Sizing Ballast Tanks

[rparwira]

Ahoy,
Our senior design project is to design a highly maneuverable RC controlled submarine that will be able to pick up a payload at 15 ft deep.
I'm having trouble in trying to determine the size of the ballast tank required and how it will perform. Does anybody have any scientific (or not) method in calculating this?
If possible we'd also like to have our submarine be capable of attaining neutral buoyancy at certain depths.

Thanks,

Ryan

[aeroengineer1]

A great book that you

A great book that you might consider in purchasing for you team is called "Concepts In Submarine Design" I forget who wrote it, but it was done by 2 authors from I think Cambridge. It has information on almost everything from balast tank sizing to maneuverability. At any rate, due to the fact that your boat will not be traveling to any great deapths or throught many changes in water cosistancey while maneuvering, you will be able to design a balast tank which will allow for neutral byouancy. Than being said, that will not allow you to necessarily hover. Remember that you can have all forces ecual and there will be no acceleration, but there can be velocity. To make a boat hover, I would recommend some type of piston tank setup with some facny electronics. There are a few options that are out there that will allow for a hovering capability.

Adam

[Guest]

An easy empirical method I

An easy empirical method I picked up from Skip Asay- make your boat and watertight compartment (be it cylinder, box etc.) add equipment batteries etc. Chances are it'll be too light, add weight until the boat is only just bouyant, now add a small bit more weight until she just goes under.

Now cut up some polystyrene foam, and attach it to the hull (beneath the waterline) until the boat reaches the desired freeboard.

Measure your blocks, this will give you the volume of the tank(s) you require to statically dive your model.

Add 10-15% for safety factor.

If you are interested in the piston tank system, and a ready made version, then take a look at the Engel website.

There you will find piston tanks and control boards for this system.

May I also suggest the purchase of an excellent book called 'Model Submarine Technology'.

This covers all the fundamentals of model submarine design, and includes some electronic circuits (some of which work well, others don't).

The book is available from Traplet.

Andy