Getting trim right

Sorry if this is a topic discussed before but the word "Trim" pops up in different threads so often that the results from search are too numerous to be usefull.

If somebody can point me to proper threads i will be gratefull

SO, my question is: what to do to be trimmed right ? Where to put the weights? how?

I dive with Halcyon SS backplate, #36 wing, 80 or 100 alu tanks, no canister light, weight belt and two piece 6 mm (3+3/3 mm) wetsuit and hood.

In fresh water (springs) i put just 2 lb on the weight belt and i am trimmed pretty horizontally in the water. but if i add anything more than that (say, for ocean diving) i end up basically vertical in the water no matter how much air i put in the wing. (the two 2lbs came from experimenting with weights in the water. i think that i might have a problem going down with "dry" wetsuit...)

I was set to put weights ont eh top of the tank in weight pounches to get the trim right but then i've talked to a cave diver instructor who told me that putting weights on a tank is a bad idea and i should basically shoot at overweighting myself a little and then compensating with the air in a wing which should pull my behind up. .. err.. i don't see how that should work because if i put more wieghts on the belt i end up more vertical in the water no matter how much air is int he wing...

So basically i am confused now

I tried getting in a pool and checking all different ammounts of the weights with 500 psi in a tank at 10 feet of depth (bottom of the pool) and that wasn't really conclusive since with fresh water (pool) the stainless steel backplate and 2lb of weight is basically all i need to stay down (does that sound logical ? it doesn't for me :-/, i would think that with two piece wetsuit i would need more weight!?!?)

experiments with putting weights on tankbands didn't end up too well because then i had a tendency to roll on my back .. really annoying.

then there is also an idea with weighted STA .. but then that would put me pretty much overweighted all the time i dive int eh springs (see the "i need only 2lb to stay down comment)

Of course, it is pretty obvious that in my Open water and advanced open water classes the issue of trim never came up and proper weighting was really skipped over. (sigh)

finally.. this is really a hit and miss issue.. sometimes i think i've got it right and get trimmed really nicelly only to go diving next time and have big troubles with exact the same config !

help !

Arch your back... don't drop your knees... get your feet up by bending at the knees.

Once horizontal tip your head down far enough to look between your legs directly behind you... what happens? Do you tip over onto your head? If so you are head heavy (not foot heavy) and have been compensating by dropping your knees.

Report back.

Like Matt I was not taught trim in my OW class I do understand some of the concept but I have never figured out what arching your back has to do with trim. Please explain why this is important for good trim.

FallenMatt once bubbled...
Sorry if this is a topic discussed before but the word "Trim" pops up in different threads so often that the results from search are too numerous to be usefull.

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help !

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I gather when you said vertical you meant vertical with feet heavy, right?

You could try rigging the entire set so that it rides a little higher on your back. Even a couple of cm might make a difference. Watch out that you don't get the valves so high that they interfere with head movement (especially looking up).

Also, what kind of fins do you wear? If you took the DIR route and are wearing jetfins then you might want to try something a little lighter. IN my experience, jetfins don't work very well in combinatoin with a wetsuit. Too heavy....

I'd say overweighting is going to amplify your problems so I'd look into that option as a last resort. As far as I know, overweighting can help if your feet are floaty but not if your feet are heavy. At any rate it's likely to create as many problems as it solves. At best it will just make your situation more complex and with all due respect to your friend I wonder what would motivate someone to advise against putting weight on the tanks and then suggest this....

About weights on the tank. I think you still have some better options. I see you're using AL tanks. Have you tried steel? That will give you all the weight you need between your shoulders. In fact, going to steel tanks might solve the problem entirely....

R..

Personally I'm still playing with my weighting and trim but, from my experience, moving the tank up or down a couple of inches in the cam bands, can make it considerably easier to get horizontal..

Also as UP pointys out, it's surprisingly difficult to tell if your foot heavy or head heavy and overcompensating.

There is so much talk about trim weights and positioning that body position is often ignored entirely. Changing the angle of your knees will shift your CoG enough to adjust your trim, especially when wearing jets. If you are foot heavy you may not have them bent enough. Ideally your knees should be at about a 90 degree angle. I would bet that you could fix your trim by bringing your feet up.

When diving singles with a Pioneer 27, 3mil, and a 5mil vest I trim out evenly without any additional weights. When I add a cannister light (3lb) to my waist it makes no difference to my trim; the adjustment is all done through body position. With doubles and a drysuit carrying two stages makes me head heavy, but rather than strapping lead to my ankles to fix it I use my legs and back to trim out. That's not to say that you should dive an unstable rig and rely entirely on this, but that you have a significant range of adjustment available to you. I would say that two pounds is not at all a problem to trim out like this, but five or so and up might be. If you need to fin to maintain trim it is not stable enough to do this.

Once you get something that works for you, however you do it, practice pivoting around your CoG. Bend your knees all the way. You should roll forward. Extend them straight out. You should go head up. This really helps to get a feel for things.

Keep your back arched. That, like UP said, is what keeps your knees up and your body flat, and is essential for perfect trim at all times. If you can't feel it, you're not doing it.

hmm it will take minimum one more week before i go diving again.. unless i decide for a quick run to blue springs mid week (and the heavy outflow of that spring is too much for trying to get trimmed right) ..

yes, how does arching back help trim ? i mean it in a way "what's the mechanism" of it ?

I use tusa liberator X fins.. they are actually slightly positivelly bouyant in the water...

steels would be a nice thing but the price tag attached to them is too high right now. I have pretty unlimited access to standard 80;s (club gear) so it is hard to justify buying new tanks for myself.

now when i am thinking about it i might be doing it the wrong way around.. seeing that with light fins and bunch of weight up front i still go vertical.

gotta work on it some more i wish i just had it done right the first time - ie. instructor that takes time in the water to teach it right.

FallenMatt once bubbled...
yes, how does arching back help trim ? i mean it in a way "what's the mechanism" of it ?

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Matt, I seriously doubt that you are foot heavy.... I think you are head heavy and compensating.

That said, to answer your question, arching your back is meant to over correct what is really happening so that you can see the difference. You are most likely dropping your knees. By getting you to arch your back (slightly) hopefully your knees will come up.

After that you can adjust.

FallenMatt,

UP may very well be right. If you are head heavy you may compensate by tipping back to become stable. However, if you do need weight higher up and add it to the cam bands, slide it up close to the wing so it's close to your back. As you improve body position you may need to adjust weighting. It's hard to figure without seeing you in the water.

I have a grommet maker and SS grommets.I have new holes in some bladders that place the wing lower on the B/P.Adjusting the tank or tanks up/down on the straps/bands can also effect trim.