hello all,

I am in the process of building a canard wing model withengine mounted at therear with apusher prop configuration and I was wondering if it would be benificial to mount the engine with a little 'up thrust' and' left thrust'asI have seenon someplans it seems to bequite common to haveengine with tractor configuration mounted with somedown thrust and sometimes right thrust.The plans don't call for it but I have heard this model I am going to build needs the foreplane elevator with some down elevator to keep the nose up.
Any help would be greatly appreciated, thanks.

Mick, If you don’t mind looking at me as I age, here are the images of the canards I built. The first three were set up 0-0-0 and they all required an eight of an inch up trim. The fourth one had two degrees of up incidence in the canard and it required no trim. The last one has two degrees of up trim in the canard and requires an eight of inch down trim. All the engines have no thrust angle built in.

Here’s a good website to help with the cg. I find it very accurate.
http://adamone.rchomepage.com/cg_canard.htm

Dan.

All the forces acting over any airplane make it rotate around the CG, if they have a combined lever respect to that point (thing spatial point here).

Undesired rotations is what the down and right deviation of the thrust achieve for tractor configuration.

Down thrust helps reducing or eliminating the lever respect to CGs that are high, so the airplane doesn't show a nose up tendency with power application.

Right thrust helps increasing the lever respect to the CGs (located over the center line, if the plane is laterally balanced). By doing that, the designer introduces a yaw moment or torque (to the right) that compensates for the left yaw moment associated to the P-factor and gyroscopic precession of the propeller, so the airplane doesn't show a nose left tendency with power application, especially for tail draggers.

http://en.wikipedia.org/wiki/P-factor

http://en.wikipedia.org/wiki/Precession

Consider how those forces could affect your design for deciding on any thrust angle.

If yours is a trike, you will not need much, if any, left thrust.
If your engine is about the same level than both wings, you will need zero upthrust.

Hi k1404
On my Canards with Pusher Prop, I mounted the engine with zero side thrust and no vertical offset. The Canard wing was mounted with a few dergees + incidence. Flew great. I suggest you learn to go to full down elevator as soon as the mains touch down during a less than perfect landing. The Canard has a tendancy to have the front end bounce up during a high wind rough landing. A few times mine has gone to near vertical just a few feet off the ground. Without a plan, you are done!

That Trimotor looks awesome! How did it fly? I could swear I saw some of those planes in RCM or MAN as construction articles. Are they your designs and are they published?

Don

Thanks for the compliment hattend. All five of the canards flew great. A couple of them had hair raising first flights, that I survived, and was able to tame them with an adjustment to the CG, Yes, the first three were published as construction articles in Flying Models. Dan.

I added the thrust changes. I don't think it made much of a difference. The plans called for it though.

http://www.youtube.com/watch?v=vX1d8JgIXKs

I am running with bad internet. Use the link to see my latest plane.

I added the thrust changes. I don't think it made much of a difference. The plans called for it though.

http://www.youtube.com/watch?v=vX1d8JgIXKs

I am running with bad internet. Use the link to see my latest plane.

thanks mate, that makes sense but as the plans dont call for any thrust angle left or up, I will stick to what the plans call for, sorry, I was just thinking outside the box a little.

Brining my astoblaster up to speed with electric power instead of rocket engine boost.
New to electric.
Question..... 920Kv 11.1 VDC Lipo
Need advise on pusher propeller

It really doesn't matter that it's a pusher or not for electric power. You just use a regular prop mounted backwards on the motor and it is now a pusher prop.

We'd need more specs on what motor it is. And even then typically there's a little testing needed to sneak up on the power level you want without burning out the motor. So don't expect a solid answer.

The other thing I see is that you are running a 920Kv motor from a 3S pack. At that Kv and voltage the motors are usually rated more for larger and slower turning props. Like 9 to 11 inch diameters. Such motors are more useful on powered gliders or 3D flat foamie models that want big fine pitch props for flying and don't want the prop size to make the motor burn out. But for something like the Astro Blaster I'd imagine you would want more speed. For that you want a motor with a Kv value up more around the 1800 to 2000 range so it can run a smaller prop at higher RPM and really make the AB zip.

So you might have the wrong sort of motor for what you are doing.

Finally this is more about picking the prop size than about canard designs. Don't be afraid to start a new thread instead of pulling up an old one. In this case it would have made more sense.

My limited experience with canards resulted in a need for "upthrust" on the pusher engine. By that I mean that high engine power will then tend to put the plan in a climbing attitude (by pushing the tail of the aircraft down). This was after initial trials where the plane would NOT lift off, until I killed the throttle - at which time it would leap off the ground. The change in the thrust angle solved the problem. Now this might have been a result of a draggy undercarriage, lowering the aerodynamic center of the plane. I don't know. The plane survived, although had to be rebuilt a couple of times.

Hi mick 1404, my answer to your initial question(if still relevant) about canard pusher engine upthrust would be: YES..! Most of my earlier pusher canards have used 0-0 engine mounting and they all had a tendency to initially dip the nose when I slam the throttle(s) into full bore. I interpret that as the rear engine pushing down the nose a bit. My latest FSW design therefore use a bit of rear engine "upthrust".
What happened to your canard mick1404..?!