I think the thing that helped me to visualize this is the understanding
that the effect only occurs during the transition to the rising air.
After that, everything goes back to normal.
This has been a *GREAT* thread. It has been a real eye-opener for me.
I think back to flying and seeing the plane do this and have a much,
much understanding about what is happening.
Thanks to all who took the time to explain this.
-Ben
[EMAIL PROTECTED] wrote:
>
> I'm not sure which answer is correct here. I'm not sure if you can use the
> "same airmass" theory because in fact the plane is moving from one air mass
> to another (the thermal). OTOH, I'm not sure I'm comfortable with the
> weathervane theory, because after all, a weathervane is anchored wheras the
> plane is not.
>
> At 12:12 PM 3/12/00 -0500, Ben Diss wrote:
> >Not really. It doesn't make sense to me. Since the wing and stab are
> >both in the same airmass, the effective AOA changes together and then
> >stabilizes together. There isn't any more wind striking the stab then
> >there is striking the wing.
> >
> >Maybe I missed something?
> >
> >-Ben
> >
> >Jill and Rick Brown wrote:
> >>
> >> You have got to be joking!
> >> How does a weather vane work? It wants to point into the wind. The tail
> >> of a sailplane is essentially a weather vane. The sailplane is pivoting
> >> about the CG and the tailboom and stab form a moment arm. It doesn't
> >> take much force on the tail to rotate it. If you need proof just balance
> >> the plane on it's GC and add a 1/2 oz of lead to the tail. Tail Down!
> >> The lift component is an upward force on this system and wants to
> >> rotate the tail upward to some degree as it also starts to lift the
> >> whole plane. Because it takes very little force to rotate the tail up
> >> or down this force gives a tail up/nose down attitude to the plane.
> >>
> >> Does this seem to make any sence to anyone?
> >>
> >> RB
> >>
> >> Rodger Hamer wrote:
> >> >
> >> > That is an answer that makes sense!
> >> > Rodger
> >> > ----- Original Message -----
> >> > From: "Moved by the wind." <[EMAIL PROTECTED]>
> >> > To: "Rodger Hamer" <[EMAIL PROTECTED]>
> >> > Cc: <[EMAIL PROTECTED]>
> >> > Sent: Sunday, March 12, 2000 9:52 AM
> >> > Subject: Re: [RCSE] On Step
> >> >
> >> > >
> >> > >
> >> > > Rodger Hamer wrote:
> >> > >
> >> > > > Can somebody explain to me why when in good lift the tail
> rises and
> >> > the
> >> > > > plane appears "on step"
> >> > >
> >> > > Seems like there's a lot of opinions on this. IMHO the opinions
> above are
> >> > wrong, so I'll add mine.
> >> > >
> >> > > The story starts with your plane is flying along level in still air
> at an
> >> > AOA of say 3*, and the fuse level, (unless it's an Hobie
> >> > > Hawk). Now you have wisely steered the plane to lift, how does the
> plane
> >> > "see" this? With the upward component of lift the wing is
> >> > > now flying into the air at an AOA of say 5*, but the plane is
> trimmed to
> >> > enter the air at 3*, so what happens now? The plane will
> >> > > assume an AOA of 3* to the air, but that looks like it's -2* on the
> fuse
> >> > compared to ground. You're on the ground, so it looks like
> >> > > the nose went down or the tail went up to you.
> >> > >
> >> > > Did I get it right?
> >> > >
> >> > > Rich B
> >> > >
> >> > >
> >> >
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> >
> ____________________________________________________________________________
> Brett Jaffee: [EMAIL PROTECTED]
>
> Brett's Slope and Power Home Page: http://home.earthlink.net/~jaffee
> OnTheWay Quake 2 server utility: http://www.planetquake.com/ontheway
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