Fiberglass Hockey Fins

Bugger, Atapene got in an essay while I typed three lines!

Duck is correct and also incorrect. Any power that doesn't transfer at all (movement within the pocket for instance) is wasted. Where he is partially incorrect is that movement that is delayed (through soft footpockets, etc) is not lost completely. His suggestion that this reduces performances is definitely correct.

How's this for a concrete example. A freediver friend got a new monofin recently. The footpockets fitted, but his toes had some vertical and horizontal movement. Simply by adding extra hard rubber in under his toes and to the side dropped his strokes/length from 5 to 4 at the same pace and effort. That is significant.

There are definitely other major performance characteristics, but footpockets are often overlooked, despite their importance. Personally, I think you need better the improved fit of custom pockets so you can increase the stiffness of the footpockets themselves. Their flex criteria are more important.

I can only speculate on my past experiances, surely I would need to experiment with my footpocket to get some hard results.

While making my new fin, I became very closely familiar with our old alas, materials, quality of tooling and attention to detail in the production. To my surprise, all this is only marginal at best of my judgement, leaving me with some strange looks on my face... The feel and performance of alas is unproportionally excellant, compared to how unperfect they are made.(I'm talking about graphite ala, the black's are even worse) But a salute goes to the main designer, no question about it!

But here's my thoughts about footpocket. First, the footpocket should be customised only for the part of enclosement, that is for the usual part of fingers all the way to heel, but no further. The molded custom made footpocket presents a few new questions. In my view, such a design would need to have 2 different types of material used. One for the fin, as it needs a specific hardness and another, softer material for the contact with skin-foot. That goes only to the inner part of the footpocket, not the whole part of the footpocket - outer side would still look as it is. This softer material should be thin, not to interfere with forces projected on the fin, but to allow some comfort level to the foot.
Basically from finswimming, I can conclude that best forces are applied through extremly hard fit to the foot, something that has to be compromised with comfort in uwh, for the reasons of manuverabillity, and longer wearing times.
This I hope I can achieve by using custom molded footpocket, and by that maximise the grip, while the fin would press against the foot evenly, but not press as much as with finswimmers-mono footpocket.
The part at the heels could be also customised further, as when or if the player would like to have a harder grip, this would be done with smaller heel radius, like with finswimmers heel strape-belt. But If I want to make it this way, I'd probably need to put some free spacing at the point of the fingers, with conically designed shape to allow for harder fit to happen without compressing the fingers at the tips. Then again, I might not need to change anything.

@atapene - What you are thinking, might present a problem. Although, one's feet are able to move more becouse of material of the fin, and not so much becouse of free space in the footpocket. Leaving just a little spacing in front of the fingers, would probably solve this potential issue, probably without any bad sideaffects, with only marginal work on my part, when doing the fin. This is what I call fine tunning the mold, but for molded footpocket it would be done once - I mean, I would know how to remake each mold, and it would be proportional for all other players molds.

Well, these are my start ideas... as I said before, such design could be optimal without any changes, or it may need some adapting. I need to test it first... and not only me! One thing that I dont doubt about, is that custom mold can be done, without so much hustle on my part, that I would have to put up some crasy price tag for it. For now, I'm still fighting with the normal fin problems!

@duck - dont you go sending me any of that porcelain feet of yours! If this thing is to work, the mould would have to be made under correct position, and I dont know what that is, yet. And ... I cant use porcelain! Pre-mentioned skin-mold would have to be done right and shipped over to me, or my ass would need some serius air miladge. Anyway, this custom footpocket solution is only intended&needed for the top-end players.... worlds should do!

@freedivenz - How did it go with monofin? Have you tried it? And I agree with your upper assesment completly.

that 5 to 4 stroke improvement is pretty impressive, i'm amazed, i really wouldnt have thought something so small would have made such a big difference.

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it's more polite on the grating than on the subs bench

Bear in mind, this was with a medium stiffness (v. stiff by freediving standards!) monofin. The guy in question is quite a fast swimmer (ex-olympic development squad for swimming, so he likes going quick!) and was training in the pool for speedy constant weight ascents. A monofin displaces so much water that small amounts of efficiency loss can mean big problems. Another example of this is another swimmer that dropped half a stroke per length just from a monofin with five degrees more angle on the blade.

As for my timetrial with a mono, that's the plan for practice on Sunday

How about just a little insight and common sense.

Most of the big bladed fins work good for deep slow kicks, usually good for surfacing from 30+ meters. I may be wrong here, and perhaps a Physics Major could explain it better, but I believe fins are designed to maximize the result at a particular cadence which is related to the kick range, length of blade, and flexibility of the material. Any lesser cadence and you get less push, any more and you lose the designed flow resulting in less push for the effort (possibly caused by the formation of eddys where you don't want them which would slow you down). Smaller bladed fins are designed for faster cadence using the same relations. Somewhere in the middle is more than likely the optimum. People's incorrect thinking and willingness to pass it along without question is what skews most hockey players' opinion. You probably heard from someone during your early years that you needed a bigger fin. They were probably told the same thing. And when you put on the bigger fin you probably went faster so you bought into it. I'd guess you went from something wimpy to something decent though. But the fact is you need one that fits you. Not just your foot, but your style of kick, your cadence, and the range of your kick.

To validate this all you have to do is look at boats. If that were not true, propellers for boats would all be the same. But they have different diameters and pitches. The simple reason for this is boats are designed different from one another. A different waterline, a v-hull or flat-bottom, different weight, motor size (power and rpm), just to mention a few. Just like people no one is exactly the same (except maybe twins). If you want to improve the speed of your boat you can't simply put a bigger prop on it and be done. A bigger prop will put more resistence on the motor bogging it down a bit. If that motor can't spin the prop fast enough for the boat to plane then you won't be faster. When you match your motor with the right size and pitch of your prop you will maximize your speed.

On the evidence level I have cut off the tips of old Alas and they are faster. So have others, and some have done so with Twarons and Quatros with the same results. Just a couple of inches. Perhaps they were designed for a slower cadence at the length which they were produced. Or perhaps they had worn out so much that they stopped getting the proper shape for the water to flow correctly. Or perhaps my motor is not big enough for them. Or perhaps the range of my kick is too shallow. Or maybe it's a combination of any of the above. Or something else. But the same foot pocket with a smaller blade was faster.

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Just in case you weren't sure, it's official -- CMAS sucks.
Oh yeah, and now they're broke.

Duck: That's a good effort, you've managed to sum up most of the key information about blade design in bifins. Basically, it comes down to these points:

Longer blades suit a slower cadence and sacrifice speed for efficiency
Stiffer blades need a stronger kick and increase speed
Wider blades act similarly to stiffer blades
A well tapered blade will provide a better kick; the optimum bend characteristic is parabolic
More reactive materials provide increased speed and efficiency (carbon fibre = fibreglass > thermoplastic > rubber)

Now for the slightly complex interactions:
Stiff blades suit shorter fins, to a point. When the blades get too stiff and too long, the vertical thrust component becomes too great and severe efficiency losses are observed.
Wide blades need side rails more than thin ones to prevent side-slipping. They also have more "dead" area and have to be shorter than thin blades.
Longer blades need better tapers than short blades.
Better materials allow for easier control over bending.

Just some quick things of note

ps. For my money, somewhere between these blades (ignore the footpocket) are near optimal for me in medium stiffness, but with small side rails added.

pps. Obviously, personal preference plays a big part too, as noted above by Duck. I'm not big enough to kick hard fins, so there's no point for me. The bigger guys will go faster in them though.

Freedivenz, clearly you know your stuff well. Are you a Leaders dealer, or this knowledge came up through years of experience?

I can add to your post few of my points. For a uwh fin there are several important factors, that need to come together in the right ammounts to make best fin for uwh. And even the uwh hockey fin is not one, but two diferent types of fins. So the two most important factors are:
1. Manuverabillity
2. End speed
These two are broken down into several more, and added with other factors
3. 0 acceleration
4. Turning speed
5. Player safety
6. Resistance to tear and mechanical pressures
7. Foot friendliness
8....your ideas?

Now, you cant have all the factors on 100%, as one is contra-relating to another factor. Compromise needs to be found between all factors in the right ammount. Thats where the job gets hard. Basically, there are 2 different fins for hockey, one is more towards end speed, another more towards manuverabillity (fronts-backs), but the difference is/should be small. Here enters our debate about usabillity of monofin in uwh... as an option of one player dedicated do speed, might be able to check-mate the opponents that needs to wear manuever fins in order to keep-up the game.

The momentarry situation in uwh is as follows. On one side there are our old and beloved alas, with excellant manuverabillity, medium speed, tough, resistant, safe, with good acceleration and nice on the foot. On the other side there are fiber fins with higher speeds, ****ty manuverabillity, bad stabilisation, potentially unsafe and can be (or are) damaged quickly.

Probably the best fin is the one that negotiate the balance between these two sides.

My approach is "russian"one, that is to take something proven to work - e.g. alas, and build on that with strategy of "trial&error". But first I need to build on production and tooling. And even If I make the first test fins on time, I'll not be starting/selling before october, since my diving season starts in a month, and I'll use whatever spare time I have left, to build on tooling and production. In autum I hope I'll come up with something like alas on steroids.
The one thing I'm sure of is... I wont quit! Uwh is kindda like my own baby.

No, I'm not involved with leaderfins, but a friend is the local dealer and I own a couple of their fins, so I know them quite well. I've mostly built up knowledge of fins over time and through owning lots of types of fins.

Your points above are very good ones, I was only taking top speed into account and only looking at blades. Obviously this is only a small part of the story. I do disagree with you about fibre fins having bad stabilisation and manuverability, but that depends on what you've tried. Of course it depends on how you make the fin as to what properties they have. I firmly believe that fibre or kevlar blades are the way to go. The key is to take those blades and get the rest of the story right too.

In saying that, alas are quite a good starting point. They may be a little wide for my liking, but they balance all the variables quite well. I think it would be worth experimenting with side rails, 1cm above and below the fin would be a good starting point. For some wide examples, see C4 Falcons and Mustangs, while the Fisher Power Fins have a much smaller rail.

The footpockets on those mustangs look just the ticket, what a fantastic idea.

Freedivenz, have you swum with them, what are they like?

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Faster than a speeding puck...

I had something similar in my mind, as Mustang footpocket, but dropped the idea becouse it seemed to me it couldnt work properly... problems with movement with fins - as in turns, but Mustangs footpocket seems worthy at least for normal swimming, if not for hockey. Nice design too... excellant attention to details, check the last pic, and you'll see how that footpocket was made to try to get the best grip. How much those fins cost?

About kevlar-carbon-fibre, I would agree with you, If I would have a working idea on how to make the story right. For now, I think the best approach is to use fibre only as an armature for upgrading speed performance of an all flexible fin... If it was for any other sport but uwh&uwr, I would definetly go for fibres.