Best way to work on trim - feet sinking

[mruseless]

There are a lot of divers who are fin heavy when diving wet. I'm one of them. I can get really close by putting my tank up high and putting weight in the cam band pockets. But I can't get perfectly still and horizontal without a drysuit. But for recreational warm water diving, close to "still and horizontal" is still way better than most!

 

[Michael Guerrero]

There are a lot of divers who are fin heavy when diving wet. I'm one of them. I can get really close by putting my tank up high and putting weight in the cam band pockets. But I can't get perfectly still and horizontal without a drysuit. But for recreational warm water diving, close to "still and horizontal" is still way better than most!

Put weight on your shoulders. You will be horizontal. Your lungs are a fulcrum. Balance both sides and you're good.

---------- Post added November 19th, 2013 at 07:02 PM ----------

Trim is a function of the relative locations of the diver's center of lift (the point around which all those pieces and parts of the diver's body and rig that are positively buoyant are balanced) and the diver's center of weight (the point around which all those pieces and parts of the diver's body and rig that are negatively buoyant are balanced). Of course those points are dynamic - they move a little as the diver breathes, adds or removes gas from the BC or dry suit or counterlung, shifts gas in the dry suit (and even the BC - some are worse than others), uses gas from the tank(s), and with wet suit compression changes with depth.
If we can arrange things so that the center of lift and the center of weight are co-located, all is lovely, and we can remain in any position we desire without effort - pitch and roll forces will be non-existent no matter what position we choose, and remaining there is effortless.
However... getting those points together is seldom possible, and adjusting trim to make position maintenance easy can be very frustrating, even counter intuitive.
The first step to take in the trim adjustment process is to discover what the relative positions of these centers of weight and lift really are:
- establish neutral buoyancy, where able to control depth precisely with just breathing.
- while maintaining a constant depth, lock arms in position with hands together, and lock legs in position with feet crossed. DO NOT KICK or SKULL.
- WAIT - (yeah, it's a real PITA and very un-natural) - DON'T MOVE - until your position stabilizes in both pitch and roll. Where you end up may surprise you, especially if you're wearing (a) steel tank(s).
The position in which the body stabilizes will be with the center of lift directly above the center of weight, and now adjustments to the rig to improve trim can be made that make sense.
There are essentially two positions: on your belly or on your back. What to do depends on this "final position" and goes something like this...
If on your belly, then when in the prone position the center of lift is higher than the center of weight, and all the recommendations folks have made so far will make sense - to get the center of weight directly below the center of lift in the desired prone position is achieved by adding or shifting negatively buoyant stuff (like weights) towards the high end/side and/or shifting a positively buoyant item toward the low end until that balance is reached... the center of lift is directly above the center of weight when prone. This is a stable arrangement - any displacement from that position will naturally swing back toward it.
--
BUT, if the diver's stable position is somewhere on the back, we have an entirely different kettle of fish!
In this case, when prone, the center of lift is lower than the center of weight, and the trimmed out position will be where that center of lift is directly below the center of weight. This is both unstable (any displacement will continue to roll or pitch in the displaced direction until the diver has arrived at the lift-above-weight position), and staying in the trimmed position requires the diver to apply constant little balancing forces with fins - or, gasp!,hands - to keep the weight from "falling off the bubble" and adjustments to the trimmed position are precisely backwards from what seems right - that is, since the trimmed position is weight-directly-above-lift, if your feet are low then it's because your center of weight is too far forward you must add or shift weight to your feet to get your feet up to the desired trimmed position.
And so forth...
Y'all have fun now, ye hear?

Rick

OMG Rick. I think my head just exploded.

OP, imagine a seesaw. You need to balance both sides. That's about it. Rick is absolutely right that the circumstances are dynamic and gas consumption and suit compression (wet) affect the outcome. But, you can get close enough that these issues are easily managed.

And yes, balance (in the GUE sense) can be challenging to achieve depending on exposure suit and environment, but a close approximation with a rig you can swim up is better than staying foot heavy. If part of your enjoyment of diving is doing it correctly (and I'd argue overall horizontal, streamlined trim, regardless of momentary changes due to looking up or turning sideways, etc., is correct) then get your fulcrum balanced. That's a combination of the wing and lungs (wet). And if dry, it's largely affected by the drysuit (big bubble), and IMO easier to achieve by managing the bubble to overcome fulcrum management.

And...exhale...

---------- Post added November 19th, 2013 at 07:10 PM ----------

AND...this says nothing about roll. Trim (pitch) is one axis. Roll (turning turtle left or right) is another. And you must be balanced on this axis as well.

 

[SanDiegoSidemount]

I was in your exact situation: I had F1 fins that were just too heavy, combined with my heavy legs. I struggled with my trim for a long time, using all the techniques already described in this thread.

I think the other posters who say you can overcome this with shoulder weighting and body position haven't actually experienced the problem. At least not at the level I was experiencing.

After a certain point, the "lever arm" of heavy feet is just too long to adequately compensate for with shoulder/tank band weights. Sure, you can use body position, butt clench and back arching along with shoulder weights to end up with what likes good trim to observers (like your instructor). But it's exhausting to hold in position. It just shouldn't be that hard.

Then I tried lighter fins -- the UTD Neutral Fins -- and instantly my trim was fixed. Almost like magic: no struggling, no exaggerated butt flexing or back arching, it just worked. My feet floated up, and I was right in trim.

I wish someone had given me the fin recommendation earlier. It would have saved me weeks of discomfort trying to dive in trim with fins that were just too heavy for me.

Another benefit of the UTD fins is that their design -- short, wide and stiff -- makes for amazingly powerful frog kicking.

 

[Michael Guerrero]

I was in your exact situation: I had F1 fins that were just too heavy, combined with my heavy legs. I struggled with my trim for a long time, using all the techniques already described in this thread.

I think the other posters who say you can overcome this with shoulder weighting and body position haven't actually experienced the problem. At least not at the level I was experiencing.

After a certain point, the "lever arm" of heavy feet is just too long to adequately compensate for with shoulder/tank band weights. Sure, you can use body position, butt clench and back arching along with shoulder weights to end up with what likes good trim to observers (like your instructor). But it's exhausting to hold in position. It just shouldn't be that hard.

Then I tried lighter fins -- the UTD Neutral Fins -- and instantly my trim was fixed. Almost like magic: no struggling, no exaggerated butt flexing or back arching, it just worked. My feet floated up, and I was right in trim.

I wish someone had given me the fin recommendation earlier. It would have saved me weeks of discomfort trying to dive in trim with fins that were just too heavy for me.

Another benefit of the UTD fins is that their design -- short, wide and stiff -- makes for amazingly powerful frog kicking.

+1. Balance the fulcrum. That doesn't always mean adding weight.

 

[Dive-aholic]

The easiest, although probably not the cheapest, solution is to get lighter fins. If you like the F1 shape you should try OMS Slipstreams. If you just want lighter fins that will give you power in your kicks then I recommend the SEAC GP100 4x4s.

 

[mruseless]

I was in your exact situation: I had F1 fins that were just too heavy, combined with my heavy legs. I struggled with my trim for a long time, using all the techniques already described in this thread.

I think the other posters who say you can overcome this with shoulder weighting and body position haven't actually experienced the problem. At least not at the level I was experiencing.

After a certain point, the "lever arm" of heavy feet is just too long to adequately compensate for with shoulder/tank band weights. Sure, you can use body position, butt clench and back arching along with shoulder weights to end up with what likes good trim to observers (like your instructor). But it's exhausting to hold in position. It just shouldn't be that hard.

Then I tried lighter fins -- the UTD Neutral Fins -- and instantly my trim was fixed. Almost like magic: no struggling, no exaggerated butt flexing or back arching, it just worked. My feet floated up, and I was right in trim.

I wish someone had given me the fin recommendation earlier. It would have saved me weeks of discomfort trying to dive in trim with fins that were just too heavy for me.

Another benefit of the UTD fins is that their design -- short, wide and stiff -- makes for amazingly powerful frog kicking.

Great tip! I've tried several different fins, but haven't found any neutral fins I liked. I didn't know UTD sold fins, I'm gonna have to try them!

 

[TSandM]

I actually think one of the reasons (not often mentioned) for why backplate and wing setups make people feel so stable, is that as the pontoons of the wing lift with air, they are right beside the tank -- that minimizes the turtling tendency (stabilizes on the roll axis). So backplate users will rarely end up on their backs at the end of that exercise, unless they are wildly out of balance on the pitch axis, to the point where they end up vertical and the tanks takes them over backwards.

 

[Michael Guerrero]

I actually think one of the reasons (not often mentioned) for why backplate and wing setups make people feel so stable, is that as the pontoons of the wing lift with air, they are right beside the tank -- that minimizes the turtling tendency (stabilizes on the roll axis). So backplate users will rarely end up on their backs at the end of that exercise, unless they are wildly out of balance on the pitch axis, to the point where they end up vertical and the tanks takes them over backwards.

Definitely. And if the plate is SS, more weight around the fulcrum while capitalizing on the pontoon effect.

My doubles seem to want to roll if I'm too aggressive with my rolls, but maybe I need to use my wider (8") HOG wing instead of my (7.25") EXD wing.

 

[SanDiegoSidemount]

I actually think one of the reasons (not often mentioned) for why backplate and wing setups make people feel so stable, is that as the pontoons of the wing lift with air, they are right beside the tank -- that minimizes the turtling tendency (stabilizes on the roll axis). So backplate users will rarely end up on their backs at the end of that exercise, unless they are wildly out of balance on the pitch axis, to the point where they end up vertical and the tanks takes them over backwards.

Indeed. This is especially true of newer wing designs that are made for single-tank, are relatively low lift (25-35lb), and are cut to stay very close and tight (as opposed to old-school "taco" wings). I love my Dive Rite Voyager: it barely extends past the edge of the backplate when it's inflated.

 

[Rick Murchison]

The easiest, although probably not the cheapest, solution is to get lighter fins. If you like the F1 shape you should try OMS Slipstreams. If you just want lighter fins that will give you power in your kicks then I recommend the SEAC GP100 4x4s.

Of course, Rob, you know the easiest way to achieve rock solid indisplaceable perfect trim... just sidemount a couple of 104's!

Rick