USD Tank Size

[stephenws]

I just bought two USD tanks, 6.9 diameter, 1800 psi, about 23.5" tall. I believe they are about 50 cu ft in volume. Can anyone verify or correct me?

Thanks,
Steve

[kworkman]

I have a set of 38s that are 1800 psi and my 50s are 2250psi. Do they have real round bottoms?

[stephenws]

No, not real rounded. Bottom shape seems to be the same as my USD 2250psi 72s - a short, quick taper to an almost flat bottom.

I found a post, a few pages back that led me to believe they may be about 50 cu.ft. The serial number begins with a K, if that means anything.

Thanks for your response.

-Steve

[kworkman]

Well ive got nothing else useful. I guess I can look through the catalogs. Are they painted?

[fishnbeer]

Steve-
It sounds like you have a set of USD 52.8 cu ft tanks. I have a twin set of the same and they are 52.8 at 1800psi +10% (1980psi)each. At 1800 psi they are only 48 cu ft. Mine have original dates from 1971 & 72 & are the same dimensions as yours. A friend of mine told me that they are approx. 2.5 lbs heavy when full in sea water, and approx. 4.5 lbs. buoyant when down to about 260 psi. I have had mine for a while but have yet to dive them. If you search a USD catalog from around 1969 or so you will see them described.

[kworkman]

That sounds right. Looks like they show up as early as the '64 catalog and up until 70 they had that interior lining

[stephenws]

Thank you both for your replies.
I'll be putting them together as a doubles set, but not real happy with the buoyancy characteristics. That will be a lot of positive buoyancy with two tanks.

- Steve

[fishnbeer]

The reason they have positive buoyancy is that they are thinner walled tanks compared to 72's. I plan on putting a 5 lb weight attached between my set to counteract the buoyancy at the end of the dive. Steve BTW they weigh about 56 lbs (twins)when full of air. Much lighter than a set of 72's.

Jerry

[stephenws]

Sounds good. The weight savings will be much appreciated - I'm not getting any younger.

Good advice about adding 5lbs. I'll do the same.

Thanks Jerry