snips.......

Well as Chrissi pointed out if you move the prop aft you risk prop strikes.
If you use a 2.17:1  PSRU and go down on the prop dia. to run it at 3600
the engine will run at 7800 RPM. More HP. Doable I guess. What diameter do you need
to run the tips at .8 mach and 3600 RPM? You will sacrifice takeoff
performances which is already not too good on canards.

I still like Vance's Idea. Profile will not be that bad as the top of
the cowl/ canopy can go straight back.

Paul Lamar

Paul, A caveat here as I have no time in type with a canard, but my high time friends tell me that more than one high speed
taxi
has turned into an inadvertent first flight when  the throttle was closed and all that down force on the canard from the
already
high thrust line was removed.

Rick

Sounds like a design defect to me. Lengthen the nose gear strut with a hydraulic
cylinder. Also increase the down thrust angle on the engine.


The tail on the prototype ME262 would not come up until the pilot hit the brakes
around 100 MPH.

Paul Lamar

Paul, Why a design defect? Lift increases with speed so at cruise the canard is balanced by the engine thrust, but at rotation
there is a downward component caused by high thrust and less lift. Even a lowly machinist can picture the vectors involved. ;-)

Rick

Proper design takes all modes of operation into consideration.
Just before an airplane takes off, and this applies to any airplane,
a rotation to near max angle of attack occurs (just short of stall).
If the angle of attack of the wings sitting on the gear is
negative all the speed in the world will not get you
off the ground. Same goes for a too high thrust line.
Any airplane must be able to rotate to near max
angle of attack when the lift available at that angle of
attack and speed equals the weight of the airplane.

Rutan limited the control authority of the canard to prevent
stall of the main wing. This means the canard also has a limited
ability to rotate the air plane at what should be the take off speed.

There fore the way to fix this is lengthen the nose gear and 
increase the angle of attack of the canard and the main wing
while the airplane is sitting on the ground. The canard, being
well ahead of the main wheels, will have a larger positive moment 
to overcome the negative moment caused by the high thrust line.

Takeoff distance will be shortened and the airplane will not jump 
off the ground when the thrust is reduced as you claim happens.

On landing leave the nose gear strut as short as it is now.

The Germans fixed the ME262 take off problem by going to tricycle gear 
thereby raising the tail.

Paul Lamar
 
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