Aeroplane Construction and Operation

by John B. Rathbun

Fig. 39. Chassis Connection.

Both methods have a common fault, in that they are unreliable. Imperfect welds and brazing are not always apparent from the outside, actual breakage of the part being necessary to determine the true nature of the joint.

FUSELAGE WEIGHTS.

Distribution of Weight. The weight of a fuselage depends upon the span of the wings, upon the seating capacity, and upon the weight and type of the power plant. The weight also varies considerably with the type of construction, that is, whether of truss, veneer, or monocoque construction. A heavily powered machine, or one carrying more than a single person, requires heavier structural members and hence weighs more than a small single seater. The amount of fuel carried also has a considerable bearing on the fuselage weight.

Probably the best method of treating this subject is to give the fuselage weights of several types of well known machines. The reader will then have at least a comparative basis for determining the approximate weight. (Truss type only.)

There are so many variables that the weight cannot be determined by any set rule or formula. Alexander Klemin in his "Course in Aerodynamics and Airplane Design" says that the approximate weight of a bare wood truss type fuselage is about 150 pounds for a machine having a total weight of 2,500 pounds. For small biplane and monoplane scouts weighing approximately 1,200 pounds total, the bare fuselage frame will weigh about 70 pounds. These figures are for the bare frame alone and without seats, controls, tail skids or other fittings. The weights given under the column headed "Wt. Bare" include the engine beds, tail skids, flooring, cowling and body covering, and hence exceed the "bone bare" estimate of Klemin by a considerable amount.

The all-steel fuselage of the large Sturtevant battle-plane (Model A) weighs 165 pounds inclusive of the steel engine bed. A wooden, wire braced fuselage of the same size and strength weighs well over 200 pounds, the metal fittings and wires weighing about 60 pounds alone. Ash is used in the wood example for the longerons. The struts and diagonal members in the Sturtevant metal fuselage are riveted directly to the longitudinals, without fittings or connection plates. The safety factor for air loads is 8, and for the ground loads due to taxi-ing over the ground, a safety factor of 4 is used.

After a minute comparison of the items comprising the fuselage of the Curtiss JN4-B and the Standard H-3, Klemin finds that the fuselage assembly of the Standard H-3 amounts to 13.6 per cent of the total loaded weight, and that the fuselage of the Curtiss JN4-B is 15.5 per cent of the total. Tanks, piping and controls are omitted in both cases. For machines weighing about 2,500 pounds, Dr. J. C. Hunsaker finds the body weight averaging 8.2 per cent of the total, this figure being the average taken from a number of machines.