Has anyone experimented with the floating winged keel, whereas the “wing” is bolted onto the fin and the angle of attack floats. Maybe this could even be a controllable surface with an attachment to the deck somehow. The “wing” could dec/inc angle of attack as you go towards the nose. Imagine if you will a control surface that you could tune as you surf, similar to the ailerons on an airplane. Someone has had to play with this at some point?
I believe Cheyne recommended that people put the star fin in but not screw down the back end, which would effectively accomplish the same thing (although the whole fin pivots, not just the wing’s AOA)…
When I played with wings, the size, shape and angle all contributed to performance at some stage, the only problem was that I wanted it to do all those things all the time. Impossible.
I like your idea though, and maybe a self-adjusting wing coupled with a self-adjusting fin like Blakestahs would be a feesable project. Engineers nightmare, but fun.
I haven’t tried any ‘floating’ winged keel, but I did ride Carl Knox’s Surflock fin system back in the mid '70s if I remeber correctly. To my knowledge Carl was the first surfer to use ‘winged’ fins and it was a real pleasure to meet him on one my trips to US during the '80s. He was a lifeguard on duty when Bob Simmons drowned at Windansea, and it was cool talking about those old days with him. He said Simmons lived in a car… surfing up and down the coast, and made pocket money doing school homework for the local surfers. His system worked really well, but he released it at about the same time that the tri fin broke through, so he didn’t get the credit that he deserved for his designwork. One of the features of his moulded winged fin system was that the wings had rocker…
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He was a lifeguard on duty when Bob Simmons drowned at Windansea, and it was cool talking about those old days with him.
That’s a terrible “claim to fame.”
That is not Carl Knox’s “claim to fame”. Carl was a pioneering surfer at Windansea, as well as in Hawaii. Carl was not the first to play around with winged fins. Alan Nelson was doing it around 1957 or 1958 at Windansea, and I’m sure Alan was not the first either. I think I heard that Velzy had also toyed with the idea.
Hi Bill, I was pleased to hear that you knew/knew of Carl Knox. So many good designer/surfers seem to fall through the cracks… I will never forget meeting Carl in Carlsbad and looking through his old surf pics of the old days. In explaining to me how he figured he had got his wings right, he showed me to his pool and dropped a fin it it. When the fin could finally boomerang back underwater into his hand was when he decided he was ready to tool up…
I am not familiar with his system, explain if you would be so kind. Do you have pictures?
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Has anyone experimented with the floating winged keel, whereas the "wing" is bolted onto the fin and the angle of attack floats. Maybe this could even be a controllable surface with an attachment to the deck somehow. The "wing" could dec/inc angle of attack as you go towards the nose. Imagine if you will a control surface that you could tune as you surf, similar to the ailerons on an airplane. Someone has had to play with this at some point?
To start with, you should ask what you want to accomplish. I wanted to make a rotating single fin to loosen the tail of a single fin while maintaining control, and allow the creation of drive off the bottom.
What performance aspect of surfboard fins are you interested in? Do you want to minimize induced drag without creating vertical lift?
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That is not Carl Knox's "claim to fame". Carl was a pioneering surfer at Windansea, as well as in Hawaii. Carl was not the first to play around with winged fins. Alan Nelson was doing it around 1957 or 1958 at Windansea, and I'm sure Alan was not the first either. I think I heard that Velzy had also toyed with the idea.
There’s the bong fin from Downing…but I guess that was mid 60s
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I am not familiar with his system, explain if you would be so kind. Do you have pictures?
While I only rode the larger fin on a long board, we did discuss a smaller tri version. Here’s some pics that Carl sent me at the time…
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That is not Carl Knox’s “claim to fame”. Carl was a pioneering surfer at Windansea, as well as in Hawaii. Carl was not the first to play around with winged fins. Alan Nelson was doing it around 1957 or 1958 at Windansea, and I’m sure Alan was not the first either. I think I heard that Velzy had also toyed with the idea.
The Velzy V-fin:
This one.
No,the photo you posted is Velzy with his “Butterfly” fin that was produced for him by Fins Unlimited. What I’m referring to are wings,or winglets on the side of the fin.
What performance aspect of surfboard fins are you interested in? Do you want to minimize induced drag without creating vertical lift?
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I am pondering the effects of such a device on a fin, I think the only way to know is build it and test it. There are several ways I am thinking of controling the wing. A) the wings can be tilted up and down by a control on the deck, a lever of sorts… B) A torsion spring loaded in the fin which releases when it feels pressure…Ahhh the possibilities just sound like something someone can spend a lot of time on and get nowhere or spend very lttle time on and get somewhere fast.
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What performance aspect of surfboard fins are you interested in? Do you want to minimize induced drag without creating vertical lift?Quote:I am pondering the effects of such a device on a fin, I think the only way to know is build it and test it. There are several ways I am thinking of controling the wing. A) the wings can be tilted up and down by a control on the deck, a lever of sorts… B) A torsion spring loaded in the fin which releases when it feels pressure…Ahhh the possibilities just sound like something someone can spend a lot of time on and get nowhere or spend very lttle time on and get somewhere fast.
So, the entire hull of a surfboard provides vertical lift, distributed over a few feet fore-aft, which usually results in adequate stability. If you take too short a board on too fast a wave you can stutter, a form of instability in vertical lift (and hull angle of attack).
When you put a vertical control element on a fin, you do add or subtract vertical force, applied to one point behind the center of planing mass. So, increases in lift will pitch you forward, decreases will lift up the nose.
Everything I’ve seen about having one foil on a board looks really hard to control, including the tow-guys foil (which actually has a couple of foils, but they aren’t spread much , enough, fore-aft, to give real stability).
Sure, you can get lift with it, but coupled with the lift will be a little pitch. Whereas the lift will speed you up, I don’t think the pitch is a desirable complement.
MTB has a pair of foils that adjust angle of attack and are stable in one of his kneeboards. Its the only solution that makes sense to me, and I think fin end-plates that are there for vertical lift aren’t a good solution for that reason. You want lift, not pitch, and until one of the foils is in front of the center of planing mass you cannot achieve this.
But, as always, willing to be shown I am wrong…the proof is in the pudding.
Thank you for a concise and well thought out answer. I understand pitch in aerodynamics from flying hang gliders and aerodynamics in college and such but as related to a denser medium like water I still have some learning to do. Looks like I have some research and models to build and play with, I still cant help thinking that some amount of pitch control could be interesting in terms of stall characteristics.
Thanks
que pasa calabasa .
buena vida buena ondas.
Christobal
How about ajustable winged keels… I think this board was famous at one time… : )
No offense to whoever came up with that, but was it famous for being difficult to ride?
A floating winged keel is a great idea. Its about time someone thought of a genuine innovation like this.
The advantage of the winged fin generally, is that it improves the effective aspect ratio of the fin upright. The increased aspect ratio causes the lift-curve slope of the fin to increase, and reduces the drag induced for a given amount of lift (sideforce) produced.
A winged fin should have a better lift (sideforce) to drag performance for a given planform area than the same fin without the wingtip.
I am not impressed with wingtips on fins in general. This is because the lift on the wing tip is not significant compared to the lift produced by the planing board. Also the close proximity of the wing to the underside of the board would tend to produce an interference or biplane effect. The wing tip produces drag for not much lifting benefit.
However, the floating wingtip allows for a much bigger wing to be put on the tip, without the drag penalties of a typical fixed lifting wingtip.
This means the performance of the fin can be effectively increased to a useful range not encountered by normal fins.
For a given fin planform area the floating wingtip fin can be given a higher lift curve slope, a higher lift co-efficient and lower drag than non-floating wingtip fins.
A way to make a better fin with the same area is to make the fin span less and fin chord greater with the floating wingtip added. The greater chord increases the chord Reynolds number and this improves the responsiveness of flow over the fin (better stability of flow attachment). The otherwise greater induced drag caused by the stubbier fin should be offset by the floating wingtip.
The floating wingtip needs be self-balancing and steady so it minimises the drag it contributes.
Such a self-balancing wingtip can be practically improved by making the wingtip fixed at a zero-local angle of attack and by making the wing trailing edge flexible or flapped. The wing trailing edge needs to be transversly straight and rigid or the benefits of minimising the induced drag due to fin tip vortices will be progressively lost.
Its a wonder to me why this concept has not caught on with yatch designers.
I’ll leave the implementation aspects of the floating wing tip design to the practical people out there.
Thanks.