Formula for estimating wing size?

[uncfnp]

Hi Dogbowl. What RyanT said. The 25 will be fine.

 

[MichaelMc]

The spreadsheet is hosted by DevonDiver but the actual creator of the spreadsheet is listed in the file. It is Constantin Novoselsky (cnovoselsky@hotmail.com). We should give credit where credit is due.

That said, this spreadsheet asks for things like "Head Weight" and "Suit weight". I KNOW my cold water rig requires 27 pounds to float. If I use my 25 pound wing, my gear slowly sinks. If I use my 27 pound wing my gear floats at the surface without me in it. I took guesses at what the numbers should be for the things I didn't know (head, suit, etc.) and most the time the spreadsheet was telling me from 18 to 23 pounds of lift.

This spreadsheet is overly complicated.

Darrell

The more complete version is at this post:
The "Ultimate" wing lift calculator :)
Though it is more complicated..
I'd love if it allowed splitting the weight belt from the integrated weights.

 

[NAM001]

Its a very simple process to get very close. Only a few rules. gear has to float when off the diver . diver with gear on has to float with head out of water.
assume your body is neutral (easy to comp fo this)
Take your full rig (full tank)and hang in on a rope in the water from a scale. it reads 15# so you you need a min wing of 16# to float the rig alone on the surface
same situation but you are wearing the rig with no wet suit. 16# to float you both and 10# to keep our head out of he water. total 25#
wearing a wet suit only reduces the surface min lift by the amount of suit lift.
going to 100 ft assume you loose all the wet suit lift from compression and you need a min lift of again 15# to be neutral at 100 ft.

The greatest of the min lifts of 16 or 25 is 25. Your min wing size is 25# for no suit and perhaps 15# with a wet suit on.

I would get a single wing to cover both with and without wet suit on instead of 2 wings.

If diving with out a wet suit you have (with a 30# wing) 5# reserve lift, with a wet suit on you have perhaps15# reserve lift. If this is done in salt water you will need the reserve in fresh water.

Any reserve lift covers other gear you might carry. reels cameras ect.

Most I know use a 28-32 # wing. If you are ALWAYS going to use a wet suit then perhaps a 18-23# will do.

 

[Dave Bevan]

Is there a rough formula for estimating wing size needed if given enough variables, such as wetsuit thickness, tank type, height and weight of diver, salt vs fresh water, etc? Thanks!

30lbs for single tank ali tanks, wetsuit and warmer weather.

40lbs for single tank, steel, drysuit and cold weather. Also for Single tank tech (twin valve or carrying stage for redundancy).

45lbs for tech 1 and tech 2 level (max 3 Ali stages). Cold or warm.

60lbs for when you start getting silly Twin 20litres, more than three stages.

 

[hammet]

Its a very simple process to get very close. Only a few rules. gear has to float when off the diver . diver with gear on has to float with head out of water.
assume your body is neutral (easy to comp fo this)
Take your full rig (full tank)and hang in on a rope in the water from a scale. it reads 15# so you you need a min wing of 16# to float the rig alone on the surface
same situation but you are wearing the rig with no wet suit. 16# to float you both and 10# to keep our head out of he water. total 25#
wearing a wet suit only reduces the surface min lift by the amount of suit lift.
going to 100 ft assume you loose all the wet suit lift from compression and you need a min lift of again 15# to be neutral at 100 ft.

The greatest of the min lifts of 16 or 25 is 25. Your min wing size is 25# for no suit and perhaps 15# with a wet suit on.

I would get a single wing to cover both with and without wet suit on instead of 2 wings.

If diving with out a wet suit you have (with a 30# wing) 5# reserve lift, with a wet suit on you have perhaps15# reserve lift. If this is done in salt water you will need the reserve in fresh water.

Any reserve lift covers other gear you might carry. reels cameras ect.

Most I know use a 28-32 # wing. If you are ALWAYS going to use a wet suit then perhaps a 18-23# will do.

So you're saying take a full tank and BC or wing without the weights, put in water and then weigh it in the water and it is 15lbs?
An Al80 tank full is about -2 lbs and a BC is probably about -2 lbs if even that.
There is so much fail here.

 

[NAM001]

So you're saying take a full tank and BC or wing without the weights, put in water and then weigh it in the water and it is 15lbs?
An Al80 tank full is about -2 lbs and a BC is probably about -2 lbs if even that.
There is so much fail here.

Those numbers have to be what is finally going on your back. integrated weight and all. not belt weight. (belt weight is not part of floating the rig with if off your back.
most of your kit weight is carried by your wet suit leaving little to nothing for the wing to carry, depending on BPW vs jacket al vs steel tank.
cold water more suit more integrated weight more wing needed to float the rig. My tank is -1 to -8.5 and i have an H valve on it with 2 regs. and a steel pack plate. All that means is that i have a larger min wing size to float the kit. compared to an al tank. The configuration is moot. the process is what counts.

It again was only an example. I use a steel tank H valve and steel backplate. my rig weighs around that. -6 back plate -10 for a full tank to float teh kit i need a min of 17+# lift wing 3/2 shorty and i need no weight. to be neutral at 20 ft 500 psi fresh water.
The process is more valuable than the specifics. An al tank is going to be much lighter and perhaps a 12# may be minimum on the surface with no wet suit.
once you get your numbers you can then put on your weights and then the numbers may very well go back to 15# min on the surface..

I was answering the question from a process point not from a point of was the weight distribution per DIR. Technally i should be using a al BP and use a weight belt. Or steel BP and al tanks. but the discussion was not about fresh or salt water. or configuration

Bottom line is that you have to have slightly more minimum lift than you kit has neg buoyancy when it is floating it self. using a scale in a pool is much easier than trying to calculate.

The same process goes for jackets. as it does for wings.

 

[decompression]

I'm no instructor and don't have anywhere near 5,000 dives, but this is just plain wrong.
You add your weight to your rig so that you are NEUTRAL with zero air in your BC or wing.
If you are too buoyant you add weight and subtract if too negative or course. But at this point you are neutral! (not withstanding 5lbs or so for air not yet consumed). The weight of your rig is irrelevant. If your rig was too heavy, you would have added less weights. If your rig was light, you would have added more lead.

As I stated before and echoed by another poster here, the only relevant thing you need air in your bc or wing to compensate for is wetsuit compression and air that you haven't used yet.

Hey Hammet.........I'm an instructor....so I'm never wrong....LOL. I see what you're saying and perhaps this will make sense.....

1. all the negatives, as mentioned are there to make you neutral at the end of the dive (slightly negative at the beginning due to gas, yes this is where you add air to the BCD to "compensate".
2. The rig, where you carry the weight, shouldn't be "too heavy or too Light" but if it is removed from your body which has a vast majority of the positive buoyancy (drysuit, wetsuit etc) is now very negative requiring a sufficient wing to keep it from plummeting it to Davy Jones's locker. If you were to wear all of your weight on a belt then, yes the weight of the rig is irrelevant (assuming its positive......Al 80 and a Poodle jacket).

Does that make sense?

 

[hammet]

Full disclosure... I was an instructor, just not scuba. I used to teach college physics

So maybe we are just talking over each other, but maybe not. Whether we are talking about steel tanks, aluminum tanks, double tanks, h-valves, ball valves, .. whatever... it makes no matter... and unless I'm not aware of some super secret aspect of recreational diving, there is no need whatsoever to 'float a rig' in the water. And even if one had to remove a rig in an emergency, even the smallest BC has the lift capacity to keep most setups from sinking, (My 11lb Outlaw bladder on a twin steel setup full of air and weights bolted to the back plate notwithstanding). I will reiterate the following and if I am wrong, please show me where...

For a diver that is PROPERLY WEIGHTED, that is, neutrally buoyant at the surface at 500psi with zero air in the wing or BCD, the only lift an air bladder is required to provide is to:

1. Counter the weight of the unconsumed gas at the start of the dive
2. Counter the effect of the loss of buoyancy of a diver's wet suit.
3. Allow the diver to bob comfortably at the surface.

Note even that there is no circumstance where all three of these conditions are met at the same time.

Now if you take extra gear with you without reducing your lead, then of course, you will need more lift. If you pick up a gold bar from the bottom, of course you will need more lift.

 

[cool_hardware52]

Full disclosure... I was an instructor, just not scuba. I used to teach college physics

So maybe we are just talking over each other, but maybe not. Whether we are talking about steel tanks, aluminum tanks, double tanks, h-valves, ball valves, .. whatever... it makes no matter... and unless I'm not aware of some super secret aspect of recreational diving, there is no need whatsoever to 'float a rig' in the water. And even if one had to remove a rig in an emergency, even the smallest BC has the lift capacity to keep most setups from sinking, (My 11lb Outlaw bladder on a twin steel setup full of air and weights bolted to the back plate notwithstanding). I will reiterate the following and if I am wrong, please show me where...

For a diver that is PROPERLY WEIGHTED, that is, neutrally buoyant at the surface at 500psi with zero air in the wing or BCD, the only lift an air bladder is required to provide is to:

1. Counter the weight of the unconsumed gas at the start of the dive
2. Counter the effect of the loss of buoyancy of a diver's wet suit.
3. Allow the diver to bob comfortably at the surface.

Note even that there is no circumstance where all three of these conditions are met at the same time.

Now if you take extra gear with you without reducing your lead, then of course, you will need more lift. If you pick up a gold bar from the bottom, of course you will need more lift.

I'd suggest your assumptions need to be examined and perhaps expanded a bit.

In particular your definition of proper weighting. Neutral at the surface with 500 psi is proper IMO only when using thin exposure suits with little initial buoyancy, and when using thin suits minimum wing capacity is almost always based on being able to keep the divers rig, with a full cylinder at the surface if they need to ditch it. In warm water the buoyancy of the diver's suit is seldom the controlling factor.

If we then consider a diver using a thick, buoyant suit, where the buoyancy of the suit exceeds the max negative value of the rig with a full cylinder, my definition of proper weighting is:

The minimum ballast necessary to maintain a shallow safety stop with a near empty cylinder.

That suggests that the buoyancy of the diver's suit *at* the Safety Stop depth, not the surface, is the issue. As the percentage change in ATA is most dramatic near the surface (from the surface to ~33 FSW the pressure doubles) and the typical safety stop is at ~1.5 ATA the change in buoyancy of a thick suit can be substantial from the surface to ~15 ft. This reduction in the volume displaced and associated buoyancy of a 7mm wetsuit, or drysuit with coldwater undies can easily exceed the weight of gas carried in a typical single cylinder, or somewhere around 6-7-8 lbs.

That would suggest that a diver who is weighted so that they are eyelevel at the surface with a full single cylinder and no gas in their BC will be able to hold a shallow stop with a near empty cylinder. Being weighted as you suggest would result in the same diver being ~6-7-8 lbs negative at 15ft.

I'm not a fan of being overweighted. It makes buoyancy control more difficult, and will result in a diver being negative by the weight of their gas at the surface at the beginning of the dive. This is IMO an unnecessary risk.

Diver's weighted as I suggest can easily stay at the surface if they panic, fail to inflate their BC, fail to drop ballast etc. etc. Diver's weighted as I suggest will be positive at the end of the dive due to consuming gas.

If one accepts my definition of proper weighting then required wing capacity is very straight forward:

Whichever of the following is larger dictates minimum required lift capacity.

1) Enough wing capacity to float the divers rig if they ditch it (or wish to don in the water)

&

2) Enough wing capacity to be able to compensate for the maximum possible change in buoyancy of their exposure suit. Exposure suits, wet or dry cannot lose more capacity than they start with.

This methodology works with thicker suits and normal single cylinders. Thin suits or larger gas volumes will require the diver be negative by at least a portion of the weight of their backgas.

Tobin

 

[MichaelMc]

there is no need whatsoever to 'float a rig' in the water. And even if one had to remove a rig in an emergency, even the smallest BC has the lift capacity to keep most setups from sinking

As a cold water counter example, I dive single aluminum tank with a 30lb wing to shallow depths. But I have a 20/10mm farmer john and hooded top that takes 35 pounds of ballast. If all that was in my rig, it would sink fast. Hence the rule of floating the rig, and a reason I keep 13 pounds of it on my waist.

It is industrial skin in rubber; I do not go deep, and am not a new diver.