[PSUBS-MAILIST] Reserve buoyancy

["F. Marc de Piolenc" <piolenc@archivale.com>]

I've been silently following the tender/reserve buoyancy discussion. As 
my primary interest is in salvage rather than sightseeing, I have 
assumed from the beginning that any sub that I build or am involved in 
building will follow safety criteria more like those of cruising Naval 
submarines than research subs. But now, reading the report of the 
salvage of the Alvin by the US Navy, I see that the allowances for 
research subs are inadequate.

Aluminaut was selected for the salvage op because she was the most 
autonomous and robust of the submersibles available. After her first 
dive, when she spent several hours trying to insert the lifting toggle 
in Alvin's hatch, she surfaced with her batteries exhausted. It proved 
to be impossible to recharge her at sea, because the main hatch had to 
be kept open to allow hydrogen to escape, and when it was left open she 
shipped water! She had to be towed to sheltered water for repairs and a 
recharge. This is all the more remarkable because Aluminaut is the most 
seamanlike of all the research submersibles that I've actually seen.

Battery vented into the crew space? No means of airing the boat without 
leaving the hatch open? I can understand not providing a separate 
snorkel or air-induction trunk - this is a deep diver, and every 
pressure-hull penetration is a potential failure point - but in that 
case the saddle tanks should have been made larger and some means of 
fitting a funnel over the main hatch to prevent water ingress should 
have been provided. And as for venting the battery into the crew 
compartment, ANY arrangement is preferable to one that exposes the crew 
to hydrogen, or worse - chlorine!

http://www.archive.org/details/recoveryofdeepre00unit

I assume that reluctance to add saddle tank volume in a personal sub is 
due to the need to trailer it home. If it exceeds maximum highway specs 
it must obtain a special movement permit every time it hits the road.

Best,
Marc



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