Are
there any recent breakthroughs in Aso spinnakers?
LL:
Asymmetrical
development continues as the perfect sail shape for each design/boat
type and angle is determined. Unlike symmetrical spinnakers, there
is a perfect shape for every wind velocity and angle. One aspect critical
to optimal performance is sheet lead position. Like trimming a genoa
or Jib Top, it is critical that the lead be changed as the TWA fluctuates.
The leading angle of the asymmetrical must break evenly top to bottom
just as if you were trimming a Jib. Because there is only one perfect
shape for each angle, the goal is to produce a sail with a wide range.
Much of this work must be done in testing on the water, but here at
Quantum we are producing great results inside the wind tunnel.
Once
only popular on skiffs and sportboats, ASO kites are now becoming
the accepted norm on all types of performance boats. What is the reasoning
behind the new acceptance?
LL:
Originally,
like anything new, a change toward asymmetricals was met with resistance.
As new boats like the Melges 24 and J120 came to market, asymmetricals
became standard equipment, leading the way toward a new generation
of boats and the method in which they would be sailed. Now having
sailed with asymmetricals, most people find the actual jibe maneuver
more safe and controlled. At the same time, making higher performance
possible. As our experience progresses and the rules become more lenient,
we now have a situation where the original symmetrical spinnaker may
disappear forever. Banished to the world of short battens, mainsail
foot ropes, and crosscut sails.
Recent
testing seems to indicate that current ASO Spinnakers are actually
more efficient than SYM kites over a wider range of windspeeds and
angles. How much has the evolution of the shapes contributed to this?
LL:
Due
to the nature of their design, symmetrical spinnakers are less affected
by sheet lead position. We have now learned to develop asymmetricals
with wider wind ranges by modifying the shape to have a straighter
more open/twisted leech. This provides a fast shape for heavy air
and then can be modified for light air by moving the sheet lead forward
and down.
You've
mentioned that you are using a wind tunnel for testing. To our knowledge,
nobody else is doing that. What can you gain by this method of testing?
LL:
Currently,
Quantum is the only sailmaking company testing sails in a wind tunnel
in the United States. Our relationship with the Glenn L. Wind Tunnel
at the University of Maryland began 3 years ago. To date we have provided
data to US Sailing, to the IMS Committee, and of course to our customers.
The advantage of the tunnel is in providing quick accurate data for
a multitude of designs in a very short period of time. It also allows
us to limit the number of variables, which can influence our results.
Currently our studies have been focused on providing target crossovers
for an inventory of asymmetricals for new designs. We also completed
a study prior to the last Bermuda Race to help a customer determine
the optimum spinnaker inventory, considering both asymmetric and symmetric
spinnakers, to win the race. This type of information would take months
of testing at full scale and obviously would require a very large
budget for the production of the test sails.
How
much oversize for the pole is the minimum required to get an ASO working
properly? We assume there is a difference if the sail is flown from
a centerline prod or from a conventional pole.
LL:
There
is no minimum. Asymmetricals can be flown from "SPL" even if it equals
"J" either from a pole or on centerline from a padeye. The tack position
is critical though, and will determine the size of the sail and its
designed foot length and overlap with the mainsail. There is another
aerodynamic factor that greatly affects performance and the location
of the tack. Without consideration for the rules, the tack should
be moved forward until the helm goes neutral or is slightly negative.
By reducing rudder angle, a constant problem while reaching, overall
boat speed is greatly increased.
Do
you build ASO kites any differently for boats with prods vs. boats
with standard poles?
LL:
Asymmetricals
developed for adjustable spinnaker poles are very different than sails
developed for non-adjustable prods or sprits. The most significant
difference is in the geometry or edge lengths of the sail. Because
sails set from a prod cannot be squared, the foot length must be designed
shorter to prevent the sail from becoming too deep as the sheet is
eased for more downwind angles. Basic shape differences are more subtle.
The sail designed for the prod must be more "All Purpose" in design
as the sail is restricted to less adjustment.
If
a customer comes to you with a club racer like a Catalina 27 or an
old Half-Tonner and asks about switching to an ASO setup, what do
you tell them?
LL:
First
there are rating rules to consider, and unfortunately the consequences
of these rules usually decide this question. Rules and rule-makers
typically react slow to new inventions in sailing and most of the
time, move slowly and cautiously, in an effort to maintain the status
quo. Sometimes, this approach can be good, but many times it is bad,
as new developments that add to the experience of sailing get stifled.
For 2 years, I have encouraged rule makers to modify how spinnakers
are measured to incorporate an area calculation, much like the Volvo
or America's Cup events. This would make the change to asymmetricals
much easier to handicap as both current symmetrical spinnakers and
new asymmetrical spinnakers would be exactly the same area. This would
allow development without punitive rating consequences.
I
might argue that North has the best ASO's in the business because
of their America's Cup accomplishments. Tell us why a customer should
consider your product.
LL:
Quantum
has a very strong background in spinnaker development that is rooted
in our beginnings with Sobstad. From this background grew our development
into asymmetrical spinnakers in 1990 (?) when we supplied the winning
designs for both classes of the Whitbread Around the World Race. Since
that time we supplied the winning America's Cup spinnakers for Bill
Koch in 1992, for his girl's team in 1996, and for Swedish Match and
Brunnel Synergy in the last Volvo event. Quantum is also, the only
sailmaker performing wind tunnel testing on asymmetrical and symmetrical
spinnaker designs in the United States. Our relationship with the
University of Maryland and the Glenn L. Wind Tunnel has provided important
research data that allows us to compete with North at this level.
Much
like mainsails and genoas, there has been significant sailcloth development
for spinnakers. Share with us what some of those are, and their applications
for ASO's.
LL:
Realistically,
affordable asymmetric spinnaker fabric has been slow to develop. Early
fabrics were produced by combining traditional nylon and polyester
substrates with lightweight, .25mil polyester Mylar. While proving
durable and capable of surviving the Whitbread, these fabrics were
just the first step in development. In the buildup to the 1992 America's
Cup, Bill Koch and a team of scientists created what is now know as
Cuben Fiber. This fabric was created by laminating multiple layers
of very small denier Spectra to Polyester Mylar through the use of
an autoclave. The result was a fabric that had unprecedented strength-to-weight
ratio. To this day, it is still the fabric of choice for top-level
programs, but is very costly for the majority of the market. For this
reason, some efficiency of weight has been sacrificed in an attempt
to lower the cost of acceptable fabrics.
Much
has been made of Code Zero's. Are they viable for a PHRF application?
LL:
Code
0's are applicable for any boat, but again rating must be a consideration.
Unlike a mainsail, a Code O will only be used in TWS 6-16 knots and
TWA of 80-130 degrees. This makes it difficult to pay an additional
6 seconds per mile, for every mile sailed, regardless of angle. For
boats with non-overlapping jibs, like the J-105, J-120, Ect, the addition
of a Code 0 for point to point races, becomes more practical as these
boats suffer when forced to reach against boats with overlapping jibs.
Realistically,
for say, a J-105, how many ASO's does somebody need to go PHRF racing?
LL:
In
order of priority, a J-105 sailor would need a class type All-Purpose
Asymmetrical and a Code 0. As described above, the Code 0 becomes
a deadly weapon and is critical when reaching against boats with large
overlapping Genoas. Then, budget allowing, this basic inventory could
be supplemented with a Code 3/5 type Reaching Asymmetrical. The mid-girth
on this type sail would be approximately 90-95%.
There
is a theory that smaller ASO's are faster than their larger counterparts
in light air. If so, why?
LL:
Like
spinnakers, small asymmetrical spinnakers are faster in light air
because optimum target angles are very high, approximately TWA -90
degrees and AWA of 60 degrees. Because of these tight sheeting angles,
a reduction in overlap is optimum to allow proper flow and attachment
over the main.
If PHRF said that they would hit my Ranger 33 six seconds per mile
to carry an ASO along with my standard kite would you say that it
is worth it?
LL:
Boats
of this type would find it difficult to pay for the additional rating.
The PHRF rule is the most inequitable as it applies rating to sails
when they may not even be flying.
Can
you give us a couple of quick tips on flying the ASO when trying to
run deep?
LL:
On
boats with sprits or prods the luff tension controlled by the tack
control line becomes critical. If designed properly, the tack line
would be all the way down when reaching and eased as then TWA increases
allowing the luff to rotate out and to weather of centerline, maximizing
the sail's projection. For boats with adjustable poles, pole height
becomes critical much like a normal spinnaker, but for a different
reason. The pole height will be lower in general, as the luff length
is longer and is chosen based on how the sail is breaking or luffing
when the sheet is eased. The luff should break evenly top to bottom
with the top 25% luffing just ahead of the lower 25%. If the bottom
portion luffs first the pole should be lowered until the reverse condition
occurs, when the pole would be raised. Keep in mind the pole will
be adjusted higher as the TWA increases. Sheet lead position is more
critical for asymmetrical spinnakers. These types of sails are more
like Genoas and therefore have only one perfect lead position for
each TWA. Additional padeyes should be located forward of the normal
spinnaker sheet block so a 2:1 tweeker or down-puller can be used
for easy lead adjustment. It is also important to remember to ease
the down-puller creating more twist when the boat becomes over powered.
Another little know trick is to move the lead forward in extremely
light air and tight reaching angles. This will create camber in the
foot of the sail allowing the sheet to be eased. This trick also works
for symmetrical spinnakers.
What
is your preferred method of retrieving an ASO?
LL:
The
most controlled method for retrieving an Asymmetrical Spinnaker is
by using the lazy or unloaded sheet. This type of take-down has become
possible with the introduction of loose footed mainsails. Take a portion
of the unloaded sheet and pass it from the leeward side, between the
boom and the bottom of the mainsail, to weather side securing it.
Then to take the sail down, the tack shackle is fired away, turning
the sail inside out making it easy to pull in between the envelope
formed by the top of the boom and the bottom of the loose footed mainsail.
Thanks Larry
