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Old Feb 04, 2013, 11:20 AM
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mike early's Avatar
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I think downthrust is more important that right-thrust. Does it climb with increased throttle? Does everyone dial in throttle-elevator mix in an attempt to rectify the issue? How much downthrust can I add and still get an acceptable cowl-to-spinner interface?

Dang.

Alas.
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Old Feb 04, 2013, 11:32 AM
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danpos's Avatar
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Quote:
Originally Posted by mike early View Post
I think downthrust is more important that right-thrust. Does it climb with increased throttle? Does everyone dial in throttle-elevator mix in an attempt to rectify the issue? How much downthrust can I add and still get an acceptable cowl-to-spinner interface?

Dang.

Alas.
I left mine as is without any throttle-elevator mixes.
As long as it's balanced right it doesn't climb bad at all.
There is a very slight climb at full throttle, but no more climb than any of my other planes.
It's really a non issue.
The cowl and spinner align good as is too.
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Old Feb 04, 2013, 11:40 AM
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Ok. Thanks. I will see how it goes.
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Old Feb 04, 2013, 11:50 AM
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Hobby King Oleos

Anyone use these with the Eflite 85 degree retracts?

http://www.hobbyking.com/hobbyking/s...dProduct=23883
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Old Feb 04, 2013, 02:59 PM
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Pitch + Power

I'd like to add a word on some of the pitch and power concerns here. Assuming all balance issues are within specs, if an aircraft is trimmed for desired pitch performance, then any change in power will result in a change of pitch attitude or performance. Straight and level cruise would ideally require neutral trim @ that desired desired attitude. Any addition or reduction in power during that pitch attitude will change the performance requiring trim adjustment. To maintain a desired pitch attitude in trim, whether level, climbing or gliding the power needs to maintain a constant setting otherwise additional elevator change or trim is required.
I hope I didn't overstate the issue.... Pitch +/- Power = Performance

ce
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Old Feb 04, 2013, 03:52 PM
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Originally Posted by capteasy View Post
I'd like to add a word on some of the pitch and power concerns here. Assuming all balance issues are within specs, if an aircraft is trimmed for desired pitch performance, then any change in power will result in a change of pitch attitude or performance. Straight and level cruise would ideally require neutral trim @ that desired desired attitude. Any addition or reduction in power during that pitch attitude will change the performance requiring trim adjustment. To maintain a desired pitch attitude in trim, whether level, climbing or gliding the power needs to maintain a constant setting otherwise additional elevator change or trim is required.
I hope I didn't overstate the issue.... Pitch +/- Power = Performance

ce
It cannot be overstated as far as I am concerned. It's my pet peeve. I buy Ernst thrust plates and adjust the thrust line till I get it perfect. I like WOT low LOW passes and I also like very slow low passes. Constant accurate trim is important to me. Why the hell does anyone put UPthrust in a plane?
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Old Feb 04, 2013, 03:58 PM
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Maybe I can work the cowl so it angles down a bit...
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Old Feb 04, 2013, 04:48 PM
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Quote:
Originally Posted by mike early View Post
Why the hell does anyone put UPthrust in a plane?
Full scale BF-109E was the only warbird I know that had up-thrust. many had none... few had down. but NONE, NOT ONE had right thrust!
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Old Feb 04, 2013, 05:37 PM
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I am only familiar with toy planes, and the apparent universal importance of down thrust...
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Old Feb 04, 2013, 07:57 PM
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Quote:
Originally Posted by mike early View Post
I am only familiar with toy planes, and the apparent universal importance of down thrust...
I have some factory drawings that show down thrust on the full scale P51.

full scale planes are supposed to climb at full throttle and we would trim slightly at cruise and expect the plane to descend when throttle was reduced below cruise. The only way to get level flight at multiple throttle settings would be to program the elevator to track with throttle or manually trim every time you change throttle settings.

To make a full speed low pass you either need to manually trim or feed some down into the elevator as you go.

Dave
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Old Feb 04, 2013, 08:15 PM
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I'm not sure about all full scale US single engine warbirds but most were probably built with vert stabs slightly offset left to help compensate for the left turning forces. Some models may use the same feature as well.
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Last edited by capteasy; Feb 04, 2013 at 08:27 PM.
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Old Feb 04, 2013, 08:47 PM
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Quote:
Originally Posted by capteasy View Post
I'm not sure about all full scale US single engine warbirds but most were probably built with vert stabs slightly offset left to help compensate for the left turning forces. Some models may use the same feature as well.
I believe the P51 manual specifies right rudder trim for the takeoff roll which is very similar to the model which requires quite a bit of rudder correction on takeoff roll.
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Old Feb 04, 2013, 08:50 PM
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Vertical stabilizers are usually off-set a bit on full scale, to my understanding.

The cowl on this particular toy plane make it too difficult to pursue any downthrust. So, I'll dial in some throttle-elevator mix and hope for the best. Biggest drawback on that is when I hammer the throttle during a low speed pass, it noses down when I am already as low as I can fly. So...I will try to remember to avoid that on this plane...
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Old Feb 04, 2013, 09:28 PM
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This is an interesting subject but the E-Flite designer said that the thrust line is supposed to be zero degrees with a couple degrees of right thrust.

The full scale P-51 manual does specify 5 degrees of right trim on the rudder for takeoff roll and that sounds right. 5 degrees is actually a lot but this is to help the pilot hold a straighter line without getting into a big ground loop situation while applying all that power.

Section VII -- Operating Instructions for the P-51

PRELIMINARY CHECK
Obtain flight clearance.
Check outside of airplane carefully. Remove pitot cover.
Check service of ship and status of it on Form 1A carefully.
Make sure chocks are in place.
ENTER COCKPIT
Adjust seat and rudders for height and length.
Check ignition switch OFF.
Set parking brake.
Check bomb and gun safety switches are OFF.
See that landing gear control handle is in the DOWN position. On the P-51D, there is NO ARENS control to prevent accidental raising of gear on the ground.
Unlock controls and check for freedom of movement. Control lock is located at the base and just forward of the stick. Pull the plunger on the left side of the lock to unlock controls.
Fasten safety belt and shoulder straps.
Set altimeter to correct barometric pressure.
Oil and coolant shutters to full OPEN position as soon as batter cart is plugged in.
Set trim tabs. Rudder 5° Right, Elevator 2° to 3° Nose UP (with 25 gallons or less in fuselage tank). Elevator 1° to 3° Nose DOWN (fuselage tank full). Aileron 0° for Take-Off.
Release hydraulic pressure with wing flaps and flap handle to UP position.
Close canopy


The fact that some of these planes have what appears to be a degree or so of upthrust is likely a result of tolerances. After all this is a hand built wood assembly and even with laser cutting one could not assume that the thrust line would be perfect on every plane. My estimate would be that holding a plus/minus 1 degree tolerance would be difficult. Shimming in 1 degree or so of down should not screw up the cowl fit much. I have two of these planes and I did adjust the thrust line slightly on one. Mine has some right thrust built in from the factory and it looks like the front face of the cowl is slightly canted to the right.

I wouldn't call this plane a toy though. I find mine to be quite intimidating at full throttle and commands a lot of respect. Overall it is a great airplane at a great price. However, I have always believed it should be flown with 2-3 degrees of aileron reflex. That is just my personal opinion though.
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Old Feb 04, 2013, 09:41 PM
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2-3 degrees of aileron reflex?
Spoilerons, so to speak? Have the ailerons up a couple of degrees on both sides at neutral?


Are most people living with the color mis-match between the hatch, flarings, and the fuesleage?
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