Help with wing lift calculation
- Thread starter 49north
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@seeker242 and @49north , thanks for your input!!
The error fixed and spreadsheets reloaded (same name: v9).
With regard to buoyancy calculations, it seems intuitive that we should add "fixed" weight like the reg set. Certainly in dry weight that counts, as does the weight of air in the tank. But for buoyancy purposes, the starting point is the tank's empty buoyancy, which as noted in the margin of the spreadsheet, may be supplied by the manufacturer computer with "valve included." In that case, the only thing that changes buoyancy is the added weight of air. So the reg cell can be left at "0" because the reg's weight (negative buoyancy, really) was already included in the empty tank number. If the table of buoyancy from the manufacturer does NOT include the reg's weight in the empty buoyancy calculations (and how did they measure that??) then you would of course need to add the reg's weight to the spreadsheet. For doubles, while the spreadsheet might not include the weight of either reg if the manufacturer did it already, the weight of the manifold alone should be inserted.
Thanks for the crowdsourcing on this. I appreciate the input. Let me know if you see other things that we should change.
Next will be a third page with weights, measurements and buoyancies for the various tanks from my tables. If others have data on odd tanks that I might not include, please PM me with the data. I already have Worthington, PST, Catalina, Faber and some US Divers old stuff.
The error fixed and spreadsheets reloaded (same name: v9).
With regard to buoyancy calculations, it seems intuitive that we should add "fixed" weight like the reg set. Certainly in dry weight that counts, as does the weight of air in the tank. But for buoyancy purposes, the starting point is the tank's empty buoyancy, which as noted in the margin of the spreadsheet, may be supplied by the manufacturer computer with "valve included." In that case, the only thing that changes buoyancy is the added weight of air. So the reg cell can be left at "0" because the reg's weight (negative buoyancy, really) was already included in the empty tank number. If the table of buoyancy from the manufacturer does NOT include the reg's weight in the empty buoyancy calculations (and how did they measure that??) then you would of course need to add the reg's weight to the spreadsheet. For doubles, while the spreadsheet might not include the weight of either reg if the manufacturer did it already, the weight of the manifold alone should be inserted.
Thanks for the crowdsourcing on this. I appreciate the input. Let me know if you see other things that we should change.
Next will be a third page with weights, measurements and buoyancies for the various tanks from my tables. If others have data on odd tanks that I might not include, please PM me with the data. I already have Worthington, PST, Catalina, Faber and some US Divers old stuff.
ams511
Contributor
Not in South Florida, but I have worn that much doing lake/quarry dives in Pennsylvania.
Jay
Need to dive more!
Thanks for the spreadsheets, it's very useful. A question about what 'at depth' approximately means wrt wetsuit compression; is this more of a Tec depth 'at depth' (vs. Rec) or does the difference become very marginal at anything deeper than Rec depth?
Ditching weights (at depth) is an interesting topic. (Naturally it's a no-brainer on the surface and we're not debating that). I agree my mindset had/has ditching at depth (mine or buddy's) as a last resort, and was struggling to think of under what circumstances I would fully ditch (with a primary view-point of: rec, tropical water, with a 3/2 wetsuit, 12# weight - plse assume my buddy is the same). Perhaps you we're writing form the perspective of having some ditchable weights as opposed to a weight belt as per "lighten the load" and there's several scenarios where that would help nicely, but fully ditching ... IDK.
So I did a little digging on SB and my take way is ditching some or all weight at depth vs. death is another debatable topic. If you have a link I could read more about weight ditching that would be great. I realise this is a bit OT.
FYI and for others wanting to read here's my SB reading list:
Do you care about ditchable weights?
Number one cause of diving fatalities?
The case against ditchable weight
Let's discuss dumpable vs non-dumpable weights
Buoyant ascents
How much negative buoyancy can you swim up with?
Thanks for your interest!
Wetsuit compression is significant even at recreational depth. Stand by for an improved spreadsheet after some collaboration with @kmarks, who had some great improvements. We should be uploading it soon.
As far as ditching weight goes. I am generally strongly against the thought, at depth. On the surface, that same reluctance kills divers.
But that said, if your buddy just tore his wing and has some fixed weight or exhaustion that makes swimming up impossible, then you're the rescuer.
I think it's better to be aware of what you're facing, and how much INCREMENTAL weight to shed to make a controlled ascent.
The spreadsheet allows you and your buddy to plan that in advance. Not an issue in tropical vacation diving. But doubles, or heavy neoprene, or deep...it's worth looking at in advance, IMHO.
With some outstanding ideas and programming support from Kevin Marks (@kmarks ), we are uploading the latest version of the Wing Lift Calculator.
This version has automated factors that several of you have asked about.
1) Exposure suit buoyancy is calculated based upon your body surface area and data you enter about your wetsuit/drysuit.
2) Tank buoyancy data can be selected from a list on the third page of the spreadsheet, which is then automatically transferred to the calculator.
3) Notes have been added explaining the purpose and use of the gray (user data entry) cells.
DISCLAIMER!!! This is a toy, for educational purposes only. It is a tool which only APPROXIMATES likely buoyancy with a given equipment and suit configuration.
Dive weighting decisions that you make, if based upon the approximations given here, MUST be checked with a neutral buoyancy check before any dive. As it is an amateur educational experiment, we make no guarantees about the accuracy of the results, and welcome your corrections and suggestions. The password for editing any of the sheets is "scuba" so you can change things at will.
This spreadsheet can assist the developing diver in several ways:
a) it can help you choose a wing or bcd to ensure adequate buoyancy for your equipment configuration;
b) it can aid you and your buddy, as you plan for a variety of equipment failures, including torn bcd/wing and flooded drysuit;
c) it can help you develop a safe "worst-case" ascent strategy using incremental weight ditching to allow a safe rate of ascent while making adequate surface buoyancy more likely;
d) it can show you why you need more or less buoyancy depending upon depth and tank pressure.
This tool was developed using standard formulas regarding pressure at depth combined with MANY ASSUMPTIONS based upon our collective diving experience.
We welcome your suggestions as we refine this tool. Again, my profound thanks to @kmarks for his valuable input!
7/4/18 EDIT: Locked an errant cell and changed formatting. Reloaded as file "Lift Calculator v10a"
This version has automated factors that several of you have asked about.
1) Exposure suit buoyancy is calculated based upon your body surface area and data you enter about your wetsuit/drysuit.
2) Tank buoyancy data can be selected from a list on the third page of the spreadsheet, which is then automatically transferred to the calculator.
3) Notes have been added explaining the purpose and use of the gray (user data entry) cells.
DISCLAIMER!!! This is a toy, for educational purposes only. It is a tool which only APPROXIMATES likely buoyancy with a given equipment and suit configuration.
Dive weighting decisions that you make, if based upon the approximations given here, MUST be checked with a neutral buoyancy check before any dive. As it is an amateur educational experiment, we make no guarantees about the accuracy of the results, and welcome your corrections and suggestions. The password for editing any of the sheets is "scuba" so you can change things at will.
This spreadsheet can assist the developing diver in several ways:
a) it can help you choose a wing or bcd to ensure adequate buoyancy for your equipment configuration;
b) it can aid you and your buddy, as you plan for a variety of equipment failures, including torn bcd/wing and flooded drysuit;
c) it can help you develop a safe "worst-case" ascent strategy using incremental weight ditching to allow a safe rate of ascent while making adequate surface buoyancy more likely;
d) it can show you why you need more or less buoyancy depending upon depth and tank pressure.
This tool was developed using standard formulas regarding pressure at depth combined with MANY ASSUMPTIONS based upon our collective diving experience.
We welcome your suggestions as we refine this tool. Again, my profound thanks to @kmarks for his valuable input!
7/4/18 EDIT: Locked an errant cell and changed formatting. Reloaded as file "Lift Calculator v10a"
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@rsingler and @kmarks: First of all a HUGE shout-out of thanks for all of your work on this!!!!!!
I though I'd pass along a cylinder spec reference that has quite a few of tanks beyond what is listed in the current version, including smaller 6-20 cuft ponys and lots of other fill-ins. Attached but from here: http://www.indianvalleyscuba.com/services page/Tank Inspection/information/CYLINDER SPECIFICATIONS.pdf
If you want to incorporate it, and it is helpful, I could enter the info early next week and get it over to you.
I also have few questions/comments/suggestions.
On the "First Stage Weight" and " Manifold + Second Reg Weight" sections, the notes are little confusing since your tank buoyancy values all include (singles) valves, but not regs, I'm not sure of the "valve" language.
I'm wondering if a more broadly functional approach might be:
- Primary-Gas regulator assembly weight(s) <- Include additional weight of bands and manifold assembly beyond standard valve(s) for doubles ---Justification: Theses are fundamentally "fixed" for backmount without ditching the rig
- Stage, Deco, Pony regulator assembly weight(s) ---Justification: These may be removed in normal use, hand-off, or emergency. There could also be multiple lines for these.
Can the wetsuit / drysuit liner thickness be easily moved to the primary page and co-located with wet/dry and condition? ---Justification: Once you set your height/weight, most of the variables other than tanks can be tweaked in one area
Would it be hard to add a Safety-Stop Depth buoyancy?
Justification: The way I see it, There are 4 key condition/depth combos:
- Start of Dive @ Surface - can I float (with inflated wing and everything or a failed wing and dropped weights) and how well?
- Start of Dive @ Depth - Is my wing big enough to get neutral and how much do I have to swim up (or come up with redundant lift) with/without weights if the wing fails?
- End of Dive @ Safety Stop - can I stay down with gas consumed and wetsuit re-expansion?
- End of Dive @ Surface - can I float WELL (with inflated wing and everything or a failed wing and dropped weights)?
An interesting addition might be to break out Rig vs. Diver buoyancies to estimate don/doff difficulties. It might be helpful to have weight-belt and rig ditch-able weights separate.
OK, a big, long-term sort of thought since it would be non-trivial:
It would be great to have the primary page layed-out such that it produces multiple, independent "scenarios" on one sheet. ---Justification: Users can easily run side-by side what-ifs or put together personal "standard" configuration tables.
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Thanks for your info and suggestions!
Well likely incorporate many of them in future iterations.
Not to say we disagree, but here's why some of the things are the way they are...
- We skipped small tank info since in an emergency, they can be jettisoned (unless you're surfacing in an emergency on your 30CF). Maybe need to rethink that...
- The organization was an attempt to avoid a "mega-spreadsheet", and concentrate results in the first page. That said, a data entry area separate from a multiple scenario results page is a good idea.
- As you might guess, this has morphed from a small one-off experiment into a bigger deal. With all the formulas and equations buried in the cells, it was problematic to do large moves and redesign, once we got too far down the road. Yet, we've actually started that process already and we thank you for your comments. Good suggestions!
Whoa! Brain fart! You're absolutely right - while valve weight is assumed in tank buoyancy, I completely neglected to account for reg weight. The recent Honker discussion on another thread makes that error obvious, lol! I got too involved in manifold weight (not counted) vs. valve weight (counted) for doubles divers. I'll fix that soon, and make the notes correct.
I'll plan a separate thread for the next iterations of this toy , for those few divers interested in following it, and having the "latest" version. I think that may also be a good discussion area for this whole topic of partial weight ditching. I'm trying to use the next version of the calculator to help us visualize what happens with a partial versus total weight drop. In a wetsuit, it's very different at depth than at the surface. Your "four scenarios" above are a great idea. I don't know if we have the screen sizes to do too many simultaneous possibilities, but we'll give it a shot.
Final thought - your request for safety stop buoyancy is a natural one. Unfortunately, that will have to await the day that one of us actually does some measurements of wetsuit buoyancy at 15' vs depth. We know what physics says about gas compression at depth, but the neoprene cell walls resist that compression to a greater or lesser degree depending upon structure, and that will affect buoyancy. So our buoyancy formula for your wetsuit at depth is a compromise estimate based upon experience and a lively debate between me and @kmarks . More to follow, one of these days.
Again, thanks for your interest! I'll put a link to the next thread on this toy here soon.
Well likely incorporate many of them in future iterations.
Not to say we disagree, but here's why some of the things are the way they are...
- We skipped small tank info since in an emergency, they can be jettisoned (unless you're surfacing in an emergency on your 30CF). Maybe need to rethink that...
- The organization was an attempt to avoid a "mega-spreadsheet", and concentrate results in the first page. That said, a data entry area separate from a multiple scenario results page is a good idea.
- As you might guess, this has morphed from a small one-off experiment into a bigger deal. With all the formulas and equations buried in the cells, it was problematic to do large moves and redesign, once we got too far down the road. Yet, we've actually started that process already and we thank you for your comments. Good suggestions!
Whoa! Brain fart! You're absolutely right - while valve weight is assumed in tank buoyancy, I completely neglected to account for reg weight. The recent Honker discussion on another thread makes that error obvious, lol! I got too involved in manifold weight (not counted) vs. valve weight (counted) for doubles divers. I'll fix that soon, and make the notes correct.
I'll plan a separate thread for the next iterations of this toy , for those few divers interested in following it, and having the "latest" version. I think that may also be a good discussion area for this whole topic of partial weight ditching. I'm trying to use the next version of the calculator to help us visualize what happens with a partial versus total weight drop. In a wetsuit, it's very different at depth than at the surface. Your "four scenarios" above are a great idea. I don't know if we have the screen sizes to do too many simultaneous possibilities, but we'll give it a shot.
Final thought - your request for safety stop buoyancy is a natural one. Unfortunately, that will have to await the day that one of us actually does some measurements of wetsuit buoyancy at 15' vs depth. We know what physics says about gas compression at depth, but the neoprene cell walls resist that compression to a greater or lesser degree depending upon structure, and that will affect buoyancy. So our buoyancy formula for your wetsuit at depth is a compromise estimate based upon experience and a lively debate between me and @kmarks . More to follow, one of these days.
Again, thanks for your interest! I'll put a link to the next thread on this toy here soon.
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