FRENCH DIRIGIBLESThe First Lebaudy.The interest evidenced by the German War Department in Zeppelin’s airship was more than duplicated by that aroused in French military circles by the success of the Lebaudy Brothers. Since 1900 these two brothers had been experimenting with dirigible balloons. Their first dirigible—built by the engineer Juillot—made thirty flights, in all but two of which it succeeded in returning to its starting point. This machine was somewhat similar to the later types built by Santos-Dumont and carried a 40-horsepower Daimler motor. A speed of 36 feet per second, or about 25 miles per hour, was obtained. During tests in the summer of 1904, the balloon was dashed against a tree and almost entirely destroyed.Lebaudy 1904.The next year the "Lebaudy 1904" appeared. This was 190 feet long and had a capacity of 94,000 cubic feet of gas. The air bag was divided into three parts and contained 17,600 cubic feet of air. It was supplied with air from a fan driven by the engine, and an auxiliary electric motor and storage battery were carried to drive the fan when the gas engine was not working. The storage battery was also used to furnish electric lights for the airship. A horizontal sail of silk was stretched between the car and the gas bag, which had an area of something over 1,000 square feet, and a sort of keel of silk was stretched below it. A horizontal rudder, shaped like a pigeon’s tail, was used at the rear, and immediately behind it were two V-shaped vertical rudders. A small vertical sail was carried, which could be used to assist in guiding the airship. The car was 16 feet long and was rigidly hung 10 feet below the bag. It was provided with an inverted pyramid of steel tubes meeting at an apex below the car to prevent injury in alighting. Sixty-three ascents were made in 1904 with this balloon, all of them comparatively successful, the longest being a journey of 60 miles in two hours and forty-five minutes.Fig. 9. La Patrie, French War DirigibleFig. 9. La Patrie, French War DirigibleThe next year a new and larger balloon equipped with a more powerful motor was used. Many flights were made in tests for the French War Department.La Patrie.La Patrie was then built for the French government by the Lebaudy Brothers and was of the same design as their earlier airships. In speed it was nearly equal to Zeppelin’s, and its dirigibility was nearly perfect. Fig. 9 shows a view of this airship in flight.It was 200 feet long, and the 70-horsepower engine drove two propellers. It could carry seven people and one-half ton of ballast. It carried four people at a speed of 30 miles per hour. On its last trip it covered 175 miles in seven hours. A few days afterward, a heavy wind tore it away from its moorings and it was blown out to sea and lost.La Republique and Le Jaune.Two more airships of the same type, La Republique and Le Jaune, followed this. These were tried by the French government, in 1908, and both proved successful. La Republique is illustrated in Fig. 10. The shape and equipment of the car are shown in Fig. 11. The automobile type of radiator may be seen attached to the side of the car. During a flight in the fall of 1909, a propeller blade broke and was thrown clear through the balloon envelope, causing the balloon to fall from a height of 500 feet. The four officers who formed the crew of the dirigible were killed instantly.Clement-Bayard II.The numerous factors that must be considered in the design of a successful dirigible balloon as well as the many conflicting conditions that must be reconciled have already been referred to in detail. How these are carried out in practice may best be made clear by a description of what may be considered as an advanced type of dirigible, the Clement-Bayard II, Fig. 12, of French design, and the most successful of the French military air fleet. Its predecessor, the Clement-Bayard I, Fig. 13, made thirty voyages, some of them of considerable distances, without suffering any damage, but a study of its shortcomings led to their elimination in the following model.Fig. 10. La Republique, French War DirigibleFig. 10. La Republique, French War DirigibleFig. 11. Car of La RepubliqueFig. 11. Car of La RepubliqueThe pisciform shape of the first Clement-Bayard was retained but given more taper, the dimensions being 248.6 feet overall by 42.9 greatest diameter, this being but a short distance back of the bow. This gives it a ratio of length to diameter of 5.76. The gas balloonet stabilizers were eliminated altogether, Fig. 12. The total gas capacity is approximately 80,000 cubic feet. Like all French dirigibles it is of the true flexible type, the only rigid construction being that of the framework of the car itself. To the latter are attached all rudders and stabilizing devices, instead of making them a part of the envelope as formerly. The latter is made of continental rubber cloth.Fig. 12. Clement-Bayard II, French DirigibleFig. 12. Clement-Bayard II, French DirigibleLight steel and aluminum tubing are employed in the construction of the frame supplemented by numerous piano-wire stays. This frame extends almost the entire length of the envelope and carries at its rear end a cellular, or box-kite, type of stabilizing rudder, instead of the former gas balloonets employed on the Clement-Bayard I, Fig. 13. This cellular rudder is in two parts, consisting of two units of four cells each, the two groups being joined at the top, with a space between them. In addition to acting as a stabilizer, this is also the direction rudder, its leverage being increased by making the end planes somewhat larger than the partitions of the cells. Between the cellular stabilizing rudder and the envelope is placed the horizontal rudder for ascending or descending. In the illustration this appears to be a flag, but it is in reality a long rectangular plane, which may be tilted on its longitudinal axis, the latter being at right angles to that of the balloon. There are two air balloonets of about one-third the total capacity of the balloon itself, and they are designed to be inflated by large aluminum centrifugal blowers driven from the main engines themselves.Fig. 13. Clement-Bayard IFig. 13. Clement-Bayard IThere are two motors, each of 125 horsepower, both being of the same conventional design,i.e., four cylinder four cycle vertical water cooled. In fact, they are merely light automobile motors. The cylinders have separate copper water jackets and the motors themselves are muffled, which is a departure from the usual custom. Each drives a separate propeller carried on top of the main frame through bevel gearing.The Clement-Bayard II made itself famous by its rapid and successful flight from the suburbs of Paris across the Channel to London, in October, 1910.Astra-Torres.In reviewing the specifications of any of the big dirigibles, the observer cannot fail to be struck by the excessive amount of power necessary to drive them at speeds which are lower than the minimum, or landing speeds, of many aeroplanes. When a speed of 45 miles per hour was first reached by a dirigible, it was acclaimed as a great feat. But this comparatively moderate rate of travel was surpassed only by increasing the number of motors and their horsepower until the fuel consumption became exceedingly high. This necessitated the carrying of a great weight of fuel and cut down correspondingly the useful load that the dirigible was capable of lifting as well as restricted its radius of flight at full speed. Until aerodynamic research had demonstrated the contrary, the necessity for such a tremendous amount of power was considered necessary to overcome the head resistance of the balloon itself. Research brought out in a striking manner how great a proportion of the total head resistance of an aeroplane was due to the struts and bracing wires. In the construction of the different types of airships illustrated, it will be noted that the gear provided for suspending the car or cars below the balloon requires a great number of cables. Later developments showed that by eliminating the great amount of head resistance caused by these numerous surfaces, the speed of a dirigible could be increased by over 50 per cent with the same amount of power.Fig. 14. Section of Astra-Torres, Illustrating Method of Suspension.Fig. 14. Section of Astra-Torres, Illustrating Method of Suspension.CB, Bracing of Heavy Fabric Bands;SRandA, Suspension Ropes and Cable Passing through Envelope;S, Expansion Sleeve in Envelope;CC', Ropes to Sides of Car;E, EnvelopeImproved Suspension.The shortcoming of the dirigible with reference to suspension was realized more than ten years previous by a Spaniard—Torres—but owing to lack of financial support, he was unable to put his idea into execution. The principle he evolved is made clear by Fig. 14, which gives a section of an Astra-Torres dirigible illustrating the method of suspension. Instead of the ropesSRused to suspend the car being attached to bands passing around the envelope, these reinforcing bandsCBand also the ropes fastened to them are placed inside the envelope, thus eliminating head resistance from those sources.Performance.Failing to obtain any encouragement in Spain, Torres finally succeeded in interesting the French Astra Company, which built a vedette, or scouting airship, of a little over 50,000 cubic feet capacity. It was pitted against the Colonel Renard, at that time the leading unit in the French aerial navy and the fastest airship in commission. The small Torres dirigible so completely outclassed its huge competitor that another of close to 300,000 cubic feet capacity was built and tried against the Parseval with similar results. An Astra-Torres dirigible built for the British government showed a speed in excess of 50 miles per hour. This particular dirigible has been at the front in France almost since the outbreak of hostilities and has rendered considerable valuable service. Its success led the French Government to order a huge replica of it, having a capacity of over 800,000 cubic feet and with motors developing 1,000 horsepower, which would give it an indicated speed of 60 miles per hour. So confident were its builders of attaining or even exceeding this, that an order for a second and even larger airship of the Astra-Torres design was placed before the first one was finished. This is also fitted with motors aggregating 1,000 horsepower and displaces 38 tons, making it larger than any Zeppelin that had been constructed up to the time it was built. As its construction and trials were undertaken during the war, no details have been published, but it is said on good authority that its speed exceeds 60 miles per hour, so that it is faster than any of the German dirigibles.Construction.Unlike the German dirigibles, the larger types of which have been characterized by a rigid frame, the Astra-Torres is a flexible airship and, owing to its method of suspension, its external appearance is decidedly unconventional, since the envelope instead of being of the usual cigar shape is more like a triangular bundle of three cigars with the third one on top. At the point where the three envelopes join, as shown in section, Fig. 14, heavy cloth bandsCBare stretched across the arcs, forming a chord across each arc, the three chords comprising an inverted triangle. The suspension ropesSRare attached to the opposite ends of the base of this inverted triangle and converge in straight lines downward through the gas space, so that the air resistance offered by the ropes is practically eliminated since only a very small part of the suspension system appears outside the envelope. This external part consists of vertical cablesAattached to the collecting rings of the bracing system and extending downward through special accordion sleevesSwhich permit the free play necessary at the points where they pass through the outer wall of the envelope. These sleeves also have another function—that of permitting the escape of gas under the pressure of expansion. A short distance below the envelopeEeach of these cables splits into two partsCandC'attached to opposite sides of the car.The British airship mentioned is provided with but one car, but the larger French ships have two placed tandem, each of which carries a 500-horsepower motor driving two two-bladed propellers of large diameter. While the form of envelope made necessary by this construction increases the frictional resistance, this is negligible in comparison with the great saving in power effected by the method of suspension, not to mention the greater simplicity of construction.
FRENCH DIRIGIBLESThe First Lebaudy.The interest evidenced by the German War Department in Zeppelin’s airship was more than duplicated by that aroused in French military circles by the success of the Lebaudy Brothers. Since 1900 these two brothers had been experimenting with dirigible balloons. Their first dirigible—built by the engineer Juillot—made thirty flights, in all but two of which it succeeded in returning to its starting point. This machine was somewhat similar to the later types built by Santos-Dumont and carried a 40-horsepower Daimler motor. A speed of 36 feet per second, or about 25 miles per hour, was obtained. During tests in the summer of 1904, the balloon was dashed against a tree and almost entirely destroyed.Lebaudy 1904.The next year the "Lebaudy 1904" appeared. This was 190 feet long and had a capacity of 94,000 cubic feet of gas. The air bag was divided into three parts and contained 17,600 cubic feet of air. It was supplied with air from a fan driven by the engine, and an auxiliary electric motor and storage battery were carried to drive the fan when the gas engine was not working. The storage battery was also used to furnish electric lights for the airship. A horizontal sail of silk was stretched between the car and the gas bag, which had an area of something over 1,000 square feet, and a sort of keel of silk was stretched below it. A horizontal rudder, shaped like a pigeon’s tail, was used at the rear, and immediately behind it were two V-shaped vertical rudders. A small vertical sail was carried, which could be used to assist in guiding the airship. The car was 16 feet long and was rigidly hung 10 feet below the bag. It was provided with an inverted pyramid of steel tubes meeting at an apex below the car to prevent injury in alighting. Sixty-three ascents were made in 1904 with this balloon, all of them comparatively successful, the longest being a journey of 60 miles in two hours and forty-five minutes.Fig. 9. La Patrie, French War DirigibleFig. 9. La Patrie, French War DirigibleThe next year a new and larger balloon equipped with a more powerful motor was used. Many flights were made in tests for the French War Department.La Patrie.La Patrie was then built for the French government by the Lebaudy Brothers and was of the same design as their earlier airships. In speed it was nearly equal to Zeppelin’s, and its dirigibility was nearly perfect. Fig. 9 shows a view of this airship in flight.It was 200 feet long, and the 70-horsepower engine drove two propellers. It could carry seven people and one-half ton of ballast. It carried four people at a speed of 30 miles per hour. On its last trip it covered 175 miles in seven hours. A few days afterward, a heavy wind tore it away from its moorings and it was blown out to sea and lost.La Republique and Le Jaune.Two more airships of the same type, La Republique and Le Jaune, followed this. These were tried by the French government, in 1908, and both proved successful. La Republique is illustrated in Fig. 10. The shape and equipment of the car are shown in Fig. 11. The automobile type of radiator may be seen attached to the side of the car. During a flight in the fall of 1909, a propeller blade broke and was thrown clear through the balloon envelope, causing the balloon to fall from a height of 500 feet. The four officers who formed the crew of the dirigible were killed instantly.Clement-Bayard II.The numerous factors that must be considered in the design of a successful dirigible balloon as well as the many conflicting conditions that must be reconciled have already been referred to in detail. How these are carried out in practice may best be made clear by a description of what may be considered as an advanced type of dirigible, the Clement-Bayard II, Fig. 12, of French design, and the most successful of the French military air fleet. Its predecessor, the Clement-Bayard I, Fig. 13, made thirty voyages, some of them of considerable distances, without suffering any damage, but a study of its shortcomings led to their elimination in the following model.Fig. 10. La Republique, French War DirigibleFig. 10. La Republique, French War DirigibleFig. 11. Car of La RepubliqueFig. 11. Car of La RepubliqueThe pisciform shape of the first Clement-Bayard was retained but given more taper, the dimensions being 248.6 feet overall by 42.9 greatest diameter, this being but a short distance back of the bow. This gives it a ratio of length to diameter of 5.76. The gas balloonet stabilizers were eliminated altogether, Fig. 12. The total gas capacity is approximately 80,000 cubic feet. Like all French dirigibles it is of the true flexible type, the only rigid construction being that of the framework of the car itself. To the latter are attached all rudders and stabilizing devices, instead of making them a part of the envelope as formerly. The latter is made of continental rubber cloth.Fig. 12. Clement-Bayard II, French DirigibleFig. 12. Clement-Bayard II, French DirigibleLight steel and aluminum tubing are employed in the construction of the frame supplemented by numerous piano-wire stays. This frame extends almost the entire length of the envelope and carries at its rear end a cellular, or box-kite, type of stabilizing rudder, instead of the former gas balloonets employed on the Clement-Bayard I, Fig. 13. This cellular rudder is in two parts, consisting of two units of four cells each, the two groups being joined at the top, with a space between them. In addition to acting as a stabilizer, this is also the direction rudder, its leverage being increased by making the end planes somewhat larger than the partitions of the cells. Between the cellular stabilizing rudder and the envelope is placed the horizontal rudder for ascending or descending. In the illustration this appears to be a flag, but it is in reality a long rectangular plane, which may be tilted on its longitudinal axis, the latter being at right angles to that of the balloon. There are two air balloonets of about one-third the total capacity of the balloon itself, and they are designed to be inflated by large aluminum centrifugal blowers driven from the main engines themselves.Fig. 13. Clement-Bayard IFig. 13. Clement-Bayard IThere are two motors, each of 125 horsepower, both being of the same conventional design,i.e., four cylinder four cycle vertical water cooled. In fact, they are merely light automobile motors. The cylinders have separate copper water jackets and the motors themselves are muffled, which is a departure from the usual custom. Each drives a separate propeller carried on top of the main frame through bevel gearing.The Clement-Bayard II made itself famous by its rapid and successful flight from the suburbs of Paris across the Channel to London, in October, 1910.Astra-Torres.In reviewing the specifications of any of the big dirigibles, the observer cannot fail to be struck by the excessive amount of power necessary to drive them at speeds which are lower than the minimum, or landing speeds, of many aeroplanes. When a speed of 45 miles per hour was first reached by a dirigible, it was acclaimed as a great feat. But this comparatively moderate rate of travel was surpassed only by increasing the number of motors and their horsepower until the fuel consumption became exceedingly high. This necessitated the carrying of a great weight of fuel and cut down correspondingly the useful load that the dirigible was capable of lifting as well as restricted its radius of flight at full speed. Until aerodynamic research had demonstrated the contrary, the necessity for such a tremendous amount of power was considered necessary to overcome the head resistance of the balloon itself. Research brought out in a striking manner how great a proportion of the total head resistance of an aeroplane was due to the struts and bracing wires. In the construction of the different types of airships illustrated, it will be noted that the gear provided for suspending the car or cars below the balloon requires a great number of cables. Later developments showed that by eliminating the great amount of head resistance caused by these numerous surfaces, the speed of a dirigible could be increased by over 50 per cent with the same amount of power.Fig. 14. Section of Astra-Torres, Illustrating Method of Suspension.Fig. 14. Section of Astra-Torres, Illustrating Method of Suspension.CB, Bracing of Heavy Fabric Bands;SRandA, Suspension Ropes and Cable Passing through Envelope;S, Expansion Sleeve in Envelope;CC', Ropes to Sides of Car;E, EnvelopeImproved Suspension.The shortcoming of the dirigible with reference to suspension was realized more than ten years previous by a Spaniard—Torres—but owing to lack of financial support, he was unable to put his idea into execution. The principle he evolved is made clear by Fig. 14, which gives a section of an Astra-Torres dirigible illustrating the method of suspension. Instead of the ropesSRused to suspend the car being attached to bands passing around the envelope, these reinforcing bandsCBand also the ropes fastened to them are placed inside the envelope, thus eliminating head resistance from those sources.Performance.Failing to obtain any encouragement in Spain, Torres finally succeeded in interesting the French Astra Company, which built a vedette, or scouting airship, of a little over 50,000 cubic feet capacity. It was pitted against the Colonel Renard, at that time the leading unit in the French aerial navy and the fastest airship in commission. The small Torres dirigible so completely outclassed its huge competitor that another of close to 300,000 cubic feet capacity was built and tried against the Parseval with similar results. An Astra-Torres dirigible built for the British government showed a speed in excess of 50 miles per hour. This particular dirigible has been at the front in France almost since the outbreak of hostilities and has rendered considerable valuable service. Its success led the French Government to order a huge replica of it, having a capacity of over 800,000 cubic feet and with motors developing 1,000 horsepower, which would give it an indicated speed of 60 miles per hour. So confident were its builders of attaining or even exceeding this, that an order for a second and even larger airship of the Astra-Torres design was placed before the first one was finished. This is also fitted with motors aggregating 1,000 horsepower and displaces 38 tons, making it larger than any Zeppelin that had been constructed up to the time it was built. As its construction and trials were undertaken during the war, no details have been published, but it is said on good authority that its speed exceeds 60 miles per hour, so that it is faster than any of the German dirigibles.Construction.Unlike the German dirigibles, the larger types of which have been characterized by a rigid frame, the Astra-Torres is a flexible airship and, owing to its method of suspension, its external appearance is decidedly unconventional, since the envelope instead of being of the usual cigar shape is more like a triangular bundle of three cigars with the third one on top. At the point where the three envelopes join, as shown in section, Fig. 14, heavy cloth bandsCBare stretched across the arcs, forming a chord across each arc, the three chords comprising an inverted triangle. The suspension ropesSRare attached to the opposite ends of the base of this inverted triangle and converge in straight lines downward through the gas space, so that the air resistance offered by the ropes is practically eliminated since only a very small part of the suspension system appears outside the envelope. This external part consists of vertical cablesAattached to the collecting rings of the bracing system and extending downward through special accordion sleevesSwhich permit the free play necessary at the points where they pass through the outer wall of the envelope. These sleeves also have another function—that of permitting the escape of gas under the pressure of expansion. A short distance below the envelopeEeach of these cables splits into two partsCandC'attached to opposite sides of the car.The British airship mentioned is provided with but one car, but the larger French ships have two placed tandem, each of which carries a 500-horsepower motor driving two two-bladed propellers of large diameter. While the form of envelope made necessary by this construction increases the frictional resistance, this is negligible in comparison with the great saving in power effected by the method of suspension, not to mention the greater simplicity of construction.
FRENCH DIRIGIBLESThe First Lebaudy.The interest evidenced by the German War Department in Zeppelin’s airship was more than duplicated by that aroused in French military circles by the success of the Lebaudy Brothers. Since 1900 these two brothers had been experimenting with dirigible balloons. Their first dirigible—built by the engineer Juillot—made thirty flights, in all but two of which it succeeded in returning to its starting point. This machine was somewhat similar to the later types built by Santos-Dumont and carried a 40-horsepower Daimler motor. A speed of 36 feet per second, or about 25 miles per hour, was obtained. During tests in the summer of 1904, the balloon was dashed against a tree and almost entirely destroyed.Lebaudy 1904.The next year the "Lebaudy 1904" appeared. This was 190 feet long and had a capacity of 94,000 cubic feet of gas. The air bag was divided into three parts and contained 17,600 cubic feet of air. It was supplied with air from a fan driven by the engine, and an auxiliary electric motor and storage battery were carried to drive the fan when the gas engine was not working. The storage battery was also used to furnish electric lights for the airship. A horizontal sail of silk was stretched between the car and the gas bag, which had an area of something over 1,000 square feet, and a sort of keel of silk was stretched below it. A horizontal rudder, shaped like a pigeon’s tail, was used at the rear, and immediately behind it were two V-shaped vertical rudders. A small vertical sail was carried, which could be used to assist in guiding the airship. The car was 16 feet long and was rigidly hung 10 feet below the bag. It was provided with an inverted pyramid of steel tubes meeting at an apex below the car to prevent injury in alighting. Sixty-three ascents were made in 1904 with this balloon, all of them comparatively successful, the longest being a journey of 60 miles in two hours and forty-five minutes.Fig. 9. La Patrie, French War DirigibleFig. 9. La Patrie, French War DirigibleThe next year a new and larger balloon equipped with a more powerful motor was used. Many flights were made in tests for the French War Department.La Patrie.La Patrie was then built for the French government by the Lebaudy Brothers and was of the same design as their earlier airships. In speed it was nearly equal to Zeppelin’s, and its dirigibility was nearly perfect. Fig. 9 shows a view of this airship in flight.It was 200 feet long, and the 70-horsepower engine drove two propellers. It could carry seven people and one-half ton of ballast. It carried four people at a speed of 30 miles per hour. On its last trip it covered 175 miles in seven hours. A few days afterward, a heavy wind tore it away from its moorings and it was blown out to sea and lost.La Republique and Le Jaune.Two more airships of the same type, La Republique and Le Jaune, followed this. These were tried by the French government, in 1908, and both proved successful. La Republique is illustrated in Fig. 10. The shape and equipment of the car are shown in Fig. 11. The automobile type of radiator may be seen attached to the side of the car. During a flight in the fall of 1909, a propeller blade broke and was thrown clear through the balloon envelope, causing the balloon to fall from a height of 500 feet. The four officers who formed the crew of the dirigible were killed instantly.Clement-Bayard II.The numerous factors that must be considered in the design of a successful dirigible balloon as well as the many conflicting conditions that must be reconciled have already been referred to in detail. How these are carried out in practice may best be made clear by a description of what may be considered as an advanced type of dirigible, the Clement-Bayard II, Fig. 12, of French design, and the most successful of the French military air fleet. Its predecessor, the Clement-Bayard I, Fig. 13, made thirty voyages, some of them of considerable distances, without suffering any damage, but a study of its shortcomings led to their elimination in the following model.Fig. 10. La Republique, French War DirigibleFig. 10. La Republique, French War DirigibleFig. 11. Car of La RepubliqueFig. 11. Car of La RepubliqueThe pisciform shape of the first Clement-Bayard was retained but given more taper, the dimensions being 248.6 feet overall by 42.9 greatest diameter, this being but a short distance back of the bow. This gives it a ratio of length to diameter of 5.76. The gas balloonet stabilizers were eliminated altogether, Fig. 12. The total gas capacity is approximately 80,000 cubic feet. Like all French dirigibles it is of the true flexible type, the only rigid construction being that of the framework of the car itself. To the latter are attached all rudders and stabilizing devices, instead of making them a part of the envelope as formerly. The latter is made of continental rubber cloth.Fig. 12. Clement-Bayard II, French DirigibleFig. 12. Clement-Bayard II, French DirigibleLight steel and aluminum tubing are employed in the construction of the frame supplemented by numerous piano-wire stays. This frame extends almost the entire length of the envelope and carries at its rear end a cellular, or box-kite, type of stabilizing rudder, instead of the former gas balloonets employed on the Clement-Bayard I, Fig. 13. This cellular rudder is in two parts, consisting of two units of four cells each, the two groups being joined at the top, with a space between them. In addition to acting as a stabilizer, this is also the direction rudder, its leverage being increased by making the end planes somewhat larger than the partitions of the cells. Between the cellular stabilizing rudder and the envelope is placed the horizontal rudder for ascending or descending. In the illustration this appears to be a flag, but it is in reality a long rectangular plane, which may be tilted on its longitudinal axis, the latter being at right angles to that of the balloon. There are two air balloonets of about one-third the total capacity of the balloon itself, and they are designed to be inflated by large aluminum centrifugal blowers driven from the main engines themselves.Fig. 13. Clement-Bayard IFig. 13. Clement-Bayard IThere are two motors, each of 125 horsepower, both being of the same conventional design,i.e., four cylinder four cycle vertical water cooled. In fact, they are merely light automobile motors. The cylinders have separate copper water jackets and the motors themselves are muffled, which is a departure from the usual custom. Each drives a separate propeller carried on top of the main frame through bevel gearing.The Clement-Bayard II made itself famous by its rapid and successful flight from the suburbs of Paris across the Channel to London, in October, 1910.Astra-Torres.In reviewing the specifications of any of the big dirigibles, the observer cannot fail to be struck by the excessive amount of power necessary to drive them at speeds which are lower than the minimum, or landing speeds, of many aeroplanes. When a speed of 45 miles per hour was first reached by a dirigible, it was acclaimed as a great feat. But this comparatively moderate rate of travel was surpassed only by increasing the number of motors and their horsepower until the fuel consumption became exceedingly high. This necessitated the carrying of a great weight of fuel and cut down correspondingly the useful load that the dirigible was capable of lifting as well as restricted its radius of flight at full speed. Until aerodynamic research had demonstrated the contrary, the necessity for such a tremendous amount of power was considered necessary to overcome the head resistance of the balloon itself. Research brought out in a striking manner how great a proportion of the total head resistance of an aeroplane was due to the struts and bracing wires. In the construction of the different types of airships illustrated, it will be noted that the gear provided for suspending the car or cars below the balloon requires a great number of cables. Later developments showed that by eliminating the great amount of head resistance caused by these numerous surfaces, the speed of a dirigible could be increased by over 50 per cent with the same amount of power.Fig. 14. Section of Astra-Torres, Illustrating Method of Suspension.Fig. 14. Section of Astra-Torres, Illustrating Method of Suspension.CB, Bracing of Heavy Fabric Bands;SRandA, Suspension Ropes and Cable Passing through Envelope;S, Expansion Sleeve in Envelope;CC', Ropes to Sides of Car;E, EnvelopeImproved Suspension.The shortcoming of the dirigible with reference to suspension was realized more than ten years previous by a Spaniard—Torres—but owing to lack of financial support, he was unable to put his idea into execution. The principle he evolved is made clear by Fig. 14, which gives a section of an Astra-Torres dirigible illustrating the method of suspension. Instead of the ropesSRused to suspend the car being attached to bands passing around the envelope, these reinforcing bandsCBand also the ropes fastened to them are placed inside the envelope, thus eliminating head resistance from those sources.Performance.Failing to obtain any encouragement in Spain, Torres finally succeeded in interesting the French Astra Company, which built a vedette, or scouting airship, of a little over 50,000 cubic feet capacity. It was pitted against the Colonel Renard, at that time the leading unit in the French aerial navy and the fastest airship in commission. The small Torres dirigible so completely outclassed its huge competitor that another of close to 300,000 cubic feet capacity was built and tried against the Parseval with similar results. An Astra-Torres dirigible built for the British government showed a speed in excess of 50 miles per hour. This particular dirigible has been at the front in France almost since the outbreak of hostilities and has rendered considerable valuable service. Its success led the French Government to order a huge replica of it, having a capacity of over 800,000 cubic feet and with motors developing 1,000 horsepower, which would give it an indicated speed of 60 miles per hour. So confident were its builders of attaining or even exceeding this, that an order for a second and even larger airship of the Astra-Torres design was placed before the first one was finished. This is also fitted with motors aggregating 1,000 horsepower and displaces 38 tons, making it larger than any Zeppelin that had been constructed up to the time it was built. As its construction and trials were undertaken during the war, no details have been published, but it is said on good authority that its speed exceeds 60 miles per hour, so that it is faster than any of the German dirigibles.Construction.Unlike the German dirigibles, the larger types of which have been characterized by a rigid frame, the Astra-Torres is a flexible airship and, owing to its method of suspension, its external appearance is decidedly unconventional, since the envelope instead of being of the usual cigar shape is more like a triangular bundle of three cigars with the third one on top. At the point where the three envelopes join, as shown in section, Fig. 14, heavy cloth bandsCBare stretched across the arcs, forming a chord across each arc, the three chords comprising an inverted triangle. The suspension ropesSRare attached to the opposite ends of the base of this inverted triangle and converge in straight lines downward through the gas space, so that the air resistance offered by the ropes is practically eliminated since only a very small part of the suspension system appears outside the envelope. This external part consists of vertical cablesAattached to the collecting rings of the bracing system and extending downward through special accordion sleevesSwhich permit the free play necessary at the points where they pass through the outer wall of the envelope. These sleeves also have another function—that of permitting the escape of gas under the pressure of expansion. A short distance below the envelopeEeach of these cables splits into two partsCandC'attached to opposite sides of the car.The British airship mentioned is provided with but one car, but the larger French ships have two placed tandem, each of which carries a 500-horsepower motor driving two two-bladed propellers of large diameter. While the form of envelope made necessary by this construction increases the frictional resistance, this is negligible in comparison with the great saving in power effected by the method of suspension, not to mention the greater simplicity of construction.
The First Lebaudy.The interest evidenced by the German War Department in Zeppelin’s airship was more than duplicated by that aroused in French military circles by the success of the Lebaudy Brothers. Since 1900 these two brothers had been experimenting with dirigible balloons. Their first dirigible—built by the engineer Juillot—made thirty flights, in all but two of which it succeeded in returning to its starting point. This machine was somewhat similar to the later types built by Santos-Dumont and carried a 40-horsepower Daimler motor. A speed of 36 feet per second, or about 25 miles per hour, was obtained. During tests in the summer of 1904, the balloon was dashed against a tree and almost entirely destroyed.
Lebaudy 1904.The next year the "Lebaudy 1904" appeared. This was 190 feet long and had a capacity of 94,000 cubic feet of gas. The air bag was divided into three parts and contained 17,600 cubic feet of air. It was supplied with air from a fan driven by the engine, and an auxiliary electric motor and storage battery were carried to drive the fan when the gas engine was not working. The storage battery was also used to furnish electric lights for the airship. A horizontal sail of silk was stretched between the car and the gas bag, which had an area of something over 1,000 square feet, and a sort of keel of silk was stretched below it. A horizontal rudder, shaped like a pigeon’s tail, was used at the rear, and immediately behind it were two V-shaped vertical rudders. A small vertical sail was carried, which could be used to assist in guiding the airship. The car was 16 feet long and was rigidly hung 10 feet below the bag. It was provided with an inverted pyramid of steel tubes meeting at an apex below the car to prevent injury in alighting. Sixty-three ascents were made in 1904 with this balloon, all of them comparatively successful, the longest being a journey of 60 miles in two hours and forty-five minutes.
Fig. 9. La Patrie, French War DirigibleFig. 9. La Patrie, French War Dirigible
Fig. 9. La Patrie, French War Dirigible
The next year a new and larger balloon equipped with a more powerful motor was used. Many flights were made in tests for the French War Department.
La Patrie.La Patrie was then built for the French government by the Lebaudy Brothers and was of the same design as their earlier airships. In speed it was nearly equal to Zeppelin’s, and its dirigibility was nearly perfect. Fig. 9 shows a view of this airship in flight.
It was 200 feet long, and the 70-horsepower engine drove two propellers. It could carry seven people and one-half ton of ballast. It carried four people at a speed of 30 miles per hour. On its last trip it covered 175 miles in seven hours. A few days afterward, a heavy wind tore it away from its moorings and it was blown out to sea and lost.
La Republique and Le Jaune.Two more airships of the same type, La Republique and Le Jaune, followed this. These were tried by the French government, in 1908, and both proved successful. La Republique is illustrated in Fig. 10. The shape and equipment of the car are shown in Fig. 11. The automobile type of radiator may be seen attached to the side of the car. During a flight in the fall of 1909, a propeller blade broke and was thrown clear through the balloon envelope, causing the balloon to fall from a height of 500 feet. The four officers who formed the crew of the dirigible were killed instantly.
Clement-Bayard II.The numerous factors that must be considered in the design of a successful dirigible balloon as well as the many conflicting conditions that must be reconciled have already been referred to in detail. How these are carried out in practice may best be made clear by a description of what may be considered as an advanced type of dirigible, the Clement-Bayard II, Fig. 12, of French design, and the most successful of the French military air fleet. Its predecessor, the Clement-Bayard I, Fig. 13, made thirty voyages, some of them of considerable distances, without suffering any damage, but a study of its shortcomings led to their elimination in the following model.
Fig. 10. La Republique, French War DirigibleFig. 10. La Republique, French War Dirigible
Fig. 10. La Republique, French War Dirigible
Fig. 11. Car of La RepubliqueFig. 11. Car of La Republique
Fig. 11. Car of La Republique
The pisciform shape of the first Clement-Bayard was retained but given more taper, the dimensions being 248.6 feet overall by 42.9 greatest diameter, this being but a short distance back of the bow. This gives it a ratio of length to diameter of 5.76. The gas balloonet stabilizers were eliminated altogether, Fig. 12. The total gas capacity is approximately 80,000 cubic feet. Like all French dirigibles it is of the true flexible type, the only rigid construction being that of the framework of the car itself. To the latter are attached all rudders and stabilizing devices, instead of making them a part of the envelope as formerly. The latter is made of continental rubber cloth.
Fig. 12. Clement-Bayard II, French DirigibleFig. 12. Clement-Bayard II, French Dirigible
Fig. 12. Clement-Bayard II, French Dirigible
Light steel and aluminum tubing are employed in the construction of the frame supplemented by numerous piano-wire stays. This frame extends almost the entire length of the envelope and carries at its rear end a cellular, or box-kite, type of stabilizing rudder, instead of the former gas balloonets employed on the Clement-Bayard I, Fig. 13. This cellular rudder is in two parts, consisting of two units of four cells each, the two groups being joined at the top, with a space between them. In addition to acting as a stabilizer, this is also the direction rudder, its leverage being increased by making the end planes somewhat larger than the partitions of the cells. Between the cellular stabilizing rudder and the envelope is placed the horizontal rudder for ascending or descending. In the illustration this appears to be a flag, but it is in reality a long rectangular plane, which may be tilted on its longitudinal axis, the latter being at right angles to that of the balloon. There are two air balloonets of about one-third the total capacity of the balloon itself, and they are designed to be inflated by large aluminum centrifugal blowers driven from the main engines themselves.
Fig. 13. Clement-Bayard IFig. 13. Clement-Bayard I
Fig. 13. Clement-Bayard I
There are two motors, each of 125 horsepower, both being of the same conventional design,i.e., four cylinder four cycle vertical water cooled. In fact, they are merely light automobile motors. The cylinders have separate copper water jackets and the motors themselves are muffled, which is a departure from the usual custom. Each drives a separate propeller carried on top of the main frame through bevel gearing.
The Clement-Bayard II made itself famous by its rapid and successful flight from the suburbs of Paris across the Channel to London, in October, 1910.
Astra-Torres.In reviewing the specifications of any of the big dirigibles, the observer cannot fail to be struck by the excessive amount of power necessary to drive them at speeds which are lower than the minimum, or landing speeds, of many aeroplanes. When a speed of 45 miles per hour was first reached by a dirigible, it was acclaimed as a great feat. But this comparatively moderate rate of travel was surpassed only by increasing the number of motors and their horsepower until the fuel consumption became exceedingly high. This necessitated the carrying of a great weight of fuel and cut down correspondingly the useful load that the dirigible was capable of lifting as well as restricted its radius of flight at full speed. Until aerodynamic research had demonstrated the contrary, the necessity for such a tremendous amount of power was considered necessary to overcome the head resistance of the balloon itself. Research brought out in a striking manner how great a proportion of the total head resistance of an aeroplane was due to the struts and bracing wires. In the construction of the different types of airships illustrated, it will be noted that the gear provided for suspending the car or cars below the balloon requires a great number of cables. Later developments showed that by eliminating the great amount of head resistance caused by these numerous surfaces, the speed of a dirigible could be increased by over 50 per cent with the same amount of power.
Fig. 14. Section of Astra-Torres, Illustrating Method of Suspension.Fig. 14. Section of Astra-Torres, Illustrating Method of Suspension.CB, Bracing of Heavy Fabric Bands;SRandA, Suspension Ropes and Cable Passing through Envelope;S, Expansion Sleeve in Envelope;CC', Ropes to Sides of Car;E, Envelope
Fig. 14. Section of Astra-Torres, Illustrating Method of Suspension.CB, Bracing of Heavy Fabric Bands;SRandA, Suspension Ropes and Cable Passing through Envelope;S, Expansion Sleeve in Envelope;CC', Ropes to Sides of Car;E, Envelope
Improved Suspension.The shortcoming of the dirigible with reference to suspension was realized more than ten years previous by a Spaniard—Torres—but owing to lack of financial support, he was unable to put his idea into execution. The principle he evolved is made clear by Fig. 14, which gives a section of an Astra-Torres dirigible illustrating the method of suspension. Instead of the ropesSRused to suspend the car being attached to bands passing around the envelope, these reinforcing bandsCBand also the ropes fastened to them are placed inside the envelope, thus eliminating head resistance from those sources.
Performance.Failing to obtain any encouragement in Spain, Torres finally succeeded in interesting the French Astra Company, which built a vedette, or scouting airship, of a little over 50,000 cubic feet capacity. It was pitted against the Colonel Renard, at that time the leading unit in the French aerial navy and the fastest airship in commission. The small Torres dirigible so completely outclassed its huge competitor that another of close to 300,000 cubic feet capacity was built and tried against the Parseval with similar results. An Astra-Torres dirigible built for the British government showed a speed in excess of 50 miles per hour. This particular dirigible has been at the front in France almost since the outbreak of hostilities and has rendered considerable valuable service. Its success led the French Government to order a huge replica of it, having a capacity of over 800,000 cubic feet and with motors developing 1,000 horsepower, which would give it an indicated speed of 60 miles per hour. So confident were its builders of attaining or even exceeding this, that an order for a second and even larger airship of the Astra-Torres design was placed before the first one was finished. This is also fitted with motors aggregating 1,000 horsepower and displaces 38 tons, making it larger than any Zeppelin that had been constructed up to the time it was built. As its construction and trials were undertaken during the war, no details have been published, but it is said on good authority that its speed exceeds 60 miles per hour, so that it is faster than any of the German dirigibles.
Construction.Unlike the German dirigibles, the larger types of which have been characterized by a rigid frame, the Astra-Torres is a flexible airship and, owing to its method of suspension, its external appearance is decidedly unconventional, since the envelope instead of being of the usual cigar shape is more like a triangular bundle of three cigars with the third one on top. At the point where the three envelopes join, as shown in section, Fig. 14, heavy cloth bandsCBare stretched across the arcs, forming a chord across each arc, the three chords comprising an inverted triangle. The suspension ropesSRare attached to the opposite ends of the base of this inverted triangle and converge in straight lines downward through the gas space, so that the air resistance offered by the ropes is practically eliminated since only a very small part of the suspension system appears outside the envelope. This external part consists of vertical cablesAattached to the collecting rings of the bracing system and extending downward through special accordion sleevesSwhich permit the free play necessary at the points where they pass through the outer wall of the envelope. These sleeves also have another function—that of permitting the escape of gas under the pressure of expansion. A short distance below the envelopeEeach of these cables splits into two partsCandC'attached to opposite sides of the car.
The British airship mentioned is provided with but one car, but the larger French ships have two placed tandem, each of which carries a 500-horsepower motor driving two two-bladed propellers of large diameter. While the form of envelope made necessary by this construction increases the frictional resistance, this is negligible in comparison with the great saving in power effected by the method of suspension, not to mention the greater simplicity of construction.