Fixing diver trim and weight placement

[FishWatcher747]

@Comm and @inquis - if I move my 4# to tank trim pockets, that's all my weights and then I have no droppable weight. I'm led to believe that's a bad idea?

Edit to add: This is in fresh water (pool), so I guess in an saltwater situation that may not be an issue?

I use one ditchable tank band trim pocket which holds around 4 of 5 pounds usually. Pull on the velcro cover and it is ditched. The other trim pocket is nonditchable. If needed I can reach around and dump this weight if needed. There is no reason one of your camband trim pockets can't be dumpable.

I use an aluminum plate and dive only warm water which gives me more weight to trim out than using a steel plate.

 

[wdeutsch]

I use one ditchable tank band trim pocket which holds around 4 of 5 pounds usually. Pull on the velcro cover and it is ditched. The other trim pocket is nonditchable. If needed I can reach around and dump this weight if needed. There is no reason one of your camband trim pockets can't be dumpable.

I use an aluminum plate and dive only warm water which gives me more weight to trim out than using a steel plate.

Thanks for that info! I didn't realize there were ditchable pockets for the tank bands - didn't think they'd be reachable. I'll definitely look into that.

 

[atestani]

May I suggest the ditchable weight discussion be taken to one of the 80 threads on that subject (yes there are that many with "ditchable" in the title). This is a very informative thread on trim with knowledgeable people contributing... I think we should keep it that way. Thanks

 

[atestani]

I have just switched to a BPW after over 600 dives with a jacket and am trying to get some starting points by going to a pool and to work out weight distribution for trim. I have 3 wetsuit configurations (7mm full, 1.5mm full, and no neoprene, i.e. skin) and 2 tank types/capacities (AL80 and S100) I want to work out. Due to the steel backplate, only the 7mm cases needs additional lead so I plan to "overweight" by 2-4 lbs for trim weights (and keep some gas in my BCD). Extra lead (when needed) will be in a weight belt. (BTW, I am not concerned about not having any ditchable weight because I carry an SMB which can provide lift in the rare case of a total BCD failure.)

I have adjusted the harness as has been mentioned in this forum and plan to mount the AL80 as low as possible (upper cam band at the start of the tank curve) and the S100 about 4" higher when I am using it. I want to understand trim at 90 feet with a full tank and at 15' with 500psi remaining but, obviously, can't do 90 feet in the 15' deep pool. Therefore my thought is to establish a "midpoint trim" by using an AL80 which is 35% full (~1000psi) and an S100 at 50% full (~1800psi). My thinking is that if I get to horizontal trim under those conditions, the change across 15ft/500psi to 90ft/full range will be manageable by adjusting body position.

Since I will most likely be doing this in the pool alone (long story), my plan is to get slightly negative and motionless on the pool bottom then take a deep breath (or put air in the BCD), push off, and see which end rises. I will have some weights with me that I will pick up and position toward the end that rises so I know where to add the trim weight.

I would start with the 1.5mm wetsuit case and do the above experiment with both the AL80 and S100 and then repeat with the 7mm and no wetsuit cases.

I am very interested in what you people think about this plan.... so don't hold back.

 

[inquis]

I want to understand trim at 90 feet with a full tank and at 15' with 500psi remaining

Fix trim at 500 psi by moving trim weight. Then adjust wing position to fix trim with a full tank. (Both done in the pool.) Ideally the wing would be empty for the first phase; but if you're a bit overweighted, you may have to iterate these steps a second time.

I've found the shift in center of buoyancy due to wetsuit compression at 90 ft to be negligible.

Be mindful that each combination of suit & tank mandates its own optimal trim weight placement. Keep notes!

 

[atestani]

Fix trim at 500 psi by moving trim weight. Then adjust wing position to fix trim with a full tank. (Both done in the pool.) Ideally the wing would be empty for the first phase; but if you're a bit overweighted, you may have to iterate these steps a second time.

I've found the shift in center of buoyancy due to wetsuit compression at 90 ft to be negligible.

Be mindful that each combination of suit & tank mandates its own optimal trim weight placement. Keep notes!

Sorry, I shouldn't have said I need to know trim at 90 ft. I should have said I want to know the trim with tanks full and at 500psi.

I am trying (hoping) to get to a single wing position for all combinations and single tank position for each tank type and only move trim weights for different suits. Possible?

My thought of doing the trim testing with 35% full for AL80 and 50% full for S100 is an attempt to trim at the "midpoint" of tank buoyancy change as gas is consumed, the idea being that the trim change from the midpoint to the extremes (full and 500psi), is small and manageable with body position. Does this make sense?

 

[inquis]

I am trying (hoping) to get to a single wing position for all combinations and single tank position for each tank type

If the center of the gas is in the center of the wing, that wing position is good. That means taller tanks will have higher valves, but I wouldn't expect the 1/2" taller AL100 to impact things noticeably.

Do note that some wings have only a single position, so some iteration in tank position may be necessary. Then again, close enough is close enough. Only you can make that call.

 

[happy-diver]

I really do feel that more emphasis must be put on how a diver holds their body through posture

How To Achieve Perfect Body Alignment | FlowState Divers

Knowledge review of How To Achieve Perfect Body Alignment.

flowstatedivers.halocrom.com

If you dive like a sack of potatoes, that is how you look, so dive your gear not the gear diving you

 

[atestani]

If the center of the gas is in the center of the wing, that wing position is good. That means taller tanks will have higher valves, but I wouldn't expect the 1/2" taller AL100 to impact things noticeably.

Do note that some wings have only a single position, so some iteration in tank position may be necessary. Then again, close enough is close enough. Only you can make that call.

I am working with an AL80 and Steel 100.