This is my Surfteacher Mour Mbenge, riding the 3pc hotcurl at „Secret“ in Dakar, Senegal, Africa. 3 miles away is Ngor Right, the first wave seen im „The endless summer“
And this is the transformer, a 3pc short board for my son, with exchangeable tails, 1 quad and one single fin tail.
Unfortunately not ridden yet, we have a lot to explore end of May… 
I made a fantasy fin, similar to Roy Stewarts (NZ) whale fins out ot scrap veneer. Still needs a gloss coat…
… still needs foiling.
This thing will drag like crazy and spin out when heavy loaded.
It actually is (slightly) foiled, you may not see it in the pics, from the front the width increases to about 1,8cm at 2,2cm depth and dicreases to the back to less than 8mm. But as I wrote it is a “fantasy” fin and I can compare it against a 7’ and an 8’ “classic” single fin. Since I’m more old-school orientated, dragging (if I understand it right finally means increasing resistance, resulting in lower speed) is not of my concern, but the board should hold its line and during wide arcs, it should not spin out. I’m not able to “rip”.
If it does more or less the same work as the standard single fins during my rides it is ok. And I definitely do not not need any high performance fin, being more a “low” performer
Please let me know how surfing this thing feels, I’m quite curious.
Slight foiling is hydrodynamically very close to no foiling at all.
If you look at the drag coefficient of a cube, a sphere is about 2x as efficient. (this is comparable to rounding the edges)
While a streamlined body is >20x as efficient!
Just to illustrate how sensitive the foil is, check the drag coefficient of a streamlined body used in revese, it’s quite close to a cilinder:
Me too:)
Of course you are right regarding hydrodynamics, and you are doing fine, you are optimizing fins.
My attention was more a try to do something with my veneer leftovers, of course the fin should basically work, but by now, the focus was on making something…
If that fin drags, would it be useful for noseriding?
I returned from Portugal already two weeks ago, and your rendered wooden fin, reminded me on this open issue.
Actually the 4 piece surfed very well, it turned even better than exspected. I had the “easter hare” fin (my wife said it does look like the easter hare) installed right from first day and did not change it during the vacation. Since I’m a poor surfer I asked my son to ride it and even he did not exspect it to turn so well. Due to its volume it catches waves quite easily, and it went fast and straight if you wanted it.But finally nobody could tell something about the fin, because we never changed it and had no comparison, but for me, it worked and I did not feel anything unusual. It definitely did not slide out.
After 14 days of daily surf I found out, that in one of the boards parts I had a little water intake, nothing really serious, but I exspected the foam to block against water, because the foam specs say absorbancy rate is only 0,3%. It looks that due to cooling of the board the inside air compresses resulting in sucking and that there must be somewhere a little leak. Actually I did not see anything, so I guess it must be inside the rope channels, where I had to remove some epoxy to make the wire fit. But as said, nothing serious, after 4 hours in the sun, the water drained out completely. Next time I will put some epoxy in the suspicious channel, hoping to have this problem solved. I left the board in Portugal, because I had to bring the transformer back home…
My son rode it, the first waves showed, that it is a nice board board for him. He got his waves and rode them, but after an hour, beeing returned to beach, the front part was literally full of water (there is no foam inside). We thought that there must be a damage somewhere, but nothing to be seen on first sight. I took the board home, and opened it and even opened I did not see anything seriously. The only conclusion for me is, that my son, forgot to close the first valve or that there was dirt or whatever between the screw and the sealing. In the moment the front part is almost repaired. I foamed the inside completely and veneered a layer of walnut onto the bottom. During the week I will glass the bottom again and hope that its watertight now and forever…
Finally a word about the dc’s the drag coefficients. To get the total drag it always needs to be multiplied with the projected surface area of the object and even if the coefficient would be bad with the “easter hare fin”, the efficient surface area is not that large, I think that even an optimized tri fin setup has a larger surface and therfore the total drag of the easter hare fin must not be dramatically higher than a usual tri fin setup. But maybe it was the drag of the fin, that made the board ride for me so well…
As we sat at the beach, the two collapsibles next to us, we had discussions with interested neigbours all day. Wow, look at that, does it ride, what a strange fin etc. etc. If you need contact build yourself such a fin
And once we talked to a young portuguese couple and he offered me to ride his board, unfortunately I just came exhausted out of the water, so I did not take the chance, but it was a CJ Nelson Colapintail 8’3 and the guy was a kind of test rider and produced videos. He went into the water, his wife with a underwater camera and he rode the board insane. He did helicopters, rode the nose, turned like a shortboard etc. etc. I think my next board will be an adaption of this board, a longboard on the short side or a large minimal, no collapsible, single fin, may nicely worked out with wooden veneers. I will not go any longer than 8’3, because this is the length which will be still transported by most airplanes, over 2,5m there are transportation restrictions very often.
“Momma played
base, Daddy sang
tenor”