Vannus (oz15675)

About this Plan

Vannus. Free flight tail-less model. Wingspan 42 in.

Note the Vannus and Vannus Minor (oz15676) both appeared in the same article.

Direct submission to Outerzone.

Quote: "Hi Steve and Mary, The first of tonight's offerings is the Vannus, a 42" flying wing free flight model, designed for either an .049 glow engine or a KP02 brushed, geared electric unit. It was presented as a free plan with Aviation Modeller International in 1995. On the reverse side of the plan was a smaller version, the Vannus Minor, 28" span, for either a Cox .010 Pee Wee or a KP01 electric unit. Best Wishes, Dilwyn"

Update 22/11/2024: Added article, thanks to RFJ.

Quote: "This model was the outcome of a session of the common aeromodelling pastime of daydreaming through a collection of plans. I carne across Kloudet (oz3260) a tailless model described in Model Aircraft, March 1958, designed by Laurie Ellis. I had just acquired one of Clive Bunyan's electric units, and was looking for a vehicle for it, so I consulted my Oswestrian spirit guide, Dr Eiborl, (he draws all my wing sections, too) and got busy on the drawing board.

I decided no undercarriage on the grounds that they cause damage to fuselages in sudden arrivals, they get models hung up in trees, and they add weight. The thrust line should be as high as possible, to clear the prop when on the deck, and the nose had to be long enough to allow the battery weight to form a reasonable part of the nose ballast.

Taper wings are no problem as to rib sections when a flat bottomed section is employed, and the old trick of the tilted root rib used to derive the remaining ribs. Establishing the balance point for a swept taper wing is also quite simple, using the geometrical diagram shown on the plan.

I built my wing without washout - flat on the board - but curiously I now find that it has near enough the washout shown on the drawing. I can only assume that some facet of the construction gives this result, after shrinking the covering. Whether the washout is vital, I couldn't say, since my two Vannus Minors are both completely flat. The small amount of dihedral is purely cosmetic - the model looks better, although I understand that dihedral is unnecessary on wings with so much sweep.

It is possible that the wing-tip fins are redundant - my model has flown quite normally with one fin knocked off - but again, the model looks better for having them. Butt join a long grain piece across their top edges, to reduce any tendency to bow.

Construction is straightforward, but take care to plan for your motor installation. The original Bunyan unit in mine had reached the point of requiring a new set of 50 mAh cells - and I had a KP 02 to hand, so I simply glued a plate of 1/16 ply over the hole for the Mabuchi of Clive's unit, and screwed the KP 02 directly onto the rear bulkhead, with the battery box removed, and using the battery box lugs for the bulkhead mounting. The battery, on extended leads, fits in the nose bays shown. One day I may cowl it, purely for looks.

I mount my KP units on 3/16 lengths of soft fuel tubing, and use 2mm screws tapped into the ply, in such fashion that they are somewhat tight in the thread, which is hardened by an application of cyano, after tapping. By using a taper tap - easily made by filing a 2mm screw into a taper of three flats, and NOT taking it through to full thread, the motor screws are tight enough to hold when the piece of tubing is squashed the correct amount to obtain the necessary side and downthnist, and adjustments later on quite simple.

Since building Vannus, I've built a 44 in follow-up for R/C, somewhat heavier, of course, and fitted with a Cox Golden Bee. Even with a 2-1/2in pitch pusher prop, it is quite fast - and out of trim, somewhat nervous making - so if you choose to put an 049 into Vannus, be prepared to put in LOTS of downthrust, and very little fuel, because I believe that it will climb like the proverbial bat.

It's a good idea to make a name and address plate and glue it onto the cockpit back wall before fixing the glazing - my own model has found its way back three times as a result of this, as have both the smaller versions with KP 01's.

My model was covered with Solarfilm, so that flying into the late evening would not be stopped by sagging tissue - and it has been flown quite happily in light rain. If you cover yours with any lighter material, tissue or film, be wary of giving full charges, especially if there is lift about - with the Bunyan unit installed I made a mistake once and gave near a full charge - the model made around five or six hundred feet, and did nearly fifteen minutes. Fortunately there was only slight drift, and she covered only four fields.

By reversing the polarity of the motor connections, a standard tractor prop may be used. Remember that with pusher installations reactions to motor torque and thrust require opposite settings of the rear thrust line - motor left, and clown to the rear, for basic settings. Ballast the model 1.0 balance at the point shown, and adjust the elevons to give a fair glide, and with about 3 degrees 'Left' and 'Down' thrust, with a KP 02, give about one and a quarter to one and a half minutes charge for a test flight, and begin a test series where you fine tune the nose weight and the elevon trims to give the flight pattern you require.

The original model flew a left pattern, because I had altered the motor connections. It now flies a right power, left glide, because the KP 02 has not been altered.

Launch two handed, gripping the TE outboard of the prop - where else? Give a good push into level flight, and she'll go away nicely."

Supplementary file notes

Article.

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