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LAA Schrenk Approximation

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imamac96

Well-Known Member
Joined
May 10, 2018
Messages
88
Location
North Texas / South Bay
Hi All,

I'm trying to learn a bit about Schrenk's approximation.
There's a great little document from the LAA on Schrenk Approximation (http://www.lightaircraftassociation.co.uk/2010/Engineering/Design/schrenk approximation.pdf), which I'm trying to emulate.
I've gotten consistent results with them so far, but I'm very stuck once I get to their section on Wing Root Reaction.
I should understand this stuff from Statics/MoM, but I can't quite figure out where they pull numbers from.

They say in the second to last paragraph on Page 11:
"Hence in this example case, the constant ultimate bending moment across the centre-section can be assumed to be 116596 lb in. The root shear reaction can be assumed to be (2575 - -731) = 3306 lb per side."

I have absolutely no idea where these (bolded) numbers are coming from. They're not listed anywhere else in the spreadsheet. There are no calculations for these described.
Is anyone familiar with this document? Would it be possible for anyone to describe this calculation?

I'm not sure if -731 is calculated or specified, but it is in the spreadsheet to represent the reaction at the wing root joint.
I have absolutely no clue where 2575 came from.

My work so far is here if you'd like to inspect: Schrenk

Thanks,
Connor
 
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