Foot pockets without tendons

  • The discussion in this thread Pathos Fireblade and Salvimar 4One reviews... prompted me to put together fins with foot pockets that don't have tendons. This was my intial post.

    So I decided to bring this thing to life, introducing the Speardiver "freeblades" :) I cut the tendons off H Dessault foot pockets and reshaped them. I figured the blade will need more support from the bottom so I shaped a piece of starboard. It doesn't feel much different than a blade in Pathos foot pockets. It will feel different once the water channeling rails are on. I'll try it and post back. Xan, you're welcome to try them.


    BTW if there's a fiberglass blade that can handle that kind of stress it's this one. If it breaks at the toe there's no usable blade in existence that will bear it.





    I finally got around to trying them. I really like the action, nice and soft. The footpockets are comfortable and the fins are light. I'd use the metaphor of a roomy comfortable Cadillac (these fiberglass fins) versus a cramped sports car (carbons in Pathos foot pockets).


    hau also tried them and I made a vid so you can see the action of the fins. In the video I say he's moving faster, I'm making a comparison to the omer ice fins that he brought. I also made one of the fins with water channeling rails and the other without for comparison. I already knew this but it was nice to see again the water channeling rails doing their job. The fin without the rails would lose control and do a quick wobble right at the end of the stroke.


    Freediving fins - footpockets without tendons - YouTube

  • Dan that is one of the best vids ever to discuss fin stroke....thank you


    what size are those pockets? I would like o test them just to see what it is like..i assume they are small if they fit Hau's dainty feet :)


    very cool and informative

    i like to spear fish

  • Dan
    My brother did the same thing with soccer cleats and DiveR fiberglass blades.


    He was doing a practice SWB rescue at 100', and snapped the blade at the toe at 60' while dragging a limp body up with him.


    Until then, he loved them.

  • Thanks for that info. One thing DiveR blades have is they're strong, if they snapped other blades will too. Albeit that's about as much stress as you're ever going to put on blades, pulling another person up I mean. Another thing to keep in mind is your brothers method of securing the blades to the soccer cleats is not apparent. I'm using foot pockets with support from the bottom.


    My contention has always been that moderate stiffness tendons are necessary to support the blade and gradually dissipate the stress on the blade away from the toe area. Making these fins was my way of saying to those who advocate very soft foot pocket tendons "why not take it all the way then". I fully expect them to fail at some point, more so if they were carbon. But in the meanwhile they're nice.

  • Thanks for that info. One thing DiveR blades have is they're strong, if they snapped other blades will too. Albeit that's about as much stress as you're ever going to put on blades, pulling another person up I mean. Another thing to keep in mind is your brothers method of securing the blades to the soccer cleats is not apparent. I'm using foot pockets with support from the bottom.


    My contention has always been that moderate stiffness tendons are necessary to support the blade and gradually dissipate the stress on the blade away from the toe area. Making these fins was my way of saying to those who advocate very soft foot pocket tendons "why not take it all the way then". I fully expect them to fail at some point, more so if they were carbon. But in the meanwhile they're nice.


    So do you believe the softer tenons allow better flex of the entire blade?

  • hey chuck, do you have any pics of your brother's setup? I am curious as t how he attached them


    He drilled four holes into the flat part and used screws with washers to attach directly to a high end soccer cleat. And it didn't break at the distal screw holes like I thought it would.
    C

  • So do you believe the softer tenons allow better flex of the entire blade?

    I believe tendons should be of moderate stiffness. Enough to give the blade some support (which very soft tendons don't, just like the tendonless foot pockets), but not so stiff that they don't allow the blade to flex at all.


    Blades take an amazing amount of stress pushing us forward, we usually don't think about it and just expect them to work. And we want them to be light and reactive at the same time. It's too much to ask when using a foot pocket that doesn't offer good support.

  • I believe tendons should be of moderate stiffness. Enough to give the blade some support (which very soft tendons don't, just like the tendonless footpockets), but not so stiff that they don't allow the blade to flex at all.


    Blades take an amazing amount of stress pushing us forward, we usually don't think about it and just expect them to work. And we want them to be light and reactive at the same time. It's too much to ask when using a footpocket that doesn't offer good support.



    I believe the amount of support a footpocket needs to give a blade is really blade-specific. Having helped lay up carbon fins before, if I were to do a rail-less pocket, I would do exactly what you did... add extra layers closer to the pocket/shoe attachment, but of increasingly longer lengths. Likewise, if I were to use a pocket with soft tendons, I would use a blade that has more integrated support. A graduated taper (i.e. progressively layered) has more backbone towards the back and softer towards the tip. The front still flexes well, while the back provides a second layer of power.


    A parabolic bend like most blades is great for general kicking, but (as you said) relies the tendons to keep the back half stiffer. No way around physics, tendons do damper the responsiveness of the blade material. The question is how much is necessary for support/guidance and where the point of diminishing returns comes into play. :)

  • In theory yes but practically no. There's a practical limit to how many layers you can use and how you can arrange them, and still have a light reactive fin. A uniform blade with an as you say parabolic flex pattern hasn't even entered my considerations. I don't know if you've used DiveR blades, they're as strong as it gets as far as backbone, so much so that I find them too heavy and uncomfortable, and they still broke. Barring a manufacturing defect which is always possible, this really demonstrates the problem with lack of blade support. If this happens with fiberglass it should be clear that carbon doesn't stand a chance. If the blade is going to be so thick in the back that it doesn't break, the fin will be too stiff to use. Otherwise there will always be a point of transition in thickness where the stress will be focused, and the blade will break there.

  • the problem with saying dive Rs are too stiff is the fact that they come in different stiffness's and you only had the mediums . i dont see any reason you cant make a fin blade that can be layered out to not need tendons . blades are the simplest thing in the world to lay up and they are still all made with the simplest production minded way possible . anyone with a little composite know how and a little skill and the right parts can make a blade in their garage as good as the best on the market after a couple trys to get the method and stiffness profile down
    phil

  • In theory yes but practically no. There's a practical limit to how many layers you can use and how you can arrange them, and still have a light reactive fin. A uniform blade with an as you say parabolic flex pattern hasn't even entered my considerations. I don't know if you've used DiveR blades, they're as strong as it gets as far as backbone, so much so that I find them too heavy and uncomfortable, and they still broke. Barring a manufacturing defect which is always possible, this really demonstrates the problem with lack of blade support. If this happens with fiberglass it should be clear that carbon doesn't stand a chance. If the blade is going to be so thick in the back that it doesn't break, the fin will be too stiff to use. Otherwise there will always be a point of transition in thickness where the stress will be focused, and the blade will break there.


    Dan,


    My DiveR carbon fibers are super light and as indestructable(almost) as the fiberglass ones. I must add that my brother weighs 240lb and was a collegiate swimmer, and was pulling a limp Kirk Krack up with him when the blade snapped.


    And my Beuchat pockets are very light too. I haven't felt a lighter combo yet, including the Pursuit CF blades in on old set of OMER footpockets.


    I'll try to get a scale to weigh my set ups, but they are glued in, so I can only weigh them with the footpockets.


    What are the weight of the Speardiver CFs in your footpockets?


    C

  • The weights of the blades and foot pockts are listed in their respective threads, blade specs are also listed in the store Speardiver C90 Fin Blades - Speardiver. You can add them up to get a weight for the complete fin. However blade volume and feel, which is something you can only know by handling it, means more to me than a weight measurement.


    Phil, I owned only one pair DiveR blades, but I've seen a few come through my shop. I consider DiveR to be strong blades and only used Charlie's story to support my idea that foot pockets without tendons are not a valid option. But if you want to discuss them at depth; I don't think much of DiveR fiberglass blades with their overdone 30 degree toe angle, no water channeling rails to stabilize the blade, and overall cumbersome feel. My fiberglass blades are simply better in all those aspects, when I finally do make them available.


    I disagree with you about manufacturing, easier said than done. It takes a specific set up, materials, and manufacturing methods to produce good blades. Never mind with consistency. Vacuum bagging doesn't cut it.


    I've seen and tried many many blades because that's what I do. IMO if there's one blade that will last in foot pockets without tendons it'll be one like the old flat Waterway blades. As you may know they're not laid up to create a flex pattern. The flex is created by machining layers off one side of the blade that's one thickness throughout to begin with. Done properly this allows for much more precise tuning of flex than layering. But even so this will be a relatively heavy fiberglass blade. IMO with layering you will never produce a usable carbon blade that will withstand lack of tendon support. It's just a dream, that's why no one sells them and no one ever will. The company would go broke from replacing broken blades.

  • Forgot to add that IMO foot pocket tendon add to the water channeling effect which stabilizes the blade. I can't offer anything to support this other than my hunch, having tried these tendon-less foot pocket fins.

  • I Know this is an old thread but i thought i would show you my foot pockets. They are Picasso, way to stiff, and i am running Marez razor plastic fins. I used the foot pockets from the razors for my diveR fins.


    Instead of leaving them in the garage never to see the light of day i chopped the tendons right down, but not off.


    They hold the blades in nice and tight and i get a heap of movement out of the plastic blade. I am thinking about sticking nice chunky rails all the way down the side, at 3 bucks a foot its a cheap experiment. So far the fins are great. These are used for rock hopping in rough conditions and that it, its shallow hunting all below 20m.


    So far so good, like i said beats leaving them in the garage as parts never to be used AND i don’t need to buy another set of fins for a while.

  • Do think it would be possible to melt the rubber with poly glue to get the right size gap? We melt 4mm thick Poly to colar a hole drilling using this technique.....


    I'm not worried about butchering these fins, it's more of an experiment than anything else...... Sticking it to the blade willmbe difficult , could even pop rivet them on!!:@


    Did you notice a huge difference with the rails Dan? These do slip side to side a bit when I go hard but nothing major. I think the short tendons make a huge difference when compared to no tendons

  • I'm not familiar with that method so I can't comment on it. Would be interested to see you try it.


    The water channeling rails definitely stabilize the fin. But I don't know why you'd invest the effort in the plastic blades. Once you use carbon or a good fiberglass fins, it's impossible to go back to plastic fins, even to mess around in shallow water. So you end up not using them even as backup fins.


    BTW it would've been better to weaken the foot pocket tendons rather than chop them off completely. You would've gotten some stabilization effect from the foot pocket tendons.


  • Yeah right I didn't think of that, probably would have been better.


    In places like Albany in Western Australia we dive in 6m swells off the rocks, fiber and carbon fins get smashed in a few exits from the water. It's only calm there a handful of days a year. But it's worth it we hunt off the most southerly point of the state, it's pretty intense. I hate plastic fins but there's really no choice for this type of diving,it's just rough as guts.


    We mostly use diveR fins in our group, but we all have a pair of plastics for rock hopping, I will try and dig out some pics for you....


    Was thinking about getting a pair of C4 wahoo fins as a compromise when these ones die, I get the, for 200$ so it's not to bad...... Have you used the wahoo fins yet?

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