The way the tanks ride

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TSandM

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I was just watching some video from some folks who were just in Mexico (Here and HERE). Their Al80's are doing what my experience says Al80s do, which is riding butt-high.

But I've watched a bunch of Steve Bogaerts' video and his tanks don't do that. Are there some sidemount setups that control the bottom of the tank, and prevent it from riding up like that? (I ask as someone who is almost completely sidemount naive.)
 
You have two sets of d-rings. One set closer to the front. When the tanks switch their buoyancy characteristics, you clip them to the set in front (assuming you're using a Razor-like system). The low profile d-rings work the best (available from Dive Rite). You could also put weights on your tank bands. Here's a link to a video of me sidemounting with a similar system.
YouTube - Sidemount Diving
 
My Catalina rides almost horizontal until it has less than 2000 psi, only after that the but starts coming slowly. Luxfer however does that much much earlier
 
. Are there some sidemount setups that control the bottom of the tank, and prevent it from riding up like that?

Absolutely. The common method now is to use a butt plate where people attach the lower end of the tank with a leash. Unfortunately when the tanks become bouyant,they will float away from the butt plate. A preference that existed before commercial sidemount harnesses,and what I use, is a rigid attachment at the hip region,and the tank has a carrabiner. Both these connect with minimal excursion which eliminates tanks floating up or away. If you are stuck in a sidemount passage it prevents having to feel behind you to unlock a tank,which may be impossible at that point,and allows you to reach down the side of your body to do the same.
 
When Al tanks get emptied, they tend to float with the butt upwards (I guess it is because of the regulator and valve on the tank's neck).

I usually add 2 pounds on the cam band, which is closer to the butt. It helps, then you can also switch them to D-rings on the waist, which forces the butt also a little more downwards.

You should also try to make the carabiner/dog clip as short as possible, and use low profile d-rings as suggested- it will minimize the tank's "slack" distance. However, it will be a little more difficult to attach the tanks IMHO.
 
Steve posted some video (I can't remember which forum) a while back and I noticed his bottles were clipped to his hip D rings. I commented in the form of a question. Steve verified that this is how he attaches al bottles. Last summer I set up a pair of al80's. I did the same and they rode great all the way down to 500 psi.
 
I remember reading one of Steve's post a while back. I believe he actually has several D-rings on his harness and moves the clip forward as his cylinders get lower in pressure. This is how he keeps the cylinders horizontal. IMO it doesn't work as well as putting some weights on your tanks. I remember seeing a video by Steve on a wreck in which the bottoms of the cylinders were riding high at the beginning of the video (the end of the dive was edited into the beginning of the video). I think it was in that thread he mentioned his technique. I put weights on my ALs when I sidemount them and it keeps them lined up just like when I'm diving steels.
 
I use Drings on the waist strap of my Nomad for situations when I'm using tanks that will start riding butt light - keeps things more managable for sure.

I do like the doorhandles for heavier steels though.
 
You can keep AL80's a bit straighter by clipping them to the towel bars when they are heavy, then clipping them to a waist D-ring when they start to float.

Alternatively or in addition, you can control them to a great extent with cam band placement to take advantage of leverage, the CG/CB, and the moment arm to control the buoyancy of the tank. A short clip helps, but what matters is the forces acting on the tank (bouyancy in the tail when it is light, the weight of the reg on the tank and the pressure and vector exerted by the bungee. For example, if the band and clip are placed so that tension from the bungee pulls the tank forward slightly and takes any slack out of the sytem, the tank will tend to ride in a more level attitude when light in the tail.
 
Great video gearhound!

You have two sets of d-rings. One set closer to the front. When the tanks switch their buoyancy characteristics, you clip them to the set in front (assuming you're using a Razor-like system). The low profile d-rings work the best (available from Dive Rite). You could also put weights on your tank bands. Here's a link to a video of me sidemounting with a similar system.
YouTube - Sidemount Diving
 
https://www.shearwater.com/products/perdix-ai/

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