“My latest is the rotating rail fins. The finbox lets the fin rotate in toe-in, and in toe-out. For toe-in, there is a lockout angle that corresponds to 1/4” toe-in. For toe-out, the fin can rotate a good bit further. The fins are stable with pre-load force going straight. The box is the size of two FCS plugs. Anytime you go straight, or nearly so, the board planes noticeably higher than a thruster of similar size/shape. And goes faster. In bottom turns, the board initiates turns more smoothly and easily, holds and projects like a thruster, and then has less drag coming out of the turn. Even for amateur surfers, the difference is easily noticeable if the same board is used (ie: retro-fitting for testing purposes). I made templates that are more similar to the FCS H2 template (but with normal cant and slightly longer chord length and more rake) that seem to go best with the rotating system. " Blakestah
I thought this deserved its own thread…The “flexing” toe-in makes perfect sense to me as it maximizes “squirt” and minimizes drag. The toe-out part intrigues me though.
How does tow-out affect performance?
Does toe-out occur only on the outboard fin during a turn?
Have you tried varying the amount of allowable toe-out? How does that impact performance?
AFAICT, the toe-out parameters are not all that important. Two things surprised me in optimizing the rotating rail fins. The first was the HUGE sensitivity of performance to the angle between the rear fin and rail fin. Its pretty clearly between 1/4" and 3’16" toe-in as the lockout angle. And think about that for a second…if the installer messes up by 1/16" of an inch in the toe-in, or about 1.3 mm, board performance will suffer…anyway.
The second surprise was the bottom turn. Toe-out, or not, really not such a huge difference. I woulda loved to be able to claim the bottom turn was enormously better, but my feet tell me it is very close to the same as a thruster. The difference shows up before you go into the turn, and as you come out. Deep in the turn is the same.
Now, going into a turn…the inside rail fin engages earlier, and more smoothly, as it rotates to a toe-in position. The net effect is that a surfer can turn more aggressively while dropping into steep wave faces. Optimal for barrellage. And then coming out of a turn…the rail fins both stay parallel to the stringer, and you lose noticeably less speed as you head into your next turn.
Also, the board paddles in and planes much more smoothly than a thruster.
The first board I retro-fitted I got from my neighbor cheap. He had ridden it for years. He was sold on the fins after riding the retro-fitted board, noticing all these changes. I just bought a 6’1" competition style board, and it is getting new boxes for the rotating rail fins, and I will see if the early feedback holds up under the feet of the best riders in town…until then…hopeful, but don’t get too excited yet.
Sounds like it could be an answer to my problems with the cluster set-up. The drag in a cluster system always made me surf the board rather than the wave. If you ever engaged all three fins at once, the board stuck. Even when rolling from one rail to another there was a little grab. I found a way around it with Rich’s fins that twisted the toe-in at the base of the fin but lost the squirt.
I spent a bit of time with Tomatdaum at the Cerritos event and he is using a single foiled fin with a double foiled leading edge (I’ve oversimplified the description) to try and accomplish the same thing; reduce drag imposed by the toe-in.
I’ve seen your single fin rotating box and it’s really slick. Maybe once you get down the R&D road a bit further, I’d love to buy a prototype and try it out.
To unsimplify it, I think its about angle of attack. Toms new “next generation” fins combine a outer edge that stays in the same position, with some release on the inner side. Foiling that inner edge outwards a bit and reducing the sharpness of the transition from the inside edge to the outside foil should provide lift or “squirt”, but not fail when the foil gets put into extreme arcs. The foil won’t stall so easy, and most likely handle some serious speed!! Can’t wait to try them if we ever get waves around here again.
I’ve been getting some performance reports on some of my full based templates and another low aspect template called “Cue.”
From what the riders say they’re getting plenty of squirt from the No Nonsense template, which is full based and very generous in profile for it’s size. The “Cue” template is still early in the testing stage but appears to have lots of hold for how deep it is. My take is that my twisted, undercambered foil will give you the sqirit you refer to and that the cutaway template, unless oversized, tends to release at slower speeds more easily which means the so called squirt which is more of a slow speed performance factor isn’t there because the fins wash more easily. On bigger waves the extra speed and lack of stalling do to the low drag ratio is a good thing so they shine there. For many a full based fin is the one that works best regardless of the conditions. I think that on a relatively short board with a wide tail like yours that for smaller waves you will definitely feel a big positive change in performance by moving to more powerful rail fins whether on not they are mine or not.
For the record the board in the attachment is a Manadala quad with 4.75" Mental lead fins and 4.75" No Nonsense trailers. The board comes on great with this set-up.
I made a set of X-2s for T.O. with my foil. I know he’s been real busy but I expect we’ll get a comparative performance report sometime soon.
The work the Blakestah doing on rotating rail fins is most progressive IMHO. It should prove to be very enlightening. I hope to make him a set of rail fins once he gets a little further down the road in the R&D process.
Uhh, my dog ate my home work…I mean my wife ran over my surfboard…So, I left it in Hawaii. I promise I’ll finish fitting your fins before we get any surf, which was the promise I made a month and a half ago and we still haven’t gotten any real surf. At this point I’m teaching myself the APS3000 software because my brother has a machine waiting in customs right now and I’m suppose to help him get started. So, guess where my next board is coming from.
I have to say the rotating rail fins seem like a really cool idea. Just wondering can a fin flex much after it stop rotating? Is the fin box strong enough? Do you have an idea of what kind of templates your going to use…are they going to be soemthing different then the conventional thruster fins? Like the fin on your website… I would think something like the FCS double foiled fin template would be good…
I have to say the rotating rail fins seem like a really cool idea. Just wondering can a fin flex much after it stop rotating? Is the fin box strong enough? Do you have an idea of what kind of templates your going to use..are they going to be soemthing different then the conventional thruster fins? Like the fin on your website... I would think something like the FCS double foiled fin template would be good...
The fin boxes are not breaking so far. But I made it real small, so both the box and fin-to-box joint are things that may change depending on how early testing stresses/breaks them. The fins I use are standard thickness full glass fins, they are as stiff as the stiffest commercial fins. Undoubtedly the hub to which the fin is mounted can squeak a little more flex in it than intended, so the rotation end-stop is positioned “just inside” 1/4" toe-in, and the fins are canted 2-3 degrees less than normal. These “undershoot” changes allow a very normal feel to the fin in a bottom turn wrt toe-in and cant.
The templates have all been single foiled with rounded front edges. I started with Orca-like templates, but that template has a reduced base width. Works well in a center fin, not as a rail fin. The base of the fin must see the most flow velocity for rail fins, so the fin is greatest in chord length there, and the taper to the tip is elliptical (if you plot chord length vs depth, the plot follows a squared relation). Once making that change, I has to adjust rake, a little, as the last generation were a little more pivot-ty than I was comfortable with. And we are currently using this fin as the base, still subject to change depending on testing. But it is converging…
The fin template, overlaid on a 1 inch square grid.
After four sessions on the latest…it goes rail to rail faster and smoother than anything I’ve ever ridden…paddles into waves like it is 3-4 inches longer…I have to take back a little of my bottom turn comments…it comes off the bottom a little, just a little, better than the stock thruster…I think it is the fin template and not the lack of an outside rail fin blocking water, but who knows…it feels good either way. Like butter surfing it. The main advantages to me are ease getting into waves, and speed and smoothness in transitions from rail to rail.
Some pics to complement the text…the board is a new 6’1" Merrick Flyer 19.25 inches wide, 2.5 inches thick, 14.25 inch tail…I got it a little bigger than chippy so I could ride it and dial it in before I give it to the rippers to evaluate.
The fin positions are the same as the original…at least
when the fin is maxed in its toe-in, the leading edge and alignment match the original FCS fins. But here you can see the fins have no toe-in when they are not pushed out.
Closeup of the plug…about the size/weight of a coupla
FCS plugs
The fin template shown above. Note the rear fin is completely unchanged. Also note I need to mow the lawn…
I’m with Rich - this looks like real progress. I’ve got a board that I don’t ride much - (didn’t go rail to rail very well) that I’d like to try this on. Are you going to set up something like a swaylocks “beta” test program for these boxes?
I’m going slower with the rail fin boxes…want to get the kinks worked out to the fine details before spreading the virus…so if the local rippers give it the thumbs up I’ll proceed to production…right now all the boxes and fins have been hand-made by me.
have you tried it with smaller sides as well , with a slightly bigger back fin ? if so , how did that go ?
The first incarnation had 4 3/8" base by 4 1/2" fins with a 4 1/2 base by 4 5/8" deep rear fin…
Not sure that is really a 2+1, but it was a little bigger rear than side fins…
That was a retro-fit. I rode it until it was dialed in and then had its original owner ride it. He was totally sold 100%, wanted these fins in his next board…
But, the fins were a little too pivot-ty, and the boxes weren’t quite deep enough and fins broke…
So, I addressed the major issues with the next boxes and made prototype number two…it has all gone a LOT faster with the rotating single a done-deal. But I’m still surprised how different it all is…
The key with the single was getting the fin right, and getting the fore-aft position right, and getting the rotational stiffness right…
With the thruster getting the toe-in end-stop right has been all important…all that matters is the rail fin angle relative to the center fin during a bottom turn…that is CRITICAL…everything else in the process is just noise…
Except the pivot-ty issue…I increased rake a little and that went away…
Anyway, very fun all around, I hope it rapidly gets to the point where I can share and know you all will see what I have already seen…
I'm going slower with the rail fin boxes...want to get the kinks worked out to the fine details before spreading the virus...so if the local rippers give it the thumbs up I'll proceed to production...right now all the boxes and fins have been hand-made by me.
Feedback from three of the best rippers in San Francisco.
The first thought it definitely worked, generated speed well, got into waves well. He was a little upset at the sensation he got when the fins hit the end of rotation. It was as though there was no fin there, then it hit the end of travel, and the fin was instantly fully engaged. That broke up his rhythm a little.
With that feedback I put new bumpers in to stiffen the fin rotation (toe-in rotation), and left it with two other rippers for the last two weeks. Neither of them noticed the end-of-travel problem. They both found it got into waves earlier than expected, and generated speed better than expected. A very fast board. Of course, there are the usual caveats b/c both of them ride boards 3/4 inch less wide and 0.25 inches thinner and an inch longer…so this one was a little more float than expected. But, the speed was something they were unaccustomed to. One described a layback he hasn’t successfully executed in years…the other mentioned a day his buddy on a shortboard couldn’t generate much speed, but the rotating rail fin board just took off on every wave.
All three testers requested a second, identical size/shape board, with standard fins to compare against…
All three testers requested a second, identical size/shape board, with standard fins to compare against…
It’s important you do this, because the Merrick flyer is supposed to have the attributes the test riders describe ie “got into waves earlier than expected, and generated speed better than expected. A very fast board.”
Instead of making new boards why not put a chock in the box that will hold a given toe-in. Saves time, money and takes weight out of the comparison.
It is already easy to fix the fin in position. Its just a lot easier to give someone two boards, rather than give them one board, a coupla widgets, and a screwdriver.
But for now no second board…I’ve done plenty of good enough tests for me. Six test riders all in agreement…two of them rode boards before and after retro-fitting…
