Three pontoons are necessary and these should be made as light as possible. Each pontoon should be made 6″ long, 1″ deep toward the forward part, by ³⁄₄″ at the rear and 2″ wide. The side members of each pontoon are made from pieces of thin white pine wood ¹⁄₃₂nd 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 crossbraces are inserted and glued. Further reference todiagram 10will show that at the extreme forward end of the sides a cut is made large enough to receive a flat piece of spruce ¹⁄₁₆″ 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 1¹⁄₂″ from the front and the rear cuts 1¹⁄₂″ from the rear, to join the sides of the pontoons as illustrated indiagram 10. Six pieces of ¹⁄₁₆″ 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 ¹⁄₈th 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 placeof the braces. To complete the rear pontoon and prepare it for covering, three strips of ¹⁄₈″ bamboo are required for struts. Two of these strips should measure 9″ in length and should be attached to the front of the pontoon on the inner side as shown indiagram 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 ¹⁄₂″. The third strip should measure 8″ in length and is attached to the upper and lower braces toward the front of the pontoon as shown in thediagram. 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 1¹⁄₂″ long should be secured to the upper end of the strut and looped as shown indiagram 10. The three pontoons should now be covered with fiber paper and it is necessary to exercise care to avoid punctures. Forthe 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 ¹⁄₈″ bamboo, each 11″ in length, are required and these should be bent over 1″ on one end as shown in thediagram, that they may be fastened to the under side of the frame members, one on either side at a point on that member 11″ from the front. Two similar pieces of bamboo, each piece 8″ 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 ofbamboo. To make the chassis sufficiently stable a piece of bamboo 7¹⁄₂″ 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 4″ 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. Notediagram 10.
To further strengthen the chassis a strip of flat steel wire sufficiently long enough should be bent so that ¹⁄₂″ of the central portion can be securely fastened to the center of the cross brace as shown indiagram 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 hydroaëroplane is one of the most interesting types of models and if properly taken care of will afford the constructor many pleasant moments.