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RE: [PSUBS-MAILIST] air pressure in ballast tank while surfacing

Jens, 
The sub I am building I figure that it is much easier to recharge
Electrically than with high pressure air.  1st where do you get your air
from when you are just breaking the surface? 2nd what is the water volume of
your ballast?
I am using an electric driven pump and have worked on the basis that 2
minutes of pumping at 1200  watts 400 litres/min should get rid of most of
my water.  The air gets sucked in through the MBT vents and I am closing the
water inlet valves before pumping.  That costs me 0.04 kwh out of 15 usable.
I don't get to use up my scrubber by huffing and puffing for 10 minutes of
manual pumping with the hatch still closed.  Pumping water is more efficient
than pumping air I think. Pumping air to 1-2 psi you will find tough. My
situation is a bit different in that I have a theoretically hard MBT
(although it is fibreglass). The MBT water vent valves are pneumatically
operated and remain open when blowing the tanks but even if closed are
relief style set at 1/2 psi. I want to conserve hp air as well.  I suggest
you get a rubber pontoon boat which has air chambers the same size and pump
it up by hand and see how knackered you are after that!  Regards,  Hugh


-----Original Message-----
From: owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of Jens Laland
Sent: Wednesday, 19 May 2010 11:25 p.m.
To: personal_submersibles@psubs.org
Subject: RE: [PSUBS-MAILIST] air pressure in ballast tank while surfacing

Hugh

[it appears that my first attempts to post this message, with attachments,
simply failed... so here is a stripped version without the images]

** What sort of a pump.

I wasn't thinking of a hand pump, but a manual pump: something like a
pedal driven membrane ('bellows' is probably more to the point) pump with
chain & sprockets (bicycle overdrive) and a small fly wheel.

** A hand pump would be a bit slow!

Yes, and that's why I hope my own idea of a pedal driven pump would
perform somewhat better.

** Spa pool pumps are very fast and good.

I thought of that, but they do consume electric energy.

** I am doing similar but with closed buoyancy and using a pool pump to **
pump out the water rather than an Air pump to pump in the air.

This is interesting, and gets me thinking of the Seehund (ww2 midget sub)
and how one of its crew were able to drive the boat at full speed upwards
and as they broke the surface, with a hand on the air vent valve of the
forward ballast tank, ready to close it the very split second the the boat
stopped 'in mid air'. This way, with the forward end of the boat now
barely afloat, they used the hand pump (ref. attached photos) and 'pumped
out the remaining water' (I assume they referred to the forward ballast
tank only, and used compress air to blow their aft ballast tank). This
bilge pump could handle 70 liter (18.5 gal) per minute (at 90 double
strokes).

Best regards,
Jens Laland

PS.: Images can now be viewed here:
http://traktoria.org/files/seehund/pumps/




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