Author Topic: Stab AoA with pusher? (Read 20301 times)

Peter Germann · « **on:** April 10, 2013, 04:02:21 AM »

Advice seeked for:

On both of my last two electric pusher prop airplanes (Max Bee derivates, see "list your Set up", reply 127, march 6 2013), I have installed the stabilizer with a positive AoA of approx 0.5 -1° (LE up) and motor thrust axis is set to 1° up. While flying very good, both airplanes show a tendency to be unstable in level flight and more so in inverted. The instability is such that the airplane does not hold altitude by itself.
Could it be that, due to the prop spinning the other way, the so far well proven "0.5° stab up" rule holds no longer true?

Thank you for advice, Peter

Brett Buck · « **Reply #1 on:** April 10, 2013, 08:37:30 AM »

Quote from: Peter Germann on April 10, 2013, 04:02:21 AM

Could it be that, due to the prop spinning the other way, the so far well proven "0.5° stab up" rule holds no longer true?

Yes. Easy to determine, just spin it the other way and see if it gets better.

It's not a rule, it was an observation, based on certain other conditions (nose-up precession from a conventional prop rotation). Now you have changed the conditions.

Brett

Doug Moon · « **Reply #2 on:** April 11, 2013, 10:08:24 AM »

Did you say you have the Stab up and the Motor up??

Typically with the tractor props stab up and engine down works well together. Or engine at 0 and stab up.

If you can set the motor at 0 try it out and see what happens. At first glance I wouldnt think up and up will work to well together....

Howard Rush · « **Reply #3 on:** April 11, 2013, 10:48:24 AM »

Quote from: Doug Moon on April 11, 2013, 10:08:24 AM

At first glance I wouldnt think up and up will work to well together....

I don't know about you, but the Jive Combat Team is on the up and up.

Air Ministry . · « **Reply #4 on:** April 11, 2013, 08:50:48 PM »

Its a bit like one of those old nasty 911 Volkswagens , where the motive force is behind the aerodynamic center & the Centre of gravity ,

youl need to angle one side UP & one Side Down , for the rotational prop wash .

Think the a.o.a. of stabs more related to divergance from wing / thrust centerline .
As in if all the air from the prop whizzes past one side . . .

Peter Germann · « **Reply #5 on:** April 12, 2013, 04:50:37 AM »

Quote from: Doug Moon on April 11, 2013, 10:08:24 AM

Did you say you have the Stab up and the Motor up?? Typically with the tractor props stab up and engine down works well together. Or engine at 0 and stab up. If you can set the motor at 0 try it out and see what happens. At first glance I wouldnt think up and up will work to well together....

I've had a couple of Trivial Pursuits (and derivates) with PA 75's and tractors. All of those had 1° motor down and 0.25 - 0.5° stab up. They all tracked excellent both level and inverted.
When going electric and pusher I thought it would make sense to compensate the (inverted) precession force by installing the motor with 1° up.
Furthermore, as I was not able to figure out whether the prop spinning backwards has any influence on the effect of positive stab AoA , I left the 0.5° stab up unchanged, which may be why tracking is now gone...
What I've done meanhwile is taping 1/8 x 1" balsa to the first third of the bottom side of the stab, trying to reduce its AoA. The gauge says its now almost 0° and wheather permitting I will test fly on sunday. Next I will follow Brett Buck's much appreciated advice of testing a tractor prop.

Igor Burger · « **Reply #6 on:** April 12, 2013, 05:12:06 AM »

Hello Peter,

I think that since we use models with landing gears down, thrust line over center of drag (over the wing) and also over the CG, the tractor prop will always get more symetric flight.

If you want use pusher, I would expect also motor up and also stab down configuration, but I can say that I never got as good trim with pusher as I had with tractor. May be "all in line" will be better configuration for pushers, but still, landing gear is on opposite side as precession and p-factor need to be ballanced.

Peter Germann · « **Reply #7 on:** April 12, 2013, 06:07:53 AM »

Quote from: Igor Burger on April 12, 2013, 05:12:06 AM

Hello Peter,
I think that since we use models with landing gears down, thrust line over center of drag (over the wing) and also over the CG, the tractor prop will always get more symetric flight.
If you want use pusher, I would expect also motor up and also stab down configuration, but I can say that I never got as good trim with pusher as I had with tractor. May be "all in line" will be better configuration for pushers, but still, landing gear is on opposite side as precession and p-factor need to be ballanced.

Thanks for comment, Igor
Flying constant RPM pushers, I find the resulting nose-out moment in outside loops quite helpful and I am willing to trade-in the resulting increase of line pull in the upper loops of the vertical eights and the upper corners of the hourglass against a (slight) lack of symmetry. The reason for this being that as a pilot I can deal, up to a certain degree, with assymmetry but there is not too much I can do for line pull. Related to my current problem, I am therefore not so much concerned about assymmetry, instead what really needs to be improved is tracking or "groove" in both level and inverted flight. If needed, I will have to do major surgery to get 0.5° down stab instead of the 0.5° up I have now.

By the way, from the first perhaps 20 flights with my new Max Bee Two, it seems that adding a Rabe rudder being coupled to elevator up seems to help against the slight loss of tension resulting from pusher induced nose-in moment in inside loops.

A bit of topic but related to tractors: When I did a couple of test flights with the Meizlik 11.5 x 5.5 3-blade tractor, the most significant effect, besides considerably higher current drain, was the airplane rapidly turning inwards during spool-up in take-off run. This was quite frightening and cought me unexpected. I must add that I fly form hard surface w/o helper or stooge. No way doing so regulary...

rgds, Peter

Igor Burger · « **Reply #8 on:** April 12, 2013, 06:56:57 AM »

Quote from: Peter Germann on April 12, 2013, 06:07:53 AM

I find the resulting nose-out moment in outside loops quite helpful and I am willing to trade-in the resulting increase of line pull in the upper loops of the vertical eights and the upper corners of the hourglass against a (slight) lack of symmetry. The reason for this being that as a pilot I can deal, up to a certain degree, with assymmetry but there is not too much I can do for line pull.

I do not mean symmetry as reaction to handle, I mean symmetry as tendency to pitch up or down without elevator input, because it could be a reason for hunting. Yes, asymetric reaction can be cured either with elevator to flaps position or handle leodouts etc, but it can add another troubles while trimming. Simply since you have landig gears down and wing also, you will need less elevator deflection to fly straight with tractor compared to pusher. That kind of asymmetry I mean.

Quote from: Peter Germann on April 12, 2013, 06:07:53 AM

Rabe rudder being coupled to elevator up seems to help against the slight loss of tension resulting from pusher induced nose-in moment in inside loops.

Yes that is the way I solved probles in second corner of hourglass with tractor. And not only, Max Bee has wing located little under CG, it means CG moment tends to roll model out and motor moment and aslo flaps must ballance it ... and now, in situation when model goes up to second corner of houglass, when the gravity kills little of line tension, model with tractor tends to roll in - what makes that secon hourglass corner safer (like little more tip weight) ... pusher will do it just opposite :-))) ... whole that model is simply designed around tractor, pusher cannot help him(theoretically - with straight model without any other issues).

Quote from: Peter Germann on April 12, 2013, 06:07:53 AM

When I did a couple of test flights with the Meizlik 11.5 x 5.5 3-blade tractor, the most significant effect, besides considerably higher current drain, was the airplane rapidly turning inwards during spool-up in take-off run.

Yes, it is illness of such small prop front of so large asymetric nose. Pusher helps in that case. However model must keep its position to lines also with change of power or thrust. If you will move leadouts little back and if you give little more rudder out offset, it will be cured. Model MUST keep its position regardless of prop thrust. You can check it when motor stops, if model yaws somewhere, then you have something not so well trimmed - either rudder, or LO position or motor out offset. And in that case it will be magnified at startup. However there is one important thing at startup, many people tend to pull elevator UP at startup, tractor prop Rabe rudder will move rudder in, and that will do just that what you explored.

That effect can be little bit minimized if motor thrust line will be moved little bit down, but it will need to be compensated either by motor down or stab up offset.

Valentin Apostolov · « **Reply #9 on:** April 13, 2013, 03:47:46 PM »

My knowledge over that topic came some time ago when I read the article in 'American modeller', December 1967
by Bill Netzeband (Control-lineAerodynamics Made Painless)- Part 3.The prop acts a gyroscopeas it is rotating mass generating enough troubles. Of course at that time we did not have 'Rabe' or fixing the stab at + angles. Any how if read this the rest is at your fingers and mind. A few calculations are needed. Any how I had no problems since then, Exept many flights and trimming with knowledge. Always used light proppellers. Thank you./

Valentin Apostolov

Air Ministry . · « **Reply #10 on:** April 13, 2013, 11:58:32 PM »

Have a similar problem on a .46 ship at the moment . A bit touchy , better with ST muffler than tounge , ( noseweight ) . BUT
issue is jeryness & a slight looseness ( lines ) turning outside high . A Yaw out ! Fudge .

ANYWAY , haveing spent a Friday Evening eliminateing dual elevator horn slack on a machine . It proceeded to wave & weave , level & tochy on straight legs .
Untill I spent the next Friday evening chopping into it again & fileing out the bushes .

Still a slight ' irregularity with 3 / 4 mm slack at elevator trailing edge . The ORIGINAL 5 mm at T.E. free movement , meant that initial repose on the flap varied lift slightly
NOT affecting A.o.A. .With NO elevator slack initial responce was on pitch / Angle of Atteck , so small corrections roller coasted .

THEREFORE this bothersome ship is going to get reamed in the Elevator Horn . To achieve 5 m.m. free play at the trailing edge of the elevator .

THINKING ABOUT IT . Your pusher set up will be enhaceing elevator responce , and lowering Thrust ' power assistance ' to the FLAPS .

Small incremental alterations in lift through the flaps achive steady course . Where elevator action alters track .

Afect is the same as the thick tailplane blanking initial thinner elevator effect , that some favour .
So , to check that , you can fit a sheet of 1/16 sheet , to Both Sides of the Tailplane .

.

Tailplane offset from wing , affects induced tailplane A.o.A. , as its in wingwash , proportional to load . So incorrect can get it weaveing in rounds due to
varying force requireing further correction for trim . Thus ' the Trim wheel ' setting @ various loads / speeds , on F.S. Aircraft .

Any chance of a picture or two of youre aeroplane . ? .

Peter Germann · « **Reply #11 on:** April 14, 2013, 03:35:44 AM »

Quote from: Matt Spencer on April 13, 2013, 11:58:32 PM

Have a similar problem on a .46 ship at the moment
Any chance of a picture or two of youre aeroplane . ? .

Play: I have flight tested elevator play on my last airplane which suffered from the same problem, however to a much lesser extent. Result was negative, so I went back to ball links.

Elevators thickness: Elevator LE thickness is equal to stab TE. Elevators LE is sharp.

At this point in in time, I am about to do flight tests with an 1/8 x 1 in balsa strip taped to the front bottom side of the stab, kind of "simulating" a smaller AoA (approx. 0° as per the Robart Model Incidence Meter).

For airplane specs see: "List your Set Up", reply 127 march 6 2012

Peter

RC Storick · « **Reply #12 on:** April 14, 2013, 11:30:31 AM »

Quote from: Peter Germann on April 14, 2013, 03:35:44 AM

For airplane specs see: "List your Set Up", reply 127 march 6 2012
Peter

Peter this is a beautiful aeroplane.

Howard Rush · « **Reply #13 on:** April 14, 2013, 12:36:19 PM »

Quote from: Matt Spencer on April 13, 2013, 11:58:32 PM

THEREFORE this bothersome ship is going to get reamed in the Elevator Horn . To achieve 5 m.m. free play at the trailing edge of the elevator .

THINKING ABOUT IT . Your pusher set up will be enhaceing elevator responce , and lowering Thrust ' power assistance ' to the FLAPS .

Small incremental alterations in lift through the flaps achive steady course . Where elevator action alters track .

It depends on where the elevator would float with no control input in level flight. If you need to deflect the elevator away from the "stick-free" position to get the plane to fly level, I don't think putting a deadzone in the elevator control horn would help. I had an airplane whose elevator control horn wore severely. I couldn't tell any difference in how it flew as the hole in the horn grew. I suspect the stick-free position was somewhere innocuous-- maybe more up control than needed for level flight, but less than needed for round insides.

Quote from: Matt Spencer on April 13, 2013, 11:58:32 PM

Tailplane offset from wing , affects induced tailplane A.o.A. , as its in wingwash , proportional to load . So incorrect can get it weaveing in rounds due to
varying force requireing further correction for trim . Thus ' the Trim wheel ' setting @ various loads / speeds , on F.S. Aircraft .

The downwash angle varies with tail height, but I think you are thinking of the rate of change of downwash with angle of attack. That's what's destabilizing. I wouldn't think that would be worse as the tailplane is offset vertically from the wing centerline.

Air Ministry . · « **Reply #14 on:** April 14, 2013, 08:43:44 PM »

PUSHER .

Pusher ? YOU said PUSHER .

oops . Definately need a whistling with eyes elsewhere icon .

Air Ministry . · « **Reply #15 on:** April 14, 2013, 08:50:48 PM »

Bother .

Youve got a fairly wide Stab. chord .

Ive run 3/32 incidance on 4 in chord , which is a degree . If im not mistaken . Same as 2 m.m.
on Airfoild Stab , Nearly Always use a bit with vertcal seperation of centrelines . Avoids the old
elevators set flat on bottom face trick .

Flown a few clockwise circulateing A/C , one on Saturday ! .
Being a Aerobatic floatplane , its to keep the lines tight on takeoff .
It walks OUTWARD .

Line tension is more even . But we all know that .

Cant see its other than mirror image to yours .

Fin / Rudder offset less needed . Rudder / Tourque counter rather than cumulative .
so think issues seperate to that .

Theres reasons some of us have dusty models .

A mixture of kerosene, clay powder, and DayGlo™ pigment is applied to the model surface with the wind off. When the wind is turned on it causes the kerosene to evaporate, leaving streaks of clay powder in the form of the flow pattern.

Advantages : Easiest method to setup and apply. Provides lasting flow pattern on the model for photos when the wind is off. Clearly shows flow pattern; shows flow separation well.

Old Hillbillies have been known to know the aerodynamic characteristics of their vehicals , from the airflow patterns from the dirt roads in the damp leaveing trails & traces on the bodywork .

Aiflow peculiarities at limits of things .

Site ( Its on winglets , in fact . ) http://fluidsengineering.asmedigitalcollection.asme.org/article.aspx?articleid=1438747&journalid=122

Drivle on Downwash . http://www.aerospaceweb.org/question/conspiracy/q0274.shtml

long & short of it ; dusting the rear fuse with say Blue Builders stringline Chalk Powder , will let you see the inviable tracks . If it sticks a bit .

Thanks for putting the picture on . Even if its not a pusher .

Disadvantages : Cannot vary model position during flow visualization. Model must be a dark color, preferably flat black, for contrasting the powder against the model surface. Pressure taps must be protected to prevent clogging.

Peter Germann · « **Reply #16 on:** April 15, 2013, 04:47:58 AM »

Quote from: Peter Germann on April 14, 2013, 03:35:44 AM

At this point in in time, I am about to do flight tests with an 1/8 x 1 in balsa strip taped to the front bottom side of the stab, kind of "simulating" a smaller AoA (approx. 0° as per the Robart Model Incidence Meter).

Here is what I, perhaps naive, flew yesterday. No effect whatsoever. Seems I have to cut into the airplane to get something like 0.25° negative (LE down) stab AoA...

Pusher: I've seen the pusher in your photograph in a Stockholm, Sweden, museum perhaps 25 years ago. Staff there said it was not a really successful airplane. Which is why mine is not a real pusher.

Valentin Apostolov · « **Reply #17 on:** April 15, 2013, 12:22:34 PM »

It is as we know from the books and and other places the PUSHER prop moments throw the nose out of the circle
and upwards. So no need to put the engine with AoA as youdid. I shall start the trimming of the model from this point. Set it at 0/0 , fly and make decisions.Also shaLL ELIMINATE the 'rabe'. May be you will find that the+ AoA
is too much. If so make it less / Katz Minato/ or eliminate it also.. And now the time to play with the stabil. came.

This shall be my way of trimming the birds,

Valentin Apostolov

Steve Helmick · « **Reply #18 on:** April 16, 2013, 06:50:43 PM »

I would urge a resolution to refer to propellers as LH and RH pitch, not "tractor" and "pusher". Typically, they are all in a tractor configuration. Some may want to refer to them as "American" vs. "Euro" (reference to Mustangs vs. Spitfires in engine rotation).

Steve

Igor Burger · « **Reply #19 on:** April 16, 2013, 11:48:39 PM »

Quote from: Peter Germann on April 15, 2013, 04:47:58 AM

Here is what I, perhaps naive, flew yesterday. No effect whatsoever. Seems I have to cut into the airplane to get something like 0.25° negative (LE down) stab AoA...

Pusher: I've seen the pusher in your photograph in a Stockholm, Sweden, museum perhaps 25 years ago. Staff there said it was not a really successful airplane. Which is why mine is not a real pusher.

Peter I do not thing that this modiffication will do anything. If you modify arfoil by lowering its LE, you will do something like negative AoA, that is true, but you will also make little chamber and it will make little extra lift, so I expect that 0 lift AoA will not change too much. May be not at all :- )))

Peter Germann · « **Reply #20 on:** April 17, 2013, 05:03:18 AM »

Quote from: Igor Burger on April 16, 2013, 11:48:39 PM

Peter I do not thing that this modiffication will do anything. If you modify arfoil by lowering its LE, you will do something like negative AoA, that is true, but you will also make little chamber and it will make little extra lift, so I expect that 0 lift AoA will not change too much. May be not at all :- )))

Confirmed, Igor. I did a bit of test flying yesterday with no positive result whatsoever. Removing the stab modification and cranking in substantial (6 mm or 1/4" at the LE) elevator up trim (with flaps at zero) did not help either. Adding 45 Gr. (1.6 oz) to the nose brought the C.G. to 205 mm (8 in) from hingeline (approx.12.5 % MAC !) with no improvement as far as level/inverted flight quality is concerned. The airplane still flies inaccurate, does not track well, shows no "groove" in level and inverted, and definitely lacks "point and shoot" quality.

Next I will remove the stab and reinstall it with 1° down AoA. Also, I will replace the current elevators (equally thick as the stab TE and with very sharp TE) by a pair of Max Bee style elevators (significantly thinner than stab TE with rounded trailing edge)

Peter

Igor Burger · « **Reply #21 on:** April 17, 2013, 05:09:40 AM »

may be you can first try classic configuration with tractor prop, motor straight or little down offset and retrim whole plane ... it will be easier then cut whole plane

if this does not help, then probably elevator will be really the problem

the yawing left on start can be easily cured with rudder right offset and lines moved back appropriately

Peter Germann · « **Reply #22 on:** April 17, 2013, 08:44:56 AM »

Quote from: Igor Burger on April 17, 2013, 05:09:40 AM

...easier then cut whole plane

Well, I guess you are right, Igor. I have now replaced the Rabe rudder function by an adjustable one setting the rudder to approx. 5° right and reversed motor direction to forward. Motor is still at 1° up as changing this to 1° down is a bit tricky

Testing will have to wait until I'll be back from the upcoming CIAM Plenary Meeting taking place April 18-21.

rgds. Peter

Doug Moon · « **Reply #23 on:** April 17, 2013, 12:45:47 PM »

Quote from: Peter Germann on April 17, 2013, 08:44:56 AM

... Motor is still at 1° up as changing this to 1° down is a bit tricky ...

rgds. Peter

You have to get that "UP" out of the motor offset. Get it level or a little down but NO up. It wont track with that in the configuration.

Not sure about you have mounted your motor but maybe a washer behind the motor at the top bolts between the motor and the mounting plate would adjust the angle some??

Peter Germann · « **Reply #24 on:** April 18, 2013, 06:31:00 AM »

Quote from: Doug Moon on April 17, 2013, 12:45:47 PM

You have to get that "UP" out of the motor offset. Get it level or a little down but NO up. It wont track with that in the configuration.

Thank you, Doug. The motor is now adjusted 1 degree down. Tractor prop trim and test to be flown when I will be back from FAI/CIAM Plenary Meeting next week.
rgds, Peter

Doug Moon · « **Reply #25 on:** April 18, 2013, 01:45:10 PM »

Quote from: Peter Germann on April 18, 2013, 06:31:00 AM

Thank you, Doug. The motor is now adjusted 1 degree down. Tractor prop trim and test to be flown when I will be back from FAI/CIAM Plenary Meeting next week.
rgds, Peter

Cant wait to hear how it goes!

Yves Fernandez · « **Reply #26 on:** April 19, 2013, 12:25:30 AM »

Quote from: Robert Storick on April 14, 2013, 11:30:31 AM

Peter this is a beautiful aeroplane.

Nice model Peter

Peter Germann · « **Reply #27 on:** April 29, 2013, 04:26:34 AM »

Quote from: Doug Moon on April 18, 2013, 01:45:10 PM

Cant wait to hear how it goes!

Here what I've done so far:
Switched to tractor APC 13 x 4 E, repitched plus 1 in at station No. 7 (9'340 RPM / 5.3 sec)
Motor thrust axis 1° down
Left unchanged stab AoA +1° (LE up)
Set C.G. at: 13.5% MAC
Added turbulators on stab; 0.4 x 3 mm (15/1000 x1/8) tape, 5/16 forward of hingeline, top & bottom sides.

Results are:
Sensitivity: high
Accuracy in manoeuvre: sufficient
Corner:tight, exits flat
Rounds: might need a bit of smoothing
Tracking in level flight: barely usable
Tracking in inverted flight: poor

As the elevators LE are of the same thickness as the stab TE, I will next replace the sharp TE elevators by significantly thinner flat plates with rounded trailing edges. This will take a bit of time and I will report findings when done.

Meanwhile, as our contest season has started yesterday, I will use last year's Max Bee (one) to compete.

rgds, Peter

Igor Burger · « **Reply #28 on:** April 29, 2013, 04:39:04 AM »

May be there is something you can test without too much effort, Rabe rudder can also cause or solve hunting, may be you can try to switch it off and try, if something changes. If not (if pusher/tractor does not make any change), then it is definitelly elevator.

RandySmith · « **Reply #29 on:** April 29, 2013, 10:16:37 PM »

Quote from: Peter Germann on April 29, 2013, 04:26:34 AM

Here what I've done so far:
Switched to tractor APC 13 x 4 E, repitched plus 1 in at station No. 7 (9'340 RPM / 5.3 sec)
Motor thrust axis 1° down
Left unchanged stab AoA +1° (LE up)
Set C.G. at: 13.5% MAC
Added turbulators on stab; 0.4 x 3 mm (15/1000 x1/8) tape, 5/16 forward of hingeline, top & bottom sides.

Results are:
Sensitivity: high
Accuracy in manoeuvre: sufficient
Corner:tight, exits flat
Rounds: might need a bit of smoothing
Tracking in level flight: barely usable
Tracking in inverted flight: poor

As the elevators LE are of the same thickness as the stab TE, I will next replace the sharp TE elevators by significantly thinner flat plates with rounded trailing edges. This will take a bit of time and I will report findings when done.

Meanwhile, as our contest season has started yesterday, I will use last year's Max Bee (one) to compete.

rgds, Peter

Peter

Is the stab LE sharp or blunt?

Randy

Peter Germann · « **Reply #30 on:** April 30, 2013, 03:37:20 AM »

Quote from: RandySmith on April 29, 2013, 10:16:37 PM

Peter
Is the stab LE sharp or blunt?
Randy

Kind of sharp, i.e. a radius of approx. 1/8"
Peter

Peter Germann · « **Reply #31 on:** April 30, 2013, 03:46:03 AM »

Quote from: Igor Burger on April 29, 2013, 04:39:04 AM

May be there is something you can test without too much effort, Rabe rudder can also cause or solve hunting, may be you can try to switch it off and try, if something changes. If not (if pusher/tractor does not make any change), then it is definitelly elevator.

When I switched to tractor the (pusher) rabe rudder (coupled to elevator up) was switched off and replaced by an adjustable rudder now being set to approx. 5° out.
Re-activating the Rabe function for tractor (coupled to elevator down) requires a bit of surgery, too. What I plan to do is installing a pair of 7 mm (1/4) flat plate elevators and make the Rabe rudder being usable for both types of props.
Peter

RandySmith · « **Reply #32 on:** April 30, 2013, 08:01:00 PM »

Quote from: Peter Germann on April 30, 2013, 03:37:20 AM

Kind of sharp, i.e. a radius of approx. 1/8"
Peter

I was curious, I have found the stab LE being sharp makes the plane groove better.

Randy

Doug Moon · « **Reply #33 on:** May 02, 2013, 01:10:39 PM »

Quote from: RandySmith on April 30, 2013, 08:01:00 PM

I was curious, I have found the stab LE being sharp makes the plane groove better.

Randy

I have found this too.... interesting....

I was thinking, just a thought before you go and make new elevators and all that work, could you or have you tried adjusting the length of the elevator pushrod Since you went to the tractor prop? Shorter or longer? Typically I try to go shorter first and see if it worsens or helps the situation.

Peter Germann · « **Reply #34 on:** May 03, 2013, 05:25:01 AM »

Quote from: Doug Moon on May 02, 2013, 01:10:39 PM

I was thinking, just a thought before you go and make new elevators and all that work, could you or have you tried adjusting the length of the elevator pushrod Since you went to the tractor prop? Shorter or longer? Typically I try to go shorter first and see if it worsens or helps the situation.

I've cranked in as much as 1/4" elevator up (at the TE, with flaps neutral) w/o noticable influence on tracking... Contests coming up (next: http://www.mgbreitenbach.ch/) keep me from working at the new airplane now, so its back to last years pretty stright forward Max Bee.
rgds, Peter

Doug Moon · « **Reply #35 on:** May 03, 2013, 01:38:06 PM »

Quote from: Peter Germann on May 03, 2013, 05:25:01 AM

I've cranked in as much as 1/4" elevator up (at the TE, with flaps neutral) w/o noticable influence on tracking... Contests coming up (next: http://www.mgbreitenbach.ch/) keep me from working at the new airplane now, so its back to last years pretty stright forward Max Bee.
rgds, Peter

Right, that would make sense. With the elevator up and flap neutral when you go to fly the plane you will need to level the elevator to get it to fly level. This would then give you a up flap, or negative AoA, and the plane would want to sink, and probably pretty badly as well.

With down elevator at flap neutral when you level elevator in flight you get a positive AoA and the plane will fly level.

At least this is what I have encountered over the years.

RandySmith · « **Reply #36 on:** May 03, 2013, 01:54:06 PM »

Quote from: Doug Moon on May 03, 2013, 01:38:06 PM

Right, that would make sense. With the elevator up and flap neutral when you go to fly the plane you will need to level the elevator to get it to fly level. This would then give you a up flap, or negative AoA, and the plane would want to sink, and probably pretty badly as well.

With down elevator at flap neutral when you level elevator in flight you get a positive AoA and the plane will fly level.

At least this is what I have encountered over the years.

Hi Peter

Doug is correct with the standard rotation prop try to set the elevators at about 1/32 inch down, when flaps are dead level. Have you tried it that way yet? and not only will it fly more level, it tracks better

Randy

Carl Cisneros · « **Reply #37 on:** November 01, 2014, 05:27:49 PM »

Peter;

Your Orange Stunt ship kind of reminds me of my old Loaded Dice Pattern ship I had when we were stationed in England.

Great looking plane you have there.

Peter Germann · « **Reply #38 on:** November 02, 2014, 03:42:26 AM »

Quote from: RandySmith on May 03, 2013, 01:54:06 PM

Hi Peter
Doug is correct with the standard rotation prop try to set the elevators at about 1/32 inch down, when flaps are dead level. Have you tried it that way yet? and not only will it fly more level, it tracks better
Randy

Two (with 66 oz kind of heavy) airplanes later, and still flying pushers, I am now back to 0° incidence for both, motor and stab. As Randy suggests, elevator slightly (1°) out of neutral seems to help.
Peter G.