Ed,
Hmmmmmm...., the Sunfish sail is rigged on the port side of the mast -
always. What slight differences there are between port tack and starboard
tack are then equal between boats.
There's lots of sail adjustments to tuning the rig as you will discover when
you get your copy of the Sunfish Bible.
I think the actual difference in speed is minor, but I'd have to (A) be
absolutely sure wind and water conditions were the same for tests on both
tacks and (B) need a GPS to tell the true speed of each.
Wayne
toggle quoted message
Show quoted text
-----Original Message-----
From: Ed Conley [mailto:conley49@...]
Sent: Wednesday, March 26, 2003 8:37 AM
To: sunfish_sailor@...
Subject: RE: [sunfish_sailor] Running Flat?
Thanks Howard and Wayne for your explanations and reference material.
I had observed that my "Fish-clone" was much slower when in a
tack or reach
course where the gooseneck orientation allows the sail to lie against the
mast thus changing the sail shape. In one lake in particular I could half
my time spent (seems like it anyway) tacking to the larger part
of the lake
just by planning ahead of time which side of the boat the
gooseneck would be
facing.
One of the first observations about my "Fish-clone" shortly after purchase
was that the daggerboard has been repeatedly damaged and
refinished to sand
out smashed spots and, as repair allowed, the leading edge of the
daggerboard was finished to a sharp edge or point along the plane of the
board. With the daggerboard involved so much in the potential lift of the
system its shape must be very important. Wouldn't a rounded blunt leading
edge allow for better off axis flow without producing turbulent
drag? Again
with no local real or racing "Fish" to view I am operating in the blind.
Dose anyone have a plan with dimensions on it for a good
daggerboard design?
I am planning a trek to the Vanguard dealer in Oakland sometime in the
future but would like any words of wisdom form other "Fish" owners.
Thanks again!
Ed
-----Original Message-----
From: Howard Bishop [mailto:bishop2398@...]
Sent: Tuesday, March 25, 2003 6:27 PM
To: sunfish_sailor@...
Subject: RE: [sunfish_sailor] Running Flat?
Don't know if this helps or not, but if all else
fails, think of the last time you flew a kite.
Remember how much harder it pulled on the string when
it was nearly overhead compared to when you first
launched it (straight downwind)? It's something like
that.
A slightly more technical attempt at an explanation
follows.
The thing that makes sailing anything other than
straight downwind is the dramatic shear, both in terms
of velocity and viscousity, of the two fluids involved
(air and water).
There are a couple of other useful things to
remember:
1) in other than a dead run, the centerboard produces
useful lift orthoganal to the direction of the boat's
travel (lift in other directions may be produced, but
it is un-useful and should be counted as drag).
2) the dynamics of a sail while reaching or pointing
are incredibly different than that of one running. It
is the difference between a gyrocopter and a
helicopter, or between a parachute and a hang glider.
with those thoughts in mind, we go on:
When running straight downwind, the theoretical
maximum speed is equal to wind speed. period.
When bearing off slightly, we could, in theory, retain
the downwind vector, but add the new, slightly
off-wind vector. Depending on the amount of wind, the
efficiency of the sail, and the amount of lift
generated by the daggerboard, there is some
theoretically optimal angle at which to sail. Bear in
mind, that as one speeds up on a beat or reach one
introduces yet a third vector which may in fact
*increase* the amount of lift the sail produces. At
some point the lift vectors generated by the sail and
board (note: these vectors will differ in both
magnitude and direction- the difference their lateral
components is your leeway) will achieve some stasis
with the drag vectors of the system (both hydro and
aero dynamic)and the theoretical max speed is
acheived.
Howard
__________________________________________________
Do you Yahoo!?
Yahoo! Platinum - Watch CBS' NCAA March Madness, live on your desktop!
Yahoo! Groups Sponsor
ADVERTISEMENT
If you do not wish to belong to Sunfish_sailor,
you may unsubscribe by sending an email to:
sunfish_sailor-unsubscribe@...
Please do not send unsubscribe requests directly to the group.
USEFUL ADDRESSES
Post message: sunfish_sailor@...
Subscribe: sunfish_sailor-subscribe@...
Unsubscribe: sunfish_sailor-unsubscribe@...
URL to egroups page:
Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.
If you do not wish to belong to Sunfish_sailor,
you may unsubscribe by sending an email to:
sunfish_sailor-unsubscribe@...
Please do not send unsubscribe requests directly to the group.
USEFUL ADDRESSES
Post message: sunfish_sailor@...
Subscribe: sunfish_sailor-subscribe@...
Unsubscribe: sunfish_sailor-unsubscribe@...
URL to egroups page:
Your use of Yahoo! Groups is subject to
