Test Run in Pool

[toppack]

I had the Gato operational in the hot-tub so I talked my neighbor into using his pool for a test run.
Of course everyone was watching, so when I put it in, I was very embrassed when it started Listing to port about 30 degrees.
Removed cover and found the battery-pack had shifted in tube, while carrying it across the street. It did okay then, but it's still very sensitive in roll, on surface. (lists a little, maybe 5 deg) No problem when at periscope depth or deeper.
It's at the correct depth when surfaced so I can't add much more keel-weight, so I guess there's not much I can do about it except attach something inside battery compartment to keep it from shifting. And maybe add removable balancing shims, beside SD, as needed?
I'm accustomed to surface ships that are not this sensitive in roll weight balance, so
Anyone have Ideas?

[He Who Shall Not Be Named]

I had the Gato operational in the hot-tub so I talked my neighbor into using his pool for a test run.
Of course everyone was watching, so when I put it in, I was very embrassed when it started Listing to port about 30 degrees.
Removed cover and found the battery-pack had shifted in tube, while carrying it across the street. It did okay then, but it's still very sensitive in roll, on surface. (lists a little, maybe 5 deg) No problem when at periscope depth or deeper.
It's at the correct depth when surfaced so I can't add much more keel-weight, so I guess there's not much I do about it except attach something inside battery compartment to keep it from shifting. And maybe add removable balancing shims, beside SD, as needed?
I'm accustomed to surface ships that are not this senstive in roll weight balance, so
Anyone have Ideas?

You can increase the roll stability by filling the unused space you have in the near waterlines area around the cylinder (and don't neglect the forward and after spaces by the torpedo tubes) with hunks of foam, then add the amount of weight needed to neutralize the added buoyancy.

David,

[Kazzer]

AHA! The sliding battery eh?

Just watch that problem, or you'll be swimming for your boat. The battery can slide about an knock the forward endcap out, resulting in a catastrophic flooding.

My Gato went down majestically, props spinning at her stern pointed skyward. She slipped under in a mess of bubbles. Very realistic!

http://www.youtube.com/watch?v=CEskvVUHjnw

Divers cost $150!!!!!

Wedge the battery into the cylinder with a block of foam and tape the end-cap to the cylinder with electricians tape.

[toppack]

Okay I may be able to stuff in a little more foam, but it's almost full Now.

Yes, I noticed the forward bulkhead is looser than the aft. Putting on some *Duct-Tape* would be good insurance. :)

Thanks Guys

[toppack]

I added more foam and more keel-weight, then did another pool test with deck/cover off, and found that it still has same roll problem, when surfaced. :(
But this time I noticed that it was perfectly level when center-ballast-chamber had No water in it (as it was in hot-tub), but the more water it has the More it Lists (until it gets about half full, then starts leveling again). Which seems Backward than it should be. :confused:
It seems that the more water in chamber, the more keel-weight there would be, making it more stable. But No, not until it gets above half full!
As soon as I pump in more air, when surfaced, it goes back to vertical.
Very Strange? :confused:
I think that's telling me that I need more flotation-foam, close to surfaced waterline, but there's No where else to put any. :(
Or maybe Remove some foam, down close to keel? Then remove some of the extra weight I just put in?

[He Who Shall Not Be Named]

I added more foam and more keel-weight, then did another pool test with deck/cover off, and found that it still has same roll problem, when surfaced. :(
But this time I noticed that it was perfectly level when center-ballast-chamber had No water in it (as it was in hot-tub), but the more water it has the More it Lists (until it gets about half full, then starts leveling again). Which seems Backward than it should be. :confused:
It seems that the more water in chamber, the more keel-weight there would be, making it more stable. But No, not until it gets above half full!
As soon as I pump in more air, when surfaced, it goes back to vertical.
Very Strange? :confused:
I think that's telling me that I need more flotation-foam, close to surfaced waterline, but there's No where else to put any. :(
Or maybe Remove some foam, down close to keel? Then remove some of the extra weight I just put in?

You've just experienced the same phenomena that plaques real American boats (and the BALAO, GATO, and TENCH class boats in particular): free-water sloshing transversely within the ballast tank -- a condition that only occurs if the tank is partially filled with water. The boat rolls, just a bit, and the free water sloshed to that side, increasing the list till the boat stabilizes -- and it will stay there till either the water is out or the tanks or the tanks are completely full, then the boat returns up-right. It's the transition state of the ballast tank, as it takes on or get rid of water, where the boat becomes less stable about the roll axis.

That's why if a diesel boat get caught on the surface in heavy seas (even with split A and B tank sides), you have to ride it out on the surface -- to dive the boat, you risk rolling over as the tanks fill. I've spent a few miserable bridge watches on the TRUTTA, stuck on the surface in a state-4 sea because of this. Puke city!

The cure? Make your flooding and blowing of the tank as quickly as possible.

David,

[toppack]

Hey, I Was trying to build a 'Scale' model. :)
I'll just Live with it then.

Thanks for the Interesting Info David.

[toppack]

If you think about it, submarines with long slinder hulls are basicly an Unstable design, in roll. It's a wonder that they operate as well as they do.
I guess that's why most countries went with the Saddle-tank design, during the diesel boat years, since it could be more stable in roll, if no equipment failures were encountered on one side?

[Nuke Power]

Subs arent designed to run on the surface anymore. Get and dive as soon as possible. If we wanted surface stability they would build another destroyer or such.

Now whos life to I have to extinguish to get some photos or movies of your darn boat...