Duellist MkII (oz5632)

About this Plan

Duellist MkII. Radio control sport twin model. Wingspan 69in, area 850 sq in, weight 9 to 10 lbs with retracting gear. For 2 x .25 to .40 engines. Plan says: "Redrawn by Joe Demarco."

Quote: "The first Duellist (oz5962) model although heavy, flew extremely well and had only minor problems. The Mk II here presented has been refined slightly, both in its force arrangement and in structural design, and can be made with confidence by the relatively inexperienced R/C fan. I would say that, if you can build and fly a Kaos, you are ready for this model.

Some of the more interesting aspects of the Duellist II's design might merit some explanation. For instance, I did not bring the nacelles as close as possible to the fuselage. Normally, twins use this feature to minimize the swing which occurs when one engine quits. While I don't argue with this logic, appearance is poor. Moreover, it seems like a cop-out to design a twin and then go as far as possible to avoid an offset-thrust situation. Instead, I placed the nacelles where they looked right, and prepared myself for heavy control corrections when one burner went out. In fact, nothing violent happened at all, and only a moderate turn resulted when one engine quit. This is easily overcome by throttling back the remaining engine to about three-quarters power, and full control is maintained, with turns either way, and landing approaches are normal.

Indeed, it probably is fair to say that one of the most fascinating and pleasurable experiences is to learn what you can do with the ship with only one motor running. After you get used to the ship and come to understand its personality, you can amaze your buddies with one-engined four-point rolls, inverted eights at a near-idle, wonderful stall-turns.

Take a look at the ailerons. They are basically strip ailerons (easy to build), but are placed well inboard, compared to a typical single-engine job like a Kaos (oz6251). Thus, they are working directly in the prop slipstreams and are very powerful, despite stopping some 10 in short of the tip. Until I did this, the vibration from the wing-mounted engines kept breaking the aileron hinges at the tip end. This problem has now been licked without reducing control effectiveness.

With a wing span and area of 69in and 850 sq in respectively, the Duellist II is intended for .19 up to .40 engines. Weight is around 9 to 9-1/2 Ib with retracts. The original Duellist weighed 12 lb, mostly due to noseweight required when the CG came out too far aft.

Using .19 engines, the newcomer to R/C or to twins will have a 'pussycat'. We used the new K&B .29's (4.9cc), as the photos show, and this is enough power to pull the airplane up in a true 90 degree vertical climb indefinitely..."

Direct submission to Outerzone.

Update 22/04/2020: Added kit review from MAN June 1981, thanks to RFJ.

Supplementary file notes

Article, thanks to DavidLegard.
Review.

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