Catching up on some emails from a week back. What exactly is the perceived problem with elevator cables ?
If anyone feels the need to make long pushrods, then make them out of pultruded carbon fibre - very light and much stiffer than 4130. NACA ducts They don't ram air, there has to be low pressure inside the cowling for them to work, all they do is suck air out of the boundary layer close to the surface of the cowling without presenting too much in the way of disturbance to the airflow over the cowling. They work on fast cars, because most cars are designed to have low pressure under the car to help suck it down on to the road, They will only work effectively on an aircraft if there is somewhere for the air to escape. You make air escape by having a hole somewhere under the plane and allowing the venturi effect to suck air out, it's best to have the hole under the plane, as it "looks better" and also this turbulent air is less likely to batter the tail feathers and also it saves getting oil streaks over the expensive airbrush work. Like all things to do with aerodynamics, they need careful design and a lots of trial and error ( or expensive computer simulation ). I suspect on most production cars they are pretty well useless - they are there to sell cars and serve no other purpose. I suspect NACAducts are just about as useless on kit aircraft as they are most production cars. Pete
