Harness adjustment question

[cool_hardware52]

1. You should adjust the plate such that it can be touched when you reach back over your shoulder.

^^This is IMO a very imperfect way to try and determine plate position. It's almost entirely dependent on the flexibility of the individual. Don't fixate on being able to touch your plate.

2. Don't make your harness too tight!!!

As other's have noted it's the in water position that matters. Everybody will spend the first few dives tweeking their harness.

Tobin

---------- Post added July 19th, 2015 at 11:48 AM ----------

Yeah. I'm thinking building about a quick adjust solution. DSS has a "glide adapter" for the backplate that would make it easier to adjust on the fly. Theirs is formed 11ga sheet, which is tough for me to replicate but I may just machine something similar from 316L billet. I think you could actually make it a bit cleaner that way by tapping the threads directly into the part instead of using a separate nut.

Would never make sense that way as a production product (ie: DSS bills it the right way for a business) but my time standing in front of a Bridgeport actually counts as "leisure" and I've got a bunch of 316 drops from a prior project.


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Captive (tapped) threads in the GHA would prevent it's use with the DSS weights plates.

Tobin

 

[benha]

Great feedback. Thanks Tobin and everyone else!

Hadn't thought about the weight plates. After I get in the water and figure out the weight requirements I thought I might cnc up some single use lead molds from wood (yes, this actually works) for something with the right volume to make the rig neutral. The lead for my exposure suit / natural buoyancy needs to go on my waist per my earlier observation that I spend a lot of time with my tank off. I suspect the rig will already be slightly negative when fully deflated with an HP119, but I'll know soon.

As soon as I get back from a trip to India on business. Sigh...


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[cool_hardware52]

Great feedback. Thanks Tobin and everyone else!

Hadn't thought about the weight plates. After I get in the water and figure out the weight requirements I thought I might cnc up some single use lead molds from wood (yes, this actually works) for something with the right volume to make the rig neutral. The lead for my exposure suit / natural buoyancy needs to go on my waist per my earlier observation that I spend a lot of time with my tank off. I suspect the rig will already be slightly negative when fully deflated with an HP119, but I'll know soon.

As soon as I get back from a trip to India on business. Sigh...


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With 7 lbs of SS backplate and harness and ~2 lbs of regulator your rig is -9 lbs before you add a cylinder. Your 119 is never going to be +9

Tobin

 

[kensuf]

I use a balled fist as a starting point in the shoulders and then dive it/adjust it from there. I start with the harness adjusted loose enough that my balled fist can fit in between the webbing and the front of my shoulder.

The main attachment point/adjustment comes at the waist and crotch strap. Those should be snug enough to hold everything down without leaving you singing a high pitch.

Here.. https://www.divegearexpress.com/library/articles/harness-assembly-instructions

 

[benha]

This gets pretty far from the topic at hand but now that we're on weight and balancing:

Has anyone ever messed around with using "uncompressable floats" to adjust rig balance? I've got buoyancy and trim reasonably well in check - though I'll have to start over again with the new rig - but I've struggled for years with the fact that the big steel tank on my back always wants to turn me over on my butt once I start contorting myself to look under rocks, grab lobsters, etc. It's just a lot of weight way off the centerline, and once you let it get too far over it wants to get to the lowest point.

It strikes me that a couple of small floats - perhaps capped aluminum tubing rigged parallel to the tank - might help offset all that weight way off my centerline? If I took a pair of 18" long 1.25" Ø aluminum tubes and capped them they'd weigh virtually nothing and displace about 5# worth of water. Should have minimal effect on streamlining and the overall rig would still be negative - just balanced differently.

I suspect this is "crazy" in that the last thing most people want to do is modify their gear in a way that means they need to carry more lead, but I'm curious what y'all think about it.

---------- Post added July 21st, 2015 at 12:40 AM ----------

Ack. Got my math wrong. (1.25" Radius, not Diameter). Whole different animal strapping 2.5" floats to the tank than 1.25".

Still an interesting concept if you ask me, but would take more thought to pull it off in a streamlined manner

 

[Nasser]

I think you are looking for solutions that can generally be dealt with by diving a balanced rig and fine tuning your harness and weight distribution.

It's true that heavier cylinders tend to make you want to turtle - especial singles, but by counter balancing with a weight belt or weight pockets towards the side/front you can off-set some of the weight on your back. Additionally, you can adjust the height of your back plate to your wing to tweak your forward tilt by trying out different positions on the wing (most wings have three holes on the top and bottom to choose from when attaching to the mounting screws of a STA or the doubles steel cam bands).

Try not to over think this too much. Just spend some time with your gear and make adjustments as you go along... also work on your technique (trim, propulsion, buoyancy etc..) in your new configuration and soon enough you'll be gliding comfortably in the water.

 

[benha]

Yeah, I'm prone to over thinking things and this is probably one of those "just live with it" items.

I will say, however, that this isn't about the normal use case of swimming along staying well trimmed.

The situation is more:

You're not neutral because you wanted to stay planted while you were tearing apart a rock pile to get the lobster that's 2" further in than you can reach without getting pulled off by the surge.
You finally get said lobster and have both hands full of annoyed crustacean.
Your mask is half flooded because the final lunge to get the bug displaced it against a rock.
You're no longer holding onto the rocks and even though you're heavy there's a gnarly surge that's picked you up and is rolling you around.
You're very occupied trying to find your lobster gauge, clear your mask, measure the bug, and stuff it in a bag.
The sea bottom is littered with needle-sharp urchins.
That damned tank is turning you on your backside making it all that much harder to stay focused.

My experience with trim has been that nothing I do with weight alone will make me completely stable at all angles of roll about my long axis. You can make yourself more or less prone to rolling within the normal swimming position, but without mounting weights 6" off your belly there isn't any way to counter the weight of a tank with a center of mass that's 5-6" from your spine. Once you're far enough outside the envelope, you go over.

I guess the test is: If you're floating still on your side - line between your shoulders perpendicular to the sea floor - is your trim balanced enough that you don't start to roll onto your back? For the diving I do most, that's the most important aspect of trim, and the hardest to achieve.

-Ben

 

[tbone1004]

dive an aluminum80 in single tank sidemount. problem solved. You can dive two tanks and just deposit one while you're digging around if you need the extra gas.

if you want to dive backmount, spread your feet apart, with the right foot position I can roll to any degree and stay there, but you have to be neutrally buoyant, you can't do it when you're planted because the wing needs to be inflated to offset the tank.

 

[RJP]

The situation is more:

You're not neutral because you wanted to stay planted...

If you're floating still on your side - line between your shoulders perpendicular to the sea floor - is your trim balanced enough that you don't start to roll onto your back? For the diving I do most, that's the most important aspect of trim, and the hardest to achieve.

If you're not neutrally buoyant, you can't very well expect to have proper trim. Especially in the case of a heavy steel tank, wherein you become negative by letting air out of your wing... which is located adjacent to the tank. With enough gas in your wing to be neutral, you are partially offsetting the weight of the tank, achieving a certain level of stability. By definition, when you dump air to become negative you will become unstable.

 

[Eric Sedletzky]

It sounds to me like you're doing Socal bug diving from what you're describing.
The plate with added weights and a big heavy steel tank to make it "balanced" may not be tbe best solution for action diving like what you want to do with the lobsters.
If you're just cruising along in trim frog kicking, maybe a drysuit, then having all your weights on your rig might work fine but you have to keep your legs apart for balance and you need to stay flat. As soon as you start wrestling with bugs or rocks or fish or whatever your no longer really considered in trim and the whole balance thing kind of goes out the window. You need to decide if you want to stay flat and upright in trim and cruise or bug hunt which is a much more dynamic style where body position can be anything. There are no real "trim" rules with a dynamic style, the whole point is to be versitile enough to twist, turn, stand on your head, get inverted,etc. to get bugs, pull scallops in cracks/ caves sometimes in oddball positions.
Most of the guys bug diving just use a plain plate with a tank and put their weight on a belt. Some guys just use a plastic pack with a tank, some use a small wing and some don't.
It sounds like you're trying to make a technical configuration work for rodeo bug diving, which may not be ideal.