Today's Message Index:
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1. 10:53 AM - Re: Re: Wing Strut Attachment ((null) raykrause)
2. 11:27 AM - Re: Wing Strut Attachment (taildrags)
3. 11:39 AM - Re: Wing Strut Attachment (taildrags)
4. 02:32 PM - Re: No Title (jarheadpilot82)
Message 1
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| Subject: | Re: Wing Strut Attachment |
Oscar,
THANKS! Well done and well presented. Now I feel more confident that my win
g will stay on the SkyScout as it flies for the first time!
Here's how I approached my attach point of the strut to the wing.
Sent from my iPad
On Jan 6, 2018, at 7:32 PM, Clif Dawson <cdawson5854@shaw.ca> wrote:
Now if the rest of our beloved beast matched these figures ----- goodby Sukh
oi. :-)
Attached are pics of my strut ends and the jury struts on my Hemlock struts.
Just for comparison, you understand.
Clif
"Hell, there are no rules here; we're trying to accomplish something." (Thom
as Edison)
Handle every Stressful situation like a dog.
If you can't eat it or play with it,
Piss on it and walk away.
I=C3=A2?Tve taken a look at the forces in the wing lift struts of the Air Ca
mper. To run the analysis, I=C3=A2?Tve used the dimensions given in the Orri
n Hoopman (1933-34) plans to create the geometry, but there=C3=A2?Ts not a l
ot of difference in any of the others that are commonly used. The main lift
strut length is given as 89-3/4=C3=A2?=C2=9D between the bolt holes, the fr
ont cabane length is given as 21-1/4=C3=A2?=C2=9D, and the distance from the
cabane mounting point to the lift strut mounting point at the bottom of the
fuselage side is 22-3/4=C3=A2?=C2=9D, so that side of the triangle is 44=C3
=A2?=C2=9D. With those two dimensions, we find that the angle that the lift
strut makes with the bottom of the wing is 29.4 degrees.
Assuming an aircraft gross weight of 1,088 lb and a design loading of +3.8G (
normal category aircraft), we get a total load to be supported by the wing o
f 4,134 lb, and each half of the wing thus has to support 2,067 lb. Accordin
g to the source quoted in my spar strength article in the BPA Newsletter (No
el Becar=C3=A2?Ts analysis in a 1963 Sport Aviation), the main spar in a str
ut-braced monoplane at a high positive angle of attack carries about 84% of t
he total load, so that results in 1,737 lbs that each front lift strut carri
es.
If the load on the spar where the lift strut attaches is 1,737 lbs and the s
trut is at an angle of 29.4 degrees to the wing, the tensile force in the st
rut will be 1737/(sin 29.4) = 3,538 lbs. This is the force that every ele
ment in the lift strut assembly must meet or exceed in order for the wing to
sustain +3.8G loading.
--------
Oscar Zuniga
Medford, OR
Air Camper NX41CC "Scout"
A75 power, 72x36 Culver prop
<IMG_1317.JPG>
<IMG_1314.JPG>
<IMG_1289.JPG>
<IMG_1472.JPG>
<unladenswallow1.JPG>
Message 2
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| Subject: | Re: Wing Strut Attachment |
Clif; those are beautiful struts and fittings there! Now, just for comparison
you understand, let's look at Western hemlock. Common references for mechanical
properties of hemlock show a modulus of rupture as being 11,300 psi and many
references estimate that the ultimate tensile strength of wood in the direction
parallel to the grain is 80% of the modulus of rupture, so about 9,040 psi.
Your struts look like they are somewhat larger than the Carlson small extruded
aluminum struts but I've got the data for those so I'll use what I've got.
The cross-sectional area of the aluminum strut is 1.8603 sq.in., so a solid
Hemlock strut with the same outside dimensions as the Carlson strut should be
able to carry a tension load of some 16,800 lbs.
I doubt that your struts are under-built. If you can catch the Sukhoi, see if
you can out-maneuver it ;o)
--------
Oscar Zuniga
Medford, OR
Air Camper NX41CC "Scout"
A75 power, 72x36 Culver prop
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=477155#477155
Message 3
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| Subject: | Re: Wing Strut Attachment |
John; many cranes have a scale rigged right into the hoist cable. Some with digital
readout, some with remote readout in the operator cab. If you know people
with cranes, I'm sure they have scales.
You can also epoxy a strain gauge onto a section of bar stock of known cross-sectional
area, placing it inline with your hoist using clevis eyes or something
simple. You could read out, collect, and graph the load data as you test the
piece, but what for? Unless you wanted to optimize the design in order to whittle
the weight down to the bare minimum (like if you were building something
for a nonstop, unrefueled circumnavigation of the earth and were looking for
ounces here and there), close enough is good enough and a little bit extra is
better than not enough ;o)
--------
Oscar Zuniga
Medford, OR
Air Camper NX41CC "Scout"
A75 power, 72x36 Culver prop
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=477156#477156
Message 4
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Steve,
I much!!
--------
Semper Fi,
Terry Hand
Athens, GA
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=477166#477166
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