Part 16 (1/2)

6 CAMBER--The camber (curvature) of the blades should be (1) equal, (2) decrease evenly towards the tips of the blades, and (3) the greatest depth of the curve should, at any point of the blade, be approxi edge as at other points

It is difficult to test the top camber without a set of templates,[18]

but a fairly accurate idea of the concave ca the blade, thus:

[Illustration]

The cae is passed along the blade, the observer should look for any irregularities of the curvature, which should gradually and evenly decrease towards the tip of the blade

7 THE JOINTS--The usualthe propeller at greater speed than it will be called upon tothe joints to see if they have opened It is not likely, however, that the reader will have the opportunity ofthis test He should, however, exa by hand to see if they are quite sound

Suspect a propeller of which the joints appear to hold any thickness of glue Sometierous unless they extend to the blades, as the bolts will hold the laether

8 CONDITION OF SURFACE--The surface should be very smooth, especially towards the tips of the blades Some propeller tips have a speed of over 30,000 feet a hness will produce a bad drift or resistance and lower the efficiency

9 MOUNTING--Great care should be taken to see that the propeller is ht on its shaft Test in the saht, it is possibly due to so been pulled up too tightly

FLUTTER--Propeller ”flutter,” or vibration, le, balance, ca It causes a condition soine trouble, and one which may easily lead to the collapse of the propeller

CARE OF PROPELLERS--The care of propellers is of the greatest importance, as they become distorted very easily

1 Do not store them in a very damp or a very dry place

2 Do not store them where the sun will shi+ne upon the in a horizontal position or leaning up against a wall

4 They should be hung on horizontal pegs, and the position of the propellers should be vertical

If the points I have impressed upon you in these notes are not attended to, youresults:

1 Lack of efficiency, resulting in less aeroplane speed and climb than would otherwise be the case

2 Propeller ”flutter” and possible collapse

3 A bad stress upon the propeller shaft and its bearings

TRACTOR--A propeller mounted in front of the main surface

PUSHER--A propeller mounted behind the main surface

FOUR-BLADED PROPELLERS--Four-bladed propellers are suitable only when the pitch is coard to ”interference,” they are not so efficient as two-bladed propellers

[Illustration: SPIRAL COURSES OF TWO-BLADE TIPS

SPIRAL COURSES OF FOUR-BLADE TIPS