*Wilbur Wright to Octave Chanute*

*Dayton, July 12, 1903 *

Your letter of 8th inst. received and also copy of Flying which has interested
us on account of the portrait & sketch of Mr. Pilcher. Many thanks.

Regarding the matter of securing a publication of the Drzewiecki paper on screws
I am entirely unable to give any advice as I have no acquaintance with marine
publications or societies. Possibly the paper might interest some technical
school where marine engineering is a part of the course of study.

I am enclosing a table giving my idea of the performance of our 1902 machine
at various speeds. The column headed "Loss from Superposing" is the
one I am most dubious about. It shows the part of the angle of descent which
is due to superposing, in degrees. The table is based on observations on the
flight of the machine, studied in connection with our various tables of surfaces
which you have.1

The figures in last column are the sums of the figures in columns 4, 5, 6,
& 7. (The last being first turned into degrees.)

1 For an explanation of the way in which the wind tunnel data were used in
compiling this table, see the first paragraph of Wilbur Wright's letter to Chanute,
Aug. 31, 1903.

The calculations which follow may be the ones on which the Wrights based their
selection of the pressure coefficient 0.0033. This coefficient was used in conjunction
with the wind tunnel data to predict aerofoil and propeller performance and
the power requirements of the 1903 and later machines. See Appendix 11, D, Pressure
Coefficients and Scale Effect.

I Chanute computed these angles and inserted them in column 7 above their equivalents
in pounds. The angles, from top to bottom, are: 0 42', 0 56', 1 61, 1 20', 1
32', and 2 4'. This table and the following one, both relating to losses due
to superposing, form two undated entries in Wilbur Wright's Notebook J. They
are introduced here because it is likely that column 6 of the table enclosed
in Wilbur Wright's letter to Chanute of July 12, 1903, was based on the notebook
entries. The data in the second entry do not correspond to any of the data for
model aerofoils in the wind tunnel tables. The upper and lower surfaces may
refer to the wings of the 1902 glider; and the notebook entries, like the table
which accompanies the letter to Chanute of July 12, 1903, may have been "based
on observations on the flight of the machine, studied in connection with our
various tables of surfaces which you have."

*Octave Chanute to Wilbur Wright,
July 12, 1903*