Building a truss-braced model airplane: sense or nonsense?

After NASA’s recent results with truss-supported wing airplanes and the benefits this could bring to full-size airplanes, (Think Flight) figured that if it helps with these airplanes, it might be a boon for model airplanes as well. With the recent construction of an aviation aircraft for smaller drones, he decided to give the concept a whirl to see if it would make a difference compared to a regular wing design. This aircraft has a payload bay that can be opened in flight to release the drones stored inside, making any potential increased payload capacity and flight performance improvements very welcome.

The truss-supported wing design has been studied by NASA and Boeing, with the design offering a high aspect ratio not unlike the wings of a glider. The obvious disadvantage of the long, narrow wings of a glider is that they are also long and fragile, which are not desirable characteristics on a commercial jetliner. By adding the truss bracing, the wing design can be optimized for high aspect ratio, while the fragility is compensated for by the spars. For a commercial jetliner, this can mean significantly less fuel consumption.

As (Think Flight) found, the typical problems with scaling wings up and down were also evident here, with the Reynolds number explaining the ‘why’ involving the chord length of the aerofoil, which is obviously different from a full-size jetliner and a model you can hold in your hand. Effectively, this means that on a model scale the effect of higher aspect ratio is not as pronounced as it is with jetliners, although the trusses may provide some advantage in structural stiffness.