COG and thrust location problems.
 

Have built a 72" solid blue foam A-10 Warthog. It replaces the 80" I backed over with my own car.

Can I mount a single EDF unit in the 6" wide X 8" high area of the COG with the blast angled SLIGHTLY downward at a angle thru a full sized open exhaust hole.
I realize the foward thrust is reduced more & more as the downward angle is increased. I think that more angle would cause the plane to lift straight up also.
Is this the same as a center mounted pylon engine on top of a powered glider?

I assume "C" is best. but are "A & B " livable ?

Thanks

RE: COG and thrust location problems.
 

That will work
The plane will not lift straight up but the position - is such that it should (if'n all is within good power to weight)
help get going from a standing start.
It is sorta like early stuff called JATO on old full scale craft where power was marginal and take off needs would out run the runway length.

RE: COG and thrust location problems.
 

Is there any advantage to a short steeper angle like " B " or to a longer shallow angle like " A " ?

RE: COG and thrust location problems.
 

I just helped a friend with his trimming of a glider that had it's electric motor in a nacelle that projected forward from the vertical fin. He had chosen to solidly attach it with downthrust because "most models need downthrust" and they usually had about 4 degrees but the designer hadn't drawn any on the plans. Bad news was it sucked and was almost impossible to fly. Good news is that the unbalanced prop trashed the motor mount and he had the opportunity to readdress the mounting setup.

The best advice for an experimental (and all prototype designs are basically a combination of many smaller experiments) design would be to make sure of one thing. Build your model so that it is as easy to adjust your thrust line as it is possible to do so. And approach your power applications on the first flights gradually or at least with extreme concentration.

There is a reason every major airframe mfg has at least one wind tunnel. And history is filled with many designs that needed modification after it's initial flight tests.

RE: COG and thrust location problems.
 

Check me out on this thought.

I was concerned about the angle of the EDF fan in the body. That really has no effect. Only the location and angle of the end of the exhaust stream ??
So a front -bottom- intake to a EDF unit blowing as straight as possible to a foot before the horizontal stabilizer should give me the least trim out out problems ? I Have measured the thrust angle of a rear most exhaust & it is about 5 to 7 degrees of up angle.