hyflyer9

Hello all I am getting a yo yo effect just after take off could it be me pulling to much on the stick or could it be my engine a little under powered . I am flying a ESM P47D 71" and power is a rcgf 26cc Gas with a 16x8 xoar prop I always try to get as much role out on the ground before take off .
Thank you.
hyflyer9.

huck1199

Is it balanced properly?

hyflyer9

Yes I got the Balance set foe a little nose heavy. Once the plane gains a little speed when flying it seems to be ok but I have noticed that it is very sensitive on the elevator
hyflyer9

MinnFlyer

My Feedback: (4)

If it's nose heavy and sensitive to the elevator, you have too much elevator throw

da Rock

Also, if you get them too nose heavy, the elevator AND the stab can be overloaded. They are responsible for pitch stability and only have so much to give. Moving the CG forward loads the tail. It's a negative load, but the tail has to keep the nose up just like it'd have to keep it down if you moved the CG aft. The farther forward, the more load, and you can get too much load. What happens then is like Dutch roll only it's in pitch. Dutch roll is an oscillation in yaw when the fin/rudder isn't large enough. The only difference (other than in the direction of "yo-yo") is that the rudder problem isn't increased by the CG location.

Most people don't realize that the CG can be too far forward. And fewer still understand how moving it forward makes the tail less effective.

The recommended CG and recommended elevator throws go together. Move CG forward and you might need more throw. Move it back from recommended and you very probably will need less.

Lnewqban

Could you explain that a little more for me?
Is that yo-yo induced by you or it happens at a fixed stick deflection?
Do you believe that the model develops insufficient speed for a scale take off?

hyflyer9

It seems to me that it may not have enough power as the engine is a 26cc gas . But I have noticed once I relax the elevator stick a little it even's out .
But then as I am flying along and pull on the elevator it is very sensitive I am using the recommended throw on all surface's and also minus 12% EXP on ail;elev;rud; As this is my first gasser I am not sure what is going on. The power band is very different from a nitro engine for sure .
hyflyer9

Glacier Girl

My Feedback: (4)

Something from your last post. You said NEGATIVE 12% expo. You are using a Futaba tx right? If not you are setting the expo the wrong way, and it is making it more sensitive.

JR/Spektrum go positive to be less sensitive, Futaba goes negative.

hyflyer9

No my RX and TX are all Hitec 2.4ghz

Lnewqban

Something seems to be contradictory in this case.

1) If the model is a little nose heavy (manual specifies 3-1/8" behind LE at center line of the wing), nothing like that should happen.

2) If the model is way nose heavy, and is still slow after take-off, you may be forcing the take-off with low speed and big AOA.
When elevator is full up, with big deflection to rise the nose,
a) The tail could stall, inducing a nose down pitch that reduces AOA and downwash, re-attaching the airflow over the elevator, and then the process repeats.
b) May be the wing is starting a stall and falling forward, just to resume flight while the speed increases, and then the process repeats.
Sort of what happens to a chuck glider that has too much elevator up or aft CG.
The problem should improve while the speed increases, since both AOA's don't need to be high.

3) If the model is neutral or close to be tail heavy, and is still slow after take-off, it may become elevator sensitive or even unstable in pitch right after take-off,.............but it should continue behaving like that or worse while the speed increases.

I agree with da Rock and MinnFlyer, in the belief that #2 above is the case here.
However, for that to be truth, the specified CG must be incorrect.

hyflyer9

my manual say's CG is 136mm or 5 5/16 from leading edge at center of the wing. this yo yo effect happens just after take off but as the plane gains speed it even's out but still the elevator is very sensitive. I should say here that my P47 is the ESM Frank Tiano Signature series the one seen on the link provided
[link]http://www.troybuiltmodels.com/items/ESMP47-71-C.html[/link]
hyflyer9.

jester_s1

It sounds like you have a simple elevator is too sensitive issue. You are getting too much travel on takeoff and having to compensate, thus dropping the nose. It's too sensitive in flight too, right? Either lighten up on the throw or add more expo to soften the center. I generally find that the manufacturer's recommendation on throws is too much for my tastes.

da Rock

You might also try setting up and tuning elevator low rates.

Rudolph Hart

Or you could have two beers and just go fly

scale only 4 me

My Feedback: (158)

I see tha't what the manual says, but That CG doesn't sound right to me,
I have the Ziroli 70" P47 and the CG is at 4",, 5 5/16 sound very aft to me

good luck

VIRGINIA MODEL BUILDERS

My Feedback: (159)

Has anyone finally established the proper CG for the ESM P47?