Louis-Pierre Mouillard to Octave Chanute 21-Jul-1891

Sender	Louis-Pierre Mouillard
Recipient	Octave Chanute
Date sent	1891-07-21
From location	France
To location	US
Communication type
Language
Refers to flight?
Tech fields
Length (in words)
Full text available	1

The text of this letter is online at Mississippi State University. Presumably the original letter was in French, and an MS State person translated it to English.

Mouillard says (paraphrased in brief):

• Thanks for offering to translate my two books [from French to English, presumably]
• I am sending you under separate cover most of the rest of Vol sans Battement (Flight without flapping), including the chapter on kites you asked for. There's a table of contents at the end [in the French style]
• I'm still finishing the chapters "Balloons", "Final review", etc.
• I'm interested in your immediate thoughts about whether there is a possibility to make profitable use of some ideas expressed in the book, before it is published. If the kites chapter has workable ideas, please do try them out. You have my permission to do anything you wish to do with them. If it seems wise to take out patents, please do so under the name "O. Chanute from Mouillard," make use of them as you see fit, and I shall be happy.

There is one chapter which I shall withhold until I get some information, otherwise I shall omit it. It deals with the experiments with captive balloons made by the Navy in Toulon. I asked Admiral Aube for this information, but he could not give it to me. He died several months ago. If you could obtain this information for me you would greatly oblige me. This lookout station is one of some interesting points of another aquatic disturbance of my making which I could not finish. It is just as new and just as unimpaired today as it was ten years ago.

Please convey my fellow-feelings to the young engineer you told me about. I shall watch with great interest the construction and tests of what has been the constant thought of my life.

As to the pictured airplane, I had to reread your letter, as I could not see the basic principle. Is it a flapping-wing airplane or a glider? The accompanying drawing resembles the sketch you drew in your letter.

You tell me that the surface of my latest airplane is too large. I only wanted it so for the first tests made in still air. It certainly has no bearing whatever on the design, but it has an enormous carrying capacity. By means of this first practice the aviator is satisfied that the air is supporting him. As soon as he wants to go a step further, trying to rise and consequently be exposed to the action of an air current of about 5 meters, a reduction of the surface will be necessary. This may be done on this machine in a very simple way: The new airplane is traced by means of very taut and well fastened string and everything which goes beyond (the tracing) is clipped off the "'bird." If the surface is still too large, it is decreased again, whereby it may be noticed that decreasing the surface corresponds with increasing the speed. One should arrive at not more than 12 square meters of surface which means a span of 8 meters and a width of 1.50 meters which is a ratio of 5:1 and could be classified as a slow soaring bird. This surface is amply sufficient for one who knows well how to fly in order to be lifted and to ascend without flapping wings. The large vulture has not got as much of a surface, but knows how to use it! It is up to us to learn step by step by recognizing gradually the difficulties and getting used to them. This is the reason this airplane with the exaggerated surface was created, as this surface may be decreased gradually.

As to the two high poles for the experiments you told me about, they are the fad of Bazin and Sanderval. I very often have argued with Bazin about this method and I hope that he is gradually coming back my way. Nothing is better than freedom, a high hill and water into which one may fall without hurting oneself.

Maxim's airplane according to your sketch, represents the infancy of the art. It is one of the many dirigible parachutes. I never have been very successful with this type of machine which I have tried out many times, even recently. The control requires excessive and constant attention. Furthermore the load is placed too far from the carrying surface causing terrific swinging motions which take place once the speed decreases and these decreases are perpetual during flight. It is a parachute which, like any other parachute, oscillates the moment it starts to glide instead of dropping. It is a hundred thousand miles away from an airplane even from an imperfect one.

When he wants to improve his system he must shorten the lever [arm], then he gradually will arrive at the airplane quite naturally, where the load is supported by the entire body of the carrying surface.

You asked about how I recommend to vary the center of gravity. I have presented three methods. The first is described on page 250 and shown in figure 30. The method is correct provided two gasket rings are used, but I was never able to build it light enough. I have this machine at my place. It weighs 28 kilograms, but it should weigh half that much. It will be necessary to preserve the principle which is fine, since it is a copy of the structure of the large soaring birds: vultures, eagles, etc. however, it has to be much lighter. The only material I know of, which could be used is aluminum, but in view of its price I have to give up this idea. The second method is shown on the de Massin-Biot airplane. Here is its history in a few words: Mr. de Massin asked me in 1882 for my latest combination in order to put it into practice. I gave it to him and he started to build. Several months afterwards the revolution in Egypt broke out and I stayed with him for a month. Here I saw the finished airplane, but its weight was enormous, as far as I can remember it weighed 32 kilograms. He never gave it a real test, and later on let Mr. Biot of Paris have it. Biot made some changes which I am going to describe to you (see the photograph). He started out by moving the aviator's place toward the rear. This is a mistake! The load of an airplane must always be in front. As a result of this move he could not make use of the control sticks which you will notice on the front, and which I have marked by two pin holes. He replaced these sticks by two pieces of curved wood of which he takes hold. This change in itself is not bad as far as the problem of moving the wing tips forward or backward is concerned. But my control sticks produced an effect which he seemingly did not understand, and which was the main reason for their being just where they were, namely their ability to create horizontal control. Actually, by moving these sticks forward or backward vertical control is created, but when they are twisted by putting one across the other, they turn and so produce the possibility of horizontal control. These two bamboo sticks rested in iron sockets which enabled this motion. The torsion created the following effect: The bamboo sticks, instead of being straight were slightly curved. When in regular position the arc of their curve was in the plane of the wing. When, due to this torsion, one wing tip was raised, a plane was formed which was different than that of the rest of the wing which remained in its original position. The latter produced horizontal control.

By this simple suppression it is deprived of one of the two directions, as shown in the photograph, and the airplane can be made to ascend and descend at will by moving the wing tips forward or backward, but it cannot be moved to the right or left. So Biot did not understand half of the mechanism which produces aviation. In spite of this basic imperfection he wrote me that he flew his plane, this may be so, but he never informed me that he had renewed his attempts. Moreover this machine was a copy of the structure of large soaring birds, it operates on about the same principle as the previous one. On both the displacement of the wing tips, though the manners of actuation differed, produced the same results of horizontal control. This control which is not presented in L'Empire de l'Air, fig. 30, see the missing space and let us admit it, for the very good reason of a reservation which I have charged to my credit: a mistake on my part which makes the airplane incomplete. Because the action of the displacement of the aviator is insufficient as I have stated in the chapter "Horizontal Control" of Vol sans Battement and described in the artificially created plane by means of the torsion of curved bamboo sticks on the Massin Biot airplane.

The method which I explain in Vol sans Battement which is the latest one developed and consequently the one I recommend because of the facility of light construction is a copy of another bird type. It is the reproduction of the structure: swift, swallow, frigate bird. The wings are shown singly though there are two. Both directions are a complete action. See chapter "Airplanes" of Vol sans Battement, and you will find there all necessary construction details.

This is the method which must be tried out. The delicate points are the harness and the equilibrium of the tension of the rubber bands. Build it with a surface as large as possible. The size will be indicated by the characteristics of the materials you use. If you have aluminum, use it, instead of bamboo, for similar conical tubes. If there is a proper solder actually available, which I do not know, fig. 1 could be produced by means of soldering a bent rod at the points A and B. If not, rivets may be used as shown in fig. 2.

Pg.51 Fig. 1 and Pg.51 Fig.2

I have touched aluminum twice. On a small scale I have some trinkets of this metal; it is as resistant as iron and light as porcelain. It is the metal for aviation. I also have seen it in Paris at the Aluminum Co. There I have weighed large pieces. Their weight is extraordinary light. One is conformed when one lifts them. And to think that I have not been able to make use of this marvel: 80 or 120 francs per kilogram, I do not remember exactly which. This is the only disadvantage of this metal. The Aluminum Co. buys it back at approximately the same price, provided it has not been soldered. Nothing is easier for them than to cut down the price if one wants to resell it. In case you have no bamboo on hand, I cannot recommend this metal too highly to you. The two control surfaces of the airplane which are the principal parts, would not weigh more than 5 kilograms or 2.5 kilograms each at 14 meters for both. It could be built completely with less than 10 kilograms of aluminum. The weight of the silk covering is negligible. No matter which method of construction you employ, try the airplane, before finishing it under the load of the aviator. Then, when you are satisfied with the lifting power and you have the airplane completed, investigate the effect due to the weight of the operator on the carrying surface, before testing the machine. For this purpose I refer you to the paragraph "Form of the airplane under pressure" which I recommend you to make use of, to enable you to arrive at something important in the carrying surface.

• These machines fly without flapping wings but rather with rigid wings.
• I never heard it said that one had dared to apply for a patent on a rigid airplane; i.e., one which is unable to beat the air with its wings. It is up to you, dear Sir, to judge this case. It is a protective measure to patent this theory before it is published. I do not believe that the fact that I was the father of this idea will be disputed.

• It's too hot to think clearly (42° C) and I'm tired.
• I'm thinking about the high-speed railroad.
• I am not going to send my book in this mail; I have to read it again and make some corrections.