Trim tanks with pump and solenoid

[spankey]

I was exploring an idea for trim tanks (fore and aft) to ensure that our boats maintained level as they were diving and surfacing.

Many of the boats out there running gas systems (but probably also piston ballasted boats) seem to experience a severe "bow-down" trim as they submerge, and the same extreme "bow-up" trim as they surface. I realize this is usually a ballast tank that is slightly forward in the sub, combined with the free surface effect of the water sloshing in the ballast tank.

Has anyone considered or experimented with two trim tanks, one in the bow, and one in the stern, where pump and solenoid operate together to move water forward and aft between the two tanks? Pumping water in either direction, and closing the solenoid valve would trap the water in either tank. The air pressure that increased as water was pumped into either of the tanks would also assist in returning the system to an equal trim state (equal water in fore and aft tanks) when the pump is reversed, and the solenoid is opened.

Yes, Yes, I know... it's complicated, but I wanted to couple it with one of the (ADC) level keeping devices that we use for the bow or stern planes.

Intended use is on a couple of my larger American nuke boats that are sometimes victims of free surface effects in their ballast tanks.

Plus, it's just for my own grins and giggles to make it work.

Any thoughts?

[spankey]

I should also add, that this is a closed system, and does not have any connection to the water that the sub is driving in. This ballast water would just remain in these tanks.

[He Who Shall Not Be Named]

Keep it simple: Just install baffles in the tank(s).

David

[RCSubGuy]

Sub pitch change during diving is not a result of ballast but rather your planes pulling the boat under. If your bow planes pull the bow downward, the boat will change pitch until stern planes compensate.

what you’re talking about will work, but I bet it will be too slow to track fast pitch changes.

Give it a try! Prove me wrong.

Bob

[Monahan Steam Models]

What Bob has pointed out is absolutely spot on.

I use a similar forward and aft trim tank set up on a recent WTC experiment, although the trimming for surface and submerged settings are carried out and set with the boat statically and the trim set points are stored for either condition.

Bob brings up a great point. The amount of ballast trim differences is very slight and slow to react. I wrote software with a PID algorithm and some other bits of code to add stability to the ballast adjustments while trimming.

Nick