Re: Regulating air supply

[Ben Trumble <trumble@well.com>]

>In a message dated 8/15/98 8:24:42 PM Eastern Daylight Time,
>nemotoad@iname.com writes:
>
><< I like some advice on methods of increasing and fine-tuning bouyancy (above
>and beyond my ballast tanks and lead weights) using air.  And I especially
>need advice on regulating the breathable air in the sub -- how to discharge
>CO2 -- how to introduce air other than using a SCUBA mouthpiece? >>
>
>These are good questions, and I'd love to hear some answers...
>
>My take on the CO2 is that you have three choices... either absorb it, in
>which case you still need an O2 supply.  This may not be ideal for a semi-dry
>sub because some absorbants are dangerous when wet, and the control systems
>are tricky...  Or flush the cabin with a steady flow of fresh air (which the
>SportSub uses), or breathe off a Scuba mouthpiece.  In my case, I will
>probably use the latter unless there are better ways which are as effective
>and as simple but that I don't know about (yet).
>
>Buoyancy control is something that I'd love to hear some discussion about
>too...
>
>Stan

When I built my semi-dry sub, modifying some old plans from Popular
Mechanics I never did come up with a good solution to bouyancy.  All of the
old designs used primitive variable bouyancy valves -- basically just a 6"
piece of 1/2" pipe with elbow and a fitting piercing the hull.  When the
pipe was pointed down in theory you had maximum positive bouyancy, straight
up, maximum negative bouyancy...but obviously this only works if you
manually introduce air to increase bouyancy via the purge valve on an air
tank.  I found that maintaining neutral bouyancy was almost a full time job
unless I wanted to be up to my neck in water.
  Using a regulator, even something lightweight like an octopus subtracts
from the pleasure we should get from a semi-dry sub.  I wonder how the
SportSub steady flow works?

Ben




"I never met a rattlesnake I didn't like."