First dive with twins.

[RTBCAT]

Hi I have been looking around the site and could not find the information I was looking for. A buddy and I just did our first dive with twins today. Alomst like being a open water student again that might be going to far but you know what I mean. I am diving dry (Bare ATR Light) with two Cat AL S80"s Oms manifold and bands Dive rite stainless backplate and Oxycheq 70 lbs dual bladder wings. Was using 30 lbs still had 1900 psi at the end of the dive. I know that I have to dive the tanks almost empty to see if I have enough weight but anyone who is diving a similar setup any input would be great. My buddy is diving with a bcd. Forgot the name of the bcd, somthing Tech without a manifold is using a soft plate.

 

[matt_unique]

Hi I have been looking around the site and could not find the information I was looking for. A buddy and I just did our first dive with twins today. Alomst like being a open water student again that might be going to far but you know what I mean. I am diving dry (Bare ATR Light) with two Cat AL S80"s Oms manifold and bands Dive rite stainless backplate and Oxycheq 70 lbs dual bladder wings. Was using 30 lbs still had 1900 psi at the end of the dive. I know that I have to dive the tanks almost empty to see if I have enough weight but anyone who is diving a similar setup any input would be great. My buddy is diving with a bcd. Forgot the name of the bcd, somthing Tech without a manifold is using a soft plate.

As you know there are so many variables to determine the weighting. I'm not familiar with your suit (neoprene, crushed, trilam)? What thermals are you wearing? Weezle Extreme's or thin DUI jumpsuit, etc.? What gear do you have on your rig in terms of reels, lights, etc.

When I wear my winter thermals (double layer DUI fleece materials), single deco bottle, two lights, two reels, two lift bags, etc., etc. I wear 28lbs of lead. This is with a DR SS BP, Classic Wing, alum 80 doubles. Without the gear listed above I wear 33 lbs. (Winter thermals, doubles with no other gear).

--Matt

 

[skeet]

How do you like the Bare ATR Light? Used it long? Any good -bad comments? I purchased one last week, 4 dives in it.

 

[roakey]

Was using 30 lbs...

How much weight to you wear with a single? Note that going to doubles typically requires you to *drop* weight when compared to a single, or leave it the same...

Roak

 

[DEEPLOU]

Hi I have been looking around the site and could not find the information I was looking for. A buddy and I just did our first dive with twins today. Alomst like being a open water student again that might be going to far but you know what I mean. I am diving dry (Bare ATR Light) with two Cat AL S80"s Oms manifold and bands Dive rite stainless backplate and Oxycheq 70 lbs dual bladder wings. Was using 30 lbs still had 1900 psi at the end of the dive. I know that I have to dive the tanks almost empty to see if I have enough weight but anyone who is diving a similar setup any input would be great. My buddy is diving with a bcd. Forgot the name of the bcd, somthing Tech without a manifold is using a soft plate.

@1900psi were you still neg?
Were you diving salt or fresh?

Matt noted other variables also.

I think it is going to be more a matter of tial and error. (for me though rather be too heavy than too light)

How much weight to you wear with a single? Note that going to doubles typically requires you to *drop* weight when compared to a single, or leave it the same...

Roak
Yesterday 10:55 PM
How much weight to you wear with a single? Note that going to doubles typically requires you to *drop* weight when compared to a single, or leave it the same...

This would be true for steel (or any tank that is still negative when empty), but AL 80s are almost 4 lb Pos when empty. Thus a single 80 empty is 4 lb pos, but double 80s are 8 lb pos.

 

[DA Aquamaster]

I'd agree the best approach is to start with an adjustment of your single tank weight requirement taking into account the bouyancy of two 80's at 500 psi rather than one as well as the negative bouyancy of the bands, manifold, and second regulator.

The change is probably not as great as you think as the negative bouyancy of the bands, reg and manifold are going to cancel out the approximately 4 lbs positive bouyancy of another empty 80.

Given your "Almost like being a open water student again" comment I'd guess you would be over weighted with empty tanks which translates to being badly overweighted with full doubles. Normally a pair of AL 80's are about as stable as it gets and when they are near empty, it is like diving under a blimp as the center of lift is quite high compared to a pair of negatively bouyant steel tanks.

Another difference is that with the increased swing weight of doubles (even when properly weighted) you need to rely on the BC for bouyancy as using the dry suit alone will result in too much air in the suit which conrtibutes to that "Almost like being a open water student again" feeling. The problem is both that you have too much air in the suit and the lift is all at the bottom and will be trying to get to the top. Carrying a good portion of the air in the wing solves both issues.

Normally on my first dive in a new configuration I will just freeflow the excess air off at the end of the dive to get it down to 300-500 psi and do the bouyancy check and adjustment right there at the end of the dive. It saves time, confirms your bouyancy calculations and virtually guarantees a better second dive.

 

[RTBCAT]

Thanks for all the input I know there is going to be a learning curve when starting out with new gear. Skeet the dry suit is great have had no problem with it, you may find if look straight up with a latex seal some water may shoot down your neck. Will be doing lots of easy dives to get used to it. Diving with a single 80 at this time of year I use 35 lbs in salt water and can drop 5 lbs in the summer.

 

[skeet]

Good to hear.

 

[roakey]

How much weight to you wear with a single? Note that going to doubles typically requires you to *drop* weight when compared to a single, or leave it the same...

Roak

This would be true for steel (or any tank that is still negative when empty), but AL 80s are almost 4 lb Pos when empty. Thus a single 80 empty is 4 lb pos, but double 80s are 8 lb pos.

Yes, you're +4 with another AL80, but as DA Aquamaster correctly points out, when you add the crossover, bands and regulator in, that a handwaving 4 pounds, hence my "...or leave it the same..."

Roak

 

[drbill]

You know it has always been a fantasy of mine to dive with twins. I dated identical twins, some 25 years apart of course. Oh, maybe you are talking about doubles here? Never mind...

Dr. Bill