Tropol monofin - angle survey

[trux]

I am in contact with Lubos Polak, one of the guys at Tropol, the Czech monofin manufacturer. We discussed their fins in this thread. As written there, they are quite interested in fulfilling freedivers wishes and developing a monofin specifically for freedivers, but they have personally only experience with monofin swimmers, so have some doubts and worries.

The most important problem now is the angle of the blade to the feet. From previous discussions, they decided to create a fin with a relatively big angle, which is otherwise not really usual at monofins - 30 degrees. However, lately a trainer from a finswim club contacted them, and warned them that they already tested fins with such a big angle, and that they were unusable. I countered with the argument that the situation is very different at finswimmers or freedivers with regular kick, and at freedivers, with kick'n'glide technique, who spend most of the time in inert position gliding.

However, because of that warning, they got rather scared that they may be working on a model that finally nobody will be interested in. The development is rather expensive, because unlike at many other manufacturers, they do not make the footpockets manually, but cast them from a mold. And the creation of such mold (resp. a series of several sizes) costs a lot of time and money, so I think they are now not sure whether the investment will really pay back.

Well, to help them with the doubts, I promised them to ask here on DB and make a small survey, whether there is sufficiently big sample of freedivers interested at all in such monofin.

Otherwise, the new footpockets they are working on sound promising - they are not only allowing for big angles, but are also non-compressible, hence suitable also for depth disciplines.

PS: myself, I voted "other" because I am not a monofin user and hence my opinion is worthless - I just wanted to cast a vote so that I see the results without clicking the button

 

[Kars]

Thanks Trux for your effort, or actually the manufacturers should say thanks to you!

About the footpocket angle.
I think the coach is right for their fast swimming type of use.

Freedivers on the other hand need to be able to GLIDE.

Glide between strokes in Dynamic,
Glide on the (long) way down!

Not to mention that most freediving ace's use the angle of 30 degrees, even though their ankles and feet should flexible enough with all their training.

Personally I've learned monofinning with the WaterWay Classic, but I'm since a year ago a very happy user of a 30 degree fin.
Recently I heart a story of a freediving women who used to stick with bifins because monofins did not work for her, too stressfull. Now she got a monofin, because she won a discount certificate, got a fin with a 25 - 30 degree angle, and she's loves it, now she can relax while swimming.

And off cause beginners LOVE that angle too, so an affordable 30 degree fin should become popular. And suit matching colours would make them extra attractive!

I still recommend the manufacturer to have a personal test, swim a dynamic with a 0 - 16 - and 30 fin, with goal of relaxed swimming. Hearing from someone is inferior to experiencing it yourself.

Be happy of this companies pro active approach,
Please Keep voting!

Kars

 

[Mullins]

This local expert prefers a 30 degree angle:

Mermaid dream comes true thanks to Weta - New Zealand news on Stuff.co.nz

Unfortunately it isn't used for propulsion, just to increase buoyancy and keep her level in the water. But this only makes the angle more important, as it has to be streamlined...

 

[DivingDane]

i have a fin with 22-23 degree angle and it is much better than other fins i have used with far less angle, i feel the power stroke is more continious and the glide phase is MUCH better, havent used a 30 and nt sure it is really needed however seeing as i have gone from no angle to about 10-12 and now to 22+ i would think that 30 would be quite easy to use and good for gliding.

DD

 

[trux]

This local expert prefers a 30 degree angle:
Mermaid dream comes true thanks to Weta - New Zealand news on Stuff.co.nz

Well, if I understood it well, the woman has no feet, hence no angle is needed, but I understand what you meant - that the tail (blade) is in direct prolongation to the legs-body axis, hence with no angle. Sure, from purely hydrodynamic point of view, there is no reason for adding an angle.

The question and the doubts about the angle come only at classical monofins. I already gave the arguments mentioned by others, to Lubos, and explained him that unlike continuous stroke, the glide at some freedivers requires that big angle to assure the best hydrodynamic and in the same time relaxed position (without the need to force the ankles into the straight position by strong muscle contractions).

I just wanted to hear more people having that opinion. As I wrote I am a bi-finner, intermediate freediver, and do not really plan switching to monofin, so my opinion is only theoretical and rather irrelevant. It would be possible that only one or two freedivers have the opinion that big angle is needed, but it would not be necessarily sufficient to trigger enough interest among others and assure sales that would cover the development costs. Fortunately, I see there are more people interested, and certainly the fact that Dave supports the concept is very important.

Still, I remember that Dave himself wrote in another thread that with the high angle monofin he lost some efficiency due to the lost "precharging" (with smaller angle the fin remains in a position that allows for a more efficient kick after the glide phase), hence there is some trade off between the better hydrodynamic position in the glide, and the need to kick stronger after the long glide. Or did I misunderstand that comment?

 

[trux]

Thanks Trux for your effort, or actually the manufacturers should say thanks to you!

Yes, he indeed is very thankful, but frankly told, I did not start it because I expected any profit from it, or because I have any financial/material interest in it. I am just enthusiast for everything what new fin development concerns, and some patriotism probably played a role too. On the other hand, although I do not expect it (and do not look for a monofin), I'd likely not refuse a nice discount or a sample for testing in our club, if a good fin comes out of it

 

[jome]

I'm convinced that "big" angle is good for freediving, but IMO 30 sounds a little extreme.

However, I have not tried it, so that is just an opinnion based other fins I've tried. I do know that I would love a little more than the current 15 or so.

While saying that I also think that for a lot of beginners it would be more important to not have big angle to learn proper fining, but that is not an opinion that sells fins (of course they all get the one that is easiest to swim with and to a degree there is nothing wrong with that).

 

[trux]

Yes, it sounds reasonable. I am just afraid that they won't be able to compete with prices of flat beginner fins, so am not sure whether a lot of beginners will be able or willing to buy a relatively high-end fin (that at least what they aim for). I wrote to Tropol that lower price would be definitely a big advantage and might help selling a lot of fins, but I do not know whether bigger volumes really help them reducing manufacturing costs. On the other hand, with the footpockets casted in a mold, they have better chance to lower cost with volumes than at manually modeled footpockets as at many other manufacturers.

 

[Kars]

Maybe contact Stig and Alexey about this angle issue? I they to have 30 degree's fins. Alexey Molchanov is the current Dynamic World record holder, he took it from our DB forum Dave Mullins.


Maybe something between 25 and 30 degrees will proof to be the sweet spot for most freedivers. But as a manufacturer I would consult the top 50 ranking Freedivers and ask in a few very short questions what they have, what they have tried and what they would like to have - when money was not an issue.
Possibly have a price competition, to win a fin, for filling out a questionnaire. A good way to gather those valuable and vital data.

Kars

 

[Fondueset]

It seems like the standard non-axial (aka 'Hyper') style fin angle is right around 22-23 degrees. I know this type of fin was a very large improvement over my Water Nemo - which had 11 degrees - making it much easier for me to swim with minimal knee bend.

My suggestion would be that they manufacture both - more standard 22-23 degree and, probably in lower quantities, the 30 'pro-freediver' fin for those who want/need it.

I'd like to try a 30 degree fin, but have not requested it on my newest.

 

[jome]

What is the price point they're aiming for?

Incidentally I might be looking for a new fin (who isn't ) and since I've yet to be completely happy with any fin this is very interesting.

 

[Mullins]

Out of interest, what range of ankle movement is considered 'flexible'? When finning the tops of my feet are almost exactly in line with my shins, or just slightly below. The perfect fin angle for me seems to be just over 30 degrees, maybe 31-32.

The problem with fins like this is that you need a flexible back. Because a 30 degree fin is neutral when sitting directly in line with your body, when you kick the down-stroke needs to go significantly below the plane of your body. Because your knees don't bend fowards, the amplitude of this down-stroke needs to come from your back and hips.

A fin with 0 angle needs no back/hip movement, because your knees are very bent when the fin is in a neutral position. So all you need to do is straighten them and voila, you have a down-stroke.

 

[trux]

What is the price point they're aiming for?

I do not really know, but see that they sell the current monofins for 8500,- CZK (incl. 19% VAT) - with the current exchange rate it gives ~300€ (~240€ without VAT). I have no idea if they can afford keeping similar price at the new monofin too.

 

[jome]

Well if they have a 30 degree prototype or something, I'll gladly buy one and give it a whirl (current fin is falling apart).

Right now, my biggest frustration with current fins is the durability and comfort (open water activities, dynamic I don't much care for), so if they can do something about that I might even be willing to sacrifice some performance.

 

[trux]

Lubos watches this thread, and in the relation to our discussion about the glide, and the first kick after it ("precharged" at low blade angles, vs. coming from a flat/streamlined position at high angles) he asks about the stiffness of the blade, and whether a stiffer than normal blade is needed.

Theoretically it makes sense, because at the kick'n'glide technique the fin works in short bursts when it is (or may be) periodically under similar stress as at the start - frequently having to accelerate from almost standstill to a relatively high speed for sufficient subsequent glide. Normally, for such acceleration, stiffer blades are more efficient, and bear less risk of being overpowered.

However, I believe Dave prefers soft blades anyway. I am not sure about others who use the kick'n'glide technique, so hope to get some feedback here. And Dave - how soft/stiff your fin is, or better told what you think would be optimal?

Well, I am sure that different levels of stiffness will be needed for individual freedivers anyway, but the question is whether there should be an offset for the entire scale - making them all slightly stiffer than regular fins, or vice-versa, or keeping the stiffness just exactly the same as at regular fins?

 

[Fondueset]

I know Will T. uses a very stiff Glide with a blade that is an inch or two shorter than normal.

I would say extra stiffness is not called for - because the blade needs to flex with minimal movement from a dead stop undulation-wise.

I certainly appreciate the amount of thought going into this thread - and the fact that the manufacturer is watching it.

I'll also volunteer to test a fin. I only use monofins and my focus is primarily on open water diving - I also do dynamics in a pool, however, several times a week. During the winter I do primarily dynamics in open water as well (to stay warm). Summer more varied recreational diving. Several times a week year 'round.

I can evaluate durability and performance - since I dive in extreme temps. I'd also be happy to do a product review for DB once they are ready.

 

[chrismar]

For me, at least, soft is better. If the blade is too stiff, a single kick will require too much knee bend to power. Besides, we're not exactly going fast...

 

[trux]

Yet another question from Lubos. Lubos browsed the forum a little bit, and saw that at freedivers, the requirements for the comfort, and tightness are quite different in comparison to swimmers. When he sold his first monofins to couple of Czech freedivers, he was surprised they asked him if neoprene socks would fit in.

Now he understood that most freedivers prefer and need more comfort for better relaxation, and in the same time, at open water freedivers, also sufficient insulation is often needed. Because he is working on the molds for the footpockets, he needs to know whether they all need to be slightly bigger to allow for more comfort and for neoprene socks, or whether there is a big percentage of freedivers who do not use socks, and/or prefer fins with tight footpockets just like finswimmers.

And if any of you have special wishes for the shape of the footpocket, do not hesitate to voice your opinion. For example requirements for the width vs. length, finger tightness, sole arc, etc. I also wonder if any of the current Russian footpockets have any opening at the tip to facilitate putting them on and off, just like most bi-fin footpockets have? And if they don't, is it for improved hydrodynamics, better fit, or just an omission because it is not considered useful?

 

[trux]

Well, I just see Fondueset's comment in the Triton thread, where he writes:

... as regards fit - My fin is made to accomodate 5 mil socks - but its not easy! These things are supposed to fit as tightly as possible or they lose efficiency - it took month's for my feet to adapt and you must always use lube and my socks are smoothskin neoprene on the outside. Nylon out 5 mils socks were a nightmare.

For example - Will Trubridge's custom Waterway is two sizes SMALLER than his normal size so that, as he puts it 'he can feel the water'.

So apparently there are apparently freedivers who prefer as tight footpockets as finswimmers do. Or is Will a rare exception?

 

[Fondueset]

Hi trux,

Because I dive in very cold water I have to have a compromise of tightness and efficiency. With my current fin from Triton I think Max did an outstanding job with the footpocket.

If I use a nylon out sock it is very difficult to get in without the sock bunching and curling my toes. I began turning my open cell socks inside out and lubing them and this works well. In 2c water I can wear the fin for 1-2 hours depending on how I am swimming. In the bahamas - with a 3 mil sock, I wore the fin for six hours with one short rest when I took it off to get more sunscreen.

I find that socks that are smoothskin on the top, with nylon on the bottom, also work well - though the ideal would be smoothskin everywhere. Also open cell socks with nylon on the outside work if turned inside out.

I think competitive freedivers may have different criteria regarding fit when compared with recreational divers. As I mentioned - Will Trubridge has a waterway glide that is two sizes below his normal foot size. Of course he is wearing it for relatively short periods of time doing a few very deep dives.

I think Tropol would do well just making standard size fins - with recommendations that people should go a size up or down depending on how they want to wear them. Perhaps size them for a 3 mil sock - then recommend half a size up or down depending on the diver's preference.

As mentioned - I would be happy to test some fins out for recreational diving in our conditions and pass them around among other freedivers to provide feedback on sizing and performance.

In terms of fit criteria - based on my experience - my fin is very tight compared to my waterway nemo or any of my bifins. I normally need about 15 minutes for my feet to adjust to the fin and, after I take it off, I need about 5 minutes for my feet to relax back into 'walking' configuration.

What seems key to me is avoiding compression of the toes, and sides of the foot while still having the fin fit snugly so that power is well transmitted. In other words - the fin must fit tightly in areas that are key for force transmission - without putting undue pressure on the feet in areas that are not relevant.

Hope that all helps!