for got to post the video
http://video.google.com/videoplay?docid=7416235999297705470








--- In wingboats@yahoogroups.com, "johhnysrocket2003"
<johhnysrocket2003@...> wrote:
>
>
> In the video at about 5.50 min. I tack and am in a lull. At 6.00 I put
> on 30 degrees of flap and the boat starts to accelerate more. It
> doesn't look like I sheeted out any. I noticed on some of the jibes
> it took a long time for the apparent wind to come around by watching
> the windex. I think the wind was pretty spotty and you had to be
> patient for the wing to hook back up.
>
> I think 30 degrees helps the wing not to stall during low lift
> situations as long as I'm moving at least 20 mph. 20 degrees is the
> fastest position but may suffer in lighter conditions.
>
> I am planning to make the ST 49 with adjustable gap on the flap. I
> imagine the sweet spots will change with each adjustment. My
> prediction is less gap will result in better low end for light air.
> Less gap equals better leeward flow at a higher flap angle like 30
> degrees. The flap deflected at 20 degrees may suffer from the leeflow
> not being as good.
>
> Normal or bigger gap will have a better top end at 20 degrees and not
> as good low end at 30 degrees because the gap gets too big.
>
>
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> --- In wingboats@yahoogroups.com, Tom Speer <me@> wrote:
> >
> >
> > On Dec 9, 2008, at 11:51 AM, johhnysrocket2003 wrote:
> >
> > > ...I have experimented with some tell tails. I have placed them
on the
> > > main trailing edge near the flap . They get sucked into the gap
on the
> > > weather side.
> >
> > They sound like they're too long. They should be short - say, two
> > inches - and it would be useful to have several in a row in the
> > chordwise direction. You won't be able to see the ones on the
leeward
> > side without a mirror or window in the wing, but the ones on the
> > windward side of the main would be the ones to tell you if the gap
was
> > too small.
> >
> > > The most helpful position I've placed them is about half
> > > way back on the flap . I let the tell tail extend about an inch
passed
> > > the trailing edge of flap. That way I can see if its flowing
right if
> > > its on the lee side.If I can't see it I know its not flowing right.
> >
> > Those sound a bit long as well, although we used a similar idea on
> > Lydia, anchoring the telltales a few inches forward of the trailing
> > edge and making them long enough to see their tips from the other
side.
> >
> > A sailmaker once told me about a troublesome client he had. The
> > client couldn't get the telltales to fly evenly up and down the
sail,
> > so he asked the sailmaker to recut the sail. After the
modifications,
> > the telltales still didn't fly smoothly, and he brought the sail
in to
> > be recut a second time. He still wasn't happy after the second
> > modification. The third time he brought the sail in, the sailmaker
> > put on telltales that were about a foot and a half long. The client
> > was satisfied when he next went sailing.
> >
> > >
> > > Most of the time I can get it flowing right if I readjust the flap
> > > angle for less angle. I have noticed in very light air that the tell
> > > tails may be flowing right at the tip but not right toward the
root or
> > > vice versa. If the boat is going about 15 or 20 mph everything flows
> > > right from top to bottom.
> >
> > This indicates the need for twist control. Twisting the wing was
the
> > secret to Cogito's success when it won the C-Class Challenge Trophy.
> >
> > > On Wingnutlll I usually have to set the flap
> > > to 20 degrees to get started. Once I get going I can set it at 30
> > > degrees to sail higher angles or deeper in light to medium air. In
> > > heavier air I leave it at 20 degrees or less.
> >
> > Interesting. Do you tend to sheet the wing out more after you
change
> > the flap to 30 degrees?
> >
> > Cheers,
> >
> > Tom Speer
> >
>