Advice for small doubles

[elan]

LP72s, Faber LP85s, worthingtons LP85s they are both long tanks 85s weight the same as Al80s as long as the AL80s and need 8 lb less weight. Worthingtons LP85s will work for her too, as well as HP100s,

HP100s would probably be the best bet as they are not too short for her and overall weight will be less then all the tanks above if you add the extra weight if you need it. But if you do not need the extra weight Faber LP85s can be good.

You need to play with numbers a bit. AL80s will probably be the worst of all of them, they will require extra weight which will kill the dry weight advantage over say HP100s.
AL80s are good for long people and in situations when you need to match your tanks to some "crazy" GUE divers diving the same tank factor

I dive them myself because I did not like how my HP100s trimmed but I absolutely love LP72s and my wife loves them too, she recently told me that I can only break them apart over her dead body She also has a set of OMS LP85s but likes 72s

 

[elan]

So what is Bobs and Your opinions of the HP 100's for trim? Just wondering as I am involved in another forum Ontario Divers where a GUE instructor states the HP 100's suck for trim and the aluminium 80's trim better; Which is not my experience I love the HP 100's for trim I'm 6'-0" if anything I keep a little air in my feet to keep them up without any effort.

They actually suck big time I had a set and I did not like them, I could marginally trim them - just at the edge of the comfort level. And they are very inconvenient on the land - when I was sitting on the bench the tanks did not touch the bench but were resting on my back. I'm 6' tall as well. They would probably work in the ocean if you add extra weight on the tail of on the belt but in fresh water that tank IMHO is far from being an optimal

 

[Lobzilla]

They actually suck big time I had a set and I did not like them, I could marginally trim them - just at the edge of the comfort level. And they are very inconvenient on the land - when I was sitting on the bench the tanks did not touch the bench but were resting on my back. I'm 6' tall as well. They would probably work in the ocean if you add extra weight on the tail of on the belt but in fresh water that tank IMHO is far from being an optimal

My Asahi HP100s are 26" from floor to manifold without boots. I am 6'6" and when I sit 'broomstick' straight the top of my shoulders is 26" above the seat surface. Unless your torso is very long, your tanks are probably sitting too high on your back which would also explain the trim issues.

Most people agree that AL80s are easier to trim out on tall people than HP100s. The AL80s need additional lead that one can use to get the trim adjusted.

Adding lead to steel tanks is mostly unnecessary and unwise. I was about to give up on the HP100s when I had them hanging down as far as sensible and was still head heavy. A very experienced and well respected instructor told me to stop obsessing and to be satisfied if I can dive them with 10 to 20 degrees nose-up trim.

But then it occurred to me that buoyancy distribution is still a variable to adjust trim. By simply reducing the undergarment thickness on my legs and increasing the bulk on arms and torso I could trim out the HP100s as nicely as the AL80s. I still can easily reach the valves with the added fleece sweater and this undergarment distribution also makes more sense thermally for me. I always chill first on the arms and shoulders and never on the legs.

Static trim is influenced by the location of the center of gravity with respect to the center of buoyancy. Can't move one enough - try to move the other.

(Different environment, same challenge: When they move the 'jumbos' around in an airplane you know that they reached the point where adjustment of lift distribution would not do the trick anymore by itself)

 

[elan]

The HP100s I'm refering to are Worthingtons HP100s which are 24" tall. If they were 26" they would be priceless.

Adjusting layers based on the trim brings other issues, you legs might freeze sooner than the body, in my case I already had 200 gram on the legs, you cannot go less than that... Adding boyant undergarment to introduce more buoyancy add a problem during ascends, it becomes more difficult to manage the buoyancy while changing levels...

You can manage to hold the static trim well but like in my case it could be on one side of the scale when you have used all tools. Once you add a stage which places more weight on the front d-ring you cannot compensate any more as all the tools are used and you sink down head first.

I could easily manage them with 20 degree trim, no issues but this introduces issues into the finning. When you are balanced the finning feels absolutely differently.

For me there is no such word as wise in weighting, you either need the weight or you do not, The configuration I dive is balanced with HP100s in fresh water. I need no extra weight, if I dive salt water in the same configuration I will need to add 3% of my total weight which is 300lb so I will need to add 9lb to my rig. If this weight is placed on the tail I would be fine with the trim.

I was experimenting with the tanks for more than 100 dives with a hope I can trim them but after I got a good understanding of how the whole system works I realized there is nothing I can do...

I just opted for different tanks. I mostly dive AL80s lately. I only have a V weight with weight located mostly on the center between the bands, As they are catalinas they are tail heavy which helps to counterbalance the manifold stuff.

 

[Lobzilla]

The HP100s I'm refering to are Worthingtons HP100s which are 24" tall. If they were 26" they would be priceless.

Depending on where you live, you can try my Asahis that are known to be more butt heavy. I also know a shorter guy who is in the market for Worthingtons if you want to sell them.

Adjusting layers based on the trim brings other issues, you legs might freeze sooner than the body, in my case I already had 200 gram on the legs, you cannot go less than that... Adding boyant undergarment to introduce more buoyancy add a problem during ascends, it becomes more difficult to manage the buoyancy while changing levels...

Agree. I had a 400 g/m3 coverall. Now it is 200 on the legs and 600 on the upper body. Overall buoyancy of the suit with me in it is still 20lbs, which is not excessive for winter diving in the North East.

You can manage to hold the static trim well but like in my case it could be on one side of the scale when you have used all tools. Once you add a stage which places more weight on the front d-ring you cannot compensate any more as all the tools are used and you sink down head first.

I try to be able to nose down to 10* negative without loosing it. That gives some margin for other stuff. Teetering on the edge is painful.

I could easily manage them with 20 degree trim, no issues but this introduces issues into the finning. When you are balanced the finning feels absolutely differently.

Especially the dreaded back kick is not so dreadful anymore.

For me there is no such word as wise in weighting, you either need the weight or you do not, The configuration I dive is balanced with HP100s in fresh water. I need no extra weight, if I dive salt water in the same configuration I will need to add 3% of my total weight which is 300lb so I will need to add 9lb to my rig. If this weight is placed on the tail I would be fine with the trim.

I meant the unwise choice of adding unneeded weight to get the trim right (and then paying for it with reduced buoyancy control and more risk in the event of BC failure)

I was experimenting with the tanks for more than 100 dives with a hope I can trim them but after I got a good understanding of how the whole system works I realized there is nothing I can do...

I always like if a strong opinion is backed up by equally strong logic or evidence.

I just opted for different tanks. I mostly dive AL80s lately. I only have a V weight with weight located mostly on the center between the bands, As they are catalinas they are tail heavy which helps to counterbalance the manifold stuff.

Coming back on topic, AL80s are the most versatile small doubles IMO. They are perfectly balanced on a wetsuit and the additional lead required for a drysuit or salt water is an advantage once you understand where to place it. If 154 cuft are enough for the job, they are the cat's meow.