Chuco (oz11100)

About this Plan

Chuco. Radio control glider, for 2 channels. Wingspan 1460mm.

Scan from KaoruKiyose, cleanup by theshadow.

Quote: "The Chuco plan seemed vaguely familiar. I have a vectorized version in my Hand Launch folder that appears to be the same plan. I have attached this file as a supplement."

Direct submission to Outerzone.

Update 23/7/2026: Added article, thanks to Axel_VPF.

Quote (google-translated): "Construction Plan
MT-1074: Chuco Hand-launch Glider
Design: Klaus Kurt.

The fun of model flying isn't measured in wingspan meters; following this realization and the current trend, a small glider was in order. The inspiration came from watching an RC launch glider competition. The whole thing was nice and relaxed. It took place on a gentle slope that's unflyable for 'normal' glider sizes. And the small models showed surprising flight performance - considering the ridiculously low construction effort. So, off to the drawing board and into the workshop!

The model building industry has already responded to the demand for mini-gliders. There is at least a small selection of suitable kits with which decent little gliders can be built. Unfortunately, in this size range, the discrepancy between the kit price and the material costs (for self-assembly) is particularly high. Some kits even include a separate empty compartment because the kit contents don't even fill the already small box.

The aircraft shown here was essentially built from leftover balsa wood (from building larger models). It wasn't just cost-benefit considerations that inspired the construction: realizing an original design was a gratifying goal! It was clear from the outset that the result would hardly differ from commercially available products. For every task, there is only one optimal solution. For those who would like to delve a little deeper into the subject, the process by which this design came about is described here.

A degree in aerodynamics isn't necessary, but some technical literature is quite helpful for the non-academic model aircraft enthusiast. In this case, the 'Handbook for Model Flying, Volume 1' by Werner Thies and the MTB Advisor 4 'Construction of RC Glider Models,' both published by VTH, were available. The information contained therein allows one to attempt the design of a simple hand-launched glider even without in-depth knowledge of aerodynamics. The intended approach could not be overly scientific anyway, as practical considerations inevitably lead to sometimes considerable compromises; be it the maximum acceptable construction effort, the commercially available ready-made products (eg trailing edge), or the quality of construction achievable with simple means. From all this, the design of this model emerged, following the following principles: construction using readily available technical knowledge, and a conventional construction taking into account commercially available materials and RC components.

Initially, only the wingspan was specified. Perhaps it was a kind of gentleman's agreement not to exceed 150 cm; probably because this measurement had proven practical. Now, one can specify an empirical value for the wing area, or one can choose the aspect ratio. For gliders of this size and for this intended use, the aspect ratio should not be too high (otherwise, for a given wingspan, the wing area becomes quite small, and structural rigidity becomes problematic).

After marking out the rib spacing (using practical, sensible measurements) - and accounting for the dihedral angle - the resulting wingspan was 147 cm. Based on an aspect ratio of 7.5, the calculated surface area was approximately 29 dm² (147 x 147 ÷ 7.5). This implies a mean chord of 19.5 cm (147 ÷ 7.5). The wing was drawn using these figures.

A tail moment arm of approximately 50 cm was determined using a chart from the VTH handbook. A nomogram indicated a tail surface area of ??5 dm² (suitable for slope soaring models). With that, the essential specifications were established.

Choosing the airfoil didn't require much agonizing. A flat-bottomed section wasn't really the goal, as the intention was to fly in light breezes or off small slopes - situations where one is happy to trade a bit of speed for extra lift. For structural reasons, the airfoil thickness needed to be at least 10%. Experience from free-flight models suggested a slightly drooped, somewhat pointed leading edge for this Reynolds number range. Commercially available trailing-edge stock ruled out anything resembling an Eppler section - such thin trailing edges simply don't exist (and, in any case, Eppler airfoils are difficult to execute using rib-and-spar construction). Based on these considerations - and a flourish of the drafting pen - an airfoil emerged that closely resembles the Göttingen 602. The angle of incidence was set at 2 degrees, and the center of gravity was planned for approximately 30% of the wing chord (all of which can be found in those clever books mentioned earlier).

Wing attachment was to be handled conventionally using rubber bands; however, the leading-edge area at the wing root needed to be kept as clean and undisturbed as possible. Consequently, the forward anchor point for the rubber bands was positioned at the center of the fuselage. Achieving a smooth transition from the fuselage nose to the wing with minimal effort required the use of shaped blocks at the wing center. Finally, the dimensions of the RC equipment and the desired center of gravity dictated the minimum fuselage cross-section and the final fuselage length. The shape of the vertical stabilizer was primarily a matter of aesthetics.

Once everything was down on paper, it was evident that the result differed little from the form of other designs. But really, that was just confirmation of the original design!

Building the Chuco presents no difficulties whatsoever. Since this aircraft wasn't intended to be an ultra-lightweight design (very light hand-launched gliders can't be thrown very high), there is no need to be overly meticulous about the choice of wood. Especially with the spars and trailing edges..."

Supplementary file notes

Article.
Vector PDF plan.

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