Tips on starting diving doubles

[rx7diver]

My independent heavy steel double 7ltr,s ...

Why "heavy"? (What are their physical characteristics?)

TIA,
rx7diver

 

[Celt]

Why "heavy"? (What are their physical characteristics?)

TIA,
rx7diver

That 7ltr tank is negative empty in fresh water.

 

[rx7diver]

That 7ltr tank is negative empty in fresh water.

Okay, thanks. I remember the old Scubapro (Faber, I think) "Slimline" cylinders. Narrow (6.0" OD, maybe), 63 and 72 cu ft cylinders having a service pressure of 3,000 psig + 10%, IIRC. Neat cylinders, except negative when empty. I always believed that they (especially the 72's) would make a neat set of doubles for diving dry.

rx7diver

 

[mr_v]

@SouthernSharktoothDiver - why would you want to learn how to dive doubles by reading random internet posts? You're probably less than 90 mins away from Scuba John's in Lexington. Hit them up. They're good people and can help you.

 

[rx7diver]

That 7ltr tank is negative empty in fresh water.

Okay, thanks. I remember the old Scubapro (Faber, I think) "Slimline" cylinders. Narrow (6.0" OD, maybe), 63 and 72 cu ft cylinders having a service pressure of 3,000 psig + 10%, IIRC. Neat cylinders, except negative when empty. I always believed that they (especially the 72's) would make a neat set of doubles for diving dry.

rx7diver

Home for lunch, so I pulled out an old Scubapro catalog (the 1986 catalog).

1. The 60.6 cu ft Scubapro "Slim-Tank" was 22" tall with 6" OD, weighed 22.7# sans valve, and had service pressure 3,000 psig + 10%. Buoyancy sans valve in seawater was -7.8# (full) and -2.8# (empty).

2. The 71.4 cu ft Scubapro "Slim-Tank" was 25.4" tall with 6" OD, weighed 26# sans valve, and had service pressure 3,000 psig + 10%. Buoyancy sans valve in seawater was -8.4# (full) and -2.5# (empty).

rx7diver

 

[Celt]

Home for lunch, so I pulled out an old Scubapro catalog (the 1986 catalog).

1. The 60.6 cu ft Scubapro "Slim-Tank" was 22" tall with 6" OD, weighed 22.7# sans valve, and had service pressure 3,000 psig + 10%. Buoyancy sans valve in seawater was -7.8# (full) and -2.8# (empty).

2. The 71.4 cu ft Scubapro "Slim-Tank" was 25.4" tall with 6" OD, weighed 26# sans valve, and had service pressure 3,000 psig + 10%. Buoyancy sans valve in seawater was -8.4# (full) and -2.5# (empty).

rx7diver

I just had to measure my 7,s. There 23in tall and 5in O.D I believe ye call them 50 cuft. I think there 3kg negative full and .8kg negative empty but those figures could be wrong, I just know there heavy when empty and what lead I need with them. My main use for them is as singles shallow or deco bottles.

 

[old frogman]

When we were approaching the water, we would grab one riser, and with the other hand release the Capwell disconnect. Then, holding the riser, we would release it upon entry into the water. That effectively threw the entire side lines over the ‘phone, and deflated the canopy in one motion. It also placed all those lines way away from us to lessen the potential for entanglement.

In one training jump, when I was just beginning, I had a weird situation happen. I had a half hitch over both sides of one riser group, meaning that I could not pull the pins and use that side for steering as they were effectively tied together. Upon entry, I couldn’t release those lines easily either, and got dragged across the water some distance, and then when trying to get out, got entangled in the suspension lines. I did not panic, but got royally chewed out by the instructors for that one. They asked “What would you do in a mission,” whereupon I pulled out my non-issue Sportsways dive knife, which I had sharpened to a razor edge, and said I’d simply cut the lines. But I didn’t want to do that in a training situation as it would effectively destroy the ‘chute. They then backed off.

We had two different configurations of the Capwell release, and the older one in this photo had the cover, then under it was a release that involved two pinch buttons that released the riser group. Later, with the S-17 parachute, that was replaced by a wire loop, which was much easier to release. (I’m capitalizing the “Capewell” as I think that is the inventer’s name.).

Parascuba Jump-Okinawa-1 by John Ratliff, on Flickr
In this photo, the right riser group’s Capwell release has been activated, and the PJ is holding the riser group in his right (probably dominant) hand. As soon as he hits the water, he releases his grip.

Here is what we looked like prior to the jump.

Rick in Parascuba by John Ratliff, on Flickr
This is Richard “The Bagger” Harder in full parascuba gear. I’m in the smaller photo. Unfortunately, Rick has passed of a heart attack while training for a firefighter competition, stair climbing in full firefighter gear for time. Note the smaller doubles. I loved those doubles, and have a set I cannot fill because the 1/2 inch manifold won’t seal anymore (too many times taken off and on, due to the need for a visual inspection yearly).

SeaRat

Very interesting. Releasing one Capewell on water entry makes sense. I used that technique on the MC1 in strong winds. The S17 with the TU modification appears similar to the MC1. I noticed you carried two knives. The knife that appears to be located near/or on the reserve chute, was that a riggers knife (orange handle with flick blade and hook blade)?

 

[John C. Ratliff]

[quate=old frogman]Very interesting. Releasing one Capewell on water entry makes sense. I used that technique on the MC1 in strong winds. The S17 with the TU modification appears similar to the MC1. I noticed you carried two knives. The knife that appears to be located near/or on the reserve chute, was that a riggers knife (orange handle with flick blade and hook blade)?[/quote]

Here's what the riser release looks like just after releasing the riser. Note the group is being thrown over the canopy.

Now, about the knife(s). Usually, I did not jump parascuba with a knife on my reserve. I had my leg knife, and that was enough. But for a tree jump, we needed the knife on the reserve because our sheath knife would be covered by the tree jump suit. The knife was not a rigger's knife, but a regular issue survival sheath knife with one side a cutting edge and the other serrated. It would be potentially used to cut a line or two that were over the canopy, cutting it into two or three smaller opened bubbles. Also, for those jumping a T-10 (without steering holes) a knife could be used to cut the back two suspension lines on either side (4 total) to give a "bubble to the canopy and some forward air speed.

I forgot to tell you that I have a set of twin AL 45s that are manifolded with the newer USD doubles manifold. That manifold is a solid piece of brass, and getting the second cylinder onto it by myself as a hassel.

SeaRat

 

[happy-diver]

These Fabers optioned at either 3364psi, 55cf, 5.5 inch, or 4351psi 70cf, 5.5 inch, each

are quite comfortable

Especially with that OMS 32lb single tank wing