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When it comes to the new
high-performance foils, there are more and more options
to dial-in. This article will try to demystify these
options, and help you dial-in your new hydrofoil to suit
your riding style.
In the beginning, foilers had to
make some drastic changes and “tune” the original Air
Chair in order to maximize the potential of the sit-down
hydrofoil. Since Sky Ski was started in 1998, the need
to actually “tune” your foil was much less of an issue
and required much less work, since these foil
incorporated all of the “tuning” modifications from the
previous years. In the past few years, Sky Ski has
improved manufacturing process and material of foils,
i.e high-strength billet aluminum, CAD design, computer
numeric controlled parts, metal extrusion. The new
foils hardly need much tuning, but now we have different
wing options, wing placement options, and strut
lengths. This gives the rider more options to “dial-in”
to suit their riding style and changing water
conditions.
So, remember that “tuning” deals
with reshaping/changing the foil and “dialing-in” deals
with setting the right options. These options include…
1)
Shimming – slightly changes the angle of attack
of a front or rear wing with a shim.
2)
Wing Positioning – moving the front and rear wing
closer together or further apart.
3)
Wing Selection – Different wing designs have
different riding effects.
To understand the basics of
“dialing-in” a foil, please refer this article. This
will help you understand what terms like quickness and
lift mean, and the basics on how to adjust quickness and
lift.
http://www.foilfreaks.com/articles/lexdialing/LEXDialing.htm
Now, let’s talk about the high
performance options that have occurred in the last 3
years, and what effect they have when foiling.
a)
Longer struts (B-39 & LE38)
b)
2003 Batwings (front and rear wings)
c)
2005 redesigned-Batwing (front wing)
d)
2006 Mini-Batwing (front wing)
e)
Front Wing Positioning (additional front fuselage
bolt holes)
Longer Strut Lengths
From a rider’s perspective, there
is not much to dial-in when it comes to strut length.
The B-39 is the only foil today that allows for
adjustable strut length. What a rider needs to be
concerned with when it comes to a longer strut length is
that it may take a few rides to get used to the
difference…
Why should I get used to the
difference?
The benefits of the longer strut
will first be apparent on the landings. Basically, it
just gives you more time to regain control on a
landing…the wings have a bit more time to clean off air
pockets and regain flight before the board smacks, the
rider has a bit more time to situation himself/herself
to control the foil before it pops back out of the
water, etc.
The longer strut will also help get
people in the air higher, because the foil has a more
time to accelerate through the water before exiting,
especially when you figure out how to time the take-off
properly and start using more of the strut length during
take-off.
What is the difference?
There are two main
differences…swing weight and take-off timing. These
foils are a little bit heavier, but that won’t take much
to get figured out. The swing weight is in a slightly
different place (further away), so it may take a few
off-axis inverts to get it figured out, but it’s not a
big deal.
During the take-offs, you will need
to be slightly more patient so that the foil has time to
exit the water before starting into your maneuver. The
foil is a bit longer, so you’ll want to start flying
higher and start the dip from higher up to make good use
of the extra inches. And…you’ll need to get used to
more hang time, because it will put you in the air a bit
higher.
All of these things will be easy to
adapt to after a few rides, and the benefits are
positive…bigger air with more control.
For the B39 foilers…which strut
length setting is right? I’m not sure there is a
definite answer to that. I’d recommend picking a strut
length that feel comfortable, then dial-in your wings
(more described below), and possibly tune up the foil
(if necessary). After you get comfortable riding at a
longer length (in general), try a different length
setting… re-dial the foil and see if the length change
is better or worse for you.
Batwing Designs
The batwing refers to a wing that
has some of the trailing edge removed, when compared to
the traditional straight trailing edge wing. Removing
the trailing edge of a wing mainly adds quickness to the
setup. Instead of sliding the wings closer together,
you can remove the trailing edge of a wing and make the
foil quicker. A smaller, secondary effect is that the
foil will be a bit more loose feeling when leaning left
and right, compared to a straight trailing edge wing.
So adding a rear batwing will give a bit more quickness
to the setup, which can result in a slightly steeper
take-off. This will feel like the foil “pops” better
out of the water. Most people prefer using a rear
batwing.
The front batwings (’03, ’05, and
’06) also have the trailing edges removed, but the ’06
mini-bat has a very small amount of trailing edge
removed compared to the ‘03/’05. With less trailing
edge removed, the wing will be less quick and have a bit
tighter feeling when leaning left and right, compared to
the ’03 and ’05.
There is one more variable that the
front batwings add. The batwings either have more
material in the front of the wing, and/or the bolt holes
are drilled in different places on the wing, compared to
the tradition straight trailing edge front wing (the
most popular front wing for the LEX). What this does is
push the nose of these wings further forward over the
front of the fuselage. We’ll talk about this effect
next, since it ties into the multiple front wing
placements on the front fuselage.
Front Wing Placements
The LEX with a straight trailing
edge front wing has about 1 inch of the nose of the wing
in front of the fuselage, and it offers no
adjustability. The 2003 front batwing is about 2.5
inches in front of the fuselage on the LEX…again no
adjustability. All of these measurements might not be
exact, but it will give you a better idea of the
concept.
What happens when you move more
of the front wing past the front of the fuselage?
Two things…
1)
Increased Lift
2)
Increased steepness of the take-off (partial
effect of increased quickness)
Both of these are usually good
qualities, but too much of them can cause an unstable
and difficult ride, which leads to a greater learning
curve or a loss of riding potential.
First, let’s talk about the lift,
and this is another MAJOR point…
Do not select a wing placement, just because of the way
it affects lift.
Again…
Do not select a wing placement, just because of the way
it affects lift.
You could be sacrificing increased
stability (greater riding consistency) just to get lift,
which can be solved by the angle of attack of a wing
(shimming). So if the front wing has really good lift
in the forward position, realize that moving it to the
back position will decrease lift. You will need to shim
the rear wing to regain the lift that you like. Without
doing this, you will not be fairly comparing the
quickness, take-off, and overall stability of the wing
placements.
So what might you notice wing a
front wing in the forward position versus the back
position?
A wing in the back position might
feel a bit more stable and a bit more predictable on
take-offs and landings. As you move the front wing
forward, the center position (center of mass) of the ski
actually changes a bit. It is kind of difficult to
explain, but imagine just sliding your butt off the back
of the seat a little bit when riding on a straight
trailing edge front wing setup. You are sitting further
away from the front wing (center of mass), so you either
need to compensate by leaning forward or using foot
pressure to keep stable – it’s not that the ski is too
lifty, it is just a different way to ride. So moving
the front wing in the forward position will make the ski
feel a bit touchier versus the front wing being in the
rear position. You may find yourself needing to use
foot pressure more in order to control the actions of
the ski. Having the front wing in the forward position
(moving center of mass forward) the also makes skidders
easier since you don’t need to slide your butt off the
seat as much or push out with your feet as much.
So with the front wing in the
forward position, you’ll generally feel quicker and
steeper take-offs (more pop) with less effort. The
downfall is that the steeper take-offs might be a bit
tougher to keep consistent (too quick-variations in
steepness), and you may need to fight the foil from
popping back up on the not-so-perfect landings.
With the front wing in the back
position (after you’ve re-shimmed the rear wing for
proper lift), you’ll generally feel like you have to do
a bit more work to get the foil go as steep as compared
to the front position. The upside is that you may feel
a bit more in control because you are doing more of the
work versus the foil doing it for you. This could lead
to more consistency on the take-offs, as well as the
landings. In general, you will control the foil more
with your upper body movements versus foot pressure,
since you are sitting closer toward the center of
gravity.
Now, the different front wings have
different amounts of material sticking out in front of
the fuselage. Here are some examples of wing positions
on the LE38 (measured from the tip of the fuselage to
the front wing.
1 ¼ inches - Straight Trailing Edge
Wing (Back Position)
2 inches - Straight Trailing Edge Wing (Front
Position)
2 inches - Mini-Batwing (Back Position)
2 ¾ inches - Mini-Batwing (Front Position)
So realize all of the different
variables that are changing when you move the front wing
forward/back and remove trailing edge material
(straight, mini-bat, batwing)…lift, responsiveness,
center of gravity, take-off steepness, take-off effort.
Too much of any of these variables will cause
instability, which causes more crashes, which causes
less aggressiveness and confidence in your riding.
Properly test all of the different placements until you
find the right balance for your riding style!
Quick Summary of Options:
Remove Trailing Edge = Added
quickness, looser feel left/right or side-side
Front Wing Forward Position
= Center of gravity moved forward, less effort to go
steeper on take-off, more lift
Front Wing Back Position
= More stable center of gravity, more effort from the
rider to go steeper on take-off, less lift
Rear Wing Forward Position =
More quickness (small lift amount may occur)
Rear Wing Back Position =
Less quickness (small lift amount may occur)
Positive Lift Shimming =
Pointing the leading edge of the rear wing down moves
the leading edge of the front wing up for more lift
Negative Lift Shimming =
Pointing the leading edge of the rear wing up moves the
leading edge of the front wing down for less left
Final note about shimming…
The great thing about shimming is
that it is a really easy way dial in the lift of a foil
when you are making wing changes or the water conditions
change. The downfall of shimming is that you have to
mess around removing the rear wing when you could be
riding! Another downfall is that it does increase
drag. Granted, the drag that you create by shimming is
pretty minimal, but you REALLY notice drag if you
greatly change the angle of the rear wing. You will
most likely never run into a shim induced, major drag
problem, unless you are designing experimental foils,
but the fact is still there. If you get your setup
dialed in and you would rather not have a shim in the
rear wing, tuning the leading edge of front wing can
increase or decrease lift by a small amount. It could
be just enough that will eliminate the need for a shim
in the water conditions that you mostly ride in. For
more information on tuning, please refer to this tuning
guide.
http://www.teamhydrofoil.com/tune_info.htm |
