#### imamac96

##### Active Member

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