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Hi Stratus,
Speed isn't really important in a sub. Fast in a sub
is VERY slow when compared to a surface craft. If your diving to see
things, a walking pace or slower is all you need. If your in poor
visibility water, you won't ever go very fast. Surface speeds are another
thing but you'll find that, if your battery powered, battery life is more
important then speed. As speed goes up your distance per charge goes way
down. A personal sub can be maneuvered submerged with one horsepower or
less and on the surface three horsepower is about as much as you can steer
a straight course with. If your design is long and sleek maybe a little
more power.
Just give a search for the heads. Not hard to
find.
Depending on prop size and motor speed you may be able to
direct couple or have to use a speed reducer. This can be a gear box or
belt and pulleys. Most P subs just use a smaller diameter prop and
direct couple to the motor shaft. The best shaft seals are
carbon on ceramic, spring loaded, face seals. Search for water
pump seals. You have essentially the same
application.
Your water line is determined by how much water the sub
will push out of it's way until it balances. Calculate the volume of
your hull and any external components. Calculate the weight of the same
volume of water. Calculate or weigh the weight of everything the makes up
the sub, it's dry weight on land. If your sub is lighter then the water
it's not going to dive. It should be heavier. Next calculate the
volume of your ballast tanks and how much lift they will have when
submerged. Combine this lift with your hull weight, which is actually a
subtraction, and you find how much remaining lift you have. Calculate the
displacement of small portions of your hull starting at the most top part and
subtract from your lift until your equations balances. Total weight
on land - weight of displaced water when totally submerged - lift of
empty ballast tanks = the force of the amount of buoyancy you
have. From that buoyancy keep subtracting slices off the
top of your sub until you reach a balance. If you can't grasp the concept
experiment with a corked bottle and weights in water.
Good luck, hope this helps, Dan H.
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