X-12 Delta (oz10791)

About this Plan

X-12 Delta. RC Delta-Motorflugmodell X-12. Simple RC delta pusher design. All-sheet construction. Wingspan 498 mm, for Cox Pee Wee power.

Direct submission to Outerzone.

Update 14/8/2024: Added article, thanks to Rennfahrer.

Quote (google-translated): "MT construction plan 569. RC delta motor flight model 'X-12'. Model design: Hartwig EßI.

The small delta flight model shown below is primarily intended for the small receiver described in FMT issue 173/70 by the same author. A Cox 0.33 cc engine is used.

The model was built by the author in two versions: one with a wingspan of 49.8 cm (which is also specified in the enclosed construction plan) and the other with a wingspan of 44 cm. The smaller model is a scaled down version of the larger version and has the same flight characteristics. The images on these pages show the model with a wingspan of 49.8 cm, as the smaller version gave up the ghost under the shoes of an overly eager spectator. For the replica, it is therefore recommended that the model be scaled down slightly, although the specified material thicknesses should be retained.

Before we deal with the actual construction, here are a few considerations about the delta shape of such small flying models.

The delta shape enables the simplest and most unproblematic construction of a model and results in a natural and attractive appearance. The compact outline means that no 'long levers' are in effect, which makes such a model extremely stable; harder landings and rollovers generally do not affect it. The delta shape also naturally results in a large load-bearing surface with a small wingspan (the wing load must, however, be lower compared to normal models). The disadvantages are that the delta flies a little faster than a normal, tame single-axle model and that it straightens up from an inclined position more slowly than such normal models with a relatively large V-shape.

The model presented here can also be flown by RC beginners if only very small rudder deflections are made for the first take-offs and the first steering attempts are only started at a sufficient height.

Construction: First, wing 1 is built. It is advisable to use a letter scale to select a particularly light and evenly grained balsa wood (the same applies to the other parts). The boards are glued together with UHU-hart and the undivided wing is cut out according to the drawing (grain perpendicular to the direction of flight). The edges are rounded and the wing is sanded cleanly with fine glass paper. Then thin covering paper is applied to one side with diluted tension varnish without any creases. As soon as the tension varnish is almost dry, the surface is stored between two flat boards to prevent it from throwing; the same is repeated with the other side. After sanding again with the finest glass paper and painting with a thin varnish, the surface is again laid flat between two plates. This is very important so that the surface does not warp now or later.

Only at the end, before the wing is firmly glued to the fuselage, are the ribs 8 and 9 glued on. To attach the rib 8, the surface is cut and bent on the left and right on the underside according to the dashed line in the construction plan. Gluing the rib 8 on automatically creates the correct twist.

The structure of the fuselage is also very simple and is clearly shown in the construction plan. First, the side parts 2 are cut out and provided with 2 x 3 mm balsa strips on the edge and for stiffening as shown in the drawing. The fuselage is then brought into the shape shown in the top view using the frames 7 and 14. Before the underside is planked, the wing must be glued to the fuselage. Then the control rods are installed. This arrangement is very clear from the description supplied with the control star, so it is not necessary to go into it in the construction plan. At this stage of construction, the nuts for the engine mounting are also fixed to the inside of frame 14 with UHU-plus.

The last 5 cm of the fuselage are painted on the inside with fuel-resistant tensioning varnish. After the planking is complete, the fuselage is also sanded down and cover 5, which provides access to the remote control system, is fitted neatly...

Supplementary file notes

Article.

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