Trimming HELP!!!
 

Still stucked with trimming my glow Genesis. The plane still needs significant backpressure to fly inverted, but KE performance is horrendous. It pulls to the wheels with both left to right and right to left KE flight. Right rudder application needs 9% up elevator mix. Left rudder is at 18% and counting since it still pitches to the wheels significantly. If I move the CG back a little more to relieve backpressure on the elevator stick, wouldn't KE deteriorate even more (i.e. needing more up mix?) I guess I will end up at 25% up mix with left rudder as of now (and still not satisfied with inverted flight)

Do you guys have any idea where else to look? TIA

RE: Trimming HELP!!!
 

I think you need to setup the plane and measure the CG position. The jig up the plane and measure the stab and wing incidence. Then measure the thrust. If you that dissastisfied with the performance, attain these baseline measurements so we can help from there.
Thanks,
Jim W.

RE: Trimming HELP!!!
 

set the wings at 1/3 to 1/2 deg positive
{it`s probably set at zero from the factory }
then move the c/g forward till both knive edges require no mix or the left rudder requires very little
right now feels like its nose heavy But it`s fooling you it`s actually tail heavy or you have more pos. inc. than you need
I suspect it`s tail heavy the c/g seems to be about an inch off to me .
looking a the front of the airplane use the left side canopy base // the right side is not the same as the left ......
to get the zero setting as a ref.
I flew this airplane for a year and this is the best setup.
Being that far tail heavy makes the airplane very unstable when the wings are not loaded and it will pitch to the canopy in the downlines and to the belly with any rudder use
you will be suprised at how far back you can fly the tail weight on a pattern airplane and not be aware of it
it can get crazy! just check inc. and don`t be afraid to move the c/g a bunch
Bryan

RE: Trimming HELP!!!
 

Good comments Bryan, I was thinking tail Heavy too. Its nice to know that you and I were thinking the same.

Sometimes when we are trimming a model its a guessing game. I just flew a new model the other day and was thinking it was the same Cg as my other one. Turns out something was different and it was 28mm behind my other models CG. By the way the models are within 3g of each other total weight so I have no idea how this happened using basically the same bits and pieces. I guess the stabs are heavier on the 2nd model. So I now have the battery pack in a different location on the new one and the Cg's are the same as the original model.

Aresti, listen to Bryan he knows what he is talking about.

Good Luck with it.

Troy Newman

RE: Trimming HELP!!!
 

Hi Guys

I'm just learning all this but I spend about 80% time setting up my plane and 20% flying it during the first six months. I was happy with the result until a more experienced pilot test flew it for me.....

I learnt from the start though to test the throws and measure the CG before even going to the field. I can't beleive you would actually fly a plane without knowing exactly where the CG is. And fingers under the wing is no way to test the CG either- hahahaha

I can say though that either my flying is improving or the work done on the plane has made it better or maybe both!!!! I have moved the recommended CG significantly rear from the manuals recommended - but I started from the manuals recommended CG. No guessing for me - it's just too bloody expensive!!!

80/20 - thats the recipe for success in pattern flying....

RE: Trimming HELP!!!
 

Yes a good CG tool is worth the time. It gives the base line to start the trimming process. 10 dollars spent on PVC pipe and fittings you can make a nice cg stand.
The ply wood you can see has holes drilled at the CG point. The ply wood has clearance holes for the wing tube and alignment pin.

Hope this helps Mark

RE: Trimming HELP!!!
 

Hi Mark

Just a quick question - I thought one has to measure CG of mid and low wing planes upside down. That is a mighty interesting stand yuse made up - I use a T/F CG machine myself.

Ok - another question or rather information - what plane am I looking at - it looks very good.

thanks, Greg

RE: Trimming HELP!!!
 

Greg

The CG can be measured with the plane up side down if you like. The CG is at the same point on the wing.

The Plane is a Smaragd ds/dt. Smarargd Fuselage with a Platform modified Temptation / Phemon wing. The Rudder and Fin is changed. Stab is Temptation.

The Plane fly’s very different than the stock Smaragd. Better I think. More crisp snaps and the plane tracks better.

Mark

RE: Trimming HELP!!!
 

MANY MANY THANKS... I think I will be hands on next weekend...comments/results on monday....

RE: Trimming HELP!!!
 

Hi Mark

Thanks the info regarding the CG and the very interesting plane.

Look forward to the results Aresti...

Unfortunately we're in for yet another cold front just in time for the weekend :-(

"so what comes after two days of bad weather?"

RE: Trimming HELP!!!
 

Very interesting guys.

I can't figure out what do you say, how can the plane require a bunch of down elev to keep inverted flight AND still be tail heavy???

Bryan, could you please explain that? Incidence is the key?

Many thanks for your help, it is very appreciated

RE: Trimming HELP!!!
 

Well, this is what I've found so far: the wing in reality had minus 0.5 degrees (frigging Great Planes laser meter, up is down with this tool!!) I moved the CG forward (heavy battery back in the plane) and reset the elev (0 deg) and wing (+0.5 deg) incidence. Test flight tomorrow....

RE: Trimming HELP!!!
 

Stek
when your airplane is tail heavy the elevator is less precise around center /Neutral
causing you to search for a nice touch on your inverted input
the feeling feels like its nose heavy because you can`t lock a inverted line
with the c/g forward the Elevator is much more responsive and precise
one fast and simple way to test if your c/g is right is by doing a loop
you should be able to use a single elevator input at halve or above throttle
and the airplane will do a very precise loop without further movement of the stick
if you are segmenting your loops and constantly changing you elevator input your prob,,,,,tail heavy.
With a forward C/G,
you will need less total elevator travel and less elevator movement
the inputs will be very forgiving and soft but responsive and easy to hit and hold your mark
hope this helps
Bryan

RE: Trimming HELP!!!
 

THANKS Bryan!!!

It's not easy to find such expert suggestions around, I'm very grateful to you.

Interesting point about CG loop test, today I'll try it!

See you soon

RE: Trimming HELP!!!
 

Aresti, how did the test go? I think the subject on this post is most interesting and it will be very helpful for others to find about the result of these changes in the trim of your plane.

Thank you

Mundo