Wow! Looking forward to trying them both.
Do you use the fin screw and snap swivels as a leash in case they do pop out?
Yes, the little stretchy string hopefully keeps the fin with the board if it comes out of the box for whatever reason. You can also quickly swap fins with another surfer without need for tools, if both boards have a swivel installed. Unfortunately the fins do not float. Maybe a fatter version later on will float, but I wanted to start with the strongest and stiffest print (solid infill) rather than making them stronger if they snap.
You should be able to install the plate and screw either in the front or the back of the box, and due to the stretchiness of the string, have little or no slack dangling around to cause drag. Detail depend on where in the box you want the fin to be. Just put the screw and plate ‘anker’ somewhere so that you can easily move the fin forward or backward by an inch or so while keeping the string pulled straight.
Or insert a pin in the front of the tab in the existing hole, that’s probably the easiest and best solution for locations like yours with seaweed.
I love when saLes pitch says
science a lot and repeats
our fins in between saying
SCIENCE, period.
case closed. Buy stuff
and if anybody asks
say Science.and buy more
beforre you try em, let
a surfer better than me try 'em.
I couldn’t read more than 1/2
the first page.
…ambrose…
where’s Halcyon?
This fin works very well now, no more hum since I modified it according to Cheynes suggestions…HAHAH!
A bit more attention during re-sanding the trailing edge (to remove the remnants of the 3D printing supports) got rid of the hum.
I had another great surf with this fin in my 8’4’’ McCoy Nugget at Currumbin Alley yesterday, in waist to occasionally shoulder height southerly swell.
The fin is very fast and also turns and pivots very well. The board is a MCoy single fin Nugget 8’4’‘, I have not surfed it with a standard MCoy Gullwing fin yet, and have not surfed it much yet at all. But I am very familiar with 7’11’’ to 8’1’’ single fin Nuggets, that’s why I got this 8’4’'. Bigger is better, as long as it’s a Nugget!
I managed to catch waves very early and then generate a lot of speed, and on several occasions people dropped in on me because they did not expect anyone from so far inside. I was catching waves a good 50-60m closer to the point than the bulk of about 20-30 surfers. Buggered if I know why they all sat where they were, close together. Herd mentality.
Very nice work guys!
@MrMik, the resolution can be refined almost infinitely, however files would become quite large and some 3D printing programs are known to fail on those.
“No, too subjective. What’s a ‘marked’ difference? If you want to call it scientific, LARGE sample. I’ll admit my statistics are rusty. Science degree finished in 1984. Haven’t taught science since 95 or so. The easiest way to do a critical evaluation of an experiment is to look at the stats. Maybe stone burner will chip in. Mike”
Sorry it took so long for me to have a look at this thread Mike.
Science is a philosophy of hypothesis, experiment, data collection, replication and (preferably) statistically validated conclusion.
The take home info I remember from my Research Statistics classes in grad school was that you need a minimum sample size of 30 to generate any kind of usable statistics. And differences would have to be very pronounced to show statistical significance.
But to be truly representative of the “total population,” minimum experimental sample/population size should be 5% of the total population.
The larger the sample population size the more reliable your findings will be.
Independent replicates are needed. Increasing the number of replicates increases the degrees of freedom and resolution of the stat analysis. Replication being conducting the “same experiment” multiple times.
You have to decide the acceptable confidence interval (CI) of your standard deviation from the observed mean for statistical analyses. This is how statistically significant differences between results are determined. Two standard deviations on either side of an experimental mean approximates a 95% CI. That indicates that there is a 95% probability that the true mean falls within this range.
Controlling as many variables outside the fin itself improves reliability of results. Board type, size, shape. Surfer weight, height, skill. Wave size, shape, speed.
The Austin, TX or Slater wave machines could be used to control wave size, shape, speed.
Hard to get a double blind study if the surfer can see the fin. Unless you can measure some physical variable, results will be skewed by the subjective mental perceptions of the surfer and his/her expectations.
The number of ways bias can be introduced is very large. especially for subjective evaluations.
Bottom line, correlation does not imply causation. For example, “Ice cream sales are highest in summer. The incidence of malaria is highest in summer. Therefore, ice cream causes malaria.”
Yesterday, I rode the blue BLEF version that MrMik mailed to me. It does not have the carbon tubes as the yellow one above does. It had arrived the day before, but I did not really have time to get it to fit and rode the WG2 the evening before. The next day I did get the BLEF to fit very snugly in the worn stretched FU box with some small modifications and rode it in conditions very similar to the evening before.
First thing I noticed was the fin was more tippy, when paddling, it was easier to sink the rail. Paddle speed felt about the same. When on a wave the fin felt extremely reliable and predictable, but it did not have the same drag free feeling of the WG2. It was not quite as fast, but still faster than my regular raked fin. When turning with some speed The WG2 fin seems to get locked into an arc and it feels like one should not really try and change that arc other than to keep the nose up. After a redirect back to the pocket the WG2 seems to accellerate back into the pocket almost stuck while still accellerating this is one of the most unique ride characteristics of it, and is both very enjoyable but takes some getting used to.
The BLEF did not have any of this. It pivoted off the top and responded to inputs without any surprising behaviors. It just felt solid. I liked it. It had that same pivoty feel, shorter turning radius that is pronounced with teh WG2, but perhaps even shorter and looser. It just lacked that almost astounding drag free acccelleration speed that the WG2 has, and in that second half of a turn back toward the pocket where the WG2 would just stay locked on and accellerate, the BLEF could kind of be broke free making it feel much more like a regular raked fin, but one that pivots faster.
There was no humming. The fin itself fits incredibly well in the worn fin box, thought the BSPs by themselves would never have allowed the fn to stay put. I had to cut out a tab for the fin plate. I used my japanese flush cut pull saw and followed the depressions mr Mik had printed into the fin. Very easy. I unthreaded the roll pin from my old fin which is just a 10-32 ss screw cut to length and threaded it in the hole Me Mik printed in the back of the fin.
In the parking lot afterwards i ran into a very good intelligent and articulate surfer who can ride both longboards and shortboards better than myself. I had previously shown him the fin, and yesterday I handed the WG2 off to him, and he was excited to try it and promised to give an honest review.
He surfs a traditional longboard traditionally, with a lot of style, and I am interested to see what he thinks of it. I can ride a longboard better than 19 of 20 guys, this guy is that 20th, so I am interested to see what he thinks.
I will go ride the BLEF again now even though the cams show a total zoo with less swell, but it is hot and humid
Thanks Stoneburner! Glad yah’ll are still having fun surfing and experimenting with fins! And, sharing it. Mike
Rode the BLEF again. Again i really liked its feel. Waves were smaller more gutless. It felt very responsive and loose and predictable.
The WG2 is definitely faster but this fin is just more responsive and predictable.
I’ve been riding this smaller longboard for nearly 20 years now. Different fins are obvious, statistically subjective or not. This fin has the best overall feel of any fin/fin combo I have yet used in this board.
Thanks for the great reviews, wrcsixeight! I am most pleased that the fins seem to perform well. Hope they don’t end up snapping off after a while, but in that case the carbon-rod build version is ready to be re-employed. Less carbon rods will be required than I initially used, and therefore no modifications to the location of the ball spring plungers required.
I found a most interesting thesis about optimising tubercle placement on airfoils, I’ll try to have a good read of it soon, unfortunately most diagrams have been removed from the online version: https://www.google.com.au/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwji19LX8LvVAhUFFpQKHaCLB7IQFggoMAA&url=https%3A%2F%2Fdigital.library.adelaide.edu.au%2Fdspace%2Fbitstream%2F2440%2F79211%2F8%2F02whole.pdf&usg=AFQjCNG8wevJcNr2BSWqaFfMU8Xl9v2x0A
From the summary:" The investigation has shown that for all tubercle arrangements investigated, increased lift
performance in the post-stall regime comes at the expense of degraded lift performance in
the pre-stall regime. However, it has also been noted that through optimizing the
amplitude and wavelength of the tubercles, pre-stall lift performance approaches the
values attained by the unmodified airfoil and post-stall performance is much improved. In
general, the configuration which demonstrates the best performance in terms of maximum
lift coefficient, maximum stall angle and minimum drag has the smallest amplitude and
wavelength tubercles. A new alternative modification has also been explored, whereby
sinusoidal surface waviness is incorporated into the airfoil, giving a spanwise variation in
local attack angle. Results indicate that optimisation of this configuration leads to similar
performance advantages as the best-performing tubercle configuration. It is believed that
the flow mechanism responsible for performance variation is similar to tubercles."
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So what that means, I think, is that more smaller tubercles might be better. I designed the bumps on the fin that you have surfed just by what looks right to me. There is every chance that smaller tubercles might cause less increase in drag for the gain in delayed stall. But, intuitively and by following the bio-mimikri approach looking at the humpback whale fins that started the whole tubercle thing, I think that tubercles should be of varying size, probably proportional to the width of the fin where they are located.
Scaling down the height of the fin only (to make slightly smaller or larger versions) might throw out the amplitude to frequency ratio of the tubercles.
Screenshot shows 100% size, 80% shrunk along x-axis, 50% shrunk along x-axis and shrunk even more for the last one, just to make the effect obvious.
Roy Stewart was the first to put bumps on surfboard fins, as far as I know. Just a little reminder, not to start a Swaylocks war over it, but I just want to give credit where credit is due. I think his fins most likely also have been designed using finFoil. http://www.finfoil.io/
I’d be gutted if/ when the BLEF fin breaks. I’ve only had one backside bottom turn where I really loaded the fin with about 85% of my ~210 lbs, and the lesser flex compared to the WG2 was noticeable. The projection afterwards was not as pronounced but there was none of the wg2’s slight tracking to deal with. I have not done the full try and load the fin to breaking point as I have done with the WG2 before coming to the conclusion that it was not going to break from water pressure alone. I’m not there with the BLEF, but it did hit sand on one duckdive without issue.
The WG2 allows quicker redirects compared to a traditional raked fin and the BLEF takes this to a new level. It also seems to allow for these redirections when trimmed further up on the board. I had a few where I threw it up on a floater from much further up on the board than I expected to be able to do from there. There was not really enough turbulence to compare WG2s seeming immunity to white water turbulence to the Blef, but I made it over to the bottom, initiated another turn to seek open face again, and attained it.
With the WG2 and my other fins, I could get that sucking sound coming from the tail on the second half of a turn, and much of this I attributed to the soft rails off the tail on my boards. It was reduced with the WG2, and I have yet to hear it at all with the BLEF. Often the noise would occur when kicking out of a wave that was closing out or after there was no usable shoulder left, and this is absent with the BLEF, so far, and the board is pivoting around much further than expected on the kickout, compared to what I am used to, and I am very familiar with this board. The WG2 had this too, withth eboard swinging much further than expected on a kick out but the BLEF had me facing well past a 180 on the kickout. Makes me thing the carving 360, by a better surfer, could be accomplished much easier with this fin than others.
Comparing the WG2 fin to the BLEF gives more insight into the Wg2. The Wg2 really seems to get a lot of traction and likes to stay in that mode. Transitioning from one rail to the other on a top turn the WG2 felt like it was locked onto a track that I tried to follow and maintain the speed, whereas the BLEF was like ’ you want to go there, then so do I, but lets not outrun the section or run too far into the flats.
If the WG2’s inherent speedy nature in trim mode could be combined with the easygoing predictable and forgiving nature of the BLEF…
Both these fins have me rethinking everything I though I knew about fins.
The BLEF fin today got a couple complements on its appearance by young kids, and in direct sunlight seems to glow some sort of nuclear blue.
With the dropping swell, I hope it wants to fit easily in my bigger younger longboard tomorrow. Its box is not quite as wide/stretched/worn in the middle. I do not think I want to narrow the BLEF’s base to fit it if not, as it fits so nicely in the smaller LB’s box and works so well in it.
Will the 3d printed fins become more flexible/weaker in time with repeated flexing? What about maximum temperatures/ UV exposure? Is there any difference between the red and blue and yellow in terms of strength as far as you know?
Good questions! And thanks again for your eloquent and detailed ride reports.
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The PLA will weaken at temperatures well below what can be reached in a car when parked in the sun (60-70C) . So keep the fins out of extreme heat.
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I have done a few experimental prints using a PLA material from Germany called PlaTech, but in my experience it is much weaker than standard PLA. It might be strong enough when carbon rods are used in addition to the printing techniques used to maximise the strength of the PLA, but the stuff is too expensive for experimenting while the printer is less than perfect and the fins are prototypes. And the PlaTech is not transparent, a massive problem when troubleshooting 3D printing problems. But once the techniques and fin templates have matured more, and complete print failures will be less likely, then the PlaTech material might come in handy, because it stays solid to well above 100degC. Shame I can tear it to shreds with my bear hands, hopefully it’s due to some mistake I am making with print settings, but their weird claims that the filament is stronger when printed at lower temperatures (that is contrary to what ? all ? other filaments do) makes me wonder if they don’t have the basics straight just yet. But I do believe that their heart is in the right place and that their filaments are likely the most environmentally friendly and bio-degradeable filaments available yet. I might be wrong.
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In other words, with the use of carbon rods as strengthening inserts into 3d printed fins, I could most likely print fins that are resistant to being left in a car when parked in the sun (unless you leave the fin on the dashboard, because somewhere around 110-120degC this material also starts to go goopy). The fins would mostly be made of renewable resources and be bio-degradable.
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Regarding UV exposure, I have no idea.
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I have had it on my "To do list’ to ask my filament supplier if there are likely differences between different colours. I know that some colours have slightly different extruder temperature specifications. The colours I used recently are the ones that I found to be specified as 220C maximum printing temperature. The blue filament was the last one in my supplies that has 230C as max printing temp. I always use the maximum nozzle temp so far, possibly due to lack of sophistication when setting printing parameters, but I figure that inter-layer adhesion is the weakness of fused filament deposition printing, and the hotter, the more they melt together to increase strength. I might be wrong.
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It is possible these solid-PLA-printed fins might snap off due to insufficient mechanical strength, and it is possible they might weaken due to repeated flexing during use. I just don’t know. But, so far, none have snapped, including those with 5% infill instead of 100% infill. But it is early days and only using them in the real world will give a definite answer. Roy Stewart’s fins were printed from polycarbonate, a much stronger material than PLA, but they had the same amount of infill throughout the fin and fin base. For large single fins like the Gull-whale fin, the mechanical stress was eventually too much and they snapped off at the top of the fin box. The smaller fins that Roy sells are probable never going to snap, but I have never surfed one. With use of ‘Solidifying-micro-cylinders’ or any other way to force 100% infill in the highly loaded areas around the base/fin junction, Roy’s large fins would probably last very well (and I would not have started out to make my own fins).
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In my experience, fins snap off not during powerful bottom turns, but when riding flat through the trough of a very sucky wave. My hypothesis is that this is a time when the board sits fairly flat on the water, but the water flows perpendicular to the board and hits the fin side-on, causing the board and surfer to be sucked up the wave face and hopefully into a barrel. While in a barrel in trim, I assume the situation remains the same (i.e. almost the entire weight of the surfer is loaded onto the fin while the board is near flat on the curved wave face), but I’ll have to defer final conclusions until I have achieved that state a few more times.
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Very nice write-ups from designer and riders alike.
It seems like another way to shorten the fin would be to ‘slide’ the fin base towards the tip of the fin in CAD, one bump at a time, until the desired length is achieved.
Great idea! That would probably work perfectly for the high aspect ratio BLEF fin. Just shorten it a tubercle at a time, brilliant!
One design covering from industrial wind turbine blade to nubster fin?
A spontaneous observation.
It occurred to me yesterday that tubercles are biological versions of wing fences.
That they occur on large cetaceans makes me wonder if they are needed because of the animal’s mass.
Biological yes, but maybe more importantly sinusoidal versions of wing fences?
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I’m enjoying reading the above mentioned paper, I can only recommend it so far:
“1.6.1.4 Restriction of Spanwise Flow
Wing fences, as depicted in Figure 1.8 from Williams (2009), are flat plates fixed
perpendicular to the suction surfaces of the airfoil and parallel to the airflow which
provide an obstruction to the spanwise flow along the wing. For swept wings, spanwise
flow contributes to a higher loading at the tip region compared to the inner portions of the
wing, which generally causes stall to initiate at the wing tip (Reithmaier, 1995). This is
undesirable because a stalled wing tip leads to reduced effectiveness of the ailerons,
especially at slow speeds and high angles of attack (Reithmaier, 1995). Tip stall of a
swept wing also causes the centre of pressure to move forward, which produces a nose-up
pitching moment that becomes more significant as stall progress further inboard (Bristow,
2002). Eventually this may lead to the highly undesirable deep-stall condition which
occurs when excessive downwash over the tail section reduces the effectiveness of the
elevator (Swatton, 2011). Other methods of spanwise flow control are the sawtooth
leading edge, the notched leading edge and vortex generators. Rather than providing a
physical barrier to the spanwise flow, these devices generate streamwise vortices which
achieve the same effect (Swatton, 2011).”
Wing fences offer their greatest advantage for swept wings.
Humpback Whales can change the sweep angle and washout of their pectoral fins.
Pectoral fin flex, washout and sweep are not fixed/static like a standard surfboard fin.
EDIT:
With regards to biomimicry, the question arises. Why do we not see tubercles on all cetacean fins?
A fin incorporating this technology would be the equivalent of the Back to the Future hover-board:
1.7.2 Drag Reduction
1.7.2.1 Vorticity Source in a Boundary Layer
Magnetohydrodynamic flow control can be used to influence the flow of electrically
conducting fluids such as seawater. Arrays of flush-mounted electrodes and sub-surface
magnets are used to induce a current-density field and magnetic field in the region of a
wall. The resultant three-dimensional Lorentz body force is a source of vorticity which
can be controlled both temporally and spatially to influence the boundary layer vorticity
field. Wall shear stress reductions were measured by Nosenchuck, Brown, Culver, Eng
and Huang (1995) for both laminar and turbulent boundary layers. It was proposed that
the mechanism of drag reduction for laminar boundary layers is the restructuring of the
vorticity field and for turbulent boundary layers, the interference with coherent motions
responsible for turbulence production (Nosenchuck et al ., 1995).