Both the floats which take practically the whole weight of the machine are situated directly under the wing just far enough behind the center of gravity to prevent the model from tipping backward. These floats are attached to the engine base by means of streamlined bamboo struts. Bamboo is also used in the construction of the float frames. A single float of triangular sections is situated just behind the propeller. The entire weight of the floats and their attachments is but .23 ounces.
The propeller which consists of four blades is built up of two propellers joined together at the hubs and securely glued, the completed propeller having a diameter of 10″ with a theoretical pitch of 14″. The blades are fairly narrow, tapering almost to a point at the tips. The propeller is driven by five strands of ³⁄₁₆th″ strip rubber at about 760 r.p.m. when the model is in flight. At the time when the model made its record flight of 116 seconds the rubber was given 1500 turns which is not the maximum number of turns. At other times the model has flown satisfactorily with less turns of the rubber. While in the air the model flies very slow and stable notwithstanding its light weight and large surface. On three occasions the model has made durations of approximately 90 seconds which rather dispenses the possibility of its being termed a freak.
THE LA TOUR FLYING BOAT
One of the most notable results of the National Model Aëroplane Competition of 1915 was the establishing of a new world’s record for flying boats. Considering that the model flying boat is a difficult type of model to construct and fly, the establishing of this new world record of 43 seconds is remarkable. Credit for this performance is due Mr. Robert La Tour of the Pacific Northwest Model Aëro Club, who designed, constructed and flew the model flying boat which is herewith described and illustrated. [Diagram 13].
The frame is made of laminated spruce 40″ in length, made of two strips glued together. They are ³⁄₈″ × ¹⁄₈″ at the center tapering to ³⁄₁₆″ × ¹⁄₈″ at the ends. The cross braces are of split bamboo and are fastened to the frame side members by bringing them to a wedge at the ends and then inserting them into slots in the sides of the frame side members and are finally drilled and bound to the latter. The rear brace is of streamlined spruce ¹⁄₄″ × ¹⁄₈″; this butts against the frame side members and is bound to them. The propeller accommodations are made of brass.
The propellers are 10″ in diameter with a 19″ pitch. These are carved from a block of Alaska cedar 1¹⁄₄″ wide by ³⁄₄″ thick. Of course the propellers may also be made from white pine. To turn the propellers 15 strands of ¹⁄₈″ flat rubber are used.
Bamboo about ¹⁄₁₆″ square is used to obtain the outline of the wings. The main wing has a span of 33″ with a chord of 5¹⁄₂″. Split bamboo is used for the making of the 9 ribs. The wing spar or brace is of spruce ³⁄₁₆″ × ¹⁄₈″ and is fastened below the ribs as illustrated in [diagram 13]. The elevator is constructed in like manner but has a span of only 17″ × 4³⁄₄″ and has only 5 ribs. A block ³⁄₄″ high is used for elevation. Both wings have a camber of ¹⁄₂″ and are covered on the upper side with silk doped with a special varnish and a few coats of white shellac.
Diagram 13
The boat is 20″ long, 3″ in width and shaped as shown. The slip is ¹⁄₂″ deep and is located 7″ from the bow. The rear end is brought down steeply to avoid the drag of the water on this point when the boat is leaving the surface of the water. Spruce ³⁄₆₄ths of an inch thick is used for the making of the sides, but the cross bracing is of slightly heavier material, there being six braces used throughout. The rear brace is much heavier in order to withstand the pull of the covering and to receive the ends of the wire connections. The outriggers or balancing pontoons are constructed of the same material as that of the boat and are held together by a spruce beam 18″ long, ¹⁄₂″ wide by ³⁄₁₆″ thick, streamlined. This beam is fastened to the boat by means of three brads to permit changing if necessary. The lower edges of the outriggers should clear the water about ¹⁄₈″ before the steps on the boat leave the water. The boat and outriggers are covered with silk, shrunk with a special solution and then coated several times with white shellac. It is a good plan to shellac the interior walls of the boat and pontoons before covering to prevent them from losing their form by becoming soft from the influence of water in the case of a puncture.