Advice on lift capacity for BP&W

[Magnus Lundstedt]

I dive Poseidon much to the dismay of my main dive buddy @victorzamora who would rather drown than breathe on them. I don't disagree with you on design, but they can easily machine on par with Poseidon

I hope you noticed the " ;-) ", it was meant not to be serious, i can myself machine to a much higher quality standard. (if time is not an issue)

But you know, for me as a swede, "made in Sweden" is worth some extra points, but only some. ...

Yea, i acctualy do not use Poseidon 1'st stages, tho i have a bunch of them, i don't like the type of rubber hat you use to seal them for cold water, I resently bought one Poseidon yoke-reg that i going to use as travel/warm water reg.

But i love the Jetstream's 2'nd.

 

[rsingler]

Hi fellow divers!
I am planning to buy a BP&W system and I am struggling to choose the lift capacity for the wing. I am moving from jacket systems to BP&W, so I thought of getting some tips from you folks.
I am 5'9, 155lb NorCal diver. Use 7 mm wetsuit and dive with 22lbs on a jacket BC. What would sufficient lift capacity that I should look for?
Also, I want to travel with it and I do dive in tropics too. I don't want extra capacity if that is not needed (seems that creates extra drag).
Please let me know.
I did like HOG Total Buoyancy Control System Package,DiveRite Transpac, Hollis L.T.S. Light Travel System and DRIS Mirage 23/38lb BP/W Package. DRIS system seems to provide both lift capacity as and when needed.
Anyone has any experience or preference between these?

Thanks again
Abhi

This subject seems to come up with regularity.
So I put together this little spreadsheet that will calculate lift requirements based upon a number of factors that you can change.
It is formatted in the current Excel .xlsx, and in the older Excel format .xls
It can be used with both wetsuit and drysuit diving, with some assumptions as follows:
I arbitrarily assumed that your wetsuit would lose 60% of its buoyancy at depth.
I arbitrarily left the weight of 15% of your stated air supply on board in calculating lift requirements at the end of a dive.

To use the spreadsheet, just fill in the grey areas in Column F.
MAKE SURE THE SIGN IS CORRECT.
Positive numbers are buoyant, Negative numbers sink.
For example, carried lead is -10, not 10.

The spreadsheet is protected with the password "scuba", so if you find mistakes, feel free to jump in and edit the formulas.

There are a number of "Calculated Wing Requirements" given at the bottom of the spreadsheet, depending upon your risk tolerance.
For example, if you want to assume that you'll be able to trap 5# of buoyancy in the leg of your flooded drysuit, go ahead and carry a smaller wing.

The spreadsheet has been set up for doubles, so if you want to calculate single tank wing requirements, just enter "0" for manifold weight and cut the air carried in half. Conversely, if you're calculating for doubles, and carrying twin AL80's, make sure to enter 160 for air.

There should be a table of suggested values for the various fields, but I haven't gone to that effort yet. You'll need to decide how much native buoyancy your suit carries, and you'll need to look up the 500psi buoyancy of your tank, but that data is available on SB in one thread or another.

In the calculations section, there are groups of "things you can control" and "things you can't control easily". This too, was arbitrary. Obviously you can change your backplate, but not easily. Conversely, maybe you can't change the weight of your air easily, but I grouped air weight there to show more graphically what happens when you switch from big to small tanks, or steel to aluminum.

Finally, there's a little section at the bottom for "redundant lift required". In the event of a torn wing, how do you want to handle it? A second bladder? A lift bag? Your drysuit? Just swimming that weight up on your own? This tells you how much add'l lift you need to carry, or how much you'll be finning up to the surface without redundant lift, and is obviously the opposite of your empty wing buoyancy at that point, which is duplicated in several cells a few rows up.

Have fun!
Please let us all know if you find mistakes. I just did this off the top of my head after reading thru this post.

Cheers!
Rob

EDIT: Sign of weight of air carried was reversed for consistency. Spreadsheets reloaded.

EDIT 3/30/19: the spreadsheets that used to live here are now obsolete, and have been replaced by the tool in Optimal Buoyancy Computer

 

[АлександрД]

I`v translated my old estimation of minimal BCD volume.
Wetsuit buoyancy: Loss in depth - how big should be BCD - here I put it as separate topic for discussion, if I have mistakes in my counts.

Conclusion from there - 9mm wetsuit buoyancy loss at 40m is around 10 kg.
Air weight in one 12Lx200bar tank (like Al80) around 2 kg.
So - you should have minimal BCD volume around 12 L (27 lbs) and it is just for safety.

When you are with your buddy - you should have it twice! (for your buddy brocken BCD).

When somebody make acronym of BCD - he loss also one letter - Buoyancy LOSS Compensation Device.

You should not calculate your lamps, cameras, lead, Backplates, tanks, etc.
You should just count items, that can LOSS buoyancy at the depth, or change weight.
There is: Neoprene and Air in tanks.

Does not matter, how much your thrash is weared on you - When you had neutral buoyancy at surface - better to have it with empty BCD (+2 kg for air weight). It mean - you are neutral!
Thats all! Others is just compensation of BOUYANCY LOSS during descent.

 

[Abhijit Roy]

This subject seems to come up with regularity.
So I put together this little spreadsheet that will calculate lift requirements based upon a number of factors that you can change.
It is formatted in the current Excel .xlsx, and in the older Excel format .xls
It can be used with both wetsuit and drysuit diving, with some assumptions as follows:
I arbitrarily assumed that your wetsuit would lose 60% of its buoyancy at depth.
I arbitrarily left the weight of 15% of your stated air supply on board in calculating lift requirements at the end of a dive.

To use the spreadsheet, just fill in the grey areas in Column F.
MAKE SURE THE SIGN IS CORRECT.
Positive numbers are buoyant, Negative numbers sink.
For example, carried lead is -10, not 10.

The spreadsheet is protected with the password "scuba", so if you find mistakes, feel free to jump in and edit the formulas.

There are a number of "Calculated Wing Requirements" given at the bottom of the spreadsheet, depending upon your risk tolerance.
For example, if you want to assume that you'll be able to trap 5# of buoyancy in the leg of your flooded drysuit, go ahead and carry a smaller wing.

The spreadsheet has been set up for doubles, so if you want to calculate single tank wing requirements, just enter "0" for manifold weight and cut the air carried in half. Conversely, if you're calculating for doubles, and carrying twin AL80's, make sure to enter 160 for air.

There should be a table of suggested values for the various fields, but I haven't gone to that effort yet. You'll need to decide how much native buoyancy your suit carries, and you'll need to look up the 500psi buoyancy of your tank, but that data is available on SB in one thread or another.

In the calculations section, there are groups of "things you can control" and "things you can't control easily". This too, was arbitrary. Obviously you can change your backplate, but not easily. Conversely, maybe you can't change the weight of your air easily, but I grouped air weight there to show more graphically what happens when you switch from big to small tanks, or steel to aluminum.

Finally, there's a little section at the bottom for "redundant lift required". In the event of a torn wing, how do you want to handle it? A second bladder? A lift bag? Your drysuit? Just swimming that weight up on your own? This tells you how much add'l lift you need to carry, or how much you'll be finning up to the surface without redundant lift, and is obviously the opposite of your empty wing buoyancy at that point, which is duplicated in several cells a few rows up.

Have fun!
Please let us all know if you find mistakes. I just did this off the top of my head after reading thru this post.

Cheers!
Rob

EDIT: Sign of weight of air carried was reversed for consistency. Spreadsheets reloaded.

Dude..this is mad scientist stuff...serious good karma points! May your lift always be adequate, tank full of air and scuba light never fails..

 

[rsingler]

Don't quite know about that. But thanks! Hope it's useful as you change equipment configurations.

 

[Abhijit Roy]

Hey everyone! Thanks for all the advice and recommendations. I got myself a HOG system this weekend. Red aluminium back-plate and 32lb wing configuration. That red is sexy to say the least !! Tried at work aquarium with 7mm semi-dry and 20 lbs of weight. Super comfortable dive and didn't feel like I needed too much lift at 20 ft. So, hopefully 32lb will be enough for open water and with pony bottles. I think I got hitched ;-)

 

[rsingler]

The lift calculator idea has progressed over the six months since this thread.
Take a peek:
Buoyancy, Balanced Rigs, Failures and Ditching – a comprehensive tool

EDIT 3/30/19:
The thread above has been replaced by
Optimal Buoyancy Computer
The original thread is preserved for background, but without the obsolete spreadsheets.

 

[DiveTy]

Looking at VDH wing 23# and plate is there a discount code here on SB? Sorry posted on wrong thread

 

[Barnaby'sDad]

Hey everyone! Thanks for all the advice and recommendations. I got myself a HOG system this weekend. Red aluminium back-plate and 32lb wing configuration. That red is sexy to say the least !! Tried at work aquarium with 7mm semi-dry and 20 lbs of weight. Super comfortable dive and didn't feel like I needed too much lift at 20 ft. So, hopefully 32lb will be enough for open water and with pony bottles. I think I got hitched ;-)

I've got the HOG 32lb wing. It provides plenty of lift for a HP100 and an AL40.

I've changed tanks (AL80 to HP100) and backplate (soft plate to steel plate), but I don't see me changing my wing anytime soon. Enjoy.