Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

cermark F-16 pulling hard right. Help!!!

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Old 06-10-2007, 05:49 PM
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The Flying Shreder
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Default cermark F-16 pulling hard right. Help!!!

I maidened my F-16 today. I had it up and down twice. I never really flew past 50% power from the Jett 90 lx and was running it a bit rich but it flew well at cruising speed. C.G. is at about 7.25 and it didnt seem to need any elevator trim. Landings were just a little bit hot but were nose up. However takeoffs were scary. Ive got about 300 ft of runway and Id say I used about 250ft of it and she wants to pull hard right on me. I took it up for a 3rd flight before the wind started kicken up this morning and when she got off the ground it rolled hard right on me and I backed off the throttle a little bit...well that was a mistake. Into the ground we went and busted the nose off her. I ve just about got it fixed already. My question is what could be pulling it so hard to the right. I havent flown it enough yet but it seemed like when I got on the power just a little bit in the air she wanted to roll right on me to. Motor looked dead center when I mounted it. I never checked to see if the wings where balanced on it. Has anybody had to add a little weight to the left wing to get the wings balanced. I just thought since the motor hangs off to the right that might make it heavier on the right side. I ve got my elevator set at about 1 inch maybe I should jack it up a little bit to see if it'll get up faster. Anybody have any problems like this? Suggestions?
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Old 06-10-2007, 06:32 PM
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Flyboy Dave
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Default RE: cermark F-16 pulling hard right. Help!!!

You should balance the plane lateraly. You should have to add weight to the left wingtip
to offset the weight of the engine hanging off the right side of the plane. You will probably
have to add about 2 1/2 ounces lead to the left wingtip.

FBD.
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Old 06-10-2007, 06:41 PM
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Default RE: cermark F-16 pulling hard right. Help!!!

Thanks for the speedy reply. This is only the 3rd plane Ive put together. So Im kinda learnin as I go here
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Old 06-10-2007, 06:45 PM
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Flyboy Dave
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Default RE: cermark F-16 pulling hard right. Help!!!

You might have a tiny warp in the wings which is making matters worse. Even though lateral
balance is important, it usually isn't critical like you described. []

See if your ailerons are centered properly as well. You might have a tiny bit of "right aileron"
into the trim.
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Old 06-10-2007, 07:01 PM
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Default RE: cermark F-16 pulling hard right. Help!!!

Thanks again. I know they pull a little to the right on the ground but this was ridiculous. I had full left rudder on takeoffs and it was still aweful squirly. Come to think of it I had quite a bit of left contols on landing to get her in straight but it wasnt nearly as bad as taking off at full power. She really wants to pull right when the motors turning up. I imagine I ll have to really balance it out now since the crash will throw it off a bit.
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Old 06-10-2007, 07:40 PM
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Default RE: cermark F-16 pulling hard right. Help!!!

Normally the torque will pull the plane to the left....

....so, I think something is really out of whack. [X(]
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Old 06-10-2007, 07:54 PM
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Mike Connor
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Default RE: cermark F-16 pulling hard right. Help!!!

Lateral balance is not causing your problem. I would start twisting things to see what you forgot to glue.
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Old 06-10-2007, 08:03 PM
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Default RE: cermark F-16 pulling hard right. Help!!!

Not much glueing on this plane. wings stabs are all held on with aluminum tubes. Even with a motor side mounted right you dont think thats going to throw a bunch of weight to that side. You other guys flying this model how does it take off for you. I can tell it will fly great once I figure this out
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Old 06-10-2007, 08:38 PM
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Default RE: cermark F-16 pulling hard right. Help!!!

What does it track like at low speed down the runway? Make sure you laterally balance the plane and check that she tracks straight. Other than that, I would seriously check for a warped wing as well. What size prop are you using?

Spar
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Old 06-10-2007, 08:42 PM
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Default RE: cermark F-16 pulling hard right. Help!!!

i would check your elevator set up. sounds like your right stab is giving more input than your left. Make sure your linkage is the same length and you have your atv set up the same. run your elevators up and down slow to make sure that they track the same. If that is good, i would try doing it with the engine running to see if you are getting any glithches from the vibration.

ken
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Old 06-10-2007, 08:57 PM
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Default RE: cermark F-16 pulling hard right. Help!!!

Ditto ^
It really sounds like a elevator setup issue to me. Two servo elevator setup not in sync.
Id check for wing warp also but im doubting thats the culprit.
Cheers.
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Old 06-10-2007, 09:12 PM
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Default RE: cermark F-16 pulling hard right. Help!!!

It tracks to the right at low speed down the runway. Im using the 11x8 on the Jett. Thats the prop for this motor I guess. The elevator linkage is real close and seemed to travel at the same rate. I checked stuff over alot before I flew it. It did kinda freak me out though after it went in nose first I came home and started fixing it I turned it on and the right elevator had way more input than the left. I cant understand why. I checked and rechecked the control surfaces and the elevators traveled at the same rate before flights and I wouldnt think a crash would knock a servo off track like that. I took the servo wheel off the right elevator and moved it to get it to travel on track with the left now.
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Old 06-10-2007, 09:17 PM
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Default RE: cermark F-16 pulling hard right. Help!!!

What is atv an abrreviation for.
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Old 06-10-2007, 10:11 PM
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Default RE: cermark F-16 pulling hard right. Help!!!

....adjustable travel volume....how far the servos travel.
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Old 06-11-2007, 05:14 AM
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Default RE: cermark F-16 pulling hard right. Help!!!

One other suggestion I can think of if you havn't already.........
A lot of guys notices the engine mount was the wrong way around on these birds and had to return or fix the problem themselves.
I dont think this could be it though as Im sure you would notice.
I havnt got my bird yet, so I dont know what it looks like.

Aslo , double check the teeth on that right elevator servo, correct arm??? (iv done that....ie arm is same make as the servo?) and teeth arent worn, may have slipped a few teeth.

Let me know what the final problem was. Very intersted.

Thanks for the thread

R.
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Old 06-11-2007, 09:15 AM
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Default RE: cermark F-16 pulling hard right. Help!!!


ORIGINAL: The Flying Shreder

Thanks again. I know they pull a little to the right on the ground but this was ridiculous. I had full left rudder on takeoffs and it was still aweful squirly. Come to think of it I had quite a bit of left contols on landing to get her in straight but it wasnt nearly as bad as taking off at full power. She really wants to pull right when the motors turning up. I imagine I ll have to really balance it out now since the crash will throw it off a bit.
Make absolutely sure the elevator/stabs are properly matched/trimmed, and that they have exactly the same amount of throw.
If the incicence on one stab is off, the plane will roll. The stabs are more effective in roll at low speeds than the ailerons are.
(since you noted that takeoff is an issue, low airspeed and up elevator control is involved... just as with landing apparoch.... this is something I would most definately check)

Also.... this may sound semi-insulting.... but Ive done it myself.....
make sure the control throws are correct direction on rudder and nose stearing.

Normally a plane with pull to the left on takeoff requiring a bit of right rudder (due to engine torque, or P-factor).
If it is rolling right, that has less to do with engine power and is more likely aerodynamic .... definately check the wings for a warp, and check the latteral balance as was noted.

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Old 06-11-2007, 10:45 AM
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Default RE: cermark F-16 pulling hard right. Help!!!

ORIGINAL: bob27s

Also.... this may sound semi-insulting.... but Ive done it myself.....
make sure the control throws are correct direction on rudder and nose stearing.
This is actually very good advice since the instructions I have say to simply connect the rudder and wheel steer servos with a standard y-harness. Problem is that wont work because the rudder and steer servos will be working opposite because of servo arrangement.
Two solutions are a servo reversing y-harnness or (in my case) I put the steer servo on ch 7 and mixed it with ch 4.
Cheers.
James
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Old 06-11-2007, 02:37 PM
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Default RE: cermark F-16 pulling hard right. Help!!!

After checking stab/wings incidence, lateral balance, elevator servos ATV to sync, the final factor to consider is wind direction. If you have a cross wind, the plane will want to turn into the wind. If wind is blowing at your back, you want to take off going from left to right. If wind is in your face, take off from right to left. Idea here is to use engine torque to counteract wind pulling effect.
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Old 06-11-2007, 04:55 PM
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Default RE: cermark F-16 pulling hard right. Help!!!

Also.... this may sound semi-insulting.... but Ive done it myself.....
make sure the control throws are correct direction on rudder and nose stearing.

I see one problem already, rudder and nose in wrong direction. I need a servo reverser. I know I should of caught that myself but the book said connect to y-harness. Man I checked this thing over and over, I sure feel stupid now[&:]
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Old 06-11-2007, 05:05 PM
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Default RE: cermark F-16 pulling hard right. Help!!!

Tape two balsa sticks to elevators coming back and hanging off the rear behind the rudder. both sticks slanted towards each other so that the ends almost meet behind rudder . Then operate elevators while watching the ends, too see if the elevators track together. This helps set up properly. they must track together. If you have seperate sub trims settings and atv,s zero them out and do mechancal adjustments first. Hope this helps. Wish I knew how to do a diagram, just not computer savy yet.
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Old 06-11-2007, 06:01 PM
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Default RE: cermark F-16 pulling hard right. Help!!!

....you should be able to move the linkage on the nosewheel over to the other side of the
servo, and change the direction of movement.

FBD.
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Old 06-11-2007, 07:58 PM
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Default RE: cermark F-16 pulling hard right. Help!!!

I had the same problem with the nose wheel needing a reverseing Y harness and used the lead with the adjustable center on the nose wheel to be able to center it later as needed. However later I changed the hitect Rudder servo for a futaba servo and low a behold I didn,t need the reverser any more All the other servos were Futaba. Maybe you mixed and matched servos like I did at first.
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Old 06-11-2007, 08:23 PM
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Default RE: cermark F-16 pulling hard right. Help!!!

I imagine thats most of my problem. I cant believe that I missed that. Im getting pretty good at flying it's just setting the plane up right thats been giving me a hard time. Elevators are tracking right on. Im just about ready to get back in the air. Im going to rebalance it and then I think we should be alright.[8D]
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Old 06-11-2007, 08:28 PM
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Default RE: cermark F-16 pulling hard right. Help!!!

I put hi tech 475 on flight surfaces 85 on rudder. Then I had some jr's I had laying around on throttle, stearing and retract.
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Old 06-11-2007, 11:31 PM
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Default RE: cermark F-16 pulling hard right. Help!!!

"""Also.... this may sound semi-insulting.... but Ive done it myself.....
make sure the control throws are correct direction on rudder and nose stearing."""----------------------------------------------------------------- I ran into this problem also,, i noticed it right before the maiden flight,, boy what a let down,, i was really exited for a maiden,,,, i can't imagine how you flew that bird like that,, it must have been scarry[X(]
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