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beams。 All of these parts are shown in the illustrations；
reference to which will make the meaning of the
various names clear。
Quantity and Cost of Material。
For the horizontal beams four pieces of spruce； 20 feet
long； 1 1/2 inches wide and 3/4 inch thick are necessary。
These pieces must be straight…grain； and absolutely free
from knots。 If it is impossible to obtain clear pieces
of this length； shorter ones may be spliced； but this is
not advised as it adds materially to the weight。 The
twelve stanchions should be 4 feet long and 7/8 inch in
diameter and rounded in form so as to offer as little
resistance as possible to the wind。 The struts； there
are twelve of them； are 3 feet long by 11/4 x 1/2 inch。 For
a 20…foot biplane about 20 yards of stout silk or unbleached
muslin； of standard one yard width； will be
needed。 The forty…one ribs are each 4 feet long； and
1/2 inch square。 A roll of No。 12 piano wire； twenty…four
sockets； a package of small copper tacks； a pot of glue；
and similar accessories will be required。 The entire
cost of this material should not exceed 20。 The wood
and cloth will be the two largest items； and these should
not cost more than 10。 This leaves 10 for the varnish；
wire； tacks； glue； and other incidentals。 This estimate
is made for cost of materials only； it being taken for
granted that the experimenter will construct his own
glider。 Should the services of a carpenter be required
the total cost will probably approximate 60 or 70。
Application of the Rudders。
The figures given also include the expense of rudders；
but the details of these have not been included as the
glider is really complete without them。 Some of the best
flights the writer ever saw were made by Mr。 A。 M。 Herring in a
glider without a rudder； and yet there can
be no doubt that a rudder； properly proportioned and
placed； especially a rear rudder； is of great value to the
aviator as it keeps the machine with its head to the
wind； which is the only safe position for a novice。 For
initial educational purposes； however； a rudder is not
essential as the glides will； or should； be made on level
ground； in moderate； steady wind currents； and at a
modest elevation。 The addition of a rudder； therefore；
may well be left until the aviator has become reasonably
expert in the management of his machine。
Putting the Machine Together。
Having obtained the necessary material； the first move
is to have the rib pieces steamed and curved。 This curve
may be slight； about 2 inches for the 4 feet。 While
this is being done the other parts should be carefully
rounded so the square edges will be taken off。 This
may be done with sand paper。 Next apply a coat of
shellac； and when dry rub it down thoroughly with fine
sand paper。 When the ribs are curved treat them in
the same way。
Lay two of the long horizontal frame pieces on the
floor 3 feet apart。 Between these place six of the strut
pieces。 Put one at each end； and each 4 1/2 feet put
another； leaving a 2…foot space in the center。 This will
give you four struts 4 1/2 feet apart； and two in the center
2 feet apart； as shown in the illustration。 This makes
five rectangles。 Be sure that the points of contact are
perfect； and that the struts are exactly at right angles
with the horizontal frames。 This is a most important
feature because if your frame 〃skews〃 or twists you
cannot keep it straight in the air。 Now glue the ends
of the struts to the frame pieces； using plenty of glue；
and nail on strips that will hold the frame in place while
the glue is drying。 The next day lash the joints together
firmly with the shoe thread； winding it as you would to
mend a broken gun stock； and over each layer put a
coating of glue。 This done； the other frame pieces and
struts may be treated in the same way； and you will thus
get the foundations for the two planes。
Another Way of Placing Struts。
In the machines built for professional use a stronger
and more certain form of construction is desired。 This
is secured by the placing the struts for the lower plane
under the frame piece； and those for the upper plane
over it； allowing them in each instance to come out flush
with the outer edges of the frame pieces。 They are then
securely fastened with a tie plate or clamp which passes
over the end of the strut and is bound firmly against
the surface of the frame piece by the eye bolts of the
stanchion sockets。
Placing the Rib Pieces。
Take one of the frames and place on it the ribs； with
the arched side up； letting one end of the ribs come
flush with the front edge of the forward frame； and the
other end projecting about a foot beyond the rear frame。
The manner of fastening the ribs to the frame pieces is
optional。 In some cases they are lashed with shoe
thread； and in others clamped with a metal clamp fastened
with 1/2…inch wood screws。 Where clamps and
screws are used care should be taken to make slight
holes in the wood with an awl before starting the screws
so as to lessen any tendency to split the wood。 On the
top frame； twenty…one ribs placed one foot apart will be
required。 On the lower frame； because of the opening
left for the operator's body； you will need only twenty。
Joining the Two Frames。
The two frames must now be joined together。 For this
you will need twenty…four aluminum or iron sockets
which may be purchased at a foundry or hardware shop。
These sockets； as the name implies； provide a receptacle
in which the end of a stanchion is firmly held； and have
flanges with holes for eye…bolts which hold them firmly
to the frame pieces； and also serve to hold the guy wires。
In addition to these eye…bolt holes there are two others
through which screws are fastened into the frame pieces。
On the front frame piece of the bottom plane place six
sockets； beginning at the end of the frame； and locating
them exactly opposite the struts。 Screw the sockets into
position with wood screws； and then put the eye…bolts in
place。 Repeat the operation on the rear frame。 Next
put the sockets for the upper plane frame in place。
You are now ready to bring the two planes together。
Begin by inserting the stanchions in the sockets in the
lower plane。 The ends may need a little rubbing with
sandpaper to get them into the sockets； but care must
be taken to have them fit snugly。 When all the stanchions
are in place on the lower plane； lift the upper
plane into position； and fit the sockets over the upper
ends of the stanchions。
Trussing with Guy Wires。
The next move is to 〃tie〃 the frame together rigidly
by the aid of guy wires。 This is where the No。 12 piano
wire comes in。 Each rectangle formed by the struts and
stanchions with the exception of the small center one；
is to be wired separately as shown in the illustration。
At each of the eight corners forming the rectangle the
ring of one of the eye…bolts will