Demon (oz4889)

About this Plan

The Demon. J Van Hattum, 62in wingspan FF glider from Model Aircraft March 1948.

Quote: "This sailplane design by Juste Van Hattum has shown itself to be a good and reliable performer, and since its construction is at the same time simple, we have no hesitation in presenting it to our readers as a first-class model of the intermediate type. As it conforms to the old FAI rules it comes well within the new 1948 rules, and is therefore eligible for all types of contests.

Like most Continental designs it is characterised by a slim fuselage with a large area forward of the centre of gravity and a shoulder wing which is mounted direct on a platform, with a sloping forward ramp built direct on to the main longerons. The centre section is built up to follow the fuselage contour.

The Fuselage and Tailplane: The fuselage is built in hardwood; such as spruce, poplar, or obechi, with the formers cut from 1-mm ply, except the nose former No.1 which is cut from 3-mm ply and the former at the wing trailing edge No.8, which is cut from 2-mm ply.

The fuselage is hexagonal in section, and is built up on two main longerons of generous dimensions with three keel longerons.

The upper decking is cut away at the wing position to provide a wing platform in the popular continental style, in which the centre of the wing forms a continuation of the decking, with a forward horn-piece round which the attachment rubber bands are passed.

The construction is quite straightforward if the top side of the main longerons are maintained straight, their taper from the wing position to the tail being carried out on the underside only.

Some support blocks (all of the same thickness) can be inserted between each former on which the edge of the main fuselage longerons can be seated, upside down, while the three keel longerons are cemented in position. When thoroughly set the fuselage can be removed and the decking longeron fitted in place. As the decking longeron is designed to be straight it serves as a check on the accuracy of the first step in the construction, and it is best to apply this in one piece over the full length of the fuselage and cut away the portion at the wing position afterwards.

The wing platform is made from 1-mm ply, applied on a ramp, fitted to the top of the longeron to give the correct wing incidence. The fin and tailplane are built-in with the fuselage before it is covered.

The nosepiece is built up from three pieces of balsa, the centre one being cut away to form a cavity for the balance weights, which are introduced through a hole in the top which is plugged with a dowel with a streamlined handle. The nosepiece must be firmly cemented to the front former.

The tailplane should be built up separately on a board, taking care to glue the stiffening blocks at the centre of the spar thoroughly. Note that the wing-tip contours are cut from 1-mm ply, and built up on the top side with balsa segments to provide a smooth contour with the spar ends. The tailplane should be attached to the tail-end of the fuselage before the trailing portion of the fin is fitted, as the trailing edge fits in between the two tailplane inner ribs..."

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