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My ft old fogey flies very unstable!! Please help me!!

gDuke

New member
#1
I have built many planes, over of 25 builds and many builds with my own plans!

The problem is that my new "old fogey" is fliyng with a very unstable way! It seems like an unbalanced or tail heavy plane!

I can't imagine that the famous old fogey (my own) is the only that wont fly!!!

Here is the video link on youtube about how it flies:
https://youtu.be/2rwuD1NHQjk

I folow the recomented build without any modifications. The CG it's tested and it is perfect balanced!!

My power setup is:
1. motor: emaxx CF2812 1400KV
2. 18A ESC
3. 8X4 or 7X4 propeller
4. 1300 mAh 3S lipo battery
5 servos 9gr X 2
6. 3ch receiver

I am desperet with my build! Please help me if you can!

gDuke
 

Attachments

Gazoo

Active member
#2
I know you said that the CG was right on but it sure looks tail heavy to me.

Have you tried to glide it with no power? If the CG is right on, it should glide with some trim adjustments.
 

Bricks

Well-known member
#3
I know you said that the CG was right on but it sure looks tail heavy to me.

Have you tried to glide it with no power? If the CG is right on, it should glide with some trim adjustments.
Have to agree looks tail heavy I would rebalance at least a 1 inch farther back and go from there.
 

Winglet

Active member
#4
Hi Gduke,

I have literally built and flown over 100 successful RC models of all types and sizes. I built the Old Fogey several years ago and I have to admit, it was a failure . Yep, it flew but it flew terrible. Nothing I did ever made if fly decently. Others have extensively modified it to the point were it really isn't an Old Fogey anymore and made it fly, but I think the modifications are extensive. Better to pull your radio and build something else. Sorry.
 
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#5
Balance it more nose heavy at least 1 inch in front of the wing split, she is tail heavy. try it in lighter winds also. turn down the rudder rate and go easy on the throttle. might try some down on the elevator too.
 

gDuke

New member
#6
I know you said that the CG was right on but it sure looks tail heavy to me.

Have you tried to glide it with no power? If the CG is right on, it should glide with some trim adjustments.
I can't glide it with no power because i can't gain altitude! I'll put the battery some cm to front and i'll give it a try!
 
#7
That video is the perfect example of an aerodynamic principle called Dutch Roll. Dutch Roll is when the dihedral in a ployhedral wing is either too great or unbalanced. This causes the plane to rock back and forth violently as the polyhedral overcompensates for itself. If you built the plane off of plans there wasn't a gauge included to help set up dihedral, which can make it difficult. Try using a ruler to make sure both sides are around the 4 inch mark, as shown in Josh's build video. I also have heard from a lot of people about the Fogey's tendencies to be tail heavy. Personally mine has never had a CG issue in a year of flying, and it's probably because I used a large langing gear, the same used on FT's bigger single-engine planes like the Sportster.

So, to sum it up, check that both sides of the wing are about 4 inches off the table when the wing is flat, and make sure they are even as possible. Also, try adding a heavier gauge of langing gear with bigger wheels and it will help the balance problem.

Cheers,
Dark
 
#8
Like many others have said, I fly with the c/g well forward of what's indicated on the plans. Because I couldn't get it flying right with the recommended 800 mAh battery, I used a 1700 mAh battery. It flies VERY nicely with that. To demonstrate, a few videos of the Old Fogey in action (I built two, the first one I smashed as I was re-learning to fly).

Both aircraft are stock. The only flaw I've seen is the tendency to "Dutch roll." But going easy on the rudder can help reduce that problem -- it does teach you to avoid over-controlling... ;)

First, the Old Fogey, Mk 1

And the Fogey, Mk 2

On board video from the Mk 2
 

Montiey

Master Tinkerer
#9
Perhaps you can cut the winglets off and adjust the poly angle? The Roll Factor and the obvious tail heavy characteristics can only make each other worse.
 

Tench745

Active member
#10
It 'looks' tail heavy, but I don't think it is.

I would try just tossing it with the radio on but don't give it any throttle and see if it glides to the ground or jumps nose up and stalls like it kept doing under power. If it pitches up violently with the motor off, then it's tail heavy. If it will glide with the power off, try it a few more times but this time give it somewhere between 1/4 and 1/2 throttle.

I'm assuming in the video you were flying at full throttle. It looks to me like you have too much power causing too much lift and the elevator can't overcome that. Glide tests as mentioned above will tell you whether it's a cg issue or power.
If it only pitches up under power, you could try angling the motor down slightly to pull the nose down as you add power (called downthrust), or make a larger horizontal stabilizer and elevator, or increase your throws on the elevator.

I think most of the instability in roll/yaw are from the wing being stalled at that high angle of attack. If you can get the pitch issues fixed, I think roll and yaw will be much more manageable for you.
 

gDuke

New member
#11
CG change on ft old fogey!!

First I want to thank all the members of the forum for the information they gave me!

Two days ago I re-flew the plane with the least possible modifications! I just put the battery even closer to the motor!

Here is the result: (The action camera ...looks to the god, so forgive me for my shots!!)


2017602120358.jpg

The plane flies more gently than before!

Trotlle about 50%, rudder 60%, elevator 60% and battery 2" from powerpod for the first flight
and Trotlle about 65%, rudder 100%, elevator 100% and battery 1" from powerpod for the second flight!

In the last seconds of the second flight the battery came out of the power pod!!
 
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#13
Try without landing gear

I'm really new at this, and had the exact same problem. I took off the landing gear (not exactly voluntarily) and was able to fly it well. After reading comments here, I'll try fiddling the CG. --Thanks to all for this resource.
 

rockyboy

Skill Collector
Mentor
#15
First, great looking Fogey! :)

One other thing that could help a little more - from looking at your photos above is seems the horizontal stabilizer isn't all the way parallel to the wing. If that horizontal stab is tilted it's going to be fighting with the dihedral in the wing. As the air spills out of one side of the stabilizer it rolls the plane, and then the dihedral in the wing tries to roll the plane back, and so on. This effect is much worse on a tail heavy plane and throwing the weight forward will help reduce the effect, but if indeed those surfaces aren't level that's a place you can adjust to get a better flight out of it.