THE INDIA RUBBER WORLD 



[October i, 1908. 



balloon — the dirigible offered by Captain Thomas S. Baldwin, 

 with a capacity of 18,000 cubic feet — was made by an important 

 rubber concern in this country. 



Balloon fabric has also been used of laic in France for the 

 construction of the planes of aeroplanes, whereas formerly varn- 

 ished silk and even varnished or oiled paper was used for this 

 purpose. These substances are likely to be entirely superseded 

 in flying machine construction by balloon fabric, which is much 

 more durable. For motor balloons, as well as for aeroplanes, 

 thin sheet-metal has been tried for the envelope. In building the 

 great motor balloon of Count Zeppelin, a great deal of aluminum 

 was used, but the gas bag itself was of rubberized balloon fabric. 

 Jatho, of Hanover, in his aeroplane, experimented with planes 

 covered with thin sheet magnalium, and the French constructors 

 otained the material for their flying machines from Hanover. 



Not only the introduction of the motor balloon, especially the 

 military balloon, has led to an increase in the demand for balloon 

 fabric, but the sport of ballooning, with sailing balloons, has also 

 witnessed remarkable growth. Thus the number of members in 

 aeronaut clubs has increased about 30 per cent, within the past 

 year and fiew clubs have been formed in many cities. The mem- 

 bers of the German clubs -own 30 sailing balloons and the clubs 

 are already-beginning to use motor balloons for sporting purposes. 

 At the recent international balloon contest at Hurlingham, Eng- 

 land, starting from the grounds of the Hurlingliam Aero Club, 

 there were 31 entrant ■;. 



Count Zeppelin's Air Ship "Number Four." 



[During a thunderstorm on August 5 the gas took fire and the machine was 

 destroyed. The German people have subscribed $400,000 to build 

 another.] 

 — Courtesy of The American Review of Reviews. 



In an article in the Gummi-Zeitung it is pointed out that while 

 in the automobile the value of the product of the rubber industry 

 (the tires) is about one-tenth of the total value of the automobile, 

 in an airship, the rubber product, represented by the gas bag, con- 

 stitutes the greater portion of the value. The value of the ma- 

 terial in aeroplanes is much less, although in covering the planes 

 of such aeroplanes as those built by Farman and Delagrange, 

 over 100 square yards of balloon fabric is required. In compari- 

 son, for an ordinary motor balloon, about 2,000 square yards of 

 balloon fabric is required, making the value of the gas bag of a 

 motor balloon about $S,ooo, to which must be added the cost of 

 making up, the filling tubes, etc. The steering and stabilizing 

 planes of motor balloons are also mainly constructed of balloon 

 fabric, so that the rubber material in a motor balloon of medium 

 size represents a value of about $6,250. 



The rubberized fabrics for ordinary sailing balloons are cheaper, 

 but cost nevertheless from $1.50 to $2 per square yard, so that 

 the balloon fabric alone is worth from $750 to $1,250. Varnished 

 fabric, used extensively for sailing, never for motor balloons. 



The First American W.\r Balloon. 



[Captain Baldwin's Dirigible, tested in August by the United States Govern- 

 ment at Fort Myer. Balloon fabric made by an .■\merican rubber 

 company.] 

 — Courtesy of The American Review of Reviews. 



costs about 60 cents per square yard in Germany. The low dura- 

 bility and strength of the varnished balloon fabric is due to the 

 hardening or resinification of the varnish, causing the substance 

 itself to become brittle and readily breakable. 



The method of making both kinds of fabric may briefly be 

 described as follows, according to the Gummi-Zeitung: For both 

 kinds of balloon fabric cotton fabric, mostly percale, is almost ex- 

 clusively employed. For varnished balloon fabric a single thick- 

 ness of cloth is used, to which boiled linseed oil varnish is ap- 

 plied, the work formerly done by hand being now effected by 

 mechanical means. In a thin layer this varnish has the property 

 of taking up oxygen from the air and drying in a thin coating. 

 The oxidization process is dependent on the moisture in and 

 temperature of the air. As soon as it is completed, which is in- 

 dicated by the darkened color and the hardness, the fabric loses 

 much of its flexibility and readily becomes brittle. In special 

 cases, where the greatest possible lightness is necessary, in place 

 of cotton cloth a silk fabric is employed. The varnishing process 

 tends to render this substance more than ordinarily brittle, and 

 for this reason, and on account of its much higher price, varn- 

 ished silk is seldom used for balloons. 



Rubberized balloon fabric is made in the familiar manner, the 



Wright's Aeroplane .\t Fort Myer. 



— By courtesy of The Automobile. 



