Canadian Forestry Journal, December, 1918 



1957 



Building a Canadian Aeroplane 



By Alfred Rubbra, Jr. 



How a Modern FlyinjS, Machine is 

 Put Together at a Toronto Factory. 



The manufacture of aeroplanes in 

 Canada has created a great demand 

 for the finest quality spruce, ash, 

 birch, oak and white pine. The 

 proper quality wood is very difficult 

 to procure and there has never been 

 a great reserve supply at an aeroplane 

 factory. 



The wood must be of a straight 

 grain and pass the many inspections 

 of the government and the manu- 

 facturer. The spruce used in the 

 aeroplane industry in Canada comes 

 from British Columbia. The Im- 

 perial Munitions Board have opened 

 large mills in the various timber 

 sections of the province. The out- 

 put of these mills is many millions 

 of feet of lumber a month. They 

 supply the British and Allied Govern- 

 ments as well as the Canadian Gov- 

 ernment. 



Great care is exercised to prevent 

 poor quality wood from getting 

 through. The first inspection takes 

 place before the log enters the mill 

 and the wood is again inspected before 

 being shipped. On arriving at the 

 aeroplane factory the lumber is in- 

 spected and cut into different sized 

 lengths as required. It is then piled 

 very carefully to prevent warping. 

 A slight warping cannot be avoided 

 so this is allowed for in the cutting 

 of the lengths. 



In order to dry the lumber to at- 

 mospheric conditions it is placed in 

 a kiln, which is heated by steam. 

 The air in the kiln is kept humid to 

 boil out the sap and acids. This 

 process is called case-hardening. 

 This is done by allowing some of 

 the steam to escape from valves in 

 the radiators. If the air in the 

 kiln was perfectly dry the wood 

 would not dry to the condition re- 

 quired in aeroplane manufacture. 



Ash, however, is an exception. It 

 is not kiln dried. If it were the 

 process would remove the properties 

 required 



Finding Wood Moisture 



When the contents of a kiln are 

 considered to be in the proper con- 

 dition samples are taken by the 

 inspector. These are weighed andi 

 put into a small furnace and dried 

 absolutely. The inspector then 

 weighes the wood again and is thus 

 able to calculate the amount of 

 moisture the wood in the kiln con- 

 tains. If the result is satisfactory 

 the contents of the kiln are taken to 

 the mill. Many samples have to 

 be examined to find out w^hether the 

 wood is just from ,the river or has 

 been piled for some time. In the 

 mill it is cut into the required lengths 

 for struts, beams for the wings, and 

 the many other parts. 



In the construction of aeroplane 

 wings, spriice plays an importan- 

 part. Great difficulty is experienct 

 ed in getting the long beams neces- 

 sary for the wings. The smaller 

 pieces are not so clifficult to obtain 

 as the grain runs straight for short 

 distances. One of the chief defects 

 in the wood and the most treacherous 

 because of the difficulty to detect it, 

 is spiral grain, rammy grain and cross 

 grain. The inspectors are, however, 

 rapidly mastering it. 



The ribs, which support the fabric, 

 are in some machines made of spruce 

 and are steamed and bent into the 

 proper shape across a drum. In 

 others they are supported by a web- 

 bing of white pine. The snow skids 

 w^hich are used in the winter in place 

 of wheels are of ash. They are 

 steamed and bent across a drum in 

 the same manner as the ribs. 



