RE: [PSUBS-MAILIST] Propane sub

["Greg Snyder" <snyde032@tc.umn.edu>]

Hi Craig - This may be a little off topic, but in all of this talk about
propane, I began to wonder - do you know if anyone is using other chemically
inert gases for ballast purposes? I'm a little removed from my chemistry,
but how about nitrogen or the like?
I know you won't be able to use it as fuel, which would defeat your
purpose - just wondering.
Thanks,
Greg

-----Original Message-----
From: owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org]On Behalf Of
CWall@swri.edu
Sent: Friday, November 10, 2000 9:17 AM
To: personal_submersibles@psubs.org
Subject: [PSUBS-MAILIST] Propane sub


Craig,
	This comment is not intended to be offensive but I think you're being a bit
naive in assuming that just because many of us don't share your depth of
knowledge regarding propane, we are going to sit by without expressing
concern.  Keep in mind that this forum is for people who are interested in
submarines, there is no entrance exam (fortunately for me :) ).  I beleive
that it was not so long ago that one of our number was killed under
circumstances not too dissimilar from yours, so it is understandable that
everyone is a bit edgy about ideas they view as dangerous.  Also keep in
mind that a large part of the reason that none of the "high grade ore" is
around any more is that they didn't like all the new and dangerous ideas the
rest of us were proposing and got tired of trying to protect us from
ourselves.
	It seems what you're asking for is a critique of an engineered design, like
"hmm Craig, it seems you have that valve drawn backwards" only there is no
drawing so all you're getting is an unwelcome sanity check.  I certainly
wouldn't presume to critique something based on a half explanation and no
drawing, but I might say something like "Propane?  I don't know... my
neighbours BBQ exploded last week."
	Anyways, I do have a question here, which I will ask you because you seem
to be a reasonably clever fellow.  Have you given any thought to propeller
design?  I believe you mentioned a large diameter, slow turning prop with a
typical 1/2hp power input (could be wrong as I just read most of this thread
and that was at the beginning).  Are you going to design it yourself or do
you have something else in mind?

Wade

Wait one more thing before I jump off my soap box...  A buddy of mine, who
is a very smart character and an excellent engineer once locked his keys in
his car with the engine running, twice in one week.  The point is that you
shouldn't jump at people for suggesting common sense issues just because you
have a reasonable technical grounding, because they might save you one day
(although I never did suggest to my friend that locking your keys in your
car with the engine running isn't a good idea).

****************************************************************************
***
************


  Wade, no one is perfect.  I've made my share of dumb mistakes, and that
shows
 no sign of stopping.  However, as an experimental aircraft designer and
test
pilot, I put my butt on the line regularly, and I make damned sure that I
have
a way out when thing turn ugly.

 How many times do you think I need to be reminded that propane vapors are
explosive?

I posted about a design *concept*, in enough detail to make it clear what
the
initial configuration was to be, and hoped for a broad base of intelligent
enthusiasts to point out hidden flaws- and instead I got this endless
repetition of "you'll blow up".   Frankly, it has been disappointing and
insulting, or at least the posted respnses have gone that way for the most
part.

Fortunately, you are incorrect when you say all the high grade ore left;
they
are stil reading but are not posting. I've been talking to a few and as I
said
before, I now have some welcomed additional resources.   Anyway....

...Propellor design *is* a concern.   Unless I accept a "single speed" boat,
efficiency will suffer with a fixed pitch prop, and I'm not much interested
in
complicated variable pitch designs.

My tentative solution, which is palatable mainly because I do not place a
premium on the time it takes to make configuration changes in operation, is
to
use removable props and literally go over the side to change them out.   A
"compromise" prop would allow me to operate without doing this, but having a
"low cruise" and a "high cruise" prop as well would enable some efficiency
gains over long distances.   Bucking a wind or current would require more
power
 and/or speed, while traveling with the wind is an opportunity to go slower.
The actual pitch changes would be fairly small, however, so what it really
amounts to is spare props with some variation. It also depends on the engine
and motor characteristics.

There are some other considerations, like possible fouling- and then there
is
the possibility that I might actually want more than one prop shaft- leading
to
 more than one set of props.  If I get the boat small enough, I may want to
actually row the vehicle, in which case removing the props altogether nets
you
a fairly large drag reduction. The same goes for sailing the boat downwind
and
especially off the wind, if I were to fly a kite attached to the hull, for
instance. Remember, I'm putting a lot of emphasis on range- one way or
another.


The upshot at this stage, however, is that I will likely use outboard motor
props in the 5-10 hp range and turn them slower than they were originally
designed for, after doctoring them myself.  You'd be AMAZED at the
performance
increase possible after a couple evenings in front of the TV with an
aluminum
alloy prop and a pocket knife!     This attention to the leading and
trailing
edges REALLY pays off, especially at low power, the only downside being a
much
more delicate prop- but when you have spares and the prop isn't being
screwed
through sandbars, it's quite a profitable modification.

Herve seems to think I'll be a huge risk for everyone in the vicinity, but
remember: I want to be able to go out completely unsupported and be gone for
days at a time. I don't WANT anyone around anyway! I anticipate launching
and
recovering unassisted and at uninproved facilities like beaches.  I place a
premium on low trailering weight. And the last thing I want is a bunch of
complicated machinery, at least a bunch of *essential* complicated
machinery.

Well, after all this, I'm more inclined than ever to bulid the boat.  And
here's a challange:

I have identified a serious potential problem with the design as I've
projected
 it.  I also have the solution, and that problem and it's solution have
enabled
 me to solve one of the last of the really sticky design requirements.

The problem, the solution, and the design breakthrough are all
straightforward
and follow one from the other.

I will send $20 to the first person to identify the basic problem, and $100
to
the person who can successfully figure out all of it- the problem, the
solution, and the breakthrough.  I have already posted text containing a
direct
 reference to the "sticky design problem" the "breakthrough" overcomes.

You guys have until noon next friday to figure this out. Let's see what this
group can do.

Craig Wall