Testing On The Cheap

"Brian Whatcott" schrieb im Newsbeitrag
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And it is much the same with airframes: you know where the heavy point
loads are applied, [engine mount, seats??] so if you support at those
points, and load the wing,
then you are going to live a long happy life.

absolutely not so! the seats are designed to carry max passenger weight
times safe G-load times 1.5 (usually). This is way less than the 2 tons you
will pack on the wings. Same with the engine mount. I don't like to know how
many guys flying around in a pre-damaged structure caused by stupid static
load testing.

rattlesnake wrote:

And it is much the same with airframes: you know where the heavy point
loads are applied, [engine mount, seats??] so if you support at those
points, and load the wing,
then you are going to live a long happy life.

absolutely not so! the seats are designed to carry max passenger weight
times safe G-load times 1.5 (usually).

Well, how about that!
And I thought seat belts were often specified at 29 g's. Silly me!

:-)

Brian W

"Brian Whatcott" schrieb im Newsbeitrag
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Well, how about that!
And I thought seat belts were often specified at 29 g's. Silly me!

we talk about seats, not seat belts. How many G's do you think will your
C-150, -172 **seats** be good for?

rattlesnake wrote:
"Brian Whatcott" schrieb im Newsbeitrag
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.....

Well, how about that!
And I thought seat belts were often specified at 29 g's. Silly me!

we talk about seats, not seat belts. How many G's do you think will your
C-150, -172 **seats** be good for?



Well, anonymous poster, you don't need my opinion. And I don't have a
demonstrated load case on those seats.
But take a look at that test case you mentioned: 2 tons on the wings.
Let's say you were demonstrating a 4 g load capability. That would imply
the gross wt is 1000 lbs.
If the engine weighs 220 lb (for a 100 HP) and the two seats can carry
200 lb wetware each - that would amount to 620 lb. Then the airframe
would weigh say 380 lb.

If you were a clueful designer interested in proving a test article, you
might want to ENSURE that a support on the seats, the engine mount and a
the empennage could react the wing proof loads. That would be a smart
thing to do, don't you think?

Do you really, really think an airframe designer hasn't thought it through?
Shouldn't you?

Brian W

"Brian Whatcott" schrieb im Newsbeitrag
news .....
Do you really, really think an airframe designer hasn't thought it
through?
Shouldn't you?

The airframe designer hasn't thought it through, at least of my plans-build
'kitplane'. This aircraft was designed to fly nicely and it shows it really
does. But it absolutely was not designed for static load testing (which in
my view was a smart decision, because designing-in hardpoints which are
completely useless in flight is just adding dead weight). Besides - you
can't just add up the support capability of seats and engine mount by
ignoring the moment arms of your construction.

rattlesnake wrote:
"Brian Whatcott" schrieb im Newsbeitrag
news ....
Do you really, really think an airframe designer hasn't thought it
through?
Shouldn't you?

The airframe designer hasn't thought it through, at least of my plans-build
'kitplane'. This aircraft was designed to fly nicely and it shows it really
does. But it absolutely was not designed for static load testing (which in
my view was a smart decision, because designing-in hardpoints which are
completely useless in flight is just adding dead weight). Besides - you
can't just add up the support capability of seats and engine mount by
ignoring the moment arms of your construction.


And the moment legs, moment feet, etc....

Jerry Wass wrote:
rattlesnake wrote:
"Brian Whatcott" schrieb im Newsbeitrag
news ....
Do you really, really think an airframe designer hasn't thought it
through?
Shouldn't you?

The airframe designer hasn't thought it through, at least of my
plans-build 'kitplane'. This aircraft was designed to fly nicely and
it shows it really does. But it absolutely was not designed for static
load testing (which in my view was a smart decision, because
designing-in hardpoints which are completely useless in flight is just
adding dead weight). Besides - you can't just add up the support
capability of seats and engine mount by ignoring the moment arms of
your construction.

And the moment legs, moment feet, etc....


Hehe....yes, indeed.
But hopefully in a static test (if it IS a static test) the clockwise
moments equal the anticlock moments.
Guess what? If they don't add to zero, the thing rotates.
No special hardpoints called for - just spread the reaction for test
loads proportionate to the mass involved. The design MUST be able to
react the loads due to the limit stresses on the aircraft mass as is,
else it's not a load test!
And a last thought for the anonymous poster: if an experimental design
has not been static tested at least once, you take your life in your hands.
And that's the great beauty of this free society - if you want to risk
killing yourself, you can. (But not in Germany under German rules, only
FAA rules)

Brian W

"Jerry Wass" schrieb im Newsbeitrag
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And the moment legs, moment feet, etc....

EOD

Jerry Wass wrote:
rattlesnake wrote:
"Brian Whatcott" schrieb im Newsbeitrag
news ....
Do you really, really think an airframe designer hasn't thought it
through?
Shouldn't you?

The airframe designer hasn't thought it through, at least of my
plans-build 'kitplane'. This aircraft was designed to fly nicely and
it shows it really does. But it absolutely was not designed for static
load testing (which in my view was a smart decision, because
designing-in hardpoints which are completely useless in flight is just
adding dead weight). Besides - you can't just add up the support
capability of seats and engine mount by ignoring the moment arms of
your construction.

And the moment legs, moment feet, etc....

But just momentarily.

Dan, U.S. Air Force, retired

On Jul 3, 10:49*am, "rattlesnake" wrote:


Destruct static testing done in a non-silly and relevant manner. Kind
of cool to see that they predicted the failure mode and location. The
wing was designed within a couple of percent of the goal. No weight
sacrificed here.


http://www.youtube.com/watch?v=pe9PVaFGl3o