You guys have heard enough of my rant about no flat surfaces on fins. So, static as they are, I’ll try and let some photos do the talking.
Though I haven’t seen lokbox’s turbo keels, which employ a similar idea, I suspect the foil and layup on mine is significantly different. I hope we can compare with fins in hand. I have taken some of the torsion out of these so the entire trailing edge, all the blue on the fins, are a concave surface. The leading edge in the black area is double foiled.
The fins in the photographs are of the rails for Greg Tate’s 6’11" twin with future boxes that has a 16.5" tail. The fins are 5.625" and of my Cik" template. I took them for a test ride on my 7’5" with Greg’s permission. It was very lively and eye opening experience cause it turns out my board really lights up with large rail fins and even as large as they are I couldn’t feel any significant increase in drag in chest to head high surf.
It’s real hard to show what’s going on with photos. It appears my attempts at capturing the fin shapes has failed. I did my best. I’ll try again sometime in different light.
I’m not much of one for disagreeing but there is no way flat sided fins will have the punch at slow speeds these will. Concave simply pushes harder that a flat surface can.
I think Greg will be the man to make the final call though. After all they are his fins.
Thanks for the observations regarding large rail fins, no doubt they have there place on some boards.
I know that at least in aviation, an undercambered airfoil, which is the same as the concave foil on your fins, is used in sailplanes and other high-lift applications. It more closely resembles the profile of a bird’s wing and was one of the first airfoils to be developed. It makes sense that this design would generate a lot of lift and drive. Flat-bottom shapes and symmetrical shapes will generate less lift and more drag overall than an undercambered foil, it’s actually kind of interesting that surf design is fairly recently catching up to aviation design that is 50 to 90 years old, like undercambers, laminar flow foils, stall characteristics etc. I guess maybe Tom Blake was maybe one of the first to use aviation technology in his boards?
The I shaped the 7’5" in question out of a 7’11" R Super Blue blank myself and glassed it with R.R. epoxy (dbl. 4oz bottom ~ 6oz. deck w/ 3/4 6oz patch)it’s nice and light.
Specks run 15.875"x21.5"x15.125"x3.0"
The rails are completely neutral in the midsection so the board likes to roll into the face of the wave and run on the rail that way. The bottom is modern and somewhat complex. I guess you’d call it an hybrid egg. It’s getting so I’d rather surf it than anything else. I’ve tried many different singles and fin combinations on the board and I’m able to generate more speed and have more board control in the critical part of the wave with the set-up in the first post than anything to date.
I think the word that best discribes the feeling I get off the fins is “lift”. The board doesn’t just turn when you push off the rail it accelerates and at the same time feels lighter in the water.
I’ve tried many different singles and fin combinations on the board and I’m able to generate more speed and have more board control in the critical part of the wave with the set-up in the first post than anything to date.
I think the word that best discribes the feeling I get off the fins is “lift”. The board doesn’t just turn when you push off the rail it accelerates and at the same time feels lighter in the water.
Yeah that makes sense…with those fins your getting more of a real thruster feel…big rail fins for big thrusters. BTW, nice shape.
Rich, It seems as though you’ve put a bit of twist in them? Jim phillips showed me some he called “propeller” fins that he layed up on this little twisted table he made. They looked really cool, and I’m dying to try some. Our turbo CI keels are a fairly stood up template, and a shorter base(6 3/4). The cant is out there at around 10 + degrees, depending on how you set the boxes. They go rail to rail very easily, and feel real squirty through turns. I switched back to the flat ones once, but I think it was the last time.
If there on the rails and I made 'em for a fin box they’ve got a twist in 'em. Flat sided rail fins have always felt kinda lifeless to me.
I’m in Live Oak. If you’re so inclined and in the hood drop me a personal message here on the forum or ring me up. We can have a cup’a’joe and look over a few fins.
I’m not Rich but I’ve used those fins a bit. Here’s my 2 cents worth… Cut a foot off the board, move the side fins back about 7 inches and lose the center fin. Then try it…
Rich, Thank you. Finally, twin fins made for a twinnie board that aren’t just scale ups of a std thruster side fin. I can not wait. But we’re going to need some surf over here, if anyone has any influence there. Maybe I’ll take a dictaphone in a zip lock baggy and record my observations. Or, maybe I should stop being an engineer and just go with it.
this board (8’4", 12" tail) works really well in 2xOH surf with the curved fins, with the center fin, and on smaller days (OH+) without the center fin (definitely looser w/out). I’ve never thought to try them on a longboard…
The fin set-ups you’ve posted are all composed of high aspect fins that will deliver very little power. The way the curve is set in the rail fin with the arc in it will actually have less power at slow speeds than a fin of the same size that has no arc at all. They will tend to cup the water and increase their hold with speed but are not what I would call high performance fins by any stretch of the imagination.
One must remember that every new fin concept is an experiment and that we often learn the most from our failures.
The FCS Red-Tip however, has it’s merits. Because it is close akin to the the keel that was on Australia II when they won the America’s Cup the first time (as is the Horan/Lexan Starfin) it will help the board hold a sharper angle into the wave face and aid holding power. Both of these fins are somewhat vertical so they don’t interfere with the turning radius of the board. The only way to know the difference between these two fins is to exchange two of equal surface area in the same surf conditions. Although both have a winglet at the tip of the fin that’s where the similarity ends. They are templated and foiled very differently.
Hope this helps.
Mahalo, Rich
P.S. Greg, thanks for the kind words – hope you have a good time with your fins. Let me know when you get them and keep us posted on performance mate.
My experience has been on my 5’8" squared-nose stubby and a 6’2" standard shortboard.
For you, I would suggest a longer center fin that reaches deeper into the water column to offest the lift that the curved fins generate… side fins lift for lift and speed, longer center fin for more control.
Perhaps having two longer fins… one with more base than the other… to experiment that angle too.
I have a pair that I threw on a 9’1" with a smaller cut away center fin. I like the feel of them better than the stock fins. Feels like I have more lift in the tail with them.
Those arced FCS fins probably give the board plenty of rail to rail freedom and when you get going they help the board keep it’s trim attitude pretty well.
When I say a rounded foil it means zero flat spots. The whole inside of the arced FCS rail fin is flat, omiting a significant part of the foil. It’s a pretty good sized flat spot at that and seems a pretty primative approach to fin foiling. It’s really not much more progressive than a flat sided fin with sharp leading and trailing edges. With this in mind consider how you would react to a board with a rocker that had a huge flat spot in it. Or better yet go buy Doug Haut’s shop and have a look at one of his rounded-pin high perfromand boards. I think you’ll discover why I feel much the way most of you feel about that sort of approach to board foiling as well as fin foiling.
Or have a look at the attachment. When you look beyond stringer on the board, The vertical cross section of the center fin and the batten on the house do you see any straight lines?
