wing question

[Scuba Steve106]

IS a Dive Rite Rec wing ok to use with double 120's?

[cool_hardware52]

IS a Dive Rite Rec wing ok to use with double 120's?

Required wing capacity is a function of the weight of your gas and the buoyancy of your exposure suit.

With only half the information it's not possible to determine if a given wing is "OK" with a certain set of cylinders.

Tobin

[RJP]

IS a Dive Rite Rec wing ok to use with double 120's?

Tobin's right of course over all, but on the assumption that at a minimum your wing needs to be able to float your rig at the surface you can do some simple math...

Tanks = -18lbs each (assuming HP, from here (http://www.diverdiscount.com/tankspecifications.html))
Plate = -6lbs (assuming steel)
Manifold/valves = -2lbs
Regs = -4lbs

Rig = -48lbs
Lift = +50lbs

Might you have another 2lbs of stuff on your rig? Light, knife, reel, etc)

:shocked2:

[cool_hardware52]

Tanks = -18lbs each
Plate = -6lbs (assuming steel)
Manifold/valves = -2lbs
Regs = -4lbs

Rig = -48lbs
Lift = +50lbs

Depends on which 120's. I have a pair of faber lp 120's that are only about -10 lbs each.

The MP fabers (-~18 full each) are a whole 'nother story.

The real take away here is people asking "What wing do I need for XX tanks?" need to do a bit more homework and understand that BC's are used for.

Tobin

[saxplayer1004]

ya, those 18lbs each are WAY off.
TECHDIVINGLIMITED.COM (http://www.techdivinglimited.com/pub/tanks.html)
the true HP120's are only about 10.

That being said, I have a friend that uses a Rec wing with LP95's and a drysuit for cave and cold wrecks with stage bottles and she's fine. The drysuit helps, but still. You want your wing to be able to hold your rig at the surface without you/exposure suit for buoyancy.
The capacity of the Rec wing should be fine, but like Tobin said, there's a whole lot of other factors in there. What Can light do you have and what does it weight, what other crap do you have on there, what plate are you using etc.

The funny thing with what is recommended for wings by a lot of the manufacturers is that buoyancy of a lot of tanks is similar.
My PST120's weight the same in the water as my buddies LP95's, as well as my PST80's

Excluding the Heisers and Fabers ridiculous mid-pressure tanks, most of the LP and HP tanks have very similar buoyancy characteristics. This is sweet because you can switch these tanks around and have minimal change to your weighting requirements.

Also with what Tobin said, you have to take accound for diameter of the tanks. You don't want wings wrapping up around your bottles, it's bad for balance.

[cool_hardware52]

Also with what Tobin said, you have to take accound for diameter of the tanks. You don't want wings wrapping up around your bottles, it's bad for balance.


This is completely untrue.

The center to center distance on doubles is set by the manifold, and modern manifolds are 215mm or about 8.46 inches.

Doesn't matter if you are doubling up 6.9" diameter 72's or 8" lp 120's the tanks will still be 8.46" center to center.

That means all these tanks will contact the divers back plate just about 4.23" inches from the center line on each side, regardless of tank diameter.

It then follows that the center panels (the part that does not inflate) of doubles wings needs to be 9~9.5" wide to avoid having the tanks trap the bladder.

Only the portion of the wing *OUTBOARD* of the point where the tanks contact the back plate is capable of "wrapping"

The issue with tank wrap is how high is the top edge of the wrapped wing with respect to the top of the cylinder.

Each side of the wing will contact one "quardrant" or about 1/4 the circumference of the cylinder, from the point where the tanks contact the plate, and the wing is free to rise vertically alongside the cylinder.


A 6.9" diameter tank is 6.9" x pi or 21.7" in circumference. 21.7/4 =~ 5.4

A 8.0" diameter tank is 8" x pi or 25.1" in circumference. 25.1 / 4 = ~ 6.3


The same wing used on 6.9" tanks will result in less than one inch more tank wrap then it would if it was used with 8" diameter cylinders.

Wings need to be sized based on:

1) The weight of the divers backgas and the buoyancy of their suit

2) Overall trim considerations where the shape of the wing may help or impede horizontal trim.

Cylinder dia is simply not an issue.

Tobin

[saxplayer1004]

Stand corrected, I've seen some real bad wing wrap on the 7.25" tanks and attributed it to that, but apparently not. Thanks for the correction. Must have been the wing. Top edge of the wings were going up just past the valve so maybe it was just a really wide wing. Don't remember what it was though. The DSS wings I have seen have almost no wrap though which is good. I had a 42lb Torus wing that I used for doubles before I got my Nomad wing. Bunch of buddies have them as well and love them.