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Hi Dean. This is Frank. Although I'm not an expert ( still building my
first one ) I have a few thoughts about your questions.
Ballast tanks make you ''come up'', and adding more capacity puts your
hatch higher out of the water. The drawbacks are, the larger the tanks, the more
air it takes to fill them, so increasing the size means you must increase
available high pressure air or settle for fewer ''tank blows''
An extra scuba tank or two doesn't take up that much room, so I'm going
with that.
The shape and location are very important. In the case of a ''K'' boat,
you'd probably make them longer to add the extra capacity. Most of the guys put
a bottom on the tank to keep the air inside during a roll or pitch.
It's important to keep the tanks as high as possible so your ''center of
buoyancy'' stays high, while your ''center of gravity'' stays low.
The shape of the tanks affects the speed and stability of the boat. George
planned the shape and location very well. The air exits the tanks at the high
point, next to the hull.
The one thing I don't like about the design is that the tanks are welded to
the hull, making it difficult to grind and paint in the corners where the two
meet.
I have opted for a bolt-on set of tanks so I can remove them, re-paint the
hull, and bolt them back on.
I'm using fiberglass fairings to smooth out the shape.
I think metal tanks are safer, in case you hit something. A fiberglass
tank could crack or break if you impact hard enough, where a metal tank will
probably just dent.
Take a look at my frappr pictures
and you'll see how much larger my tanks are relative to hull size. I hope
to get the top hatch out of the water about 28 inches. I built test
models with the tanks and stability is good. Steel is lighter in water than in
air, so once you have the steel at the surface, it takes a lot of displacement
to raise it out of the water. With the ''K'' boats,you only need to get the
tower above the surface.
I'm going to need a splash guard to keep waves from washing into the sub
when the hatch is open. I'm working on an inflatable design for that. (not done
yet, but getting close)
Got any new pictures? Love to see them. Frank D.
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