Twinwall is a fantastic material for making wings. It's tough enough to handle test flights, easy to work with and above all can be used to make wings in unbelievably fast time. Trust us - you'll be amazed!
The monocoque 'ribless' wing
We build our twinwall wings without ribs. By using the integral strength of the twinwall skin we can create a wing that holds its cross sectional shape without formers. Just like in the construction of the Mugi Evo - by 'building in' stress and tension, the structure we create an object that forces itself to be a certain shape.
Try this... Fold a piece of paper in half and lay it flat on a table. Now with the fold line furthest away from you, push the top sheet forward slightly. Notice how a wing section is formed that holds its own shape with no ribs? Our wings are the same theory but in twinwall instead of paper....
Building a wing in twinwall
A twinwall wing follows the paper principle we just outlined. For the folded wing section method to work and for maximum strength the flutes on the wing must travel from leading edge to trailing edge (TE). This means that the wing will need strengthening along its length, or spanwise.
To stiffen the wing along its length we will build in a spar. This can be any suitable modelling material but here at Mugi we like to keep it pure and simple - preferring to use twinwall, carbon or a mixture of both. The spar not only strengthens the wing along its length but also keeps the section by holding the wing open at the thickest point. The spar is therefore generally placed around 1/3rd of the wing chord back from the leading edge (LE).
The diagram below shows a typical twinwall wing in cross-section. The aileron control surface is made from a separate piece of twinwall and often inset into the wing as shown (though other aileron configurations can be used).
Wings are usually built in two halves, left and right, allowing us to maximise the size of wing that can be built from a sheet of twinwall.