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Hi
all,
Ballasting a small shallow water sub
proprely requires at least three separate ballasting systems or
techniques:
1- Main Ballast System (Also called Air
Ballast)
2- Variable Ballast System (Also called
Water Ballast)
3- Fixed Ballast System
The purpose of the first is to provide the
freeboard necessary to keep the hatch above water and is the system with
the most buoyancy reserve of all. It is the largest consumer of air in the
sub.
The second is to accommodate for
differences in payload from dive to dive, the system capacity depends on the
size constraints, weight and total payload available. As a rule you never want
to run your VBT system completely full or completely empty. It should be
designed so that the system oprerates between 20% & 80% of it's range. The
rest is designated as a reserve
buoyancy.
The third is either fixed by means of lead
or syntactic foam in order to adjust for the lack or excess buoyancy. It is
normally set with a full payload and the ballast system set at 80% of it's full
capacity. It is also designed to adjust the trim of the submersible with a full
payload condition by distributing the lead throughout the length of the
submersible.
In smaller subs the total payload must be
calculated before each dive and the fixed ballast adjusted accordingly in order
to operate within the parameters established.
This is the traditional method of
ballasting subs, other subs like the Deep Flight depart from the norm and depend
on speed, rudders and elevators to
submerge.
By the way, the term sinking implies a one
way trip to the bottom. Subs submerge and ascend, not sink and float...
;o)
Hugo
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