Produced by James Simmons.
This file was produced from page images at the Internet Archive.
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.
HOW TO BUILD A 20-FOOT
*BI-PLANE GLIDER*
_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._
BY
ALFRED POWELL MORGAN
_Editor Mechanical and Electrical Department of the_
_“Boy’s Magazine.”_
NEW EDITION, REVISED
NEW YORK
SPON & CHAMBERLAIN, 123 LIBERTY ST.
LONDON
*E. & F. N. SPON, LIMITED, 57 HAYMARKET, S.W.*
1912
Copyright, 1909, by
Spon & Chamberlain.
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.
HOW TO BUILD A 20-FOOT BI-PLANE GLIDER ............................
PREFACE .........................................................
CHAPTER I. The Framework. .......................................
CHAPTER II. Covering the Planes. ................................
CHAPTER III. Trussing. ..........................................
CHAPTER IV. Gliding. ............................................
CHAPTER V. Remarks. .............................................
BOOKS FOR AVIATORS ..............................................
BOOKS ON AERONAUTICS. ...........................................
MODEL AEROPLANES. ...............................................
GOOD BOOKS FOR WIRELESS OPERATORS. ..............................
Fig. 1 Horizontal Beam ............................................
Fig. 2.—Strut. ....................................................
Fig. 3.—Position of Struts. .......................................
Fig. 4.—Strut clamp. ..............................................
Fig. 5.—Stanchion. ................................................
Fig. 6.—Stanchion socket. .........................................
Fig. 7.—Eyebolt. ..................................................
Fig. 8.—Assembly of stanchion, socket beam, strut and clamp. ......
Fig. 9.—Rib. ......................................................
Fig. 10.—Rib clamp. ...............................................
Fig. 11.—Plan View of Planes showing Ribs. ........................
Fig. 12.—Arm piece. ...............................................
Fig. 13.—Parts of rudder framework. ...............................
Fig. 14.—Corners of horizontal rudder plane. ......................
Fig. 15.—Complete framework of rudder. ............................
Fig. 16.—Cross bar. ...............................................
Fig. 17.—Rudder Sockets, or Clamps. ...............................
Fig. 18.—Arrangement of Armpieces and Rudder Cross Bar. ...........
Fig. 19.—Complete Framework Ribs on Lower Plane Not Shown .........
Fig. 20.—Method of hemming up edge of cloth. ......................
Fig. 21.—Section of cloth hemmed, and reinforcing strips sewn on. .
Fig. 22.—Trussing Of Cells. .......................................
Fig. 23.—Plan and Elevation Views of Piano Wire Bracing. ..........
Fig. 24.—Method of anchoring wires ................................
Fig. 25.—Bicycle spoke turnbuckle. ................................
Fig. 26.—Top view, showing how streams of air divide. .............
Fig. 27.—Showing how air currents pass over objects. ..............
Fig. 28—Action of aeroplane. ......................................
Fig. 29—Ready to Start ............................................
Fig. 30—Lines of Flight ...........................................
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.
[Illustration: 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.
[Illustration: 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.
[Illustration: 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.
[Illustration: Fig. 4.—Strut clamp.]
*Stanchions*. The planes are separated by twelve stanchions, four feet
long and 7/8 of an inch in diameter.
[Illustration: 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 purchased¹
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.
[Illustration: 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.
[Illustration: 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.
[Illustration: 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.
[Illustration: 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.
[Illustration: 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.
[Illustration: 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.
[Illustration: 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.
[Illustration: 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.
[Illustration: Fig. 14.—Corners of horizontal rudder plane.]
Corner braces are also used to strengthen the vertical plane.
[Illustration: 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.
[Illustration: 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.
[Illustration: Fig. 17.—Rudder Sockets, or Clamps.]
[Illustration: Fig. 18.—Arrangement of Armpieces and Rudder Cross Bar.]
[Illustration: 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.
¹ From Spon & Chamberlain