Odd profile deco diving.

Martin Burnard · September 5th, 2007, 01:50 PM

The thread on the VR3 started me on this!

My buddy and I do a dive here in Plymouth which is an odd profile and sorting out the dive plan deco schedule is not so easy. OK we have it sorted now but how do other people deal with odd profiles?

Here is the way it runs.

0-12m is a 5 minute dive (surface current makes surface swim out of the question) of fairly consistent slope.

12m to 25m is 3 minute dive, a gradually increasing slope.

25 to 35m is vertical wall, but due to strength of current takes 2 minutes to drop.

35m to 45m to 35m to 30m is the bottom so 15minutes spent on bottom.

Ascent is wall to 20m, slope to 12m (10 minute dive) , then long slow dive (30 minutes) in on a gentle slope to surface.

Gases used 21/35 and 50% deco gas. Gas switch at 21m.

Now we break this down into each segment and then run it through V-planner assuming 45 metre constant bottom (see always cautious). Apart from the ascent where we work on the basis that last 20m ascent over 40 minutes must be fine (or am I barking up the wrong tree?)

If you run a dive computer (well Tec2G) on this dive it hates the long slow ascent and penalises accordingly (so we hang around at 3m waiting for that to clear.)

If I run a 45m dive on the V-planner for 21/35 and 50%. it gives roughly the same dive time as the Tec2G on 21% and 50% (just a note as I like playing with figures).

Hope that is clear!

Martin

ogobara2000 · September 5th, 2007, 03:40 PM

Hi!

Hmm not much to add i think you pretty much wrote the dive plan down by describing the profile of the dive site. I think this particular dive is pretty well dictated by the distances you have to swim if you do it from shore.

I would come up the wall slowly and then do something like 2min every 3m after 21GS (in other words pretty much follow the slope slowly). From 10 onwards you can pretty much head home as the swimming takes you longer than you need to clear anyway.

Your description sounds like a nice dive in Eastern Kings and if it is i think this site gives you almost a perfect profile by simply following the seabed on your way up as most of the long last swim is around 6m anyway IIRC.

Have not checked with any dive planning software but i would assume that if anything it gives you a much shorter profile anyway.

Have a nice dive.

Martin Burnard · September 5th, 2007, 04:54 PM

You spotted the dive site!

It is the profile running from the entry around by Millbay and coming back with the tide to Firestone Bay passing Eastern kings on route.

Recieve one Gold star for alertness!

rjack · September 5th, 2007, 07:35 PM

Quote: (Originally Posted by Martin Burnard)

Now we break this down into each segment and then run it through V-planner assuming 45 metre constant bottom (see always cautious). Apart from the ascent where we work on the basis that last 20m ascent over 40 minutes must be fine (or am I barking up the wrong tree?)

I have not tried every possible ascent combo, but I'm not surpised that just about any old shape works here.

Quote: (Originally Posted by Martin Burnard)

If you run a dive computer (well Tec2G) on this dive it hates the long slow ascent and penalises accordingly (so we hang around at 3m waiting for that to clear.)

Ahhh, but really you are padding the shallow end. You could probably move a little quicker through the 15m-9m range.

Quote: (Originally Posted by Martin Burnard)

If I run a 45m dive on the V-planner for 21/35 and 50%. it gives roughly the same dive time as the Tec2G on 21% and 50% (just a note as I like playing with figures).

Not surpising. I dive 21/35 with zero He penalty.
Martin are you T1? (or just a math geek

) This all seems fairly predictable.

Martin Burnard · September 5th, 2007, 11:01 PM

Quote: (Originally Posted by rjack)

IMartin are you T1? (or just a math geek

) This all seems fairly predictable.

OI behave!

No I am not Tech1, although ratio deco is no great mystery.

Just probing how people deal with none square profiles.

I dive this run on the conservative side as it is tidal dependant (neaps/ springs), run off down the river dependant. so just curious.

I guess I am fishing for info or ideas that I may have missed.

rjack · September 6th, 2007, 05:05 AM

Take the class, the borg call...

Assuming a deep then shallow shift we just weight a tad deeper than the mathematical average (since it kinda hard to do rigorous math even with an END of 30M) and use that depth to base our depth-time relationship on.

September 5th, 2007, 01:50 PM	#1 (permalink)
Martin Burnard (Online) New Member Join Date: Nov 2005 Location: Plymouth, UK Posts: 580	Odd profile deco diving. The thread on the VR3 started me on this! My buddy and I do a dive here in Plymouth which is an odd profile and sorting out the dive plan deco schedule is not so easy. OK we have it sorted now but how do other people deal with odd profiles? Here is the way it runs. 0-12m is a 5 minute dive (surface current makes surface swim out of the question) of fairly consistent slope. 12m to 25m is 3 minute dive, a gradually increasing slope. 25 to 35m is vertical wall, but due to strength of current takes 2 minutes to drop. 35m to 45m to 35m to 30m is the bottom so 15minutes spent on bottom. Ascent is wall to 20m, slope to 12m (10 minute dive) , then long slow dive (30 minutes) in on a gentle slope to surface. Gases used 21/35 and 50% deco gas. Gas switch at 21m. Now we break this down into each segment and then run it through V-planner assuming 45 metre constant bottom (see always cautious). Apart from the ascent where we work on the basis that last 20m ascent over 40 minutes must be fine (or am I barking up the wrong tree?) If you run a dive computer (well Tec2G) on this dive it hates the long slow ascent and penalises accordingly (so we hang around at 3m waiting for that to clear.) If I run a 45m dive on the V-planner for 21/35 and 50%. it gives roughly the same dive time as the Tec2G on 21% and 50% (just a note as I like playing with figures). Hope that is clear! Martin __________________ I once enjoyed a sado-masachistic frenzy of total tintintabulation leading to a state of metampsychosis... or did I make that up? www.bananafrogcars.co.uk

September 5th, 2007, 03:40 PM	#2 (permalink)
ogobara2000(Offline) New Member Join Date: Dec 2005 Location: Plymouth UK :) Posts: 99	Hi! Hmm not much to add i think you pretty much wrote the dive plan down by describing the profile of the dive site. I think this particular dive is pretty well dictated by the distances you have to swim if you do it from shore. I would come up the wall slowly and then do something like 2min every 3m after 21GS (in other words pretty much follow the slope slowly). From 10 onwards you can pretty much head home as the swimming takes you longer than you need to clear anyway. Your description sounds like a nice dive in Eastern Kings and if it is i think this site gives you almost a perfect profile by simply following the seabed on your way up as most of the long last swim is around 6m anyway IIRC. Have not checked with any dive planning software but i would assume that if anything it gives you a much shorter profile anyway. Have a nice dive. __________________ You are free....to do as you are told

September 5th, 2007, 04:54 PM	#3 (permalink)
Martin Burnard (Online) New Member Join Date: Nov 2005 Location: Plymouth, UK Posts: 580	You spotted the dive site! It is the profile running from the entry around by Millbay and coming back with the tide to Firestone Bay passing Eastern kings on route. Recieve one Gold star for alertness! __________________ I once enjoyed a sado-masachistic frenzy of total tintintabulation leading to a state of metampsychosis... or did I make that up? www.bananafrogcars.co.uk

September 5th, 2007, 11:01 PM	#5 (permalink)
Martin Burnard (Online) New Member Join Date: Nov 2005 Location: Plymouth, UK Posts: 580	Quote: (Originally Posted by rjack) IMartin are you T1? (or just a math geek ) This all seems fairly predictable. OI behave! No I am not Tech1, although ratio deco is no great mystery. Just probing how people deal with none square profiles. I dive this run on the conservative side as it is tidal dependant (neaps/ springs), run off down the river dependant. so just curious. I guess I am fishing for info or ideas that I may have missed. __________________ I once enjoyed a sado-masachistic frenzy of total tintintabulation leading to a state of metampsychosis... or did I make that up? www.bananafrogcars.co.uk

September 5th, 2007, 07:35 PM	#4 (permalink)
rjack(Offline) wet behind the ears Join Date: Nov 2005 Location: Seattle, WA Posts: 860	Quote: (Originally Posted by Martin Burnard) Now we break this down into each segment and then run it through V-planner assuming 45 metre constant bottom (see always cautious). Apart from the ascent where we work on the basis that last 20m ascent over 40 minutes must be fine (or am I barking up the wrong tree?) I have not tried every possible ascent combo, but I'm not surpised that just about any old shape works here. Quote: (Originally Posted by Martin Burnard) If you run a dive computer (well Tec2G) on this dive it hates the long slow ascent and penalises accordingly (so we hang around at 3m waiting for that to clear.) Ahhh, but really you are padding the shallow end. You could probably move a little quicker through the 15m-9m range. Quote: (Originally Posted by Martin Burnard) If I run a 45m dive on the V-planner for 21/35 and 50%. it gives roughly the same dive time as the Tec2G on 21% and 50% (just a note as I like playing with figures). Not surpising. I dive 21/35 with zero He penalty. Martin are you T1? (or just a math geek ) This all seems fairly predictable.

September 6th, 2007, 05:05 AM	#6 (permalink)
rjack(Offline) wet behind the ears Join Date: Nov 2005 Location: Seattle, WA Posts: 860	Take the class, the borg call... Assuming a deep then shallow shift we just weight a tad deeper than the mathematical average (since it kinda hard to do rigorous math even with an END of 30M) and use that depth to base our depth-time relationship on.