I just finished the S-1S drawing. I had found the old Pitts drawing didn't really give you an accurate reference to the chord line. That Pitts drawing was for a tool to use on both the S-1 and S-2 airplanes. This new drawing is only for the S-1S and is based on the upper airfoil dimensions in the plans -- 1-441, Sht.1. Because the dimensions are fractional (1/32") the airfoil is pretty loosely defined. I used the spar dimensions to make sure the airfoil fit properly. I did the same with the lower wing airfoil but used published ordinates for the NACA 0012. I intend to check the fit of the lower wing airfoil on 1-441, Sht.1 to the spars and also compare it to the one I generated.
Because the rigging board touches the wing very close to the spars, small differences in airfoil shape do not change the reference to the chord line significantly. The CAD model is accurate to .001° when referencing to the chord and between upper and lower airfoils. The drawing I made is done mostly in fractions and will not be quite that accurate but still around .05° error given an accurate build. Certainly close enough for our purposes.
I will make other versions for common chord lengths probably starting with the Skybolt/Model 12. I'm not sure what the upper wing airfoil is for the Skybolt design but I assume it's a 63 series like the Model 12. The S-1S plans reference a 64 series but I was unable to get that airfoil to fit the spars or to agree with the dimensions in the plans.
Because the rigging board touches the wing very close to the spars, small differences in airfoil shape do not change the reference to the chord line significantly. The CAD model is accurate to .001° when referencing to the chord and between upper and lower airfoils. The drawing I made is done mostly in fractions and will not be quite that accurate but still around .05° error given an accurate build. Certainly close enough for our purposes.
I will make other versions for common chord lengths probably starting with the Skybolt/Model 12. I'm not sure what the upper wing airfoil is for the Skybolt design but I assume it's a 63 series like the Model 12. The S-1S plans reference a 64 series but I was unable to get that airfoil to fit the spars or to agree with the dimensions in the plans.
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