Brett, I follow what you are saying except one part. You said "No, whatever
surface is facing "up" is going to have less pressure then the lower surface
if the plane is going to maintian
altitude." How does the plane know which way is up? It doesn't.
thanks for your input!
>From: Brett Jaffee <[EMAIL PROTECTED]>
>Reply-To: [EMAIL PROTECTED]
>To: Dana Falconer <[EMAIL PROTECTED]>
>CC: [EMAIL PROTECTED]
>Subject: Re: [RCSE] aerodynamic question
>Date: Tue, 31 Oct 2000 19:28:30 -0800
>
>Dana Falconer wrote:
>
> > I have always wondered this and I bet all of you out there know the
>answer.
> > Okay here goes...
> >
> > Considering a symmetrical airfoil:
> > Is a symmetrical airfoil used primarily for aerobatics/inverted flight?
>
>Almost exclusivly. That and surfaces that generally maintain zero-lift at
>zero-angle, such as horizontal tail surfaces.
>
> > So if the top of the wing creates less pressure due to the bernoulli
>effect
> > then when inverted the less pressure the top of the wing creates is
>working
> > against you right?
>
>No, whatever surface is facing "up" is going to have less pressure then the
>lower surface if the plane is going to maintian
>altitude. It is true that a symetrical or semi-symetrical wing isn't going
>to be as efficient when flying upside down, though. The
>pilot will have to compensate with a greater angle of attack to keep the
>plane from losing alititude, which will result in more
>drag.
>
> > I assume this is compensated by increasing the angle of attack and
>newton's
> > 3rd law then starts to play into maintaining altitude when inverted.
>
>Heh, this is a good way to start a Bernoulli vs Newton flame war :). Lets
>just say that both factors are always in effect, no
>matter how the plane is flying and no matter what the shape of the wing,
>and leave it at that for the moment.
>
> >
> > With a symmetrical wing the curve on top is almost the same as on the
> > bottom. Therefore the upward force the top of the wing creates is
>almost
> > the same as the downward force that the bottom of the wing creates
>(upward
> > being greater). The difference is the lift. So why have a symmetrical
> > wing?
>
>The only reason to have a symetrical wing is so a plane can fly upside down
>exactly the same as it does right side up (and do
>everything in between). If it weren't for aerobatic planes, I doubt you
>would see too many fully symetrical airfoils on main wings.
>
> > Why not have a wing with a flat bottom and a top that a little lift?
> > What I am getting at is, what does the symmetrical wing buy you
> > aerodynamically?
>
>Again, depends on what you want to do. A mildly aerobatic plane will
>probably have a semi-symetrical wing, that will allow for
>decent inverted performance. However, if you want unlimited aerobatics,
>have lots of power, and you don't care much about top
>speed, effciency or range, then a symetrical wing is what you want.
>
>Brett
>
>
> >
> >
> > Thanks!!
> >
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