steel 120's for side mount?

[djcheburashka]

Sm has more drag because of the relationship between the leading edge cutting the water and the outermost point of the rest of the gear.

Take a class.

As for contorting through passages-yes, some of us do that. And the big issue with no-mounting and hp-120s isn't length, it's the combination of length and weight. The concept is leverage.

Again, you need to take a class. Like high school physics.

And if you think longer, heavier tanks trim out better-if you're really amateurish at trimming them out, having really heavy ones makes it easier because then you just keep making things tighter

Otherwise, longer tanks are worse for trim, because of the whole Pythagorean theorem thing.

This time it's middle school math.

(Whatever you mean by "moment they the valve has on the pivot points ..." It's totally incoherent in your post.)

 

[victorzamora]

Sm has more drag because of the relationship between the leading edge cutting the water and the outermost point of the rest of the gear.

Literally gibberish, at best. I'm a fluid dynamicist by trade, training, and passion.

HP120s are great tanks to dive in SM with if you're tall enough for them. I'm afraid at 5'10" they'd be all over your knees and would make swimming miserable.

 

[djcheburashka]

Try it with a scooter honestly, this question of whether sm has more or less drag than bm is something that separates out the internet divers

 

[bamafan]

I guess I am an internet diver because I don't have a clue what you are talking about. If the sidemount diver is actually diving sidemount and not front mounting like many do I do not see how it could have more drag than backmount. If you look at a true sidemount diver head on in proper trim the tanks can hardly be seen as they are blocked by the arms.

As far as triming out tanks sidemount any tank can be trimmed out. Now having the tanks hitting you in the thighs is another story. I don't think there is any perfect sidemount tank. They need to be chosen for the dive.

I see you are from Miami. With your attitude are you by chance kin to G.I. III?

 

[djcheburashka]

Not kin to GI. I don't think there's only one right way to do things. At all. I do think that a lot of what passes for knowledge on the diving boards is horse kaka.

As for drag-yeah, that's what you'd think. That's what I thought too. Then I said as much to someone in a position to know better and he said I was just wrong. So I tried it.

Comparing without the scooter, I did feel like I have to work harder in sm than bm to move through the water. But that's unscientific since I switched to sm after back surgery.

I also tried it with a scooter. And, yes, sm was noticeably slower on the same scooter. No question.

I am not an expert in fluid dynamics; someone who was an expert explained the reason to me and I felt like I understood it at the time, but apparently not well enough to relate it two years later.

The way I recall it, is you draw a cone from the furthest-forward point on the diver, the point that cuts the water. The axis of the cone is along the divers' path of motion. The larger an angle you have to make the tip of the cone so the whole diver fits inside, the more drag you have. And what an sm diver gains in reduced height is more than made-up-for in increased width, in terms of how big you have to make the cone.

That's as well as I can remember the explanation, but anyway try it if you don't believe me!

And by the way, *every* serious diver I've spoken to about sm and bm who's in a position to know, *except* people on Internet forums, said exactly the same thing about the comparative drag.

 

[victorzamora]

The way I recall it, is you draw a cone from the furthest-forward point on the diver, the point that cuts the water. The axis of the cone is along the divers' path of motion. The larger an angle you have to make the tip of the cone so the whole diver fits inside, the more drag you have. And what an sm diver gains in reduced height is more than made-up-for in increased width, in terms of how big you have to make the cone.

That drag principle you're describing is accurate......for supersonic and hypersonic flow characteristics. We, as divers, are diving a wee bit slower than the speed of sound.

 

[djcheburashka]

So it turned out not to be total gibberish; definitely an improvement over 2 posts. Perhaps you want to try it before saying that I've got it wrong?

 

[maxguru]

I dove PST HP120 tanks in both backmount and sidemount for a while. They were the tall skinny tanks.

I'm 5'8". I had no problem with the length of the tanks.

The problem with the tanks is that some brands get too light when the pressure gets low. Mine were Pressed Steel tanks, which are neutral when empty.

 

[AngloFish]

I'm confused about this drag issue.. I've just recently moved to SM from BM and have noticed considerable streamlining vs BM. My tanks ride right along my sides behind my shoulders.. My shoulders have always been a drag point (like anybody else) so I'm not sure how hiding the tanks behind a drag point that already existed and can't be changed is worse than adding a huge drag point to your back? I have found finning to be much faster and less exerting (as shown by my air consumption reduction since switching) as well as a speed increase on my scooter. Prior to switching I was slightly slower than my buddy at full speed, I'm now slightly faster.
As mentioned above I think the key is actually side mounting (tucked up under the armpits and running straight down the side) vs the incorrect front/bottom mount you see people doing.

Oh and the 120 question I used to dive them as singles, great trim for a tall guy like me but definitely like water heaters with respect to weight. I know a few guys who side mount them and quite like it. They all gear up in the water though..

 

[decompression]

I think the drag issue (barring scooters/high current) is mostly a paper exercise, I move far too slow to notice much of a difference. And not sure how that minute difference would translate into modifying how/what I dive. Although I love seeing Engineers work (I is one myself, lol). However, moving 120's and no mount 120s are much more challenging than simple AL 80s.


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