THE REAL FLYING MACHINE.

We will now assume that you have become proficient

enough to warrant an attempt at the construction of a

real flying machine--one that will not only remain suspended

in the air at the will of the operator, but make

respectable progress in whatever direction he may desire to go.

The glider, it must be remembered, is not

steerable, except to a limited extent, and moves only in

one direction--against the wind Besides this its power

of flotation--suspension in the air--is circumscribed.



Larger Surface Area Required.



The real flying machine is the glider enlarged, and

equipped with motor and propeller. The first thing to

do is to decide upon the size required. While a glider

of 20 foot spread is large enough to sustain a man it

could not under any possible conditions, be made to rise

with the weight of the motor, propeller and similar

equipment added. As the load is increased so must the

surface area of the planes be increased. Just what this

increase in surface area should be is problematical as

experienced aviators disagree, but as a general proposition

it may be placed at from three to four times the area of

a 20-foot glider.[3]



[3] See chapter XXV.



Some Practical Examples.



The Wrights used a biplane 41 feet in spread, and 6 1/2

ft. deep. This, for the two planes, gives a total surface

area of 538 square feet, inclusive of auxiliary planes.

This sustains the engine equipment, operator, etc., a total

weight officially announced at 1,070 pounds. It shows

a lifting capacity of about two pounds to the square

foot of plane surface, as against a lifting capacity of

about 1/2 pound per square foot of plane surface for the

20-foot glider. This same Wright machine is also reported

to have made a successful flight, carrying a total

load of 1,100 pounds, which would be over two pounds

for each square foot of surface area, which, with auxiliary

planes, is 538 square feet.



To attain the same results in a monoplane, the single

surface would have to be 60 feet in spread and 9 feet

deep. But, while this is the mathematical rule, Bleriot

has demonstrated that it does not always hold good.

On his record-breaking trip across the English channel,

July 25th, 1909, the Frenchman was carried in a

monoplane 24 1/2 feet in spread, and with a total sustaining

surface of 150 1/2 square feet. The total weight of

the outfit, including machine, operator and fuel sufficient

for a three-hour run, was only 660 pounds. With

an engine of (nominally) 25 horsepower the distance of

21 miles was covered in 37 minutes.



Which is the Best?



Right here an established mathematical quantity is

involved. A small plane surface offers less resistance

to the air than a large one and consequently can attain

a higher rate of speed. As explained further on in this

chapter speed is an important factor in the matter of

weight-sustaining capacity. A machine that travels one-

third faster than another can get along with one-half the

surface area of the latter without affecting the load. See

the closing paragraph of this chapter on this point. In

theory the construction is also the simplest, but this is

not always found to be so in practice. The designing

and carrying into execution of plans for an extensive

area like that of a monoplane involves great skill and

cleverness in getting a framework that will be strong

enough to furnish the requisite support without an undue excess

of weight. This proposition is greatly simplified

in the biplane and, while the speed attained by the latter

may not be quite so great as that of the monoplane, it

has much larger weight-carrying capacity.



Proper Sizes For Frame.



Allowing that the biplane form is selected the construction

may be practically identical with that of the

20-foot glider described in chapter V., except as to size

and elimination of the armpieces. In size the surface

planes should be about twice as large as those of the

20-foot glider, viz: 40 feet spread instead of 20, and 6 feet

deep instead of 3. The horizontal beams, struts, stanchions,

ribs, etc., should also be increased in size proportionately.



While care in the selection of clear, straight-grained

timber is important in the glider, it is still more important

in the construction of a motor-equipped flying

machine as the strain on the various parts will be much

greater.



How to Splice Timbers.



It is practically certain that you will have to resort to

splicing the horizontal beams as it will be difficult, if not

impossible, to find 40-foot pieces of timber totally free

from knots and worm holes, and of straight grain.



If splicing is necessary select two good 20-foot pieces,

3 inches wide and 1 1/2 inches thick, and one 10-foot long,

of the same thickness and width. Plane off the bottom

sides of the 10-foot strip, beginning about two feet back

from each end, and taper them so the strip will be about

3/4 inch thick at the extreme ends. Lay the two 20-foot

beams end to end, and under the joint thus made place

the 10-foot strip, with the planed-off ends downward.

The joint of the 20-foot pieces should be directly in the

center of the 10-foot piece. Bore ten holes (with a 1/4-

inch augur) equi-distant apart through the 20-foot

strips and the 10-foot strip under them. Through these

holes run 1/4-inch stove bolts with round, beveled heads.

In placing these bolts use washers top and bottom, one

between the head and the top beam, and the other between

the bottom beam and the screw nut which holds

the bolt. Screw the nuts down hard so as to bring the

two beams tightly together, and you will have a rigid

40-foot beam.



Splicing with Metal Sleeves.



An even better way of making a splice is by tonguing

and grooving the ends of the frame pieces and enclosing

them in a metal sleeve, but it requires more mechanical

skill than the method first named. The operation of

tonguing and grooving is especially delicate and calls

for extreme nicety of touch in the handling of tools, but

if this dexterity is possessed the job will be much more

satisfactory than one done with a third timber.



As the frame pieces are generally about 1 1/2 inch in

diameter, the tongue and the groove into which the

tongue fits must be correspondingly small. Begin by

sawing into one side of one of the frame pieces about 4

inches back from the end. Make the cut about 1/2 inch

deep. Then turn the piece over and duplicate the cut.

Next saw down from the end to these cuts. When the

sawed-out parts are removed you will have a "tongue"

in the end of the frame timber 4 inches long and 1/2 inch

thick. The next move is to saw out a 5/8-inch groove in

the end of the frame piece which is to be joined. You

will have to use a small chisel to remove the 5/8-inch bit.

This will leave a groove into which the tongue will fit

easily.



Joining the Two Pieces.



Take a thin metal sleeve--this is merely a hollow tube

of aluminum or brass open at each end--8 inches long,

and slip it over either the tongued or grooved end of one

of the frame timbers. It is well to have the sleeve fit

snugly, and this may necessitate a sand-papering of the

frame pieces so the sleeve will slip on.



Push the sleeve well back out of the way. Cover the

tongue thoroughly with glue, and also put some on the

inside of the groove. Use plenty of glue. Now press

the tongue into the groove, and keep the ends firmly

together until the glue is thoroughly dried. Rub off the

joint lightly with sand-paper to remove any of the glue

which may have oozed out, and slip the sleeve into place

over the joint. Tack the sleeve in position with small

copper tacks, and you will have an ideal splice.



The same operation is to be repeated on each of the

four frame pieces. Two 20-foot pieces joined in this

way will give a substantial frame, but when suitable

timber of this kind can not be had, three pieces, each 6

feet 11 inches long, may be used. This would give 20

feet 9 inches, of which 8 inches will be taken up in the

two joints, leaving the frame 20 feet 1 inch long.



Installation of Motor.



Next comes the installation of the motor. The kinds

and efficiency of the various types are described in the

following chapter (IX). All we are interested in at

this point is the manner of installation. This varies

according to the personal ideas of the aviator. Thus one

man puts his motor in the front of his machine, another

places it in the center, and still another finds the rear of

the frame the best. All get good results, the comparative

advantages of which it is difficult to estimate. Where

one man, as already explained, flies faster than another,

the one beaten from the speed standpoint has an advantage

in the matter of carrying weight, etc.



The ideas of various well-known aviators as to the

correct placing of motors may be had from the following:



Wrights--In rear of machine and to one side.



Curtiss--Well to rear, about midway between upper

and lower planes.



Raich--In rear, above the center.



Brauner-Smith--In exact center of machine.



Van Anden--In center.



Herring-Burgess--Directly behind operator.



Voisin--In rear, and on lower plane.



Bleriot--In front.



R. E. P.--In front.



The One Chief Object.



An even distribution of the load so as to assist in

maintaining the equilibrium of the machine, should be

the one chief object in deciding upon the location of the

motor. It matters little what particular spot is selected

so long as the weight does not tend to overbalance the

machine, or to "throw it off an even keel." It is just

like loading a vessel, an operation in which the expert

seeks to so distribute the weight of the cargo as to keep

the vessel in a perfectly upright position, and prevent a

"list" or leaning to one side. The more evenly the cargo

is distributed the more perfect will be the equilibrium of

the vessel and the better it can be handled. Sometimes,

when not properly stowed, the cargo shifts, and this at

once affects the position of the craft. When a ship

"lists" to starboard or port a preponderating weight of

the cargo has shifted sideways; if bow or stern is unduly

depressed it is a sure indication that the cargo has shifted

accordingly. In either event the handling of the craft

becomes not only difficult, but extremely hazardous.

Exactly the same conditions prevail in the handling of a

flying machine.



Shape of Machine a Factor.



In placing the motor you must be governed largely by

the shape and construction of the flying machine frame.

If the bulk of the weight of the machine and auxiliaries

is toward the rear, then the natural location for the motor

will be well to the front so as to counterbalance the

excess in rear weight. In the same way if the

preponderance of the weight is forward, then the motor

should be placed back of the center.



As the propeller blade is really an integral part of the

motor, the latter being useless without it, its placing

naturally depends upon the location selected for the

motor.



Rudders and Auxiliary Planes.



Here again there is great diversity of opinion among

aviators as to size, location and form. The striking

difference of ideas in this respect is well illustrated in

the choice made by prominent makers as follows:



Voisin--horizontal rudder, with two wing-like planes,

in front; box-like longitudinal stability plane in rear,

inside of which is a vertical rudder.



Wright--large biplane horizontal rudder in front at

considerable distance--about 10 feet--from the main

planes; vertical biplane rudder in rear; ends of upper

and lower main planes made flexible so they may be

moved.



Curtiss--horizontal biplane rudder, with vertical damping

plane between the rudder planes about 10 feet in

front of main planes; vertical rudder in rear; stabilizing

planes at each end of upper main plane.



Bleriot--V-shaped stabilizing fin, projecting from rear

of plane, with broad end outward; to the broad end of

this fin is hinged a vertical rudder; horizontal biplane

rudder, also in rear, under the fin.



These instances show forcefully the wide diversity of

opinion existing among experienced aviators as to the

best manner of placing the rudders and stabilizing, or

auxiliary planes, and make manifest how hopeless would

be the task of attempting to select any one form and

advise its exclusive use.



Rudder and Auxiliary Construction.



The material used in the construction of the rudders

and auxiliary planes is the same as that used in the main

planes--spruce for the framework and some kind of

rubberized or varnished cloth for the covering. The

frames are joined and wired in exactly the same manner

as the frames of the main planes, the purpose being to

secure the same strength and rigidity. Dimensions of

the various parts depend upon the plan adopted and the

size of the main plane.



No details as to exact dimensions of these rudders and

auxiliary planes are obtainable. The various builders,

while willing enough to supply data as to the general

measurements, weight, power, etc., of their machines,

appear to have overlooked the details of the auxiliary

parts, thinking, perhaps, that these were of no particular

import to the general public. In the Wright machine, the

rear horizontal and front vertical rudders may be set

down as being about one-quarter (probably a little less)

the size of the main supporting planes.



Arrangement of Alighting Gear.



Most modern machines are equipped with an alighting

gear, which not only serves to protect the machine and

aviator from shock or injury in touching the ground, but

also aids in getting under headway. All the leading

makes, with the exception of the Wright, are furnished

with a frame carrying from two to five pneumatic rubber-

tired bicycle wheels. In the Curtiss and Voisin

machines one wheel is placed in front and two in the

rear. In the Bleriot and other prominent machines the

reverse is the rule--two wheels in front and one in the

rear. Farman makes use of five wheels, one in the,

extreme rear, and four, arranged in pairs, a little to the

front of the center of the main lower plane.



In place of wheels the Wright machine is equipped

with a skid-like device consisting of two long beams

attached to the lower plane by stanchions and curving

up far in front, so as to act as supports to the horizontal

rudder.



Why Wood Is Favored.



A frequently asked question is: "Why is not aluminum,

or some similar metal, substituted for wood."

Wood, particularly spruce, is preferred because, weight

considered, it is much stronger than aluminum, and this

is the lightest of all metals. In this connection the following

table will be of interest:



Compressive

Weight Tensile Strength Strength

per cubic foot per sq. inch per sq. inch

Material in lbs. in lbs. in lbs.

Spruce . . . . 25 8,000 5,000

Aluminum 162 16,000 ......

Brass (sheet) 510 23,000 12,000

Steel (tool) 490 100,000 40,000

Copper (sheet) 548 30,000 40,000



As extreme lightness, combined with strength,

especially tensile strength, is the great essential in flying-

machine construction, it can be readily seen that the

use of metal, even aluminum, for the framework, is

prohibited by its weight. While aluminum has double the

strength of spruce wood it is vastly heavier, and thus

the advantage it has in strength is overbalanced many

times by its weight. The specific gravity of aluminum

is 2.50; that of spruce is only 0.403.



Things to Be Considered.



In laying out plans for a flying machine there are five

important points which should be settled upon before

the actual work of construction is started. These are:



First--Approximate weight of the machine when finished

and equipped.



Second--Area of the supporting surface required.



Third--Amount of power that will be necessary to

secure the desired speed and lifting capacity.



Fourth--Exact dimensions of the main framework

and of the auxiliary parts.



Fifth--Size, speed and character of the propeller.



In deciding upon these it will be well to take into

consideration the experience of expert aviators regarding

these features as given elsewhere. (See chapter X.)



Estimating the Weights Involved.



In fixing upon the probable approximate weight in

advance of construction much, of course, must be assumed.

This means that it will be a matter of advance

estimating. If a two-passenger machine is to be built

we will start by assuming the maximum combined

weight of the two people to be 350 pounds. Most of

the professional aviators are lighter than this. Taking

the medium between the weights of the Curtiss and

Wright machines we have a net average of 850 pounds

for the framework, motor, propeller, etc. This, with

the two passengers, amounts to 1,190 pounds. As the

machines quoted are in successful operation it will be

reasonable to assume that this will be a safe basis to

operate on.



What the Novice Must Avoid.



This does not mean, however, that it will be safe to

follow these weights exactly in construction, but that

they will serve merely as a basis to start from. Because

an expert can turn out a machine, thoroughly equipped,

of 850 pounds weight, it does not follow that a novice

can do the same thing. The expert's work is the result

of years of experience, and he has learned how to construct

frames and motor plants of the utmost lightness

and strength.



It will be safer for the novice to assume that he can

not duplicate the work of such men as Wright and Curtiss

without adding materially to the gross weight of

the framework and equipment minus passengers.



How to Distribute the Weight.



Let us take 1,030 pounds as the net weight of the machine

as against the same average in the Wright and

Curtiss machines. Now comes the question of distributing

this weight between the framework, motor, and

other equipment. As a general proposition the framework

should weigh about twice as much as the complete

power plant (this is for amateur work).



The word "framework" indicates not only the wooden

frames of the main planes, auxiliary planes, rudders,

etc., but the cloth coverings as well--everything in fact

except the engine and propeller.



On the basis named the framework would weigh 686

pounds, and the power plant 344. These figures are

liberal, and the results desired may be obtained well

within them as the novice will learn as he makes progress

in the work.



Figuring on Surface Area.



It was Prof. Langley who first brought into prominence

in connection with flying machine construction the

mathematical principle that the larger the object the

smaller may be the relative area of support. As explained

in chapter XIII, there are mechanical limits as

to size which it is not practical to exceed, but the main

principle remains in effect.



Take two aeroplanes of marked difference in area of

surface. The larger will, as a rule, sustain a greater

weight in relative proportion to its area than the smaller

one, and do the work with less relative horsepower. As

a general thing well-constructed machines will average

a supporting capacity of one pound for every one-half

square foot of surface area. Accepting this as a working

rule we find that to sustain a weight of 1,200 pounds

--machine and two passengers--we should have 600

square feet of surface.



Distributing the Surface Area.



The largest surfaces now in use are those of the

Wright, Voisin and Antoinette machines--538 square

feet in each. The actual sustaining power of these machines,

so far as known, has never been tested to the

limit; it is probable that the maximum is considerably

in excess of what they have been called upon to show.

In actual practice the average is a little over one pound

for each one-half square foot of surface area.



Allowing that 600 square feet of surface will be used,

the next question is how to distribute it to the best

advantage. This is another important matter in which

individual preference must rule. We have seen how

the professionals disagree on this point, some using

auxiliary planes of large size, and others depending upon

smaller auxiliaries with an increase in number so as to

secure on a different plan virtually the same amount of

surface.



In deciding upon this feature the best thing to do is

to follow the plans of some successful aviator, increasing

the area of the auxiliaries in proportion to the increase

in the area of the main planes. Thus, if you use 600

square feet of surface where the man whose plans you

are following uses 500, it is simply a matter of making

your planes one-fifth larger all around.



The Cost of Production.



Cost of production will be of interest to the amateur

who essays to construct a flying machine. Assuming

that the size decided upon is double that of the glider

the material for the framework, timber, cloth, wire, etc.,

will cost a little more than double. This is because it

must be heavier in proportion to the increased size of

the framework, and heavy material brings a larger price

than the lighter goods. If we allow $20 as the cost of

the glider material it will be safe to put down the cost

of that required for a real flying machine framework

at $60, provided the owner builds it himself.



As regards the cost of motor and similar equipment

it can only be said that this depends upon the selection

made. There are some reliable aviation motors which

may be had as low as $500, and there are others which

cost as much as $2,000.



Services of Expert Necessary.



No matter what kind of a motor may be selected the

services of an expert will be necessary in its proper

installation unless the amateur has considerable genius

in this line himself. As a general thing $25 should be

a liberal allowance for this work. No matter how carefully

the engine may be placed and connected it will be

largely a matter of luck if it is installed in exactly the

proper manner at the first attempt. The chances are

that several alterations, prompted by the results of trials,

will have to be made. If this is the case the expert's bill may

readily run up to $50. If the amateur is competent to do this

part of the work the entire item of $50 may, of course, be cut

out.



As a general proposition a fairly satisfactory flying machine,

one that will actually fly and carry the operator with it, may be

constructed for $750, but it will lack the better qualities which

mark the higher priced machines. This computation is made on

the basis of $60 for material, $50 for services of expert, $600

for motor, etc., and an allowance of $40 for extras.



No man who has the flying machine germ in his system will be long

satisfied with his first moderate price machine, no matter how

well it may work. It's the old story of the automobile "bug"

over again. The man who starts in with a modest $1,000 automobile

invariably progresses by easy stages to the $4,000 or $5,000

class. The natural tendency is to want the biggest and best

attainable within the financial reach of the owner.



It's exactly the same way with the flying machine

convert. The more proficient he becomes in the manipulation

of his car, the stronger becomes the desire to fly

further and stay in the air longer than the rest of his

brethren. This necessitates larger, more powerful, and

more expensive machines as the work of the germ progresses.



Speed Affects Weight Capacity.



Don't overlook the fact that the greater speed you

can attain the smaller will be the surface area you can

get along with. If a machine with 500 square feet of

sustaining surface, traveling at a speed of 40 miles an

hour, will carry a weight of 1,200 pounds, we can cut

the sustaining surface in half and get along with 250

square feet, provided a speed of 60 miles an hour can

be obtained. At 100 miles an hour only 80 square feet

of surface area would be required. In both instances the

weight sustaining capacity will remain the same as with

the 500 square feet of surface area--1,200 pounds.



One of these days some mathematical genius will

figure out this problem with exactitude and we will have

a dependable table giving the maximum carrying capacity

of various surface areas at various stated speeds,

based on the dimensions of the advancing edges. At

present it is largely a matter of guesswork so far as

making accurate computation goes. Much depends upon

the shape of the machine, and the amount of surface

offering resistance to the wind, etc.