[Rhodes22-list] Re: Pointing

[Steve Alm]

Peter,

Hold on, thar!  "Lift" from the keel, CB and rudder?  The underwater
appendages are symmetrical with the hull and cannot provide any lift.  They
only serve to prevent lee way, or to provide lateral resistance.  That part
I agree with.  Brad might have a better description, but lift happens when
air (or presumably water) has to travel farther around one side than the
other, creating a difference in pressure between the two sides.  Lift is
created by the curved shape of the sail or airplane wing and will stall if
not going fast enough.  The keel, CB and rudder do not have that kind of
shape.  I'm with you on the rest as far as pinching vs. pointing goes, but
it's the sails that stall out, not the keel, CB or rudder.

Slim

On 9/22/04 7:58 PM, "Peter Thorn" <pthorn at nc.rr.com> wrote:

> Hello Ed,
> 
> If you verify that you're able to point your R22 35 degrees off the true
> wind, I certainly would like to visit Lake Hartwell to see that.   Perhaps
> it's the apparent wind, the combination of the boat's velocity across the
> bottom combined with the true wind direction, that's making you think you're
> pointing so close. On a reasonably fast boat like R22, the apparent wind
> angle can move quite a bit forward.  In an extreme example such as iceboats
> (that travel many times the true windspeed) the wind indicator points almost
> straight forward.
> 
> Are your headsail sheets led to tracks at the foot of the cabinhouse roof?
> That, I think, would certainly improve pointing.
> 
> It's good to be aware of the difference between pointing and pinching.
> Sailing too close to the wind can cause the underwater foils to slow down
> then stall.  That's pinching.  When the keel, cb and rudder stop producing
> lift, the boat will start to produce a lot of leeway, or sideways drift.  It
> is very difficult to detect leeway when aboard the boat that's making all
> the leeway.  The bow points higher, so the skipper might think he's pointing
> pretty high because the sideslip is so hard to feel.  To avoid this
> condition, foot off and keep the boat moving.  After regaining speed, head
> up a little.
> 
> If you have a GPS you can verify your pointing angle by measuring your
> heading (not the direction the bow is pointing), tack to the other tack,
> measure heading again and divide the angle difference by 2.  I think someone
> mentioned this not too long ago on the list.
> 
> I too have wondered about the diamond board, and would guess Phil Rhodes
> original cb is pretty hard to improve on.   A while back Roger wrote a very
> scientific sounding comparison, do you recall that?
> 
> Perhaps you Lake Hartwell guys should conduct on-the-water pointing trials
> and settle the issue.
> 
> PT