What size wing do I need with this setup?

[bamamedic]

I'm just starting to plan for doubling up my tanks in preparation to take Advanced Nitrox later this fall.

I'm going to be diving with doubled LP85's in a drysuit with a single AL40 deco bottle. What size wing would I need for this setup? Was thinking either something along the lines of a 55lb wing, but I'm not sure.

Thanks for your help!

 

[String]

40lb is fine. 55 probably a little big.

 

[bryanmc57]

Here's the formula from the master himself... Tobin of DSS.
The Deco Stop

 

[micklock]

Trek wing 47lb

 

[Dive-aholic]

For someone your size, 40lb would be plenty.

 

[mpgunner]

I have a Ranger (44lbs) and thought that would be fine. But I have had situations where I wish I had more lift. In a rescue sitation, the extra would be nice.

 

[TSandM]

In a rescue sitation, the extra would be nice.

I've been able to retrieve an "unconscious" buddy in HP130s with my 40 lb wing. Where did you run into a situation where you needed more lift than that?

 

[cool_hardware52]

I'm just starting to plan for doubling up my tanks in preparation to take Advanced Nitrox later this fall.

I'm going to be diving with doubled LP85's in a drysuit with a single AL40 deco bottle. What size wing would I need for this setup? Was thinking either something along the lines of a 55lb wing, but I'm not sure.

Thanks for your help!

The "Reader's Digest" version is the weight of your back gas + the buoyancy of your drysuit with minimum gas = smallest safe wing.

2 x 85's will hold about 13-14 lbs of gas. For a 38 lbs wing to be too small your drysuit would need to be more than 38-14 = 24 lbs positive. That's certainly possible.

To require a 55 lbs wing your drysuit would need to be 55-14= 41 lbs positive, that's very unlikely.

Test your suit. Put on your undies and suit and grab a bag 'o' lead. Get into neck deep water and vent all the gas you can from your suit. Remove lead until you are just neutral. Weigh the bag of lead.

Tobin

 

[srcalDiver]

Regarding the Deco Stop analysis for a single HP100 rig, I compute that the minimum wing lift should be 32 Lbs. Here is how I arrived at that number:

- Assuming the worst case situation where the drysuit is ripped and you've lost +24 Lbs.
- Rip occurs at beginning of the dive, so the rig is -19 Lbs.
- Your weight belt holds 13 Lbs, based on the calculation in the example.
- At that point you're (-19) + (-13) = -32 Lbs.
- Then, the wing should provide slightly more than 32 lbs lift.

A smaller wing would do if you ditched your weight belt. Is that the assumption in the Deco Stop example?

 

[cool_hardware52]

Regarding the Deco Stop analysis for a single HP100 rig, I compute that the minimum wing lift should be 32 Lbs. Here is how I arrived at that number:

- Assuming the worst case situation where the drysuit is ripped and you've lost +24 Lbs.
- Rip occurs at beginning of the dive, so the rig is -19 Lbs.
- Your weight belt holds 13 Lbs, based on the calculation in the example.
- At that point you're (-19) + (-13) = -32 Lbs.
- Then, the wing should provide slightly more than 32 lbs lift.

A smaller wing would do if you ditched your weight belt. Is that the assumption in the Deco Stop example?

You are over thinking this.

If you suffer a total failure of the Drysuit you loose the 24 lbs of buoyancy the suit provided, no more. This is the buoyancy the wing needs to be able to replace.

I will note that the diver in the the TDS example is likely to need less than 13 lbs in a belt, due to compression of the undergarment from the surface to the shallow stop.

Tobin