Drysuit trim

[wrybosome]

Hi all,

I started diving dry this year and am having trouble with keeping trim. I tend to go head down. Not a runaway air in the feet heading to the surface scenario, just light and floaty feet putting me firmly head down. My gear is:

Bare HD suit
4th El arctic undies
steel bp/w
single LP95
14 lbs lead on belt
2 lbs lead on ankles

Anyone have any advice on correcting this? I'm trying to add only just enough air to offset squeeze, ie I keep the suit so I feel just slightly squeezed all over. The boots are somewhat large on my feet.

 

[tbone1004]

That's an AWFUL lot of weight dude... that's 26 ish lbs... that's more than we put our students in with AL80's, jackets and 7mm farmer johns... You need to shed some SERIOUS weight off of that and reevaluate first.
LP95's are notoriously head heavy, so that's some of the problem. I'd try gaiters, they help a fair bit with that.
You SHOULD be able to shed enough weight to get down to about 6lbs on a belt and nothing else

 

[HenrikBP]

You SHOULD be able to shed enough weight to get down to about 6lbs on a belt and nothing else

That depends ...

In my Fusion drysuit with Arctic undies, 7 mil hood and Hollis F1 fins (no other gear) it takes me about 24 lbs to get slightly negatively buoyant. To "get there" in my AL80 doubles rig I have a 6 lbs steel BP, 11 lbs V-weight, 5 lbs tail weight, a 3 lbs "sausage" weight plus can light, back-up lights and probably a good pound of bolt snaps

Henrik

 

[ScubaSteve]

Tim, how far up is your tank? Are you able to slide it down any?

What happens when you stand up, vent air from your suit and then get into trim again so that your boots do not fill up? Knees bent and slightly head up in trim should prevent excess air from forming in your feet. If you feel a floaty moment, stand up, vent a bit and correct your trim. Don't worry about how much weight you are carrying right now. Worry about placement. Are you able to attach a couple pounds to the bottom of your plate? If the boots are too big then correcting that should help somewhat.

Are you able to try a lighter undergarment on your feet and legs without freezing yourself?

 

[TSandM]

Maybe I'm math-challenged, but I'm coming up with 21 lbs of ballast, which seems quite reasonable if he is using 4th Element Arctics. I use 10 lbs MORE than that with my LP 95s and my White's MK3.

Trim starts with body posture. Do you hang your head? That will tend to make you tip head down. If your head is up and your body is flat, then which way you tip will be totally dependent on the buoyancy of the various parts of you and your gear. What kind of fins are you using? A lot of dry suit divers like Jet fins, because they are negative. You have ankle weights on -- how much do you bend your knees? If your knees are very bent and your feet are close to your behind, those ankle weights don't have much of a lever arm to help balance you.

Another thing to look at is where you have the gas in your dry suit parked. I like to keep most of mine up around my shoulders. If I get much gas in my feet, I drop them and move the bubble upwards (except when I'm scootering -- then gas in the feet is great).

Another thing you can play with is using your wing more. Most of your negative stuff is on your back -- tank and backplate -- so putting the lift right where that stuff is might help as well. This might be a case where just lofting the undergarment, and putting the rest of the compensation gas in the wing might work better.

Play with some of this and come back and let us know how it worked. If you can get someone to video you, that will help a lot, too.

 

[wrybosome]

That's an AWFUL lot of weight dude <SNIP>
You SHOULD be able to shed enough weight to get down to about 6lbs on a belt and nothing else

It's the weight that it took to sink me with an empty tank, a vented suit, and an empty wing. You are using 6# on your belt plus a BP and single tank?

In my Fusion drysuit with Arctic undies, 7 mil hood and Hollis F1 fins (no other gear) it takes me about 24 lbs to get slightly negatively buoyant.

I already knew I was denser than you Henrik . I'm using F1s too. Thanks for your weight estimates.

Tim, how far up is your tank? Are you able to slide it down any? It's at lowest wearable location, ie the upper strap is right at the tank shoulder.

What happens when you stand up, vent air from your suit and then get into trim again so that your boots do not fill up?
I lose most of the floaty sensation but am still in definite head down trim. This seems to shift the air back to the boots before long unless there's really no loose air.

Don't worry about how much weight you are carrying right now. Worry about placement. Are you able to attach a couple pounds to the bottom of your plate?
I'm wearing the weight in some droppable DR pouches which mount on the hip belt. Not sure if moving them to the plate bottom would shift my CG, but I'll take a look at it. Maybe my whole rig sits high and I can move it down my back an inch or two.

If the boots are too big then correcting that should help somewhat.
The suit has integrated hard boots. I'm going to make some heel inserts to take up 3/4" or so. If that doesn't help I'll consider having different boots mounted.

Are you able to try a lighter undergarment on your feet and legs without freezing yourself?
Probably!

Maybe I'm math-challenged, but I'm coming up with 21 lbs of ballast, which seems quite reasonable if he is using 4th Element Arctics. I use 10 lbs MORE than that with my LP 95s and my White's MK3.
I thought my weighting was appropriate. On the surface with 800 psi I'm just negative with the bc empty.

Trim starts with body posture. Do you hang your head?
No, it's craned up to see forward.
That will tend to make you tip head down. If your head is up and your body is flat, then which way you tip will be totally dependent on the buoyancy of the various parts of you and your gear. What kind of fins are you using? A lot of dry suit divers like Jet fins, because they are negative. You have ankle weights on -- how much do you bend your knees? If your knees are very bent and your feet are close to your behind, those ankle weights don't have much of a lever arm to help balance you.
Hollis F1s, and the knees are bent about ~90°. With the head down trim this probably puts my feet well above my head.

Another thing to look at is where you have the gas in your dry suit parked. I like to keep most of mine up around my shoulders. If I get much gas in my feet, I drop them and move the bubble upwards (except when I'm scootering -- then gas in the feet is great).
Still learning to feel this, but not there yet. I'm trying to be very minimal with the amount of gas in my suit so it always feels more like a bit of squeeze than a bubble of gas.

Another thing you can play with is using your wing more. Most of your negative stuff is on your back -- tank and backplate -- so putting the lift right where that stuff is might help as well. This might be a case where just lofting the undergarment, and putting the rest of the compensation gas in the wing might work better.
I'm using the wing for buoyancy and just adding enough suit gas to remove most of the squeeze. So if I read you correctly I am doing what you suggest here.

Play with some of this and come back and let us know how it worked. If you can get someone to video you, that will help a lot, too. I will, thank you.

Thanks everyone! Food for thought.

 

[tbone1004]

I dive two HP120's and a nomad, so no crossbar/bands and no hard plates and I sink like a brick in my drysuit. I know i'm really dense, but that still seems like a lot to me.
I don't really don't know how else to help you if you're head down like that though. I think if you could put some of the weight farther down on the plate that may help. If you can't reach the valves the tank still has to scoot up until you can reach it though. That trumps trim.

What wing are you using out of curiosity?
I know some people that use the DR Venture wings or other similar shaped wings that have more lift in the hips than the top which will make you flip over. If I'm diving wet with doubles on my Nomad I'm constantly fighting the urge to flip because all the lift is at my hips.

 

[HenrikBP]

I'd start with plate/tank position. See if you can shift it lower while still being able to reach your valves. Do this a little at a time by loosening your shoulder straps maybe an inch or less at a time. Shifting that heavy steel tank might be enough ...?

Henrik

 

[wrybosome]

What wing are you using out of curiosity?
I know some people that use the DR Venture wings or other similar shaped wings that have more lift in the hips than the top which will make you flip over. If I'm diving wet with doubles on my Nomad I'm constantly fighting the urge to flip because all the lift is at my hips.

It's a DSS torus 26, pretty symmetrical profile with regard to hips and shoulder. I'll recheck my weighting as well in case I'm wrong and can get away with less. I was wrong once before.

I'd start with plate/tank position. See if you can shift it lower while still being able to reach your valves. Do this a little at a time by loosening your shoulder straps maybe an inch or less at a time. Shifting that heavy steel tank might be enough ...?

Henrik

Yeah, think I'll start with that. And see if I can shift the other lead lower.

 

[tbone1004]

Make sure the suit is fully burped when you do it...

You may also be able to weave a 4lb weight on the crotch strap. I've seen people do that before with good results