COMPARISON: Backplate and Wing to Stab Jacket BC

[rcohn]

Wow, lots of questions, let’s see……

Back to Ralph's discussion, it is a great report, i have some questions/comments, some on the subject of BP/W vs SP Classic, some more on your dives:

Did cave diver tell you he was a cave diver or was he just dressed the part? I take it he and Buddy were same ocean buddies then?

You’re the first person to pick up on the dive story. No, he was telling people on the boat about cave diving and how beautiful the caves were. He definitely presented himself as a cave diver. I don’t actually remember hearing him say he was an instructor that came from my wife. Also, I had no reason to doubt him, he had good trim, decent SAC, and a better command of hand signals than I do. Obviously his buddy skills could use improvement.

I am surprised you needed all that neoprene for

SE FL, its about 78F now isnt it? I was surprised at the little amount of weight you had for all that neoprene, i guess you are a lot more relaxed than me in that respect (therefore need less weight).

Actually I was wishing I had more! Expected 79 degrees like last year had 77 the first day and 75 the second. At those temperatures I would have brought my 5 mm suit and been happier. The Body Glove suit had 46 dive on it so it lost some buoyancy. And, I don’t believe relaxation has much to do with how much lead you need. With use and experience suits loose buoyancy and divers learn to get the trapped air out of their BCs, which should account for the reduction in lead.

If you used a SS BP that might have helped the trim out, although you pretty much wouldnt have had around 4# ditchable (or did you drop lower than 10# total in the end?). Due to its lack of extra padding, typically you can lose more than the just the buoyant weight of the plate (ie more than 2/6# for AL/SS) as noted elsewhere, ] i found the ranger to be a load of extra weight to get to stay down with compared to other jackets i rented before purchasing my BP/W.

Trim was fine, no help needed. I used 8 lb lead and the Al backplate throughout. I’d reduce some on the next dive, along with other adjustments if I continued using the system. I stripped the extra padding off the SP Classic years ago, so it has little residual buoyancy

I understand your concern about wearing the weight belt inside your crotch strap (again dont have to wear the strap), i do that more for convenience than anything, easier to sit down with it on and buckle up than wait until i have buckled up and then put on the belt - personal choice and if i need to drop the weight (IF) then it pulls out fairly easily from within the CS area once the belt buckle is released.

See, easy to slip into a less safe habit with a crotch strap. With my wife donning in the water the crotch strap it would be difficult for her to get the crotch strap under the weight belt

As for the rest of the strap, i am currently tightening up my shoulder straps and the belt (mostly due to losing 20# in the last 4 months). I find it easy enough to float on my back (face-up) on the surface and could probably sleep like that, i dont have that forward rolling thing going on - just have my BP and a few # in the back pockets of my weight belt - although thinking of putting some of that up on the tank straps.

Have you actually tried sleeping or is that just a guess? It is very easy to confuse minimal effort with no effort. Very few divers try going completely limp and seeing how they really float with no motion. Everyone should try it, you may be surprised. Most BCs put you on your face or on your side.

Oh and as for the surface area thing and drag, if you inflate the wrap around stab jacket, that would provide an extra 1-2" around your whole torso in the direction of flow, whereas the wing is only 1" across your back (and actually fills in that gap under your tank slightly too) so has less resistance. Your arms arent forced out to the side like stay-puft marshmallow man like the jacket, they can be streamlined behind your shoulders as they lie down your side - just a few places its more streamlined.

Nice try but you really need to measure it, there is a big lump of BC behind you head in the flow. Fluid flow is not that obvious, that's why flow tanks and wind tunnels are needed (or complicated finite element models) And the arm thing is a bit silly, I can put my arms wherever I want. If your jacket forces them out to the side, you definitely have the wrong BC.

All in all, you highlighted some good points about both BC types, i saw that overall you gave the SP Classic more +'s, and if i wanted a stab jacket, that looks like a good choice (however most jackets i tried were nasty in the past - personal thing) i prefer it my way, you prefer yours, c'est la vie. At least you can say you tried it, lots dismiss it without even trying it

BTW, did you get any of the Conch divers out there with you over your time down here - we are always up for a dive.

No I usually only read the Massachusetts section. Maybe next trip, previously we dove with Suzuki from the D2D board, but she has moved away.



Thank you for your comments.



Ralph

 

[simbrooks]

No, he was telling people on the boat about cave diving and how beautiful the caves were. He definitely presented himself as a cave diver. I don’t actually remember hearing him say he was an instructor that came from my wife. Also, I had no reason to doubt him, he had good trim, decent SAC, and a better command of hand signals than I do. Obviously his buddy skills could use improvement.

It takes two to be a buddy pair though, yes "cave diver" did drop to the bottom without him, but they didnt seem to know the other was missing and did their ascents and descents apart - not a safe pair in my books so far.

Actually I was wishing I had more! Expected 79 degrees like last year had 77 the first day and 75 the second. At those temperatures I would have brought my 5 mm suit and been happier. The Body Glove suit had 46 dive on it so it lost some buoyancy. And, I don’t believe relaxation has much to do with how much lead you need. With use and experience suits loose buoyancy and divers learn to get the trapped air out of their BCs, which should account for the reduction in lead.

My 3mm has as many dives on it, but is still good to high 60's, the 5mm comes out at lower temps (which we only get in NE FL and the gulf in the winter). As for weight, i am still slowly dropping a little (just about 50 dives so far under my belt) so things are still getting into that relaxed mode - i was thinking more of the newbie holding their average lung vol a little on the high side if you know what i mean.

Trim was fine, no help needed. I used 8 lb lead and the Al backplate throughout. I’d reduce some on the next dive, along with other adjustments if I continued using the system. I stripped the extra padding off the SP Classic years ago, so it has little residual buoyancy

Oh i thought you mentioned dropping some of moving it and the tank around to get better trim, i didnt say you needed help, but that it sounded like you were mentioning it was harder to trim due to your weight distribution options. I will say the BP/W does need a few dives to get the straps the right length, i recently decided mine was a little loose on the shoulders so a few dives later it feels much better - the waist band is coming in as i lose some belly!!

See, easy to slip into a less safe habit with a crotch strap. With my wife donning in the water the crotch strap it would be difficult for her to get the crotch strap under the weight belt

Sorry didnt quite understand this one, unless its about wearing the weightbelt in/outside the CS being safer arguement - i know it is elsewhere on the board in a few places, i know which i prefer - personal choice again. If it isnt that, then i have no idea what you are saying, sorry.

Have you actually tried sleeping or is that just a guess? It is very easy to confuse minimal effort with no effort. Very few divers try going completely limp and seeing how they really float with no motion. Everyone should try it, you may be surprised. Most BCs put you on your face or on your side.

Obviously not actually slept, but have lay motionless like lying on an air bed, very comfortable - however not as easy to do when in waves! Beds are for sleeping, water is for diving.

Nice try but you really need to measure it, there is a big lump of BC behind you head in the flow. Fluid flow is not that obvious, that's why flow tanks and wind tunnels are needed (or complicated finite element models) And the arm thing is a bit silly, I can put my arms wherever I want. If your jacket forces them out to the side, you definitely have the wrong BC.

We could do tests, do you have the money to fund the research?? I would be more than happy to carry it out for you, either in the tank or with FE and write some papers, just need the funds . Seriously though, i had some bad jacket BC's on rental, they were like life jackets and pushed my arms out about 1-2" off my side (increasing my area exposed to the water when horizontal - not by much though), with the BP/W i can get them down to the neoprene (out of the flow path behind my shoulders - i have large shoulders). My wing is only about 1.5" in dia. at the neck under the tank neck and tapers out to about 3" at the base of the horseshoe, the jackets were huge though - i stand by my qualitative research.

No I usually only read the Massachusetts section. Maybe next trip, previously we dove with Suzuki from the D2D board, but she has moved away

Well look us up if you think you are going to dive down here, that goes for anyone really visiting FL, i cant think of people (except dive pro's and maybe some hardy PNW people) who seem to have so many trips and dives going on.

 

[DA Aquamaster]

I also share your heads up surface position view and wonder if there is a BP/W design out there that will float a disabled diver face up? Anyone?

I share your concern and have worked to try to achieve this with a BP/Wing. I have lately been diving with a 7mm semidry, an OMS Aluminum backplate and harness, a Dive Rite Rec Wing and a set of Dive Rite weight pouches. With double steel 72's I get reliable face up floatation even with the wing fully inflated. If I go limp, I gently rock backward to a fully face up position. The setup works equally well with a dry suit as long as the suit is not extremely squeezed.

The key here is to place the weights as close to the BP as possible which essentially keeps them virtually underneath the floatation of the wing and well aft of the floatation provided by the exposure suit. The DR pockets do this very well. I have tried Halycon pockets but they extend too far forward with the weights being esentially even with the midline of the body. The use of a weight belt is also not practical due to problems with the belt rotating around to the front if the weights are not evenly distributed around the belt. This results in the weights again being too far forward from the back plate to float the diver face up.

Achieving face up floatation with a single tank, particularly a single AL 80, would require a sizeable trim weight on the back side of the tank itself to provide the negative bouyancy at the tank required to maintain the proper center of bouyancy when on the surface.

 

[Matthew]

Seriously though, i had some bad jacket BC's on rental, they were like life jackets and pushed my arms out about 1-2" off my side (increasing my area exposed to the water when horizontal - not by much though), with the BP/W i can get them down to the neoprene (out of the flow path behind my shoulders - i have large shoulders).

Do you really inflate your bc that much underwater?

 

[simbrooks]

That was with no inflation at all, the padding and huge pockets made the BC that large - think of a life preserver and then add some more padding and wearing about 4-5 sweaters at once before adding air to the BC. Then of course you add on the inflation of the BC (which depending on manufacturer can move inwards (and crush your diaphragm) or outwards) and you get a larger shape.

With my wing i probably have about 8# lift max in it at the beginning of the dive (in fact it feels almost empty and just lips around the tank a little - so really no addition to the frontal surface area like the jackets i have used - but a little material flapping in the breeze i guess which isnt too hydrodynamic), havent maxed it out on a single tank (even a single HP-120 i reckon only about 12# lift used, except when using it like a raft to lie upon whilst waiting to get out) - or at least it doesnt feel like there is much air in the wing.

As a side note i have maxed out my singles wing when i was trying out some Genesis HP-120 doubles (thinking about -12# per tank and a 6# SS BP - would have used a doubles wing an AL plate, but nothing else was available at the time) and that maxed out my 34# lift wing for most of the dive - the dive was only to ~30' in a lake i know VERY well, i could have crawled out, but i could just about swim up that rig - man was that heavy!! Just before you ask, i was trying the doubles out to see how i liked that kind of rig prior to thinking of buying two Gen 120's and finding out how they might act as doubles for me in the future when i got to that kind of diving and had purchased that kind of tank. I would get a bigger wing with redundancy and AL BP if i were doing a deeper dive in a less familiar area using the same kind of equipment - again when that time comes - just FYI about the amount of wing inflation i typically need.

 

[Green_Manelishi]

I also share your heads up surface position view and wonder if there is a BP/W design out there that will float a disabled diver face up? Anyone?

Thanks,

Jim

Using a DUI W&T II system with "most" of the weight AFT, a single tank (HP80), steel BP, and a drysuit I am turned onto
my back on the surface. YMMV.

Ralph, VERY well written. "You da man".

 

[rcohn]

Using a DUI W&T II system with "most" of the weight AFT, a single tank (HP80), steel BP, and a drysuit I am turned onto
my back on the surface. YMMV.

Ralph, VERY well written. "You da man".

Thanks G_M

I can easily believe that in the cold water, with so much lead or SS to play with you can find a distribution that achieves face-up floatation. However in the warm water, where roughly 50% on my diving occurs, this is not possible unless the diver is significantly overweighted. For warm water diving you need to move the air bubble rather than just the lead.

Ralph

 

[rcohn]

That was with no inflation at all, the padding and huge pockets made the BC that large - think of a life preserver and then add some more padding and wearing about 4-5 sweaters at once before adding air to the BC. Then of course you add on the inflation of the BC (which depending on manufacturer can move inwards (and crush your diaphragm) or outwards) and you get a larger shape.

Wow, you really had the wrong BC. A good vest is nothing like that. Of course if you happened to be severely overweighted, the high level of inflation in the vest might cause problems, but a decent vest still would not be as nearly bad as what you are describing.

Ralph

 

[simbrooks]

They were rentals that i used, i know they were cheap $150-200 affairs and quite poor, but even those for sale in a variety (i know of 10 within 10 miles of me) of LDS's looked and felt about the same (at least in wearing in the shop) for anything up to $450 - i also really dont like wrapping something around me amongst other things - hence went back-inflate and tried out some BP/W - much more pleasant.

As most people are when training i was over-weighted, i worked that down quite a bit and now am close with my current rig - still trying to shave off where i can though!

If i were to ever go further into being a pro or something i might wear a vest for pool work (something to take the chlorine hit and to make the students more comfortable), but i will stick with my BP/W. With an AL80 i wear 2# fresh and 8# salt with my 6# SS BP, might be able to take 1# off that i reckon for starters and maybe more if i keep my average lung volume a bit lower on ascents, but i have it controlled on ascents at that weighting with no air as i am just under the surface. Sometimes i have a little trouble descending (mostly cos i dont like to let all the air out of my wing - dont want to drop too fast due to my ear troubles) particularly in waves, but nothing too bad. However, i am in somewhat of a flux right now as i am dropping body weight, increasing muscle mass % and such, so my weighting may continue to drop further than anticipated - at the moment it feels only about 1-2# overweight, soon it might be more and i shall weight myself accordingly.

Its been a good discussion on this subject, better than a lot i have seen on here!!

 

[Matthew]

Oh and as for the surface area thing and drag, if you inflate the wrap around stab jacket, that would provide an extra 1-2" around your whole torso in the direction of flow, whereas the wing is only 1" across your back (and actually fills in that gap under your tank slightly too) so has less resistance. Your arms arent forced out to the side like stay-puft marshmallow man like the jacket, they can be streamlined behind your shoulders as they lie down your side - just a few places its more streamlined.

You did mention inflating, that's why I asked.

Regarding streamlining, I think it would take much more than 2" to force your arms out significantly beyond shoulder width, unless you are very big in the middle. Also, a jacket doesn't add anything significant to the frontal surface area against the direction of flow, at least in my case (pls. see drawing below).

They were rentals that i used, i know they were cheap $150-200 affairs and quite poor, but even those for sale in a variety (i know of 10 within 10 miles of me) of LDS's looked and felt about the same (at least in wearing in the shop) for anything up to $450 - i also really dont like wrapping something around me amongst other things - hence went back-inflate and tried out some BP/W - much more pleasant.

Do you remember what bc's they were and in what way were they poor? Usually bc's in that price range, especially rental ones, have little or no padding or added material, that's why I feel your marshmallow man description may be exaggerated. Of course I have to agree with you that a bp/wing is best in this regard as there is nothing on your sides and back.