50% is too much. A good rule of thumb is about 80-85% of the fan area for the exhaust. This gives a good combination of static thrust and efflux. The more you choke down the exhaust, the less static thrust you generate, but the faster the air exists the duct. But at 50% it may choke the fan to the point where you may back pressure the fan. You will deffinitely greatly lose your static thrust. What is the size of the airplane? It may be worthwhile to look at a smaller fan...or open up the exhaust.


Chris