griesel

I just finished assembling a Nexstar Arf and on the early flights it does not turn when in a
slight climb. The plane weights 7lb 1oz and is balanced at 83mm; the book range is 81 -
90 mm. All throws are set to the book value including differential aileron settings. It was
built using 6 servos with a 3 servo wing; flaps, left and right aileron. It was originally
built with air brakes and bumps, but required almost all down elevator trim to fly level at
half throttle. The air brakes were removed and the trim changed to two up clicks of elevator.
The theory is that the airbrakes were disrupting the airflow to the tail. The problem seems
to happen in a shallow 30 degree bank when flying into the wind although it happened once
in a cross wind. The aileron differential is 1/2 up - 3/8 down. The problem is probably
adverse yaw and is apparently inherit in the design as evidenced by the differential aileron
setting. My instructor said this is the third Nexstar he has flown and they all did this.
What can I do to fix this problem?

jetmech05

the only problem I've had with a Nexstar like this, was an aileron that had a piece of wood inhibiting the travel of the pushrod. The wood only stuck out far enough to inhibit the travel intermittently...I am assuming you've held the airplane at the same attitude and checked for binding? Then I'd try and see if it happened turning with just ailerons, or ailerons and rudder...perhaps the pushrods or the servo arms are hitting each other.....I doubt it's an airflow issue

CGRetired

My Feedback: (1)

Jetmech.. he said he has aileron servos (plural) so I don't think that there is a blockage from the torque rod because he isn't using one.

From the description, it looks like he had free movement of the ailerons. The big problem with any aircraft equipped with flaps is their inteference, if not set up right (out of the airflow so they do not cause problems) is just that. If there is even a slight deflection, it may cause the ailerons to become ineffective.

Why would you want flaps on such an aircraft anyway? It's a trainer.

Albeit, you may check to make sure that the bottom of the flaps on both sides are perfectly lined up with the flat bottom wing so that there is no deflection noted. Use a straight edge and place it across the bottom of the wing and make sure the flaps are not even slightly deflected down.. or that one side is not a bit down as compared to the other.

Then add more deflection to the ailerons. Try increasing it by 1/8th of an inch on both sides, both up and down. You will still maintain the differential but get more deflection and more authority. If you are concerned about adverse yaw, then mix in some rudder. And, of course, make sure you don't have any binding, that the ailerons move freely with plenty of room to move both up and down.

Let us know what you find.

CGr.

griesel

I have a JR7202 transmitter and I think coupling in some rudder would be the easiest answer.
I wonder what is going on with Hobbico as all of the Nexstars he flew were bought recently.
Any ideas on what % coupling. I was thinking 5%, but thats probably too small.[>:]

nobodytwo

The NexStar's training equipment actually works very well! The "flaps" keep the plane slow so that the student has time to react, the droops give a better stability during landings. The biggest problem with the RTF setup is the aileron and rudder can't be coupled. Adverse yaw affects ALL high wing aircraft. A good example is the cub, ever try to turn that plane without the rudder? Here' is a link that will help you get the NexStar under control: [link=http://www.rcplanetips.net/NexStar.htm]NexStar Tips[/link]

Happy Landings

nobodytwo

Coupling is one to one or 100%. The when the right stick moves right the rudder moves right and the right aileron moves UP.

Happy Landings

Scar

My Feedback: (3)

Griesel,

I must ask, were you trying to turn without rudder?

I would suggest not mixing aileron and rudder. Try turning with the rudder. You will see the plane roll in the same direction, to the extent that you will apply opposite aileron to keep the bank angle reasonble. For that reason, I don't mix aileron wth rudder.

Best wishes,
Dave Olson

Flying freak

Just for clarification-

You cut your ailerons in 2 to turn the inboard parts into flaps. And keep the out board section as ailerons. Here is the thing didnt bby you doing this DRAMATICLY decrease the size of your ailerons? So if you not have half the surfacce area wouldnt you need double (or clsoe to it) to get the same roll rate?/????

Steven

exeter_acres

My Feedback: (2)

What does your instructor think is happening??

da Rock

The mfg suggested aileron differential for a reason. Every suggested surface deflection is just a starting point really. And if the mfg's suggested deflections and differential amounts aren't working for you and your specific airplane, the next step is to tune them so that they do work for you. Simple as that.

Try increasing the differential. If the problem is adverse yaw, you'll have less. The problem will be on the way to being solved.

Beginners tend to accept the suggested throws as chiseled in stone. They are not. Matter of fact, lots of assembly manuals are not even close.

As soon as you taxi out a model for the first time, what it does from that secon on is 100% your responsibility. And whatever you wish to do with the deflections and such is completely within you control. If the airplane needs throws changed, you change 'em. Beginners also tend to believe that any change in throws will result in massive performance changes. Wait until you try your first. You'll understand then.

da Rock

Be careful about slapping a mix on an airplane until you know what all is involved. You're wanting to mix the rudder to the ailerons to fix an aileron differential problem. It might be the proper solution, but before you do anything, find out what the rudder does by itself. No lie, lots of airplanes have rudders that do WAY more than just yaw the airplane when they move. Lots of models actually have mixes on the airplane to FIX the problems the rudder causes.

Rudders very often couple into pitch and couple into roll. Just moving the rudder on my CAP232 would almost violently pitch the airplane and would roll the sucker at the same time. It was like the devil had posessed that rudder. You do not want to plug some rudder movement into anything until you find out what it does by itself.

Fly the airplane straight and level and simply push rudder one way and watch what happens. Now level it back out and push rudder the other way. Sometimes you get different reactions. Sometimes the same reactions but more or less amount.

Do some research on all your surfaces in the first flights before you start throwing mixes at an airplane.
And fix any problem at the source of the problem if you can. Your ailerons are giving you a problem so fix the ailerons if you can. And more differential would seem to be the first step in that direction.

BTW, you might wind up with the best flying Nexstar. And what you will get others don't is the experience flying an airplane with different settings as it is changed to fight the problem.

It's actually fun to do all that stuff.

Al Lewis

I take it you increased the throws on the ailerons proportionally when you cut 5" off of each of them to do the flap modification?? They need nearly full throw after that mod. I had to when I modified mine. Felt it became very unresponsive so I left it stock when I replaced it with an ARF version. Oopps! Sorry, I see Flying Freak already asked that. Only other problem I ever encounted was the wind. Nexstars do not like being flown in the wind. That big wing gets tossed quite a bit. The down elevator is necessary because of the air brakes which pitch the nose up. The flaps will do the same thing.

Art Cloutier

The Nextar my last student had behaved as you have described; we tried to blend a little rudder but found it pitched so hard to the landing gear that was not a help in getting a level turn. We finally crashed it after much experimenting with its rather poor handling characteristics. We were both glad to see it go. I think it is the second worst handling trainer I have experienced. The worst was the Perfect Trainer by Great Planes. Art Cloutier

Al Lewis

*

rceric

Art,

The Nexstar has got to be one of the easiest planes to fly I have ever seen. It is almost crash resistant IMO. My 7 year old can fly it with no problems. If you had that bad of an experience with one then something had to be set up wrong in the first place.


Eric

Al Lewis

I said that in my earlier deleted post but decided it was off subject. Couldn't believe he crashed his students plane. My grandson flies mine now. Without a buddy cord. ( 10 year old )

ramboy

The worst was the Perfect Trainer by Great Planes.



Can you give us more specific detail ?

Al Lewis

Not sure Art is a "specific" kind of guy.

CGRetired

My Feedback: (1)

I trained on the Nexstar Select RTF and both my instructor and I found it to be a fine trainer, even with the wing tip gizmos and the brakes. I dinged it up two times, not seriously, and both were my fault. After that, I flew it in a strong cross wind and learned a lot about such flying. It was difficult and, at times, scary, but I managed it and never crashed it once.

That was several years ago and, I've since sold the plane, and as far as I know, it's still around and training student pilots.

No complaints about the Nexstar, for sure.

I've already put my two cents worth in as for his situation and still feel that he should not have cut the ailerons and put flaps on that plane.

CGr.

ramboy

CGRetired - how do you like your Protege? Would you recommend it as a first plane?

chevypower1930

im thinkin this is due to the "airfoils" on the leading edge of the wing.. My first plane was a Nexstar and I still fly and LOVE it... but all the training equipment is good for a BEGINNER... somebody first training without ANY flight experience.. but I never used the air brakes or AFS.. I used the "airfoils" for the first few flights and then took them off.. you know the "airfoils" are actually called by Hobbico the "anti-spin" airfoils.. so Im thinking thats your problem... try it out, I promise you you'll be able to fly without them if you've already flown it. not a big difference but I think it will help out on your climbing turns...

clouddancer

I trained with the nextar. The droops and drags were meant to keep the plane stable and allow for slow
and stable flight and landings. I also needed alot of down trim, just to maintain level flight.
My instructor found the the droops and drags to be quote: unwanted cruches, and were removed after the maiden flight.
The plane flew better imo, after taking them off.
This plane seems to have a lot higher dihedral than other trainers, i could be wrong,as i never measured for sure.
The nexstar was designed to be stable in level flight, but the high dihedral made it harder to bank with just ailerons,
especially in a moderate wind.
I mustled it around using rudder for turns, but didnt like the way it banked.
After i soloed i lowered the dihedral alot , i used someone elses degree meter, and sorry,dont remember what it was set at.

It did however make the plane fly great. And banking was easy by just using ailerons.
I think it would have been easier for me to learn on had this been done in the begining.It flys similar to a cessna now.

Heres a pic of the plane after the mod

Art Cloutier

The high dihedral planes I have flown often have too much adverse yaw to be very resposive to aileron inputs. On some of these planes it is an improvement to remove most of the dihedral. It may also help to raise the ailerons about a sixteenth on an inch above center. If the dihedral is too much it also tends to make the plane roll out of turns which increases the pilot's workload when flying constant radius turns.
Flying a fully symmetrical wing with no dihedral is easier than fighting an overly stable trainer. It is easier to deal with a light wing loaded plane which goes where you point it than to fight most of the hyper stable trainer types. Art Cloutier

hogflyer

Here's my experience with the NextStar. I have one and I'm currently training a student on one. NextStars need lots of aileron throw to get a decent roll rate. By cutting the aileron to incorporate flaps you have greatly reduced the amount of aileron available to bank the plane. When I set mine up for flaps I used full span flapperons, not the split aileron/flap. I set the aileron throw for the maximum I could get - the limiting factor was the bevel on the aileron its self. The flapperons dropped almost to this point and it flew on mostly differential aileron with full flaps. As far as the training aids - keep them off the plane, especially with flaps or flapperons. The landing speed is reduced quite a bit using just flapperons.

The easiest solution is to mix rudder for your turn. NextStars will bank just fine using only rudder, and I've demonstrated this by flying short flights without touching the ailerons, just the rudder. Start by manually coordinating your turns with the rudder to see how much throw you actually need, then start mixing that in and test some more, adjusting the amount of rudder required.

The best way to fix this would be to cut the ailerons and flaps off completely and install new ailerons. This would not be all that difficult, you just have to be careful when installing new hinges not to put one where the old hinges are - hinge points would be the best to use in this case.

To anybody else out there with a NextStar: DO NOT cut the ailerons for the flap option as indicated in the instruction manual. If you want to experiment with flaps, install dual aileron servo's and set up for flapperons using the mixes on your radio. Mine has shown absolutely no tendency to tip stall at full flap, and I've tried every way to tip stall or spin and it wont! You need all that aileron for a decent roll rate!

Hogflyer