Some time ago, Dick Gossen embarked on an automotive conversion for his Vans RV-12, replacing the factory-supplied Rotax engine with one built by Aeromomentum derived from a car engine.
The result, pictured left with the permission of the owner, was an absolutely gorgeous airplane, christened the DG-12.
Among the many challenges Mr. Gossen faced during the development of this airplane was that of cooling. His kit offered a purely liquid-cooled engine, as is common is cars, rather than the more standard liquid-air combo used in many aircraft engines. This means that his engine relies heavily on its radiator to cool sufficiently: the cooling power of a radiator is determined by the pressure differential between the oncoming wind and the pressure inside the cowling; however, the cowling has intakes so as to provide the engine with the air it needs to run. These intakes reduce the change in pressure at the radiator, reducing its performance and correspondingly the performance of the engine.
There is a solution: a cowling duct. If we direct the air from the intake directly to the engine without letting it escape, we maximize the performance of the engine. The cowling of this airplane is 100 percent custom, so Mr. Gossen needed a 100 percent custom duct. The challenge was designing a system to mount a ducting hose to the cowling, as flexible hosing is not complex. This challenge is easily solved with additive manufacturing prototypes.
The actual design and prototyping process took several months, and picture above are some of our iterations. Top left was a model for mounting a light (a surprise benefit of the design), bottom left was my design fresh off the printer, which was dimensionally accurate but too thin and brittle, and right is one of my earlier prototypes, featuring a hand-crafted 3 inch inner diameter laminated craft paper tube, as such as thing for some reason did not exist in my price range. This prototype has flown in Mr. Gossen's airplane. I used a high-strength and high-temperature photosensitive resin in an Anycubic Photon MSLA printer for prototyping.
After many iterations, I manage to get an American manufacturer to turn and anodize (unanodized left) our part for a reasonable price. This part kills two birds with one stone in that it both acts as a cowling duct and a light mount with its 3 inch inner diameter.