www.Robse.dk - SSBN737, R/C Submarine

Main ballast tank (MBT):

This is my home-made MBT. Those of you that has been along for a while might remember two MBT's. The idea with two independent tanks was scrapped, and this new single MBT was constructed instead. It was folded in a sheet of aluminum, and fits the inside diameter of the hull.

The raw alu sheet.
It was shaped mostly by hand,
and glued together with epoxy.

Shaped to match inner hull diam. The square hole is for the weight bars in the very keel of the sub.

This is a view inside prior to the spray
with car underbody coating, which-
should prevent corrotion for SURE.

Here the MBT has been fitted,
and hoses connected.
The masking tape is for trimming..

This is a closer look of the fitted MBT.
Note that the epoxy closes the hole
for the weight bars in the keel.

The inside volume of the tank has been divided up by bulkheads to prevent water from floating back and forth, thus rapidly moving the center of gravity. The very top of these bulkheads has been cut, allowing air to distribute to all inner compartments. At the very bottom of these bulkheads, holes around the bottom-placed weight bars in the sub allow water to flow slowly from compartment to compartment.
This tank will be able to lift the missile deck and the sail out of the water, and then some.. This leaves room for alterations later on, while keeping the perfect surfaced waterline. I could not place the tank right at the middle of the center of gravity, so I will move the center of gravity aft using ballast (lead) I have to put some additional weight in anyway, so it is not a problem.

Mechanical Data, MBT:
Length:	Weight:	Displacement:	Volume:
21 cm / 8 ,2"	0,458 kg / 1 lb	3,3 kg / 7,27 lb	3300ml. / 0,79 gal.

MBT, compartment connections:

There are two hose connections on the flat top of the MBT. Both these hoses goes to the valve compartment, WTC2. In the bottom of the tank there is a series of holes, always open to the sea. These are the drain ports.
By this, diving and surfacing is controlled alone by the top mounted hoses, and the two dive valves and vent ports. (Two hoses, two valves and two vent ports, ensures faster diving than a single hose / valve system would. ) They let the air out when diving, and keep shut when not.
Said in other words, the sub 'hangs' in these two valves. This is much like a real sub, which is also why I dropped the ballast pump in this new system.

Read more about the compartment function here: Dive System & Ballast Tank.