Question Truefins
- Thread starter scubadada
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L13
Contributor
Took my Truefins to a popular local dive site this weekend, but I forgot the green spines. They were very nice. Almost the perfect buoyancy for my configuration, a happy medium between JetFins and Seawings. Still getting used to the changing stiffness during the stroke, but I think I will like them when I do. Especially with the green spines, I think the will have the right attack angles for my fining style.
Got lots of interested questions from bystanders.
Got lots of interested questions from bystanders.
T.K.
Registered
I’m willing to test them out. I am in the size range and will take video.
Dm your shipping address and they will be shipped out within 3 days.
Thanks for participating.
This concludes the shipping of the six pair of fins for this test. As I have indicated, this test will be repeated in the future.
Unrelated to this test, I thought I'd update those interested in the endurance testing we conduct. Truefin passed one million flutter kicks at 40 kicks per minute and 27 inches of swept tip length. We are now increasing that to 60 kicks per minute while we continue to adjust material and refine injection molding parameters. The spines and the Monprene fin have a lifetime guarantee. This endurance test is turning out to be an endurance test of the testing machine, because we have broken the mechanical leg twice due to metal fatigue, and we have to keep refining the leg design while keeping the metal leg as light as possible.
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<Still getting used to the changing stiffness during the stroke>
Interesting, I've never heard it phrased quite like that, but you are absolutely correct,, there is a changing stiffness of the fin rails with Truefin-
A comment I will make,,, when you are using spineless fins having elastomeric rails, the energy you put in to them to bend the rails during the initiation of the flutter kick stroke is never fully returned during the elastic rebound of the rails at the end of the kick stroke due to the self dampening nature of the solid rail elastomer. For example, I believe most resilience tests (which in a sense measures internal friction) are based on how far a pendulum rebounds after impact with an elastomer, or how far a weighted ball bounces up from a specified height from an elastomer. There is never 100% rebound with any elastomer, but some are of course better than others. I don't think Monprene has 'rebound' properties that are particularly high, but Truefin does not primarily rely of the 'rebound' of the rails, and instead relies on articulated spines. This is part of the reason Truefin is more efficient,,, most of the energy you put into the fin only occurs after the angle of attack has formed, and you don't waste energy forming the angle of attack that you will never get 100% back.
By the way, I've noticed the term 'snap' is also used in the fin industry, but I will say with conventional scuba fins,, again,, energy from the 'snap back' is never fully returned. Freediving fins operate differently in principle to scuba fins, with the familiar 'S' shape pushing water, and snap appears to be important,,, with carbon fiber currently being the best commercial material for freediving fins. Truefin is not trying to compete with long freediving fins, so if that is what you primarily use, Truefin is not suggested.
Additional info from truefintechnical-
.... long fins such as freediving fins are a different category and may benefit from both elasticity and 'snap'. Long freediving fins have a large surface area which displaces more water while typically forming a long 'S' shape during both up and down kick strokes thereby potentially offering more thrust, and the elastic 'snap' may be more noticeable and beneficial. The elastic 'snap' or relaxation modulus (Re) of the blade material is highest with carbon fiber blades. Fiberglass, plastic, and rubber have decreasing moduli and consequently less 'snap'. 'Snap' is a property that defines the response rate or elastic rebound rate, and is independent of blade stiffness. Typically, the relaxation modulus (Re) of a material is measured by holding the material at a given strain, and then measure the rate at which the internal stress of the material decreases with time as it relaxes.
.... long fins such as freediving fins are a different category and may benefit from both elasticity and 'snap'. Long freediving fins have a large surface area which displaces more water while typically forming a long 'S' shape during both up and down kick strokes thereby potentially offering more thrust, and the elastic 'snap' may be more noticeable and beneficial. The elastic 'snap' or relaxation modulus (Re) of the blade material is highest with carbon fiber blades. Fiberglass, plastic, and rubber have decreasing moduli and consequently less 'snap'. 'Snap' is a property that defines the response rate or elastic rebound rate, and is independent of blade stiffness. Typically, the relaxation modulus (Re) of a material is measured by holding the material at a given strain, and then measure the rate at which the internal stress of the material decreases with time as it relaxes.
I have one piece of product feedback and maybe you guys are already working on a solution based on a blurb in the documentation. The spines are difficult to remove, more specifically, the release is difficult to press just right. I kind of had it, but didn't have a way to pull it out easily. I see on the end is a small slot, maybe add to your removal tool, the ability to hook into that slot and pull?
With that said, the first two were a pain. I got the next two out more easily. Some way to hook into that slot would have made it even easier.
With that said, the first two were a pain. I got the next two out more easily. Some way to hook into that slot would have made it even easier.
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