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Hi Alan. I've heard of as little as 40 pounds, and another at 300 pounds.
My calculated lead ballast should be around 1800 pounds. Of that, 700 or so
will be a drop weight. two things I've considered are,
#1...keeping the weight as low as possible obviously, to keep the
center of buoyancy well above the center of gravity. Too big a drop weight and
the boat may become unstable after dropping. I've designed a grid system on
the floor of the sub which will have "pockets" for lead bricks. ( bolted down )
The drop weight will be poured into a steel container attached to the bottom of
the sub. Model testing has shown acceptable stability after the drop weight is
released.
#2.... if the weight is dropped, you need to have a spare to go and
retrieve the old one. The cheapest I've found for lead on Ebay is 76 cents per
pound. I got lucky and found a local guy who will sell me 1800 pounds for $350.
I went with a large drop weight because I may get hung up on
something and wanted to have a lot of buoyancy to break free if the need arises.
I plan on spending a lot of time in the kelp beds and they are pretty
strong if you get tangled up in them. I've tried to minimize points that
can "snag" on the sub, but it's still possible to get hooked on something. Frank
D.
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