An Observation On Trim

[chrpai]

I recently dove with a new buddy that has around 10 dives (OW and AOW and then stopped diving for an extended period ). We headed down to Lake Travis for some fun dives to dust off the cob webs.

We had a nice discussion on diving and gear selection ( he was curious about these BP/W's he keeps hearing about around here ) and then we headed down to the water. He was wearing a rental BCD that I think was a ScubaPro Seahawk. He had a some problem getting down at first but all in all I think his weighting was good and we didn't "fix" the problem by adding more.

I'll be honest, we were cruising along the wall and he had some pretty gnarly vertical trim / rototilling issues going on. He would trim it out sometimes and then it would go south again. The funniest was when he kind of flipped on his back, put his hands on the bottom to support himself and then started churning away. At first I thought maybe he had a cramp but then he recovered. What the heck, he was having fun, as was I, so I didn't worry about it. Total dive time was 30 minutes.

So between the dives we talked about the first dive and I mentioned to him some really dirt simple advice that had been passed down to me by 50Fathom. Arch your back, get your knees up, squeeze your arse cheeks like your holding a golf ball, hands in front locked together and head up. I told him that you might be a little sore the first time

The difference during the second dive was amazing. We didn't change his weight, we didn't move it around, we didn't switch him to a BP/W ( not you anyways...) Every time I glanced over to check on my buddy he was in a nice prone trim position gliding along without kicking up the silt. Bottom time was 48 minutes.

Now that overly long boat anchor of a console being dragged through the silt was another story but oh well, it's rental gear.

Thanks for the dives buddy. Hope to see you around again soon.

 

[Abdullah]

Ahh... The hard arch works again! I learned to dive decades ago from former special ops divers who were also sky diving buddies. They told me to do the same hard arch we used when exiting the aircraft. Worked perfectly, haven't had trim problems since.

 

[billt4sf]

I'll be honest, we were cruising along the wall and he had some pretty gnarly vertical trim / rototilling issues going on. He would trim it out sometimes and then it would go south again. The funniest was when he kind of flipped on his back, put his hands on the bottom to support himself and then started churning away. At first I thought maybe he had a cramp but then he recovered. What the heck, he was having fun, as was I, so I didn't worry about it. Total dive time was 30 minutes.

So between the dives we talked about the first dive and I mentioned to him some really dirt simple advice that had been passed down to me by 50Fathom. Arch your back, get your knees up, squeeze your arse cheeks like your holding a golf ball, hands in front locked together and head up. I told him that you might be a little sore the first time

The difference during the second dive was amazing.

Stupid question: what do you mean by "trim problem?" I think I might be having some -- when I inflate my drysuit I tend to rotate side-to-side uncontrollably and roll over.

I think your advice here might be helpful. I didn't quite understand what is meant by "get your knees up". Knees to chest? That can't be it.

Thanks,

Bill

 

[261311]

I have a small butt, I'm not sure how viable the golf ball clench will be. I imagine it shooting out and injuring the nearest thing behind me My trim is still poor, I need to get some weight in the tank band pockets to transfer some of that load forward, right now I really have to have some sort of "intentional effort" to swim downwards because my trim pushes me naturally up slowly (sad noob).

@Bill, no, knees the other way- level with or past your butt horizontally. Otherwise they participate in drag. The roll is from your drysuit inflating and the natural part of air (while buoyant) not evenly spreading out- I'll let someone else help you on fixing that because I draw blanks there.

 

[Hepcat62]

Stupid question: what do you mean by "trim problem?" I think I might be having some -- when I inflate my drysuit I tend to rotate side-to-side uncontrollably and roll over.

More like this...

Horizontal Trim 101 - Levers
Horizontal Trim 101 - Uses

One of the big reasons for rolling in a drysuit is undeveloped control over body position. Air wants to go up, and once you start (for example) rolling the air can be more than happy to help you along. Developing effective control over body position/posture underwater is a big part of REALLY getting in control of your drysuit, as it allows you to keep air where you want it (and out of the places you don't).

 

[ianr33]

I have a small butt, I'm not sure how viable the golf ball clench will be. I imagine it shooting out and injuring the nearest thing behind me

Something like this?

 

[TSandM]

You can do an enormous amount with posture. We were working with our OW students in the pool the other night, and I talked to them about making themselves "as long as possible" -- stretching the arms out in front and the legs out behind. They tried it, and reported they felt considerably more stable.

Bill, if you lie down on the floor on your stomach, and stretch your arms out in front of you, and raise your head, that's the beginning of the posture. Now raise your knees off the floor -- but don't do it by arching the small of your back. Do it by tightening your buttock muscles. The knees won't come up that much, but they will come off the floor. That's your stable platform. How much your knees are bent will be determined by your static weighting -- you put your feet and fins where they need to be to balance you fore and aft.

I still think your horizontal roll problems are likely due to a bit of overweighting, a rig that isn't adjusted properly yet, and probably some degree of variability in your posture and limb positioning. I wish you had somebody who could do some video, so we could actually SEE what is going on.

 

[alan_lee]

I agree with TSandM. How I like to describe it to my students is to "stretch out", the same sort of feeling of standing tall, the feeling of having a good posture: chest out, tummy in.

 

[CamG]

Usually a little pre-dive briefing can help many-o-problems.
This is a great example of how to work together to improve technique.
Kudos to both of you for working this trim.

CamG

 

[spectrum]

The value of posture is real and a good way to make things work in a pinch. The contortions suggested in the original post are not my idea of gun diving. Get the configuration right and relax!

Clenching a golf ball in the cheeks, give me a break.

Pete