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  fitzgerald : the drifta - hocker : concaves and fin boxes, 1981

Australian Unorthodox : The Religion of Oz Design
Tracks

May 1981  Number 128 page 17.
Terry Fitzgerald: Drifita III
Rod Hocker: Concaves -They're Functional Rod Hocker: Fin Boxes- Fine Tuning Surfboards

Introduction
Design article detailing Fitzgerald's development of the Drifta Mark III up to February 1981, with small rail fins and a large centre fin in a fin-box.
N
ote that the Drifta Mk III rail fins are flat on the outside and foiled on the inside, reversing the common design.
Terry was a smart guy (he went to university) and he did his homework; technically, this should be the correct foil template for rail fins.

By mid-1981, the Mark VI saw the rail-fins removed, the centre fin box featuring an upright blade fin.
See Surfer, Volume 22 Number 6 page 9, below.

This was the second entry in a three page design feature titled Australian Unorthodox : The Religion of Oz Design.
Other contributors are Dougall Walker, Geoff McCoy, Michael Rae, Phil Byrne, and Col Smith (Newcastle).
See below.


Photographs : Peter Simons
MODEL :
HB 5'9" MK III
HB 6'2" MK III
ACCELERATION: 0-50 quickly.
 
A basic cut-back is a stalling manoeuvre for a single fin and a sliding manoeuvre for a twin fin.
On both boards you wait for the wave - a slowing manoeuvre.
With a Drifta the cut-back becomes an accelerating turn!
The central wide base fin drives the board In a pivot arc determined by the rail fin which in turn provides stability and short arc direction.

POWER:
In drifts, flat or on edge.
The 'power DRIFT' Is back.

ENGINE:
Big base drive fin, two pivotal stabilIsers placed on the first wing.
Swallows or roundpins depending on taste.

TRANSMISSION:
Double-barrelled concave, nose and tall Vs, double wings and edged tall flutes.
Five forward gears, no reverse.

DIMENSIONS:
Round nose for quicker re-entries (points go through the lip, rounds come over with it)
-  a no-nose at all, so to speak.
Hips, and lots of planing area under the balance point.
Foiled and pinched wings.

SPEEDS:
On edge; through the water single fin lines, power plus.
Flat on the face; In small surf, skate and relate to the twin fin reaction times.


HB 5'9" MK III       HB 6'2" MK III
DEVELOPMENT:
The first trl-flns popped up in the early seventies as a result of trying to ride 6'0" boards at 10' Hanaiei Bay.
Feb '80 I started work on blending twin-fin reactions with single fin power, leading to the Driftas.
Oct '80 - on a Mark II 7'4" (broke it at Sunset that winter) the power drift started to show with edged flutes In the barrels.
Jan '81 and Mark III hit the streets, nothing like a wave feeding frenzy, the rest Is history
- Gary Green 1st NSW Juniors, Nick Carroll 2nd Seniors, Steve Wilson 9th Stubbies.


PRICE RANGE -THRILLS: Cheap.

ACTION: Quick.

DOLLAR: Investment capital.

Putting together any new surfboard trip, people naturally are very critical especially if you are sacrificing personal performance in the short term for long term overall development.
Going backwards in your personal surfing to eventually go forward in both boards and surfing, and understanding the value of going to extremes to find a medium value is difficult.
I know.
The results to date with Drlfta development have more than justified the bullshit that has floated around.
Thanks Steve, Nick, Barry, Linda, Greenie and the customers.
There's more to come.
Yowzer!

Terry Fitzgerald

 
1981 Drifta  Mk III (Tri-fin)
Centre fin: 7.5 x 4.5  b @ 4.5 inches (estimation), laminated fibreglass.
Rail fins: 2 x 2.5  b @ 8.5 inches (estimation), laminated fibreglass.

Design by Terry Fitzgerald, Hot Buttered Surfboards, Brookvale.
Note that the Drifta Mk3 rail fins are flat on the outside and foiled on the inside, reversing the common design.
Terry was a smart guy (he went to university) and he did his homework- "technically," this should be the correct foil template for rail fins.

HB MK III - VI  - VII -  8  Drifta Models, June 1981.


Concaves -They're Functional
Concaves Do they track?
Do they increase trim speed?
Are they more responsive through turns?

Do they offer more hold on takeoffs?
Can they be made to function like a flat bottom?

These are questions I have been asked over the past eight years, while I have been designing concaves for surfboards.

The key to all the above questions is subtlety in bottom contours.
Channel bottoms being another possible functional bottom shape are so chaotic when it comes to production that they are not really feasible.
I am speaking from past experience.

Another point to consider about channels is that they are derived from power boat planing hulls.
I'll leave the above paragraph open for debate by the general public or advocates of channel bottoms; so write in with opinions, but please be concise.

Now to get to the theme of this article.
The new breed of concave, that is, a full nose to tail concave, does not track due to flat planes running along the rails.
These planes give the flat bottom feel.
They increase trim speed due to their ability to sit higher in the wave face, just like a fine pintail.
Another advantage is that wider tails can be used for manoeuvrability but still have loads of top speed because they can sit higher in a given wave.
They are faster on takeoff due to hyro-planing action.

Because of their natural ability to hold or compress water they give more drive through turns in any wave conditions.
The same applies on takeoff, you can set your rail a lot earlier because of the excellent rail hold due to concave through tail.

After eight years of development in trying to obtain the same basic flat bottom surfing characteristics, I have finally developed the present day contours which allow flat bottom performance along with the added extras mentioned above.
The bottom shape I have developed is completely functional in all aspects from production to surfing.
All the bugs have been ironed out and the concept suits any outline, twin or single.
Of course you can vary any or all of the integral planes to derive any response you want.

The ease of production compared to channels is great; the shaper naturally has to spend more time on it, up to about half an hour, depending on his skill.
The sander also has to be extra careful.

I am presently using three flyers in the tail on hotdoggers as this allows wider tails and more curve or hip for extra manoeuvrability as well as incorporating the no-nose concept.
Extra vee in tail for quicker rail to rail transition.

Rod Hocker

Fin Boxes- Fine Tuning Surfboards
Over the years finboxes' pros and cons have been discussed in full.
This article is designed to refresh surfers' memories.

Nowhere in the past history of surfing have finboxes been needed more.
Quite a statement you might say, well let's take a new look at the fin box.
With the arrival of "New Wave" surfing, a combination of short boards and a growth in general awareness of surfing's capabilities, the fin box is a must for fine tuning.
Your new stick now becomes multiple in function in large or small surf.


For larger surf set the fin closer to the tail, which increases hold and to a degree eliminates spinouts, when one is powering into a bottom turn on an eight foot wave.
Move the fin further forward to lift the tail so turns are looser in the small stuff.
Cutbacks are easier and an increase in trim speed is noticeable.

Ever had the hassle of your new rocket sticking in the top of a wave?
Fin box is the answer, move your fin slightly forward till you find out where you like it for your style and conditions.
Soon you will pull up at your favourite break, check out conditions, adjust your fin and go out and carve it without the hassle of feeling too stiff or loose.

So what does it all mean?
Instead of you adjusting yourself to the way your new board wants to go you can (within reason) make your new board perform the way you want it to.
I personally feel that twins or singles without boxes are too limited in functions.


Set fins are limited to a certain number of functions in any conditions; with fin boxes a whole new set of performance ranges are available in any conditions.

Let's face it, not everybody can afford a fleet of surfboards, not even the manufacturers themselves (due to costs of materials).
The extra price of a fin box is more than offset by the extra hours of pleasure and adventure in investigating the possibilities inherent in the fin box.
Twins are slightly tail heavy with boxes but performance is not impaired.

Rod Hocker


Tracks
May 1981
Number 128.

Australian Unorthodox : The Religion of Oz Design

Dougal Walker : The Tri-Fin - Did God Mean It To Be?


Terry Fiztgerald : Drifta III


Rod Hocker : Conaves and Fin Boxes

Geoff McCoy: Design

Mitchell Rae: Tails

Phil Byrne: Clinker Bottoms

Col Smith: Conaves 


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home catalogue history references appendix

Geoff Cater (1999-2019) : Terry Fitzgerald : Drifta III - Rod Hocker : Concaves and Finboxes, 1981.
http://www.surfresearch.com.au/1981_Drifta_Tracks_May_n128p17.html