waterway glide vs. leaderfins hyper

[Evita]

Originally Posted by Walrus

So far it seems the bad concave/edge folding problem only happens with the soft fins......
Any one out there got a stiff or medium fin with this problem ?

With the softer fins perhaps some of the monofin makers haven't changed the blade design enough between the soft/medium and stiff models and just add more or less layers for the whole blade. So perhaps the really soft fins need a minimum amount of shoulder thickness of fibreglass to stop getting the bad concave. It could partly explain why Evita seems to have no problems with folding edges having a medium stiff glide fin vs a soft/long distance, the shoulder of the fin would be a a lot stiffer.

Yes, sorry, I have to retract what I said before. I talked about this with Maria and she feels her glidefin (medium) doing the ear-folding, when she dives CWT, as you can see here Havfruerne » - Konstantvægt

Also, the Leaderfins Hyper Pro I tried last week is a medium, carbon, and it wobbled.

I'll have another go at the comparison and try to get someone to watch it. Maybe find someone with a camera...

[Evita]

Originally Posted by ADR

Here is a previous pic from Martin of his girlfriends waterway glide fin. Very Very different from what I received and I bet it is a great fin.

I was about to say yep, that's the one we got... but it isn't. There are differences in the layering of the blade, the corners and the reinforcement between the footpockets, and probably more. See pic below. Ours are numbered 269, 270 and 271. Do you know which batch hers is from? Bogdan changes them all the time...

[jome]

Originally Posted by ADR

Jome - yes I have as I train 2-3 times a week with Ant Williams. Half a stroke per 25m difference consistently for me with Ant's Hyper fin compared to mine. 5 with mine and 4.5 with his. That's a 12.5 precent difference. In most sports anything above a couple of percent is worth serious attention.

Ok, that's what I wanted to know. Although I don't think stroke count alone is a very definitive measure. It gives us a good estimate that there is a difference, but I'd still like to see comparsions of max dynamics and even more so from CW and sprint (different fins might require a little different style, but the max result might be very close in the end).

I mean the folding looks bad, yes, but are we talking "tolerable quality" or "utter crap"? Do the other properties of the fin outweigh the effect compared to a less advanced fin?

Also, what effect does technique have? Does the blade fold like that with every diver? I suspect that the already mentioned knee-issue might have some effect...Ie some divers (my self included) tend to spread the knees, which would put tension on the footpockets too. And on this type of fin, they are so protruding so far from the blade, even small tension could cause surprising effects? And I imagine a strong "leg kick" will only make things worse.

Anyway, from what I can gather, the problem does not seem to be so much for the type, but individual fins or batch. Some individuals of the same type/brand fold while others don't. For example my (very soft) Leaderfins Hyper does not, but I've seen fins of the same type that do (even stiffer ones).

I'm no hydrodynamic engineer, so I'd still like to hear Eric Fattah's comment since he's the only one who I've heard defend the v-flex - but he never told us why he thinks so...

[ADR]

Originally Posted by Evita

I was about to say yep, that's the one we got... but it isn't. There are differences in the layering of the blade, the corners and the reinforcement between the footpockets, and probably more. See pic below. Ours are numbered 269, 270 and 271. Do you know which batch hers is from? Bogdan changes them all the time...

oh dear that looks just like mine.

Why does it have to be such a lottery when buying a fin?

[jome]

Originally Posted by ADR

oh dear that looks just like mine.

Why does it have to be such a lottery when buying a fin?

You seem to be pretty handy with tools. How about you start turning the trend? It would be about time someone did it...

[ADR]

Thanks Simo however I shouldn't need to as good examples of Waterway Glide and Hyperfins are out there. It's only a matter of getting some consistency from the manufacturers.......but then again maybe that is the point you are making.

[trux]

I was pointed to this thread in another one where we discussed similar topics. I just wanted to add a small detail: the type of the bending discussed here is not concave (which would be good), it is convex (which is bad for the propulsion).

As I explained in the other thread, and as already mentioned earlier in this thread too, the concave bending (ear bends) pushes water sideways instead of backward, hence a lot of energy gets wasted.

In contrary, at a concave flexing, the resulting bend creates a cavity preventing water from escaping sideways, and pushing so more water backward than a flat blade, hence it would improve the propulsion. But again, that would be the case only if it did not prevent the blade from flexing lengthwise (like in the photos with paper sheets earlier in this thread). That can be achieved only with a good design of the fin: reinforced sides (or arms or wings if you prefer), and a softer, thinner and possibly stretchable center or even a slit. Look at the following photo to see how the resulting concave flex should look like to improve the propulsion against the plain flat flexing common at current monofins (except the ones discussed here, that bend in the wrong way):

Atomic_SplitFin_Waterflow.jpg

Of course, the slit does not need to be left empty. On my mind, much better than a simple slit, is filling it with a stretchy material (profiled rubber foil) just like some bi-fin manufacturers do - for example Mares at the Volo Race fin (but there are some others too). At every kick, it creates a very efficient concave shape with a better efficiency than a flat blade, where much more energy is being lost laterally.

MaresFinsVoloRace410313.jpg

The same principle would apply at a monofin, of course too. You just need to find the right material, geometry, and stiffens (which needs to be variable across and along the blade).

[Fondueset]

I have been studying some of the pictures I have taken of fish and you can see the type of convex flex trux describes. The Rays along the outside of the fin support the edges - it also appears there is a bit more support toward the center - enough to make a little less convexity there - though still some. These fish also have a higher aspect ratio, of course - than a traditional monofin - but less than the lunocet or fish like tuna. It would be interesting to build a fin with a higher aspect - but with re-enforcement along the leading edges and material layered so that it would function as above. You would want it to go slightly convex - more toward the edge and not too much.

[trux]

I think you mean concave, not convex, Fondueset. These two terms get often confused. There is a picture here showing the difference

image credit © STSCI.edu

[jome]

Originally Posted by ADR

Thanks Simo however I shouldn't need to as good examples of Waterway Glide and Hyperfins are out there. It's only a matter of getting some consistency from the manufacturers.......but then again maybe that is the point you are making.

Heh, that was exactly the point I was making

There really isn't much consistency in quality as far as I can see...

Maybe for my next fin I'll look into Binfins, heard good things about those. Unless of course the lunocet is ready by then

[Fondueset]

Concave relative to the direction of force then Like the split fins but without all that loss. For some reason I dyslexicized the terms.. possibly the result of doing three things at once - anyway - What trux said and thanks.

[jome]

By the way I saw some of Japanese diver with a carbon fiber fin that had been cast into a concave shape (concave for the down kick obviously), in the Sharm WC. Can't imagine it working very well though, but looked interesting

Andy, how about sacrificing another fin for science? Cut out a large chunk in the middle in a v-shape and replace it with a flexible material, maybe reinforce the edges a little...Perhaps put a little split in there as well?

I'd do it if I had an extra fin

[trux]

Originally Posted by jome

By the way I saw some of Japanese diver with a carbon fiber fin that had been cast into a concave shape (concave for the down kick obviously), in the Sharm WC. Can't imagine it working very well though, but looked interesting

Yes, I agree. Although I did not see it, I suspect it may be rather a hindrance because if you have it pre-casted in a concave shape, without the blade being stretchable, the blade loses its lengthwise flexibility (as you can see in ADR's photos with a paper sheet) and rather moves the water downward (at the down kick) instead of backward.

[monkeyhatfork]

evita- how long ago did you get your glide fin? yours looks very similar to the pics of mandy rae at her 88m dive and also some i've seen of carlos costa, but recent pics if seen-including the product section on the waterway site show a blade almost identicle to my ww1 med, wonder if they have made a permanent change? or if they just use model 1 blades if they run short on the other

[Evita]

I got mine in November 2006 and already in December at the WC in Hurghada, Bogdan had brought a new version (slightly shorter blade and full corners). He said that he experimented with the glidefin all the time, and true enough, at Nordic Deep in August last year, I saw yet another version with the dealer there, but I can't tell you how it was different. Being a girl, I only remember that it had a different colour (blue, not pink) ;-) but from now on I will pay more attention to the different layering, position of foot pockets, shoulder reinforcement etc that this thread is bringing up. Interesting!