How do you rig and use your doubles?

[WarrenZ]

If you are short the HP80s would probally work for you Im not a fan of them but I about 6'. Depending on how much weight it takes to sink you and your wetsuit the HP 80s full would be about 24-26lbs negative possibly a little more depending on plate and regs. Worst case is you have to swim all that weight back up of something failed so bad you cant use your wing for any buoyancy a rare possibility but it could happen. in that case you would have to swim up with all of that weight assuming you and your suit currently dont need any weight to get down. if it takes you 15lbs of lead now then you are only talking about swimming up with 10-15lbs of weight. I dive steels with a wetsuit no problem however as you can see in my profile pic I am a big guy and can completely hide a set of 133s behind me.

Your wing needs to be large enought o float your rig at the surface without you in it and full tanks. If it can do that it shouldnt have much problem floating you comfortably in it. I carry a 50lb lift bag for redundant lift and as a smb when diving wet.

 

[dvrdv]

If you are short the HP80s would probally work for you Im not a fan of them but I about 6'. Depending on how much weight it takes to sink you and your wetsuit the HP 80s full would be about 24-26lbs negative possibly a little more depending on plate and regs. Worst case is you have to swim all that weight back up of something failed so bad you cant use your wing for any buoyancy a rare possibility but it could happen. in that case you would have to swim up with all of that weight assuming you and your suit currently dont need any weight to get down. if it takes you 15lbs of lead now then you are only talking about swimming up with 10-15lbs of weight. I dive steels with a wetsuit no problem however as you can see in my profile pic I am a big guy and can completely hide a set of 133s behind me.

Your wing needs to be large enought o float your rig at the surface without you in it and full tanks. If it can do that it shouldnt have much problem floating you comfortably in it. I carry a 50lb lift bag for redundant lift and as a smb when diving wet.

Thanx much for the feedback! ......
24 -26lbs negative might be too much. I use a Diverite tranpac soft BP and rec exp 45lb lift wing which I believe puts me right at neutral, but also use older generation diverite led can light and hollis f1 fins which probably adds to the negative buoyancy. It sounds like a the 50lb lift bag would be areally good idea to carry if I go with this setup !! ......

 

[tbone1004]

@dvrdv you need to understand the why before you blindly follow those statements. The don't dive steels while wet is only relevant because MOST steel tanks will overweight a diver, especially doubles. Tanks like LP72's and HP80's won't necessarily overweight you.
Let's think.
AL80's are +4.4 when empty
HP80's are -2.5 ish when empty *some more, some less*
IF you are putting on a weight belt with 14-15lbs of lead in order to get you down, then you should dive the HP80's because the total rig weight will be 3*2lbs lighter for the actual tanks, and 7*2lbs lighter for the buoyancy characteristics=~20lbs lighter weight. If you're short, it will also be 6" shorter. AL80's are really only appropriate for divers 5'10" ish and taller because they're actually pretty long tanks. You have the same amount of air so the buoyancy shift is no different for AL80's vs HP80's, so there is no reason to dive AL80's if you are better served by the HP80's. Now, if you need 14-15lbs of lead on top of the bands/manifold/regulators, then you are either very overweighted, have lots of bioprene, or are diving a very thick wetsuit. I don't think double 7mm farmer johns are safe, and that is about the only wetsuit I can think of that would cause you to have to add that much lead onto a set of doubles.
If you only need say 10lbs to get down, then you are going to be overweighted using the HP80's, and going to something less negative like a HP100 is a better choice. There is only an extra 3.2lbs of buoyancy shift, but it is about the same amount less negative. Total rig weight will be a bit heavier, but you get an extra 25% gas bump which is nice and the rig is less negative.

I have no problems with divers in a balanced rig using HP100's and a 5mm and do it myself regularly.

 

[dvrdv]

@dvrdv you need to understand the why before you blindly follow those statements. The don't dive steels while wet is only relevant because MOST steel tanks will overweight a diver, especially doubles. Tanks like LP72's and HP80's won't necessarily overweight you.
Let's think.
AL80's are +4.4 when empty
HP80's are -2.5 ish when empty *some more, some less*
IF you are putting on a weight belt with 14-15lbs of lead in order to get you down, then you should dive the HP80's because the total rig weight will be 3*2lbs lighter for the actual tanks, and 7*2lbs lighter for the buoyancy characteristics=~20lbs lighter weight. If you're short, it will also be 6" shorter. AL80's are really only appropriate for divers 5'10" ish and taller because they're actually pretty long tanks. You have the same amount of air so the buoyancy shift is no different for AL80's vs HP80's, so there is no reason to dive AL80's if you are better served by the HP80's. Now, if you need 14-15lbs of lead on top of the bands/manifold/regulators, then you are either very overweighted, have lots of bioprene, or are diving a very thick wetsuit. I don't think double 7mm farmer johns are safe, and that is about the only wetsuit I can think of that would cause you to have to add that much lead onto a set of doubles.
If you only need say 10lbs to get down, then you are going to be overweighted using the HP80's, and going to something less negative like a HP100 is a better choice. There is only an extra 3.2lbs of buoyancy shift, but it is about the same amount less negative. Total rig weight will be a bit heavier, but you get an extra 25% gas bump which is nice and the rig is less negative.

I have no problems with divers in a balanced rig using HP100's and a 5mm and do it myself regularly.

That makes a lot of sense tbone thanx for taking the time to reply.....right now im mainly diving freshwater about 60degrees temp. I use 5mil wetsuit w/3mil hooded vest thin gloves and 5mil booties and I stay warm no problem. Right now Im using the HP80 single DIR config, a wing for singles, a slung 30cf aluminum bailout bottle, a LED can light, heavy fins and back up lights. With that rig I only need 4-6lbs of lead on my waist and my trim and buoyancy is near perfect. In your opinion, would the transition to double HP80 be manageable??

 

[tbone1004]

to double 80's you'll probably be a few pounds heavy, but maybe not depending on if your weighting is with or without the al30. If it's without then you'll be heavy, if it's with then you'll be about right with no lead

 

[dvrdv]

to double 80's you'll probably be a few pounds heavy, but maybe not depending on if your weighting is with or without the al30. If it's without then you'll be heavy, if it's with then you'll be about right with no lead

There's gonna be way more ocean dives in my very near future and one of my main reasons for switching to a double set is to ditch the bailout bottle. Would the more buoyant fsw offset any overweighting I may incur with double hp80 and no 30cf pony? I guess what I mean is if im diving saltwater with the doubles and no pony would I still be over weighted?

 

[tbone1004]

it is unlikely you would be overweighted in the salty stuff. In fresh you might be over by 3-5lbs, not a huge deal, and to me certainly not worth the 20lb weight penalty and the 6" height penalty of AL80's

 

[dvrdv]

it is unlikely you would be overweighted in the salty stuff. In fresh you might be over by 3-5lbs, not a huge deal, and to me certainly not worth the 20lb weight penalty and the 6" height penalty of AL80's

Nice!! .....
Thanx so much tbone I appreciate you taking the time to help me out....
Im thinkin my next move is to assemble the doubles and hopefully get to some confined or shallow water and try out some different scenarios ......

 

[RyanT]

Wow, a few hours off SB and I missed so much! tbone and others actually provided a lot of good info already. I can dive my double HP 80s in my 8 mil Neotek wetsuit, saltwater, with an aluminum backplate (2 lbs) and I'm about perfectly weighted. I also dive this same rig in warm water in my shorty 5 mil wetsuit and I'm a little heavy, but it is easily manageable. My wing is a 45 lb and it provides plenty of lift for this rig, even in my shorty. At the start of the dive, if I had a wing failure, I'd be on the heavy side and it would be difficult to kick the rig up. Towards the end of my dive when the tanks get a little lighter, I could kick the whole rig up. Also, I carry an SMB with about 25 lbs of lift. I can also shoot that bag to the surface and have a buoyant line that I could also use as an assist to the surface.

I'm 5'10" and I absolutely love the length of my short 80's on my back in the water. The whole rig is just tight, compact and works for me. The downside is that the short tanks make getting into them a little harder on the boat. When I get into my harness, I have to bend back and sit with my back bent while the tank bottoms rest on the bench. Alternatively, I can sit upright, but that requires a lot of effort to support the tanks which no longer rest on the bench. Both options are really uncomfortable. The solution I found (thanks instructor) is that I now bring a block of wood (two sections of 2x6s screwed together) that I slide under the tanks just before I'm ready to get into the harness. This elevates the tanks enough that I can get into my harness and sit upright comfortably while the base of the tanks rest on the block. I find this especially useful since you often have to suit up and then sit and listen to the dive briefing before splashing.

If anyone is interested, I can upload a picture of this.

 

[dvrdv]

Wow, a few hours off SB and I missed so much! tbone and others actually provided a lot of good info already. I can dive my double HP 80s in my 8 mil Neotek wetsuit, saltwater, with an aluminum backplate (2 lbs) and I'm about perfectly weighted. I also dive this same rig in warm water in my shorty 5 mil wetsuit and I'm a little heavy, but it is easily manageable. My wing is a 45 lb and it provides plenty of lift for this rig, even in my shorty. At the start of the dive, if I had a wing failure, I'd be on the heavy side and it would be difficult to kick the rig up. Towards the end of my dive when the tanks get a little lighter, I could kick the whole rig up. Also, I carry an SMB with about 25 lbs of lift. I can also shoot that bag to the surface and have a buoyant line that I could also use as an assist to the surface.

I'm 5'10" and I absolutely love the length of my short 80's on my back in the water. The whole rig is just tight, compact and works for me. The downside is that the short tanks make getting into them a little harder on the boat. When I get into my harness, I have to bend back and sit with my back bent while the tank bottoms rest on the bench. Alternatively, I can sit upright, but that requires a lot of effort to support the tanks which no longer rest on the bench. Both options are really uncomfortable. The solution I found (thanks instructor) is that I now bring a block of wood (two sections of 2x6s screwed together) that I slide under the tanks just before I'm ready to get into the harness. This elevates the tanks enough that I can get into my harness and sit upright comfortably while the base of the tanks rest on the block. I find this especially useful since you often have to suit up and then sit and listen to the dive briefing before splashing.

If anyone is interested, I can upload a picture of this.

Thanx RyanT for the input...... it really helps to get the perspective of one who dives this setup regularly . Likewise, everyone's input has been great.
I like how you overcame and adapted to the "length" dilemma. Great solution it gives me some ideas..... It seems that in all the different exposure suit, environments, and weighting scenarios I will put myself through the double HP80's maybe just slightly over weighted diving wet, however, from the input you gave I think this could be an ideal set up for me.
I am definitely interested in photos pertaining to this and thanx again for taking the time to help me out ..........