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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.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?
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.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
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.
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....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.
As an owner and user of the Revolutions, I can indeed confirm that the drag is easily noticeable in comparison to other fins.I do think that drag and turbulence play a significant role in the efficency of the 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: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?
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.I also like also the blades on the fin tips for alignment of the blade to the flow of water.
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.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 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: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.
- 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
- 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.
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.
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.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.
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?
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?
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