How high in my back should the wing and tank be?

[mmarchadesch]

@mattboy, tortuga: Thanks again
Anyways, I gave my BP/wing setup a good look. Turns out, my harness wasn't weaved properly. My right shoulder strap was riding an inch and a half higher than the left. The D rings were also low and in my armpit - thus the pinch in my upper inner arms. I re-did the harness and I hope this helps with the trim problem.

I'll see how it goes in my next outing. Thanks again...

Mario

 

[Tortuga68]

You're welcome

Re: chest d-rings, as a general rule, your fingertips should hit them when you 1. stretch your arms out to either side and bend your elbows inward and 2. when stretch them straight down and bend your elbows upward, when standing

Or in other words, they should be an inch or so below the front of your collar bone, on an average person

 

[Doc Harry]

Hello mmarchadesch,

Without actually diving with you, we can only speculate as to the cause of your problems.

Your weight may be fine without switching to an aluminum backplate. Are you too heavy? Doesn't sound like it. If you want to know for sure, check your weight in a shallow area (15 feet) with 500 PSI in your tank.

You should position your tank/wing high enough that you can reach the valve. As it is not possible to "fine tune" your trim with tank positioning, so just get the valve within reach and leave it there.

I say it is not possible to "fine tune" your trim with a tank because the tank buoyancy characteristic is constantly changing as you consume gas. This is especially true with an aluminum 80. It's "negatively buoyant" at the start of the dive, so it tends to push your head down. Later the tank becomes "positively buoyant" as gas is consumed, so it tends to pull your head up. Thus trying to find a "sweet spot" for the tank position for trim purposes is pointless and frustrating.

It does sound like you are "turtling," or flipping over due to the weight of your tank. The solution to this problem is body positioning and practice. Major equipment or configuration changes are not generally necessary.

You can expect a tendency to turtle early in your dive when your tank is full. You can counter this tendency by keeping your legs widely spaced to stabilize yourself. As other have mentioning, in the short term you can switch to an aluminum back plate and put 4 pounds on a weight belt. But long term you can and should work through it and get back to the steel BP without a belt.

The solutions you seek should be in your technique not your equipment.

Good luck.

 

[Tortuga68]

I say it is not possible to "fine tune" your trim with a tank because the tank buoyancy characteristic is constantly changing as you consume gas. This is especially true with an aluminum 80. It's "negatively buoyant" at the start of the dive, so it tends to push your head down. Later the tank becomes "positively buoyant" as gas is consumed, so it tends to pull your head up. Thus trying to find a "sweet spot" for the tank position for trim purposes is pointless and frustrating.

Adjusting tank position is only one component of achieving correct horizontal trim

While it's true that tank buoyancy changes during the dive, I don't agree with your implication. If you have the tank positioned correctly and your trim weighting right, you shouldn't get the head up/head down variation that you describe; if you have your horizontal trim right to start with, it should be consistent regardless of tank volume

 

[Doc Harry]

Adjusting tank position is only one component of achieving correct horizontal trim

While it's true that tank buoyancy changes during the dive, I don't agree with your implication. If you have the tank positioned correctly and your trim weighting right, you shouldn't get the head up/head down variation that you describe; if you have your horizontal trim right to start with, it should be consistent regardless of tank volume

You can't agree or disagree with the laws of gravity and buoyancy. The laws exist whether or not we chose to acknowledge them.

 

[halocline]

Actually I don't think an AL tank pushes me "head up" when it's empty. It's the bottom of the tank that is most buoyant. The valve and attached reg add weight at the top, and the contour of the neck makes the top less buoyant. Plus, in my case, that AL80 is attached to a steel plate, which is located near the top of the tank.

I've dove with steel and AL tanks, and to me the buoyancy swing is the pretty much same in both. If anything, if I'm light with the AL tank, I tend to go feet up towards the end of the dive.

As a general rule of thumb (with lots of exceptions) a steel plate works well with AL tanks and vice versa for warm water for a reasonably lean diver. In cold water, or with divers that need 15-20lbs in warm water, the steel plate might be more useful with any tank.

 

[Diver0001]

Greetings Scubaboard listers!

I'm Mario - from the Philippines. I'm glad to have stumbled into this forum, its been very

I'd have to see you in the water to really stand a chance of correcting this but here's a short list of things to try.

1) Move the weight off of the cam band and put it on a weightbelt. The weight on the weight belt needs to be slightly toward the FRONT of your pelvis and not on the side or behind. If you can't find 1lb weights then you'll need to put 2x 2lb weights, one on each side symmetrically.

2) The problem with aluminium tanks is that they'll tend to float your feet up as they get empty. To compensate for this (find the sweet spot) just adjust the backplate as shown on the link to the DIR site in post #6 and then try different locations for the wing. The wing usually has three possible positions which will put the whole wing higher or lower on the backplate. Try it in the middle position first. If that doesn't feel right then move it to the other positions and try again.

As for the position of the tank, as you're playing with this try to keep it set in one position and move one thing at a time. There are ways to add a keel weight to the tank too but try it without first because usually even a small weight attached to the tank will push your feet too far down.

3) I can't advise you about whether or not you need a steel or AL plate but using an AL plate will allow you to put more weight on your weightbelt which, given the problem you're describing, may help to keep you more stable in the water. You're not using much weight as it is, so just adding another 2lb and moving all your weight to the weightbelt may very well sort you out.

hope that gives you some useful ideas.

R..

 

[mmarchadesch]

@doc harry, Diver0001:

thanks for the inputs. I think I'll have to carefully take note how my attitude is in water. What my "problem" is at specific times in the dive. What a full or empty tank does to my swim trim, etc.

Too heavy, I don't think so, too. If I remember correctly, I can float with my head at about eye level when tank near empty with no air in wing - but I'll have to verify that next IN WATER time

I do remember that I get this anxious feeling that I'm overinflated coz my butt rises and therefore I deflate using the rear exhaust and attempt to right myself. I'm not sure when this happens, though, on a full or half full tank. I'll make a note of this too.

Thanks again for sharing your takes.

Mario

 

[Tortuga68]

You can't agree or disagree with the laws of gravity and buoyancy. The laws exist whether or not we chose to acknowledge them.

I disagreed with your implication of how the laws applied, not the laws themselves

I'd greatly appreciate if you would share your experience with me and further my understanding of how the laws work in practice

 

[mmarchadesch]

Greetings to all and a belated happy new year.

Well, I was able to put in 2 dives this weekend, and although I felt a bit more "trimmed" with a properly woven harness, I wasn't able to give it much of a test.

Here are a few of what I did notice:
1. I did not experience the turn turtle feeling. I did apply a wider feet stance, also extending it at the knee just a bit. I also used my heavier jetfins. Could this have helped?
2. I still had the bottom of the tank lifting at about the end of the dive - during the 1st dive - thus decided to add weight in a belt. 2lbs on each side in front of the pelvis, and this really helped the tail lifting! Of course, I was over weighted. I really needed extra air in the wing at the surface, but not in the water. I did not feel the extra weight but instead felt a lot more stable. I guess I'll be adding just 2lbs total in a belt.

BTW, is it possible to shave a bit off my stainless steel single tank adapter without weakening it too much?

Thanks again to all!!! I can't wait to get back in the water again....