RDP questions

[oreocookie]

HELP!! OK..I think I got the first part...but not the second.

Day 1-
Dive #1 100 feet for 10 minutes (which means we are in PG E)
Dive #2 60 feet for 20 minutes (which means the RNT was 11, the ABT was 20 minutes and the TBT is 31 minutes/the SI is 1:00 hr) which puts us at PG B
Dive #3 40 feet for 30 minutes (which means the RNT is 9, ABT is 30 and TBT is 39) my new PG is L and after a SI of 2:15, we would end the day at PG A

Right??? Oh please be right

Looks like you've got most of it right. Remember to take note of your pressure group at the end of the dive and at the end of the SI.

Dive 1 - 100ft for 10 mins, you're indeed in PG E
SI of 1:00 puts you in B. so far so good.
Dive 2 - 60ft for 20 mins. RNT is 11, ABT is 20, TBT is 31 minutes. This puts you in L.
SI of 2:15 puts you into PG A.
Dive 3 - 40ft for 30 mins. RNT is 9, ABT is 30, so TBT is indeed 39. This puts you into group I at the end of your dive day.

Work out each section before moving on to the next (dives and SI's) or you'll miss something, which is what looks to have happened here.

Day 2 I picked 40 feet for 30
The first PG would be F and the second would be V...but there is no intersection of F on the diagonal and V at the bottom???

Help please

Determining the minimal SI is the trickest part of these tables to me

That dive would indeed put you into F, but I'm not sure where you're getting the V from.

I'll give you my own example to see if I can help you here.
Lets say Dive 1 is 60ft for 35 mins and Dive 2 is going to be at 50ft for 45 mins.
At the end of Dive 1, I'd be in PG N. Now look at table 3 (where you got your RNTs) to find out what post-SI pressure group has an adjusted NDL of atleast 45 mins. PG J has an adjusted NDL of 47 mins. The intersection of N and J gives a surface time of 0:19 - 0:24. So the minimum surface interval required to do these dives would be 19 minutes.

Hope this helps.

EDIT: ok, I see where you're getting the V from. You have the right idea. The reason there's no intersection is that there's no minimum surface interval required to do these dives. At 40ft, the NDL is 140 mins, so even doing 2 30 minute dives back to back is still within NDL, meaning that no surface interval is required.

 

[boulderjohn]

You are really close--just a couple minor problems.

HELP!! OK..I think I got the first part...but not the second.

Day 1-
Dive #1 100 feet for 10 minutes (which means we are in PG E)
Dive #2 60 feet for 20 minutes (which means the RNT was 11, the ABT was 20 minutes and the TBT is 31 minutes/the SI is 1:00 hr) which puts us at PG B
Dive #3 40 feet for 30 minutes (which means the RNT is 9, ABT is 30 and TBT is 39) my new PG is L and after a SI of 2:15, we would end the day at PG A

Right??? Oh please be right

I think you are confusing things, or at least it seems to me because you wrote things out of the normal sequence of the thought process.

First dive = 100 feet for 10 minutes, pressure group E
Surface Interval = 1:00; pressure group B--that is where you start the second dive.
Second dive at 60 feet, starting at pressure group B. 20 minutes BT plus 11 minutes RNT = 31 minutes TBT. You treat the second dive as if it were a 31 minute dive because of the RNT. A 60 minute dive for 31 minutes gives you pressure group L. So you END the second dive as an L diver.
Surface Interval = 2:15, putting you at pressure group A. That is where you START dive number 3.
Dive number 3 is 40 feet at pressure group A, so you have to add 9 minutes to your actual bottom time as a "penalty" for multiple dives. Adding those 9 minutes to the 30 minute dive gives you a 39 minute dive at 40 feet. A 40 foot dive for 39 minutes puts you in pressure group H at the end of your dive.

Day 2 I picked 40 feet for 30
The first PG would be F and the second would be V...but there is no intersection of F on the diagonal and V at the bottom???

Help please

Determining the minimal SI is the trickest part of these tables to me
Dive #3 40 feet for 30 minutes

I asked you to plan two dives in the least amount of time. DO you want both to be 40 feet for 30 minutes? OK.

First dive is 40 feet for 30 minutes, putting you in pressure group F.
Now look at the back of the card at the 40 foot line as see what pressure group you have to be in to do a dive for 30 minutes. That's where you got the V. The reason you are confused is that you picked two really easy dives. You have to be at least a V diver to do the second dive, but you are already an F diver, so you don't need any surface interval at all. You could have done both dives without even going to the surface.

Let's do it with two more serious dives.

First dive will be 80 feet for 23 minutes = Pressure group M.
I want to do a second dive of 60 feet for 37 minutes.

I go to the back of the card and look for 60 feet for 37 minutes. I see that I have to be in pressure group E to dive that deep for that long.

I go to the front of the card and find pressure group M. I then trace across until I get to pressure group E. I see that it will take 47-55 minutes to get to pressure group E, so the minimum time is 47 minutes.

 

[EFB]

I went back with hubby tonight and re-did these problems and finally got your answers. We had never encountered no intersection due to shallow and short dives.

We also wrote down the problems from the RDP little booklet and came up with the right answers...I'm trying not to over think this.

 

[oreocookie]

Thanks for making me feel slightly useless, John. You probably explained it a little better than I did, but then again, seeing it multiple times in slightly different ways can only be beneficial to the OP or anyone else trying to learn tables.