Sequoia Aircraft Corporation F.8L Falco, Construction Manual

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F.8L Falco Construction Manual 12–3 Revision 4, March 1, 2002
not always given at the face with the larger overall dimensions. For most of the fuselage frames in
the tail section, this is inconsequential, but if you wish, you may work out the larger dimensions
using trigonometry and a calculator. There are two frames where this discrepancy cannot be
ignored. Frame No. 8 is actually two frames, and the forward frame is the larger of the two. It is
best to make both in a female mold to the dimensions shown and then add an extra lamination to
the outside of the forward frame. It would be ideal if you could get the outside shape of frame No.
1 right on the money. This will make for a better fit with the cowling, and it will make the
already-tight front fuel tank installation no tighter.
The Fuselage Curve
The fuselage frames are curved. The curve is very similar to an ellipse, but it is not a true ellipse.
The curve has no name that we know of. The curve is sometimes called a “faired curve” since it
is frequently used in wing fairings, wing tips, etc. The curve is developed as shown on drawing
No. 301. Each side of the “box” is divided into a number of equal divisions. It does not matter
how many divisions you use except that for a given “box” you
must use the same number of
divisions on the horizontal side as you do on the vertical side. Failure to use the same number of
divisions will give you an incorrect curve. For most drawings, we find it easiest to use divisions of
ten or twenty. If there are more divisions it is easier to draw the curve with a flexible spline.
When all divisions have been marked off, connect the points with straight lines. The method of
connecting the points is also important. Refer to drawing No. 301. For the upper left quadrant,
you can label the marks on the horizontal line as “1”, “2”, “3”, “4” etc. from the inboard out.
Next, repeat the process on the side working down from the top.
Note: The centerline of the airplane and Water Line 0 are not used in connecting the
lines. It is possible to draw a curve using those points, but the curve will not be correct.
One builder has made this mistake, and he had to add wood to frame No. 1.
Next, connect point “1” on the top side with point “1” on the side, “2” with “2” and so on until
all of the points are connected. Use a spline and draw the curved line. The line should be
tangent to the segmented “curve” formed by the straight lines you have just drawn.
There is one additional method of drawing the curve. This method requires a programmable
calculator or a computer. To calculate the curve, three variables must be known. These variables
are shown in Figure 1.
Figure 1
The formula for this curve is:
1 −
x
A
+ 1 −
y
B
= 1