Part 12 (1/2)

WASHERS--Under the bolt-head, and also under the nut, a washer e washer compared with the size which would be used in all-e area; otherwise the washer may be pulled into the wood and weaken it, besides possibly throwing out of adjust it is holding to the spar

LOCKING--Now as regards locking the bolts If split pins are used, be sure to see that they are used in such a way that the nut cannot possibly unscrew at all The split pin should be passed through the bolt as near as possible to the nut It should not be passed through both nut and bolt

If it is locked by burring over the edge of the bolt, do not use a heavy haht dae the ork inside the fabric-covered surface Use a se of the bolt until it is burred over

TURNBUCKLES--A turnbuckle is composed of a central barrel into each end of which is screwed an eye-bolt Wires are taken fro the barrel, they can be adjusted to their proper tension Eye-bolts ood fit in the barrel; that is to say, not slack and not very tight Theoretically it is not necessary to screw the eye-bolt into the barrel for a distance greater than the diameter of the bolt, but, in practice, it is better to screw it in for a considerably greater distance than that if a reasonable degree of safety is to be secured

Now about turning the barrel to secure the right adjustment The barrel looks solid, but, as a matter of fact, it is hollow and much more frail than it appears For that reason it should not be turned by seizing it with pliers, as that may distort it and spoil the bore within it

The best h the hole in its centre, and to use that as a lever When the correct adjustment has been secured, the turnbuckle

It is quite possible to lock it in such a way as to allow it to unscrew a quarter or a half turn, and that would throw the wires out of the very fine adjust wire so that its direction is such as to oppose the tendency of the barrel to unscrew, thus:

[Illustration]

WIRES--The following points should be carefully observed where wire is concerned:

1 _Quality_--It must not be too hard or too soft An easy practical way of learning to know the approximate quality of wire is as follows:

Take three pieces, all of the sath One piece should be too soft, another too hard, and the third piece of the right quality Fix them in a vice, about an inch apart and in a vertical position, and with the light fro upon theht reflected from each wire

Now bend the wires over as far as possible and away froht

Where the soft wire is concerned, it will squash out at the bend, and this will be indicated by the band of light, which will broaden at that point In the case of the hich is too hard, the band of light will broaden very little at the turn, but, if you look carefully, you will see sohness of surface In the case of the wire of the right quality, the band of light may broaden a very little at the turn, but there will be no roughness of surface

Bythis experiment two or three tiood, and also learn to know the strength of hand necessary to bend the right quality

2 _It ed_ That is to say, it ards keeping wire in good condition Where outside wires are concerned, they should be kept _well greased or oiled_, especially where bent over at the ends Internal bracing wires cannot be reached for the purpose of regreasing them, as they are inside fabric-covered surfaces They should be prevented fro painted with an anti-rust mixture Great care should be taken to see that the wire is perfectly clean and dry before being painted A greasy finger- to the wire In such a case there will be a little space between the paint and the wire

Air may enter there and cause the wire to rust

4 _Tension of Wires_--The tension to which the wires are adjusted is of the greatest importance All the wires should be of the same tension when the aeroplane is supported in such a way as to throw no stress upon thereater tension than others, the aeroplane will quickly become distorted and lose its efficiency

In order to secure the saed, should be supported by packing underneath the lower surfaces as well as by packing underneath the fuselage or nacelle In this way the anti-lift wires are relieved of the weight, and there is no stress upon any of the wires

As a general rule the wires of an aeroplane are tensioned too much

The tension should be sufficient to keep the fra more than that lowers the factor of safety, throws various parts of the fras into the wood, and will, in the end, distort the whole framework of the aeroplane

Only experience will teach the rigger what tension to e the construction of the various types of aeroplanes, the work the various parts do, and in cultivating a touch for tensioning wires by constantly handling them

5 _Wires with no Opposition Wires_--In some few cases wires will be found which have no opposition wires pulling in the opposite direction

For instance, an auxiliary lift wire may run from the bottom of a strut to a spar in the top plane at a point between struts In such a case great care should be taken not to tighten the wire beyond barely taking up the slack

[Illustration: Distortion of upper wing caused by auxiliary lift wire being too tight]

Such a wire must be a little slack, or, as illustrated above, it will distort the fraiven, will spoil the ca both the lift and the drift at that part of the surface Such a condition will cause the aeroplane to lose its directional stability and also to fly one wing down

I cannot ily