Decide between wings
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Since you need it spelled out: It was a hypothetical question that supposed that two wings had the same capacity. It didn't suppose that they were RATED at the same capacity. It supposed that they ARE the same capacity. Since I'm spelling here, that means that most people understand that it is implied, in this hypothetical question, regarding two hypothetical wings, that their capacity was determined to be the same by measuring each wing's capacity the exact same way and found that they are the same capacity when being used in an identical (save for the change in wings) scenario.
ams511
Contributor
Stuart, as others have mentioned there are no industry standards to determining the lift of a wing. Tobin was mentioning how he measures his products which could be different than how another manufacturer tests their products. If I remember correctly, Dive Rite changed their testing procedures and lowered the advertised lift of their wings while the size remained the same. So the difference between a 30 lb and a 25 lb wing could be the testing procedure. I would think the liability for a manufacturer is much higher if they advertise a wing as having 30 lbs of lift when it only has 25, than advertising a wing that has 25 lbs of lift that really has 30.
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cool_hardware52
Contributor
The reality is most wings are produced in job shops. They work to a pattern and bill of materials. If there is any capacity testing done it's likely in the "free" state, i.e. not mounted to anything, If you dropped a back plate and cylinder in the middle of the production floor most would have no idea what they were or how they interface with the wing.
That doesn't mean wings produced via job shops are bad, it's just the reality. AFAIK there are two wing brands where the goods are actually designed and manufactured under the same roof, DSS and Halcyon, my apologies if I missed somebody.
We decided to test for capacity in the "worst case" , plates with the least included angle, largest diameter cylinder, weight plates mounted etc. Most deviations from this, steeper plate bends, use of STA's, smaller cylinders etc. reduce the constraints.
I suspect that other wings have been tested in the free state for the simple fact that you won't find a back plate and or cylinder in most sewing job shops.
I just finished testing a custom application for one of our Rebreather wings, the RB40. This particular RB (back mounted counter lungs) has a wide flat back plane that actually is bent slightly towards the diver. When fitted with a shallow bend DSS back plate there is little space between the back plate and RB back plane. A "40" lbs wing tested at 27 lbs following the protocol I listed above.
This is a reminder to verify that whatever wing you choose is capable of floating your rig with full bottles, and that you should test the buoyancy of your exposure suit and make sure it is less than the actual lift offered by your wing / bc *in the configuration* you will actually be diving it.
Tobin
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ams511
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I meant to say ...than advertising a wing that has 30 lbs of lift that really has 25. My point being that from a liability standpoint it is better to have more lift than advertised than less.
None taken. I fixed the post in question.
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Sorry, I misunderstood. I thought you were saying it's better to advertise llow and it be higher than the opposite.
---------- Post added August 18th, 2015 at 01:58 AM ----------
I think we are on the same page but perhaps got lost somewhere in translation.
---------- Post added August 18th, 2015 at 01:58 AM ----------
I think we are on the same page but perhaps got lost somewhere in translation.
dmaziuk
Contributor
Can you please quote the post where I asked that?
I posited two wings of the same lift - one horsehoe and one donut - and asked if the donut would be slightly more streamlined.
In the build-up to my question, I posted one of my axioms upon which my theory was built. To wit, two wings of identical lift must be of identical internal volume. I expressed it as a question seeking confirmation, but that was indeed rhetorical. The axiom must be true. If they didn't have the same internal volume, they would not displace the same amount of water and, therefore, would not have the same lift.
You responded to that with some inane comment about flashlights. Your comment implied that two wings of identical lift could have different internal volumes, which is simply wrong. Well, unless you use different densities of "water" when you compare the lift of the two - which would be kind of stupid to do in the context of the question (would a donut be more streamlined than a horseshoe).
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