Finale (oz15276)

 

Finale (oz15276) by Mike Freeman 1988 - plan thumbnail

About this Plan

Finale. Radio control slope soarer model. Uses all-moving wings for control. Wingspan 38 in.

Direct submission to Outerzone.

Quote: "RM Plan Feature: A soarer with moving wing for roll and pitch control. Finale, by Mike Freeman.

After the success of Prelude (oz11947) and Sequel (RM May 86), I wondered if there was any possibility of the all-moving wing method of roll and pitch control being used on an all-flying wing design. This would mean that there would be no outside means of holding the fuselage on line while the wing angle of attack changes, which the tailplane does on the previous models.

I spent a lot of time thinking about the theory. A flying wing's lateral stability is achieved by adding reflex to the trailing edge of the wing. Reflex could easily be added to the all-moving wing, but would pitch control be possible or would the wing hold steady in its equilibrium in the airflow and the body just nod up and down? I could not convince myself one way or the other, so the only way to satisfy my curiosity was to build a prototype and find out. My flying wing design Zippy (oz7664) flys well using conventional elevons so I decided to use the same wing design on the prototype. The body was to be the same as Sequel from the nose to the rear of the wings but shortened at the rear so that the fin was just behind the TE.

I did not want to spend a long time building something that I was not sure would fly so I came up with the idea to convert the model, in seconds, from flying wing with reflex to V-tail. The tail feathers changeover was quite easy to overcome. I made a combination tail with removeable flying surfaces from brass tube and piano wire joiners and sheet balsa. These were arranged such that the same surfaces can be used for either V-tail or fin. The photos show the arrangement during construction and when built into the body.

The reflex required a bit more thought. I wanted to keep the wings 'clean' without any horns and I wanted the change from reflex to no reflex to be quick without the need to fiddle with clevises. I spent a lot of time thinking about a way to achieve this. I was just about to give in to putting horns in when the idea in the photos came to mind. It is so simple and easy and to date has performed faultlessly.

The brass tube is held in the root rib by reinforcement inside the wing, and the 1/32 ply facing rib, so there is no way it can become dislodged. The wire inserts (bent for reflex, straight for non) are a tight fit in the yokes, so there is no possibility of them falling out or any free play.

With the concept finally decided, the model was quickly built, covered, and the gear installed. The CG was located as for Zippy at 40% root chord. Before long I was driving to my favourite slope.

Faced with a 10 to 15 mph wind straight onto the face of the slope, I decided to try the model in V-tail mode first; this seemed the best choice to start with as at least there would be a degree of lateral stability. The V-tail plane surfaces were installed and the wire inserts for no reflex were fitted. Holding the model into the wind and feeding in pitch control first up then down had the right effect so with much optimism I launched... SPLAT! Oh well, bad launch, try again... SPLAT! The model followed a parabolic path straight into the ground irrespective of launch attitude. There was no lateral control at all. I decided to add the reflex and try to get better stability.

This time the model climbed out into the lift beautifully. Roll response was fine, similar to Sequel, but there were still problems with pitch. Up was OK, but down was very limited. With full stick there was only just enough effect to penetrate, nowhere near enough to dive.

Eventually I got the model down again and contemplated what next. I wanted something between the first launches with no reflex and the last one with the full reflex - how about half the available reflex? Could it be that simple.

Yes it could! In this mode everything was fine. Roll response was good and pitch control much better, penetration was effortless into the 10 to 15 mph wind. It was now possible to try some aerobatics, rolls were easy even if a little barrelly, loops were possible with speed but, as with all flying-wings, they had to be kept large. I tried to stall but this was not possible. Ease back on the stick and the model started to wallow about, but roll control was still present. (In strong winds it is possible to get the model to fly backwards doing this). Any over zealous stick stirring in this attitude usually ended up in a spiral dive. Flying the model in this V-tail and half reflex mode was so enjoyable and relaxing I nearly forgot the reason for the whole exercise..."

Finale from Radio Modeller, April 1988.

Supplementary file notes

Article pages, thanks to RFJ.

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Finale (oz15276) by Mike Freeman 1988 - model pic

Datafile:
  • (oz15276)
    Finale
    by Mike Freeman
    from Radio Modeller
    April 1988 
    38in span
    Glider R/C
    clean :)
    all formers complete :)
    got article :)
  • Submitted: 29/04/2024
    Filesize: 610KB
    Format: • PDFbitmap
    Credit*: Circlip, RFJ
    Downloads: 456

Finale (oz15276) by Mike Freeman 1988 - pic 003.jpg
003.jpg

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