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Hi Guys. On the ballast/trim thread........
Brian's sub is long and thin, but the pressure cabin is quite
small. He wants to be able to invert his boat, so has a large ballast system
able to overcome the buoyancy and make the cabin be at one end. The large
ballast would make it possible to lift something heavy off the bottom.
A trim system is quite different. Generally it
doesn't affect buoyancy, just dive angle, although if designed properly, the
sliding weight could be used as VBT also. It makes it pretty complicated
though because you'd want the ability to dump the water at depth, requiring a
piston pump and related plumbing, all connected to a moving tank or dual
tanks.
My first thought is.....too complicated, and prone to malfunction.
I like the idea of a VBT and will have one on my
sub. I'm leaning towards that "lite" propane tank idea. It is see through and I
should be able to see how much water is in there, making adjustment ( always
done near the surface at the beginning of the dive ) quick and easy. It
won't need that much capacity because I'll be loading lead bricks on/off
depending on how heavy my passenger is or what extra equipment I'm taking on
board for that particular dive.
For trim, I will start with seats that slide forward and
back. I can also get my passenger to move behind me if we want to get a severe
up angle. Same thing with roll, we can slide our butts across the bench seat
left and right to add banking to the turns. My dive planes/side thrusters will
also add to the roll a bit.
If I had a K boat, I think I'd make the drop weight a
sliding mechanism so trim angle could be adjusted that way. You need a drop
mechanism anyway, and adding a little slider to it shouldn't be hard.
If my sliding seats don't give me enough angle, I'll add that to my drop
weight which is shaped like a keel.
As for lifting things off the bottom, using
adjustable ballast to compensate for added weight of a retrieved object, that's
a system that is full of problems. First off, it will need to be huge, extremely
strong, and balanced. How heavy would any object be, how to compensate for just
that amount, what happens if a part of it falls off and you shoot up to the
surface, what if it's stuck in the mud and once cleared of the bottom, isn't all
that heavy, and lots of other scenarios that would make a system like that
problematic.
I would suggest using the tried and proven lift bag
option. Much simpler, and it doesn't tie the sub to an object that may or
may not be liftable. Lift bags can be attached with a manipulator arm, and
by pulling a rip cord device, inflated without having the sub connected in any
way. Pull the rip cord and get out of the way.
My point here is mainly to keep all the systems, whether
it's trim, buoyancy adjustment, or any other, as simple as possible. The more
complicated a system gets, the more chance it will malfunction. Maintenance on a
system with very few parts is always going to be easier than having a complex
device with tubes, pumps, pins, hinges, swivels, parts and pieces, all outside
the sub where you can't get at it when submerged. Not to mention the snag
potential of having all that stuff poking out from the hull.
My " Fat Shark " ( thanks Vance, I like that ) will be
as simple as I can make it, with pretty much every system and component inside
the hull where I can get at it, and it's protected from everything that happens
on the outside. Again.....SIMPLICITY is the key to safety and reduced cost, both
in building and operation.
Frank D. Great Deals on Dell Laptops. Starting at $499. |