Model Forum / Radio Controlled / Water Models / September 2003

I've never seen that kind of submarine, but I'll take a guess at how it works.

Basically, you want to displace the water out of the submarine to make it
lighter. To do this, you need to pump air into the balloon, to inflate it,
driving the air out. If you had another balloon filled with air, one would
deflate and the other would inflate, ending up with no net gain in buoyancy.
But with a solid bottle, the air from inside the bottle can be pumped into the
balloon to inflate it, without the bottle collapsing from the partial vacuum.

For safety, you probably want to start out with the balloon inflated enough to
cause the sub to float to the surface, and maybe a little more than that.
Then, when you turn on the compressor, you pump the air into the bottle,
pressurizing the bottle but deflating the balloon. With less volume of air in
the sub, it will sink. When you reverse the compressor (or maybe just turn it
off), the pressurized air in the bottle will fill the balloon, driving out the
water and letting the sub rise to the surface again.

You need to trim the sub with weights so it just barely floats on an even keel
when the balloon is inflated. Then when it is deflated, the bow will angle
down, causing it to dive. You may have to keep the motor running and use
diving planes (if the sub has them), to get the stern under, and keep it
running on an even keel underwater, as with the flotation in the bow, the
stern will try to rise during diving.

Does anyone else have a better idea on how this would work?

Jerry

Sounds like you have an old Darnell sub.
The bottle in the bow is probably made from fibreglass. The process is
start the sub in the water with the rubber bladder inflated( take one
hose off the compressor that leads to the bladder and blow )Start the
compresor sucking air out of the bladder and that is then pumped into
the bottle and stored.Now you dive.Reverse the compressor and it sucks
from the bottle  back into the bladder and you rise ! Voilla !!A
dynamic sub is one that ONLY uses forward speed and correct ballasting
to dive on the motors. Stop the motors and you rise again
Subs1