New divers with question on calculating min sufrace intervals!

Please register or login

Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.

Benefits of registering include

  • Ability to post and comment on topics and discussions.
  • A Free photo gallery to share your dive photos with the world.
  • You can make this box go away

Joining is quick and easy. Log in or Register now!

ricster80

Registered
Messages
5
Reaction score
0
Location
London, England
Hi All,

My Girlfriend and I are currently nose deep in learning to dive and have managed to get stuck on using the RDP card to calculate minimum surface intervals.

In particular there is one example we can't understand; it's question 7 on the chapter 5 knoledge review in the open water diver manual. The example results in a pre second dive PG of M and a post dive PG of P. These two letters don't match up in table 3.

Should you assume that this means the min surface interval between dives is zero? Surley that can't be right?

Can anyone help?

Thanks,

Ric n Ros. :idk:
 
Without knowing the entire question it is hard to tell. I remember one "trick" question we had in our OW class that resulted in a SI less than 10 minutes. In this case the second dive is considered a continuation of the first.

HTH,

Jason
 
I got in trouble on that translating 1:20 as 120 minutes rather than on HOUR and twenty minutes.
Not those numbers, exactly, but that type of error. Double check your numbers. Maybe not the problem, but that was a mistake I made...good luck!
 
Ok guys,

Here's the full question:

'What is the minumum surface interval required between the following dives: first dive to 20m/70ft for 29 mins then to 14m/50ft for 39mins?'

The result is pressure group M at the end of the first dive and you must be at at lease group P before the second dive begins. These two letters don't match up on table 3 so no min surface interval can be determined.

Does that mean that you could theoretically dive to 20m for half an hour, surface, then dive straight back down to 14m for 40 mins without taking a break in between to allow Nitrogen to disperse?

Doesn't seem right to me; is there a minimum surface interval between all dives that should be observed whatever depth you go to (above 40m obviously)?

The problem is not isolated to these particular dives as above. I just can't get my head around what happens if your two PG's don't match up...

Thanks for your help.

Ric.
 
What tables are you using?

According to NAUI tables you would be at group F after the first dive. In order to do a 50/39 you would need a min 0:46 to put you at a new group of E.

Jason
 
I guess my table must be different.

I'm using the RDP by 'Diving Science & Technology Corp' which is distributed by PADI in their OW Crew Pack. It has Product No. 66055 Ver 1.2 (02/03) stamped on it.
 
I see what you mean. Group P or lower allows the dive, and you finish at M, so....
no SI is indicated. I always try to take a one hour SI, at least. I just browsed and didn't see a recommended mandatory SI in PADI OW. It sounds like you're working the table correctly, so check with your instructor, or I'm sure a certified instructor will be along presently to answer about agency recommendations.
 


A ScubaBoard Staff Message...

Moved to basicScuba
 
??

70ft for 29 mins puts you in "N" according to the above linked table.

50ft for 39 mins requires "M" according to the same table.

"M" intersects "N" with a minimum surface interval of 4 minutes.
 
https://www.shearwater.com/products/swift/

Back
Top Bottom