Wing Choices?

[cmalinowski]

Nah ... if you're planning to dive both singles and doubles, it's better to have two plates and set them up as completely separate rigs. Swapping out plates and wings all the time is a pain ...

... Bob (Grateful Diver)

Good plan. I think that's what I'll do. Since I have that extra plate and webbing lying around, I might as well put it to use. Of course, that means I'm going to have to go purchase another one to have lying around not in use

 

[cool_hardware52]

Tobin,

My sense is that if divers follow our recommendation(s) and use a shell drysuit, then the above statement is likely inaccurate. Take for example the typical So Cal diver. If they dive wet it's normally along the lines of a 7 mil westuit, possibly with a vest added for warmth. Juxtapose that against a shell drysuit and C-4 undergarment. I think you'll find that the 7 mil diver is notably more bouyant then the shell suit, and thus require additional weighting. Moreover, most wetsuit divers need to weight themselves for the 10' stop when the neoprene is at it's most bouyant. As a result of this dichotomy, more often then not divers tend to be over weighted for the vast majority of the dive to allow for the ability to hold the 10' stop.

I do agree with the rest of your analysis and believe that it is important for divers to appreciate the kind of diving they are likely to do and purchase equipment that compliments that choice.

Regards,

Micheal,

I agree that a shell drysuit might be less buoyant than some neoprene wetsuits. However in many cases the diver moving to a drysuit from a wetsuit does need more ballast, at least initially.

Part of the reason is the new drysuit diver may not have mastered the suit, and may not be able to vent as completely as a more experienced dry suit user. This eventually cures itself.

The other part of the reason is the lenght of exposure. Dives that would have been difficult to endure in a wetsuit become possible in a Drysuit, but at the "expense" of greater insulation. More undies equals more ballast.

I'm not making any recommendations regarding Drysuit types or undergarments, my preferences are in line with yours. I only wanted to make the thread starter aware that changes to his exposure suit could likely effect his wing requirements.

Regards,


Tobin

 

[Makin Raider]

In response to the expense of an extra BP, I've pick up two of these and they have been in excellent shape and fit Halcyon Eclipse and Explorer wings perfect.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=7247218594

Mark

 

[Splitlip]

First thing you need to do is determine how much lift you need. Once this is known you can narrow down the choices a bit.

The weight of your rig can be estimated reasonably closely, add the weight of your tank and plate + regs, + what ever else you might have on the rig, can light etc.


Regards,


Tobin

Tobin:
You mean (negative) buoyancy of the tank, not the weight, right?

 

[cool_hardware52]

Tobin:
You mean (negative) buoyancy of the tank, not the weight, right?

Of course. Sorry if I wasn't clear. All the "weights" should be their effective in water weight, we are after all trying to estimate how much wing is required to float the rig in the water, not how large a helium ballon we need to float the rig over dry land.

Lets look at a 6 lbs SS back plate. SS is ~495 lbs / cuft. Water is ~63 bls / cuft

SS in water is 495-63 or 432 lbs / cuft 432/495 = .87 A 6 lbs back plate will weigh 6 x .87 or a little more than 5 lbs.

You can see for the high density materials like SS and Brass there is a 10-15% change when submerged in water, so for the purposes of this estimate you can use the "dry" weights and not be too far off.

It's different with tanks, first they constitute a great percentage of the total mass, and becasue they are hollow their density is much less.

There are numerous tables all over the net that can provide the buoyancy figures for tanks.


Tobin

 

[Splitlip]

Of course. Sorry if I wasn't clear. All the "weights" should be their effective in water weight, we are after all trying to estimate how much wing is required to float the rig in the water, not how large a helium ballon we need to float the rig over dry land.

Lets look at a 6 lbs SS back plate. SS is ~495 lbs / cuft. Water is ~63 bls / cuft

SS in water is 495-63 or 432 lbs / cuft 432/495 = .87 A 6 lbs back plate will weigh 6 x .87 or a little more than 5 lbs.

You can see for the high density materials like SS and Brass there is a 10-15% change when submerged in water, so for the purposes of this estimate you can use the "dry" weights and not be too far off.

It's different with tanks, first they constitute a great percentage of the total mass, and becasue they are hollow their density is much less.

There are numerous tables all over the net that can provide the buoyancy figures for tanks.


Tobin

Ok, so how big a helium balloon would I need.
I knew what you meant. (my tanks weigh 38#s but have a negative buoyancy of 7.75 #s.) Just making it clear for the any new folks who might pop in. I did not realize though I was in the DIR forum when I jumped.
But your physics brings up a question. If the specific gravity of water has such an effect on solid steel, it would affect regs and such even more.
I am thinking I'll just put my entire kit in a couple mesh bags and see how much weight it will take to sink it. (I am shopping a new wing myself)

 

[cool_hardware52]

Ok, so how big a helium balloon would I need.

Helium in balloons is a terrible waste:11:

I knew what you meant. (my tanks weigh 38#s but have a negative buoyancy of 7.75 #s.) Just making it clear for the any new folks who might pop in.

Fair enough, I did get sloppy.

But your physics brings up a question. If the specific gravity of water has such an effect on solid steel, it would affect regs and such even more.

Less actually. Mos regs are brass, the Specific gravity of brass is ~8.6, meaning it weighs about 540 lbs per cuft. Brass will be 1/8.6 = ~11% "lighter" when submerged.

I am thinking I'll just put my entire kit in a couple mesh bags and see how much weight it will take to sink it. (I am shopping a new wing myself)

Your kit, less your exposure suit, is likely negative, better tie a line on to the bag.


Tobin

 

[Splitlip]

Your kit, less your exposure suit, is likely negative, better tie a line on to the bag.


Tobin

I am getting punchy. As soon as I typed it realized it. One bag with the suit, harness, regs etc but no tank. x pounds of weight to sink the bag plus the negative buoyancy of the cylinder would give a close approximation?

 

[cool_hardware52]

I am getting punchy. As soon as I typed it realized it. One bag with the suit, harness, regs etc but no tank. x pounds of weight to sink the bag plus the negative buoyancy of the cylinder would give a close approximation?

Your wing needs to do two things, float your rig without you (our your positive exposure suit) in it, and compensate for the loss of buoyancy of your exposure suit.

What I want to know is the positive buoyancy of the suit, and I want to estimate, or in your case actually weigh, the negative buoyancy of your rig.

In cold water single tank diving it would be unusual for the weight (negative buoyancy) of your rig to be greater than the initial buoyancy of your suit.

You can estimate with reasonable accuracy the weight of the rig.


Tobin