MadSci Network: Physics Query:

### Re: How does a loop paper airplane gain lift?

Date: Fri Oct 20 09:39:52 2000
Posted By: Kenneth Chivers, Grad student, B.S. Aerospace Engineering, In school for MBA:Management of Information Systems, NAWCAD, Lakehurst, NJ
Area of science: Physics
ID: 968174426.Ph
Message:
```
In the "wingless wonder" example, the top part of the loop, where the
straw was afixed is too disrupted to provide decent lift, however without
the straw body any standard flight path, except straight down, would be
impossible.  There are 2 components here.  First, is distributed weight,
which affects stability.  Second, is distributed lift, the "wing" or as
generalized, the lifting body/surface.

In your loop, as well as in the teacher's loop, the loop could easily
break down into four simple sections-right, left, top and bottom-acting as
four lifting surfaces.  The air flow is faster down the center of the
loop, due to bernoulli's therom and the laws of conservation.  The volume
flow rate ((m^3)/sec) must therefore be the same on the inside and outside
of the loop.  Due to the resultant three-dimensional effect of the "loop"
design, the air flowing into the loop is actually streamlined or tunneled
in, while the air outside the loop is relatively unaffected and slower.
The result is a lower pressure and faster moving air flow over the inner
surface of the bottom half of the loop vs. the underside/outside portion.
This results in lift, the upward difference in pressure between the two
surfaces.

On the upper half of the loop, you have a more readily understood air
flow, more like a traditional wing.  This upper half is the second
contibuting lift surface.

It is the interplay between the lifting forces and gravity which lend
to "flight."  Focusing on straight-forward flight, you'll need the center
of lift either at or in-front of the center of gravity.  Only
experimentation can find the best location for such a design.

In your design you'd have to think a lot about this interplay, as
your center of lift will tend to be behind your center of gravity and
significantly impair flight.  You would also need a fairly rigid and
extremely light material, and you'd have to think really hard about where
you put the wheels.  In the end you'd be building a miniature, but very
complex, ultra-light air craft.  It could be done, but you'd be looking at
an expensive life-long hobby :)

Good luck!

Ken

```

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