Texas Parasol Plans...

Hi Group:

Cla

Looking at the calculations for the spar, spar.pdf I do not see your
interpretation. The 67000 psi value is Bearing Ultimate, not tensile.

A MATWEB lookup is in order:

6061-T6

Tensile ultimate: 45000
Tensile yield : 39000

Bearing ultimate: 88000
Bearing Yield : 56000

The values presented in the spar calculation are correct, and the
bearing ultimate of 67000 is below spec.

So where is the spar calc using bad values except, as you say, in the
initial assumptions of 244 pounds versus 288?

Curtis Scholl


Just a little more input from another more knowledgeable than
myself. The material that the plans and the airplane use is 6061t6
correct? The calculations show the material or the identifier as being
6061. The problem in the shown calcs is that the numbers he is using
at 68000psi tensile is higher than the ultimate strength of 2024-t4
which is given at 64000. 6061t6 is only 45,000psi ultimate and 39,900
yield.

It's no wonder the wing was failing at 2g.

*** Free account sponsored by SecureIX.com ***
*** Encrypt your Internet usage with a free VPN account from http://www.SecureIX.com ***

On Mon, 27 Feb 2006 15:14:24 -0500, Curtis Scholl
wrote:

Cla

Looking at the calculations for the spar, spar.pdf I do not see your
interpretation. The 67000 psi value is Bearing Ultimate, not tensile.

A MATWEB lookup is in order:

6061-T6

Tensile ultimate: 45000
Tensile yield : 39000

Bearing ultimate: 88000
Bearing Yield : 56000

The values presented in the spar calculation are correct, and the
bearing ultimate of 67000 is below spec.


Thjat may well be true, but is "bearing strength" the proper
charachteristic of the material to be used in this calculation?

As I said - not an engineer - just asking.
Please explain for the rest of us how the bearing ultimate and / or
yeild values impact the calculation, vs tensile.
*** Free account sponsored by SecureIX.com ***
*** Encrypt your Internet usage with a free VPN account from http://www.SecureIX.com ***

On Mon, 27 Feb 2006 16:02:51 -0500, clare at snyder.on.ca wrote:

On Mon, 27 Feb 2006 15:14:24 -0500, Curtis Scholl
wrote:

Cla

Looking at the calculations for the spar, spar.pdf I do not see your
interpretation. The 67000 psi value is Bearing Ultimate, not tensile.

A MATWEB lookup is in order:

6061-T6

Tensile ultimate: 45000
Tensile yield : 39000

Bearing ultimate: 88000
Bearing Yield : 56000

The values presented in the spar calculation are correct, and the
bearing ultimate of 67000 is below spec.


Thjat may well be true, but is "bearing strength" the proper
charachteristic of the material to be used in this calculation?

As I said - not an engineer - just asking.
Please explain for the rest of us how the bearing ultimate and / or
yeild values impact the calculation, vs tensile.
*** Free account sponsored by SecureIX.com ***
*** Encrypt your Internet usage with a free VPN account from http://www.SecureIX.com ***

bearing strength

The maximum bearing load at failure divided by the effective bearing
area.
In a pinned or riveted joint, the effective area is calculated as the
product of the diameter of the hole and the thickness of the bearing
member. ASM, 1



How does this impact the failure of the wing structure by buckling and
failure of the main spar???
*** Free account sponsored by SecureIX.com ***
*** Encrypt your Internet usage with a free VPN account from http://www.SecureIX.com ***

Cla

Bearing properties are used when designing mechanically fastened joints.
The purpose of a bearing test is to determine the the deformation of a
hole as a function of the applied bearing stress. The test specimen is
basically a piece of sheet or plate with a carefully prepared hole some
standard distance from the edge. Edge-to-hole diameter ratios of 1.5 and
2.0 are common. A hardened pin is inserted through the hole and an AXIAL
load applied to the specimen and the pin. The bearing stress is computed
by dividing the load applied to the pin, which bears against the edge of
the hole, by the bearing area (the product of the pin diameter and the
sheet or plate thickness).

Different axis and on edge rather than in tension or compression. The
flat surface described by the hole in the part as it passes through the
thickness of the tube or plate of the hole. The stress is spread through
the material differently.

Curtis S.

And I am not an engineer either, I make rocket motors, and need this
information constantly.



clare at snyder.on.ca wrote:
On Mon, 27 Feb 2006 15:14:24 -0500, Curtis Scholl
wrote:


Cla

Looking at the calculations for the spar, spar.pdf I do not see your
interpretation. The 67000 psi value is Bearing Ultimate, not tensile.

A MATWEB lookup is in order:

6061-T6

Tensile ultimate: 45000
Tensile yield : 39000

Bearing ultimate: 88000
Bearing Yield : 56000

The values presented in the spar calculation are correct, and the
bearing ultimate of 67000 is below spec.



Thjat may well be true, but is "bearing strength" the proper
charachteristic of the material to be used in this calculation?

As I said - not an engineer - just asking.
Please explain for the rest of us how the bearing ultimate and / or
yeild values impact the calculation, vs tensile.
*** Free account sponsored by SecureIX.com ***
*** Encrypt your Internet usage with a free VPN account from http://www.SecureIX.com ***

On Mon, 27 Feb 2006 16:38:44 -0500, Curtis Scholl
wrote:

Cla

Bearing properties are used when designing mechanically fastened joints.
The purpose of a bearing test is to determine the the deformation of a
hole as a function of the applied bearing stress. The test specimen is
basically a piece of sheet or plate with a carefully prepared hole some
standard distance from the edge. Edge-to-hole diameter ratios of 1.5 and
2.0 are common. A hardened pin is inserted through the hole and an AXIAL
load applied to the specimen and the pin. The bearing stress is computed
by dividing the load applied to the pin, which bears against the edge of
the hole, by the bearing area (the product of the pin diameter and the
sheet or plate thickness).

Different axis and on edge rather than in tension or compression. The
flat surface described by the hole in the part as it passes through the
thickness of the tube or plate of the hole. The stress is spread through
the material differently.

Curtis S.

And I am not an engineer either, I make rocket motors, and need this
information constantly.


I understand what the bearing strength is - I'm just saying it is the
wrong strength to design to when designing the wing, as the
compressive, shear, and tension strengths more realistically represent
the loads in the wing.

If you substitute the tensile strength numbers into the calculations,
I'll bet you find the wing fails around 2 Gs, which is what the test
found.
*** Free account sponsored by SecureIX.com ***
*** Encrypt your Internet usage with a free VPN account from http://www.SecureIX.com ***

Cla

Bearing strength is for the Connecting Points of all those items you
mentioned. And the engineer stopped the test before complete failure
from what I read.

Excessive deflection is not a failure mode unless the engineer states it
is out of spec. And again, what was the sandbag testing weight at which
the testing was stopped? And again, excessive deflection where? In the
skins? In the Spars? in the struts?

You stated:
**
"No- Gary built a wing according to plans and sandbag tested it under
an engineer's supervision. The engineer stopped the loading before
failure because of excessive deflection IIRC."
**

And I have a set of plans, and I recall seeing the sleeves being called
out in the manual. And I don't see where aluminum skins are in the
plans. Again, deflection where?

"And sleaves in the spars by your own admission. Which are NOT in the
plans."

See wing plan D-WING3. It clearly shows what to do on the wing as for
the sleeve inserts to reinforce the connecting points, wing to cabane,
and strut to wing.

Look, this aircraft flies, in it's designed weight class, it has worked
for many years. The designer flies it. There are many copies flying, and
the death rate is not "significant" considering what happened in the
accident reports.

As you said, Clare, you are not an engineer. And you don't have current
validated DATA to back you up. I have stated instances of you being
incorrect in your assumptions. And in one of the instances, given you
the reference for corrections of your statements.

We are done. No response is necessary or wanted. This will be an agree
to disagree situation and no further contact is warranted.

Curtis Scholl

On Tue, 28 Feb 2006 09:50:32 -0500, Curtis Scholl
wrote:

Cla

Bearing strength is for the Connecting Points of all those items you
mentioned. And the engineer stopped the test before complete failure
from what I read.

Excessive deflection is not a failure mode unless the engineer states it
is out of spec. And again, what was the sandbag testing weight at which
the testing was stopped? And again, excessive deflection where? In the
skins? In the Spars? in the struts?

The wing was tested to 2 G's at 600 lb gross. At that point the spars
were ready to fail if I recall correctly.

You stated:
**
"No- Gary built a wing according to plans and sandbag tested it under
an engineer's supervision. The engineer stopped the loading before
failure because of excessive deflection IIRC."
**

And I have a set of plans, and I recall seeing the sleeves being called
out in the manual. And I don't see where aluminum skins are in the
plans. Again, deflection where?

The wing was tested with NO ALUMINUM SKINS. There are doublers at the
arttach points in the plans, but the spars are not doubled between the
root and the struts, which is where the spar is not up to the job from
what I gathered. I'll be talking to Gary tomorrow

"And sleaves in the spars by your own admission. Which are NOT in the
plans."

See wing plan D-WING3. It clearly shows what to do on the wing as for
the sleeve inserts to reinforce the connecting points, wing to cabane,
and strut to wing.

Look, this aircraft flies, in it's designed weight class, it has worked
for many years. The designer flies it. There are many copies flying, and
the death rate is not "significant" considering what happened in the
accident reports.

As you said, Clare, you are not an engineer. And you don't have current
validated DATA to back you up. I have stated instances of you being
incorrect in your assumptions. And in one of the instances, given you
the reference for corrections of your statements.

We are done. No response is necessary or wanted. This will be an agree
to disagree situation and no further contact is warranted.

Curtis Scholl

*** Free account sponsored by SecureIX.com ***
*** Encrypt your Internet usage with a free VPN account from http://www.SecureIX.com ***

Curtis Scholl wrote:
Cla

Bearing strength is for the Connecting Points of all those items you
mentioned. And the engineer stopped the test before complete failure
from what I read.

Excessive deflection is not a failure mode unless the engineer states it
is out of spec. And again, what was the sandbag testing weight at which
the testing was stopped? And again, excessive deflection where? In the
skins? In the Spars? in the struts?

I disagree. Excessive deflection is a failure mode if it has
sufficient
adverse impact on function or safety, without regard to whether or
not any particular engineer realized it and said so.

That is more a criticism of the wording you used, than it is of the
implied question--How do we know the deflection was excessive?

(And what was it that deflected?)

--

FF

On Tue, 28 Feb 2006 09:50:32 -0500, Curtis Scholl
wrote:

Clare wrote:

"No- Gary built a wing according to plans and sandbag tested it under
an engineer's supervision. The engineer stopped the loading before
failure because of excessive deflection IIRC."
**

As you said, Clare, you are not an engineer. And you don't have current
validated DATA to back you up. I have stated instances of you being
incorrect in your assumptions. And in one of the instances, given you
the reference for corrections of your statements.



Just an update on the testing procedure and results on the TP wing
tested at Kitchener Waterloo International Airport last year.

The wing was instrumented with strain guages. The main spar was
bending significantly between the Cabane mounting and the strut, and
the strain readings were beyond the limits the engineer was
comfortable with at 2Gs testing for a 600 lb plane.Failure was
IMMINENT.
*** Free account sponsored by SecureIX.com ***
*** Encrypt your Internet usage with a free VPN account from http://www.SecureIX.com ***

clare at snyder.on.ca wrote

Just an update on the testing procedure and results on the TP wing
tested at Kitchener Waterloo International Airport last year.

The wing was instrumented with strain guages. The main spar was
bending significantly between the Cabane mounting and the strut, and
the strain readings were beyond the limits the engineer was
comfortable with at 2Gs testing for a 600 lb plane.Failure was
IMMINENT.

I don't understand why the testing did not continue. Seems to me that
having someone say that failure was imminent, based on strain gauges, leaves
a lot of room for opinion to creep in.
--
Jim in NC