Testing Stick-built Ribs

[Veeduber[_2_]]

Hi Guys.

Does that title tickle any memory-bones?

Well, let's see if I can tickle them again. First-off come the ground
rules: The data came from "Handbook of Instruction for Airplane
Designers, Structures Tests" Air Corps, U.S.Army (Not available to
the public)

....and apparently not available to many Airplane Designers, too. :-)
(Because nobody could remember seeing the thing.)

Okay, start with the outline of whatever airfoil you're working
with... which tells you right off that this isn't going to be good for
ALL airfoils. The airfoil used in the Army manual looks suspicious
like the USA-35B, which was used in the Piper Cub... and was the first
thing C.G.Taylor tossed on the rubbish heap when he designed the
Taylorcraft. However, the Army's test wing was tapered and of
aluminum construction. It would be interesting to know the history of
this manual since, from all appearances it didn't do the Army Air
Corps much good.

Using whatever outline you're using, starting at the trailing edge,
come forward 10% of the airfoil's chord. The next section takes 43.8%
of your airfoil's length. Next comes the main load-bearing section:
27.1% of your airfoil's chord, and finally the leading edge section --
19.1% of the airfoil's chord.

The weight is distributed as follows: 20% is suspended on the leading
edge section, 40% is suspended on the mid-wing section, and 40% is
suspended on the aft-wing section. You will note that NO LOAD is
placed on the trailing edge of the wing.

The method is a bit unusual (in my opinion) but it matches the

[Brian Whatcott]

Veeduber wrote:
> Hi Guys.
>
> Does that title tickle any memory-bones?
>
> Well, let's see if I can tickle them again. First-off come the ground
> rules: The data came from "Handbook of Instruction for Airplane
> Designers, Structures Tests" Air Corps, U.S.Army (Not available to
> the public)
>
> ...and apparently not available to many Airplane Designers, too. :-)
> (Because nobody could remember seeing the thing.)
>
> Okay, start with the outline of whatever airfoil you're working
> with... which tells you right off that this isn't going to be good for
> ALL airfoils. The airfoil used in the Army manual looks suspicious
> like the USA-35B, which was used in the Piper Cub... and was the first
> thing C.G.Taylor tossed on the rubbish heap when he designed the
> Taylorcraft. However, the Army's test wing was tapered and of
> aluminum construction. It would be interesting to know the history of
> this manual since, from all appearances it didn't do the Army Air
> Corps much good.
>
> Using whatever outline you're using, starting at the trailing edge,
> come forward 10% of the airfoil's chord. The next section takes 43.8%
> of your airfoil's length. Next comes the main load-bearing section:
> 27.1% of your airfoil's chord, and finally the leading edge section --
> 19.1% of the airfoil's chord.
>
> The weight is distributed as follows: 20% is suspended on the leading
> edge section, 40% is suspended on the mid-wing section, and 40% is
> suspended on the aft-wing section. You will note that NO LOAD is
> placed on the trailing edge of the wing.
>
> The method is a bit unusual (in my opinion) but it matches the


This is where your note stops. I expect you wanted to continue by asking
for comments. Coupla thoughts:
There's a freebee 2-D airfoil calculator from an MIT instructor which
shows the shape of the low pressure on the upper surface, and the high
pressure on the lower surface for a whole bunch of airfoils. If you
cut these two shapes out of - lets say - lead sheet
and weighed vertical strips from top and bottom, you would have a
representative load for a particular airfoil station.

But the last time I had that code was two or three computers ago....

So, getting down and dirty:
Say a wing balances at 30% chord, then if you evenly loaded the front
30% with 70% of the load, and the back 70% with 30% of the load,
you balance the turning moment (roughly!)

Your USAAC cite puts roughly that proportion before and after the 30% point.
So it seems to make sense. True, load distribution varies with AoA
yada-yada.....

Brian W

[Bob]

On Jul 25, 6:14*pm, Veeduber > wrote:
> Hi Guys.
>
> Does that title tickle any memory-bones?
>
> Well, let's see if I can tickle them again. *First-off come the ground
> rules: The data came from "Handbook of Instruction for Airplane
> Designers, Structures Tests" *Air Corps, U.S.Army (Not available to
> the public)
>
> ...and apparently not available to many Airplane Designers, too. *:-)
> (Because nobody could remember seeing the thing.)
>
> Okay, start with the outline of whatever airfoil you're working
> with... which tells you right off that this isn't going to be good for
> ALL airfoils. *The airfoil used in the Army manual looks suspicious
> like the USA-35B, which was used in the Piper Cub... and was the first
> thing C.G.Taylor tossed on the rubbish heap when he designed the
> Taylorcraft. *However, the Army's test wing was tapered and of
> aluminum construction. *It would be interesting to know the history of
> this manual since, from all appearances it didn't do the Army Air
> Corps much good.
>
> Using whatever outline you're using, starting at the trailing edge,
> come forward 10% of the airfoil's chord. *The next section takes 43.8%
> of your airfoil's length. *Next comes the main load-bearing section:
> 27.1% of your airfoil's chord, and finally the leading edge section --
> 19.1% of the airfoil's chord.
>
> The weight is distributed as follows: 20% is suspended on the leading
> edge section, 40% is suspended on the mid-wing section, and 40% is
> suspended on the aft-wing section. *You will note that NO LOAD is
> placed on the trailing edge of the wing.
>
> The method is a bit unusual (in my opinion) but it matches the

....and right about there the whole damn shootin' match landed in my
lap...
that is, a lap-top HP 'Pavilion' computer flying home to roost on top
of an outboard keyboard that allows me to type those long, complex
words that some folks like to see in their articles and which if you
try typing on an HP product you may as well throw it all out the door
and plug in your S-100 computer and fire up its Hazeltine terminal
because the chances are about 50-50.

Hell, I throught it was World War Three when all it was happened to be
a sixteen pound tom cat attempting to offer an example of his
affections to a three and a half-pound lap-cat who knew I was the only
feller she'd ever seen who put a 16 ga. shell into his cane every
morning and wasn't ABOUT to take any lip from her boy friend.

The moral of this tale is: There's really no limit to what's liable
to come flying through your kitchen door if you're foolish enough to
leave the damn thing open.

-R.S.Hoover

PS -- the truth is, I had no idea that a combination of feline romance
and hi-tek electronics could actually end up SENDING a message when my
best efforts often lead to failure. And that's the truth.

[[email protected]]

bob, that's as bad as the "dog ate my homework"!

[Bob]

On Jul 27, 4:33*am, wrote:
> bob, that's as bad as the "dog ate my homework"!

--------------------------------------------------------------------------

Gee, Great... that really hurts. But brings to mind a certain

[Brian Whatcott]

Bob wrote:
> On Jul 27, 4:33 am, wrote:
>> bob, that's as bad as the "dog ate my homework"!
>
> --------------------------------------------------------------------------
>
> Gee, Great... that really hurts. But brings to mind a certain


Ya, we know you are faking it. But a great reply, all the same! :-)

Brian W

[Bob]

On Jul 25, 7:01*pm, brian whatcott > wrote:

> Your USAAC cite puts roughly that proportion before and after the 30% point.

[Bob]

On Jul 27, 6:41*pm, brian whatcott > wrote:
>
> Ya, we know you are faking it. But a great reply, all the same! * :-)
>
>-------------------------------------------------------------------------------------------------------

Dear Brian, et al,

It is the craziest thing but I'd swear the cats KNOW I am ill. Okay,
okay... sure; the ol' hunting dog found dead on his master's grave,
I'm talking about some VERY independent cats who now seem considerably
less so; who jump in your lap when before you couldn't BRIBE them to
come over and say hello. They have taken to accompaning me on my
doctor-dictated hikes whereas before they gave such things less than a
yawn's-worth of their Royal Attention. More than passing strange --
folk tales and all that -- it takes on a different emphasis.

But... speaking of strange: On Sunday I had need to visit the local
Lowe's, nearest of several Box Stores. Along the way there were TWO
instances where slightly crazy drivers violated numerous traffic laws
to inquire if I might be interested in selling my 'old bus' (a 1965
VW).

One Crazy Driver, okay. After all, this is California... and it IS a
splittie, etc. But two? That's about one too many.

So... howzabout THIS to rattle your rudder-tab: After I shoot through
(bound to happen, sooner or later, right?) So, after the Last
Flight... the one we ALL gotta make sooner or later, this is to let
you know I'll be keeping an eye on those rib-test procedures. (Just
something to give all the girls something to twitter about... I''ll be
watching :-)

-Bob

[Stealth Pilot[_2_]]

On Tue, 28 Jul 2009 07:51:21 -0700 (PDT), Bob >
wrote:

>On Jul 27, 6:41*pm, brian whatcott > wrote:
>>
>> Ya, we know you are faking it. But a great reply, all the same! * :-)
>>
>>-------------------------------------------------------------------------------------------------------
>
>Dear Brian, et al,
>
>It is the craziest thing but I'd swear the cats KNOW I am ill. Okay,
>okay... sure; the ol' hunting dog found dead on his master's grave,
>I'm talking about some VERY independent cats who now seem considerably
>less so; who jump in your lap when before you couldn't BRIBE them to
>come over and say hello. They have taken to accompaning me on my
>doctor-dictated hikes whereas before they gave such things less than a
>yawn's-worth of their Royal Attention. More than passing strange --
>folk tales and all that -- it takes on a different emphasis.
>
cats desert the dieing.
have you ever thought that they've decided you arent going to just
yet.
it's a promising sign.

et al.

[Steve Hix]

In article >,
Stealth Pilot > wrote:

> On Tue, 28 Jul 2009 07:51:21 -0700 (PDT), Bob >
> wrote:
>
> >On Jul 27, 6:41*pm, brian whatcott > wrote:
> >>
> >> Ya, we know you are faking it. But a great reply, all the same! * :-)
> >>
> >>----------------------------------------------------------------------------
> >>---------------------------
> >
> >Dear Brian, et al,
> >
> >It is the craziest thing but I'd swear the cats KNOW I am ill. Okay,
> >okay... sure; the ol' hunting dog found dead on his master's grave,
> >I'm talking about some VERY independent cats who now seem considerably
> >less so; who jump in your lap when before you couldn't BRIBE them to
> >come over and say hello. They have taken to accompaning me on my
> >doctor-dictated hikes whereas before they gave such things less than a
> >yawn's-worth of their Royal Attention. More than passing strange --
> >folk tales and all that -- it takes on a different emphasis.
> >
> cats desert the dieing.
> have you ever thought that they've decided you arent going to just
> yet.

That, and you're the one with opposable thumbs.

Once they find a can opener that they can operate ...