Recently I got a .25 class old low-wing trainer, I put a .32os on it ,I did set 3 to 5 deg offset on thrust line to the right,but when taxiing on ground ,just a little advance on throttle will cause obvious yaw to left , So a lot of right rudder is required before it get airborne ,when airborne it has very strong tendency roll to left .I used a lot of right aileron to counteract the roll to keep wings level ,what should I do?increase riht offset or ?

after take off do you notice it still pulling to the left? Are you gunning the throttle on take off, that can be part of the propblem....try increasing the throttle gradually

The torque effect on takeoff is normal.

If the airplane has conventional gear ( taildragger) the torque effect will be more apparent than a bird with a tricycle gear setup. Add power slowly and apply the appropriate amount of rudder required to keep the takeoff roll straight.

As far a having tendency to roll once airborne requiring a lot of trim. Be sure to check the lateral balance you may have one wing heavier than the other causing the roll tendency. Also re-check your control surfaces for proper alignment if one or more surfaces are out of adjustment it can cause problems.

Another thing to check is the possibility of a warp in the wing which may of been caused by improper covering the shrinking up of one side too much. The problem can often be corrected by application of heat to the other side of the wing covering to bring the wing back to proper shape.

5 degrees offset to the right? Far to much usually.
All planes, especially taildraggers will yaw to the left as soon as the tailwhell lifts. Some more than others. This has nothing to do with the right offset/thrust of the engine!
Most RC pilots don`t know how to do a perfect takeoff with taildraggers. The trick is to add a small amount of down elevator early in the takeoff to raise the tailwhell, thus redicing the sudden yaw to the left. If the tail is lifted early the yaw will be softer and easier to control.
Right thrust is something which have to be adjusted doing a lot of trimming during flight. And of course everything have to be as perfect as possible first; no warped wings, proper CG, lateral balance, taped rudders and so on and so on.
95% of model pilots never try to optimize their planes after first flights, thus they never learn how well a plane really could fly How many pilots do tweak for optimal CG suiting their flying style???

Thank you Steve ,Indeed, right wing tip did drop and warp a little,I correct it with hairdrier,soon i am going to have a test flight.

The most thrust I have ever put in a plane was 3 degrees, 2 is about normal if I put any in at all. Depending on the plane itself I will start out with zero thrust then during trim flights I will add if needed. Some kits and ARFs come with built in thrust on the fire wall and that usually comes out to about 2. Joo mentioned adding down elevator on take off to bring the plane up onto step. {lifting the tail wheel} None of my planes have ever needed that, I have always had to add just a touch to keep the tail wheel on the ground until I have enough ground speed to steer with just rudder. If you are flying a trike geared plane and it's turning left then check your rudder trim and nose wheel to make sure it isn't bent or twisted. Remember, you do have to do some of that pilot stuff and steering is part of it. After a year of flying I just now got one of my old students to understand he can't let the plane get ahead of him, he has to react before the plane does anything that will effect his take offs or get out of control.

The OS .32 is a pretty strong engine. I've a LT-25 Kadet and fly it with a Saito .30 and a friend has one with an OS .32 and his flies twice as fast as mine, which leads me to believe that the engine might be simply over torquing your plane. Whether that excess torque can be compensated for by more right thrust beyond 3 degrees, I don't know.

You can test this by programming some limitation to the throttle to reduce the power of the motor and get back to the power band the model was intended. Then, if it still shows rolling left the problem could be a warped wing.

Another left roll issue could be P factor. If the motor is angled upward at all, it could play a big effect. Do you by any chance have much down elevator trim to maintain level flight? You may wonder what the pitch axis has to do with the roll axis and I'll try to explain briefly but you can do a search and get much more fuller explanations. If the motor is pitched up any amount, then the propeller no longer has equal pitched blades to the oncoming air flow. The left side goes less pitch and the right side goes more pitch with the effect that more bite on the right then yaws the plane left. Normally an engine will be zero down thrust to whatever it takes down thrust to maintain trim during the full range of throttle to counter wing lift at greater speeds but rarely if ever any up thrust.

Hi!
Sorry! But there isn't such thing as noticeable torque in such a small engine /plane combination!
The reason your model needs right rudder at take off is due to wrong setting of the wheels and perhaps landing gear location! -Or not using the rudder in the appropriate way.

Second ! The reason the plane needs right aileron is due to warped wing! The reason I can say this is that I have flown, constructed ,competed for 35 years!
Sorry for being so outspoken but I have seen so many R/C plane owners (novice fliers) that just blame torque in my days that I have to tell it the way it is! There even was an article in Model Aviation last month that wrongly blamed the torque factor!


The first problem is fixed by having slight toe -in and slight camber built into the landing gear wheels! You must also check that the wheels are not placed too far forward! Too far forward and the plane hunts at take off!!!

The second problem with the wing is easily fixed by twisting it with either a heating iron or a warm air gun, I presume the wing is covered with plastic film.
You should always have slight wash-out in the wing tips! Check it with a Robart "Incident meter" or do it with watching (eyeballing) from wing tip to wing root and compare which part of the wing that is twisted. On small .40-.60 size models the 0,0,0 law usually applies