I was reading this thread from Chip Hyde,

http://www.rcuniverse.com/forum/m_14...tm.htm#1414420

and it got me wondering if we could use a rudder to throttle mix on the profile planes and their style of flying instead of the conventional way of adding washers under the engine to get right thrust (which I hate doing), any comments?

Mike

I don't see why you can't, but adding a few washer takes just as long...?[&:]

Hmm...lets see what everyone has to say because I'm not the smartest kid here.

Dan[8D]

I should mention that the reason I hate adding the washers is because imo it is a terrible way to attach the engine to the fuse, with no washers you have two nice flat surfaces mating together, now when you add a washer you have completely blown that and now you have on the engine contacting the fuse on a few small point which puts alot of stress on the fuse and eventually will wear out the connection, the washer will end up imbedding themselves into the fuse over time as you continually need to tighten the bolts. The right way to do it would be to machine tapered shims to go under the motor, but this is complicated and not adjustable. Last night I made a new aluminum mounting plate for my ff540p (to cover up the damage caused by the washer method) and bolted the motor on with no right thrust, I will try the mix and see how it works.

Mike

Mike,
I too am interested in this for the same reasons you stated. Plz let me know how your test comes out.

thanks,
Kenny

I learned this trick from ChuckAuger and it works great.

Get yourself some G10 fiberglass material from an electronic/industrial surplus place.
Cut to shape and laminate several layers together using CA to get an appropriate thickness.
Using a sanding block, taper the flat edges to give yourself the offset you need.
Drill and mount. Hard as a rock and structurally sound.

Just takes a few minutes to make. You will never use washers as as shims again.
I have retrofitted all of my profile planes this way. This would work for firewall mounts too.
Here is a picture to help you visualize. The shims are under the motor beams.

Looks good Marty, the only problem I see is that it is not adjustable after installation, I guess if the mixing works it would be nice because its infinitely adjustable at the field. How much R thrust are you guys using on the OMP 47" edge? And what kind of test are the best to determine if you have too much or not enough? thanks

Sure it's adjustable!

Loosen 4 engine bolts.
Back 2 out completely, and set aside.
Slip out the fiberglass shim.
Adjust angle using sandpaper, a flat surface, and a little elbow grease.
Put the shim and bolts back in.
Repeat for the other side.
Tighten everything back up, fuel up and fly.

Takes 5 minutes, using tools you probably already have at the field anyway.
On the OMP 47" Edge, shoot for 2-degrees right thrust and adjust from there.

I prefer to adjust my plane mechanically first, then work from there with mixing.
But then again, I'm no Chip Hyde either.

Didn't think of sanding it, that's a good suggestion. I think I'll try this out anyways just to see what happens. I should have the plane back together in about a week, I'll keep you guys posted.

Oh yeah if anyone has a good procedure for flight testing for the amount of right thrust let me know, I'm sure I can find it if I search a little, just being lazy I guess.

Mike

I read that thread also about using mixing instead of adding right thrust to the engine...

From my point of view... I have to ask... WHY??

They both do exactly the same thing... and I'd go one further and say that right thrust added to the engine is AUTOMATIC... for example... you adjust the needle valve on your engine and it's now turning a different RPM than what you did before. With right thrust, the more thrust the engine puts out, the more it pulls slightly to the right to counteract the left turning tendencies of the engine. IF you set up rudder mixing with throttle, and your engine is putting out more or less than what it did when you set up your mixing, you now have a funky flying airplane because the radio doesn't have a clue how much power the engine is putting out... it is just adding rudder in a corresponding amount to throttle setting... with no regard to the actual power output of the engine.

I know that Chip has a lot more clout than I do and could out fly me any day of the week, but I think his idea is just a way to get off the building board and into the air a little quicker. Anyone who is familiar with programming their radio could program in that mix in about 1 minute, and then tweak it once they get out to the flying field, whereas it may take you 30 minutes or more on the building board to get your engine properly set up with the correct amount of right thrust built in.

But once your engine is mounted right, it's always right. If you mix rudder, it's only right when everything's right... if the engine is a little bit off on power output (either higher or lower), then you're yawing through the air when you shouldn't be, draining your battery pack and stressing your rudder servo needlessly.

Chip's method is just letting the computer in the radio do work that should have been done by the human on the building board.



Soapbox off.