Wasp (oz13925)

 

Wasp (oz13925) by Andy Lennon 1988 - plan thumbnail

About this Plan

Wasp. Radio control sport model, with 'tandem wing biplane' layout. For .15 engines.

Quote: "Sting the opposition with this unique canard pusher for .15 engines and 4 function radio. The Wasp, by AG Lennon.

THE WASP is classified by this author as a 'Tandem Wing Biplane' - both wings being of equal chord, span and area. It has the non-stalling characteristics of a canard whose foreplane is substantially smaller than the aft plane. Obtaining the correct CG with the Wasp's configuration is easily accomplished without ballast - which cannot be said for a canard with a pusher engine located behind the aft wing.

Aerodynamic theory, confirmed by wind tunnel testing, indicates that equal span wings in tandem have lower induced drag than a conventional wing-tail arrangement provided the vertical separation (GAP) and the longitudinal spacing (stagger) between the wings is adequate. The Wasp configuration was based on this data. In addition the Clark Y wing section employed for both wings has surprisingly low profile drag at the low Reynolds Numbers (150.000) at which this model cruises. Particular attention was paid to drag reduction in other components; landing gear legs have fairings, the engine is completely cowled, wheels are streamlined and control horns - except on the twin rudders are enclosed in the structure.

The model portrayed in flight and in the drawings is, I regret to say, the second version. The first crashed after a short flight, due to poor selection of front wing airfoil (Eppler 385M) which assumed its zero-lift angle of attack with aft wing still lifting. This resulted in a violent nose dive which demolished all but the aft wing and fins/rudder. Pitch control with full span elevators on the foreplane proved over-sensitive, contributing to the crash. Aileron control, with differential action (twice up to down action) proved excellent during the short flight. Radio, servos and engine were undamaged.


The model was redesigned. The foreplane airfoil was changed to that of the aft wing, Clark Y. The fuselage was moved forward relative to the front wing to advance the CG; and the angles of incidence of both wings were adjusted to provide balanced lift - taking into account the impact of the downwash, from the front wing, on the aft wing. The front plane elevators were reduced to 70% of the wing's span.

The model was rebuilt and test flown, successfully. Longitudinal stability was excellent, aileron control precise, but the model was unstable directionally, and tended to spiral dive readily.

The vertical tail surfaces, during the initial design process, were each increased in area, as a precaution, compared to the calculated areas. Cutting off the tops of both fins and rudders and replacing the top-caps removed this additional area. Subsequent test flights confirmed this action. The aircraft was stable around all three axis.

The adjustable trim flap in the aft wing, inboard of the ailerons and fins, was found unnecessary and has been deleted from the drawings.

The black and white construction photos are of the first version, but construction of both versions is almost identical - and the small difference should present no problem. Note that the fuel tank is almost centred on the CG; very little change in CG occurs as fuel is consumed.

The engine is installed inverted with a Tatone universal exhaust manifold which permits cowling the power plant completely. The exhause pipe (3/32 dia alum tube) is directed downward through and below the cowling.

Cooling air enters on both sides of the fuselage through NASA-developed, recessed, low drag scoops, and exits through the opening below the spinner - aided by the propellor which 'sucks' the air through the cowling, to effectively cool the engine.

Accessibility to all four servos, fuel tank, onboard battery and nose wheel steering is achieved through the easy removal of the top of the fuselage (canopy). Similarly, the lower portion of the engine cowling is easily removed by hand for access to the glo-plug and carburettor..."

Wasp from RCM&E, February 1988.

Direct submission to Outerzone.

Supplementary file notes

Article pages, thanks to RFJ.

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Wasp (oz13925) by Andy Lennon 1988 - model pic

Datafile:
  • (oz13925)
    Wasp
    by Andy Lennon
    from RCME
    February 1988 
    31in span
    IC R/C Pusher
    clean :)
    all formers complete :)
    got article :)
  • Submitted: 07/07/2022
    Filesize: 848KB
    Format: • PDFbitmap
    Credit*: Circlip, RFJ
    Downloads: 552

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User comments

The details of this model's design principles are found in Andy Lennon's book 'Basics of R/C Model Aircraft Design', which is hosted on Outerzone's sister site, RCLibrary. The Wasp makes an appearance in Chapter 16.
Link here : https://rclibrary.co.uk/title_details.asp?ID=1433
Martin La Grange - 01/04/2023
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