Bill:
ORIGINAL: BillHarris
That is a good setup on the engine nacelles. My first thoughts were to mount the engine nacelles below the wing, but I'm starting to think along the lines of mounting the engines along the chord line, as you have done here.
With a high wing, as you have here, you will find much less difference between power on trim and power off with the engines under the wing. For neutral trim with throttle has to be on or slightly above the line of the vertical center of gravity; if the plane is hung by the prop shafts it should hang vertically. At least that's a place to start, as, believe it or not, the ideal position changes with speed. Remember drag?
As the air speed goes up the drag will also increase. Since the wing gives a large percentage of the total drag, the high wing all by itself will tend to make the plane go to a nose up trim with increasing air speed. This gives an amount of automatic airspeed control, but at the same time it also gives you effective up trim to the thrust line.
The compromise that works for me is to estimate the drag center line and the weight center line, and put the thrust line 10 to 15% of this distance above the weight center line.
One of the tricks to preclude tip-stall is to make the LE of the inner wing sharper so that it stalls before the outer wing. JOOC, does sticking engines on the wing alter the stall characteristics of that wing section? I can see that the airflow behind the engines can be markedly different than if the wing were moving through the air.
Increasing the leading edge radius from the root to the tip is a trick that works very well. it gives the effect of washout without having it work against you in inverted flight. The new Funtana from Hangar 9 is the first popular model I know of using this.
On an airplane not intended for aerobatics washout works just as well, and I think the wing with washout just looks better.
And the lost prop wash over the wing behind the dead engine is the second major cause of the airplane turning into the dead engine - the wing loses lift. the plane tends to roll.
Think I've covered it, If I missed something or wasn't clear ask again, please.
Bill.