Popular Mechanics/Volume 13/Issue 6/How to Build the Famous "Demoiselle" Santos-Dumont Monoplane

by Arthur E. Joerin, A. Cross, A. M.

HOW TO BUILD THE FAMOUS "DEMOISELLE"
SANTOS-DUMONT'S MONOPLANE

By ARTHUR E. JOERIN AND A. CROSS, A. M.

(Paris)

FROM time to time vague descriptions of the manner of constructing aeroplanes have been given to the public. All over the United States there are thousands of persons who are intensely interested in the subject of aerial flight, but until now nothing of a tangible nature has been presented on which work could be started with a reasonable prospect of success. It is a great satisfaction therefore, to be able to present the working drawings of the wonderful monoplane invented by M. Santos-Dumont. As the authors point out, however, it would be useless for anyone not possessed of some mechanical skill, and plenty of common sense, to attempt to construct a copy of the famous flyer, even with such detailed workings and instructions. — THE EDITOR.

FOLLOWING the announcement, made some months ago by Alberto Santos-Dumont that he intended to give the plans of his latest aeroplane, the "Demoiselle," to the world in the interest of aeronautics, great interest has been centered in the wonderful monoplane. It is the lightest and smallest of all heavier-than-air machines, yet is thoroughly practical. It was with this monoplane that the renowned aviator made a flight from St. Cyr to Buc. on the 13th of September last at a speed of 56 miles an hour.

This machine is better than any other which has ever been built, for those who wish to reach results with the least possible expense and with a minimum of experimenting. The plans which accompany this article are identical with those from which the machines are now being built in France.

As it would lead us too far from the purpose of this article if we were to take up at length such questions as the strength, flexibility, and resistance and other properties of materials we shall restrict ourselves to a description of the manner of constructing the flyer. It would be well, of course, for the prospective aviator to make himself acquainted with the subject of atmosphere as it applies to aeronautics, to have a good general knowledge of gasoline motors, and to study the properties and qualities of the different materials which enter into the construction of the monoplane.

It is clearly impossible to go into these subjects at any great length here, but the one who is ambitious to become thoroughly conversant with the subject of aerial navigation, will not fail to consult suitable books on these subjects. Of course the possession of plans is the basis without which it would be impossible to set about building the airship, but at the same time it is necessary to possess some mechanical skill and ability, and plenty of common sense.

In presenting the plans through Popular Mechanics Magazine we trust that no one of our readers will start to build unless he possesses these qualities, especially the latter, without which he will never be able to accomplish anything.

That the monoplane is the superior form of heavier-than-air machine is the opinion of a majority of the aviation experts. Biplanes and even triplanes have made wonderful flights. but no flying-machine ever built has

proven so easy to balance as the monoplane. The principal objection to it up to within a short time has been the difficulty of bracing the plane. With the biplane the trussing was of great service in this connection. But with the guide wires firmly fixed from the frame to the wings there is little probability of any difficulty with the Santos-Dumont type.

At the very beginning it might be well to state that the greatest items of expense in the construction of the machine will be the motor and the propeller. Santos-Dumont used a Darracq motor of 30 hp. in his record-breaking flight, although he had previously made some fine flights with a 17-hp. motor. There are American motors which will do just as well, probably. and will undoubtedly be much cheaper, as the importation of one from France involves the expense of freight and customs duties.

The construction of the propeller is vitally important, and we would advise that this be purchased.

A good place at which to start would be the vertical rudder, Plate III. The thickness of the bamboo there given is the maximum one. The stronger and heavier portions are used for the centers where the joints are formed and the strain is heaviest. The detailed drawing C on this plate shows the manner in which the cloth is attached to the framework by gauge No. 21 piano wire. As it is done at this point so it should be done on all parts of the monoplane. After having sewn the piano wire into the outer edge of the cloth, taking care to leave open the part where the wire is to be attached to the framework, the wire should be stretched to get it to the extremity, and then dropped into the slot made for it to rest in on the outer end of the bamboo. Thus the planes of cloth are well stretched, and are held firmly in place, adding to the strength of the machine. The same end could not be accomplished nearly as well by first attaching the wire and then sewing the cloth thereon. This applies to the wings also where every added bit of strength and firmness adds to the successful completion. Slots are made at the end of the bamboos for the wires to slip into and be held fast. It is a good idea to put a cork into the hollow ends of the rods, and to cut the slots in both at the same time. The brass wire, gauge No. 25, should also be wound around the rod just below the end of the slot. This prevents the piano wire on which the cloth is sewn from splitting the rods. It may seem that this arrangement is crude, yet it is the way that Santos-Dumont made the ends when he flew from St. Cyr to Buc. Later on—he had a number of "Demoiselles," and small breaks happened now and then—he put a little metal cap over the ends of the rods. Slots were made in these caps to receive the wires. We have described the former because it is by far the easier way for amateur airship builders.

 

M. Santos-Dumont about to Start Flight in the
"Demoiselle"

The cloth used by Santos-Dumont was a very finely woven silk. Silk does not rot as easily as cotton and is considerably stronger. Silk has the great objection of expense, however, and it would probably be as well to use percale or strong muslin, care being taken to secure the best grade of closely woven and unbleached goods.

The method of making the joint at B is well shown in the drawing. The use of steel or aluminum plates is very important for it would be impossible to secure the necessary strength without them. The clever idea adopted by the inventor of the machine practically makes this joint in one piece, and he experienced little or no trouble at this point. The ends of the two smaller pieces are inserted for about a quarter of an inch into the vertical piece as is shown. If one wishes to finish the work particularly well, cabinetmaker's muscilage or several coats of varnish may be put on at these joints. It serves to retard decay in the bamboo.

Plate IV shows the details of the horizontal rudder which governs the altitude of the machine. "Gouvenail de Profendeur" is the French term for it. It should be constructed in the same general way as the vertical rudder. At the point where the rudders join it is necessary to cut the cloth of the horizontal rudder and sew it to the cloth of the vertical rudder on both sides. If this is done properly no rods will be visible, all being covered by the cloth. The manner in which the cloth covers the rods is shown at Con Plate III.

 

Rear View of "Demoiselle"

The method of attaching the rudders to the frame is shown on Plate IV. This is practically a universal joint, allowing the steering device to be turned in any direction by the controlling wires shown on Plate I, and also in the smaller illustration of the monoplane. These wires should be carefully selected and tested for a great deal depends upon their strength. It would be very imprudent to use ordinary piano string or wire. Santos-Dumont uses a flexible metallic wire, gauge No. 13, with a flaxen cord in the center. This wire will withstand the constant bending without danger of breaking. The joint should be made of the best steel tubing procurable as it performs a very important function. Good bicycle tubing is excellent.

(Concluded in the July Issue of
Popular Mechanics )