Giant Yak-54 Trim Question
05-04-2005, 08:54 PM
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Giant Yak-54 Trim Question
This question is for Mike.
I'm in the late stages of trimming my 79in Yak, and have a question about aileron placement.
Adjusting for straight down power-off dives, I have found I need to droop ailerons so they are flush with the top of the airfoil.
I figured they would be "neutral" straight through the airfoil section (i.e. Parallel with the thrust line)
Instead, they are lowered about 5-10 degrees from my initial setup.
CG is set for hands off upright/inverted flight at half throttle.
No pitch changes power on/off, so I'm satisfied up/down thrust is close enough.
Lateral balance is set. Sustained knife edge flight requires almost no corrective input.
This is all with the ailerons trimmed down as above. Flies great this way, so I've just left them there.
Plane was built with wing/stab incidence set as close to zero as I could measure them.
Just wondering how your prototype planes were set up.
If this sounds abnormal, what do you suggest I look at?
I'm in the late stages of trimming my 79in Yak, and have a question about aileron placement.
Adjusting for straight down power-off dives, I have found I need to droop ailerons so they are flush with the top of the airfoil.
I figured they would be "neutral" straight through the airfoil section (i.e. Parallel with the thrust line)
Instead, they are lowered about 5-10 degrees from my initial setup.
CG is set for hands off upright/inverted flight at half throttle.
No pitch changes power on/off, so I'm satisfied up/down thrust is close enough.
Lateral balance is set. Sustained knife edge flight requires almost no corrective input.
This is all with the ailerons trimmed down as above. Flies great this way, so I've just left them there.
Plane was built with wing/stab incidence set as close to zero as I could measure them.
Just wondering how your prototype planes were set up.
If this sounds abnormal, what do you suggest I look at?
05-05-2005, 09:37 AM
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RE: Giant Yak-54 Trim Question
Well first thoughts are we don't fly too many straight lines with the profiles but given that everything should be nuetral with wing and stab incience, it should draw a straight line. Engine thrust and balance will be a factor. One thing I would check is the nuetral position of your elevator while static on the ground. If it's not even with the stab then that is an indication of the cg being off one way or the other. The other thing to check is engine thrust line. Some pattern and IMAC style flyers believe you need down thrust (engine pointed down) as well as right thrust for proper performance. If you have the plane set up and it will fly nuetral both right side up and inverted then I'd say you are right on the cg point.
05-05-2005, 09:49 AM
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RE: Giant Yak-54 Trim Question
Silly me for trying to trim a profile like a pattern plane. [sm=bananahead.gif]
I was going to update my earlier post, but you beat me to it.
Elevators are in line with the stabs. (First thing I checked)
Flies great the way it is, so I'm not going to lose sleep over this.
I was thinking I was missing a kernel of aerodynamic theory, and this might really be the way it should be.
I'll re-measure everything next time I have it assembled on the bench.
I was going to update my earlier post, but you beat me to it.
Elevators are in line with the stabs. (First thing I checked)
Flies great the way it is, so I'm not going to lose sleep over this.
I was thinking I was missing a kernel of aerodynamic theory, and this might really be the way it should be.
I'll re-measure everything next time I have it assembled on the bench.
