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I take it then that the cockpit will be exposed to
the ambient sea?
I looked at the pics on Frappr. I think
you've got room close to the boat's CG for a variable tank that can be separated
from the cockpit. You can keep your toes bone dry (unless you pee yourself
when you see the bottom rushing up at you) by having an isolated VBT. You
needn't have a one-atm strong tank if you go with the compensating reg
and two bilge pumps. You need nothing more than a DPDT switch
connected to the two pumps. Flip the switch down (for "go down") and the
pump outside the tank (exposed to the ocean) will introduce water into the
tank (air in the tank will rush out the reg's mouthpiece exhaust ports) and
make Octopus heavy. Flip the switch up (for "go up") and the pump located
INSIDE the VBT will eject water to the outside, activate the second stage dive
reg to "breathe" air through the mouthpiece into the VBT to compensate
it. If you want, you can forget having a reg dedicated to the VBT by
having a line running to the ambient cockpit. By having a sight-glass
you'll always be sure the VBT won't overflow up the line into your cockpit -
your feet WILL get wet.
But, heck, the bilge pump you were planning to
install at your feet - in its own well - will prevent that right?
:-)
This system avoids having to crack flood valves
manually, activating vent valves, monitoring the Delta-P's
(VBT tank pressures), installing overpressure valves, etc. The scuba
reg already has exhaust ports built into it and will vent overpressures
automatically (if the VBT is isolated).
Personally I prefer a dedicated reg - it reduces
hull penetrators by one. It does, however, add slight complexity to
the system.
Rick L
----- Original Message -----
Sent: Saturday, March 04, 2006 5:14
AM
Subject: Re: [PSUBS-MAILIST] Free
Surfaces solution!
Hi Rick,
"Hi, Joe, et al . . . I'm curious about the
foot-well thing and the nasty buoyancy thing. Could you elaborate a
bit?"
Sure thing Rick. If I want the ability to touch
down "softly" on a sand patch and stay there with my design as
is sans thrusters, I will need to vary the buoyancy slowly to negative
and balance on the keel with short bursts to the saddle tanks. The foot well
is nothing more than a variable tank then. It's the only place I can use
because of the battery box.
Here's the potential nasty part. A 1 atm design
never changes anything in the crew cabin when playing around
with the variable tank. I'm not worried about sinking into the abyss because
I'm never going to be in deep water but, I do worry about running hard aground
with 2000 lbs + of internal lead ballast and things could break. That
crazy Newton inertia thing.
Overcompensate because your now worried about slamming
into the bottom now, and you could take the fast track back to
the sun with Boyles Law now becoming a bit of an issue.
My design may not be appropriate for ever trying to
touch down, I'm still looking at this and various options....I just don't know
yet.
Joe
From: "Rick and Marcia" <empiricus@telus.net>
Reply-To:
personal_submersibles@psubs.org
To:
<personal_submersibles@psubs.org>
Subject: Re:
[PSUBS-MAILIST] Free Surfaces solution!
Date: Sat, 4 Mar 2006
00:49:02 -0800
I am contemplating flooding the
pilots foot well as a variable tank but, as Dan pointed out, things can get
a bit nasty buoyancy / control wise in an ambient.
Hi, Joe, et al . . . I'm curious about the foot-well
thing and the nasty buoyancy thing. Could you elaborate a
bit?
The only reason I can see for flooding a footwell is
to reduce the amount of required compensating air into the cockpit, in
other words, to save compressed air. Many moons ago, before I decided
on the reg compensation scheme, I considered using a kayak skirt to keep the
wet sloshing surface in the cockpit from splashing around (unlike the
Sportsub, I wanted my boat to incline like a "real" sub). Everything
up to the skirt would be wet, everything abouve would be dry. Kent
Markham with a kayak skirt.
There seems to be a widespread feeling in the
list that ambients will have buoyancy issues. Boyle's Law will only
come into play if you have an open bottom in your cockpit.
Maybe I'm missing something here.
Rick L
----- Original Message -----
Sent: Thursday, March 02, 2006 7:31
PM
Subject: Re: [PSUBS-MAILIST] Free
Surfaces solution!
Bill,
I see what you are saying. Sportsub is clever that way and even smarter
in their placement of the entry. But, I will be lucky to have a few
inches under the keel dockside at most ramps here.
If I land on the bottom, I have to balance her on her
keel with little bursts to the saddle tanks like a BC. This makes ever
leaving the boat an absolute no no. I won't be doing twin keels
because of increased wetted surface...that and the lower hull peppered
with limber holes as is, would be a bit much to ask of any decent
surface running.
Also, the discussion regarding "fine tuning" of the numbers has me
re-thinking things a bit. My deciding to design in the ability to leave
"snorkel depth" also leaves behind the hydrodynamic / energy advantage of
the 14 hp diesel, and its hull effect. That gives me the reserve to
force her under even if the boat were significantly positive, how much
positive?...(me not know). I lose that advantage as soon as I
would break away from the surface and that makes things a bit tougher for
me.
I am contemplating flooding the pilots foot well as a variable tank
but, as Dan pointed out, things can get a bit nasty buoyancy
/ control wise in an ambient.
Let's see what develops.
Joe
From: "Akins" <lakins1@tampabay.rr.com>
Reply-To:
personal_submersibles@psubs.org
To:
<personal_submersibles@psubs.org>
Subject: Re:
[PSUBS-MAILIST] Free Surfaces solution!
Date: Thu, 2 Mar 2006
21:00:49 -0500
Glad to help Joe.
See how the exact same "center board trunk"
idea can be used to create an open bottom hatch that the water level is
under by a few inches
and therefore would not slosh into the
ambient boat? No need for a hatch if you want to cut down on time
and costs and don't plan to be
sitting outside atop the sail. Just use
your trunk hole to enter and exit the sub. One thing to remember if
using this for going out diving from the sub.....
remember you were already pressurized at
whatever depth the sub was at and for that time. Now if you go outside
and dive deeper as a diver,
you must calculate your previous
compression pressure and its time and then treat your outside dive just
like any other repetitive scuba dive so
you will not require deco. Even if you did
decide to put in an upper sail hatch, or deck hatch, it would still be
very nice to have a big hole in the floor
that you can just jump out of the ambient
sub thru.
Bill Akins.
----- Original Message -----
Sent: Thursday, March 02, 2006
6:40 PM
Subject: Re: [PSUBS-MAILIST] Free
Surfaces solution!
Yes you did Bill but, I didn't put 2 + 2 together
at that moment! I was still thinking of a flat plane.
Thanks so much!
Joe
From: "Akins" <lakins1@tampabay.rr.com>
Reply-To:
personal_submersibles@psubs.org
To:
<personal_submersibles@psubs.org>
Subject:
Re: [PSUBS-MAILIST] Free Surfaces solution!
Date: Thu,
2 Mar 2006 17:30:03 -0500
Hi Joe.
Remember when I told you to partially
enclose the ballast tanks to prevent not only burping but also to
aleviate your free surface problem and just leave a small hole in
their bottoms for ambient operation?
Looks like you came to the same
conclusion.
Bill Akins.
----- Original Message -----
Sent: Thursday, March 02,
2006 12:08 PM
Subject: [PSUBS-MAILIST] Free
Surfaces solution!
I really did not want to seal off the soft tanks
completely in my ambient design to keep the "free surfaces"
in check. I found the solenoid flood valves unnecessarily
complex for my application, plus the issue of access and
maintenance.
This is truly bizarre and a testament to the
function of this list. Not to encourage off topic discussions
but...
The rocket discussion made me think about the
pyrotechnics of solid rocket motors, which made me think of
flares, which made me think of the time years ago, Freddy got
drunk and set his sail cover on fire one July 4th with a hand
flare.
That boat had a centerboard
trunk!!
Hmmm, centerboard trunk!!....led me
to this solution in five minutes!
You guys are just bursting with design ideas!!!
:)
Thanks
Joe
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CAN-SPAM Act of 2003. Your email address appears in our database because
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complete within five minutes of our server receiving your request.
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personal submersibles mailing list complies with the US Federal CAN-SPAM Act
of 2003. Your email address appears in our database because either you, or
someone you know, requested you receive messages from our organization. If you
want to be removed from this mailing list simply click on the link below or
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