high aspect ratio longboard fin

Interesting...I remember back in the late 80's or even early 90's, can't remember his name, surfed with a sailboat type keel that was similar to the winglets. He actually had good success with the fin on a short board. It was great in the weak surf. Saw the Huntington pro with him surfing with it. Think he made it to the semis. He glided over those weak sections.

 

I saw that and was intrigued by it too. He makes some great comparisons to F1 cars and fighter jets and the winglets came from sailing as well. The only draw back is that there is this guy talking about it and no footage of anyone surfing it.

 

i remeber seeing fins like that on my dad's sailboards when i was a kid & they look a LOT like the sails used in the america's cup last year, which were modeled off fighter jet wings...& very rigid, unlike sails in the past. makes me wonder if the benefits of the high aspect ratio only kick in over a certain speed...those winglets certainly aren't going to provide any additional lift at the (relatively) slow speeds surfers generally work w/. i also wonder whether he (or they) have taken into consideration the fact that there's a lot more going on as a surfboard moves diagonally through the water while riding a wave...the wave is pushing toward shore, while the surfboard (& rider, if all goes well) slides across the face of the wave. so water isn't just flowing straight over the foil of the fins, it's also coming at it from an angle & being redirected by the fin. sailboats & planes designed for high maneuverability still use low aspect ration sails & wings...airliners use long wings b/c they don't have (& are not designed) to maneuver quickly or in a tight space. same w/ short course racing sailboats...they maneuver quickly, but don't exactly haul ass.
then there's the hugely thick foil right at the leading edge of the fin. look at your surfboard fins...the thickest part of the foil isn't right at the leading edge, it's back a millimeter or so (w/ fcs, look around the front tab, it'll be right about there). & it's also not that thick...surfboard fins have become progressively thinner as time goes on, b/c we've found that thinner fins are more efficient & thicker fins tend to be slower & less responsive. bigger fins, of course, have to be thicker to accommodate the necessary foil, but that's a different discussion.

i have an interesting (& long!) article about fins saved on my hard drive if anyone is interested. it's primarily about fin flex, but i can post it if asked.

 

Very interesting as he does draw this shape from other applications and seems to have done quite a bit of research. It will be interest to follow how these things translate to surfboard performance. The only concern I have is how deep that channel is cut near the base (the one that aids the water flow near the board/fin attach point). If it makes it to thin at that point, it may become a a point where the fin might shear if it hits something (say shallow bottom kick out). However, I'd rather snap the fin than bust the fin box (which happened to a buddy of mine). Thanks for sharing.. something new to think about.

 

i agree 100%, mook. i also think there are a lot of people who DON'T know what they're talking about in any sense of the matter steering people wrong, either intentionally to try & make a buck or b/c they genuinely think they're correct. it's tough to wade through all the jargon & marketing bs out there, which is why i rely heavily on my own observation & research (which is why i constantly have fins for sale...i'm always visiting & revisiting templates, foils, & materials to see what works best.
i'll post the article in a new thread, just to avoid confusion & derailment of this one.

 

That was Cheyne Horan of Australia. McCoy Surfboards adapted a "keel"-type fin to an unusual plane-type board outline that was inspired by Australia's winning of the America's Cup yacht race in 1983. He used the shape on the pro surfing circuit with very mixed results at a time when everybody else was surfing on versions of Mark Richards's twin fin. IIRC, this was all right before Simon Anderson broke through with his Thruster.

 

star fin!

horan's stubborn refusal to surf anything else probably cost him more than 1 world title...

 

not really...

 

Ask Roy Stuart....

 

for pseudo-scientific insanity? no thanks...

 

Utter and complete baloney. How does a keel produce lift? Its vertical or near vert so it can only push sideways via the foil. The hull produces the lift because the vast majority of surfboards are planing hulls. The skeg or skegs keep the hull from slipping sideways so you can maintain desired direction. Multi fin hulls aim the keels in the direction to get us to high trim or bottom turn to top turn. That stupid winglet thing will only produce a cavity of air at speed and with direction changes and will put out the anchor. Why would you want to hold the bow at a certain angle in relation to the water with the winglet thing anyway? I find that angle changes constantly depending where I am on the wave face, I don't want it to be stuck here or there. Wing keels might work on sailboats (displacement hulls) but not surfboards (planing hulls). Snake oil patent medicine at its finest. Anyone who buys this thing is a fool and I have some property in FL that he might be interested in. Sorry about the flame job but I hate to see anyone duped out of hard earned cheese.

 

Bean,

Watch his videos and read his site before you make your judgement. Lift does not equal up and down, it follows the foil of the fin. He goes in depth about how surfers talk about "drive" but "drive" doesn't have a place in physics. The drive you feel from fins is the lift that is created.

You're all hulled out which is good. Have you been reading your Lindsay Lord lately? Naval Architecture of Planing Hulls is where it's at. You can't get the actual book but you can find PDFs out there. If you can't I have a copy I can send to you.

 

The high priest of snake oil salesmen. Cures gout, impotence and hair loss, right? Only costs a measly million pesos!

 

My guess is he and ol' roy were of the same breeding stock. Just because you want to be different doesn't change the fact that a square peg will not fit nicely in a round hole.

 

Got a copy. But that is exactly what I was proposing. Lift up does not come from a vertical keel. Guess that what he is trying to sell me with the wing? But I don't want up lift with a winged keel. The hull does that just fine. I'm not pushing on a fin, I'm pushing on a rail when I bottom turn. I think that is why a sponger can bottom turn without skegs, just not as hard without slipping. And the deck wears out and the fin attachment apparatus does not? Yes I am hulled out which is where I feel I should be.