Kai wrote:Antoine wrote:Even going up to 90%, the benefit is negligible ( compare 50 watts with the 100 kilowatts of engine power......) that would explain why Diamond didnt bother.
That's exactly what I suspected.
Antoine wrote:However, i believe that the draggy struts also disturb the airflow under the wing and around the main gear wheel pants, and that is not easily quantified
There is an aerodynamic cover for the struts already. I believe it's on all XLS and at least on the new generation DA40s. Or was it only on the nose gear?
Well I don't know. A friend of mine has an XLS, so I will check at the next occasion, but I think there is no fairing either.
The nose gear strut fairing was present on the first models (with the "fat" landing gear) but somehow disappeared on our models.
I think the nose wheel fairing is a bad job, compared to the Cirrus nose wheel (all of the fairings btw).
As to the question about how much gain by properly integrating the landing light, here my answer:
I think we should be careful NOT to seal this cavity completely. We must allow pressure compensation, because we dont know if this is provided for from the wing side. So I will leave a small gap on the lower side.
Bad flow at this point can have significant drag effects, but I don't know how much honestly.
I have bought some foam sealing tape that I will use to properly align the surface of the plexiglass cover with the underside of the wing (there is a 1 mm+ step now!). I will also remove the foam washers and make sure the screws sit very loosely. Then I will cover them with white tape, and cover the seams as well. This way the screws will not be putting too much crack strain on the plexiglass and they cannot fall off by going loose.
This will be a small gain gain, but its nice pleasant work!
If we want bigger gains we must look at the following:
Engine cooling drag and general design of the cowling (can't do)
Ugly finish of the plane at the wing root trailing adge. (can do)
Intersection drag of gear struts to wing. (can do)
In my plane, the stormscope installation and a couple of antennas are also not soooo nice...