After the trials at Kitty Hawk of their 1909 glider, designed with knowledge gained from their wind-tunnel experiments, the Wrights felt sure they could fly a power machine. There were delays in getting the new machine ready, partly because they had to build their own engine, since none that they could buy seemed suitable. Another problem was propellers. The brothers had assumed that they could learn all they needed about the theory of propellers from books on marine engineering, and then substitute air pressures for water pressures. But when they began to read such books, they discovered that, though strew propellers had been in use for a century, surprisingly little was known about them.
A majority of the earlier letters from the Wrights were written by Wilbur, for a reason given in the letter that follows. But Orville could express himself equally well. For a time many letters went to George Spratt, a young man in Pennsylvania, much interested in aeronautical problems, who had visited the Wrights at Kitty Hawk.
ORVILLE WRIGHT TO GEORGE A. SPRATT
DAYTON, OHIO, June 7, 1908
While I am aware that the shock of receiving a letter from me is apt to bring on a fit, yet I assure you that my writing is with no "design" on your life, which you mention in your letter to Wilbur.
We both take great interest in your letters, and my not writing to you is not from a lack of interest in what you are doing, but rather from a lack of ability as a letter writer. Will seems to enjoy writing, so I leave all the literary part of our work to him. Bul I see that he has failed to make you understand exactly what our ideas are on some of the points that have been under discussion.
[The next part of the letter was devoted to highly technical discussion of air pressures.]
I will drop the argumentative a while to tell you of what has been going on since we last met in Kitty Hawk. Immediately after our return we began the construction of a new testing apparatus for measuring the effects of wind at various angles on surfaces. After almost completing the machine, we discovered that we would have to have a very large room in which to operate it, as the current in our tunnel would be stronger on one side and then on the other, according to the course taken by the in returning to our fan. Consequently we were compelled to lay the whole matter aside until we ar able to find a more favorable place for operating. We may take it to Kitty Hawk.
We next began the designing of ribs, spars, etc., for our next machine, on which we had decided to put a motor with propellers. We had already before leaving Kitty Hawk about 'decided' on many of the points of construction, but it takes considerable figuring to determine the proper size of the different parts so as to maintain a high enough factor of safety in so large a machine.
We are going to make the surfaces 40 x 6 feet, 6 and a half feet apart...
Our curvature of surface will be about one in twenty, probably not as easy in control as the shape used last year, but of better lifting capacity. We are greatly increasing the size of the front rudder so as to have an abundance of control anyway. About Christmas time we began the construction of the motor, which is of four cylinders, 4-inch bore and 4-nch stroke. We had estimated that we would require a little over 8 horsepower to carry our weight of 625 pounds of machine and man. Our motor on completion turned out a very pleasant surprise. Instead of 8 horsepower, for which we hoped but hardly expected, it has given us 13 horsepower on the brake, with a weight of only 150 pounds in the motor. During the time the engine was building we were engaged in some very heated discussions on the principles of screw propellers. We had been unable to find anything of value in any of the works to which we had access, so that we worked out a theory of our own on the subject, and soon discovered, as we usually do, that all the propellers built heretofore are all wrong, and then built a pair of propellers 8 and an eight feet in diameter, based on our theory, which are all right! (till we have a chance to test them down at Kitty Hawk and find out differently). Isn't it astonishing that all these secrets have been preserved for so many years just so that we could discover them!! Well, our propellers are so different from any that have been used before that they will have to either be a good deal better or a good deal worse.
We have also made some experiments on the best shapes for the uprights of our machine, and again found out that everybody but ourselves is very badly mistaken!!! We simply tested the shapes here illustrated for the purpose of finding which was the best; exact measurements or ratios of resistance in the various shapes were not made, and the figures I give are only approximations. The "fair" or fish shape, like that recommended by Mr. Chanute, did not give as good results as that of the piece with the corners simply rounded. Mr. Chanute seems to very seriously doubt the accuracy of our measurements, as do some others who have made measurements along the same line. We are building our new uprights with simply rounded corners, nevertheless. We are going to have the chance to learn a whole lot of things when we get to Kitty Hawk this year, maybe very much to our sorrow. By the way, I will state that you will receive an invitation as soon as we determine our time of going, to visit us again at camp...
The theories you advance on the effects of straight winds on curved surfaces, and of curved winds on straight surfaces or planes, seem very original and interesting. I hope that you will have more time to carry on your experiments, and to develop these ideas to their fullest extent. You doubtless will make some mistakes, just as we do, and just as everybody else does, but if we all worked on the assumption that what is accepted as true is really true, there would be little hope of advance.
P.S. Please do not mention the fact of our building a power machine to anybody. The newspapers would take great delight in following us in order to record our troubles.
Almost as important as their research on wing curvatures and their method of control was the Wrights' work on propellers. They were the first to be able to calculate accurately in advance a screw propeller's performance.
WILBUR WRIGHT TO OCTAVE CHANUTE
DAYTON, June 18, 1903
The papers on screws [propellers], by various writers, do not seem to me of very much value. The chapter in the French book of Andre which is devoted to screws seems about as good as anything, but the final conclusion is that very little is known of the action of screws in motion forward. The action of screws not moving forward presents a very different case, and experiments based on such conditions are not applicable to the conditions met in practical flying.. Some of the writers see that running forward introduces new conditions but they do not seem to have any very definite ideas as to the amount and nature of the differences. We think we have a method of figuring a screw in action but of course it is all mere theory as yet. We will know more about its correctness when we have had a chance to try it.
At Kitty Hawk, when Spratt was the Wrights' guest, they had many arguments and discussions about technical questions, and some of these arguments were continued in letters.
ORVILLE WRIGHT TO GEORGE A. SPRATT
DAYTON, June 8, 1905
Your letter of the 12th was received some days ago, and has been read over a number of times by Wilbur and myself. Your speaking of knocking the props out from under us and allowing us to come up to your way of thinking reminds me of a new flying machine which Mr. Chanute saw in Europe. It was built to run along on some long legs or stilts until it has attained a pretty good speed, when it kicks its own legs out from under itself and allows itself to rise. However, I guess our props are stuck pretty well down into the mud, for we do not feel them giving under us much.
We made up several styles of ribs before adopting our present method of making them, but found nothing more satisfactory than the one I described to you. Those with holes bored in them, like you mentioned, we found to be heavier for the same strength. We wrap the ribs at all places where blocks are put in with glued paper, which adds greatly to the strength. Since putting in heavier springs to actuate the valves on our engine we have increased its power to nearly 16 horsepower, and at the same time reduced the amount of gasoline consumed per hour to about one half of what it was before.
You were inquiring, some time ago, about Langley's Experiments in Aerodynamics. We do not think it would pay you to buy this. In fact, we place very little confidence in the work. Lilienthal's Der Vogelflug, Chanute's Progress in Flying Machines, and the Aeronautical Annuals of 1896 and 1897 contain most of what has been published that is of much value.
We cannot tell with any certainty yet as to when we will be ready to go to Kitty Hawk, but we are hoping to be off about the middle of August. The motor greatly complicates the difficulties of building. We find it no easy matter to convey 16 horsepower from the motor to the two propellers. A French army officer has been very anxious to visit us at Kitty Hawk this year, but knowing that we will have much more work this year than heretofore, we do not feel that we ought to try any new visitors. We are collecting a whole lot of material for argument in camp, and hope to give you a good time when you meet us there.
Letters began to come to the Wrights from Captain Louis F. Ferber of the French Army, who had made gliding experiments as a hobby while serving in an Alpine artillery corps. As early as 1901 he had written to Octave Chanute about the Wrights, after reading of their experiments. He called himself a disciple of the Wrights.
WILBUR WRIGHT TO OCTAVE CHANUTE
DAYTON, July 2, 1903
What you have written to Captain Ferber will probably be a sufficient hint that for the present we would prefer to carry on our experiments undisturbed.
The method we employ in securing lateral equilibrium is of a somewhat complex nature, and unless a very minute description of the structure and theory of operation is given, there is danger to novices in attempting to use it, Both Orville and myself had trouble in our early experiments last year and it is our belief that beginners will be much safer on a machine without tail, and with the lateral balance secured by slightly shifting weight just as in our 1900 and 1901 machines. It is not our wish that any description of this feature of our machine be given at present. Beginners should he cautioned to use machines of less than a 20-foot spread from tip to tip, and to learn the longitudinal control thouroughly before attempting to use large machines and complex methods of operation. One thing at a time is the safe rule...
Professor Langley seems to be having rather more than his fair share of trouble just now with pestiferous reporters and wind storms. But as the mosquitoes are reported to be very bad along banks where the reporters are encamped he has some consolation. It would be interesting to attempt a computation of the possible performance of his machine in advance of its trial, but the data of the machine as given in the newspapers are so evidently erroneous that it seems hopeless to attempt it. It is a sure thing that the speed will not be from 60 to 90 miles an hour with an expenditure of 25 horsepower as the papers have reported its prospective flight. I presume that you are to be one the guests of honor at the launching festivities. has not yet arrived. Our invitation has not yet arrived.
WILBUR WRIGHT TO OCTAVE CHANUTE
DAYTON, July 4, 1903
Your special delivery letter of 23rd inst. is at hand and I hasten to reply.
The vertical tail is operated by wires leading the wires which connect with the wing tips. Thus the movement of the wing tips operates the rudder. This statement is not for publication, but merely to correct the misapprehension in your own mind. As the laws of France and Germany provide that patents will be held invalid if the matter claimed has been publicly printed we prefer to exercise reasonable caution about the details of our machine until the question of patents is settled. I only see three methods of dealing with this matter: (1) Tell the truth. (2) Tell nothing specific. (3) Tell something not true. I really cannot advise either the first or the third course.
WILBUR WRIGHT TO OCTAVE CHANUTE
DAYTON, August 2, 1903
Your letters of 27th, 28th ult. are at hand. We thank you for striking out of your "Revue" article the sentence relating to steering. You have, however, entirely mistaken the ground to it. The trouble was not that it gave away our secrets, but that it attributed to us ancient methods which we do not use. We could not propose a substitute without going into matters we think it safest to keep out of print for the present. But for the fact that the article was submitted to us in advance of publication and might therefore be considered as approved by us, I should not have considered it necessary to mention any of the matters which I called attention to.
Captain Ferber need have no fears that we offended at his patriotism. If we had facilities for entertaining him, and nothing but gliding on the program, and four months instead of less than two in our season, he would have been very welcome.
Not until September 8, 1903, were the Wrights ready for their trip back to Kitty Hawk. They made good connections with a boat and arrived at Kitty Hawk two days after leaving home. Discussing en route what they hoped to accomplish, neither had the slightest doubt about flying their new power machine.
ORVILLE WRIGHT TO HIS SISTER
KITTY HAWK, N.C., October 4, 1903
These two days of gliding have made us much more expert in handling the machine, and on the next day we have 18 to 20 miles of wind we expect to go up and stay up for at least several minutes...
We haven't had but one newspaper since we came down here, so you see we are living in blissful ignorance... I bought this paper and envelopes in Norfolk as we came down. The young lady in the store recognized me at once as of the aristocracy, and so palmed off these envelopes without gum. As I will have to spend the next half hour heating up some tire cement to seal it I will have to close now.
WILBUR WRIGHT TO HIS FATHER
KITTY HAWK, October 4, 1908
We have increased our time for length of flight [with glider] to 43 seconds, which is 1 and two thirds over last year's record and about three times the best of any one else. We will soon have it up to more than a minute as we are now able to remain practically stationary when a suitable wind blows up a good slope. This is something former experimenters were entirely unable to accomplish.
WILBUR WRIGHT TO OCTAVE CHANTUTE
KITTY HAWK, October 16, 1903
We regret to learn that there is danger of your being unable to visit our camp this year. We are expecting the most interesting results of any of our seasons of experiments, and are sure that, barring exasperating little accidents or some mishap, we will have done something before we break camp...
I see that Langley has had his fling, and failed. It seems to be our turn to throw now, and I wonder what our luck will be.
Langley made one more attempt to fly his machine, but again was unsuccessful. Not until several years later, when the Langley machine was completely built, with vital changes based on discoveries by the Wrights, was it able to lift itself into the air for a short hop.
ORVILLE WRIGHT TO HIS SISTERAbout a week ago the weather turned very cold (about zero according to my backbone) and another rain set in which continued for several days without intermittence. We found that a fire was absolutely necessary, especially on account of Spratt, who suffers much from cold. We took one of the carbide cans and, after punching some holes in the bottom for air, built a fire in it inside the building. Of course the smoke was so intense that there was no standing up in the room, so we sat down on the floor about the can with tears streaming down our cheeks enjoying its kindly rays of heat. Everything about the building was sooted up so thoroughly that for several days we couldn't sit down to eat without a whole lot of black soot dropping down in our plates. We decided a change was necessary, so we got a little stove pipe and built a stove out of the can, adding strap iron legs to it, and a number of patent dampers, so that now we have about as good control in our stove as we have on our machine. We are now living in luxurious ease.
KITTY HAWK, November 1, 1908
Your asking that we telegraph after every storm would soon have us "busted" if complied with. We have been having an almost continuous succession of storms the past few weeks.
I suppose you have read in the papers the account of the failure of Langley's big machine. He started from a point 60 feet in the air and landed 300 feet away, which is a drop of 1 foot for every 5 forward. We are able, from this same height, to make from 400 to 600 feet without any motor at all, so that I think his surfaces must be very inefficient. They found they had no control of the machine whatever, though the wind blew but 5 miles an hour at the time of the test. That is the point where we have a great advantage. We have been in the air hundreds and hundreds of times, and have pretty well worked out the problem of control. We find it much more difficult to manage the machine when trying to soar in one spot than when traveling rapidly forward. We expect no trouble from our big machine at all in this respect. Of course we are going to thoroughly test the control of it on the hills before attaching the motor. We are highly pleased with our progress so far this year...
I have been putting in about an hour every night down here in studying German and am getting along pretty well.
ORVILLE WRIGHT TO HIS FATHER AND SISTER
KITTY HAWK, November 15, 1903
We are now alone again. The first time for about a month...
Mr. Chanute says that no one before has ever tried to build a machine on such close margins as we have done to our calculations. He said that he nevertheless had more hope of our machine going than any of the others. He seems to think we are pursued by a blind fate from vhich we are unable to escape. He has been trying to purchase the Ader machine built by the French government at an expense of $100,000, which he was intending to have us fix up and run for him. He thinks we could do it! He doesn't seem to think our machines are so much superior as the manner in which we handle them. We are of just the reverse opinion.
ORVILLE WRIGHT TO HIS FATHER AND SISTER
KITTY HAWK, November 19, 1903
Mr. Chanute brought several pictures of the Langley machine which have furnished us matter for a good deal of speculation. It would appear from what Mr. Chanute learned in Washington that the machine weighed 750 pounds and had a 50-horsepower engine. The weight is about the same as ours but the power—four times as much.
Judging from present prospects, it is probable that we will not be home before the first of next month. Of course we cannot tell what is going to happen when we try the engine and screws again, but if the propeller shafts stand up, I think the rest will. If we should succeed in making a flight, and telegraph, we will, expect Lorin as our press agent (!) to notify the papers and the Associated Press. Chanute was much surprised that none of the reporters had learned of our experiments. Langley told him that they nearly worried him to death. Will thought that our best chance of doing the bird act would be to get home before Thanksgiving, but that now seems hopeless, so we will try it here.
WILBUR WRIGHT TO HIS FAMILY
KITTY HAWK, November 3, 1903
Our track for starting the machine (total cost about $4) amused Mr. Chanute considerably, as Langley is said to have spent nearly $50,000 on his starting device, which failed in the end to give a proper start he claims. At least this is the reason he gives for the failure last month. We have only tried ours with the little machine, so far, but it seems to work well.
Noone was more keenly interested in what the Wrights were doing than their chief mechanic, Charles Taylor, at their bicycle shop in Dayton. He had given them enthusiastic help in building their engine.
ORVILLE WRIGHT TO CHARLES TAYLOR
KITTY HAWK, November 3, 1903
We thought that when we could get both propellers on, the shock would be divided between the two, but on the contrary we found the shock greatly increased on each. The jerking of the propellers back and forth would loosen up the sprockets in spite of all the tightening we could do...
We used a chain and a 6-foot 2 x 4 to tighten them and the nuts, but 10 seconds more run and they were loose again. We kept that up all Friday afternoon... The next morning, thanks to Arnstein's hard cement, which will fix anything from a stop watch to a thrashing machine, we stuck those sprockets so tight I doubt whether they will ever come loose again... When Mr. Chanute was here he said that from 25 to 30 per cent should be allowed for loss from transmission. As we had allowed but 10 to 15 per cent, we saw that the gears we have would not allow us to speed the engine up enough to get the thrust. However, the loss of transmission is not as much as we had calculated, or the power of the engine is more, for the propellers speeded up more than we had ever hoped for (standing still) but gave exactly the thrust we had calculated that it should give at this speed. We will not be ready for trial for several days yet on account of having decided some changes in the machine. Unless something breaks in the meantime we feel confident of success.
WILBUR WRIGHT TO HIS FAMILY
KITTY HAWK, December 14, 1903
We gave machine first trial today with only pairtial success. The wind was only about 5 miles an hour, so we anticipated difficulty in getting speed enough on our short track (60 ft.) to lift. We took to the hill and after tossing for first whack, which I won, got ready for the start. The wind was a little to one side and the track was not exactly straigh down hill, which caused the start to be more dficult than it would otherwise have been. However, the real trouble was an error in judgment in turning up too suddenly after leaving the track, and as the machine had barely speed enough for support already, this slowed it down so much that before I could correct the error, the machine began to come down, though turned up at a big angle.
Toward the end it began to speed up again but i was too late, and it struck the ground while moving a little to one side, due to wind and a rather bad start. A few sticks in the front rudder were broken which will take a day or two to repair probably. It was a nice easy landing for the operator. The machinery all worked in entirely satisfactory manner and seems reliable. The power is ample, and but for a trifling error due to lack of experience with the machine and this method of starting, the machim would undoubtedly have flown beautifully.
There is now no question of final success. The strength of the machine is all right, the trouble in the front rudder being easily remedied. We anticipate no further trouble in landings. Will probably have made another trial before you receive this unless weather is unfavorable.
On December 15, the day after the first try of the power machine, a little short of success, Orville Wright sent a telegram to his father:—