Credit Given Where Due

This was Bill Thrailkill’s Design. Well posted and discussed here already.

Thought too.

Reminds me of the time Patagonia founder, Y Chouinard, asked Greg Loehr if he could come to FL and learn all about epoxy and EPS surfboards. Greg opened his factory to YC and spend to 2 weeks with him showing him everything. YC won the SIMI award that year for Environmental for his epoxy boards. In accepting the award, not one word was mentioned about Loehr. He shrugged it off. But obviously, I haven’t.

I suppose Mr Purchase could have developed his twin fin arrangement on his own without knowledge of Bill, It happens. But, many of us here know what is happening on the cutting edge. I’m surprised that more people would not be aware of Biull’s long standing work. And the standing joke here about so-and-so having done something years ago that we now regard as new.

Bill’s design was is his own. It’s entirely possible that NPJ arrived at a similar (NOT identical) design in isolation. Even so, 6" apart and 1" apart a different enough to distinguish the two designs as different.

NPJ’s is closer to some very old wide tailed twins than a novel single fin adaptation.

As I said over on the erbb, with all due respect to Bill Thrailkill he is simply not a household name for Australian surfers, and had I not spent considerable time on Sway’s I wouldn’t know much if anything about him or his designs.

Anyway, NPJ has given credit to others including BT here.

“The board uses a normal twin-fin setup, but with ‘larger fins that are traditionally used only on single-fin surfboards’.”
(Normal twin-fin setup is 6" apart?)

Seems like Mr. T’s core concept is/was twin, traditional single fins.
If the fins were 1.5" apart, would that be significantly different?
What is the critical distance between 2 traditional single fins that makes a concept/design different?

What does household recognition have to do with who developed a concept?

“What does household recognition have to do with who developed a concept?”

Nothing…Just pointing out it is possible NPJ has lived his life surfing and shaping on the other side of the Pacific without having been exposed to Mr Thrailkill’s designs (or this one in particular).

I would also consider them quite unrelated.
The unique properties of the Thrailkill twin fade away the further you put the fins apart.

This design looks more like the twin fin used in windsurfing, than it look like the Thrailkill twin.

I’ve been studying the Thrailkill twin setup, and am a strong believer of the concept.
But I am convinced this is not one.

Traditional biplane wing spacing is/was one chord length apart.
I measured the chord lengths of my 9" and 10" single fins, up 1" (25.4 mm) from the base. Chord lengths were 5.5" and 6".
If we consider Mr. T’s twin, traditional single fin configuration to be a biplane variant, then a 5.5"-6" separation/spacing of twin, single fins would fall within the biplane concept.

You should compare gap to mean wingspan, not to chord length for the biplane effect.

It’s easy to imagine that two bonzer runners one chord legnht apart have less biplane effect that two formula windsurfing fins one chord length apart.

But it is not so easy to see a Bonzer runner as similar to a biplane wing.
Biplane wings had/have a much higher aspect ratio and had/have fairly uniform chord lengths for the entire span of the wing.
Just sayin’

Exactly my point.
The fins of this shaper also have a low aspect ratio compared to biplane wings.
You need to compare to mean wingspan and not chord length.

Look at figure two in:
It is titled: Figure 2. Munk’s Span Factor Dependence on the Gap-to-span Ratio

BTW the spacing and design of biplane wings was more influenced by structural than aerodynamic reasons

Yes the gap to span ratio concept makes good sense. Gap to aspect ratio might be a good comparison also.
But we must be looking at different fins.
The NP fins look like they have an aspect ratio closer to biplane wings than Bonzer runners.

Closer, but not close enough to make up the gap.
The bonzer runners were just an illustration to highlight comparing to chord length is not valid.

“Slot Effect” from sailing and directly opposing foils. One of these setups makes direct reference to those design concepts.

Meanwhile, there are references to actual twin fins from the late 1960s. Here’s one such blog post"

And the fins entry at 1970 early twins referenced 2/3 down:

I don’t think the Duo is Bill’s design. The Twingle and the Duo are very different and are designed for different reasons. Bill’s Twingle is his way of making a better single fin. The position of the fins doesn’t have the advantages of fish boards with the fins out on the rail.
The Duo tries to capture the best of a twin and single. The wider spacing is suited to the shorter, wider tailed boards, and with no toe or cant, there’s less drag.
I’ve made my interpretation of both. My current Duo is a short board made for better waves. I’ve pushed it hard and it seems to work well, but it doesn’t have the instant speed that boards with fins on the rail have. It’s more like a single for wider tails. Really good for in the pocket surfing.
Add a couple of boxes on the rail, and the Duo can be a nice quad with a fin setup similar to the Gemini.

I’ve been through 4-5 pairs of gloves from them - Lost track…
Every pair has developed a major leak in the palm, in less than six sessions - straight up crushed neoprene, or what ever crap they use - they still look like new.
They have replaced them - although I’ve spent as much shipping back the leaky ones, as I spent on the first pair.
I pointed out to them - for a company that touts itself as being green, selling shit like this that is going straight to the land fill is kinda sad. Maybe the gloves suck because they are made out of green-biodegradable material. But, this reminded me of people’s ability to say one thing, and do another.

For what it’s worth - I’ve given Greg credit when every I talk about my use and love of RR epoxy, and not using vents on eps… Ha!

Well they grow that rubber on a Yule tree in the desert out by Bakersfield. The same in documented workers that pick Pisstachios for Paramont farms cut the Yule limbs with a Machete then chew it until it’s hand and moth processed fiber. Can’t get much greener than that. As a marketing ploy it is extremely Green$$$$$$$. Greener Resin would be Supper Sap not RR.

I came up with that design years before. But I discarded it because it limited my airs and ollies.

Add a couple of boxes on the rail and it will tombstone to the bottom of the sea.

…I ll play the Devil s advocate an immolate to say that is very simple: The Aussie guy is a hipster guy with all the contacts around the world so he can travel here and there promoting his ideas (or other ideas).
Bill T has another age, nor hipster and retired shaper; the only point is that he lives in California; if not nobody were in the known of his design.
So the potential to show something are not the same.
I can add that I saw couple of clips showing the Aussie shaper shaping one of those bulky outdated shapes in France and the guy is just a rookie shaping boards; the technique (or lack of) the protocol to shape it; the time to put on that job; all pretty amateur.
But yeah, I lived that in Japan; when the importers showed me outdated amateurish shapes (but with excellent or very good glass works that saved them by the way) saying how good ¿? “x” shaper is…

The ‘‘Twingle’’, has the fins on two inch centers. Flat sides out, foil cambers facing each other. Higher speed water flow, between the fins, creates a lower pressure area. Not a true venturi, but a ‘‘venturi effect.’’ The camber on a single foiled 3/8th inch thick fin, is the same camber to be found on a symmetrically foiled 3/4th inch thick fin. The performance goal of the design, is the dramatic reduction or outright elimination, of fin stall during high AoA maneuvers. The feeling experienced by the rider, is like having the gas peddle down all the time. Said another way, tapping more of the kinetic energy of the wave, throughout any maneuver. I hope this is helpful.

1 Like