Teach me warm weather weighting

[Paul S]

Hi all,

So I've got a little trip planned . A long weekend down to Cyprus to spend a few dives diving the Zenobia (Zenobia Shipwreck Diving Larnaca Cyprus). I did 6 dives on it last year on a back-mounted single steel 15l (HP120) + little 3l backup (20cuft or so), and it's a cracking dive. The top is around 15m (50ft) and the sea bed is around 42m (140ft).

Definitely recommend it if you're ever in the area.

This year I'm going back and I've arranged to have two Ali80's waiting for me so I can spend a bit longer, have some redundancy and go side-mount. Should be great.

Thing is, I've only ever dived side-mount in the UK, where I'm either in a Dry-suit or thick neoprene wet-suit, and using my 12l (HP100) or 7l (Guess that'd be about an HP55). Obviously my weighting and trim is going to be very different. It's going to be more like what I read people are doing on here.

So.... In my thin wet-suit I have about neutral buoyancy with no lead on. My understanding is that Ali80's are about neutral when full (maybe a bit nose heavy with regs & valve), and go floaty when empty. I don't really have any experience with them. How much lead do people have on to cope with them going floaty?

Doing the calcs I reckon there's about 6 lbs of gas in each cylinder. So I'd be wearing about 12lbs? Does that sound about right? or is that over the top?

Would you put the weight on the tanks or on me?

Anything else I need to think about?

---------- Post Merged at 10:14 AM ---------- Previous Post was at 10:04 AM ----------

BTW: I hadn't actually looked at the video on that site. It just came up in Google with lots of good pics on it.

Not quite sure why the camera is filming that guys butt more than the wreck.

 

[Easy Divers Cyprus]

Hi all,

So I've got a little trip planned . A long weekend down to Cyprus to spend a few dives diving the Zenobia (Zenobia Shipwreck Diving Larnaca Cyprus). I did 6 dives on it last year on a back-mounted single steel 15l (HP120) + little 3l backup (20cuft or so), and it's a cracking dive. The top is around 15m (50ft) and the sea bed is around 42m (140ft).

Definitely recommend it if you're ever in the area.

This year I'm going back and I've arranged to have two Ali80's waiting for me so I can spend a bit longer, have some redundancy and go side-mount. Should be great.

Thing is, I've only ever dived side-mount in the UK, where I'm either in a Dry-suit or thick neoprene wet-suit, and using my 12l (HP100) or 7l (Guess that'd be about an HP55). Obviously my weighting and trim is going to be very different. It's going to be more like what I read people are doing on here.

So.... In my thin wet-suit I have about neutral buoyancy with no lead on. My understanding is that Ali80's are about neutral when full (maybe a bit nose heavy with regs & valve), and go floaty when empty. I don't really have any experience with them. How much lead do people have on to cope with them going floaty?

Doing the calcs I reckon there's about 6 lbs of gas in each cylinder. So I'd be wearing about 12lbs? Does that sound about right? or is that over the top?

Would you put the weight on the tanks or on me?

Anything else I need to think about?

---------- Post Merged at 10:14 AM ---------- Previous Post was at 10:04 AM ----------

BTW: I hadn't actually looked at the video on that site. It just came up in Google with lots of good pics on it.

Not quite sure why the camera is filming that guys butt more than the wreck.

Hi Paul,

I you are planning a trip soon. drop me an email: dive@ezdivers.com i will arrange all your sidemount dives. you can had a dip locally and then we can have a great dive on the Zenobia Wreck too.



ps. The video was filmed by a diver at the back of the group.

Happy Diving

Regards Joey

 

[Paul S]

thanks Joey, but I'm already booked for this trip. Will keep you in mind for next time though.

 

[Easy Divers Cyprus]

thanks Joey, but I'm already booked for this trip. Will keep you in mind for next time though.

No worries Paul. See you next time round!:cool2:

 

[eternaljonah]

Hi Paul
I have no experience side mount diving, Yet but i do dive a lot with al80's and they are a little negative in the beginning and about 1.5-2 kg positive when at 40-50 bar( thats with luxfer tanks others may wary.), and yes they are light at the bottom at the end, i have read that sidemount divers sometimes add 2kg on the end of each tank, but have no experience with that. enjoy your dive

 

[JamesK]

12 pounds seems over the top to me. When I am in warm water in my thin wetsuit I am neutral. With full tanks of course I am negative. I need two pounds total in double AL80's in that setup to stay neutral with 500psi in the tanks. I do not use any air in my wing at depths to 100 feet. I am not one who believes in weighting the cylinders. I prefer the weight to be on me. Empty tanks may be positively buoyant, but you also have to consider the regs on those tanks. That is some of your total weight as well. You are not trying to weight yourself to make up for the gas loss when you are neutral to begin with without tanks. You just want to offset the positive buoyancy of the tanks when at minimum pressure including your regulators. For me that was two pounds when in salt water.

Of course this I just all my opinion based on my experience. I am sure someone here will come in and tell me my math is wrong and even though I have over 100 dives in AL80 side mount warm salt water that their is no way it can be correct.

 

[Paul S]

... but i do dive a lot with al80's and they are a little negative in the beginning and about 1.5-2 kg positive when at 40-50 bar( thats with luxfer tanks others may wary.)

Is that per tank?

12 pounds seems over the top to me....Empty tanks may be positively buoyant, but you also have to consider the regs on those tanks

OK, sounds like my initial assumption of them being neutral was causing me to go heavy.

That makes more sense now. The couple of sites I found that had buoyancy numbers on for Ali80s didn't seem to add up to neutral tanks. More like 3-4lbs negative once rigged which would tally with your 2lbs lead.

I already got the 'gotta count the reg' point, but when people say 'I like 80s because their neutral' you don't know all the details. Even when shops quote numbers they often don't say.

I'm never going to be spot on on the first dive, but at least I'll be a bit closer now.

 

[eternaljonah]

Is that per tank?

yes

 

[Mr.X]

With AL 80 Luxfer I tend to go with 3-4 lbs of lead. Same with Catalina 80's. The Catalina tanks tend to be butt heavy and the Luxfers tend to be tail light at the end of the dive. The Luxfers are great tanks when it comes to trim and getting them out of the way if they are slung to the side.

 

[The Chairman]

I just did a liveaboard in the Sea of Cortez with AL80s. I used a weight pocket on each camband and put in a five pound weight. It was spot on perfect and it kept the back end from floating up during the dive. Here is the link: http://www.scubaboard.com/forums/si...ocio-del-mar.html?highlight=sidemount+musings