In Defense of Symmetrical Airfoils

sentencecopyΗλεκτρονική - Συσκευές

13 Οκτ 2013 (πριν από 4 χρόνια και 26 μέρες)

82 εμφανίσεις

I
n

D
e
f
e
n
s
e

o
f

S
y
m
m
e
t
r
i
c
a
l

A
i
r
f
o
i
l
s
F
l
i
g
h
t
l
i
n
e

A
i
r
y

m
u
s
i
n
g
s

b
y

T
o
m

A
r
n
o
l
d

A
s

P
u
b
l
i
s
h
e
d

i
n

t
h
e

A
u
g
u
s
t

2
0
0
4

n
e
w
s
l
e
t
t
e
r

o
f

t
h
e

S
c
a
l
e

S
t
a
f
f
e
l

M
o
d
e
l

A
i
r
p
l
a
n
e

C
l
u
b

o
f

S
a
n

D
i
e
g
o
,

C
a
l
i
f
.
,

G
e
r
a
l
d

S
u
l
l
i
v
a
n
,

e
d
i
t
o
r

I
a
l
w
a
y
s

l
o
v
e

t
o

h
a
n
g

a
r
o
u
n
d

t
h
e

b
i
g

kids
a
n
d

s
e
e

w
h
a
t

t
h
e
y

f
l
y

a
n
d

t
r
y

t
o

f
i
g
u
r
e

o
u
t

T
h
e

S
e
c
r
e
t
.

H
a
v
e

n
o
t

found
T
h
e

S
e
c
r
e
t

y
e
t

b
u
t

i
t

is
fun
t
r
y
i
n
g
.

C
l
a
r
e
n
c
e

M
a
t
h
e
r

h
a
d

a

couple
of
j
u
m
b
o
,

h
i
g
h

f
l
y
i
n
g
,

(does
h
e

b
u
i
l
d

a
n
y

o
t
h
e
r

k
i
n
d
?
)

F
o
l
k
e
r
t
s

r
a
c
e
r
s

a
n
d

t
h
e
y

h
a
d

s
y
m
m
e
t
r
i
c
a
l

a
i
r
f
o
i
l
s
.

W
h
e
n

a
s
k
e
d

w
h
y

h
e

u
s
e
d

them when
t
h
e

r
e
s
t

o
f

t
h
e

w
o
r
l
d

u
s
e
s

f
l
a
t
-
b
o
t
t
o
m
e
d

a
i
r
f
o
i
l
s

h
e

h
a
d

a
n

i
n
t
e
r
e
s
t
i
n
g

l
i
n
e

o
f

r
e
a
s
o
n
i
n
g
.

First (assuming the
s
a
m
e

t
h
i
c
k
n
e
s
s
)

a

s
y
m
m
e
t
r
i
c
a
l

a
i
r
f
o
i
l

h
a
s

less
d
r
a
g

t
h
a
n

a

f
l
a
t

b
o
t
t
o
m

e
x
a
m
p
l
e
.

In fact,
a

s
y
m
m
e
t
r
i
c
a
l

a
i
r
f
o
i
l

h
a
s

t
h
e

s
a
m
e

d
r
a
g

a
s

a

c
i
r
c
u
l
a
r

w
i
r
e

or
p
o
l
e

1
/
1
0

t
h
e

t
h
i
c
k
n
e
s
s

of
t
h
e

a
i
r
f
o
i
l
.

N
o
w

y
o
u

s
e
e

w
h
e
r
e

a
l
l

t
h
e

d
r
a
g

of
a

w
i
r
e

b
r
a
c
e
d

b
i
p
l
a
n
e

c
o
m
e
s

f
r
o
m
.

A

s
y
m
m
e
t
r
i
c
a
l

a
i
r
f
o
i
l

has
another
c
h
a
r
a
c
t
e
r
i
s
t
i
c

t
h
a
t

C
l
a
r
e
n
c
e

used.
A
s

a

f
l
a
t
b
o
t
t
o
m
e
d

a
i
r
f
o
i
l

is
r
o
t
a
t
e
d

t
o

a

h
i
g
h
e
r

a
n
d

h
i
g
h
e
r

a
n
g
l
e

of
a
t
t
a
c
k

(
t
h
i
n
k

stall),
t
h
e

c
e
n
t
e
r

of lift,
w
h
i
c
h

is
b
e
h
i
n
d

t
h
e

c
e
n
t
e
r

of
gravity,
b
e
g
i
n
s

t
o

m
o
v
e

f
o
r
w
a
r
d
,

l
i
t
e
r
a
l
l
y

d
e
c
r
e
a
s
i
n
g

t
h
e

n
o
r
m
a
l

anti-stall
m
o
m
e
n
t

of
a

w
i
n
g
.

I
n

o
t
h
e
r

w
o
r
d
s
,

t
h
e

c
l
o
s
e
r

a

flat
b
o
t
t
o
m
e
d

a
i
r
f
o
i
l

g
e
t
s

t
o

a

s
t
a
l
l
,

t
h
e

m
o
r
e

i
t

w
a
n
t
s

t
o

stall.
S
e
e

t
h
e

d
i
a
g
r
a
m
.

A

s
y
m
m
e
t
r
i
c
a
l

a
i
r
f
o
i
l

d
o
e
s

n
o
t

have
this
characteristic
and
the
center
of
lift
stays
put
through
out
the
whole
stall
evolution
doing
its
best
to
keep
the
airfoil
flying.
C
l
a
r
e
n
c
e

felt
t
h
i
s

b
u
i
l
t
-
i
n

stall
r
e
s
i
s
t
a
n
c
e

k
e
p
t

his
models out
of
trouble
f
a
r

l
o
n
g
e
r

t
h
a
n

t
h
e

flat-
b
o
t
t
o
m
e
d

e
x
a
m
p
l
e
s

a
n
d

t
h
e

e
x
a
m
p
l
e
s

h
e

f
l
e
w

s
u
r
e

s
e
e
m
e
d

t
o

b
e
a
r

i
t

a
l
l

o
u
t
.

I

c
a
n

h
e
a
r

t
h
e

h
o
o
t
s

a
l
r
e
a
d
y

from the
p
e
a
n
u
t

g
a
l
l
e
r
y

as
C
l
a
r
e
n
c
e

c
a
n

m
a
k
e

a
n
y
t
h
i
n
g

f
l
y

w
e
l
l
.

H
i
s

t
r
i
m
m
i
n
g

a
n
d

f
l
y
i
n
g

s
k
i
l
l
s

a
r
e

l
e
g
e
n
d
a
r
y

b
u
t
,

H
e
y
,

i
f

h
e

t
h
i
n
k
s

i
t

w
o
r
k
s
,

l
e
m
m
e

a
t

i
t
!

S
o

I

d
e
c
i
d
e
d

t
o

b
u
i
l
d

a

s
y
m
m
e
t
r
i
c
a
l

w
i
n
g

f
o
r

o
n
e

o
f

m
y

m
a
s
s

l
a
u
n
c
h

h
o
u
n
d
s

a
n
d

p
r
o
m
p
t
l
y

f
o
u
n
d

o
u
t

w
h
y

w
e

b
u
i
l
d

f
l
a
t

b
o
t
t
o
m
e
d

o
n
e
s
-
-
f
l
a
t

b
o
t
t
o
m

i
s

i
n
c
r
e
d
i
b
l
y

e
a
s
y

t
o

b
u
i
l
d

s
t
r
a
i
g
h
t

a
n
d

t
r
u
e

a
n
d

s
y
m
m
e
t
r
i
c
a
l

i
s

i
n
c
r
e
d
i
b
l
y

h
a
r
d

a
s

t
h
e
r
e

i
s

n
o

w
a
y

t
o

anchor
the
whole
structure.
A
f
t
e
r

b
u
i
l
d
i
n
g

6
,

c
o
u
n
t


'
e
m

6,
w
i
n
g
s

I
t
h
i
n
k

I
h
a
v
e

h
i
t

u
p
o
n

a

method
t
h
a
t

w
o
r
k
s

a
n
d

I
h
u
m
b
l
y

s
h
a
r
e

i
t

for
a
n
y

o
t
h
e
r

p
o
o
r

s
o
u
l

w
h
o

t
a
k
e
s

t
h
i
s

o
n
.

S
t
e
p

1
:

B
u
i
l
d

a

f
l
a
t

f
r
a
m
e
w
o
r
k

o
f

t
h
e

w
i
n
g

w
i
t
h

t
h
e

l
e
a
d
i
n
g

e
d
g
e

and the
t
r
a
i
l
i
n
g

e
d
g
e
s

c
o
n
n
e
c
t
e
d

b
y

1
/
1
6
'
"

s
q

w
h
e
r
e

t
h
e

r
i
b
s

g
o
.

C
a
l
l

t
h
e
s
e

"
r
i
b

b
r
a
c
e
s
"

f
o
r

l
a
c
k

o
f

a

b
e
t
t
e
r

w
o
r
d
.

S
t
e
p

2
:

U
n
p
i
n

t
h
e

w
i
n
g

f
r
a
m
e

a
n
d

g
l
u
e

t
h
e

s
y
m
m
e
t
r
i
c
a
l

r
i
b
s

a
g
a
i
n
s
t

t
h
e

1
/
1
6
'
"

sq rib
b
r
a
c
e
s
,

b
u
t

o
n
l
y

g
l
u
e

t
h
e
m

a
t

t
h
e

l
e
a
d
i
n
g

a
n
d

t
r
a
i
l
i
n
g

e
d
g
e
s
.

W
e

w
i
l
l

c
u
t
,
a
w
a
y

t
h
e

c
e
n
t
e
r

s
e
c
t
i
o
n

l
e
a
v
i
n
g
.

the
ends
to
reinforce
the
naturally
weak
attach
points
and
save
some
weight
in
the
process.
S
t
e
p

3
:

L
a
y

t
h
e

f
l
o
p
p
y

a
f
f
a
i
r

b
a
c
k

d
o
w
n

on
t
h
e

w
o
r
k
b
e
n
c
h

a
n
d

p
i
n

i
t

a
t

t
h
e

h
i
g
h

p
o
i
n
t

on
t
h
e

airfoil
to
the
bench.
Glue
a
1/16'"
sq
stringer
along
the
top
from
root
to
tip.
S
t
e
p

4
:

F
l
i
p

t
h
e

a
f
f
a
i
r

o
v
e
r

a
n
d

g
l
u
e

a

s
e
c
o
n
d

s
t
r
i
n
g
e
r

a
t

t
h
e

s
a
m
e

l
o
c
a
t
i
o
n

a
l
o
n
g

t
h
e

b
o
t
t
o
m
.

Y
o
u

h
a
v
e

j
u
s
t

c
o
n
s
t
r
u
c
t
e
d

t
h
e

c
e
n
t
e
r

"
s
p
a
r
"
,

s
o

t
o

s
p
e
a
k
.

S
t
e
p

5
:

C
o
n
t
i
n
u
e

t
o

d
o

t
h
e

s
a
m
e

a
t

e
a
c
h

o
f

t
h
e

p
o
i
n
t
s

y
o
u

w
a
n
t

a

s
p
a
n
-
w
i
s
e

s
t
r
i
n
g
e
r
,

f
l
i
p
p
i
n
g

t
h
e

wing
over
to
complete
pairs
top
and
bottom
as
you
go
along.
S
t
e
p

6
:

F
i
l
l

in at
t
h
e

r
o
o
t

r
i
b

w
i
t
h

s
o
f
t

1
/
8
'
"

X

1
/
1
6
'
"

between
t
h
e

s
t
r
i
n
g
e
r
s

over the
e
d
g
e

of
t
h
e

r
o
o
t

r
i
b

a
n
d

s
a
n
d

F
L
A
T

b
e
t
w
e
e
n

t
h
e

s
t
r
i
n
g
e
r
s
.

What
t
h
i
s

g
i
v
e
s

y
o
u

is
a

s
t
r
u
c
t
u
r
e

y
o
u

s
o
r
t

of
s
e
m
i
-
b
u
i
l
t

i
n

t
h
e

a
i
r

a
n
d

s
e
m
i

built
on
t
h
e

w
o
r
k

board. The
a
i
r
f
o
i
l

i
s

b
u
i
l
t

u
p

o
f

f
l
a
t

planes, which I
f
i
n
d

m
o
r
e

v
i
s
u
a
l
l
y

a
p
p
e
a
l
i
n
g

f
o
r

a

m
e
t
a
l

w
i
n
g

as
o
p
p
o
s
e
d

t
h
e

h
i
l
l
s
-
a
n
d
-
v
a
l
l
e
y
s

of
c
o
n
v
e
n
t
i
o
n
a
l

r
i
b

a
n
d

s
t
r
i
n
g
e
r

c
o
n
s
t
r
u
c
t
i
o
n
.

Y
o
u

a
l
s
o

d
i
d

n
o
t

h
a
v
e

t
o

s
t
r
u
g
g
l
e

w
i
t
h

l
i
n
i
n
g

u
p

n
o
t
c
h
e
s

a
n
d

s
t
r
i
n
g
e
r
s
,

w
h
i
c
h

I
a
l
s
o

f
i
n
d

is
a

l
o
s
i
n
g

b
a
t
t
l
e
.

I
h
a
v
e

n
o
t

a
d
d
r
e
s
s
e
d

t
h
e

a
t
t
a
c
h
m
e
n
t

method
of
t
h
e

w
i
n
g

t
o

t
h
e

f
u
s
e
l
a
g
e

as
y
o
u

c
a
n

u
s
e

a
n
y

n
u
m
b
e
r

of
w
a
y
s

a
n
d

l
e
t

m
e

k
n
o
w

w
h
e
n

y
o
u

f
i
n
d

a

r
e
a
l
l
y

g
o
o
d

o
n
e
.

O
n

m
y

particular
e
x
a
m
p
l
e
,

a

Short
S
e
a
m
e
w
,

there
w
a
s

a

d
i
h
e
d
r
a
l

a
n
g
l
e

built
i
n
t
o

t
h
e

o
u
t
e
r

h
a
l
f

t
h
a
t

d
r
o
v
e

me nuts and
a
c
c
o
u
n
t
e
d

f
o
r

3

o
f

t
h
e

6

w
i
n
g
s

u
n
t
i
l

I

f
i
g
u
r
e
d

i
t

o
u
t
.

I
n

c
a
s
e

y
o
u

a
r
e

f
a
c
e
d

w
i
t
h

t
h
i
s

h
e
r
e

i
s

m
y

s
o
l
u
t
i
o
n
.

S
t
e
p
1
:

A
t

t
h
e

d
i
h
e
d
r
a
l

b
r
e
a
k
,

s
l
i
p

i
n

2

1/32'" sheet
ribs
a
n
d

D
O
N
'
T

g
l
u
e

t
h
e
m

t
o

the stringers
as
y
o
u

a
t
t
a
c
h

t
h
e

s
t
r
i
n
g
e
r
s

t
o

a
l
l

t
h
e

o
t
h
e
r

r
i
b
s
.

S
t
e
p

2
:

P
i
n

t
h
e

w
i
n
g

d
o
w
n

a
t

t
h
e

m
a
i
n

"
s
p
a
r
"

a
n
d

g
l
u
e

t
h
e

i
n
s
i
d
e

l
o
o
s
e

r
i
b

i
n

p
l
a
c
e

a
n
d

p
e
r
f
e
c
t
l
y

v
e
r
t
i
c
a
l
.

U
s
e

a

l
i
t
t
l
e

s
q
u
a
r
e

p
i
e
c
e

o
f

b
a
l
s
a

t
o

h
e
l
p
.

S
t
e
p

3
:

N
o
w

t
a
k
e

a

v
e
r
y

c
a
r
e
f
u
l
l
y

c
u
t

w
e
d
g
e

o
f

1
/
6
4
'
"

ply
or
balsa
that
is
cut
to
the
dihedral
angle
and slip in
d
o
w
n

b
e
t
w
e
e
n

t
h
e

t
w
o

r
i
b
s

a
n
d

g
l
u
e

t
h
e

s
e
c
o
n
d

i
n
t
o

p
l
a
c
e
.

S
l
i
d
e

y
o
u
r

w
e
d
g
e

a
l
o
n
g

t
h
e

c
h
o
r
d

b
e
f
o
r
e

g
l
u
i
n
g

t
o

i
n
s
u
r
e

t
h
e

a
n
g
l
e

i
s

t
h
e

s
a
m
e

a
l
l

a
l
o
n
g

t
h
e

r
i
b
.

S
t
e
p

4
:

C
u
t

t
h
e

o
u
t
e
r

h
a
l
f

f
r
e
e
,

c
l
e
a
n

u
p

t
h
e

s
u
r
f
a
c
e

between
t
h
e

2
ribs
a
n
d

r
e
g
l
u
e

a
t

t
h
e

n
o
w

c
o
r
r
e
c
t

a
n
g
l
e
.

S
t
e
p

5
:

F
i
l
l

i
n

o
n

t
h
e

t
o
p

o
f

t
h
i
s

d
i
h
e
d
r
a
l

r
i
b

w
i
t
h

s
o
f
t

1
/
8
'
"

f
i
l
l

a
s

y
o
u

d
i
d

o
n

t
h
e

r
o
o
t

r
i
b
.

.

In
t
h
i
s

w
h
o
l
e

e
v
o
l
u
t
i
o
n

y
o
u

n
e
e
d

p
r
e
c
i
s
e
l
y

p
l
o
t
t
e
d

ribs
for
t
h
e

s
t
r
i
n
g
e
r
s

t
o

l
i
e

on.
I
h
a
v
e

found
t
h
e

use
o
f

"
S
i
m
p
l
e
x
"

a
i
r
f
o
i
l
s

t
o

b
e

i
d
e
a
l

a
n
d

t
h
e
y

work marvelously.
F
o
r

t
h
o
s
e

n
o
t

f
a
m
i
l
i
a
r

w
i
t
h

the term, a
S
i
m
p
l
e
x

a
i
r
f
o
i
l

i
s

a
n

a
i
r
f
o
i
l

t
h
a
t

w
h
e
n

y
o
u

c
u
t

a
n
y

l
e
n
g
t
h

o
f
f

t
h
e

t
r
a
i
l
i
n
g

e
d
g
e
,

y
o
u

w
i
l
l

a
l
w
a
y
s

h
a
v
e

a

p
e
r
f
e
c
t
l
y

p
r
o
p
o
r
t
i
o
n
a
l

s
m
a
l
l
e
r

e
x
a
m
p
l
e

left.
C
o
n
t
r
a
r
y

t
o

w
h
a
t

I
h
a
v
e

s
e
e
n

advocated, this
w
i
l
l

N
O
T

w
o
r
k

b
y

j
u
s
t

c
h
o
p
p
i
n
g

o
f
f

t
h
e

t
a
i
l

o
f

a
n
y

o
l
d

a
i
r
f
o
i
l
.

I
f

y
o
u

d
o
,

b
y

t
h
e

t
i
m
e

y
o
u

get to
t
h
e

t
i
p

rib, you will
h
a
v
e

a

v
e
r
y

d
i
f
f
e
r
e
n
t

s
h
a
p
e

and worse,
the stringers
will not
l
a
y

f
l
a
t
.

T
h
e

S
i
m
p
l
e
x

f
a
m
i
l
y

c
o
m
e
s

f
r
o
m

a

t
y
p
e

o
f

h
e
l
i
x

t
h
a
t

a
l
m
o
s
t

i
d
e
n
t
i
c
a
l
l
y

m
i
m
i
c
s

t
h
e

s
h
a
p
e
s

we
use
w
h
i
c
h

r
e
a
l
l
y

a
r
e

n
o
t

precise
a
n
y
w
a
y
.

I
h
a
v
e

m
a
d
e

u
p

f
a
m
i
l
y

of
S
i
m
p
l
e
x
.

a
!
[
f
o
i
l
s

(%
of
c
h
o
r
d

s
u
c
h

a
s

6
%

c
h
o
r
d
,

8
%

c
h
o
r
d
,

e
t
c
.
)

a
n
d

m
o
u
n
t
e
d

t
h
e
m

t
o

l
i
t
h
o
g
r
a
p
h
i
c

p
l
a
t
e
-
-
e
a
s
y

t
o

c
u
t

a
n
d

s
h
a
p
e
.

I

then just slice
o
u
t

w
h
a
t

I

n
e
e
d

f
r
o
m

s
h
e
e
t

b
a
l
s
a

at whatever chord
i
s

d
e
s
i
r
e
d

a
n
d

t
h
e
y

a
l
l

a
r
e

p
r
o
p
o
r
t
i
o
n
a
l
.

W
o
r
k
s

l
i
k
e

a

c
h
a
r
m
.

So
are
there
any
drawbacks
to
this
method?
The
only
one
I
have
found
is
that
it
gets
hard
to
do
in
v
e
r
y

t
h
i
n

a
i
r
f
o
i
l

e
x
a
m
p
l
e
s
.

T
h
e

s
t
r
i
n
g
e
r
s

w
o
r
k

b
e
s
t

w
h
e
n

t
h
e
y

a
r
e

s
q
u
a
r
e

for
e
a
s
e

of
g
l
u
i
n
g

s
o

I
h
a
v
e

a

h
a
r
d

t
i
m
e

d
o
i
n
g

t
h
e

1
/
3
2

X

1
/
1
6

s
t
r
i
n
g
e
r
s

t
h
a
t

I
l
i
k
e
.

I
a
m

s
t
u
c
k

w
i
t
h

1
/
1
6

s
q
.

C
l
a
r
e
n
c
e

u
s
e
d

1
/
3
2

s
h
e
e
t

r
i
b
s

a
n
d

1
/
3
2

X 1/16
s
t
r
i
n
g
s

n
o
t
c
h
e
d

i
n
t
o

t
h
e

r
i
b
s

a
n
d

h
e

d
i
d

a
d
m
i
t

t
h
a
t

i
t

t
o
o
k

a

l
o
t

o
f

c
a
r
e
f
u
l

w
o
r
k

a
n
d

j
i
g
g
i
n
g

t
o

b
u
i
l
d

h
i
s

w
i
n
g
s

b
u
t
,

B
o
y
,

d
i
d

t
h
e
y

l
o
o
k

n
i
c
e
.

F
o
r

t
h
o
s
e

i
n
t
e
r
e
s
t
e
d

i
n

t
h
e

S
i
m
p
l
e
x

a
i
r
f
o
i
l

f
a
m
i
l
y
,

I
found
s
e
v
e
r
a
l

e
x
a
m
p
l
e
s

on
t
h
e

web
b
y

j
u
s
t

t
y
p
i
n
g

i
n

"
S
i
m
p
l
e
x

A
i
r
f
o
i
l
s
"
.

J
u
s
t

p
r
i
n
t

t
h
e
m

o
u
t
-
-
a
n
y

s
i
z
e

i
s

f
i
n
e

a
n
d

t
a
k
e

t
o

K
i
n
k
o
'
s

a
n
d

e
x
p
a
n
d

t
o

w
h
a
t

e
v
e
r

w
o
r
k
i
n
g

s
i
z
e

y
o
u

n
e
e
d

t
o

m
a
k
e

s
o
m
e

s
h
o
p

t
e
m
p
l
a
t
e
s
.

Y
o
u

c
a
n

use
them
t
o

m
a
k
e

s
e
m
i
-
s
y
m
m
e
t
r
i
c
a
l

a
i
r
f
o
i
l
s

o
f

a
n
y

t
h
i
c
k
n
e
s
s

a
s

w
e
l
l

a
s

u
n
d
e
r

c
a
m
b
e
r
e
d

j
u
s
t

b
y

flipping them
o
v
e
r

a
n
d

u
p
s
i
d
e

d
o
w
n
.