Scooter planning in caves

[rjack321]

The whole stage bottles in caves thread has been very helpful to understand "the big picture" which is beyond my current state of training...

In the same vein, I'd like to hear how scooter burn times and redundancy issues are considered by the various "DIR" members here using scooters in caves. Yes I've read little planning blurbs on the Gavin website and similar, that is just enough info to still be but not look clueless.

When do you consider alt. exits, potential to swim out, one or 2 backups for the team vs. one or more each, potential to be exiting 'slower' than you might have anticipated if you have to run one scooter to the max, necessity of stages, using 1/6ths of total gas or of backgas when not using stages, etc. etc.

Edit: moved? I figured the main DIR forum would allow the non-DIR to see the DIR reasoning, but hey this is fine too.

 

[RTodd]

I moved this one to the DPZ where you should get more appropriate answers. The user list in this area has grown enough now that this forum can be more extensively used.

Unfortunately, the answer to this question is, it takes experience. Start on short short body dives using a single stage and diving sixths. Learn from there. You really have to discuss this in terms of specific scenarios.

 

[rjack321]

In a team of 2 you'd bring one backup? How about in a team of 3, one or two backups?

For your first forays would you dive a stage and reserve 100% of backgas, or chose 1/6ths of backgas (no stage) for simplicity? Since you are diving smaller scooters... 1/3rds on trigger time will be ~20mins which at least for MX is less time than I would typically use 500psi of backgas or 1300psi of a stage in anyway. So I think I'd go for the no stage option to minimize chance to wacking something.

As you build experience would you add additional smaller scooters for everyone and use them to 1/3rds each or go for longer bodies with a single towed team backup?

Sorry lots of jumbled questions...

 

[lamont]

initially, don't you just want to start playing around with smaller scooters in caves that you can swim out of (and reserving enough gas to do so)?

 

[rjack321]

I'm not sure if I did a 1/6ths (500psi) scooter penetration I could swim out with suitable reserves. Really it would be a 20min penetration cause I would use 1/3rd burntime on a shortbody before hitting 1/6ths anyway.

In 20mins I could be 3000ft back (175ft/min but some time lost on a T or a jump or something since I have yet to dive a MX cave with a 3000ft tube).

To swim out of that would take roughly 1500psi maybe a little more, so I'm guessing that 5/6ths is quite a marginal reserve to swim out. I don't really know, hence the question (which came up in the other thread) if scooter automatically = stages.

 

[KMD]

I'm not sure if I did a 1/6ths (500psi) scooter penetration I could swim out with suitable reserves. Really it would be a 20min penetration cause I would use 1/3rd burntime on a shortbody before hitting 1/6ths anyway.

In 20mins I could be 3000ft back (175ft/min but some time lost on a T or a jump or something since I have yet to dive a MX cave with a 3000ft tube).

To swim out of that would take roughly 1500psi maybe a little more, so I'm guessing that 5/6ths is quite a marginal reserve to swim out. I don't really know, hence the question (which came up in the other thread) if scooter automatically = stages.

I think 175ft/min on a scooter is a bit too much.... At most I have heard travel speeds of around 150ft/min.... If one guestimates 50ft/min swimming speed means you would have ~ a 60 minute swim back. Using sixths would give you ~ 120 minutes of bottom time of which one used 80 minutes for the complete dive or roughly 2/3rds.

From a total newbies perspective, it seems to pass the smell test. Diving with a buddy one could loose their scooter at max penetration and still get towed or kick back, or the team could loose both scooters, or one scooter and backgas and still be allright. After three major failures then things would get dicey.

 

[rjack321]

Yes 175ft/min was a bit high. That was my 1st guess but got a couple of PMs about that being unrealistic.

I guess I'm struggling with the comments in the other thread about scooters = big reserves
vs.
dive 1/6ths as a scooter noob and be prepared to swim it out

How does one progress from the 1/6ths + swim backup? What's the next step people took in their career? Why did they tow one spare or go to stages or whatever. I'm not trying to learn to dive on the internet, but its hard to see how people have developed their skills outside of specific classes (e.g. the experience portions of DIRness). E.g. dialogue along the lines of this report:
Cave Diving Scooter Workshop in México - DIR Explorers

 

[RTodd]

The general rule is that, when first scootering, you don't scooter anywhere you have never done a swim dive. So, at first you should always know how much gas you need to exit swimming. The minimum reserve is double that.

For me scooters=stages. I really never do a scooter dive without a stage. Get used to the scooter and the stage outside of the cave. Your first scooter dives should only be in big caves you can't hurt anyway.

For a 20-30 minute scooter ride in Mexico I don't consider a backup scooter an absolute requirement. But, I would not use much gas on such a dive and would always have plenty of gas to swim out sharing gas if my buddy lost his scooter too. However, for shorter scooter dives we generally carry at least one backup and for most dives everyone carries a backup.

 

[lamont]

how do you back-kick when you're towing a scooter? and once you hit deco and don't need to be streamlined anymore do you reposition the towed scooter on a different d-ring?

 

[RTodd]

how do you back-kick when you're towing a scooter? and once you hit deco and don't need to be streamlined anymore do you reposition the towed scooter on a different d-ring?

Basically, you don't. Technically doable, but once you are loaded with scooters and stages, the scooter is your propulsion. Once I get to deco, what I do with the scooter depends on the location. If we are surfacing and exiting right where decoing, I clip everything off to a leash and get it out of the way which makes clipping it off after surfacing easier. If it is a shorter deco but requires a ride out, I usually just leave it in place, but would move unused stages that were still on my chest to just the waist d-ring.

For a short body, you can wrap a leash around the handle and rig it like a stage but there is rarely a reason to ever do this.