Does down thrust push a jet down or up?
 

I would think I would push it up???

RE: Does down thrust push a jet down or up?
 

It depends where the turbine is mounted of course, but in the case of your Velox, down thrust will help push the nose DOWN. The Velox has a natural tendancy to want to climb at higher throttle settings. The stock mount is not set-up for straight and level at all speeds.

RE: Does down thrust push a jet down or up?
 

easy:

your CG is the centre of the balance

you push at the back from down to up - nose goes down.
you push from the back up to down - nose goes up..

most of the jets or delta,s have the thrustsetting from down to up..

RE: Does down thrust push a jet down or up?
 

if it is for your velox
this is what i recomend :

mount in the front of the mounting clamp about 10mm this will give about 4 degrees downthrust.
at higher speeds you will notice that it will fly strait , and flying inverted with no pushing the elevator.

RE: Does down thrust push a jet down or up?
 

Thanks, that's what I needed to know. I will take out the down thrust until I fly it at WOT!:)

RE: Does down thrust push a jet down or up?
 

WOW

RE: Does down thrust push a jet down or up?
 

FWIW, here's what's going on with some (especially, but not exclusively) twin boom designs:

The high velocity jet efflux blasting underneath the stab creates a low pressure zone which then "sucks" the stab down, rotating the nose up. (For a demo, place a sheet of paper against your chin and just under your lip, holding the paper from the edge so that it goes up at first then curls away from as it sags over your fingers toward the ground. Blow across the top of the paper and you'll see it "lift" away fro the floor)

The higher the throttle setting, the more the stab is affected. Twin boom designs which have taller vertical stabs are not as affected because the stab is farther away from the jet blast. Shimming the front of the engine mount counters the problem by rotating the efflux away from the stab even as it uses the jet blast to hold the nose down.

They key is to find, through advice from trusted sources or through your own experiments, what amount of shimming results in the fewest/smallest trim changes over the widest range of speeds. It will vary slightly depending on your particular engine and CG, so don't be disappointed if you need to "tweak" your settings......

Hope this helped, Don.

RE: Does down thrust push a jet down or up?
 

Great. thanks a bunch Don...:D