Streamlining my gear

[Rhone Man]

No, reducing drag "pays the biggest dividends" at the highest speeds, since drag increases as the square of velocity.

It may be a matter of relative perspective, but I always think reducing drag pays biggest dividends when I am swimming into a ripping current. This tends to result in very slow speeds on my part, but I understand what you are saying!

 

[Blackwood]

Mossman -- due to the difference in density, water vs. air, the resistance one feels when playing "airplane" with your hand at 60 mph in a car is about the same amound of resistance one gets at swimming at a normal pace (approx. .5-.75 kts). Every bit of extraneous stuff that hangs out sucks energy that YOU provide.

I know it's early so I could be off, but my math shows you'd have to be going 2.1MPH in water to create the same drag as an equivalent object moving through air at 60MPH.

ok i did it. 3.9 sec 0-60 with hands on wheel, 3.98 with 1 hand - driver error? yes those are real times, my buddy just got a very nice new, very expensive toy and it gives off ZERO emissions - can you guess what i am? sorry to thread jack

Tesla Roadster?

If so, don't neglect the emissions related to the mining and burning of coal to generate electricity

 

[vladimir]

It may be a matter of relative perspective, but I always think reducing drag pays biggest dividends when I am swimming into a ripping current. This tends to result in very slow speeds on my part, but I understand what you are saying!

Yes, for the purposes of this discussion, when you are making no progress swimming into a strong current you are going (relatively) fast. And that usually does inspire me to pay extra attention to my trim, etc.

 

[TSandM]

I didn't mean to provoke a hailstorm with my comment, and no, I'm sure no one will notice the difference in drag from eliminating a single hose. But I think most of us who dive dry and wet in similar water have noticed that you are more streamlined and efficient in a wetsuit -- and that's a pretty subtle difference, considering that you're still a big object with a big tank on trying to force itself through the water. The difference is certainly very noticeable when you are scootering! For this reason, I don't think it's unjustified to cast an eye over one's equipment to figure out where it can be made neater. It doesn't cost much, if any money, makes it easier to move through kelp or enclosed spaces, and probably pays off in increased efficiency -- which means longer dives on the same amount of gas. Anybody not want that?

 

[fjpatrum]

It may be a matter of relative perspective, but I always think reducing drag pays biggest dividends when I am swimming into a ripping current. This tends to result in very slow speeds on my part, but I understand what you are saying!

Well, in terms of "relative speed" it's the same thing, right? Velocity, is a vector after all, not just a magnitude.

I haven't spent a lot of time under water at this point. I do spend a lot of time in the air though, and anything you can do to decrease drag is going to be helpful. Is it necessary, probably not for most people. It is still helpful though.

 

[Teamcasa]

...For this reason, I don't think it's unjustified to cast an eye over one's equipment to figure out where it can be made neater. It doesn't cost much, if any money, makes it easier to move through kelp or enclosed spaces, and probably pays off in increased efficiency -- which means longer dives on the same amount of gas. Anybody not want that?

I agree with TSandM.
For me the main reason for streamlining is reduced entanglements but it's the whole underwater drag issue that gets all the attention. Let me break it down with high level math:

((Loose hoses + other floopy bits)*Dangling gear) + other entanglement hazards) = a really sucky dive risk ratio of 98%
((streamlining + I look cool factor) + A Scuba Diver's typical underwater inherent drag) = 4 or 5 more breaths of a AL80

 

[vladimir]

I didn't mean to provoke a hailstorm with my comment, and no, I'm sure no one will notice the difference in drag from eliminating a single hose. But I think most of us who dive dry and wet in similar water have noticed that you are more streamlined and efficient in a wetsuit -- and that's a pretty subtle difference, considering that you're still a big object with a big tank on trying to force itself through the water. The difference is certainly very noticeable when you are scootering! For this reason, I don't think it's unjustified to cast an eye over one's equipment to figure out where it can be made neater. It doesn't cost much, if any money, makes it easier to move through kelp or enclosed spaces, and probably pays off in increased efficiency -- which means longer dives on the same amount of gas. Anybody not want that?

This is a fairly modest claim, and it seems reasonable to me. Scootering should magnify the effect of drag. The wetsuit/drysuit difference is probably (I surmise) due to increased material (and therefore friction) in contact with the water, rather than a larger cross-section, and is therefore not analogous to protruding hoses or consoles, for example.

 

[Blackwood]

This is a fairly modest claim, and it seems reasonable to me. Scootering should magnify the effect of drag. The wetsuit/drysuit difference is probably (I surmise) due to increased material (and therefore friction) in contact with the water, rather than a larger cross-section, and is therefore not analogous to protruding hoses or consoles, for example.

Drag is proportional to the product of area and the drag coefficient, but really that's a cart before the horse scenario.

In reality, drag and area are measured and CD is calculated. Going forward, that CD can be used only if the reference area represents the same area as used in the initial calculation.

In other words, if I have a tube, measure the drag and compute CD based on the circular cross section moving through the water, I need to use the circular cross section moving through the water for other calculations for that CD to be applicable.

Most of the time, frontal CD and area are used.

 

[Mossman]

This is a fairly modest claim, and it seems reasonable to me. Scootering should magnify the effect of drag. The wetsuit/drysuit difference is probably (I surmise) due to increased material (and therefore friction) in contact with the water, rather than a larger cross-section, and is therefore not analogous to protruding hoses or consoles, for example.

There's a larger cross-section too. That added air has to create some extra volume, so the drysuit diver will be at least slightly "bigger" than a corresponding wetsuit diver, more so with bulky undergarments. (And there's an extra LP hose too, with all the drag that creates!)

What I mainly notice when diving dry, however, is it's simply harder to kick because one has all that extra surface area drag and increased material friction to move through the water with each stroke.

 

[rx7diver]

Antagonist,

In post #5 in this thread, I suggested some ways to streamline your BCD-based rig. I was servicing my rec gear just now and decided to take a few pics to illustrate.

Now, this setup isn't nearly as slick as the one I posted a few months ago (of my SS Freedom Plate with harness and singles wing), but it "ain't" bad. In fact, if I don't need to carry a large back cylinder and/or a buddy bottle and/or a canister light, and if I am wearing at most a thin exposure suit in fresh water, I actually prefer this Scubapro Stab Jacket setup for rec diving to moderate depths.

Hope this helps.

Dive Safely,

Ronald