From: rogerc@ssd.intel.com (Roger Christal)
Subject: Bruce Peterson Interview
Organization: Supercomputer Systems Division, Intel Corp.
Distribution: rec
Date: Thu, 8 Oct 1992 21:24:23 GMT


Following are portions of an interview with Sailworks designer Bruce
Peterson.  This interview was published in Performance Windsurf
Report, Volume 2, Issue 3, 1992.

The portions reprinted here are done so with permission of Performance
Windsurf Report, published by MBA, P. O. Box 336, Hood River, OR,
97031, +1-503-386-3522, FAX +1-503-386-3541.  Look for their next
issue on February 15, 1993 with test results of 1992 sails, 1993
production boards and light air boards.  If your local windsurf shop
doesn't carry Performance Windsurf Report, ask them to write or call
for more information.

Many portions of the interview relate directly to the "Optimal Sail
Quivers" thread that has been under discussion lately.  I hope you
will find the information here as interesting as I did.  All questions
and responses are in interview order.  Some questions in between were
dropped because they do not relate to the discussion.

----------------------------------------------------------------
PWR = Performance Windsurf Report
BP  = Bruce Peterson

PWR:  What are you consumer targets?  Obviously your three lines are
the Revolutions, Cam 1, and your Race sails.  What are your different
targets?

BP:  Even though most of the people who buy our sails are not racers
and don't have any desire to race, they want to sail something that's
real fast, real easy to sail and something that they perceive to be
the most performance oriented sail on the market.  That's what I find
interesting.  Very few of the people who buy our sails race, but they
do enjoy going fast.  They go for the stability derived from all the
development and racing on our Race sails.  Funny, because there's
sort of a small misconception about race sails, in general.  Many
folks think they are hard to use and that you have to be a racer to
use them.  I think that couldn't be further from the truth, because
what a racer wants is something that's powerful, efficient, stable and
easy to handle.  It's also got to be easy to use because if you're
fighting it you're not going to go fast.  Those performance points are
the same things your average recreational sailor wants.  That's where
our Race sail has been really successful.  You don't have to be a
racer to use it.  Anybody who can waterstart and make a third of their
jibes can appreciate the performance in it.  When we made the Race
sail, our target was for intermediate to advanced sailors, but we now
also have professional racers calling us wanting to buy our production
sails.  It's unusual, being pursued in that manner.

[...]

PWR:  I've seen pictures of you and Phil [McGain] from the session
when Michael Hildreth was shooting you two, and I was looking at the
photos and the sails looked really torqued out.

BP:  We were totally overpowered that day.  We were hanging onto a 5.1
and a 5.6 in 35 to 40 knots.

PWR:  They were just doing all sorts of things.  I see this sail
sitting right here (I'm pointing to a 4.6 Race, that's rigged on his
lawn) and it has a different look to it.  Loose leech, virtually no
outhaul.

BP:  Looks flat

PWR:  Looks really flat.

BP:  You take that sail, that's a 4.6, that's meant for 20 to 40 knots
of wind.  That's the sail that I'll be running in Birds of Prey
(forthcoming article in our next issue.)  That's a top end sail.  It's
not a sail that you've got to struggle to get up on a plane on, and
it's still got a really good low end.  You hang on, a puff hits and
you just keep accelerating.  You don't get all bent and torqued out of
shape.  Statically it is loose and statically it is really lean.  But
when you get powered up and put some wind to it, the mast starts to
bend and the sail starts to load up and twist.  It pulls tight along
the perimeter and the shape fills out on the bottom of the sail.  How
it looks right there and how it looks under 30 knots of wind are
totally different shapes.  Most people don't realize that.  There were
a number of sail designers who make the sail design look real pretty
on the beach, but when they get a lot of wind in them they get totally
distored.  A shape that is really easy to handle when you're
overpowered is not necessarily the prettiest thing to look at.  You've
got to get the sail opening and twisting in the top and you've got to
keep your center of effort low and forward.  If that doesn't happen,
you can't hang onto the thing.  You get a huge backhand pressure and
you get lifted out of the water.

PWR:  It sounds like the real focus of Sailworks is to have a sail
that can carry a tremendous load range.

BP:  Right, but not at the expense of having to sacrifice your
acceleration.

PWR:  What's more important, control or acceleration?

BP:  What sail size?  Because it's an in-line change, it depends upon
your sail size.  If you're on a 7.5, for example, because it's the
biggest sail that you can use in a IYRU Race board class it is a sail
that is gonna have low end.  By and large, they race in less than 12
knots in that class.  So that sail has got to be all grunt - it's got
to be all acceleration to pull your board onto a plane as quick as you
can.  And if you can't plane, you have got to have a high lift, or a
high center of effort in the sail.  So you have a lot of pressure in
that sail so that you can plow along at speed even if you can't get
onto a plane.  It doesn't have so much pre-twist.  It's much fuller up
through the head, the perimeter is really tight so you can pump
better, the foil is really deep, the draft is back at 45 percent.  The
entry is really lean so that you don't have to force the air flow
around a really blunt entry.  It's all designed for acceleration to
get going.  And as you start to come down through the sail range, say
like a 6.5 or a 6.1, which are primarily course racing, or course
slalom sails, then you start getting into a little more induced static
twist so the sails are looser on the leech and starting to come open.
They are still pretty lean on the entry, but the entry is starting to
come forward a little bit, to be a little bit more efficient.  As the
sail loads up you are going to want to be able to carry the sail in
heavier winds.  Sometimes on 6.1's you are getting into 30 knots, in a
course race and you just have to hang on.  As you go down the range
further, like a 5.1 or a 4.6 and down, they are reaching sails.  You
don't course slalom race on a 4.6.  So all of our small sails in our
race sail line are biased toward reaching and having a controllable
top end, where you have this sort of open ended acceleration.  The
wind starts hitting it and the sail just starts twisting, twisting,
twisting and the center of effort comes down and goes forward.  You
can control the sail even if you can't sheet in.  It's controllable
because you're not getting a big back hand pressure as your center of
effort moves back, and the tip isn't really tight so your center of
effort doesn't stay high.  That's the in-line change I'm referring to. 

[...]

PWR:  You said your Race Sail works for everyone?

BP:  I think so.  If you know how to jibe and make a waterstart, you
can use our race sails.  If you don't like having the brute force, the
power and acceleration of a race sail, we have a Cam 1, which is more
of a recreational oriented sail.  In the big sizes, it's more like a
slalom sail, and in the small sizes, it's more like a wave sail.  And
then we make a sail that we call the Revolution, which is designed to
be a full on competition wave sail.  It's a more versatile wave sail
to use in a variety of locations.  But it's also a forgiving and easy
to use RAF.  People have this idea that if you have a really advanced
design in a sail, it's hard to use.  It couldn't be further from the
truth!  Our racers, like Phil [McGain], will nitpick forever on a
sail, because they want something that's easy to use.  If you have to
fight the sail, if it's something that's difficult for you to tune, or
difficult to trim, it's not fast.  The fastest sails are the ones that
just go, you sheet in and go.  The sail twists properly, you've got
the right draft in the sail, the tension moves through the sail so
that it loads up properly.  You don't have to do anything.  There's
not this constant fighting and trimming and constantly readjusting and
being lifted up, and pulled back and you sheet in and you get lifted
up and you got to sheet out, you get back again and you sheet in, you
know.  That's a poorly tuned or poorly designed sail.  The sails that
go the fastest, you just sheet in and you just go.  And everything
happens automatically in the sail.  The wind hits the sail, it twists
open, the center of effort comes down and moves forward, you don't
have to sheet out, you can just hold it there.  If the wind backs off,
the leach closes up a little bit, and you get a little bit more power
going up to the top of the sail.  Keeps the board trimming nice.  If a
gust hits, the sail opens up, the board just lifts up like that, you
just hit the tops of the waves and go.  You don't get picked up, and
you don't get moved back.  It's easy, that's what it's all about.

-- 

>>=-  Roger Christal  rogerc@techbook.com  rogerc@ssd.intel.com  -=<<