[Fig. 24] shows the T or cantilever frame, so named because of its resemblance to that letter. It is usual to make the spar of this hollow, by channelling out two pieces of wood, and gluing and cramping them together under pressure. Where the bracing kingpost passes through the channel should be packed, previous to gluing the two half spars together, with a piece of hard wood, so that the assembled spar is not weakened by the piercing necessary for the insertion of the kingpost. Such a spar should not exceed 4 ft. in length. C is a section of the spar.
Fig. 23.—A Frame
Fig. 26.—T Frame
Fig. 25.—A and T Frame
Fig. 24.—T Frame
A much stronger twin-screw fuselage, which is a combination of the A and T frames, is shown by [Fig. 25]. Here, again, a single-channelled longeron should be used, although the propeller bar and supports should be solid. The channelled spar can be of silver spruce or birch, and the bar and supports of mahogany. A section of the spar is given at D.