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02-18-2014, 07:02 AM
Join Date: Aug 2009
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Club: Sky Corral
Just wanted to get a different opinion on what I am trying to do with this model, to see if Iím thinking correctly or not.
I designed and built this Navaho Missile that stands around 42Ē tall ready for take off, and yes it takes off under rocket power then the winged portion is powered by two small 27mm EDF units.
The model is for a National Scale Rocket Contest this summer. Instead of having the model glide back to the ground unguided, it will be RC controlled! To add realism in flight I thought I would add a couple of fan units to just help the model stay up an extra 15 seconds or so since this model doesnít have a lot of wing area.
So since the model will already be at altitude, about 400 feet up the fan units only have to provide thrust to keep the flight speed up so I can execute a couple of controlled turns and land back at the field. The model doesnít have to climb just have a controllable descent. Ready to fly back to the ground it should weigh about 16 oz.
Assuming I can get about 3 total ounces of thrust from both fans unit, should this be enough to extend my flight time?
The other issue that may make things a little harder on the fan unit is that the although I figure I have about .812 sq. inches on intake area for each fan unit, while the fan unit itself has about .742 sq. inches of swept fan area, the intake shape isnít optimized nor will there be any ducting.
One image shows the inside of the fuselage and the former where the two fan units will be mounted. As for exhaust exit area I've got tons, since the real Navaho used Ram Jets for power. I figured I would keep the duct exit diameter same as the fan shroud.
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