[Rhodes22-list] Re: Pointing

[Steve Alm]

P.S.  Unless you're on Fretless, then there's a whole new set of variables.
8-)

Slim

On 9/23/04 2:26 AM, "Steve Alm" <salm at mn.rr.com> wrote:

> 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
> 
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