I came across this article on surfline and it was a lot of good information. I recently shaped a quad and had to really dig for most of the information that is in this article.
QUADROPHENIA: PART ONE
Posted: **11/10/09** | Visits: **6339**
| Comments: **22** | <a href="http://www.surfline.com/blog/entry.cfm?id=38677#storycomments">View Comments</a>
Four fins are faster than tri fins.
Four Fins are looser than tri fins.
Four fins ride the barrel higher and tighter than a tri fin.
They drop in easier.
They come out of the gate quicker.
Accelerate on cutbacks.
Do better airs.
Can be ridden shorter.
Draw new and different lines.
 |
| Josh Kerr is one of the half-dozen or so of the ASP World Tour who regularly experiment with quads. |
So why isn’t every surfer on the planet riding one?
It’s all Hype?
Different strokes?
Media?
The pros don’t so I won’t?
Maybe shapers don’t have it right…yet?
Perhaps if there were a ubiquitous effort, a Manhattan Quad Project,
the design would evolve at a faster rate and all would enjoy the
benefits.
Sorry, somebody has to win a major friggin contest on one first.
(Biggest win? CJ won the Body Glove Surfbout on a quad in '07.)
So at this point, who seems to like them and who doesn’t? And why?
Typical first impression of a quad is this: fast and loose, but not
confident without something directly under the back foot. It takes a
few sessions to trust the setup – and run with the positive attributes.
The lack of an auto-centering sensation seems to be a common complaint
from most detractors. Without a center fin, a lot of surfers miss the
instant feedback from the back foot and the ability to do quick
adjustments. With quads there is an information gap in rail change that
varies widely depending on fin (rear especially) position.
Backhand performance is also a concern of 3-fin loyalists. Going
heelside, the rider delivers more power through the rear foot and
specifically the heel. Visualize foot angle and where the energy is
going…for most surfers pretty much in line with the rear fin, three
inches and change from the back end.
Early days of the 3-fin, I’d put rear fins way back on some rider’s
tail blocks. It was necessary to do this to keep more powerful,
rear-foot surfers from blowing their tails out on acute direction
changes. Occy’s were set at 2 3/4" and some of Tom Carroll’s trailers
were as far back as 2" from the end of the board. As rockers and
outlines evolved, the rears crept up to 3 1/4" to 3 1/2" on an average
shortboard.
If a rear fin on a tri is moved up an inch or two from the placement
most people are used to, the board loses drive, hold, and moves the
pivot point further forward. A surfer would have to completely readjust
his rear foot placement. Same holds true with a quad.
Which leads to probably one of, if not the single most important detail
in designing a 4-fin surfboard: fin positioning. Not weird-ass tails.
Not crazy bottom contours. Fins. How big they are, outlines, and foils.
Where they are, their relative positioning with respect to each other,
cant and nose vector.
 |
| Jamie Sterling is a fan of quads in the barrel at Teahupoo 'cause they go fast and hold at speed. Photo: Tyler Cuddy |
Early on I took a fairly simplistic approach to it.
Early quads were an attempt to add drive and control to twins. In 1980/81, Twins were de rigueur.
Since 1982/83, tri-fins were most surfers’ experiential basis. In my
mind, I’m starting with a tri-fin. So I took the rear fin on a tri, and
was theoretically splitting it in half. The more the rider wants the
feel of a tri, the further back and closer together I’d keep the fins.
If a rider was after more of a twin-fin feel, I’d move the rears
towards the rail and the front fins.
My common middle ground: for argument’s sake, a 6’2" tri-fin has fronts
at 11" and rears at 3 1/4". A lot of designers go half the distance on
a quad, so that would put the rears at 5 1/2" and the same distance
from the rail, about 1 1/8". In my humble opinion, I feel this is a
little on the neutral side. I split the difference on distance from the
tail (tri vs. quad: 2 1/4"), which would be 3 1/4" plus 1 1/8"…or 4
3/8". Easier math: 7’ board. Fins at 12" and 4" on a tri. Half the
distance is 6". Split the difference, 5" for a quad. On average, I try
to keep my rears about 2" in from the rail. That’s a generalization. It
becomes a more complicated depending on tail width and board length.
Fin size: Fronts are similar to tri-fins, perhaps slightly
smaller. Rears: profiles similar to fronts reduced approximately 10% in
overall area. You can adjust drive by swapping out rears with different
aspect ratios. More upright fins for tighter arcs. More rake to add
length and draw to turns.
Foils: Your preference on fronts…your favorite tri fin fronts
are a good starting point. If you are a fan of cambered fins – stay
with them. If you prefer flat-sided fronts, you will probably like them
in the trailers as well. Smaller, weaker surf; flats are probably the
go as they react a little quicker and provide instant feedback. Bigger,
more powerful surf – most prefer cambered or dual (full) foil
trailers. Less prone to cavitate and let go. Some prefer full-foil
trailers in everyday surf, citing more “feel”…smoother, cleaner, etc.
Not as fast.
Cant on rears: Typically, I halve the angle of the fronts. It
can vary according to intended use. Smaller softer surf; a little more
cant will add some lift and looseness. Conversely, less tilt will
increase speed, hold, and drive.
Nose vector (line towards nose): I typically point all four fins
to approximately the same place, which depends on board length and type
of surf the board is intended for.
Another shaper’s insight into quads and fin positioning: Bruce McKee
has done nearly 30 years of homework for all of us and he’s quite happy
to share it here.
 |
| Why not chuck a quad in the back with the rest of your quiver? Photo: Tyler Cuddy |
So back to…why aren’t more surfers embracing this design?
I suspect that there were probably a lot of takers that might have had
a go early on before a lot of work had been done. They may have had a
less-than-satisfactory experience and shared it with others that may
have at one point been interested.
Some of it may be due to negative stigma. The print media. In an
incredibly myopic and disappointing “Surfboard Issue” last year the
polyurethane/polyester tri-fin was declared the winner and still champ
in a fizzling technology push.
Thankfully, we have the Internet.
Search and you will find. There are quite a few board builders offering
quads. Even Simon Anderson himself rides and enjoys quads and has
several models in his product line.
My suggestion is that if you are interested, search out a builder who
embraces the design and has a solid history with the setup. It’s not as
easy as just sticking four fins on a board.
More often than not when I let someone demo a quad they are pleasantly surprised.
+++
Check back later this month for “Part Two: A History of Quads,” with words from Simon Anderson, Jeff Clark and more.
+++
BONUS ANSWER TO A COMMENT FROM LAST MONTH:
Last month’s blog on tails, we received a question in response to the Simon Anderson story:
So Rusty - did you build a thruster later that same night? –Munga
Rusty answers:
I tripped on the experience for a couple of days, wrestling with the
thought, was it the board or the surfer? My mind said it was 90% Simon.
After a few days, wtf, I stuck a trailing fin on my favorite twin. My
first surf on the jury-rigged tri-fin was in decent surf but it was not
nearly as good as Blacks on that day I watched Simon. First impression:
board was noticeably slower but had a tentative short burst of speed
out of turns on the better waves. It felt like the parking brake was on
but when I drove off my back foot hard enough the board would come back
up to the speed it had as a twin…just briefly, and as soon as I let
off, it would slow down again.
I shelved it.
The next board I made myself after the twin to tri-conversion was a 4
fin round-tail. It was a super fun board. It had the speed of a twin
but with more drive and a bigger sweet spot. I vividly remember it
doing swooping cutbacks at full speed, almost effortlessly. I rode it
for a few months.
