"GLIRT"
By P.A. LATHAM
The construction is quite simple and straightforward, but great care must be taken in making the soldered joints secure and in lining the wire booms up correctly.
The wings are constructed from 1/8 in. medium sheet balsa, with a strip at the leading edge of either hardwood or hard balsa. The wings must be strengthened at the appropriate places with either hardwood or thin ply to avoid wear from the tail booms. The guides for the tail booms are of hardwood with the grain running as in the drawing. The space between the guides is best judged by using a piece of 20 s.w.g. wire when they are being fixed. The two wings should be first joined together at the correct dihedral angle, the joint being covered on both sides with cement-saturated ½ in. strips of tissue paper. When they are firmly set, No. 3 lamination of the fuselage should be cut away to take them so that they form a good fit and the wings cemented in. The incidence of plus 2° can be checked here and any alterations made. The rest of the fuselage laminations can be attached and the block sanded to shape. It will be seen that the cut-out portion of the rear of the fuselage is covered with a sheet of metal foil. It is attached by cutting out tangs on the edge and forcing them into the wood.
The tail is also quite straightforward. The wire brace across the cut-out piece being attached to the rest of the tailplane by strips of cement-saturated tissue holding the wire in its grooves. The fins are attached to the tailplane by cutting a slot halfway into the rear of the tailplane and another halfway into the front of the fins. The slot in the front of the fins should be wide enough to take the wire extensions from the tail booms. When the tail has been fixed to the booms, a 1/16 in. square strip of balsa should be cemented either side of both fins to enclose the wire extensions. The upright piece at the end of the tail booms is let into the fins and covered with cement-saturated strips of tissue.
The wire booms are the only things which may cause trouble. The plan clearly indicates the
shape of them. In order to make a perfectly accurate job, the following method may be used
:– Trace the shape onto a piece of flat wood and cut grooves to this shape with a penknife or patent modelling tool. Bend the main outline in 20 s.w.g. wire and make sure that it fits into the grooves. It can be held firmly in the grooves with bent pins used as staples. The cross-pieces, of similar wire, can then be put in : it may also be advisable to hold these with pins as they have a tendency to stick to the iron when soldering them and come out of the grooves. Make sure that both booms are exactly the same, especially the angle between the wing slot and boom.
The wings are fixed to the boom by sliding them into the slot in the boom, the boom being held firm in the 1/32 in. strip guides.
The model flies powered with the ordinary twopenny rocket, which is attached with two elastic bands; the heat is not sufficient to burn them. The model is launched by placing it on a flat board a foot or so wide and about four feet long. The board should be at an angle of between 30 and 50 degrees to the horizontal. If any instability is found during the take-off, strips of wood can be nailed to the board for the skids to run between. Before the model is flown, it should be balanced accurately about its fore and aft axis and then trimmed to fly straight.
The model climbs at about the same angle as the take-off board till the rocket is spent. The glide is improved by finishing all the wooden parts with banana oil and sanding down smooth. Do not use explosive rockets !
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Click image to view or download enlarged dimensioned plan
- Aeromodeller,November 1946
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