Trim and roll issues

A question for anyone with a recommendation. After 18 months of experimenting, I'm still struggling with my tech gear in that I just can't get it to feel as stable as my good old weight-integrated jacket BC. I have a manifolded pair of LP 95s and a set of HP120s. I dive a Dive Rite harness, Classic wing, and have both an AL and a SS backplates. I dive dry suit with boots, and 7mm and 3 mm wetsuits choice driven by water temp. The problem exists somewhat with the 3mm but is more serious with the 7mm wetsuit and drysuit. Namely that it just doesn't feel as stable as my recreational setup in that I am always fighting a nose-down problem that must be fixed with ankle weights and a feeling that the entire setup wants to roll over on its back as well. No matter how much I lower the tanks in the bands (to put more weight toward hips versus shoulders), I still need ankle weights to fix the nose down tendency. Also, both setups are negatively bouyant enough that I dont require any additional weight on a weight belt even with the 7mm and the drysuit. And I don't require much inflation of the BC to maintain neutral bouyancy. While theoretically this sounds like the perfect setup in terms of overall bouancy of the entire system, I'm starting to wonder if I might be better off to add some weight via a weight belt or pockets which would then be offset by more inflation of the wing. My theory being that it might be more stable to add something heavier lower on my (horizontal) body to be offset by increased inflation in the wing above that (while horizontal) and thereby improve stability by having heavy things down and bouyant things up. As it stands, needing little inflation in the wing, I have heavy things (tanks, manifold, bands, regs) trying to balance on top of bouyant things (7mm suit/drysuit and my body/lungs). Am I on the right track? Any other ideas?

PURE speculation on my part - but hey - it's free.... I think you're on the right track.

I'm assuming you have a serious wing with more than enough lift, and hopefully a dual bladder.

I'd try an old fashioned weight belt with 4-6 pounds on the front side of your hips - depending on your rig the further outboard you can place them, the more they'll stabilize you in roll. Just make sure you can ditch it if you lose a bladder or flood your suit, so you have to put it on over your rig. I'd prefer this to some kind of harness since it would allow easy movement of the weights to trim yourself, easy ditching, and you could move it up and down your hips a bit to try to zero out the horizontal problem.

Remember your ankle weights are on a long moment arm, so you'll need more on your hips.

Let us know how it goes.

WOW, you don't require any lead even wearing a 7mm wetsuit?? That setup must be VERY negatively buoyant. Assuming you're a typical male with no hips to speak of.....guys tend to carry most of their body weight in their upper torso.....is there any way to lengthen the harness straps over the shoulders, to move the entire setup lower on your torso a bit? I'm not a tech diver, but I have physiology as a Personal Trainer.

The wing is designed for steel doubles and has plenty of lift (60lbs I think). Another idea I am toying with is getting rid of the boots on the dry suit in favor of booties and lace up on boots. The idea being that the boots hold a lot of air and may be adding to the nose down problem. With decent socks I am confident that my feet will stay plenty warm in the booties. Anyone have any opinon on that when it comes to thermal protection and bouancy issues? Also, I was also quite surprised that I don't need any weights with the 7mm suit. The first time I dove the setup, I took a guess and put 20 lbs on a weight belt. The weight check showed that it was way too much, but I didn't have time to mess with it so I dove it as it was. I must say that it was definitely more stable. What about adding weights to the bottom of the tanks. Anyone ever dong that? Hadn't thought about lengthening the chest straps. Won't that just make it loose? I have already lowered the tanks as far in the bands as possible and it's starting to get to the point of making it hard to reach the knobs on the manifold, which is a concern. Good things so far...keep em coming.

Edited by techintime, 18 August 2009 - 09:33 PM.

Weight on the tanks doesn't appeal to me - you're still going to be Top-Heavy, making your rolling moment greater - and they're not ditchable. You really don't want to carry even more weight you can't ditch.

This chart -

http://www.huronscub...cification.html

Shows 95s in the range of -8 to -10 pounds, and steel 120s from -26 down to -10 -- so with doubles, you're hauling at LEAST 20 pounds negative in tanks alone.

I've been thinking about investing in a DSS Kydex plate - although that shouldn't be more than 4 pounds lighter than SS. Although SS would lower your CG a bit more toward your center of mass, thus AL or Kydex might be a net nuisance - less weight, but more rolling moment.

You have a pool handy to check some of this out?

The HP120s are known for this problem in particular. I used to dive a set, and I found the same issues.

I solved the problem by doing a few things. I punched an extra set of holes about an inch or inch-and-a-half higher in my wing where it attaches to the tank bands. This moved the point of lift higher. I added some lead so that it was hanging from the bottom bolt on the tank band. These steps did the trick for me.

A couple of other points. If you are diving wet with such negative tanks, make sure that you have redundant lift such as a second wing, etc. Next, if you are diving dry, you should have every drop of gas possible out of the suit. Otherwise, the gas may create a bubble in your legs. The 95s are not known for causing these problems, which is why I am wondering if the gas in your suit is a main cause of what is going on.

Mark -

Where do you find tables like these? I am suitably intimidated with the technical info you spout on a regular basis - but am working to be able to do SAC calculations on the fly in my head on my way down and up (I never paid a whole lot of attention to this before, despite the number of dives I have logged...).

Although I do have a signal mirror (very scratched), I never paid a whole lot attention to the 'new generation' mirrors you presented last week. Now I am thinking "...maybe I had better start thinking about an EPIRB..."

Finally, just as I am preparing to order a couple of new tanks for SO and myself, here is a fantastic table that presents the data I have been wanting for Luxifer, Catalina, etc. tanks.

Where DO you get this stuff? (Inquiring minds want to know)

Thanks for the info -


UP Diver aka Jim

Where do you find tables like these?

Although I do have a signal mirror (very scratched), I never paid a whole lot attention to the 'new generation' mirrors you presented last week. Now I am thinking "...maybe I had better start thinking about an EPIRB..."

Where DO you get this stuff? (Inquiring minds want to know)

UP Diver aka Jim

First - thanks for the compliment - I'm not real bright, just old.... sigh ....

About mirrors - 'nuff said - best bang for the buck you can carry. EPIRB on the other hand I am conflicted about, despite the fact I own one. My motivation was some really remote dive locations I had on my list - some of which are also famous for swift currents where the next stop is New Guinea (Palau being one) - I think it's extremely conservative for most recreational divers - and it costs as much as a long weekend in Cozumel (not including ToKillYa shots)

To your question about "Where" - and "How" ?? We Divemasters are a clever bunch - it's that simple....

Seriously - I've been around water most of my adult life - no I did not join the Navy when we still had sails - but it wasn't too long afterwards. I went through YMCA certification as a kid - it took six weeks, and since my instructor was also my swim coach and lifeguard / Water safety instructor I didn't have to go through some of the swim drills... today - recreational diving is within the reach of so many with the superior gear, BCs, pressure gauges, computers etc etc etc - that you can dive safely WITHIN YOUR LIMITS without the pain of many hours in the class room and water. On the other hand, you miss the knowledge gained - mostly during surface intervals - with a patient instructor who had many years under their weight belt.

Spending ten years before the mast exposed me literally to a world of diving experiences, and navy divers were around as well. Many hours at sea gave me time to read the Navy's Divers Manual - which I still consider to be one of the best references any diver can have on their bookshelf (or on their hard drive) - and it's free from your government courtesy of your tax dollars and Supervisor of Salvage at

http://www.supsalv.o...ublications.asp - if you don't want to browse that page to find it (and you really should if you thirst for cool stuff, sites etc) here is the direct link to the doc - it's HUGE btw

http://www.supsalv.o...iveMan_rev6.pdf

This is a great board to ask questions like this - some others will treat less experienced divers with disdain.

Since I do some tech diving - not nearly as much as several on the board - I have been exposed to a lot of information. Bill (OTWDiver - aka the tank b**tch for WW) taught me a huge amount during our deco and advanced nitrox classes. Spend some time with the likes of him and you have to learn.

There is a world of knowledge on the web - google found that particular table "scuba tank buoyancy" was my query - but I knew they were out there somewhere. I have no financial interest and have little dealings with them - but there is a diverite shop with a website that I go to a lot for info and I think there is a list of good diving websites somewhere on this board. GUE has a ton of information - including very arcane stuff like how to mount various pieces of gear on your kit.

http://www.gue.com

DAN has a great website - if you're a member you can download the incident details and learn from the errors of others.

http://www.diversalertnetwork.org

There are a few others I've discovered that are very cool as well - one of my favorites is NOAA's diver site -

http://www.ndc.noaa.gov/

Last, but not least - take some courses - not to plug the agencies, but find a good instructor and you'll learn a ton even taking "card collector" courses offered by some agencies. I am a GIANT fan of the rescue course btw.

Divemaster training, IMHO, is a course that I found particularly satisfying, but I can't recommend it unless you really have the itch to be a DM, and have some notion of what you'll do with that credential. The manuals that PADI and NAUI provide for those courses are VERY good too - you might want to invest in them.

Someone help me here - but wasn't there a thread on "divers bookshelf"?

Hope this helps - see you soon I hope.

Edited by Capn Jack, 19 August 2009 - 09:08 PM.

Lot's of good info. Thanks again to all that are posting here. What frustrates me most is the huge number of variables with tech setups that one must get right to get the stability that comes out of the box with a jacket BC. I never had a single stability, trim, roll issue with my recreational BC to include tech-light diving with independent doubles on travel bands and a sling deco cylinder. It's frustrating that 18 months (perhaps better to measure it as about 20 dives) into the tech diving equipment that I'm still trying to solve basic issues that were never a problem with my recreational gear even as a basic OW student. At times I am tempted to throw the whole lot on Ebay and just go back to my recreational, independent doubles setup and just accept the goofy looks I used to get on dive boats. I am still searching for that famed benefit of the BP/Wing setup. But I ain't giving up yet and have a lot of leads from those that have commented here. Yes I have a pool to play with and I think that I am going to ban my tech gear from the ocean and concentrate on fixing this instead of muddling through with problems.

A coule of other questions I'd like to throw out for anyone to comment on:

Can anyone comment on the trim effect for a dry suit using gators, integral dry booties and lace up boots versus the integral boots to minimize the air in the legs? Replacing the boots is a drastic and expensive proposition that I don't want to do it unless I have a concrete idea that it will elliminate the need for ankle weghts.

Has anyone experimented with the roll effect of an AL backplate versus a SS backplate. While lower on the setup, it is still above the lungs, exposure suit etc. So does a heavier BP help or hinder roll issues? Capn Jack's theory is that heavier would be more roll stable. I'd like to hear the experiences of others.

Last thing, I know that every body shape is different but I'm a fairly average sized individual (5'10", 185) so I would like to hear the nitty gritty details about how anyone else of similar size is setting up their manifolded LP95s and HP120s and how they change it when diving dry versus wet. I'd much rather copy/tweak someone's recipe for success than take another 18 months experimenting till I find what works.

Continuing thanks to all

Edited by techintime, 20 August 2009 - 11:56 AM.

I myself do not have any trim and roll issues. Physically I'm 6'4" and 250 lbs. I dive dry with 130 dbls, stainless bp & wing. If have mix in my tanks and do not use them, I will use a set of smaller dbls of OTW's and still have no problems other than being slightly more on the positive side. I do not use gaters or ankle weights and do not use any additonal lead. I have never had any trim or roll problems (my luck or good instructor??). I dive with the OMS Comfort Harness even when on occasion with a single 80. Still no problems there. I use the middle holes in my wings, and the bottom holes on my harness/bp. This puts the wing just over the shoulder of my dbl 130's. On valve drills, i have to loosen my waist strip a little so I can reach my valves but that's not a problem. So even with stage bottles (4) dbl 130's, or down to just dbls, I love my wing/bp set up. Dont give up experimenting with your set up. Everyone is different physically and what works for one, maybe close you what you need. Make minor adjustments and keep trying them out until you are zeroed in. That is part of being a "tech diver". Dive with experienced divers, learn from them, keep an open mind, notice their set up and do not be afraid of asking questions.

As for boots, I have a Moby and a Dui suit. Moby has built in boots, Dui has the rock boots w/laces. I'm ok with either. Moby is an older suit that I use on occasion with county rescue. Dui is my "tech" suit. On either one, use only enough air to prevent squeeze. You may also give it a shot of air to trim out. I do not use my drysuit as a bc.

SS vs AL bp: I have ss which weighs in at about 6 lbs. Never used AL. I have a friend that has a titanium bp. Lighter than both. He wore his tanks so high, he just reached back and did valve shut downs. Heavier up top is going to mean more air in your wings to compensate from putting your face into the silt. As said before, time & patience will get you there.

Get used to making adjustments to your equipment. It is part of tech diving. There is always something new to try to make your diving even better.

Since you mentioned the drysuit issues: Some people have stock suits that fit well. Others have to go with custom suits. These can get to be very expensive, e.g., over $3,000 (yes, really!). Proper fitting suits will help to keep baggy suit legs from happening. Some people use the gators as a much less expensive alternative.

Lots of things can combine together to create trim issues: tank type (such as the HP120), drysuit issues, excess suit gas, diver form, etc. Just keep working at it. It is a never ending thing that can become extremely satisfying once you get dialed in.

Has anyone experimented with the roll effect of an AL backplate versus a SS backplate. While lower on the setup, it is still above the lungs, exposure suit etc. So does a heavier BP help or hinder roll issues? Capn Jack's theory is that heavier would be more roll stable. I'd like to hear the experiences of others.

Just to clarify. Heavy is related to greater effect in shifting your Center of Gravity down from way off your body's geographical center. It relates to roll in the sense that moving your CG closer to your center reduces the moment arm of the weight that is creating the roll instability.

One observation too - as you advance in diving, especially tech with a continual focus on drills in the water column, you become more and more tuned in to your body position and motion in the water. Thus you are more aware of small trim issues that other divers are not noticing. I've read many posts here from some of our tech gurus expressing their frustrations over some of the same minutiae.

Might be like those who enjoy the frustrations of golf. For the record, I keep score in terms of number of balls lost per round.

Edited by Capn Jack, 21 August 2009 - 06:28 AM.

Might be like those who enjoy the frustrations of golf. For the record, I keep score in terms of number of balls lost per round.

Ha Ha.... I like your scoring method! I don't worry much about my score, as I figure the more times you get to hit the ball, the better value on your green's fee.

Might be like those who enjoy the frustrations of golf. For the record, I keep score in terms of number of balls lost per round.

Ha Ha.... I like your scoring method! I don't worry much about my score, as I figure the more times you get to hit the ball, the better value on your green's fee.

yep - I'll put my cost per shot against anyone - there's something we can try on our no-dive day at the end of the trip.

Edited by Capn Jack, 21 August 2009 - 08:53 PM.

Might be like those who enjoy the frustrations of golf. For the record, I keep score in terms of number of balls lost per round.

Ha Ha.... I like your scoring method! I don't worry much about my score, as I figure the more times you get to hit the ball, the better value on your green's fee.

yep - I'll put my cost per shot against anyone - there's something we can try on our no-dive day at the end of the trip.

So does this mean you are in???