6’1 epoxy dc that ive had a blast riding this summer in typical fla surf:
tail width is a whopping 17.5~!
it does get fun here every so often…
Florida? Oh yeah I see where you said that… Whereabouts?
How do you like those crazy fins? Who made them, and when?
Do you have an angle from the top of fin looking down?
east central near the cape. this is my 3rd board with the vented fins (the first two were twins), and i’m addicted. i went from single to twin in the late 70’s, and didn’t really convert to thrusters with the pack in the early 80’s. a friend who owns several shops let me ride one of his favorite boards a couple of years ago- a well-used greg loehr epoxy slotted twin fin. i loved it, took it to dc to reproduce in poly (pre-clark). the slot in the fins channels water at a defined angle in turns, adding bite and lift at the same time. i’ve riden overhead hurricane surf aggressively with these slotted twins. the quad in the pics is my first, and rides well in 1-4’ surf with a bit too much tail width to my liking for bigger days. i dont have a measurement, but the fin angle from the top is relatively mild and not towed out much on either the front or back fins. here are a couple of more pics from different angles:
pic of a late spring swell south swell:
Hey dean, This is josh-I was the one who gave gunner to you. How’s he doing i know last that i heard he was up in georgia. Nice board by the way, Ive been shaping alot of quads lately under Miller Surfboards. The quads are so fast!
Wow, that’s cool. That tail looks like (Mandala’s) Jobson-designed twinzers.
Is that Jobson on the tail? But the fins are from someone else?
That board does look like a Jobson, I have one that looks just like it with the same fins. One of the best boards I have ever owned.
yes, that is where i the tail came from. wider and somewhat softer on the tail/bat tips and the channel is softer too. dc makes the vented fins, based on a greg loehr twin. nothing but positive feedback on the vented twins from those who’ve tried them. my next board from dc will be a moon tail quad with all fins vented.
gunner is doing fine. sis moved to texas with him last fall. i checked out your photo archive- the quad fish and retro twins are sick!
Very nice. Always nice to see some of the ideas I’ve had in the past that don’t die. This one in particular worked so well … I could never get anyone to make the damn things though. It’s about 15 years old. Now there are pictures on the web , maybe someone will bite. When you understand the hydrodynamics it’s pretty cool. Probably should have put a patent on this one but I didn’t. Now it’s public domain. So have at it dudes … have fun.
Hey GL, nice to see you on this thread–did you invent those fins? I’ve seen something like them before. Do you ride them?
What about that tail?
The obscurity of the GL slotted fin is a textbook example of how the surf industry fin companies have turned a blind eye to radical and innovative technology that works. When I saw Greg’s slotted fin for the first time I said two fins, one tip vortex. Brilliant. Conservation of energy. I like it.
Maybe more expensive to mold, but no more than any car dashboard vent.
But it didn’t take long to realize there’s more to the fin design than that, even though that is one of those really cool “Aha!” design features and should be enough of a selling point in it’s own right. However, there is much more going on in the workings of this fin. For one it’s more than a little like a cheese slicer and from that feature there appears to be a contribution of flow from the flat side of the leading planar lifting surface to the lifting surface of the second planar lifting surface. So not only are there two leading edge lifting surfaces per fin, the second lifting surface receives more lift potential and that potential is focused (and can be intentionally focused by placement) and puts a premium on lifting in the middle or second third of the fin. The potential here is mind boggling. Why? Because, interestingly there may be no significant additional contribution to or increase in trailing edge lift (parasitic drag) because the contribution of flow from the first to the second lifting surface and the way in which it is delivered may possibly have an overall effect of preventing boundary layer separation off the back or last third of the second lifting surface. Thus more than offsetting any possible parasitic drag from having two trailing edges per fin. This would also appear to allow for a somewhat longer base without causing ventilation of air into the flow. Ventilation in it’s common use as in air being sucked into the fins from the surface which causes drag. Sadly most people are confused and call this cavitation, but cavitation requires much higher speeds than those attained by surfboards, somewhere over 50mph, because cavitation is the process whereby water is actually converted into vapor and requires a lot more energy than just sucking air from the surface. But sucking air from the surface can’t be good either. Not if you want to go fast with control. (And also not to be confused with the way the term vent is being used in the title of this thread.) The way I see it, it’s a win win any way you look at it. And all this without adding an extra tip vortex or rather two extra tip vortices per board. Thereby further increasing or adding to the positive side list of potentials.
This concept could use more testing because the overall potential is enormous. Think about it. There is potential for all the benefits of a quad (speed drive control) without the restrictions on maneuverability. Plus more efficient use of fin area means overall less fin area requirement for added speed. But also adding a level of flexibility into design of base length without all the negatives. Have I beat this horse enough?
Taking it to the next level, ask yourselves this: What is entropy? Why is there entropy? Does entropy apply to every system? If you understand that, does it not make sense to make better use of energy through more efficient designs? Organisms that can make better use of energy have generally proven themselves to have a higher rate of survival. (Entropy applies to statistics as well as biology. That is what is meant by all systems. All systems! Like it or not.) So would it not make sense to consider designs in terms of merit (energy efficiency) and not consumerism (greed)? After all professional surf careers are subject to entropy, too, as is every aspect of the surf industry and the universe et al. Systems break down, the surf eventually goes flat. Might as well make the most of it while you can. Why let something silly and unimportant like cultural pressure interfere with having fun? Right?
These fins are much too hard to get and yet the fin industry has known about them for years. I’ve personally seen and even added my two cents as Greg pitched these fins to at least one fin company owner. Still no takers. Why, if I owned a fin company I’d test, mold, market, and even pay GL a royalty for the permission to assign his name to this design. That’s what should be done if anyone wanted to do this the right way. Public domain or not these fins deserve the connection and vice versa.
I don’t want to forget to mention that’s a sharp looking board! Nice pictures and great post too by the way. Hope I don’t scare to many away with mine or step on too many toes.
Just playing the ball from where it lies.
AHA!
But really, is Greg Loehr the very first guy to make this fin? Factually?
(Good post, Mark)
dc said the same thing about your fin- mass marketing just doesn’t get it when production takes extra effort and thought.
thanks for the elaboration!
“When I saw Greg’s slotted fin for the first time I said two fins, one tip vortex.”
Hi Mark -
I’m currently working on a slotted base hoop fin. I.E. 4 fins and an arch with NO tip vortex. Probably not so brilliant but I’m giving it a try.
I also have been playing around with some old recycled windsurfing slot singles in my longboards. They seem to go OK too.
Sheesh - Roy Stewart could probably kick in some good info about now.
I’m not the world’s greatest expert, and I feel like I’m overburdening this thread, but I’ve done independent research on surfboard fins, and I have had contact with some of the worlds acknowledged fin experts. Including fish fin experts, too. Animal fish, that is. And I’ll be the first to admit surfboard fins (and fish fins) are complicated and a hard thing to get my mind around, but to the best of my knowledge the idea of bookend matched mirror image left and right slotted side fins specifically for surfboards that incorporate this kind of angled slot (like a hand plane or cheese slicer) is a Greg Loehr invention.
No one can patent a concept, so even if something similar existed in another field or sport, deep drilling for technology and applying it to other sports constitutes new and original use. So if Greg borrowed any number of similar ideas from single fin sailboards (dangerously close) or from Grand Prix cars or parachutes or whatever and combined them, all or in part all he would have had to do is disclose his influences in the origin of the invention section of a patent application and it would fall under the fair use doctrine.
Only one thing I can honestly say for certain is it’s not my idea. This site is marketed world wide and freely accessible to anyone with access to a computer so if anyone has proof to the contrary or knows someone who does here’s the place for them to post it.
Otherwise lacking such proof Greg’s claim should stand. Keep in mind he didn’t start this thread nor did he make the first claim in it so that would tend indicate that there is already a very real and independent level of acceptance of his connection to it floating around in the universe and attaching itself to people who may or may not even know him.
Still anyone who wants to make one, can. And that’s probably the best thing about this thread. Seeing learning and trying without restraint or hesitation.
I don’t think anyone can go wrong trying.
Oh, hey Mark, I didn’t mean the F1 wing was where he got it–I think multi-element wings on F1 cars were developed after the time frame you’re talking about. I just meant “AHA!” per your comment about aha! moments of design solutions.
Surfers can be conservative about stuff like this, mainly I guess cuz surfboards and fins seem so simple, or rather their organic precursors and inspirations are, sorta.
I wonder how much slot there really needs to be to keep the foil side from developing the boundary layer separation drag or ventilation–I wonder how much higher aspect a fin could be if you developed those slots properly–I wonder how much smaller they could be–I wonder what different shapes you could use… One thing’s for sure, maybe–that umpteenth gen F1 wing up there shows you can put a lot of contouring in the mix when you’re using slots
greg
Welcome to Swaylock’s, isobar.
I got a set of Greg’s slotted twins about twelve year’s ago but I don’t remember them looking quite like that.
We were shaping room neighbors for a long time and used to compare notes a lot. Those fins look more like
an evolution of the ‘‘slotted’’ fin that has been refined, and ridden constantly, by another Brevard County resident
over the last ten years. He wants no part of any mention on this forum, and I respect his wishes. I’ve been riding
them for two years.
Recently, Alfred Maldanado’s 1977 version was posted here also. I’d add the link if I could. The ‘‘shadow’’ fins of the
early 70’s pre-date that and are the first ‘‘multiple-element’’ (F1 terminology) fins that I know of. I’m sure someone
might take it even further back. The concept is widely applied in aircraft also.
BTW, the version I (can’t) speak of is under consideration and testing with a well known fin company.
Mike
Hi Mark, You are the first person that explained cavitation in it’s proper element out of the Surfing world, a term that came from Windsurfing and the Surfing world started using it in the media which drove me crazy. There was a Thread in June of this year which I think you guys will find interesting and applies to this thread. Past, Present and Future Fins. I will bring it back up to the front for you Mark. I think you will like page one of that thread. Mahalo,Larry