Twinwall Wings - Adding Ailerons

Ailerons come in all shapes and sizes

In this section I'll deal with adding simple strip ailerons to a wing. These have worked fine for me on many aeroplanes and, while maybe not the neatest or most aerodynamically efficient ailerons, they more than make up for it in their ease of construction.

Once the techniques are familiar and understood, it's just a short step up to customising the ailerons to fit your own plans, whether they're to give a more scale appearance or to make room for flaps etc.

Simple trailing edge ailerons

The simplest way to put an aileron on your wing is to simply cut an aileron to the desired length and then to tape it to the trailing edge of the wing. This sounds rather more crude than it actually is, as with a little effort , a very neat looking aileron can be produced.

Note: the following diagrams show a right hand wing (starboard) as viewed from above. The left side of the diagram represents the centre of the wing.

Fig 1. (above) shows possibly the most simple of all configurations - basically a near full width strip aileron. The aileron stops before the centre, or root, of the wing in order that the ailerons do not contact the fuselage. Also, the ailerons will have more effect the further they are towards the wingtips.

Fig 2. (above) shows a neater form of aileron installation. Instead of simply taping them to the rear of the wing, a bit of planning during the wing building stage has left a gap for them to fill neatly. There are far too many different possible configurations to show here, but hopefully you'll be able to have fun experimenting and finding your own way to aesthetic perfection!

Fig 3. (above) is a close up of the small gap between wing and aileron - the simplest way to hinge the ailerons is shown. Just lay a strip of clear self adhesive tape across the surfaces. This provides an extremely free moving hinge and can easily be replaced in a matter of minutes any time you need (for example if it has become totally encrusted with dust and grass)
I've tried a good number of different hinges but the one I keep returning to, for its ease of construction and maintenance, is sticky tape. It also adds a negligible amount of weight.

Fig 4. here shows a cross section of the hinge. Notice the gap between the double surface trailing edge of the wing and the aileron. In practice, this gap should be no more than equal to the thickness of your twinwall sheet. This allows for a good range of motion, though you might like to close up the gap if you don't need massive deflection on your flying surfaces.

What size ailerons to use

There are several really quite dull formulae around to calculate the best area of aileron for a given wing. I however, choose the old 'suck it and see' formula.

Let's face it, those equations probably matter if you're building in balsa but for the twinwall modeler, all you need to do is to attach ailerons as big as you think you might need, and then trim them down if necessary following empirical evidence from a first test flight. If they really are wrong, simply untape them, cut some new ones and try again.

As a general rule, I make ailerons pretty large and with really extreme deflections of >45 degrees. That suits my style of flying and, after all, you can always reduce the movement mechanically or on the radio, but it's a whole lot harder to increase the movement.

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