Text and photos by Wetsand
Thruster Fins
A tri-fin design that revolutionized surfing. Invented by Simon
Anderson and Frank Williams, but usually credited to Anderson. A
thruster has a 3 fins of similar size and template with the center fin
being the stabilizer, or thruster. This is currently the most commonly
used fin set up with the most commonly used foil pattern being
symmetrical for the center fin and asymmetrical outside fins.
Bonzer Fins
The Bonzer fin was conceived by the Campbell brothers, Duncan and
Malcom of Oxnard California, in 1969. The brothers were tired of the
limitations they found with single and twin fins (single fins not being
loose enough and twin fins being too loose. Bonzer fins were originally
a triangle shape and were designed out of a passion for speed and
maneuverability. Designed to fit on Bonzer boards, which boasted the
first single to double concave (which you now see on most thrusters
used in professional competitions) based on Jacob Bernoulli's
principle, the Venturi effect. The double barrel concave inside of the
side fins creates an area of low pressure so the high pressure water
under the front third of the board is drawn to the low pressure area
jetting the water through the concaves and out the back creating speed.
In the beginning there was the 3 fin bonzer, which has a center fin,
and two keel-like triangular side fins that are usually canted and
slightly toed in. Now there is also a 5 fin bonzer option, arguably the
fastest, that incorporates a more rounded template than the original
triangular side fin. The five fin design has about as much surface area
as the 3 fin, but the area is split between two fins instead of one and
the fins are spaced creating another channel for water flow. Bonzers
are all about speed and agility.
The twinzer was invented by Wil Jobson and generally has two larger
toed in fins in the middle and two smaller fin placed outside (closer
to the rail) and closer to the nose than the center fin. Other quad
set-ups often get mistaken for twinzers, but this was the original.
There are unlimited possibilities for fin set-ups...especially in
quads. Toby Pavel has combined bonzer, twinzer and fish designs to
create the Pavel Speed dialer under the Rainbow label. If you put two
speed dialer fins together you'll find a keel fin. Pavel split the keel
fin like the Campbell brothers split the bonzer for their 5 fin. Fin
placement in quads can vary as can the foil, flex, template, cant and
toe patterns.
Thanks to George Greenough for this fin innovation. First tested on
one of Greenough's kneeboards; today most makers of stand up board fins
have at least one flex fin template in their quiver. A flex fin will
angle and create tension through a turn and then release creating
propulsion out of the turn. A flex fin is loose and sometimes less
precise than a stiff fin. Preference plays a big part in fin choice.
Some who go flex never go back and some surfers like stiff fin options.
An optimal flex pattern is one that recoils back into its original
position. A flex fin that doesn't spring back can get a little out of
control. These designs are great for turning and generating speed, but
are not highly recommended for nose riding.
George Greenough has been revolutionizing fin design since the
1960's and he's done it again. The paddle fin and Greenough were highly
influenced by windsurfing skegs. The combination of the stiff leg and
active paddle helps to generate powerful turns. On larger sizes the
paddle makes for great nose rides.
Original concept by Cheyne Horan and designed in conjunction with
Ben Lexcen. Inspired by Australia's victory in the 1980 America's Cup,
Horan thought the keel of Australia II could be modified for use on a
surfboard. This seems appropriate seeing as a boat keel inspired Blake
to put the first fin on a board. Designers are still looking to boats
for relevant design strategies. In 1984 Horan met with Lexcen and after
much advanced testing in the water tank they came up with the star fin
design. In more recent years FCS has introduced a smaller version for
use as the center fin in a thruster set-up. The 3D Red Tip was designed
by Gold Coast surfer/shaper John Harris. Original design influences for
this fin date back to aeroplane wing design, especially the WWII
British fighter the spitfire. Fish, whale and numerous yacht keel
innovations all helped to formulate the star fin concept. This style
fin creates tail lift and positive drive, also speed and acceleration
through turns as well as tip time. The latest contribution to this fin
design was a Laird Hamilton outline released by Future Fins. Same
concept with some of the same characteristics of one of Laird's hydro
foils.
The cutaway fin utilizes a decreased base area with a normal sized
tip giving the fin the look of having the base cut from it, hence the
name. This style fin loosens up the board and is great for turning
because more water can flow perpendicular so the fin with the decreased
base area. Usually used in 2+1 performance longboards and is generally
a shorter length than a standard single fin option (although cutaways
are available in large sizes). These fins are not considered to be
great nose riders, due in part to 2+1's not being great nose riders
(side fins create wobble while on the nose) and also because of the
decreased surface area.
Concept and design by Dewy Weber circa 1965. Original design was for
the Dewey Weber Performer model board. Newer hatchet fin models
incorporate more rake and a more angular tip than the original design.
This style fin is great for nose riding and the increased rake in newer
models has helped to increase the turning ability of this fin. In more
recent years Future Fins have developed a hatchet series. The line
includes two Vector sets with a middle hatchet fin campatable with the
Future box system and a 6" hatchet for a traditional fin box.
The name of the Keel Fin is taken from boat design, which is
appropriate because a boat keel was the inspiration for the first
surfboard fin. The keel was first adapted and attached to a surfboard
by design legend Tom Blake (Nub or Skeg Fin circa 1935). Over the years
others refined the keel fin design (most notably Bob Simmons circa
1946-49) and gave it the basic template that is still used today. The
keel fin filled it's full potential in the 70's when Steve Lis designed
the first Fish. Keel fins are still the most stylish, highly functional
fin used on a traditional Fish. Larry Gephart is the guru of the keel
fin foil and it has been said that you can't have a real fish without a
pair of Gephart fins and, to his credit, some of the greatest Fish
shapers covet and use his fins. The keel fin has more surface area than
the most shortboard fins, therefore, it delivers more drive, and thus,
more speed. Speed, drive, and power all originate at the base of your
fin, but the average shortboard fin has only a few inches of base. The
surface area of a keel fin base usually more than doubles that of most
shortboard fins. If you enjoy experiencing a lot of drive and speed out
of your bottom turns then keel fins are a must, they are a necessity
for any surfer who likes the feeling of fluid drawn out carves. If you
think you know what shortboarding is all about and you've never surfed
keel fins you're missing out. Plus, wooden keels add a little extra
weight which is key for a real nice trim, but the don't weigh you down
because they float.
Twin Fins were first put on a surfboard in 1943 by Tom Blake. His
design, although revolutionary, was crude and very triangular with a
base of about 12". Bob Simmons was the first to put keel fins on a twin
fin. Simmons design was much more refined than Blake's, but it took
Blake's innovations to get there. Other twin fin aficionados include
George Greenough (high aspect ratio), Steve Lis, Skip Frye, Larry
Gephart, and Mark Richards. Richards modified twin fin design by
putting a more modern template on his boards. The shape resembled how
most thruster fins look these days. In the 1970's, when most people
were riding single fins, Mark Richards won 4 world titles riding twin
fins. His style of fin loosens up the board a bit more than the keel
fin. He is still designing fins two of which are sold by FCS, the MR
TFX and the MR-X Carbon Lite. The MR TFX comes with an optional trailer
fin if you want to make your board a tri fin. The trailer is a good
optio for when the surf picks up and/or if you don't want your board as
loose as the twin fin set-up.
A pivot fin has little to no rake. Its turning capabilities are just
what the name suggests; you actually pivot on the fin. The turn ends up
being quicker and less drawn out (not a big carve) than a fin with more
rake. This style fin is a great nose rider. Pivot fin designs include
the Nuuhiwa Noserider (the old DT Pivot), the Fins Unlimited Pivot
9.5", and the straightback (circa 1965). The True Ames Velzy Noserider
and Heritage fins are takes on the pivot. They both incorporate a
template similar to a pivot with significantly more rake than most. The
Velzy Noserider also has far less surface area than a standard pivot
fin.
George Downing is often credited with this design. First introduced
as the Downing Gun Fin; although, the first fin of this template may
have existed earlier possibly via McDonagh surfboards (surf design is
often debatable and begs the question: who did it first?). These fins
are similar in shape to keel fins only with more surface area and a
higher aspect ratio.
