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Extreme Dolfinism

Discussion in 'Monofins' started by REVAN, Mar 17, 2010.

  1. REVAN

    REVAN The Right Stuff Supporter

    Local Time:
    4:23 AM
    Dealing with the water inside the fairing was the largest design risk I had moving forward with the DOL-Fin Orca’s development. My plan actually was to capture the water inside the fairing, “like a bucket”. The risk was that I really didn’t know how the mass of trapped water inside the fin would affect the feel of the monofin, and my biggest concern was that it would somehow mess up the ability to stroke the fin and produce thrust effectively.

    My hypothesis was that the non-streamlined fin was already dragging a huge mass of water along with it as a shed wake, and that adding the fairing would actually be reducing the mass of water being pulled along with it. Unfortunately for me, the only way I knew of to prove if my hypothesis was true was to build and test it in the water. When this ended up taking twice as long as I originally thought it was going to take, I was getting rather nervous about that first swim and the moment of truth. It had the potential to be a very expensive failure.

    Fortunately, my hypothesis turned out to be right. The DOL-Fin Orca with the water trapped inside it actually feels much lighter on the feet than did the prototype without the streamline fairings. It was a big improvement, and I knew it was going to work within about 10 seconds of strapping the fin on.

    This method of using wet ballast keeps the fin lightweight when it is dry which makes for easy traveling. The DOL-Fin Orca weighs in dry at about 5 pounds (2.25 Kg). This fin design also effectively has a trunk space in it. I am thinking of making one of the fairing shells in-water removable, and using that volume inside to store a fresh-water reserve, a signal float/buoy and a strobe light. If you ever found yourself lost at sea, you would have a decent chance of survival and rescue if you have this basic survival gear available. This could be a nice safety option for sea-hiking and recreational freediving.


    The feet fit inside the shroud using the same basic methods I had used on my previous DOL-Fin systems. I use textile binding straps to secure the feet to a rigid base-plate. The system is adjustable and, when secured, have no buckles or loose ends sticking out in the flow to cause drag. To add more structural stability to this fin’s interface to the swimmer, I have increased the height of the side rails of the base-plate which hold the assembly in alignment with the feet. I have also added an option to include adjustable side rails for inside edge heel support.

    The binding straps are not presently padded, and although you can wear it over bare feet, I expect that it would chafe. Padding can be added to these straps, but I have always felt that it makes more sense to have the padding on your feet instead of on the fin’s straps. At a minimum a low-cut cotton gym sock can be enough padding. I usually use a low cut 3 mm dive sock in warm water and for colder water switch to a high-cut 3 mm or 5 mm depending on water temperature.

    The system is different to what you are used to, but I think it has several advantages over the old methods. Once familiar with how to use it, I think most divers will come to appreciate the design.
     
    Last edited: Mar 26, 2010
  2. Fondueset

    Fondueset Carp Whisperer

    Local Time:
    6:23 AM
    Now that is one thing I would not have thought was okay - letting the shroud collect water. Shows what I know. It looks like with that fin you could even wear a surf boot or something - which would be darned handy for seahiking type activities.
     
    Last edited: Mar 26, 2010
  3. REVAN

    REVAN The Right Stuff Supporter

    Local Time:
    4:23 AM
    For most sea-hiking activities I like using the Pinnacle Stealth fin sock. It is half way in between a dive sock and a dive boot. I recycle older ones that rip-out on the opening, by cutting off the top and making it a low cut and use those for warmer waters. I like having the sole on it though. It really makes a big difference on sharp rocks and barnacles. Plus the sock itself is far more durable.

    I must be a big wussy, because I don’t know how you folks can stand going out sea-hiking without some protection on your feet. The cuts and blisters would take the fun out of it for me.
     

    Attached Files:

  4. Fondueset

    Fondueset Carp Whisperer

    Local Time:
    6:23 AM
    Well Ron, I'm glad you mentioned that.

    You see, here in the Great North (and I'm sure Pete, who is a genuine Canadian can echo my view) we think of comfort as something meant for girls. Fact is, most of the time we can't even feel our feet! - and who would want to anyway?! (insert creepy-nervous laughter)

    Seriously (?) though - another plus of your fin is the opportunity to buy cool footwear - I found these over at Leisurepro for $30. Can't wait till I need em!

    Cool Surf Shoes
     
  5. DivingDane

    DivingDane 1BREATH Freediving

    Local Time:
    10:23 PM
    Revan i understand your grasp of hydrodynamics is MUCH better than mine.

    however i am almost 100% sure that the Bucket efect is a negative for glide and hydrodynamics

    mares has addressed this exact problem with their new scuba fin the X stream.

    i can think of 2 solutions one of which would require a moification of the shroud, the other s aimple addition.

    1. like on a boat or plane shroud add scubber style ventilatrion hole angled towards the back, the higher flow on the outside would cause negative pressure and allowwater to flow through this area more freely preventing the breaking of the bucket effect.

    2. which i believ is much simpler is to add a smooth skin outer GATOR to the shrpoud which moulds aroung the ankles and attached to the shroud, this would prevent any water from being channeled into the shroud. it would not need to be water tight as once the fin is under water and the shroud is flooded then you would still have your hydroballast, but with the gator over the top the streamlining would be further improved.

    i think the second option would be the most cost effective and probably the most hydrodynamically effective as well. all that would be recuired would be some smooth skin neoprene (say from an old suit) with one large hole in one end to fit over the shroud and 2 smaller holes in the other end of the tube to fit each foot into, the shroud would then sit snuggly just above the ankle covvering the feet and entrence to the shroud preventing water flow. pretty sure it will work.

    DD
     
  6. DivingDane

    DivingDane 1BREATH Freediving

    Local Time:
    10:23 PM
    i think much of the attraction lof bare feet in a fin is the feel of it, i feel much more attached to my fin this way, when i move my feet even slightly the fin reacts, even having a 2mm sock i find i can feel the sock compressing before the fin moves, it is only miniscule but because of it i definetly find my diving experience much more enjoyable... in saying that i can understand from a cold water divers point of view why a 3mm or 5mm sock would be of huge importance. luckly for me ocean temperature never fall below 22 degrees celcius in my area (and thats only for a couple of weeks before it heads back up to around 30 degrees in summer)

    DD
     
  7. Fondueset

    Fondueset Carp Whisperer

    Local Time:
    6:23 AM
    you still have a mass issue - I submit this is a non-solution and we'd best leave Ron to his own device :) On the sock issue - we studied this in taijiquan. There is a saying that a fly alighting on the hand sets the whole body in motion. True also, with some acclimitization - if the hand is gloved.
     
    Last edited: Mar 26, 2010
  8. REVAN

    REVAN The Right Stuff Supporter

    Local Time:
    4:23 AM
    DD,

    Water flowing through the fairing would, in general, be considered to have a drag increasing effect. The more flow there is the larger the drag effect. The questions are, how big is the effect, and is it worth doing something about it?

    The base-plate inside the fairing makes a pretty decent plug to arrest any flow, but it does have some small flow paths through it that could be better sealed if needed. That is something I will experiment with in the future, although I will be somewhat surprised if it makes a measureable difference.

    It seems to be working pretty well as it is. When gliding and on up-strokes of the fin that area around the base-plate will be pretty deep within wake zone of the swimmer’s body and legs in front of the fin, so I would expect the flow potential to be small producing little water exchange. The effect would be larger on the down-stroke of the kick.

    On the sock issue, keep in mind that this monofin has a solid aluminum foot support (including the heel) and a rigid structure with a tightly coupled fin. When the binding straps are tightened, I have little doubt that the DOL-Fin with 3mm socks will be more connected and responsive to small movements than a flexible hyperfin on bare feet. As I said previously, “The notion of barefoot being preferred assumes certain predisposed functional characteristics of the design of the monofin and foot pocket”.
     
  9. DivingDane

    DivingDane 1BREATH Freediving

    Local Time:
    10:23 PM
    fair enough! that answers that. :)

    they were the only concerns i could see, just figured that a couple of BIG name manufactures had spotted this "Bucket effect" as n issue and have started to design ways to reduce the effect.

    so if they decided to spend so much money on the redesign then i would have thought it would have had a noticable effect on performance.

    http://www.mares.com/videoplayer_2/?region=ALL

    given it has a dodgy voice over and a bit of BS, but it does seem to make some sense.

    DD
     
  10. REVAN

    REVAN The Right Stuff Supporter

    Local Time:
    4:23 AM
    DD,

    Thanks for the link. It was good for a laugh! At least 85% of the content in that vid is BS. The mesh holes in the foot pocket will actually increase the drag on the fin. In my opinion, they added the holes to make the plastic foot pocket more elastic and comfortable. Marketing probably came up with the fluff material on this “parachute-effect” because they like to hear themselves talk. The vents in the fin blade will also increase drag and hurt performance. But these drag penalties are going to be small and it won’t really be noticeable. These features are there because they look cool and people will pay more for it. It’s all marketing.

    Another thought, I’m thinking the mesh holes in the foot pocket are probably not as durable as a solid structure. I can see that tearing after about 4 years of use. Mares is probably looking at product turnover statistics too.
     
    Last edited: Mar 27, 2010
  11. laminar

    laminar Well-Known Member

    Local Time:
    11:23 AM
    I love you, fondue. :chatup

    This is getting more exciting. Ron, I'm enjoying your storytelling approach to revealing the design concepts and challenges behind the orca.

    I'm looking forward to seeing how the new footpocket enclosure works in the water.

    When I dove last year with the DOLfin v.1.0 I assumed that the hard footplate and knobby bits would cause drag, and no doubt they did, but with sinking on FRC it was as if I had no fin on at all. A beautiful feeling. If that low drag glide is improved even further, then that could be very interesting!

    Monofins cause a lot of drag, especially in the sub optimal positions between strokes and in streamline if the angle from foot to fin is wrong or the legs and ankles lack strength and flexibility to hold a good streamline.

    Think of your descents (especially without a line) and how usually some part of the monofin is available or connecting with the water. A handy steering device but it does require effort to manage that.

    With the DOLfin I could go relatively limp and still avoid creating drag with the blade on the way down.

    I think recreational and newer competitive divers will always need to work on assuming a good streamline, as do the experts.

    One accomplishment that the Orca could bring is to create a fin that reduces drag created by the swimmer for nearly everyone who uses it (the holy grail of one size fits all). That would be something. The Orca could take the guesswork that is usually part and parcel of buying a monofin/hyperfin, ie. choosing fin stiffness, footpocket fit, materials, angle, etc...

    And I believe that you can still modify the DOLfin tension settings, correct, Ron, to obtain a more custom feel? Can you talk more about that?
     
  12. Fondueset

    Fondueset Carp Whisperer

    Local Time:
    6:23 AM
    William Chen actually pointed the bit about the glove out - the rest of the saying goes way back.

    Hey Pete - I was at the pool today working up to some easy 75s. I'd do a very relaxed breathe-up - then effortless 50s for awhile. Then I breathed up longer and did a 75 at the same pace. It felt extremely weird at about 60m.
    So I said screw it - cut the breathe-up almost in half and sprinted the whole 75. MUCH better. I was obviously hyperventillating and when the urge to breathe finally hit it felt weird as hell.

    Did 5 of those and 35 50s. Alicia was there and she's really coming along with her monofin. Nice to see.

    Off topic I know - but a little local color doesn't hurt :)

    Dol-fin would be great in the pool. Probly slice through other swimmers without even losing a stroke!
     
  13. DivingDane

    DivingDane 1BREATH Freediving

    Local Time:
    10:23 PM
    Thanks for clearing that up Raven, doesnt surprise me!

    never been a big mares fan for any of there product generally seams to e they focus on looks over function, but then again they cater to the mainstream market which is very image conscious.

    keep up the good work on the fin, look forward to using one sooner or later.

    DD
     
  14. REVAN

    REVAN The Right Stuff Supporter

    Local Time:
    4:23 AM
    The fin responds angularly to the dynamic loads of the water it is acting through and is controlled by an assembly of suspension straps and trim plates. The angles the fin is controlled at will determine how much forward thrust and resistive reaction load the fin generates when being stroked.

    Through the removal of four small machine screws, these trim plates can be swapped out for others of a different setting to modify how the fin will react. Through this method, you will be able to change the reaction load and power of the fin stroke to suit your swimming style without having to go out and purchase a new monofin to do so. From a user perspective, it would be similar to a having conventional monofin that allows you to swap out a medium stiffness blade for a soft blade, or vise versa.
     
    Last edited: Mar 28, 2010
  15. REVAN

    REVAN The Right Stuff Supporter

    Local Time:
    4:23 AM
    As you have probably noticed, the story of the DOL-Fin Orca’s development has caught up to real time and has, therefore, slowed to a near standstill. For the next couple of weeks, I will be focusing on getting ready for the Orca’s sea-trials and some personal training in Kona Hawaii. I expect to have more information to begin trickling out through my website and other communication conduits like this forum in the May - June timeframe.

    I’d like to thank everyone who has participated in this thread so far. This has bean a lot of fun, and I appreciate your feedback and encouragements. I look forward to more lively discussions on this topic in the near future. Once the testing is underway, I’m sure there will be much to talk about again.

    Ron
     
  16. titan

    titan New Member

    Local Time:
    11:23 AM
    when can we have one of those foundueset reviews?!?!?! :)
     
  17. REVAN

    REVAN The Right Stuff Supporter

    Local Time:
    4:23 AM
    Quick update:

    I’ve been getting my DOL-Fin Orca fins ready for Kona. The challenge with this design is producing the streamline fairings, but each time I make one it comes out better than the last. This last part I made was the first part I where I vacuum bagged the composite material to debulk it. All previous parts were made with wet-layup technique.

    The debulked part came out much nicer than the wet-layup parts. The part is strong, thin and flexible and doesn't have a single air bubble trapped inside it. It is also 1/3 lighter in weight.
     
  18. DivingDane

    DivingDane 1BREATH Freediving

    Local Time:
    10:23 PM
    EXCELLENT!!!!!!!!!carbon fibre yes?

    DD
     
  19. REVAN

    REVAN The Right Stuff Supporter

    Local Time:
    4:23 AM
  20. Bill

    Bill Baron of Breathold Supporter

    Local Time:
    1:23 AM
    Since buying one in 1970, I've dreamed about taking the Aqueon to the next level. Then, on Sunday, I saw Ron's latest version of the Dolfin. Almost an hour of one-on-one time with an engineer that could translate marine terms into aeronautical language and I learned more about fins than I had in the sixty plus years that I've been using them.

    Just wish that I was a monofin diver and could evaluate it.