Twinzers: The forgotten four fin design
Last week I was privy to a private conversation about surfboard design. Fittingly it was held in the carpark of my local pointbreak, the speakers stood near the tailgate of a late model ute while I, the lone audience member, sat quietly at the wheel of my van. Eavesdropping is the impolite term. The protagonists had just been for a surf and one of them was assessing the merits of his craft, a quad, while the other asked ever more probing questions.
Did it go alright?
How did it feel?
Mr Quad said, yes, it did go alright, and yes it felt good, he went on to describe the feeling of the board and its performance in florid language. Clearly he enjoyed surfing it. But then the line of questioning took a turn away from the sensory and toward the scientific:
Why was the board so fast?
Why did it perform differently than his last board?
...and the answers ceased to flow as freely. Mr Quad attempted to respond but he was obviously fumbling.
The conversation caused me to think how little surfers know about board design – and I include myself in that assessment. We may understand what particular design features do – pintails hold a line, twin fins are skatey, thrusters more stable – but we don't always understand why they work. I'm talking about the theory of board design here. The physics of water over fibreglass that makes each design feature behave in its own peculiar way. And in the case of fins, the more there are on a board the harder it is to understand why the board behaves the way it does.
An exception to this is the Twinzer, the fin configuration that's best described as an augmented twin fin. For those that don't know, the Twinzer is a standard twinny with two smaller fins sitting just forward and towards the rail of each larger fin. Early iterations also had a narrow tail for increased hold with a concave running out the back. But it was the fins that were the defining feature. The Twinzer was invented in the late-1980s, refined in the early-1990s, although the theory behind them had been used in aerodynamics for many years previous. Unlike most other surfboard designs the Twinzer incorporates a commonly understood physical concept.
The fin configuration was first placed on a board by Wil Jobson while shaping in Southern California in the late-80s. For arguments sake it'd be good to know Jobson's thinking when he placed the fins the way he did. Was it just trial and error experimentation, the method that led to breakthroughs such as the twin fin and Thruster, or did Jobson understand the laws of physics before he created the Twinzer? Unfortunately I couldn't get hold of Jobson for this article so the question remains unanswered.
However, for the time being we'll leave the physics and trace the short history of the Twinzer.
In 1988 Martin Potter was in Southern California and rode one of Wil Jobson's new designs. He liked it and took the idea to his shaper at the time, Glenn Minami of Blue Hawaii. Potter had success on twinnies in the early-80s and in the Twinzer saw a way to remove the “terminal skittishness” of twin fins. With a Twinzer among his armoury, Potter built up a head of steam in 1989 and went on to blitz the world tour winning six competitions and the World Title.
In Australia, Stuart D'Arcy was taking notice. In 1986 Pottz stayed at D'Arcy's Cronulla house during the Beaurepaires Open and the two remained friends. When Potter left Blue Hawaii in the early-90s D'Arcy not only offered to shape his boards but also to go shares in a new label, Pottz surfboards. The Twinzer thus became part of D'Arcy's shaping repertoire. In 1991, the Twinzer went into production at Pottz surfboards with some changes to the tail shape. According to Darc the design sold well.
Pottz Twinzer shaped by Stuart D'Arcy
Back in California, Wil Jobson travelled to San Diego and shared his design with Rusty Priesendorfer who was “blown away at the difference in feel from a conventional twin fin”. Rusty subsequently made “quite a few” Twinzer's paying Wil a royalty for his idea.
As well as being a shaper of principle - how many shapers voluntarily pay royalties? - Rusty is also the best person to explain the physics behind the Twinzer concept. To begin with, many people call the smaller outside fins 'stabilisers' or 'sidebiters' but the correct term for them is 'canards'. The canards, Rusty says, “help punch a hole in the water” before the main fins run through it. When turning a twin fin, the inside fin is pivoting and also holding the board in the water. By redirecting the water flow the canard “creates a wider effective base” on the main fin, thereby allowing a higher angle of attack - read: sharper turns - while lessening the chance of them spinning out.
In short, canards prime the water, allowing the main fin to work at its best – reducing drag and increasing foil efficiency. And the principle works across all fluid dynamics. The theory dates right back to the Wright Brothers; the Wright Flyer biplane had canards when it launched at Kittyhawk in 1903. The term 'canard' means duck in French, owing to the fact the French public thought another pioneering biplane, the Santos-Dumon 14-bis, looked like a duck with its stabilising control front wings.
In modern times canards can be seen on supersonic fighter jets, the most well known being the RAF's Typhoon and the Mirage, used by the French and Australian air forces. Many commercial and private jets also employ the use of canards.
RAF Typhoon with forward canards that increase foil efficiency of the wings behind, the same principle is applied on Wil Jobson's Twinzer
In the mid-90s Rusty extended Wil Jobson's concept evolving it into the C-5. Where the Twinzer was an augmented twin fin, the C-5 was an augmented thruster: it had canards placed outside and in front of the forward fins in a standard thruster set up. Both the Twinzer and C-5 enjoyed a brief period of popularity in the mid-90s before being lost in the rush of retro designs that defined the late-90s marketplace.
However, Twinzers never fully went away, they've always remained around the periphery and with quad fins currently the source of much experimentation it was only a matter of time before shapers began investigating 'the other four fin' design. One of them is Sunshine Coast shaper, and Swellnet's local reporter, Mark Pridmore:
Swellnet: How did you come across the design?
Mark Pridmore: I remember seeing a few in the mags and then saw a Glenn Minami Pottz version about '89. I rode one a few times but didn’t think it went that great, but it was different and I have always been drawn to anything different in design, so I decided to revisit it.
Do you consider it an extension of the quad, or another design altogether?
Not really, although I do enjoy a good quaddy, it's more about being curious about other fin set-ups that offer different performance benefits.
Describe the feeling.
I think they feel free and fast, kinda like a twinny, but they have the drive and hold of a quad fin yet with exceptional manoeuvrability. They definitely aren’t slidey or too loose like a twinny usually is.
Why the Nubbin fin?
Because it adds hold, and with a wider tail or in bigger waves, or even if you just want to push harder through turns, the Nubbin allows that with no slipping.
Have you ridden it without it?
Yes, sure have I've ridden it with about 10 variations. I had to trial lots of things with the entire set-up to understand it and get my version of it to feel great.
What’s the difference?
Without the Nubbin it's looser and some lighter footed surfers don’t need the Nubbin, but I like to push on rail and the Nubbin allows me to do that. I don’t wanna nurse turns...
Best type of surf to ride it?
I ride mine in everything. My current fave is a little 5’5” wide-tailed thing with the Twinzer set-up but with two small nubbins, as I like the feeling of no centre fin, and it adds hold and drive on such a wide tail. I cant stop riding it, I even took it to Fiji and rode it in waves that were way too big for it. But once I got into 'em it went insane, it's just a magic board for me. It's a big call but it's the best board I have ever ridden and best thing I have ever shaped for myself.
Generally I ride it in head high and under waves, but that's thereality of living on this coast and not the limitations of the fin set up.
Where do you think this Twinzer design could lead?
Personally, I like it more than a quad or thruster, and they go insane, though they may be too different for many people.