Your idea of ideal twins

[dab]

I dive the oms LP 85's and love 'em. Easy to lug around, and are great for wreck diving. My son uses a pair of oms LP 112's and he is very happy as well. The recommendation of your instructor should be a major consideration.

 

[BigboyDan]

I dive the oms LP 85's and love 'em. Easy to lug around, and are great for wreck diving. My son uses a pair of oms LP 112's and he is very happy as well. The recommendation of your instructor should be a major consideration.

Ding! Ding !Ding!

I use the OMS LP 85s and 112s as well.

 

[Sideband]

6'4" / 230. In my drysuit, with the 400g thinsulate and an al80, I just tie an anvil to my butt. (Actually, about 34 lb of lead, in fw. Please nobody get me started on taking off lead. I have light bones and large lung volume, ok?)

BTW how does the switch to doubles affect bouyancy characteristics? If they say the bottle is x lbs negative when full can you treat that as the weight coming off your belt, more or less?

(Assuming a tank that is + when empty)
If you count the weight of the air in the tank towards weight you need to decend then you must also remember not to breath during the dive or you will be overly buoyant at the end of the dive. That could make for some really really short dives.
What you really need to do is take the setup yo are thinking about diving and do a bouyancy check with the bottles nearly empty. You should do that any time you change your configuration such as suit, tanks or other item that might change your buoyancy. It isn't just a new diver thing.

Joe

 

[Hyper-limits]

I dive the oms LP 85's and love 'em. Easy to lug around, and are great for wreck diving .

I'm also a big fans of the OMS LP's 85 for the reasons stated above. 75% of my dives are from shore and I find they just the right size for me.

 

[Don Burke]

I am about to engage in a tech course and I am considering the purchase of a pair of new bottles. I am looking for recommendations in terms of capacity and bouyancy characteristics.

..snip..

Thus there are so many options open to me that I'm a tad confused. Should I use the 120's as the doubles and get something else for rec use, or vice versa - get something else for the doubles and continue using the 120's for rec diving? (In that configuration, I like their bouyancy characteristics and the fact that I can often dive all day on one of them.)

Look into borrowing a set of small steel doubles for the course.

If you were closer, I would offer to loan you a set of 72s.

The idea is to have more gas than you need, but not so much that you are likely to hurt yourself, especially on boats.

 

[divad]

This may be a ridiculous question, but have you printed out a cylinder specification chart? Its ridiculously easier to crunch the numbers with a hard copy chart. Its all laid out before you, like a smorgasbord, while you're looking at different suggestions.

 

[matt_unique]

6'4" / 230. In my drysuit, with the 400g thinsulate and an al80, I just tie an anvil to my butt. (Actually, about 34 lb of lead, in fw. Please nobody get me started on taking off lead. I have light bones and large lung volume, ok?)

BTW how does the switch to doubles affect bouyancy characteristics? If they say the bottle is x lbs negative when full can you treat that as the weight coming off your belt, more or less?

I would suggest double alum 80's. 154CF is a good amount of back gas and they will be the most economical solution. You could pick up two used alum 80's for less than $200 for example. My doubles with bands and manifold weighs 96 lbs (full). You have to deal with the buoyancy shift of course. With a neoprene drysuit, thic winter thermals, dry gloves, deco bottle, reels, lights, etc., etc., etc. I use 28 lbs of lead in salt water. I'm 6' 180lbs.

I think your steel 120's would be overkill and too heavy. Obviously not an issue once you are in the water but carrying this rig around, to/from the boat/car will be a ball buster. If you were doing the Doria or U869 and wanted max bottom time/super long deco obligation then you would need this kind of volume of air. Short of that you would be more than well served with much less back gas in my opinion.

Ultimately comes down to your SAC rate though. If you have a high SAC rate you may want to consider 100's or such. Do you know your SAC rate? Do you have an idea of the profiles (depth, etc.) you would like to work to? Your instructor could help you or in fact we here could help you with an idea of the gas requirements you would need.

--Matt

 

[doole]

Thanks everybody for the great info. Just knew that would happen.

Haven't assessed my SAC in the generally accepted way but I am quite assured that it's going to be up there. Plus the course outline warns that some of the training dives are going to be lengthy. Thus I'm starting to gravitate towards bolting together my existing 120's. (Or perhaps a pair of 95's.) But I'll see what Heir Instructor says, too.

The points about working out (back to doing heavy leg days - yuck) as well as bouyancy checks not just being for new divers were particularly well taken. Thanks again, everyone.

 

[bottomrunner]

...and no, I don't mean the kind of twins that have been sending you all those Email invitations to visit their web site. :07: (Actually, I mean doubles.)

I am about to engage in a tech course and I am considering the purchase of a pair of new bottles. I am looking for recommendations in terms of capacity and bouyancy characteristics.

I already own matching PST 120's, 3442 WPSI. These are great for use as singles but I wonder if they might be a bit much together. (Their land weight is kind of up there.) Moreover, I will still require a pair of tanks for use as singles during normal rec diving.

Thus there are so many options open to me that I'm a tad confused. Should I use the 120's as the doubles and get something else for rec use, or vice versa - get something else for the doubles and continue using the 120's for rec diving? (In that configuration, I like their bouyancy characteristics and the fact that I can often dive all day on one of them.)

Thanks in advance,
chris

Hi Chris
I use the 120's as twins, also I am a air pig.
They weigh less that a set of oms 108's.
But they have lasted as long as 4 hours working on the east coast
I have an isolating manifold and a reg on each post.
When I dive with a buddy I put a long hose on one first stage.
I like the idea of not having to change your tanks between dives.
I weigh 150 lbs. at 5 foot 10.
For my single tank dives I have an aluminum 90 cu.ft. at 3300 psi.
I also have 2, 50 cu.ft. at 3300 psi. aluminum tanks setup as side mounts, and carry at least one on every dive.
In my dry suit I do not need a weight belt, but I carry enough to keep my suit a little negative, just in case I have to take my kit off under water.
Hope this helps!

 

[DA Aquamaster]

An option you may want to consider, depending on your gas needs, is doubled AL80's, especially if you're not doing longer (ie, open water) run times.

Look into borrowing a set of small steel doubles for the course.

If you were closer, I would offer to loan you a set of 72s.

The idea is to have more gas than you need, but not so much that you are likely to hurt yourself, especially on boats.

I would suggest double alum 80's. 154CF is a good amount of back gas and they will be the most economical solution. You could pick up two used alum 80's for less than $200 for example. My doubles with bands and manifold weighs 96 lbs (full). You have to deal with the buoyancy shift of course. With a neoprene drysuit, thic winter thermals, dry gloves, deco bottle, reels, lights, etc., etc., etc. I use 28 lbs of lead in salt water. I'm 6' 180lbs.

I think your steel 120's would be overkill and too heavy. Obviously not an issue once you are in the water but carrying this rig around, to/from the boat/car will be a ball buster. If you were doing the Doria or U869 and wanted max bottom time/super long deco obligation then you would need this kind of volume of air. Short of that you would be more than well served with much less back gas in my opinion.

Ultimately comes down to your SAC rate though. If you have a high SAC rate you may want to consider 100's or such. Do you know your SAC rate? Do you have an idea of the profiles (depth, etc.) you would like to work to? Your instructor could help you or in fact we here could help you with an idea of the gas requirements you would need.

All of the above is very good advice. In my opinion you should select your doubles by deciding what type of diving you are going and considering your SAC rate and then using this information to determine how much gas you are going to need. While having more gas than you need is not exactly a bad thing, it is also not exactly a good thing if lugging around sets of uneccesarily large doubles leave you dragging butt, strains your back or results in compromises in your configuration (larger wing than neccesary, etc).

A set of doble 80's or similar sized steel tanks will serve you well for quite awhile. You ae goion g to have to be going pretty deep or be a real hoover to actually need the gas in a set of 120's.

If you can find them and afford them E7-100's are perhaps an excellent compromise. They offer a more or less honest 100 cu ft. at a size and weight comprarable to an AL 80.