PONTOONS
Having satisfactorily developed the hand launched model and the model rising off the ground under its own propulsion the constructor will next turn his mind to the question of having his model rise under its own power from the surface of the water in the fashion of passenger-carrying hydros and flying boats. This will be accomplished by the use of pontoons attached to a specially designed chassis.
C. V. Obst World record flying boat
Twin tractor Hydroaƫroplane designed and constructed by
George F. McLaughlin
Louis Bambergerās hydro about to leave surface of water
Three pontoons are necessary and these should be made as light as possible. Each pontoon should be made 6ā³ long, 1ā³ deep toward the forward part, by Ā³āāā³ at the rear and 2ā³ wide. The side members of each pontoon are made from pieces of thin white pine wood Ā¹āāānd of an inch thick, slightly curved up at the front and sloped down toward the rear. Small niches should be made on the top and bottom sides of the pontoons into which the cross braces are inserted and glued. Further reference to [diagram 10] will show that at the extreme forward end of the sides a cut is made large enough to receive a flat piece of spruce Ā¹āāāā³ wide. Another cut of the same dimensions is made at the extreme rear end. Still further cuts are made on the top and bottom sides of the pontoons, the forward cuts measuring 1Ā¹āāā³ from the front and the rear cuts 1Ā¹āāā³ from the rear, to join the sides of the pontoons as illustrated in [diagram 10]. Six pieces of Ā¹āāāā³ flat spruce are required for the rear pontoon, the ends of which are held in position by glue. For the forward pontoon only 4 braces are required in so far as the ends of the two main brace spars of the forward part of chassis are inserted in the cuts on the top sides of the pontoon. These brace spars measure 10 inches in length and are made from bamboo Ā¹āāth inch in diameter, which necessitates enlargement of the cuts on the top sides of the forward pontoons so that the extreme ends of the spars can be inserted in the cuts in the place of the braces. To complete the rear pontoon and prepare it for covering, three strips of Ā¹āāā³ bamboo are required for struts. Two of these strips should measure 9ā³ in length and should be attached to the front of the pontoon on the inner side as shown in [diagram 10]. Thread and glue should be used in attaching the ends of the strips to the pontoon. To enable fastening to the frame the upper ends of the bamboo strips should be bent over about Ā¹āāā³. The third strip should measure 8ā³ in length and is attached to the upper and lower braces toward the front of the pontoon as shown in the [diagram]. It is necessary that this strip be secured in the approximate center of the pontoon to insure a good balance. For the purpose of securing the upper end of the third strut to the center of the propeller brace a piece of wire 1Ā¹āāā³ long should be secured to the upper end of the strut and looped as shown in [diagram 10]. The three pontoons should now be covered with fiber paper and it is necessary to exercise care to avoid punctures. For the purpose of coating the fiber paper to render it waterproof, a satisfactory solution can be made by mixing banana oil with celluloid until it has attained the desired thickness, after which it should be applied to the covering of the pontoons with a soft brush.
For the main strut of the forward portion of the chassis two pieces of Ā¹āāā³ bamboo, each 11ā³ in length, are required and these should be bent over 1ā³ on one end as shown in the [diagram], that they may be fastened to the under side of the frame members, one on either side at a point on that member 11ā³ from the front. Two similar pieces of bamboo, each piece 8ā³ in length, are required to act as braces between the frame members and the main chassis struts. Each end of the braces should be bent over in the same direction and in the same manner as that described for the main struts so that the fastening to the main frame member and the main chassis struts may be accomplished. Steam or an alcohol lamp may be used in bending the ends of the pieces of bamboo. To make the chassis sufficiently stable a piece of bamboo 7Ā¹āāā³ should be fastened from either side of the main chassis struts at the point where the chassis brace on either side meets with the main strut. The ends of this cross brace should be bent in similar fashion to the other braces to enable its being fastened easily and permanently.
For the accommodation of the pontoons two strips of flat steel wire, each 4ā³ in length, should be attached to the ends of the main struts, about one inch from the bottom, the farthest ends should be bent to grip the second spar which joins the pontoons. Note [diagram 10].
To further strengthen the chassis a strip of flat steel wire sufficiently long enough should be bent so that Ā¹āāā³ of the central portion can be securely fastened to the center of the cross brace as shown in [diagram 10]. The two outer ends should be bent down and are fastened to the wires which are attached to the bottom ends of the struts. This method of attaching the forward pontoons enables the constructor to adjust them to any desired angle and also detach them when not in use.
A model hydroaƫroplane is one of the most interesting types of models and if properly taken care of will afford the constructor many pleasant moments.
Erwin B. Eiring about to release R. O. G. Model. (Note manner of holding propellers.) Kennith Sedgwick, tractor record holder Milwaukee Model Club. Courtesy Gilbert Counsell.
Waid Carl releasing R. O. G. Model. Courtesy Edward P. Warner.