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away the cause of the difficulty, but as this would have necessitated far more work it was thought sufficient to strengthen this part.  Two methods were used.  The simpler one, consisting in replacing the original 24 x 1 mm. vertical tube by a 28 x 2.4mm. tube, giving not only increased strength against torsion, but slightly strengthening the whole tail by the greater circumference that can be directly welded in the "V" of the main girders.  This has proved satisfactory.

A stronger type of tail skid than that originally mounted is now being used also.

An interesting point to be considered is the ease with which major repairs can be carried out.  Entire tubes can be replaced and welded in the old fuselage.

The report of the Dutch National Aeronautical Research Laboratory may be quoted as to the best way in which such parts can be welded:

In tensile tests of tubes welded together, with an inner tube reinforcement, the failure occurred at the outer edge of the inner reinforcing tube, while the total strength of a tube

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