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<font color='#0000FF'>Hello all,

Last weekend I was doing one of the last 2 dives to complete the Adv. trimix course. The plan was 70m 20min using 17/38 bottom gas and 32% and 60%. We planned the dive at Reqqa a shore dive in Gozo. Here you jump and find bottom to 30m, after some finning you are at 50m with a drop to 70m, where bottom will slide slowly down for more that 110m.
This summer I had been playing with by trim and trying to remove as much lead as possible.I fist started to dive with twin 12's and 2 10l stages (all steel) and 4kgs lead. Then I started to remove some lead and each time hang a spare weight on deco station. So I started to dive with twinset and if I use only one stage I use a 2kg on ther side to balance. On this dive I decided not to use any weight as I had enough weight to sink but just in case I put a 2kg weight with deco stage and spare stage.
As we jumped the sea was a little bit rough, but not doable. So we decende and could feel my trim not perefect, I was all the time going head down and feet up (I use a wet suit which is more than enough for 14'c bottom and 25'c surface). Off we went to 70m, trim was so and so but better than at surface. There was a strange feeling, your experience is telling you your gauge is fauly, how can it be that you are at 70m no narcosis and breathing so easy (who have done a 70m air dive will understand what I mean, although now I can say it was really crazy) The ascend started and everyhting was ok doing deep stops and time was passing by. But when we reached to 9m stop I was very light with no air in my wing and the sea worst than before. We were going up and down me more than others, at 6m I clipped the weight but problem was not sorted so I had to fight the wave action and my trim for 30min.
Depth1=  30msw:   3mins 32%O2  0%He  Run Time=  3mins
 Depth2=  70msw:  17mins 17%O2 38%He  Run Time= 20mins

  DIVE 1 DECOMPRESSION REQUIREMENTS      
   Stop=  46msw:   1mins 17%O2 38%He  Run Time= 23mins
   Stop=  35msw:   1mins 32%O2  0%He  Run Time= 26mins
   Stop=  24msw:   1mins 32%O2  0%He  Run Time= 28mins
   Stop=  21msw:   1mins 32%O2  0%He  Run Time= 29mins
   Stop=  18msw:   1mins 32%O2  0%He  Run Time= 30mins
   Stop=  15msw:   2mins 60%O2  0%He  Run Time= 33mins
   Stop=  12msw:   5mins 60%O2  0%He  Run Time= 38mins
   Stop=   9msw:   6mins 60%O2  0%He  Run Time= 44mins
   Stop=   6msw:  35mins 60%O2  0%He  Run Time= 79mins

     Total time to surface=60mins              
     Time to first stop=5mins                  
     CNS exposure: 34%peak, 34%dive end        
     CNS exposure= 34%                          
     Max PPO2=1.50bar  OTU=100units  OTUtotal=100
     Dive Start:   Day 1   Time 00:00        
     Dive Finish:  Day 1   Time 01:20        
     Flight Time:  Day 1   Time 06:18
     Surface gas=21%O2,  0%He
     Surface interval=   0mins                    
********************************************************************************
 Depth1=  30msw:   3mins 32%O2  0%He  Run Time=  3mins
 Depth2=  70msw:  17mins 17%O2 38%He  Run Time= 20mins
 Depth,    Gas,  Stop,  RT
     6,  60/ 0,    35,    79
     9,  60/ 0,     6,    44
    12,  60/ 0,     5,    38
    15,  60/ 0,     2,    33
    18,  32/ 0,     1,    30
    21,  32/ 0,     1,    29
    24,  32/ 0,     1,    28
    35,  32/ 0,     1,    26
    46,  17/38,     1,    23

Then last struggle to get out of the water after we passed our stages. And evrything went well after. About my trim I tought that either my twins were higher than before (as for this dive I didn't use mine but have used these without a problem before). More probably the lead I had in the waist was giving be a good trim and without I was going head first as at the end I was heavy just enough to hold my 6m stop. All equipemnt used for this dive is my usual.

Here is my profile of the dive, I know it's sh;t and I think is the worst I have ever had but considering bad trim and the rough weather but it's food for tought and would like your comments good and bad about the dive  
 

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<font color='#0000FF'>Hello all again,

Anyone here had same problem , with head down position trim? What was your problem, what do you do to solve it? Dive heavier?

Regards

Pierre
 

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<font color='#000F22'>I stuck a .5 kilo ankle weight on the back d-ring of my crotch strap. Problem solved.
 

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Yep i did the bulldozer dive a few times due to my tanks being set high enough for me to do manual shut downs. In the end I opted for the slob knob and lowered the tanks. This worked well and I never had the problem again.

Trim in twin set and stages is a diferent thing to normal trim and needs to be re lurnt. I am a bit surprised your instructor didnt get all the trim and weighting issues sorted out before actualy doing the 70m dive. I spent a fair bit of time at 6 -10m with stages ranging between 100 bar and empty and 50 bar in my twin set before attempting an actual deco dive in the rig.

That said you obviously overcame the dificultys enough to pull off the dive so well done for that.

In my early days of deco I used to always be overweight to guarentee the 6m stop. Then I started to fiddle with weighting so I could hold a horizonrtal trim without effort. End result was 4kg (2 on each hip) a SS back plate and that was it. (5mm dry suit)

I would like to experiment with V weights at the bottom of the twin set and raising the tanks higher to enable shut downs. This will be my pet project for the winter months


Glad it all went OK in the end.

ATB

Mark Chase
 
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