v-planner vs. GAP software

[deepdarkblue]

I'm currently using V-planner, but have seen the GAP software but have never thought to invest in it, for anyone who has used it, is the GAP planner worth the investment vs V-Planner?  What are its pros and cons?

[arcFlash]

You may want to search DecoStop.com. I think they even have a topic for this stuff.

[john j]

I can speak a little about the decompression algorithms.  I can't speak much about the dive planning or gas usage functions of these software packages, since I don't use software much for those calculations.

GAP has the RGBM algorithm.  V-planner (at least the versions I have seen) does not have RGBM. 

In my opinion, RGBM is somewhat superior to the other algorithms for long, deep helium-mix dives.  Generally speaking, RGBM gives longer deep stops but less overall decompression time than the other models.  For dives shallower than about 225 feet and less than about 20 minutes bottom time, there is only a few minutes difference in total deco times between RGBM and the others.  For longer and/or deeper dives the difference can be much larger.  For example, a dive we have done is 360 feet for 35 minutes. RGBM reduces deco time by around 20-30 minutes compared to other common algorithms for this dive and allows non-scheduled deep stops without severe penalty.  Some of the non-RGBM models (like the one in the VR3) penalize you greatly for doing deep stops that are not called for in the deco schedule.  RGBM includes deeper stops and penalizes you much less less if you insert your own deep stops.

GAP is not cheap, so if you can't justify the need for RGBM, it may not be worth the extra cost.

I think v-planner is easier to use and more intuitave than GAP.

None of the algorithms that are available to the sport diver are very well tested beyond 300 feet.  Deeper than that, you are kind of cutting new ground so to speak.

Another problem with most or all of the algorithms out there is that they penalize the diver (add more decompression time) when helium mixes are used.  It was previously thought based on diffusion rates, solubility, etc.  that helium required more decompression than nitrogen.  Slowly, the tables are turning on this belief.  Evidence that helium is actually faster to offgas than nitrogen is now emerging.  I haven't done numerical comparisons, but it looks to me like RGBM penalizes you less than the other algorithms for using helium.  So there is another advantage for RGBM.  You have to go pretty deep to see a difference of more than a few minutes in total deco time though.

I don't know what kind of diving you are doing, but I would say if you are not doing super-deep, long dives (beyond 250 feet for 25 minutes) and if there is not some specific function you need that GAP would provide, then save yourself some money and consider v-planner.  I have used v-planner for a lot of deep dives and I'm still OK.  Well... maybe that's debatable.

[trob09]

I have both v-planner and GAP

I dove OC with v-planner for years doing dives up to about 275'  V-planner uses the VPM algorithm.  In my experience  VPM generates profiles that are indistinguishable from RGBM profiles.

I purchased GAP because it will generate Buhlman with gradient factors tables on CCR that match my rebreather electronics.  I did not purchase it for the RGBM capability

RGBM is fine.  As I say, it generates near identical profiles to VPM.  If you're happy with v-planner, there's no reason to spring for GAP.

[rcojr]

In my experience  VPM generates profiles that are indistinguishable from RGBM profiles  ???
That hasn't been my experiance. I agree with what John said. On deeper dives we get deeper Deepstops and less overall run times.
A buddy of mine and I did a dive on the Moonlight (240ft)
I was using my Explorer computer on CF2.
He was using a computer with the VPM-B. 240 ft for 20 mins. My computer cleared and his still had 20 mins. to go. He wound up blowing off the last 10 mins. of his deco. His comment back on the boat was "This is Nuts"
He now has an Explorer.
Bob

[DiveCaptDean]

He ended up blowing off his last 10 min..............

Keep in mind young divers....this is not taught in recreational dive class.......nor is it condoned in the technical diving community.........one doesnt blow off deco time because his buddy is getting out of the water before him.....Granted..the diver knew exactly what he was doing......but the proper solution would have been to finish the 10 minutes and adjust his issues above water...

[glow=red,2,300]Dont try this at home[/glow][flash=200,200][/flash]

[trob09]

Interesting.  We've been running profiles using RGMB, VPM and Buhman with GF set to emulate "bubble models" profiles and have had very consistent run times in the 200' - 300' range.  There are variations in the middle (i.e. the shape of the curve), but the run times are consistent (2-5 minutes max).

If by "using a computer with VPM-B" you mean the VR3 with VPM, this is not a true implementation of VPM.  It has additional conservatism in the algo.

Tim

[rcojr]

If by "using a computer with VPM-B" you mean the VR3 with VPM, this is not a true implementation of VPM.  It has additional conservatism in the algo.


Ahh that would be the difference. I was speaking about the VR3