Learning doubles w/ Twin HP 120s?

[bikefox]

Thanks everyone for the responses so far. A couple of more questions.

All of the bands I find are either 7.25" or 8". Since mine are 7.29" is this a problem? Will I have to special order bands?

Also I have Genesis valves on the tanks. Do I need to buy a complete manifold or can I just by the isolation crossbar?

Thanks

 

[dannobee]

If I'm not mistaken, the Sherwood 120's are made by Asahi and are very negative and bottom heavy because of their spun construction. Double them up and you'll likely have trim problems and need a LOT of lift.

Look at the tank neck to see if they are in fact Asahi's. If they are, I certainly would not be doubling them up.

 

[Scared Silly]

Most cylinders have a slight variance. You will want 7.25" bands. I will venture a guess that you have two std right hand valves so you will need to buy a complete manifold. As these are PST you will want a 7/8" manifold.

Also what are the buoyancy characteristics? Some cylinders are really really negative and really should not be doubled up.

 

[bikefox]

If I'm not mistaken, the Sherwood 120's are made by Asahi and are very negative and bottom heavy because of their spun construction. Double them up and you'll likely have trim problems and need a LOT of lift.

Look at the tank neck to see if they are in fact Asahi's. If they are, I certainly would not be doubling them up.

They are Ashai.

Most cylinders have a slight variance. You will want 7.25" bands. I will venture a guess that you have two std right hand valves so you will need to buy a complete manifold. As these are PST you will want a 7/8" manifold.

Also what are the buoyancy characteristics? Some cylinders are really really negative and really should not be doubled up.

-12.8 full
-4.6 empty

It's starting to sound like maybe I need to borrow or rent some doubles for now. Still learning alot about all of this. Thanks and keep it coming.

 

[Scared Silly]

I would not double these up for open water diving.

Cylinders 2 x -12.8
Bands & Manifold -5
Al Backplate -3
Regs 2 x -2

So right there you are -35 when full.


For comparison I dive LP85s which are around -5 when full.

Cylinders 2 x -5
Bands & Manifold -5
SS Backplate -5
Regs 2 x -2

-24 when full

When in my dry suit I need around 15lbs of blast. So that means I have an extra -10 to deal with. When in my full kit it is a bit more but still manageable if I had a either wing failure and had to use my dry suit or a dry suit flood and to fully rely on my wing.

 

[Bismark]

I'm going to disagree and say 120s are not the right tanks. They are too big for most ocean diving and most cave divers prefer other tanks. Back in the day, they were also frowned on by the Tech 1 crowd so you may have an issue there if you go that route.

I don't think you read the second post by the OP where he said he can't afford anything else at this point. The question of whether these were the best tanks was not asked, hence our replies.

 

[Bismark]

If you can't find any to borrow, the cheapest alternative is to double up a set of AL 80's, then get an 11 pound v-weight and you will need a few pounds on your belt. The tanks are cheap, keep the original valves when you get your manifold and you can use them for stage bottles down the road. They trim out nice and have an adequate amount of gas for just about any dives you will want to do at this point. Make sure to get a HP manifold when you get your manifold and then later on you can use the same manifold and 7 1/4" bands to put a set of HP 100's together........ Large volume steel tanks are great when you need the gas volume but bigger is not always better. When you are doing training dives, etc., you will love carrying the al 80's around. Unless we are doing bigger dives, we have pretty much adopted AL 80's to use for fun dives because of this. My back thanks me, and so will yours..........

 

[scuubaadoo]

I am 6'1" 205 lbs and I have 2 of the original Sherwood 120's as singles and 2 sets of Asahi 120's doubled up and I love them. I tried a set of OMS/Faber LP95's and thought they were too heavy and too bulky. I do not have any experience with the LP 85's but I have been so happy with my 120's so I don't see a need to change. Good luck the Asahi's hold up very well and the only complaint is that the neck is the non-standard thinner thread so you have fewer option in buying manifolds.

 

[MaxBottomtime]

I had a set of LP120s that were great for deep diving. My kit weighed 125# with them, but I only used them on a few beach dives. I strongly recommend getting an isolation manifold and backplate with at least 50# lift. I tore up a "tech" BC using the water heaters. I had no trouble handling them in the water.
BTW, I'm 6'4" 220 lbs and my buddy tells everyone that I'm freaklishly strong.

 

[DeepSeaExplorer]

I don't think you read the second post by the OP where he said he can't afford anything else at this point. The question of whether these were the best tanks was not asked, hence our replies.

Understood... I'm just not sure investing money in the wrong tanks is his best use of available funds. Tech diving is not an inexpensive hobby. If one can't afford the proper gear, then one should limit their diving to what is appropriate for the gear they have.