Info The "Ultimate" wing lift calculator :)

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I got confused by the values in the right column being positive for negative buoyancy and changed it so objects that sink are negative and colored them blue as you did on the left column. I just bought a Faber HP117 so I added it. The tank list on the second tab seems to be backwards with positive buoyancy being negative and negative buoyancy being positive. I didn't change these. Here is the spreadsheet.
View attachment ST BPW Buoyancy.xls
 
bj, your formatting got messed up somehow. Anyway, the cylinder values are mfg specs. Good suggestion on right side values (been fixed.)
 

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  • Buoyancy Estimate Worksheet.xls
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bj, your formatting got messed up somehow. Anyway, the cylinder values are mfg specs. Good suggestion on right side values (been fixed.)

I reloaded the first two spreadsheets from the thread and buoyancies are negative when they should be positive and vice versa. Your latest spreadsheet corrects this. I was just too lazy to do this.:) I still prefer values to be entered by the user to be all one color but to each his own. Nice job on cleaning it up.

I had some buoyancies of two wetsuits on the cylinder tab. These were from people on SB actually reporting tests they had done in a pool with weights(Bare 7mm step in vest +11 lbs., Neosport 7mm Farmer John and top +31 lbs.)

Bill
 
im not sure if im using the calculator right, but i ended up needing 31.8# for the wing and no additional weight. Maybe its because im not calculating the drysuit correctly? Or is this common?

Thanks!
 
im not sure if im using the calculator right, but i ended up needing 31.8# for the wing and no additional weight. Maybe its because im not calculating the drysuit correctly? Or is this common?

Thanks!

Exposure suits are tricky to account for, and I'm not a drysuit diver, but my thought would be that the drysuit has no inherent buoyancy without adding air. Also, the amount of undergarment you wear may have some effect on overall displacement. I would recommend chatting with some of our regular tech/drysuit divers on SB for guidance on this.
 
im not sure if im using the calculator right, but i ended up needing 31.8# for the wing and no additional weight. Maybe its because im not calculating the drysuit correctly? Or is this common?

Thanks!

Lift should be calculated on the basis of the negative buoyancy you have at the beginning of the dive. Could your buoyancy be something like this?

-10 lbs head weight
-10 lbs for 120 cuft steel tank
-6 lbs for SS BP
-6 lbs weighted STA

Total -32 lbs

The drysuit should only affect the amount of weight you need and not the BC lift needed. The drysuit is maybe about +20 lbs buoyant, depending on underwear, so you should have more than enough weight to be neutral.
 
Lift should be calculated on the basis of the negative buoyancy you have at the beginning of the dive. Could your buoyancy be something like this?

-10 lbs head weight
-10 lbs for 120 cuft steel tank
-6 lbs for SS BP
-6 lbs weighted STA

Total -32 lbs

The drysuit should only affect the amount of weight you need and not the BC lift needed. The drysuit is maybe about +20 lbs buoyant, depending on underwear, so you should have more than enough weight to be neutral.


The single most important element in determining minimum required wing capacity for cold water diving is the buoyancy of the exposure suit.

There's really no need to make calculating wing capacity some sort of black art requiring spread sheets and higher math.


1) Enough lift to float the divers "rig" with a full back gas and no buoyant diver attached, i.e. the rig if it is ditched.

2) Enough lift to compensate for the maximum possible change in buoyancy of the divers exposure suit. Wetsuits compress, and drysuits have the potential for a total failure. In either case the exposure suit cannot loose more buoyancy that it started with at the surface.


Whichever is larger, 1 or 2 will dictate the minimum capacity. In most cases in cold water it will #2 (the suit) and in tropical conditions it will be #1

Tobin
 
The single most important element in determining minimum required wing capacity for cold water diving is the buoyancy of the exposure suit.

There's really no need to make calculating wing capacity some sort of black art requiring spread sheets and higher math.


1) Enough lift to float the divers "rig" with a full back gas and no buoyant diver attached, i.e. the rig if it is ditched.

2) Enough lift to compensate for the maximum possible change in buoyancy of the divers exposure suit. Wetsuits compress, and drysuits have the potential for a total failure. In either case the exposure suit cannot loose more buoyancy that it started with at the surface.


Whichever is larger, 1 or 2 will dictate the minimum capacity. In most cases in cold water it will #2 (the suit) and in tropical conditions it will be #1

Tobin

You are right. I said the wing lift needed is only determined by the amount of weight you are carrying and not by the drysuit buoyancy. The wing lift needed IS determined by the amount of weight you are carrying but the amount of weight you are carrying IS determined by your drysuit buoyancy.

The drysuit buoyancy is counteracted by weight carried in order to get neutral. If the drysuit floods the wing must be able to take over this buoyancy. So we are both right, me saying the weight carried determines the wing lift needed and you stating exposure suit buoyancy determines the lift needed. The wing could really be considered backup buoyancy in case of drysuit failure.

1. Pick exposure suit needed to stay warm >
2. determine weight needed to descend with #1>
3. determine wing lift needed to ascend if exposure suit fails.

What size wing would be the best for a typical coldwater drysuit or wetsuit diver if he could only afford one?

Respectfully,
Bill
 
What size wing would be the best for a typical coldwater drysuit or wetsuit diver if he could only afford one?

Respectfully,
Bill

Which suit is the most buoyant, and how buoyant is it?

Minimum wing capacity need to be no less than the initial (surface) buoyancy of the most buoyant suit the diver will use with it.

Tobin
 
Tobin,

If my most buoyant suit is 30 lbs. and I am diving doubles why would I need a 94 lb. wing?

Bill
 
https://www.shearwater.com/products/teric/

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