will you plan to go arround the regulations for safety on the waters,
when trasporting a flamable gas  or tring to get permission to enter a
harbour or a dock
Do you have any friends on the coast guard?
4)

  Screw them.  I'll be using DOT approved propane bottles and if necessary I'll
 fire up the grill.  

Next question.


5) propane tanks are heavy, do you work out?

15 lb propane bottles I can flip over my shoulder with one finger. Next
question.

There is cars that drive on propane and machinery too, i have use them, they
work, i think that your alternative is certainly posible,and i also think
that it can be built whith a degree of safety on it, people live by volcanos
too.
But having so many others types of fuels available, dont you think this is a
to some degree a bit impractical aproach to propulsion.

Nope.  Especially because as an approach to propulsion, it also satisfies the
ballast problem very neatly- IF you don't plan to go deep.  1 lb of propane
will displace between 400 and 500 lbs of water at the surface.   The ratio is
still 100 to 1 at 100ft.    And because propane is liquid, the pressure does
not drop off as the tank is emptied until all the liquid is gassified.

Craig Wall