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How To Build A 20-Foot Bi-Plane Glider 
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.. meta::
        :PG.Title: How To Build A 20-Foot Bi-Plane Glider
        :PG.Id: 63077
        :PG.Rights: Public Domain
        :PG.Producer: James Simmons
        :PG.Credits: This file was produced from page images at the Internet Archive.
        :DC.Creator: Alfred Powell Morgan
        :DC.Title: How To Build A 20-Foot Bi-Plane Glider
        :DC.Language: en
        :DC.Created: 1909
        :PG.Released: 2020-08-29
        :coverpage: images/CoverImage.jpg

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.. topic:: Transcriber's Note

    This book was transcribed from scans of the original found at the Internet Archive. 
    I have rotated some images. Tables are treated as images. The back of the book 
    contains ads for other books, which I have treated as additional chapters.

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       HOW TO BUILD A 20-FOOT 

       **BI-PLANE GLIDER**

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       *A Practical Handbook on the Construction of a Bi-plane*
       
       *Gliding Machine, Enabling an Intelligent Reader*
      
       *to Make His First Step in the Field of Aviation;*
       
       *With a Comprehensive*
       
       *Understanding of the Principles Involved.*

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       BY
 
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       ALFRED POWELL MORGAN 

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       *Editor Mechanical and Electrical Department of the*
       
       *“Boy's Magazine.”*

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       NEW EDITION, REVISED 

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       NEW YORK 

       SPON & CHAMBERLAIN, 123 LIBERTY ST. 

       LONDON 

       **E. & F. N. SPON, LIMITED, 57 HAYMARKET, S.W.**

       1912 

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    Copyright, 1909, by 

    Spon & Chamberlain. 

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HOW TO BUILD A 20-FOOT BI-PLANE GLIDER 
--------------------------------------

PREFACE
``````` 

Gliding flight is a comparatively new field for 
the amateur to delve in, but the time has arrived 
when it is being extensively taken up both as a 
sport and a means of experiment. 

Many very costly aeroplanes have failed to fly 
because of man’s total inexperience in the art of 
flying. All of the great aviators now before the 
world, whose machines are the result of their 
own genius *learned to fly* before succeeding in a 
motor driven machine. 

The Wright brothers spent no less than three 
years on the sand dunes near the coast of North 
Carolina making gliding flights. They approached 
the difficulties in a methodical manner, working 
out each problem and determining which was the 
best means of accomplishing a certain result. 

To control the tendency to pitching, they 
devised an elevation rudder and attached it to the 
front of their machine. The next step was to 
determine whether equilibrium should be 
maintained by shifting the centre of gravity or if there 
was not a better method and they introduced what 
is probably the most valuable feature of the 
modern aeroplane, namely the warping or twisting 
of the ends of the planes to secure lateral stability 
when a gust of wind strikes one end of the machine. 

In this manner the Wright’s continued their 
experiments until every move had become a 
matter of habit and to balance and guide an 
aeroplane was almost an instinct. 

A gasoline engine was then fastened in the 
machine and connected to drive two screw propellers 
at the rear. Dec. 17, 1903 the machine flew for a 
few seconds. 

The leaps and bounds with which aviation has 
since progressed both in the hands of the Wrights 
and others is a matter too well known to be 
repeated. 

There is therefore no excuse necessary to be 
made for this little book, coming as it does at this 
time and it is sincerely hoped that it may interest 
and lead many to experiment first and build their 
aeroplane afterward so that when their machine 
is complete it may be practical and not intended 
to operate in some "lift-yourself-by-your-boot-straps" manner. 

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CHAPTER I. The Framework.
`````````````````````````

**A gliding machine**, more often popularly termed 
a glider, is simply a motorless aeroplane, operating 
by force of gravity to carry its passenger sailing 
through the air from the top to the foot of a slope. 

**The glider** described herein is the type developed 
by Octave Chanute and may be considered as the 
parent of the biplane machines with which the world 
has lately become so familiar. The machine is 
known as a biplane since its supporting surface 
is in the form of two superimposed trussed planes 
vertically above each other and having a tail in 
the rear for the control of direction. 

There is always a tendency among experimenters 
to depart from the design and dimensions of any 
machine or apparatus offered for construction. 
This, since it develops originality is a good 
indication, but most of those who will undertake to build 
a glider are attempting something altogether new 
and so any radical change from the instructions 
in this little booklet are unadvisable. 

It is better at first to benefit by the experience 
of others. The glider here described is considered 
as the "standard" of the biplane type. It has 
an active supporting surface of 152 square feet 
which is sufficient to carry the weight of an ordinary 
man. A machine having a larger surface will 
support the same weight when moving through the 
air at a slower speed, but larger surface means an 
increase in some of the general dimensions. An 
increase in surface by lengthening the planes will 
make the machine much harder to keep on an even 
keel, while increasing their depth in the direction 
of flight will require greater agility on the part of 
the operator to keep the centre of gravity in the 
proper position. A larger machine also means 
more weight and a heavy machine is hard to make 
a landing with. 

On the other hand a light glider is dangerous and 
will not stand any rough usage. 

**The cost of the glider**, provided the construction 
is accomplished by the intending owner is so low 
as to place it within the reach of any person of 
ordinary means. The expenditure for raw 
materials varies greatly. It is usually a little less than 
$20.00 and should not exceed $35.00. A finished 
glider is worth from $50.00 to $100.00 depending 
whether or not more than one is made at a time. 

**Housing.** One of the first considerations is 
usually the housing and storing of the glider, but 
the machine under consideration is so designed that 
it may be quickly taken apart or "knocked down" 
and be put away in the cellar, under the porch or 
in some other out of the way place. 

**The framework** is composed entirely of selected 
spruce, straight grained and free from knots. 
Spruce is very dense and tough but yet one of the 
lightest of woods. 

**The dimensions** given are for the finished pieces 
after they have been planed up. The usual method 
of finishing wood for aeronautical work, so that 
it has a hard glassy surface and offers little 
resistance to the air is first to give it a thorough 
brushing over with hot glue and water. It is 
rubbed down after drying, using fine sand paper. 
The wood is then given a coat of thin shellac. 

This is rather a tedious operation and instead 
some may prefer to first smooth up the wood by 
sand papering and giving it a coat of spar varnish. 

The corners of all the woodwork are rounded off 
so as to reduce the resistance offered to the air. 

**Horizontal beams**. The principal members of 
the planes when smoothed up should measure 
20 feet long, 1 1/2 inches wide and 3/4 inches thick. 
Four of these beams are required. In some lumber 
yards, twenty foot spruce free from knots is very 
hard to secure and so instead, two 10 foot pieces 
may be spliced together at the centre as shown in 
Fig. 1. 

The splicing strip is 5 feet long and has the same 
cross section as the beams, save for a distance of 
one foot from each end where it begins to taper 
down to 1/4 inch thick. Six holes are bored through 
the splicing strip and the beams so that they may 
be fastened together by means of six 3/16 inch 
round headed stove bolts. The holes are located 
so that the space between the two centre bolts is 
six inches while the others are located one foot apart. 

A large washer having a small hole in the centre 
is placed under the head of each bolt as well as 
the nut. 

.. figure:: images/Image1.jpg
   :scale: 85 %
   :alt: Fig. 1 Horizontal Beam

   Fig. 1 Horizontal Beam

**Struts.** Each pair of horizontal beams are held 
parallel to each other and three feet apart by six 
horizontal struts. The form of these struts is 
illustrated in Fig. 2. 

They are three feet long and 1/2 x 1 1/4 inches in 
cross section. A notch 1 1/2 x 3/4 inches is cut in 
each end so as, to form a projection 1 1/2 x 1/2 x 1/2
inches. 

The location of the struts in the plane is 
illustrated in Fig. 3. The two in the centre are two 
feet apart and the others respectively 4 feet 
6 inches and 9 feet on either side. The struts 
on the upper plane are placed so that the 
projections come above the horizontal members. 
Those on the lower plane are placed just the 
opposite, that is so that they come on the under 
side. 

.. figure:: images/Image2.jpg
   :scale: 85 %
   :alt: Fig. 2.—Strut. 

   Fig. 2.—Strut. 

They are fastened with one or two small wire 
nails and then secured by means of a clamp. 
Two dozen clamps are required. They are bent 
out of a strip of sheet brass one sixteenth of an 
inch thick, 3 7/8 inches long and 1 inch wide. The 
ends are rounded and a 1/4 inch hole located and 
bored in each as in Fig. 4. 

.. figure:: images/Image3.jpg
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   :alt: Fig. 3.—Position of Struts.

   Fig. 3.—Position of Struts.

The clamp also serves to protect the under side 
of the beam from the action of the nuts on the ends 
of the eyebolts. The method of fastening the 
clamp is detailed a little later. 

.. figure:: images/Image4a.jpg
   :scale: 85 %
   :alt: Fig. 4.—Strut clamp.

   Fig. 4.—Strut clamp.

**Stanchions**. The planes are separated by twelve 
stanchions, four feet long and 7/8 of an inch in 
diameter. 

.. figure:: images/Image4b.jpg
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   :alt: Fig. 5.—Stanchion. 

   Fig. 5.—Stanchion. 

They are rounded and smoothed up so that the 
ends will fit snugly into the socket illustrated in 
Fig. 6. These sockets may be purchased [#]_ already 
bored and finished or can be procured at a foundry. 
They are preferably made of aluminum which 
metal is at once light and strong but brass or even 
iron may be used if it is necessary to avoid expense. 

.. figure:: images/Image5.jpg
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   :alt: Fig. 6.—Stanchion socket.

   Fig. 6.—Stanchion socket.

There are other methods of joining the stanchions 
to the beams but the use of the socket is 
recommended because it is the strongest method and 
also permits the glider to be readily taken apart. 

The base of the socket is 3 1/4 inches long, 1 1/4 inches 
wide and 1/4 of an inch thick. The cup has an 
internal diameter of seven eighths of an inch and 
an outside diameter of one inch and one quarter. 
It is one inch high above the base. Two 1/4 inch 
holes are bored 1 7/8 inches apart in the base. Two 
smaller holes 1/8 inch in diameter are bored 7/16 inch 
nearer the ends of the base than the larger holes. 

**The wooden pattern** is made from the dimensions 
indicated in Fig. 6. It is thoroughly smoothed up 
by rubbing with sand paper and then given a coat 
of shellac. All parts should have a very slight 
taper towards the top so that the pattern may be 
withdrawn easily from the sand mould. 

.. figure:: images/Image6.jpg
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   :alt: Fig. 7.—Eyebolt. 

   Fig. 7.—Eyebolt. 

If the interior of the mould is coated with 
lamp-black, the castings will require no other finishing 
than boring the holes. 

Two dozen of these sockets are required. Six 
are fastened to each of the four horizontal members 
by means of round headed wood screws which pass 
through the smaller holes in the base. The 
sockets are located exactly opposite the ends of 
each strut so that when the stanchions are in 
place, they will be separated by the same distances 
but all lie in a plane at right angles to that in 
which the struts are. 

A 1/4 inch hole is bored through the horizontal 
beam directly under each one of the 1/4 inch holes 
in the base of the socket. These holes permit an 
eyebolt to pass through. The eye bolt is illustrated 
in Fig. 7. The stock is 1/4 inch in diameter and 
should be at least two inches long under the eye. 

.. figure:: images/Image7.jpg
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   :alt: Fig. 8.—Assembly of stanchion, socket beam, strut and clamp. 

   Fig. 8.—Assembly of stanchion, socket beam, strut and clamp. 

The diameter of the eye is one half an inch. 
These eye bolts are obtainable already threaded 
and ready for use with a nut and washers, but can 
be procured somewhat cheaper in blank form and 
threaded by the purchaser. Four dozen are 
necessary, two for each socket. The eye bolts 
pass through the socket and beam, coming out on 
the under side directly opposite the holes in the 
strut clamp. A nut placed on the under side as 
in Fig. 8 will then hold the clamp tightly against 
the under side of the beam and secure the position 
of the strut. 

**Ribs.** Forty one ribs support the cloth forming 
the surfaces. They are each one half an inch 
square in cross section and four feet long. 

.. figure:: images/Image8.jpg
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   :alt: Fig. 9.—Rib. 

   Fig. 9.—Rib. 

They are fastened to the horizontal members 
one foot apart, flush with the front and projecting 
one foot in the rear. One or two small wire nails 
are used to fasten the front ends and then a clamp 
placed over them and screwed down with two No. 5 
round headed wood screws, one half an inch long. 
A small brad awl should be used to make a hole 
before starting the screw and so avoid any 
possibility of starting a split in the wood. 

The clamps are bent out of sheet copper strips, 
2 1/4 inches long and 5/8 of an inch wide. The ends are 
rounded and a hole bored through which the screws 
may pass. 

The surfaces of the planes are curved to give 
them an increased carrying capacity and add to 
the gliding power. 

.. figure:: images/Image9.jpg
   :scale: 85 %
   :alt: Fig. 10.—Rib clamp. 

   Fig. 10.—Rib clamp. 

The best method is to steam the ribs and then 
bend them so that when they dry they will retain 
their curve and not tend to push the horizontal 
beams apart. Only a very slight curve should be 
given and the amount of curvature should be the 
same for all the ribs. 

Some designers construct gliders having flat 
planes, intending that the pressure of the air 
underneath the fabric shall produce a natural curve 
but such a method is exceedingly poor practice 
and results in a very inefficient machine. 

The ribs must be perfectly rigid and the frame 
of the whole machine strongly trussed so that it 
cannot possibly be distorted by the air pressure. 
The following extract from the report of the 
Smithsonian Institute well illustrates this point. 

"This new launching piece did its work 
effectively and subsequent disaster was, at any rate, 
not due to it. But now a new series of failures 
took place, which could not be attributed to any 
defect of the launching apparatus, but to a cause 
which was at first obscure; for sometimes the 
aerodrome, when successfully launched would dash 
down forward and into the water, and sometimes 
(under apparently identical conditions) would 
sweep almost vertically upward into the air, and 
fall back although the circumstances of flight 
seemed to be the same. The cause of this class of 
failures was finally found in the fact that as soon 
as the whole machine was up-borne by the air, 
the wings yielded under the pressure which 
supported them, and were momentarily distorted from 
the form designed and which they appeared to 
possess. "Momentarily," but enough to cause the 
wind to catch the top, directing the flight 
downward, or under them, directing the flight upward, 
and to wreck the experiment. When the cause of 
the difficulty was found the cure was not easy, 
for it was necessary to make this great *sustaining 
surfaces rigid*, so that they could not bend.” 

The report in question refers to the experiments 
conducted with Professor Langely’s model 
aerodrome. 

Some experimenters claim that the parabolic 
curve gives the greatest lift with the least power 
required for propulsion but it can be safely doubted. 
The Wright machine is probably the most efficient 
in existence. Their curve is very nearly the arc 
of a circle and is not of the parabolic form. 

Four per cent is about the proper curve to give 
the planes of a glider. This is about two inches for 
ribs four feet long. After fastening the front end 
of the ribs, curve them up in the centre by pressing 
down on the loose and at the rear. Then nail the 
rib to the rear beam with a small wire brad and 
screw on the clamp. The nails prevent the ribs 
from slipping longitudinally while the clamps serve 
to prevent them from moving sideways or pulling 
off when the fabric is under the pressure of the air. 

Fig. 11 is a plan view of the top and bottom 
planes. Twenty one ribs, each one foot apart 
are used on the upper plane. Only twenty ribs 
are required on the bottom surface because an 
opening two feet wide must be left in the centre 
for the body of the operator. 

**Arm pieces.** The operator is supported in the 
machine by two strips of wood passing under his 
armpits. These armpieces are 3 feet long, 1 inch 
wide and 1 3/4 inches deep. 

.. figure:: images/Image10.jpg
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   :alt: Fig. 11.—Plan View of Planes showing Ribs.

   Fig. 11.—Plan View of Planes showing Ribs.

They are fastened to the horizontal beams by 
means of a 3/16 inch round headed stove bolt. The 
distance between should be just wide enough to 
be comfortable and is variable with the breadth 
of the operator between his shoulders. Thirteen 
inches is about the proper distance for the average 
person. The upper side of the arm pieces is 
rounded so that they will not be quite so 
uncomfortable as they would be if left square. It is 
not a good plan to pad these pieces by wrapping 
them with cloth for it will impede the movements 
of the body in balancing. 

.. figure:: images/Image11.jpg
   :scale: 85 %
   :alt: Fig. 12.—Arm piece.

   Fig. 12.—Arm piece. 

**Rudder.** The rudder is composed of two planes 
at right angles to each other and in the rear of 
the main surfaces. The vertical portion keeps the 
machine headed into the wind and causes it to 
glide in the direction in which it is started or head 
on into the wind. The horizontal rudder steadies 
the machine longitudinally and prevents the 
machine from suddenly diving or pitching. Neither 
of the rudder planes are movable. 

The separate parts composing the framework 
are illustrated in Fig. 13. 

.. figure:: images/Image12.jpg
   :scale: 85 %
   :alt: Fig. 13.—Parts of rudder framework.

   Fig. 13.—Parts of rudder framework.

The cross section of all the sticks is the same, 
namely one inch square. The two long beams, 
*A*, are 8 feet 11 inches long. The two uprights, *B*, 
each 3 feet 10 inches long from the vertical members 
of the directional plane. The horizontal plane 
is made up of six horizontal strips, two of them, *C*, 
six feet long and four, *D*, two feet in length. 

**The horizontal plane** is fitted together with half 
and half lap joints. It is first fastened with nails 
and then reinforced with brass corner braces. 

.. figure:: images/Image13a.jpg
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   :alt: Fig. 14.—Corners of horizontal rudder plane. 

   Fig. 14.—Corners of horizontal rudder plane. 

Corner braces are also used to strengthen the 
vertical plane. 

.. figure:: images/Image13b.jpg
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   :alt: Fig. 15.—Complete framework of rudder.

   Fig. 15.—Complete framework of rudder.

**The rudder beams** are stepped into sockets on 
the body of the machine so that the rudder is 
detachable. 

**A short cross bar** 2 feet inches long and 1 1/4
x 3/4 inches in cross section, is fastened between 
the two centre struts of both planes at a point 
eight inches forward of the rear beams. 

These cross bars carry one of the sockets 
mentioned above as also do the rear horizontal beams. 
The cross bar and sockets in the upper plane should 
be directly over those in the lower plane but in an 
inverted position. 

.. figure:: images/Image14.jpg
   :scale: 85 %
   :alt: Fig. 16.—Cross bar. 

   Fig. 16.—Cross bar. 

**The construction of the sockets** is illustrated in 
Fig. 17. The smaller one is fastened to the cross 
bar and is bent out of a strip of 1/16 inch sheet 
brass 4 1/2 inches long and 3/4 of an inch wide. The 
larger socket is the same length and thickness but 
is 1 1/4 inches wide and is fastened to the horizontal 
beam. Two of each size are required. The ends 
are rounded and a 3/16 inch hole bored in each so that 
a 3/16 inch round headed stove bolt may be used 
to fasten the sockets to the framework. 

.. figure:: images/Image15.jpg
   :scale: 85 %
   :alt: Fig. 17.—Rudder Sockets, or Clamps.

   Fig. 17.—Rudder Sockets, or Clamps.

.. figure:: images/Image16.jpg
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   :alt: Fig. 18.—Arrangement of Armpieces and Rudder Cross Bar.

   Fig. 18.—Arrangement of Armpieces and Rudder Cross Bar.

.. figure:: images/Image17.jpg
   :scale: 85 %
   :alt: Fig. 19.—Complete Framework Ribs on Lower Plane Not Shown

   Fig. 19.—Complete Framework Ribs on Lower Plane Not Shown

A hole is bored in the centre of the top of the 
smaller sockets so that a bolt may be passed through 
the rudder beam and cross bar to prevent the 
former from pulling out. 

The two sockets in each plane must be in perfect 
alignment and lie on a line drawn at right angles 
to the horizontal members through the centre of 
the planes. 

In Fig. 15 it will be noticed that four bolts pass 
through each plane near the corners. The bolts 
are 3/16 inches in diameter and serve to fasten the 
piano wires which brace the vertical and horizontal 
plane to each other. 

The complete framework of the glider without 
the tie wires and the ribs on the lower plane will 
appear as in Fig. 19. 

.. figure:: images/Image18.jpg
   :scale: 85 %
   :alt: Parabolic Curve for a 4 ft. Plane 

.. [#] From Spon & Chamberlain 

CHAPTER II. Covering the Planes.
````````````````````````````````

The surfaces of a motor driven aeroplane are 
usually made of some material which is practically 
air tight. The Herring-Curtiss Co., use Baldwin’s 
rubberized silk, while most of the foreign aviators 
prefer a balloon cloth known under the name of 
"continental." 

Ordinarily the surfaces of a glider are not covered 
with any preparation to make them air tight and 
is not necessary, but since it will considerably 
increase their efficiency it is offered as a suggestion 
to those who are able or care to undergo the 
expense. 

**Aero varnishes** for this purpose are obtainable 
in the market and may be applied with an ordinary 
brush or by immersing the fabric. One gallon 
will cover approximately 100 square feet of 
ordinary Cambric, although much depends upon 
the weave. The more open or coarser the goods, 
the more varnish it will require, while fine fabrics 
take the least amount. 

Varnish is expensive and is not considered in 
the estimate of cost made at the beginning of the 
book. 

**The surfaces** are formed of cambric or muslin 
stretched tightly over the ribs. Thirty yards of 
material, one yard wide will be sufficient to cover 
the machine, including the rudders. 

Seven strips 4 feet 6 1/2 inches long are cut and 
sewed together along the selvages so that a surface 
4 feet 6 1/2 inches wide and a little over 20 feet long 
is formed. Twenty one strips, 4 feet 6 1/2 inches 
long and 1 1/2 inches wide are cut and sewed to the 
surface at right angles to the long edges and one 
foot apart, between their centre lines. The edges 
of these strips are turned under 1/4 of an inch on 
each side so that they form a reinforcement 1 inch 
wide which will come directly above each rib. 

.. figure:: images/Image19.jpg
   :scale: 85 %
   :alt: Fig. 20.—Method of hemming up edge of cloth. 
   
   Fig. 20.—Method of hemming up edge of cloth. 

**Reinforcing.** The long edges of the surface are 
then doubled back and hemmed, turning under 1/4 
of an inch and forming a 3 inch hem as illustrated 
in the upper part of Fig. 20. This 3 inch hem is 
then doubled back one inch and sewed again so 
that the result is a two inch hem, composed of 
two thicknesses of cloth save for one inch back from 
the edge where it is made up of four thicknesses. 

This reinforcing is necessary to avoid ripping 
and tearing the cloth out from under the tack 
heads when it is under pressure during a flight. 

.. figure:: images/Image20.jpg
   :scale: 85 %
   :alt: Fig. 21.—Section of cloth hemmed, and reinforcing strips sewn on. 
   
   Fig. 21.—Section of cloth hemmed, and reinforcing strips sewn on. 

**The bottom planes.** The cloth on the bottom 
planes is made up of two sections, divided by the 
space in the centre of the lower plane which the 
operator occupies. These sections are made and 
reinforced in exactly the same manner as that for 
the top plane just described but are one foot less 
than half as long. 

**The cloth is tacked** over the front horizontal 
beam and then stretched tightly over the curved 
ribs and fastened with tacks at the ends. Fasten 
the corners of the cloth first and smooth it out 
before driving the tacks in the ribs. Ordinary 
brass headed upholsterer’s nails are used but they 
should not be long enough to pass all the way 
through the ribs. 

A strip of felt 3/8 of an inch wide and four feet 
long is laid on the cloth directly over each rib so 
that it comes between the head of the tack and 
the cloth. This precaution may seem unnecessary 
to some, but it greatly reduces the liability of 
having the cloth tear when under pressure. The 
tacks along the ribs are spaced about 4 inches apart 
A heavy weight held against the under side of 
the rib by an assistant, when the tacks are driven 
in will provide a firm foundation to hammer 
against. 

A very good method of fastening the cloth to 
the ribs is to sew a pocket on the under side of 
the surface and into which the ribs may be 
slipped. 

The rear ends of the ribs may be fitted with 
metal tips by tapering the end down until it is 
round and measures 1/2 inch in diameter. A 
1/2 inch brass ferrule such as that used on file handles 
is then forced on. 

**The rudder planes** are covered on both sides. 
The fabric is stretched tightly over the frame and 
then tacked along the edges. The edges should 
be turned under before tacking so that there is 
no possibility of the cloth tearing out. 

The cloth at the ends of the planes should be 
securely fastened to the struts by means of tacks. 
This will relieve the ribs of some of the strain and 
correct a tendency for them to pull in towards the 
centre. 

CHAPTER III. Trussing.
``````````````````````

The strength of the glider lies in its proper 
trussing with piano wires which when tightened 
up should so brace the framework that it will 
support without appreciable sag or strain, a heavy 
man hanging from the arm pieces and the ends of 
the planes resting on a pair of carpenters’ horses. 

Two methods of trussing the planes are 
illustrated in Fig. 22. The machine is divided into 
five cells the vertical boundaries of which are 
formed by the stanchions. . 

**The first method** illustrated is the one used in 
this case for the glider. It is somewhat simpler 
than the second and does not require the use of 
any turnbuckles. 

Each wire is fastened to one of the eyebolts on 
the horizontal beams and then run diagonally across 
to the socket on the opposite beam in the other 
plane, considering front and rear to be opposed. 

Four of these diagonal wires, represented by 
*J* in Fig. 23 brace each of the four large cells. 
The middle cell cannot be trussed up in this manner 
because the wires would interfere with the body 
of the operator. So the rectangles formed by 
the two centre struts with the upper horizontal 
beams and the two centre rear stanchions with the 
rear horizontal beams of the upper and lower 
planes, are braced by means of wires running 
across their diagonals. 

.. figure:: images/Image21.jpg
   :scale: 85 %
   :alt: Fig. 22.—Trussing Of Cells.
   
   Fig. 22.—Trussing Of Cells.

**The rudder** is stiffened and trussed to the planes 
by sixteen wires. Two of these *F* and *H* run from 
the top of the vertical rudder plane to the lower 
sockets in the rear, 4 1/2 feet from the ends of the
planes. The corresponding pair *E* and *G* run 
from the bottom of the rudder to the top sockets 
of the same stanchions. Four wires *A*, *B*, *C*, *D* 
steady the horizontal plane and run from its corners
to the sockets in which the rudder beams are 
stepped on the frame of the glider itself. The 
remaining eight, indicated by *I* in the illustration 
brace the horizontal and vertical planes of the 
rudder to each other. 

Fig. 24 illustrates the method of anchoring 
piano wires.

The wire is first passed through a short piece 
of 1/8 inch copper tubing about 3/8 of an inch long,
then through the eyebolt. The end is doubled 
back passed through the tube again but now in a 
reverse direction. By bending the extreme end 
of the wire over in the form of a hook and shoving 
the tube down close to the eye bolt, the wire is 
secured and cannot pull out. The other end of the
wire is fastened in the same manner but before the
end is bent over into a hook, the wire must be
first pulled tight.

.. figure:: images/Image22.jpg
   :scale: 85 %
   :alt: Fig. 23.—Plan and Elevation Views of Piano Wire Bracing.
   
   Fig. 23.—Plan and Elevation Views of Piano Wire Bracing.

After fastening all of the wires their tension may 
be regulated by turning the nuts on the lower ends 
of the eye bolts. It is very necessary that the 
frame should be perfectly true and not warped 
or twisted. Otherwise the machine will be very 
hard to balance and manage when making a glide. 
Especially must the rudder be true with the rest 
of the machine. 

.. figure:: images/Image23.jpg
   :scale: 85 %
   :alt: Fig. 24.—Method of anchoring wires
   
   Fig. 24.—Method of anchoring wires

Since there are no eyebolts about the rudder 
which could be used to tighten or loosen the 
truss wires, a turnbuckle must be included in 
each wire for that purpose. 

**Turnbuckles.** The construction of these 
turnbuckles which are very simple and inexpensive is 
illustrated in Fig. 25. They are made of a bicycle 
spoke and nipple by cutting off one end of the 
spoke and using the part which is threaded. The 
end of this piece is bent back and twisted into an 
eye. A piece of 1/16 inch sheet brass 1/2 x 3/8 inch has 
a hole bored in its centre, the diameter of which is 
such that it will just admit the spoke nipple. 
The nipple is prevented from passing all the way 
through by the shoulder on one end. A piece of 
sheet iron 1/2 inch wide and 3 inches long has a 
similar hole bored in its centre. The ends of this 
strap are rounded and bored so that the piano 
wire may be passed through. The turnbuckle 
is then assembled and connected as shown in the 
illustration. The tension of the wire is regulated 
by turning the spoke nipple while the spoke 
itself is held rigid.
 
.. figure:: images/Image24.jpg
   :scale: 85 %
   :alt: Fig. 25.—Bicycle spoke turnbuckle. 
   
   Fig. 25.—Bicycle spoke turnbuckle. 

**The second method** of bracing illustrated in 
Fig. 22 requires that a turnbuckle be included in 
the diagonals of every rectangle, except those 
formed by the stanchions with the horizontal 
beams. This method is used on almost all 
aeroplanes and is considered the strongest but the first 
method is plenty strong enough for an ordinary 
glider. If after trussing, the machine is found 
to be warped or twisted, it must be trued up. 
By sighting along the horizontal beams and 
tightening or loosening the necessary wire any curvature 
may be easily corrected. 

**The second method** of trussing is considerably 
harder to true up than the first, since when one 
diagonal of a rectangle is tightened, the other must 
be loosened. But since it makes an exceedingly 
firm and rigid structure, it may be well 
recommended to those who care to undergo the added 
expense and labor involved by the extra 
turnbuckles and wires. 

**To take the glider apart**, first remove the bolts 
holding the rudder beams in the sockets on the 
machine. Then unfasten the wires which brace 
the rudder to the machine by loosening the 
turnbuckles until the spokes and nipples unscrew and 
come apart. The rudder may now be removed 
from the machine. 

Next take off all the nuts on the eye bolts in 
the lower plane and pull the eyebolts out of the 
sockets. The two planes will then come apart. 
Remove the stanchions by pulling them out of the 
sockets. The two planes are then laid one on 
top of the other and will occupy very little room. 

CHAPTER IV. Gliding.
````````````````````

The first words which may well be said upon 
this subject are to emphasize caution. But by 
this I do not wish to imply that gliding is 
exceedingly dangerous. Neither do I by caution mean 
timidity but rather judgment and common sense. 

Canoeing is generally considered a safe sport, 
but who would think of canoeing on the ocean 
in a storm. It is exactly the same extreme to 
glide from a very high object, or experiment in a 
high wind. 

**The atmosphere** near the earth is a mass of 
whirling and swirling currents which are 
constantly rising and falling and become very 
pronounced in a high wind. Even in a comparative 
calm these eddy currents exist but of course not 
to a dangerous degree. Evidence of this may be 
seen by watching the little dust particles floating 
in the air and made visible by a sunbeam coming 
through the window of a quiet room. Although 
the sense of feeling cannot detect the smallest 
air current, these little particles are whirling 
around and constantly changing their direction. 

When the wind strikes some natural object 
such as a tree or a stone, the streams of air divide, 
part of them passing to the sides and part going 
over the top. The air begins to divide some 
distance before it reaches the object and the result is 
a rising current on one side and a falling current 
on the other. 

These currents are the bugbears of aviators for 
when one end of their machine passes into such a 
current that end rises or falls depending whether 
or not the current is rising or falling. 

.. figure:: images/Image25.jpg
   :scale: 85 %
   :alt: Fig. 26.—Top view, showing how streams of air divide. 
   
   Fig. 26.—Top view, showing how streams of air divide. 

Other rising and falling currents are caused by 
the sun passing behind clouds. Portions of the 
atmosphere are thus chilled and commence to fall 
while others upon which the sun is reappearing are 
heated and rise. Balloonists constantly encounter 
these changes in temperature and the gas in the 
bag expands or contracts so rapidly that it often 
requires a skillful pilot to prevent disaster. 

These rising and falling currents caused by 
changes of temperature may be clearly seen on the 
surface of a lake if the observer is stationed at a 
height where he may look down on the water. 
In some places the water is covered with smooth 
glassy streaks which run in various directions. 
These smooth streaks are evidence of rising 
currents of air at those places. The rough spots 
which suddenly spread out and run across the 
water are caused by descending currents. 

Therefore it is not good judgment to attempt 
gliding over ground broken by trees or other 
natural objects or when the wind is blowing over 
12-15 miles per hour. 

.. figure:: images/Image26.jpg
   :scale: 85 %
   :alt: Fig. 27.—Showing how air currents pass over objects.
   
   Fig. 27.—Showing how air currents pass over objects.

Do not under any consideration jump off from 
a height which rises prominently from surrounding 
objects. Otto Lilienthal, the brilliant German 
investigator and engineer who made over two 
thousand gliding flights specifically warned 
experimenters against starting glides from 
precipitous cliffs or buildings. There are two 
excellent reasons for this. First, because when 
jumping from such an elevation, a gust of wind 
rebounds from the sides and strikes the machine 
so that it requires great skill to counteract its 
influence. Second, because, the operator and 
machine are suddenly suspended high in the air. 

.. figure:: images/Image27.jpg
   :scale: 85 %
   :alt: TABLE VELOCITY AND FORCE OF WIND.

Be satisfied at first by running against the wind 
on level ground and making short jumps. After 
some practice, operations may be transferred to 
a gentle slope and the length of the glides 
considerably increased. If the experimenter thus 
proceeds slowly without impatience, there is no 
danger in gliding. It is said that the Wright 
brothers never so much as turned an ankle in the 
hundreds of flights they made, before building a 
power driven machine. 

.. figure:: images/Image28.jpg
   :scale: 85 %
   :alt: Fig. 28—Action of aeroplane.
   
   Fig. 28—Action of aeroplane.

**Action of an Aeroplane**. Before starting to 
glide it is perhaps well to understand how the 
machine operates and supports its passenger. The 
illustration shows the cross section of an aeroplane 
moving forward through the air in the direction 
indicated by the arrow. The front edge of the 
aeroplane is elevated so that the surfaces form an 
angle with the horizontal. The front edge enters 
practically still air and causes it to follow the curve 
of the planes and leave at the rear in a downward 
direction. Since the action and reaction of two 
forces are always equal and opposite, there is a 
force exerted against the aeroplane causing it to 
rise. 

A sky-rocket is caused to ascend by the reaction 
of gases formed by burning powder escaping 
downwards through a small hole. The aeroplane, 
by means of its curvature directs the air 
downwards and so rises itself. 

The planes pass so rapidly on to new and 
undisturbed bodies of air, and stay over one body 
for so brief an instant, that there is no time to 
completely overcome the inertia of the air and 
force it downwards. This may be likened to a 
skater moving swiftly over very thin ice which 
would not bear his weight were he standing still, 
but since he is moving so rapidly, that any one 
portion of the ice does not have time to bend to 
the breaking point, is supported. 

**Equilibrium.** A glider will remain in perfect 
equilibrium only so long as the centre of gravity 
of the machine and operator fall in the same vertical 
line as the pressure exerted by the air. If the 
former is forward of the latter, the machine will 
incline forward and travel downwards. If the 
centre of gravity is to the rear of the centre of 
upward thrust exerted by the air, the head of 
the machine will rise, while if it is to either the 
right or left side, the machine will lean or turn over 
respectively to the right or left. 

.. figure:: images/Image29.jpg
   :scale: 85 %
   :alt: Fig. 29—Ready to Start
   
   Fig. 29—Ready to Start

The centre of pressure on the plane is somewhat 
in advance of the actual dimensional centre of 
the plane. This is due to the curvature of the 
plane and also to the disturbing action upon the 
air of the front edge. 

**To make a glide**, carry the machine to the top 
of a slope. Have two assistants hold the ends of 
the lower plane. Get in underneath and stand 
up between the arm pieces. Grasp the front 
horizontal beam of the lower plane and lift the 
machine until the arm sticks are snugly under the 
arm pits as in the illustration. 

If necessary have the two assistants prepared 
to run a short distance with the machine, but as 
soon as you are in motion you will be relieved of 
all weight and surprised at the lift exerted. 

After getting the machine snugly up under the 
arm pits, face the wind, elevate the front of the 
machine slightly, run a short, distance and leap 
into the air. If you are in the right position you 
will sail to the foot of the slope in free flight. 
To land, push yourself towards the back of the 
machine, so that the glider tips upward slightly 
in front. It will then rise slightly but loose its 
momentum and slowly settle so that you drop 
gently on your feet. 

**Balancing** is accomplished in flight by moving 
the legs and body towards that side which is 
highest. 

.. figure:: images/Image30.jpg
   :scale: 85 %
   :alt: Fig. 30—Lines of Flight
   
   Fig. 30—Lines of Flight

**Shifting the centre of gravity** by swinging, the 
legs forward or moving the body in the same 
direction, will naturally cause the centre of gravity 
to assume a forward position, and being a force 
exerted downwards, the machine will dip and 
descend. A reverse movement of the centre of 
gravity will cause the front of the machine to tip 
up and ascend. But if the upward slant is 
continued too long the glider will loose its forward 
velocity and settle. 

The tendency is always to place the weight of the 
body too far to the rear. After a little experience 
the experimenter will learn how to dip his machine 
to acquire velocity for a rise and to otherwise 
handle it. 

Fig. 29 illustrates two lines of flight in their 
successive stages. At 1 the operator is running along 
the top of the hill and the dotted line from 1 to 2 
represents his course immediately after leaving the 
ground. In case the weight is back slightly too far 
and is not shifted much during the glide, the 
machine will follow the upper line indicated by 
3, 4, 5 and land at 6. If instead, at 2, the body is 
moved forward, the machine will travel down as 
shown by 7 and approach the earth. Having 
attained considerable velocity at *S*, the operator 
moves back and the machine rises, travels 
upwards as at 9 and then settles about at the point 6. 
This latter line of flight is to be preferred since the 
machine does not rise quite so high in the air and 
moreover has more velocity so that the operator 
may rise if necessary. 

If during a flight a gust of wind strikes the 
machine from the front, it will accelerate its vertical 
motion in regard to the earth. That is, if the 
machine is already rising it will rise higher and if 
descending will fall more quickly. A gust of wind 
from the rear will cause the machine to drop 
suddenly and so always glide *into the* wind. 

CHAPTER V. Remarks.
```````````````````

In a little booklet such as this it is even 
impossible to cover the subject of gliding flight fully 
much less power driven aeroplanes, but a short 
description of such a machine built by the author, 
assisted by Mr. Harold Dodd and Mr. Safford 
Adams will no doubt interest many since it has 
been used successfully as a glider in towed flights. 

The machine was attached to an automobile 
by means of a long piano wire bridle. It rises at 
a speed of between 15 and 20 miles per hour and 
remains in the air as long as the auto keeps moving 
at this rate. The grounds used by the author in 
his experiments limited the flights to about 800 feet. 

The automobile in one flight traveled about 
50 miles per hour, but the machine soared on a 
perfectly even keel and without any pitching. 
Just as the author was about to descend, the towing 
wire broke, but the aeroplane glided so gently to 
the ground that it was impossible to tell where 
it first touched. 

The following description of the machine is an 
extract from an article written by Mr. R. S. Brown. 

.. figure:: images/Image31.jpg
   :scale: 85 %
   :alt: Glider Built By The Author

"The two supporting surfaces of the aeroplane 
are five feet wide in the direction of flight and 
twenty six feet long. When the machine is moved 
rapidly forward, the action and reaction of the 
still air on the lower side of the moving surfaces, 
lifts the aeroplane from the ground and supports 
it in the air. The curvature of the planes is that 
segment of a parabola, whose depth is one ninth 
its length. They are spaced one vertically above 
the other and about four and one half feet apart 
in the middle. The ends converge slightly to make 
the machine less affected by cross gusts. The 
longitudinal curvature of the planes is maintained 
by spruce ribs half an inch square and spaced nine 
inches apart. Their front ends are ingeniously 
fastened in brass sockets on the front horizontal 
members and their rear ends project about a foot 
over the rear horizontal pieces. The fabric a 
close woven muslin is put on over the top and 
bottom of the ribs and is fastened by grommets 
to a wire running through the rear ends of the 
ribs, and by strips of felt fastened down to the 
ribs with upholsterer’s tacks. 

"The stanchions are six feet apart except the 
middle two, which are only eighteen inches apart. 
The horizontal pieces of each surface are parallel 
and four feet distant from each other. All are of 
selected spruce, shaped so as to give the greatest 
strength with the least resistance to the air, and 
the least weight. All the many rectangles of the 
structure are braced diagonally with steel piano 
wire. In every one a small turnbuckle is inserted 
to adjust the length. The nuclei of these 
turnbuckles consists of bicycle spokes. By this wiring 
a perfectly rigid truss is formed. 

"Ten feet to the rear of the main body, there is 
a horizontal tail, which halves a vertical rudder of 
about the same area. This vertical surface is 
movable and turns the aeroplane to the right and 
left when moved by rotation of the steering wheel. 
As can be seen in the accompanying illustration 
these rudders are strongly supported from the 
principal structure. 

"At an equal distance in front of the supporting 
planes is the elevation rudder. This consists of 
two horizontal plane surfaces, six feet by two. 
These turn about a horizontal axis transverse 
to the direction of flight. Thus the angle which 
they present to the wind can be altered at the 
will of the operator. This is accomplished by 
pushing and pulling on the steering wheel. Through 
the middle of the horizontal surface runs a 
triangular vertical plane. This is designed to 
prevent the turning of the machine by a gust striking 
the rear vertical rudder, for if it strikes both 
vertical surfaces, one in front and one behind, 
the two neutralize each other and no turning takes 
place. 

"On the ground the machine runs on three 
twenty-inch pneumatic tired wheels. These were 
especially made for the purpose, with seamless 
rims and heavy motorcycle spokes. Two are 
set in regular forks of tubing under the rear edge 
of the lower plane, while the third wheel is 
considerably in advance of the body proper. When 
running on the ground preparatory to rising, the 
machine is carried on these little wheels. 

"The operators seat is in front of the supporting 
planes, and as the photograph shows is carried 
on two braces from the front wheel. Sitting in 
the seat, the aviator can direct the aeroplane from 
side to side by turning the steering wheel before 
him. This steering wheel is mounted on a post 
hinged at the bottom, and by pushing or pulling 
on the wheel the aviator is enabled to control his 
height above ground by means of the elevation 
rudder which is connected by a wooden rod to the 
steering post. 

"Mid-way between the two main surfaces and 
at the front of each end is a small plane. These are 
tilted at positive and negative angles to the wind, 
by means of cords connecting them with a pivoted 
bar moved by the pilots feet. In flight, if one 
end rises, the aviator presses down the end of the 
bar on the rising side. This causes the 'balancing 
plane' on the high side, which is the name given 
to the movable planes just described, to form a 
negative angle with the wind so that the high side 
is forced down. The other balancing plane assumes 
an equal positive angle, so as to force up the lower 
side. Thus the machine is again brought to an 
even keel. After a little experience, this action 
becomes almost automatic, so that no difficulty 
is experienced in keeping the flyer level. 

"The motor, which at present has not been 
installed, will be supported between the two main 
planes and connected to a laminated spruce 
propeller, six feet in diameter.” 

Those who of until late have not been associated 
with aeronautics can scarcely realize the steps by 
which aviation had progressed and the trend 
towards building machines. 

The aeroplane worker can no longer be classified 
with the seeker after perpetual motion. It is 
therefore to be lamented that so many of these 
machines partake of freak construction. Originality 
is always to be fostered but must bear some degree 
of proportion. 

Only a very few favored people in comparison 
to the rest of civilization have been enabled to see 
an aeroplane in flight. Many times less are those 
who have had the privilege of examining a 
successful machine. 

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**THE THEORY AND PRACTICE OF MODEL 
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BOOKS ON AERONAUTICS.
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**FLIGHT-VELOCITY.** By A. Samuelson. This work is a short 
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GOOD BOOKS FOR WIRELESS OPERATORS. 
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With tables of windings for coils giving 1/4 in. spark up 
to 12 in. sparks. With full description for the 
construction of mercury interrupters. 76 pages, 35 illustrations. 
Price, 25c.; cloth binding, 50c. 

Full descriptive circular of The Model Library Series 
of practical Handbooks FREE. 

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