Thinking outside the (ballast tank) box

[roedj]

Group,

Before the dynamic duo, D&M, descend upon my head in holy wrath, let me say that I really like the Sub Driver concept for safety and reliability especially after the addition of the SNORT system.

BUT... (Oh God, here it comes)...

It does have what I choose to call a design limitation. And just to be absolutely clear on this, I'm sure D&M are very much aware of this. The limitation is that the ballast adjustment is not proportional to a servo movement in the sense that one cannot fine tune the density of the submarine, on the fly, without introducing air into the ballast tank (always a risky proposition).

I'm wondering if D or M have considered some way to add a small piston/cylinder to the main ballast tank to fine tune the amount of water in a full ballast tank. I believe it wouldn't have to be much more than 10% or 15% of the main tank volume to get the desired effect.

Perhaps the Wiz has come up with an entirely different and better idea. I'm just taking a freakin' shot in the dark here.

**** on the EPA, I'm fully clothed in asbestos, go for it..

Dan

[Kazzer]

Yes, The Wiz has been pondering this for a while. We are looking for a component for this that is economical enough, then we'll easily introduce the concept.
David has beaten it into me that the ballast tank is either full or empty, so I think you're right on the money here.

[roedj]

Mike,

Wow, no beatings about the head nor shoulders. I'm impressed.
I was thinking about a 50ml or so syringe, like vets use, perhaps driven pneumatically, hydraulically or a small lead screw. Something like that.
Anyway, thanks for listening and now back to the British "U" class sub.

Dan

[Slats]

Group,

Before the dynamic duo, D&M, descend upon my head in holy wrath, let me say that I really like the Sub Driver concept for safety and reliability especially after the addition of the SNORT system.

BUT... (Oh God, here it comes)...

It does have what I choose to call a design limitation. And just to be absolutely clear on this, I'm sure D&M are very much aware of this. The limitation is that the ballast adjustment is not proportional to a servo movement in the sense that one cannot fine tune the density of the submarine, on the fly, without introducing air into the ballast tank (always a risky proposition).

I'm wondering if D or M have considered some way to add a small piston/cylinder to the main ballast tank to fine tune the amount of water in a full ballast tank. I believe it wouldn't have to be much more than 10% or 15% of the main tank volume to get the desired effect.

Perhaps the Wiz has come up with an entirely different and better idea. I'm just taking a freakin' shot in the dark here.

**** on the EPA, I'm fully clothed in asbestos, go for it..

Dan

Dan, as Mike says they are looking into it. Its the reason why I tend to still experiment with pumps systems.
David has said that he was thinking of some sort of trim tank within the main BT.

The only boat that I could atest to having good proportional ballast control that eventuated in perfect "neutral" boyancy was a sealed tank with a pump and valve. This boat actually got parked a couple of metres down in a pool and a few metres off the bottom. Left it there while I had lunch. Came back it had not moved. That system fluked that occurance. The problem I see with pumps (although I am not anti them), is that they seem so hit an miss. Different voltage states of depleting batteries say 12.8v vs 12.3v from a gel cell for example, can cause differing ballast quantities when pumping against pressure. Then its a case of if you are holding back considerable pressure - how fine the adjustment is to let out just a little ballast. You also have an issue of going deeper, the + pressure in the tank can get to a point where the corresponding external pressure almost negates it. Case in point my Alfa at the bottom of a dive pool 5m down - took almost a minute to get off the bottom. Fully blowing the tank had the ballast coming out with pressure driving it at perhaps a drop at a time. Back at around 2m the thing came up fast.

Then there is the semi-aspirated tank - the bulk of the ballast is pumped in and out in a vented condition, the last part of the ballast is pumped in under pressure. This last part of ballast gives you the means to surface beyond snort depth, but you are left with a very fine amount to proportionally adjust ballast, which is fine, but you will find that its hit and miss by how sentitive letting out some ballast is for proportional control.

Gas - with a free flood tank gives you a constant ballast volume (either full or empty). As you go deeper you will find that as you state, proportional control would be good as the boat with a full tank will eventually be negative, even if its slight positive with a full tank to begin with. Whilst with a trim tank - and I like the syringe type thinking, a key issue is where I you going to sail the boat. If you go to a dive pool regularly and like to go deep - say to the limits of the radio range, then yes it would be good. If however you spend most of your time in waters where you don't go beyond PD, then the current setup is just fine (no trim tank).

I have spent a lot of time mucking around with different systems (like a couiple of decades now), I keep going back to gas / snort as the seasoned all rounder. If you are not going that deep, you won't need a proportional control. If you go perhaps a few times a year only to waters (pools) where you can go very deep, perhaps ballast the gas boat a little more positive on the surface than ordinarily, and this might help you find or be close to neutral at lower depths.

All that said, a fine adjustment tank like the syringe / engel type would be cool.
J

[roedj]

John,

Thanks for your insights and experiences. Stuff to ponder as I'm opening all those verkachte limber holes on the "U" class sub.

Dan