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Hi Brian. (" tapping on the side" ) That's definitely low tech,
but not quite as accurate as I'd like. I think that with a little practice, a
guy should be able to approximate what level is needed to achieve neutral
buoyancy. That level can then be repeated as long as other factors affecting
buoyancy remain constant. However, changes in temperature, salinity, and depth (
it's much colder at depth around here ) can require small adjustments that
only a VBT can provide. If I start out at a river mouth launch site where
there's very little salt in the water, and then motor out to the ocean, the
difference in buoyancy, although not that large, would make adjustments
necessary. This scenario is typical of where I plan to dive. Both of the local
harbors near here are situated on rivers. With a displacement of 900 gallons,
the difference in salinity/water density will make a difference. I'll need some
way to set the level in the tank about half way full, and then repeat that level
consistently on following dives with out time/energy consuming re-balancing the
boat to neutral.
I'll be carrying lead bricks on the inside for major weight changes like a
passenger or additional equipment for a specific dive, and the drop weight is
adjustable also with a little wrenching, but being able to repeat a level of
buoyancy consistently when all other factors remain constant should make
multiple dives easier and faster. I want to maximize the useful time spent
submerged without spending too much time adjusting for neutral. Did you see the
composite propane tank link Greg put up ? that looks promising.
I'm still not sure how big the tank needs to be. It's probably not that
critical, but the amount of fine adjustment needed is affected by several
variables. And then there's the amount of air it takes to change that level. If
you can set the level at the surface, it takes only a little air. If you need to
make adjustments at 300 ft. then it takes a lot more air, and then you've got a
pressurized cylinder inside the sub with water in it. That will need to be
dumped once you get back to the surface. Of course, I've never actually done any
of this before, so maybe I'm over thinking it. I'm certain there's going to be
some design changes needed after I get this thing wet. Some of them will
undoubtedly be expensive fixes. I just want to avoid dangerous mistakes.
Frank D. Wondering what's for Dinner Tonight? Get new twists on family favorites at AOL Food. |