I've put together a rig using an aluminum backplate, harness, cam bands and AL80 tank for minimalist diving. So far I've only used it in the pool. I'm wondering if it will be necessary to make/use a crotch strap in salt water. Most of what I've read is that when you surface with a rig like this that the AL80, when low on air, has a tendency to float up unless you use one. Anyone have some experience with this type rig and any suggestions? No, I don't want to buy a $teel tank.
Minimalist rig
- Thread starter Garrobo
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That is close to what I dive. I use a vintage plastic plate instead of the AL one but otherwise pretty much the same. I weight so that I am about 2 lbs overweighted at the beginning of the dive which leaves me about 2 lbs positive at the end. I find this amount of over and underweighting no problem to deal with. In warm fresh water (no wetsuit) I use no weights and 4 lbs in salt. I can't dive steel because it will overweight me when diving minimalist unless I have a wetsuit on, which is fairly rare.....hate cold water. 
herman: I'm thinking about hanging a couple two-pounders off the bottom of the backplate to compensate for the uplift of the tank if there seems to be any problem. Can't wait to get to an ocean to try this rig out. Maybe next month.
I use a similar rig. I have a freedom plate on a 30lb Oxycheq wing. The rig fits quite snug even without a crotch strap. I have not noticed any problems with the rig wanting to float up while on the surface. In fact, I think that it is better on the surface than by Seaquest Balance.
When you get the rig setup, you might just want to add the crotch strap initially and try using it both ways. I normally use the crotch strap anyway just because it does make it a little more stable.
I am sure that body shape and other factors will play into it, so I would recommend that you just try it both ways and see what you like.
Have fun!
When you get the rig setup, you might just want to add the crotch strap initially and try using it both ways. I normally use the crotch strap anyway just because it does make it a little more stable.
I am sure that body shape and other factors will play into it, so I would recommend that you just try it both ways and see what you like.
Have fun!
Mayor
Contributor
I feel the crotch strap is a big part of the rig.
The crotch strap is a bit of a nuisance to find and get clipped in some times but it does help keep the rig in place.
I, too, feel that the crotch strap is a big part of the rig. I don't like to have tight shoulder straps, plus you have to where the rig a lot higher on your back if you want the shoulders to hold everything on, which takes away some options for trimming the rig out, etc. I feel like the CS hold everything together. I definitely would not dive doubles without a crotch strap.
I dive the setup you are describing and have close to 1000 dives in it. I do prefer a crotch strap, but not for the reason you mention. I don't find that the rig floats up when the tank is almost empty. However, when orienting yourself upside down to, for example, take a peek in a hole, the crotch strap prevents the rig from sliding downwards. Try it without the weights first.
For the few pounds I need in saltwater I just thow on a standard weight belt. I use a crotch strap when diving with a BC and prefer one if I am diving dry or need a thick wetsuit but I really don't see the need when mini diving with little exposure protection. Since there is no bladder to cause lift and you are diving mini so I am assuming you are correctly weighted so there is little to make the BP shift.
I would try it without it, you can always add it if you feel you need it. IMO it's just one more unnecessary item when diving mini.
I would not get too hung up on the bouyancy of the AL tank. Your tank, reg, BP, harness and cambands will act as a unit and in total, it's not likely they will be anywhere close to positive even with an empty tank. Frankly, I would want mine darn near neutral or maybe even slightly positive so the darn thing will not sink like a rock if I need to remove it.
Mayor
Contributor
I spent some time with an AL80 to trim out my rig for vacation. 3mm shorty, AL backplate, harness, single tank adaptor, single tank adaptor weight (6lb), and 2 pounds in two small weight pockets. Trimed out perfect with 500psi in the tank. Of course salt water I will need a little more but I have a good number to work with. All the clips and rings add up quick.
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