Im new in this hobby, I went to the field yesterday and somebody told me that I need to add right thrust. I have a Hobbico Nexstar, The engine is already "leaning" to the right. How do I determine the amount of thrust need it?

The Nexstar should have the correct amount of right thrust built in...mine does. What is the plane doing to cause them to say that? I have noticed that with the speedbrakes on that the plane climbs aggressively at full throttle. Trim the plane to fly level at about 1/2 to 3/4 throttle and it flies great.

Jess

2-5 degrees of right thrust should do fine. It helps the plane to track straight during take-off and climb, and to overcome some of the effects of the propellor/slipstream.

Jetts

But Jessh is correct, nowadays if the designers feel that right thrust is needed, it is incorporated into the design. It "should" fly well as is

Just to give you an understanding of what right thrust is about ....., or any "altered" thrust.

Firstly, "Down" thrust. You almost always want your engine to point down a bit, and here's why: The lift the wing produces is proportional to speed. The faster you go, the more lift you get. if your engine pointed straight ahead you would have to change the trim of your plane at different speeds (which is what most "real" planes do anyways, but it is a PITA). To counter-act this PITA, you build down thrust in to the engine, the faster you go, the more lift you get, and the more the engine pulls the nose down. A carefully designed plane will give just the right down-thrust to counteract the increased lift with speed.

Now, there is a problem .... With down thrust, when travelling straight, the propeller "disk" is not perpendicular to the airflow... the prop disk is tilted forward. This has the effect that the prop does not create an even thrust. As the prop is swinging up on the right side of the plane, it has a greater angle of attack. On the down stroke on the left, it has a lesser angle of attack. Whis basically means that the right side of the prop pulls harder, and turns the plane to the left. There are two additional forces, "Gyroscopic pecession", and "P-Factor". Gyroscopic precession basically means that as the engine spins the prop, there is a "torque" force turning the plane to the left. The "P factor" describes the way that as the prop spins it causes the airflow to spiral a bit in the same direction as the rotation of the prop. If you think about it, the air will be spinning up slighly on the left side of the plane, and "pushing" on the left side of the fin and rudder. This also adds to the left-hand tendency to turn.

Given the three forces that tend to make the plane turn left, the design also builds right-thrust in to the engine to counteract all the left-tendency forces..

So, bottom line is that to get a well trimmed plane, you need to have the engine thrust angles just right. I have built kits with as much as 2deg down, and 3 deg right thrust.

Now, if the thrust angle is wrong, an expert pilot will know, but for the most part, the average or beginner pilot would not even notice even if it was quite far out. I wouldn't know. So, get the reasoning for the suggestion to change the thrust angle, decide how much would you are willing to take on to change it, and then make the change if it all adds up.

gus

Bought a nextstar when I went to glow type aircraft. Found it very easy to assemble and looked a high quality RTF kit. Went to the field where experienced pilots helped me taking off and landing.

The aircraft was having a very clear tendency to turn to the right (quite a bit) on take off and once 10 mtrs off the ground it was fine. Did low passes and everything was just dandy. Started an assited take off, rotated and the right wing went down quite a lot, corrected and went all the way to the other side and the airplane was so low I could not take it out. Left wing touched the ground, the aircraft flipped twice.

Damage was limited to engine and firewall being ripped. Probably will be ready to fly for next week end. Should I be able to correct the freaking tendency to turn right on rotation, the aircraft is a beauty.

The Instructor's diagnostic is that the right thrust setting is just too much to the point it was making the airplane do what I described above. He put a washer between bulkhead and the right mounting screw and it corrected a bit, yet not enough as the incident still happened.

I think the right thrust down thrust thing is slightly over exagerrated. I'm not telling ANYONE not to do it but I have never done it and have had no ill effects. I spose for competition pattern where absolute perfect flying is a must all this should probably be taken into account but for the typical trainer, sport plane I'm bettin it's not necessary.

Furthermore it drives me up a wall to look at an airplane with a crooked motor.

Thought I would add a few things here. I'm no expert, so don't flame me if I'm wrong or you don't agree.

First, the NextStar is an ARF like my Xtra Easy II. Things can be sloppy or just not right with any ARF. I've flown several and seen a few more. You can expect to find anything on ARF trainers and they should be inspected with a critical eye.

My XE2 has too much down thrust. It looks like it is angled down too much. I put a 2 bladed prop on it the other day and I nosed it over into the grass when I gave it too much throttle for takeoff. It bent the nose gear over and went right on down. Nothing was damaged. I've always thought it was pushing down too much when I was using the 3 bladed prop (Evo .45 trainer engine.) It takes off fine if I ease on the throttle and hold up elevator like a taildragger.

Gyroscopic precession means that if you apply a tilting force on a spinning object, like a propellor or rotor system, the action will take place 90 degrees later. This is why we looked silly trying to hold spinning bicycle wheels in our hands while figuring out how to tilt them. We all did that, right? Same reason we looked dumb the first time we hijacked the school floor buffer for laughs and it kept zinging around knocking over chairs, hitting buddies ankles, etc.

elombama,
aimaintenance is right, the right/down thrust is not overly important, but still will make a small difference in some planes, a large difference in others-mostly depends on how exacting the pilot wants to be. We experamented with a sturdy birdy, and went from 0 right/down to 5 degrees both ways, and everything in between, and it didn't make a huge difference. I did build a very light, big, boxy "camera plane" (high powered, light wing loading) and the right/down thrust was very important, especially the amount of DOWN thrust.

I highly doubt that your "right wing down, right turn on take off" is due to right thrust. You'd have to have 10 degrees or more for it to do that! Maybe you have a balance problem, wing twist, or even just out of trim.
Best to check all that before you fly again.

Jetts

Elombana - I also have a nextstar and have the same right wing dropping problem. Take a look at this post about my problem. Maybe it will help.

[link=http://www.rcuniverse.com/forum/Aileron_Trim/m_1803835/tm.htm]Aileron Trim[/link]

While I still have not resolved my problem entirely, the advice I received has helped out alot. My problem is not nearly as sever as it used to be.

Ok...these are the things I corrected during the week. Haven't flight tested them but I think could really contribute to resolve the problem:

- The right elevator appeared to be coming up higher than the left one.
- The rudder and the nose wheel were not fully alligned.

Will let you know how it went.

Engine thrust angle and control deflection is not something I would worry about on a trainer. Due to the fact that the elevator thurst will make the engine track different at different speeds. Most newbies fly full throttle or some other throttle setting but do not manage the throttle setting so I would not worry about that.

As far as elevator deflection. Due to the servo being connected to just one side, the non-servo side will always have a little less deflection that the servo side when the plane is in the air. So I would not worry about it.

Ok....so that's what the solution is not...what in your opinion is it then?