Differences Between UTD and GUE

[Rainer]

I'll be honest, I think the way AG does O2-only deco (half deco time on back gas coming into the O2 switch) is wonky. I don't know what it's based on, since no other deco algorithms generate such profiles. It certainly isn't motivated in the UTD RD slides. In most cases, it just keeps you in the water longer (roughly same O2 time), so not a huge deal, but it does seem unmotivated. At least UTD *has* an algorithm for O2 dives (a huge GUE weakness, IMO). For these shallow (<120') dives, most GUE people I know are simply doing time over NDL, half credit for O2 + extra five min up on the O2 (the back gas deco up to 20' is done differently by different teams; so much for uniformity...).

 

[boomx5]

Interestingly enough, I just finished running an RD dive I did this weekend through V-Planner (which I know is not Bulmann). We did have almost exactly the same run time, but the V-Planner schedule had us spend more time on O2, while RD had us spend more time on back gas (25/25) before the O2 switch.

(I was interested in trying to figure if there was any obvious reason my buddy got bent.)

Hey John,

I was wondering...how big were the differences in profiles between RD and V-Planner?

Thanks,

 

[boulderjohn]

Hey John,

I was wondering...how big were the differences in profiles between RD and V-Planner?

We averaged 130' depth for 43 minutes.

The first difference is that V-Planner includes altitude in its calculations and RD does not. We were diving at about 5,000 feet, and it makes a 4 minute difference in deco time for V-Planner.

The next difference was that RD has deep stops at 90, 80, and 70, whereas V-Planner has its first stop at 60, and it is darn brief there. The 60 and 50 minute stops were more for RD as well. The 40 and 30 foot stops were about the same. All the added time from the deeper RD stops is put into the O2 stop for V-Planner.

 

[Rainer]

You said VP gives more O2 time than RD for this dive. What did you calculate the O2 time at on RD? I get 15 minutes from VP (I didn't bother to add the elevation info). I don't get less time on RD, but curious how you're calculating the requirement.

We averaged 130' depth for 43 minutes.

The first difference is that V-Planner includes altitude in its calculations and RD does not. We were diving at about 5,000 feet, and it makes a 4 minute difference in deco time for V-Planner.

The next difference was that RD has deep stops at 90, 80, and 70, whereas V-Planner has its first stop at 60, and it is darn brief there. The 60 and 50 minute stops were more for RD as well. The 40 and 30 foot stops were about the same. All the added time from the deeper RD stops is put into the O2 stop for V-Planner.

 

[boomx5]

We averaged 130' depth for 43 minutes.

The first difference is that V-Planner includes altitude in its calculations and RD does not. We were diving at about 5,000 feet, and it makes a 4 minute difference in deco time for V-Planner.

The next difference was that RD has deep stops at 90, 80, and 70, whereas V-Planner has its first stop at 60, and it is darn brief there. The 60 and 50 minute stops were more for RD as well. The 40 and 30 foot stops were about the same. All the added time from the deeper RD stops is put into the O2 stop for V-Planner.

Hmmm...I wasn't there but it could've just been a physical thing...is he recovering ok? You know...the dives we do in Tahoe (6,200') we 've done using straight RD. We've also played with the numbers a bit where we've padded times, added more time on the 50%, pressed the gradient through the 50' & 40', spent more time on O2 etc. We find that a few minutes here or there doesn't make that big of a difference and have done mulitple different profiles for the same dives. I've found (for me) that a few minutes here or there doesn't make that big of a difference and generally pre-dive fitness/conditioning has a greater roll to play in how I fill post dive...but that's me. Personally...if I'm feeling tired or a bit dehydrated we'll pad the deco a bit more on the O2 and it really helps clean us up a bit more where we get out "feeling better".

 

[boulderjohn]

You said VP gives more O2 time than RD for this dive. What did you calculate the O2 time at on RD? I get 15 minutes from VP (I didn't bother to add the elevation info). I don't get less time on RD, but curious how you're calculating the requirement.

I got 21 on VP when I did it. If I omitted the altitude, it was 15 as well. The altitude makes a big difference in VP. In fact, I got a lower run time on VP than on RD when I took out the altitude. (Ross Hemingway, creator of V-Planner, told me this past spring that the altitude factor was very important.)

And by the way, that was what the doctor who treated my buddy said. He gave him Bruce Weinke's book on diving at altitude to read wile he as doing his 7 hours of Table 6.

We had planned to do a 40 minute dive, and our initial plan was for 15 minutes between 60-30 and 15 minutes on O2. I added the full overtime, dividing it between the 30 foot stop and the O2 stop. In fact, I added O2 time just to be safe--I thought.

 

[Rainer]

Interesting with the altitude stuff in VP. All my dives are at sea level (and with RD).

Just curious, did you do the entire O2 segment at 20' (15 min), then add 3-5 minutes up, or did you do 10 min at 20' and 5 min up?

 

[boulderjohn]

Hmmm...I wasn't there but it could've just been a physical thing...is he recovering ok?

Not that well, really. He did a full 7 hours on Monday and went back for 2 more hours yesterday. He still has some residual numbness in his right hand. The doctor is pretty sure he took a hit to the spine.

There was an additional complicating factor in that we had to cross a pass with a couple thousand feet of elevation gain about 3-4 hours after the dive. In preparation for that, we finished off the AL 40s of O2 and the AL80 safety bottle (only half full) while we were driving. We thought we were OK, but his came on while he was trying to sleep that night.

 

[boulderjohn]

Interesting with the altitude stuff in VP. All my dives are at sea level (and with RD).

Just curious, did you do the entire O2 segment at 20' (15 min), then add 3-5 minutes up, or did you do 10 min at 20' and 5 min up?

I added time. We did a full 17 at 20' and then took 3-5 up.

 

[Rainer]

I added time. We did a full 17 at 20' and then took 3-5 up.

Thanks. Sorry to hear about your buddy. That sucks.