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PROPER DIMENSIONS OF MACHINES.






From: Flying Machines Construction Operation

In laying out plans for a flying machine the first thing
to decide upon is the size of the plane surfaces. The
proportions of these must be based upon the load to be
carried. This includes the total weight of the machine
and equipment, and also the operator. This will be a
rather difficult problem to figure out exactly, but
practical approximate figures may be reached.

It is easy to get at the weight of the operator, motor
and propeller, but the matter of determining, before they
are constructed, what the planes, rudders, auxiliaries,
etc., will weigh when completed is an intricate proposition.
The best way is to take the dimensions of some
successful machine and use them, making such alterations
in a minor way as you may desire.

Dimensions of Leading Machines.

In the following tables will be found the details as to
surface area, weight, power, etc., of the nine principal
types of flying machines which are now prominently before
the public:

MONOPLANES.
Surface area Spread in Depth in
Make Passengers sq. feet linear feet linear
feet
Santos-Dumont . . 1 110 16.0 26.0
Bleriot . . . . . 1 150.6 24.6 22.0
R. E. P . . . . . 1 215 34.1 28.9
Bleriot . . . . . 2 236 32.9 23.0
Antoinette. . . . 2 538 41.2 37.9
No. of Weight Without
Propeller
Make Cylinders Horse Power Operator
Diameter
Santos-Dumont. . 2 30 250 5.0
Bleriot. . . . . 3 25 680 6.9
R. E. P. . . . . 7 35 900 6.6
Bleriot. . . . . 7 50 1,240 8.1
Antoinette . . . 8 50 1,040 7.2

BIPLANES.
Surface Area Spread in Depth
in
Make Passengers sq. feet linear feet linear
feet
Curtiss . . . 2 258 29.0
28.7
Wright. . . . 2 538 41.0
30.7
Farman. . . . 2 430 32.9
39.6
Voisin. . . . 2 538 37.9
39.6

No. of Weight Without
Propeller
Make Cylinders Horse Power Operator
Diameter
Curtiss . . . 8 50 600 6.0
Wright. . . . 4 25 1,100 8.1
Farman. . . . 7 50 1,200 8.9
Voisin. . . . 8 50 1,200 6.6

In giving the depth dimensions the length over all--
from the extreme edge of the front auxiliary plane to
the extreme tip of the rear is stated. Thus while the
dimensions of the main planes of the Wright machine
are 41 feet spread by 6 1/2 feet in depth, the depth over
all is 30.7.

Figuring Out the Details.

With this data as a guide it should be comparatively
easy to decide upon the dimensions of the machine required.
In arriving at the maximum lifting capacity the
weight of the operator must be added. Assuming this
to average 170 pounds the method of procedure would be
as follows:

Add the weight of the operator to the weight of the
complete machine. The new Wright machine complete
weighs 900 pounds. This, plus 170, the weight of the
operator, gives a total of 1,070 pounds. There are 538
square feet of supporting surface, or practically one
square foot of surface area to each two pounds of load.

There are some machines, notably the Bleriot, in which
the supporting power is much greater. In this latter
instance we find a surface area of 150 1/2 square feet
carrying a load of 680 plus 170, or an aggregate of 850
pounds. This is the equivalent of five pounds to the
square foot. This ratio is phenomenally large, and
should not be taken as a guide by amateurs.

The Matter of Passengers.

These deductions are based on each machine carrying
one passenger, which is admittedly the limit at present
of the monoplanes like those operated for record-making
purposes by Santos-Dumont and Bleriot. The biplanes,
however, have a two-passenger capacity, and this adds
materially to the proportion of their weight-sustaining
power as compared with the surface area. In the following
statement all the machines are figured on the
one-passenger basis. Curtiss and Wright have carried
two passengers on numerous occasions, and an extra 170
pounds should therefore be added to the total weight
carried, which would materially increase the capacity.
Even with the two-passenger load the limit is by no
means reached, but as experiments have gone no further
it is impossible to make more accurate figures.

Average Proportions of Load.

It will be interesting, before proceeding to lay out the
dimension details, to make a comparison of the proportion
of load effect with the supporting surfaces of various
well-known machines. Here are the figures:

Santos-Dumont--A trifle under four pounds per square
foot.

Bleriot--Five pounds.

R. E. P.--Five pounds.

Antoinette--About two and one-quarter pounds.

Curtiss--About two and one-half pounds.

Wright--Two and one-quarter pounds.

Farman--A trifle over three pounds.

Voisin--A little under two and one-half pounds.

Importance of Engine Power.

While these figures are authentic, they are in a way
misleading, as the important factor of engine power
is not taken into consideration. Let us recall the fact
that it is the engine power which keeps the machine in
motion, and that it is only while in motion that the machine
will remain suspended in the air. Hence, to attribute the support
solely to the surface area is erroneous.
True, that once under headway the planes contribute
largely to the sustaining effect, and are absolutely essential
in aerial navigation--the motor could not rise without
them--still, when it comes to a question of weight-
sustaining power, we must also figure on the engine
capacity.

In the Wright machine, in which there is a lifting
capacity of approximately 2 1/4 pounds to the square foot
of surface area, an engine of only 25 horsepower is used.
In the Curtiss, which has a lifting capacity of 2 1/2
pounds per square foot, the engine is of 50 horsepower.
This is another of the peculiarities of aerial construction
and navigation. Here we have a gain of 1/4 pound in
weight-lifting capacity with an expenditure of double
the horsepower. It is this feature which enables Curtiss
to get along with a smaller surface area of supporting
planes at the expense of a big increase in engine power.
Proper Weight of Machine.

As a general proposition the most satisfactory machine
for amateur purposes will be found to be one with
a total weight-sustaining power of about 1,200 pounds.
Deducting 170 pounds as the weight of the operator,
this will leave 1,030 pounds for the complete motor-
equipped machine, and it should be easy to construct one
within this limit. This implies, of course, that due care
will be taken to eliminate all superfluous weight by using
the lightest material compatible with strength and safety.

This plan will admit of 686 pounds weight in the
frame work, coverings, etc., and 344 for the motor,
propeller, etc., which will be ample. Just how to distribute
the weight of the planes is a matter which must
be left to the ingenuity of the builder.

Comparison of Bird Power.

There is an interesting study in the accompanying
illustration. Note that the surface area of the albatross
is much smaller than that of the vulture, although the
wing spread is about the same. Despite this the albatross
accomplishes fully as much in the way of flight
and soaring as the vulture. Why? Because the albaboss is quicker
and more powerful in action. It is
the application of this same principle in flying machines
which enables those of great speed and power to get
along with less supporting surface than those of slower
movement.

Measurements of Curtiss Machine.

Some idea of framework proportion may be had from
the following description of the Curtiss machine. The
main planes have a spread (width) of 29 feet, and are
4 1/2 feet deep. The front double surface horizontal rudder
is 6x2 feet, with an area of 24 square feet. To the
rear of the main planes is a single surface horizontal
plane 6x2 feet, with an area of 12 square feet. In connection
with this is a vertical rudder 2 1/2 feet square.
Two movable ailerons, or balancing planes, are placed
at the extreme ends of the upper planes. These are 6x2
feet, and have a combined area of 24 square feet. There
is also a triangular shaped vertical steadying surface in
connection with the front rudder.

Thus we have a total of 195 square feet, but as the
official figures are 258, and the size of the triangular-
shaped steadying surface is unknown, we must take it
for granted that this makes up the difference. In the
matter of proportion the horizontal double-plane rudder
is about one-tenth the size of the main plane, counting
the surface area of only one plane, the vertical rudder
one-fortieth, and the ailerons one-twentieth.





Next: PLANE AND RUDDER CONTROL.

Previous: SELECTION OF THE MOTOR.



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