What size doubles?

[Eris Lucan7*]

...Maybe you do know all about it!!!

E.L.7*

 

[nereas]

He's looking for his first set of doubles. It's probably better to find a manageable size and reasonable volume, not necessarily the largest tanks he'll ever need.

Again, he's looking for his first set of doubles. A skilled doubles diver can dive any tanks and make it look easy. But picking a tank that is best suited to your individual build will ease the transition. And moving tanks too far in the bands can make valve manipulation difficult.

Which U-boats would you be diving off South Carolina?
Sealife isn't usually why people dive caves. And from Upstate South Carolina, North Florida cave country is about the same drive as the region's best wreck diving (Morehead City).

I would bet that you would be a great mentor for this fellow!

I believe you are right about the "first set" issue. LP85s therefore come to mind.

 

[xiSkiGuy]

I would bet that you would be a great mentor for this fellow!

I'd be happy to help out if he ever dives Lake Jocassee.

I believe you are right about the "first set" issue. LP85s therefore come to mind.

I agree. I think they make a great first set for most people.

 

[Mr. Bubble]

Thanks everyone....WHy do some of youadvocate the LP rather than the HP ?? I can't imagine an LP having more CF of air than a HP filled to 3442.

Yes, both the NC coast (U352 fyi) and the North Florida springs are about the same distance. I went on a NC dive this past summer and the DM had HP95's.

Yeah I dive Jocassee on occassion, just to fill the void every now and then.

So, why LP and not HP...I think I can handle the HP95's........

I dive single HP120's now.


Mr. B

 

[Rainer]

Reasons I dive LP85 doubles:

Trim (no HP equivalent cylinder)
Cheaper (*much* less than similar capacity HP cylinders)
Capacity (I also have HP100s, but with short fills on those, and "good" fills on the LP, I get the same capacity on my LP85s as my HP100s, if not better on the LPs)
Transfilling (much easier to fill my LP cylinders from spare HP cylinders, than the other way around!)

 

[texdiveguy]

Rainer, you might just define a 'good fill' for the OP....I know were you are with this,,,but he may not......

 

[Dive-aholic]

Mr. B, your height may or may not eliminate some tanks. LP95s are usually a little shorter than the other usual tanks. If you are 5'8" or shorter, they may be the tank for you. If you're 5'8" or taller, then you may want to go with a taller tank for better trim. Eventually you should be able to dive any tank so that won't matter much. I'm 6' and can dive pretty much whatever tank I'm given, but the taller tanks do trim out a little better on me. As for LP v. HP. An LP95 holds 95cf of gas when filled to 2400psi. An HP100 holds 100cf of gas when filled to 3442psi. Fill an LP95 to 3600psi and the tank is now holding a lot more than 95cf. Fill an HP100 to 3000psi and it's holding a lot less than 100cf. Some shops can only fill to 3000psi. Some places will fill LP tanks to 3600 regularly. Also, I haven't heard of an HP95. Who is making that?

 

[Mr. Bubble]

Also, I haven't heard of an HP95. Who is making that?

Good point! I'm pretty sure thats what he told me. Maybe he ment Lp filled to 3600= HP...??? I looked up available tanks and you are right...no HP95's only LP.

I did not realize filling up to capacity was that difficult. I have not run into that problem yet. So, LDS' will top off an LP to 2600 if they have the ability? So with temp. variation it may go back to 2400 which is about 100psi below the rating right? And a set of HP 100's filled to 3800 (if they can fill it that fare) would settle to 3500 give or take.
so were are talking only 10-12 cf of air........thats a pretty good bit to get you out of a jam if you needed it.....

But task loading is another point as well........it may take up that extra air just to haul those big puppies around.

B

 

[cool_hardware52]

Some shops can only fill to 300psi.

I'd avoid them

Tobin

 

[fweber]

As you've specified that these are your first set, and likely to be used to around 130' and it sounds like in open ocean or overhead wreck diving. You might want to really consider the lp85's that others have mentioned. I have 4 sets of old 72's(rougly the same dimensions as 85's) only because they were around and available. If I were going to go out and purchase new steel for open ocean diving it would be 85's or the hp equivilent in physical size. They usually provide sufficient gas for dives with run times in the 45-60 minute range and contingencies of upto around 90 minutes. However, there are plenty of other things to consider. One, what are your buddies diving? While any decent deco class is going to teach you enough to make gas matching with your buddies easy, identical tanks make it a non-issue. Second, if you're diving from charter boats, you may find it's easier to bring one large set of doubles that you can get 2 dives from. It can save on space requirements and elimanates the need to change tanks between dives.

There are alot of variables that can lead to one setup being preferable to another. You really have to weigh out your particular circumstances to come up with the ideal solution. I would however suggest talking to your instructor/mentor, who will probably have reasonably strong reasons why they dive the way they do. And, talk or coordinate with your likely buddies or teammates.