How do you calculate when to turn when using a scooter on OC?

[Dsix36]

I know that turning on thirds (or even sooner if conditions dictate) is the most common approch to OC cave diving but what changes when you scooter. Suddenly you get much further into the cave before you ever hit thirds. There is no way you have enough gas to swim out if the scooter dies. Knowing your SAC rate, swim rate, and gas amounts makes for easy calculation of the distance you can swim with given amounts of gas BUT Y0ou are using gas as you go into the cave (and this can vary from day to day and dive to dive) so how can you truly plan when to turn in a realistic manner that is acceptable,

Very simplified example: swim @ 50fpm, scooter @ 150fpm, SAC @ .5, 160 cf of gas @ 3000psi, 4ATA
Swimming =Thirds is at 2000psi in 20 minutes with 1000' of penetration
Scootering =Thirds is at 2000psi in 20 minutes with 3000' of penetration

Simple logic tell me that is an easy way to die so one must plan according having enough gas to swim out but it can never be a linear plan due to variables of each dive. Turning must be done on thirds of the lowest common denominator. Scootering to 1000' and turning will be way early of 1/3 of my gas supply and at the end of my dive is when I will finally reach thirds. Meaning I turned at sixths. Is there a simple magic formula to calculate proper turn time on the fly?

RB diving is simple since I never touch my OC gas and thus I still have full tanks at only penetration.

OK, let the keyboard warriors attack for asking for online training etc. I have thick skin and really do not care. It will be fun to see how the different replies tally up

 

[NothingClever]

What did your instructor teach you in your cave DPV course?

I get that our memories can be hazy.

What do your course materials say?

 

[Johnoly]

How many diver's on your team?

 

[Vicko]

I think everyone should try to tow their scooter out on OC just to see how physical demanding it is and then remember that it's still neutral/positive. Flooded scooter deep in a cave is a very expensive sack of bricks.

It's a serious question, do you double your SAC for safety, do you triple it?

 

[Mobulai]

I think everyone should try to tow their scooter out on OC just to see how physical demanding it is and then remember that it's still neutral/positive. Flooded scooter deep in a cave is a very expensive sack of bricks.

It's a serious question, do you double your SAC for safety, do you triple it?

Along these lines is my guess

Being extremely uneducated / unpracticed in these specializations (cave, dpv) I’d personally have an overly conservative guess — worst case scenario of towing the dpv back

Or, the gas plan has to include a battery plan as well

 

[grantctobin]

What do your course materials say?

I don't think I am incorrect in suggesting that the most of the cave dpv written documentation is garbanzo beans. I also think that if you put ten average current cave dpv instructors in a room and asked them to show their work, you'd get a rather large list of opinions. Hell, there are people walking around teaching incorrect stage math.

Answer: bring two DPVs Scooter math is closer to ccr math than it is OC math imo

 

[broncobowsher]

I think everyone should try to tow their scooter out on OC just to see how physical demanding it is and then remember that it's still neutral/positive. Flooded scooter deep in a cave is a very expensive sack of bricks.

It's a serious question, do you double your SAC for safety, do you triple it?

I would think that if the scooter died at the point you would call the deepest penetration that you have gas to get out with, drop the scooter and don't try to drag it with you. Why work harder to haul dead gear out that could leave you dead?

 

[Asheron]

For CCR i have an Avg depth vs BO gas quantity that gives me turn times. It works for linear dives well, but loses effectiveness in hub and spoke.

You would know your 1) scooter travel speed 2) scooter towing speed 3) scooter towing sac rate 4) Gas quantity

With these you should be abke to develop a chart that will tell you turn time based on AVG xepth your computer reads.(again pending its linear and some things like not stopping for long periods at the shallowest point). Deco quantities would also need to. be subtracted from available gas.

 

[mr_v]

I doubt that there is a single formula, Don. There are too many variables. The calculations are cave, team and route specific. You can start with identifying cf/ft for the route, adding a safety factor, and going from there.

@Vicko , @Asheron - if my scoot fails, I'll leave it there and come back. There is no reason to increase complexity. Towing scooter is a pain in the back, especially if the scooter is flooded.

 

[jadairiii]

I always used stages with scootering, dont touch my back gas. My buddies and I normally, in a typical flow cave, 1/2 + 500 when we would either turn on our stage or drop it and go to our new stage.