Sporasub Shoe Fins (i.e. Sporasub Revolution)

[trux]

Trux, I understand your concerns about non-streamline shape of those Revolution fins boots but my question is - C4's have a huge rectangular blade up to the nose of the foot pocket isn't it more waste then just boots in Revolution?

Hard to tell without a hydrodynamic test, but I'd tell the design of the C4 Mustangs is much more streamlined. The square leading edge alone is not necessarily a problem. In fact it can improve the hydrodynamics - just look at the leading edges of high-end monofins.

 

[sancarlos]

Square is almost always bad since square usually means turbulence while soft shapes and materials usualy means more laminar flux (just remnants of physics)
My point is more about width of the particular fin (C4 vs Revolution) in the area close to the nose of the booty.
Fins mostly works in the end and area close to the nose of the boody as you mentioned is mostly just a displacement of water so it rather irrelevant what particular shape it is (tennis shooes, big square etc.) - if it close to the foot it is bad. Theoretically the narrower the foot\foot pocket (kind of like the narrow place close to the tail of dolfin) the better the hydro performance whould be.
I actually like your suggestion to cover booty with some rubber like sock.

 

[trux]

Square is almost always bad since square usually means turbulence while soft shapes and materials usualy means more laminar flux (just remnants of physics)
My

You are not necessarily right. The shape can also help reducing turbulences. You won't be able to tell the exact effect without a hydrodynamic test or simulation. Foot-pockets with diagonal wings can often cause more turbulences than the straight leading edge. The diagonal edge is much longer hence if not perfectly designed, it can create more turbulences than the hydrofoil-like straight edge. If straight edge cause significantly worse turbulences, hydrofoils would not work so well. Look at the DOL-fin - the leading edge is perfectly straight (and quite long in plus), still the hydrodynamics is quite perfect, and the glide seems to be much better than at classical monofins. Well, that's also because of the high width/length ratio which significantly reduces the induced drag (similarly as wide wings at airplanes), but still the turbulence caused by the straight edge is no issue there.

 

[sancarlos]

Agreed on your analysis of relationship between rate of width of the leading edge of the fin to the thicknes of the fin itself - inverse drop (thick part first) is classic low grag shape. As far as what angle of the leading edge suppose to have - there is a veriety of angles in the nature - very acute in some fish and sea lions, about 80 degrees in dolfins\whales. One substantial difference of humans from sea creatures - the pivoting point in humans is often in knees or even hips, while in the nature it is usually in the narrowest point of the blade or close to it. Which actualy make lateral booty speed rather high and hence play to your argument that hydrodynamic shape of the booty is important. Anybody you know building any simulator of the diver fin action? Would be indespansible for testing\comparing fins. Shouldn't be that big of a deal with current technology.

 

[Jon]

Analysis aside, I've actually used the fins mentioned and the Sporasub Radicals suck pretty bad. :head

I don't get sponsored by anyone so I can say what I want. I had high hopes for them because I really like the pocket design and blade angle of my Mustangs, but the Radicals just don't have it.

A standard freediving fin, like my old C4-30's, might be smoother in the water than my Mustangs, but the Radicals are worse in a whole other way. The blade angle is too great, the blades are too soft, and the water flows off the sides too easy- since there are no rails.

We had a pair at Palooza last year and lots of people got to try them. The people I talked to all seemed to come away with the same impression- nice idea, but it doesn't work. I still like the idea of the cycling shoe foot pocket, but I think they need to go back and look at the blade. I had shot some video footage that I wanted to post, but can't seem to find it anymore. It showed a variety of divers working way too hard to get anywhere with the Radicals on their feet.

They're not the worst fin I ever used (that honor I save for the Lunocet) but they were pretty bad.

Just my $0.02,

Jon

 

[Mark Lamont]

Hey Jon,
While doing research for the Sea Wing fin, I found after looking at underwater swim videos, that the 26 degree angle was in fact just right. That placed the fin in alignment to the angle of attack by the diver (in many cases). The problem is that it makes walking on the deck of a boat or shore difficult and subject to breaking the fins. That is not commercially beneficial to any company. There is a solution to that problem. (No, I won't discuss that futher unless someone is willing to pay for my services).
I do think that drag and turbulance play a significant role in the efficency of the fins. And that being said will not pick on Sporasub more than to say the idea of the shoe is great but the execution is poor in my opinion. I hate those little flappers (for shoe adjustment) on the top since they apear to be turbulence prone. Sporasub has always had a fin with a toe that juts out (my H. Desault's were my favorite and died from overuse) but they were also (the foot pockets) more steamlined than these new ones. The toe of the shoe jutting out is not refined.
I agree with the leading edge of the fin allowing the free flow of fluid onto the blade. One would never expect to look out the window of an airplane and see a rubber rail in front of the wing so why do we do that with our fins? I also like also the blades on the fin tips for alignment of the blade to the flow of water.
If the blades are in fact too soft, that seems an easy fix for Sporasub to overcome by changing materials. I believe that the key to the long fins is memory. That is the ability of the (in this case) molded material to return to it's original position. Carbon fiber is becoming more prevalent in fins for this reason. Softer fins are a marketing challenge more than a engineering challenge in my opinion. I have a response in DB (deep spearo fins something.....) in which we found that by changing ones swimming style to a higher frequency and a more rythmic kick style efficency and therefore speed increases. Scubapro found this by accident and was an impressive lesson for us on the Test Dive Team at the time.
The swimming machine thing in my opinion is trash or garbage which ever is more respectful according to the rules of engagement here.
I went to Smith Aerospace and looked at the DOL fins online and think they are more on track than not. One of their models is very close but would be a disaster in California kelp diving.
It would seem that we as a community are in for some really nice equipment in the near future. The marriage of some of these ideas is going to make the community laugh over todays fins. I hope to see some of my drawing board design dreams come true.

 

[Ol Dirty Diver]

I have a response in DB (deep spearo fins something.....) in which we found that by changing ones swimming style to a higher frequency and a more rythmic kick style efficency and therefore speed increases. Scubapro found this by accident and was an impressive lesson for us on the Test Dive Team at the time.

Mark,

Can you elaborate on this? I am very interested to hear more.

Early on my intuition told me that this, too, was the way to kick. I was into cycling and running and I knew that higher cadence with less stretching against one's flexibility and energy expenditure per stroke was the ticket (as exemplified by the Africans' >90 RPM and Lance Armstrong, respectively). That plus all the frontal drag from a wide amplitude kick.

Then I met Martin Stepanek. I am now an instructor for his school and thus I am sorta' forced to teach his philosophies, which, in regard to kicking, is totally opposite. He describes that we only produce propulsion as long as our fins are bent (and the response of the material comprising the blade is engaged), therefore we should strive for keeping the blades bent as long as possible through a wide amplitude kick. As long as the blades are bent we are pushing water back. But I question that the mechanics of bi-fins is really that simple? Perhaps lift is somehow created and contributes to the propulsion instead of the idea of simply pushing water back?

Of course it is not sufficient for me to simply tell students this...I have to demonstrate it at all times as a part of my style. I have to admit that it works...It takes me only four kick cycles to go from 0 - 10m (with neutral buoyancy at 10m). But perhaps at the expense of greater oxygen savings through more but easier kicks?

I acquired the C4 80s a long time ago and had high hopes for them knowing all the world records they served, but neither my partner nor I could stick with them...Too noodley. But perhaps their extra blade length is intended for a low amplitude/high frequency kick? Maybe such that the blade assumes an S-bend instead of a big arc? What are the mechanics of this type of fin stroke?

Eager to hear your thoughts.
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[trux]

...The problem is that it makes walking on the deck of a boat or shore difficult and subject to breaking the fins. That is not commercially beneficial to any company.

I have already seen many hundreds (when not thousands) of freedivers, but I never saw one walking in their long fins on the deck of a boat, or the floor of a swimming pool. That's perhaps more usual among newbie scuba divers and snorkelers, but I do not think any freedivers would consider it a problem if they could not walk in their bifins.

That told, I agree that the concept of bicycle shoes directly offers the possibility of a quick lock mechanism with removable blades (just like at the monofin shown in this thread: http://forums.deeperblue.com/monofins/88435-shimano-monofin.html), and that I was a bit disappointed seeing the Sporasub did not take advantage of this possibility. It would be very easy, and very profitable in this case, especially if it reused the same lock mechanism as at bicycles, and you could use the shoes not only for the fins, but also for walking and riding a bicycle.

I do think that drag and turbulence play a significant role in the efficency of the fins.

As an owner and user of the Revolutions, I can indeed confirm that the drag is easily noticeable in comparison to other fins.

I agree with the leading edge of the fin allowing the free flow of fluid onto the blade. One would never expect to look out the window of an airplane and see a rubber rail in front of the wing so why do we do that with our fins?

If you look closer at an airplane wing, you'll see that the leading edge is much thicker that the trailing edge. You can see it easily also for example at a dolphin of a whale fin. The hydrofoil profile contributes to the propulsion. However usually in this way it make sense only at monofins, where there indeed is some leading edge. At bi-fins, there is practically none, and most of the water flows onto the fin along the feet. At bi-fins the side-rails serve to two other purposes:

1. Keeping the water on the blade, preventing so that it spills sideways too much. See below the water flow over a fin like the C4 compared to the Revolution. I think it will be more apparent that a great part of the energy gets wasted in the second case.
   
   
   
2. And the second important purpose is reinforcing the root of the fin, hence distributing the propulsive force to the whole blade. This is the principal problem at the Revolutions - they are very narrow at the shoe, and are not reinforced there, hence all the flexing happens directly at the shoe tip, and the rest of the blade is already off the ideal attack angle.

I also like also the blades on the fin tips for alignment of the blade to the flow of water.

Considering their size and position, I find them almost entirely useless. The effect of stabilisation is minimal, and they do no prevent water escaping to the sides of the blade.

If the blades are in fact too soft, that seems an easy fix for Sporasub to overcome by changing materials. I believe that the key to the long fins is memory. That is the ability of the (in this case) molded material to return to it's original position. Carbon fiber is becoming more prevalent in fins for this reason. Softer fins are a marketing challenge more than a engineering challenge in my opinion. I have a response in DB (deep spearo fins something.....) in which we found that by changing ones swimming style to a higher frequency and a more rythmic kick style efficency and therefore speed increases.

I agree very much with the opinion that soft fins may be more efficient with proper technique, and that the feel of force at stiff fins is actually just fooling us, because the vast majority of the resistance force is not transformed into propulsive force, but just moving water vertically. Many freedivers mistakenly think that the bigger resistance feedback the fin has, the better/faster/more efficient it is.

However, at the Revolutions it is a completely different case. The blade itself is not too soft. It has simply just wrong geometry - as already explained above, it is too narrow at the shoe tip, and is not reinforced by any side-rails, hence practically all the flexing happens at a single point - directly at the shoe, and the rest of the blade is inefficient, and permanently either overpowered or in a wrong angle of attack, regardless of the amplitude, frequence, or force you use.

 

[spaghetti]

I think you guys (Trux et al.) are just too much demanding from fins. The Revolution are spearfishing footwear for shallow-intermediate hunting sessions, where you barely need any real finstroke: Sporasub's are about comfy shoes, no rails, easy on side movements and sleek.
You will not break any freediving or finswimming record with them (I bet), but I've been told you can spear some nice fish on a shallow reef, and end up with no pain at legs and feet.
I think that's what it's about: a smart concept of spearfishing footwear. Performance fins are all another subject IMHO.

 

[Mark Lamont]

I have already seen many hundreds (when not thousands) of freedivers, but I never saw one walking in their long fins on the deck of a boat, or the floor of a swimming pool. That's perhaps more usual among newbie scuba divers and snorkelers, but I do not think any freedivers would consider it a problem if they could not walk in their bifins.

Hey Trux.........
No, all of the free divers like you would not walk in their fins and to set the record straight...nor would I. Doing the math of the free diver consumption of fins and if I agree with your thousands... let's say 2000 in the world and are they going to only buy one fin or many types of long fins? Let's assume the cost of a plastic mold for the blades is $150,000 and the molding process on a huge press if someone is even willing to mold 2000 short run items rather than hundreds of thousands plastic lids for storage boxes and on and on..........in short it's economics friend. There is no market for free diving fins. I would guess that the companies making freediving style fins do it for name recognition.

That told, I agree that the concept of bicycle shoes directly offers the possibility of a quick lock mechanism with removable blades (just like at the monofin shown in this thread: http://forums.deeperblue.com/monofins/88435-shimano-monofin.html), and that I was a bit disappointed seeing the Sporasub did not take advantage of this possibility. It would be very easy, and very profitable in this case, especially if it reused the same lock mechanism as at bicycles, and you could use the shoes not only for the fins, but also for walking and riding a bicycle.

That is a great concept.....Why isn't that done by all of the manufacturers of scubafins? (whom sell hundreds of thousands and cross sports product lines) Throw out the items needed and combine them to a generic sports shoe. I think the true answer to that is that the sale is made at the dive shop and saving money there affects the bottom line of both the shop and the manufacturer. Also most people want the top value for their recreation dollar and specialization is okay. With all due respect and I mean that. I have seen your responses and threads and you are very sharp.



As an owner and user of the Revolutions, I can indeed confirm that the drag is easily noticeable in comparison to other fins.







If you look closer at an airplane wing, you'll see that the leading edge is much thicker that the trailing edge. You can see it easily also for example at a dolphin of a whale fin. The hydrofoil profile contributes to the propulsion. However usually in this way it make sense only at monofins, where there indeed is some leading edge. At bi-fins, there is practically none, and most of the water flows onto the fin along the feet. At bi-fins the side-rails serve to two other purposes:

1. Keeping the water on the blade, preventing so that it spills sideways too much. See below the water flow over a fin like the C4 compared to the Revolution. I think it will be more apparent that a great part of the energy gets wasted in the second case.
   
   View attachment 29836
   
2. And the second important purpose is reinforcing the root of the fin, hence distributing the propulsive force to the whole blade. This is the principal problem at the Revolutions - they are very narrow at the shoe, and are not reinforced there, hence all the flexing happens directly at the shoe tip, and the rest of the blade is already off the ideal attack angle. The ideal attack angle is probably not a flexible foil. I also think but cannot back it up that different types of foils are at play in the ocean. for example, pelagic fish have a more traditional foil rounded in the leading edge and thin almost knife like trailing edge. Groupers and bass have a foil more common to a monofin. The snake like foil of a moray eel or squid are probably more aligned to a long fin. All are forms of propulsion. Can we as humans deliver the muscle to push a true foil? I think Smith Aerospace is proving this if their advertising is true.

Considering their size and position, I find them almost entirely useless. The effect of stabilisation is minimal, and they do no prevent water escaping to the sides of the blade.
Then if that is so, how would you make them yourself? would you put the rails on the sides of the fins only??? Are not all fin fish directing their muscle power from a single point? Just for laughs, you might take a look at my patent. US 4,737,127. Keep in mind that the time frame for this patent was 86 and it was stage one.

I agree very much with the opinion that soft fins may be more efficient with proper technique, and that the feel of force at stiff fins is actually just fooling us, because the vast majority of the resistance force is not transformed into propulsive force, but just moving water vertically. Many freedivers mistakenly think that the bigger resistance feedback the fin has, the better/faster/more efficient it is.
We are in agreement.

However, at the Revolutions it is a completely different case. The blade itself is not too soft. It has simply just wrong geometry - as already explained above, it is too narrow at the show tip, and is not reinforced by any side-rails, hence practically all the flexing happens at a single point - directly at the shoe, and the rest of the blade is inefficient, and permanently either overpowered or in a wrong angle of attack, regardless of the amplitude, frequence, or force you use.

I too in my testing built some very flexible soft fins. It was a good experiance to see both ends of the spectrum. As I said before I have had and used for years H. Dessault Sporasubs with a polypropylene blade and found them to be great fins for my type diving. They were more flexible blades with a shoe sole that supported well back toward the heel and (for me) much more comfortable than the Esclapez of that day which were way too stiff and didn't bend near the toe.

Rereading this reply, I see I'm doing the quote thing wrong. I will repeat my original ending thought. I can see that our diving community of freedivers will soon see a real revolution in diving fins both bi and mono. It doesn't take a genius to see it on the horizon. We will look back and have a good laugh at or present day fins. It will seem so obvious at that point.

 

[trux]

Yes, Spaghetti, I definitely agree that the Sporasub Revolutions are still excellent, and in many points superior to many other freediving fins. They are definitely worth of the money, and I never regretted to have bought them. If I did, I would have already sold them again.

I criticize them just because I see the enormous potential of the concept that went totally unused, although pretty evident. If they thought a bit more thouroughly during the development and testing, the fin could have blown away most other fins. However, I am sure we'll see other and better versions. If not from Sporasub, then from others.

 

[Ol Dirty Diver]

I think you guys (Trux et al.) are just too much demanding from fins. The Revolution are spearfishing footwear for shallow-intermediate hunting sessions, where you barely need any real finstroke: Sporasub's are about comfy shoes, no rails, easy on side movements and sleek.
You will not break any freediving or finswimming record with them (I bet), but I've been told you can spear some nice fish on a shallow reef, and end up with no pain at legs and feet.
I think that's what it's about: a smart concept of spearfishing footwear. Performance fins are all another subject IMHO.

Of course Sporasub wouldn't share a description like this in the catalog, but the guy running the show for OMER/Sporasub in the U.S. told me this very same thing. But it makes sense for everyone to have such high performance expectations considering the price tag.

 

[spaghetti]

But it makes sense for everyone to have such high performance expectations considering the price tag.

And what about comfort, Kurt? Does the comfort match the high expectations?

You see, I for one don't demand too much from my fins. I found it cool to fly up and down on a pair of Falcon 30 as well as with the Rekord 3, which made me feel "oh, these are some fins!".

But how many average spearfishers (or conservative divers) like myself do really need the "push" of Falcon 30, rather than an aquatic device that's comfy, smooth, and still capable do give me a few good kicks if I need them?

On the other end, you're right: price tag is pretty high for many of those who would like to giv'em a try.

(I'm not advocating the Revolution's: they're not made in Italy so I don't advocate them :t)

 

[Ol Dirty Diver]

And what about comfort, Kurt? Does the comfort match the high expectations?

Interesting point. For some reason I think most of us care more about the performance than the comfort when we consider new fins, even though the reverse is what is more important. In my review of the fins I definitely commended the comfort of the shoes. I mentioned how I could actually wear them comfortably without socks, and the issues of chafing (er, gouging out deep wounds around the heels) are eliminated.

But how many average spearfishers (or conservative divers) like myself do really need the "push" of Falcon 30, rather than an aquatic device that's comfy, smooth, and still capable do give me a few good kicks if I need them?

Well, the benefits of the carbon material certainly aren't limited to performance during ascent and descent. For all of us that kick around on the surface a lot, possibly swimming a few kilometers over a dive, the benefit is also huge...More help from the blades. This is what accounts for that good feeling of carbon fins (I remember thinking "buttery smooth" when I tried my Rekord 3s), and eventually less decrease in comfort compared to lesser fins when our ankles are tired from 6+ hours of diving (and we start to consider "bicycle" kicking :head). Who doesn't deserve this? When I used to work in a bike shop and was trying to sell high-end carbon bikes to new customers, I realized that many enthusiasts don't feel they "deserve" the higher-end bikes (invariably made of carbon fiber). I would tell them all the other benefits besides performance, such as much increased comfort, and would ask "Who doesn't deserve that?" If you've got the money, why not use what is most comfortable, with the side benefit of also gathering the best performance advantage possible.

 

[Mark Lamont]

Good Salesman Kurk,
That is the true sale.

 

[Mark Lamont]

Kurt,
As you can see, I'm not that good.

 

[spaghetti]

Kurt,
As you can see, I'm not that good.

 

[cdavis]

Mark, second dirty ole divers question about high frequency rhythmic kick and efficiency.

Last summer, while recovering from a knee injury, a buddy lent me a pair of spora plastic blades, black, very short and relatively soft, marked "brevete 5.G.D.G. Much less torque than my Specialfins. I quickly found that a high frequency, minimal knee bend kick was both very fast and seemed pretty efficient.

Is this the type of thing you are talking about?

 

[DANger-is]

I know this post is quite old but I was hoping that after using these fins for a while I could get an updated review.

I am new to freediving and I am looking to buy my first pair of freediving fins. I can pick up a pair of these fins for $200. So, compared to other fins in the same price range are they good?

 

[trux]

Although they could be much better, they are not too bad. After reinforcing the root of the blade, and adding side rails, they may even become very decent fins. But at this price and considering you are a beginner, I think I would rather suggest classical fins with exchangaeble blades, that you can easily replace or upgrade to another material or stiffness as you evolute.