Hydro-monoplane
The present machine is capable of making a flight of about sixty
seconds after rising from the water, which it does after travelling
from 8 ft. to 10 ft. under normal conditions. This model is what is
known as the “A” frame (see Chapter III.) type of monoplane fitted with
a loaded elevator.
The framework or fuselage is not constructed in quite the orthodox
manner, but in the manner shown in section at =D= and =E= (Fig. 124).
These side members are made from two pieces of best silver spruce 3
ft. 3 in. long, ⅜ in. by ¼ in. at the forward or elevator end, ½ in.
by ¼ in. in the middle, between the elevator and the main plane, and
⅜ in. by ³/₁₆ in. at the propeller end. This tapering is necessary in
order to make the wood proportionate to the strain to which it will
be subjected. This is called a cantilever. After each stick has been
planed to the above sizes, a hollow chisel is used to channel out the
wood on one side, the finish being given with a woodworker’s file.
The opposite side is rounded off after the inside is finished. The
front ends are bound together and glued, the forward hooks (to which
the rubber is attached), and the protector, shown by Fig. 125, being
incorporated at the same time; these are made of No. 18 and No. 20
S.W.G. piano wire respectively.
The other extremity of the fuselage is held 9½ in. apart by means
of a bamboo distance strut, measuring ³/16 in. by ¹/16 in. This
strut, together with the three others, is carefully shaped, the
ends sharpened, and then fitted into a split in the side members as
indicated in Fig. 126. Considerable care is needed in making this form
of joint; but when the joints are glued and bound over with ¼-in. strip
silk, they are wonderfully strong.
The propeller bearings are made of No. 18 S.W.G. wire, and resemble
a lady’s plain hairpin bent at right angles midway, with a cupped
washer soldered on the round end to take the thrust (see Fig. 127).
These washers, known as French clock collets or cupped washers, may
be procured at any watch repairer’s at 3d. per dozen. The propeller
bearings should be bound to the fuselage at the same time as the end
distance piece is fixed. The frame is trussed with two diagonal bracing
wires; No. 30 S.W.G. piano wire should be used, this being strained
with the aid of hooks as shown in Fig. 128. To tighten the wire, twist
the hooks with a pair of round-nose pliers.
The main plane is 37 in. in span, with a maximum width of 7 in. at
the centre, tapering to 6 in. at 3 in. from the tip. The camber is ¾
in. at the centre and ⅜ in. near the tip. The frame is constructed
of bamboo, the leading edge and the end ribs being one long piece of
selected yellow bamboo, ³/₁₆ in. by ³/₃₂ in., and is bent to the shape
by holding over an incandescent gas burner. The trailing edge is made
of similar material; but is straight when looked at in plan. This piece
measures 34 in. by ³/₁₆ in. by ³/₃₂ in., and is joined to the end ribs
as shown at =C= (Fig. 129), afterwards being bound with strip silk. The
ribs are all ³/₁₆ in. by ¹/₁₆ in., being bent in the manner suggested
above and split-jointed into the spars.
[Illustration: Fig. 124.—Plan]
[Illustration: Fig. 125.—Nose of Model]
[Illustration: Fig. 126.—Cross Member Joint]
[Illustration: Fig. 127.—Bearings]
[Illustration: Fig. 128.—Bracing Anchorage]
[Illustration: Fig. 129.—Rib Attachment]
The main plane has a dihedral angle of 1 in 7; that is, the tips are
about 2⅝ in. higher than the centre of the plane. The plane is covered
with proofed silk secured with fish glue.
The elevator is a miniature edition of the main plane, being 13 in. in
span and provided with a chord of 3½ in. The camber is ⅜ in. at the
centre and ³/₁₆ in. at the tips. It is attached to the framework in the
following manner: Two straight pieces of thin bamboo 5 in. long are
attached to the under-side of the elevator, and run parallel to the
tapered end of the fuselage, and the projecting ends of these pieces
are attached to the frame with elastic bands. To give an increased
angle, blocks of wood are placed under the bamboo strips as shown in
Fig. 125, these pieces being ¼ in. high. A greater or less angle may be
given by moving the blocks either backwards or forwards as required.
[Illustration: Fig. 130.—Side Elevation]
[Illustration: Fig. 131.—Floats]
[Illustration: Fig. 132.—Rear Float]
[Illustration: Fig. 131A.—Rear Float]
[Illustration: Fig. 133.—Screw Eye]
[Illustration: Fig. 134.—Rear Elevation]
The floats are three in number, and are of equal dimensions, 6 in. by
2 in. by ¾ in. at the greatest depth, which is about three parts of
the way from the front. To construct the floats, two side pieces of
¹/₂₀-in. birch are cut to the shape given in Figs. 130 to 131A, and
these are nailed to the ends of a piece of whitewood measuring 2 in.
by ¾ in. by ⅛ in. Joining each end of the side pieces is a piece of
whitewood, cut to fit so as to form a nice entry, the forward piece
being flat on top and the rear piece flat on the bottom. At the place
marked =G= (Fig. 130) there is an additional piece to strengthen the
float and keep the silk covering taut. Running from front to back there
is a ⅛-in. by ¹/₁₆-in. strip of bamboo to keep the silk from sagging
when running on the water. The front floats are nailed to the bamboo
cross-piece, and the adjustment is made by bending the small pieces of
piano-wire =F=. The rear float attachment is shown by Fig. 132, and the
adjustment is made in the same way. The wire is attached to the floats
with small hooks as shown by Fig. 133, these being screwed into the
distance pieces of the float. The connecting wires are bound to the
fuselage with strip silk and glued. The flat portion of the under-side
of the front floats has an angle of incidence of 1 in 6, the rear float
angle being 1 in 8.
Another type of float is quite practicable, if preferred.
[Illustration: Fig. 135.—Model Hydroplane]
The propellers are 10 in. in diameter with a pitch of 23 in., and are
carved from a solid piece of mahogany. The blades are glasspapered to
a thickness of about ¹/₂₀ in., and are strengthened with silk stuck on
one side.
The floats are covered with the same proofed silk as the planes; but to
ensure complete imperviousness to water, coat with a mixture of 2 parts
of boiled oil and 1 part of gold size. Fig. 134 is a rear elevation.
The main plane rests flat on the fuselage, and is held in place by
means of two 9-in. by ⅛-in. by ¹/₁₆-in. pieces of bamboo, which are
secured to the framework with elastic. This method allows the plane to
be readily removed. There are six strands of thick ¼-in. strip elastic
to each propeller, and the number of turns given is about 900 when well
lubricated.
The total weight of the complete model is only 6 oz., and in making the
machine every effort should be made not to exceed this amount.
Fig. 135 shows a model hydro-monoplane in perspective.