How Fast (Relative to Wind) do windsurfers go?
Jim Titus
Sorry if this has been discussed and I missed it, but I have often
wondered how fast I am really going when sailing in a 12-20kt wind.
My guestimate has been, of course, to assume that (1) my sail has the
ability to only go 45 degrees off the apparent wind and that (2) there
is no friction. This leads to the conclusion that I am going 1.41 times
the wind speed when I am on a 45% broad reach, and that I am sailing at
the wind speed when on a beam reach.
But I have no sense of either (3) how much the invalidity of these two
assumptions slows me down (or speeds me up), or (4) how big of a sail I
have to have to get to whatever the theoretical potential may be.
Can anyone elaborate on these matters. Any idea what the speed record
is for sailing in a 15 or 20kt wind?
Thanks
Jim
Murray Hunter
WHO CARES!
Just get on a fast plane and start sailing on Maui:
http://www.maui.net/~ranch2k1/index.html
Aloha
William Braden
A sailboard is nowhere near no-friction. The assumption of no friction
is most nearly realized in an iceboat, where the limiting factor is the
drag of the sail itself. An iceboat can go 4-5 times the speed of the
wind anywhere from 45 deg upwind to 45 deg downwind (roughly).
I think the ratio for a multihull is about one. I haven't seen
calculations for sailboards but in real life I've seen reports of 1.5
(e g 30 kts in a 20 kt breeze).
Bill Braden
John Bryja
Jim Titus <jtitussss...@erols.com> writes: > Sorry if this has been discussed and I missed it, but I have often
> wondered how fast I am really going when sailing in a 12-20kt wind.
Hello Jim,
From our radar testing in Cape Hatteras during our annual testing
and clinics we have found in lighter winds windsurfers can go
about two times the speed of the wind. As the wind increases
the speed relative to the wind decreases. In 15-20 knots of
wind recreational sailors will go any where from 20-38 knots
when planing. In 40 knots of wind most sailors will reach
25-40 knots. Experts and pro level sailors can go a little
faster but there seems to be a barrier to the speed people
reach relative to the wind as it increases.
Best Regards,
John Bryja
Managing Editor
Windsport Magazine
John Crumpley
The Swami from Shell Point Sailboard Club coined a phrase, "Who feels
it, knows it. It has always been thus."
Believe me. You'll have no doubt, and will NEVER forget the first time.
John Crumpley
JAWS
Jacksonville, Fl
Dale Appleton
On Fri, 12 Jun 1998 15:11:54 +1000, John Bryja wrote
(in message <6lqdaq$7b4$1...@news10.ispnews.com>):
A clumsy explanation is the best I can do:
On the subject of apparent wind:
You will notice that on a sailboard that is planning (assuminmg a straight
course), the clew of the sail lies either just on the centre line of the board
or a little to leward. This is the case from sailing hard up wind, to below a
beam reach. In other words the trim angle of the sail to the wind remains the
same. This due to the apparent wind that sweeps the deck of the board. The
further off a beat to windward you sail, the faster your hull speed is, and the
more that speed increase results in an angle change downwind to the apparent
wind. Like many other high perforamance yachts our sails spend most of the time
at shallow angles of attack.
(Have a look at any displacement yachts near you when you next blast past one
and compare boom angles.)
On the subject of windspeed vs hull speed ratios:
I just had a quick look through "Areo-Hydrodynamics of Sailing" C.A. Marchaj
specifically looking at Boat speed/Wind Speed (Vs/Vt) ratios of various sailing
craft. In 1977 Crossbow, an offsett catarmaran achieved 31.8 knots in
windspeeds of under 20kn. More recently the World Speed sailing record was
broken by a what could be classed as a trimaran. She recorded burst speeds of
over 50kn in wind speeds of around 20kn.
Marchaj equates the Vs/Vt to lift drag ratios of modern gliders and ice yachts.
He also has a number of polar diagrams that plot the given Vs/Vt ratio against
the course relative to true wind direction. (At ratios of 2:1 we are very
inefficient compared to iceyachts at 5:1 or high performance gliders at 50:1)
In most classes of sailing craft a course of arond 110 degrees from the true
wind direction is the where the Vs/Vt ratios are highest.
Similarly "High Performance Sailing" F Bethwaite, there are excellent
comparrisions with ice yachts and gliders, and high performance craft.
Some years ago I participated in a 500 metre speed sailing event, and managed
to record the days highest production board speed of 26kn in wind speeds of
under 20kn. The course was laid at 90 degrees to the wind, so by sailing the
course at approx 110 degrees to the wind I picked up a few extra knots over my
fellow competitors, I also came close to breaking the World Record for the
fastest deacceleration of a sailboard, by running into a sandbar at the end of
the course!
Hope that helps and not confuses!
Dale
b...@spam_sync.com
On June 11 1998, Jim Titus <jtitussss...@erols.com> wrote:
> Can anyone elaborate on these matters. Any idea what the speed record
> is for sailing in a 15 or 20kt wind?
Jim,
Too many factors to consider. However, I recall a report on the Bic 263
Vivace which the testers radar gunned it at 38Mph in 18mph wind.
The only inexpensive way to know what your average speed is would be to
sail between two points of known distance from each other and time the
ride.
Ben
--
Ben Kaufman
antispam: To Email me, change domain from spam_sync to pobox.
- 06/14/98
TomBuckOb2
Jim:
1.4 times windspeed is definitely do-able. I think Roger had some reports of
closer to 2x windspeed at the high end of your 12 to 20 mph range.
Tom O'Brien - Chicago
Charlie Escher
TomBuckOb2 wrote:
Back around '91 or so, Ken Winner used to factor efficiency into the rankings at
the Jantzen Speed Series. He had anemometers on the start and finish buoys (this
was when he had the radio transponder system), and averaged the readings for the
windspeed on course readings. I competed in one particular event, at Floras Lake
in southern Oregon, which was on a 50 meter course. 2.2 X windspeed was pretty
common, as I recall (I even did this, on an E-Rock); I think 2.4 or even 2.6 X
won that event. I believe that the numbers dropped sharply as windspeeds
increased much above 15 mph, I know that they did for me. Note that this
methodology is far from foolproof, as windspeed before the start buoy is unknown.
In fact my strategy for the event was to catch a good puff outside the course,
then to glide through the 50 meters as (hopefully) the wind on course totally
fizzed out. I managed something around 25 mph in 11mph average wind using this
strategy (E-Rock, Freedom 6.1 sail), but in any case, anything less than 2 X
windspeed was not competitive at this particular event. I'd love to see what more
modern equipment could do, both from the sailing and the testing side of things.
I posted this same question a couple of months ago, expecting to see numbers at
3 X or better, but nobody posted any higher numbers than what I saw back in '91,
hmmm...
--Charlie Escher // Bingen, Wa.
TomBuckOb2
>I posted this same question a couple of months ago, expecting to see numbers
>at
>3 X or better, but nobody posted any higher numbers than what I saw back in
>'91,
>hmmm...
>
> --Charlie Escher // Bingen, Wa.
The more things change . . .