The torque effect and Control line plane design

I have seen several references on the site to the torque effect induced by the spinning propeller when referring to control line flight. By torque effect I mean the tendency for the plane to want to roll in the opposite direction to the propeller.

I now have two control line models prepared and two in progress. However, these will be electric. My normal flying is RC and during the course of my progress I have made several observations. (mostly as a result of a near tragedy!)

These "observations" have been amplified by my watching progress in the CEF speed contest partcularly some of the struggles "taking off" and my imminent return to control line.

My only really disastrous flight in my previous control line history (some 45+ years ago) was with profile fuselage model with built up wings and a DC Bantam .75cc glo engine. My first glo engine and first profile model. I had previously flown 1.5 cc to 3.5 cc diesel models and, I have to say, never experienced slack lines always feeling a "pull" on the handle. This experience, the plane was uncontrollable, I first put down to being underpowered. Following the "handle" comments - I flew this with my then standard 4 1/2 " handle - I put it down to the handle. Then I got to thinking - "The lines were slack but it was flying!"

I have an inbuilt reluctance to repeat this and still somewhat of a disdain for profile models!

Back to my observations.

Firstly, with RC ( and I only fly electric "tail draggers").

1. All my planes have a distinct right thrust set.

2. If the wing and tail plane are in line with each other and the thrust line of the motor there is no downthrust set. (3D style aircraft usually!)

3. My "High wing" planes all have some downthrust set.

4. All planes have a tendency to roll a little to the left on take off and need a touch of aileron or rudder to correct.

5. Being Rc they are eay to trim true during flight. However this only usually is relative to speed.

6. Increase power on a "High winger", after trimming and it will climb and roll to the left.

7. On a 3D model, increasing power induces no climb but a left roll.

8. The smaller the plane - the more rapid is the roll and the climb when increasing power.

9. The larger the wingspan the more stable the plane remains.

10. Trying a more powerful motor with a larger propeller can be disastrous. A relatively stable model can turn into a skittish little deamon!

Now to control line.

1. I fly electric and am aware that in converting to electric I will be using larger propellers with more pitch. This will amplify the tendency to roll left or inwards.

2. My successful I.C. control liners all had a few things in common.

a. There was side thrust on the engine
b. The inboard wing was usually longer than the outboard wing.
c. Some had right thrust on the fin - Some didn't.
d. Some didn't have a fin.

3. Once the plane is in motion - you can't trim it on the fly!

My admiration for the CEF speed contest designs and the executions of the builds is immense. All my planes have been plan builds, kit builds and, in recent times, a.r.t.f.

To design and build a scale look alike with no provenance is a brave undertaking. To do this with the aim of a high power to weight ratio is even more adventurous. The two most difficult planes I fly are a 15" span Spitfire and a 14" Focke Wulf. They fly nicely when cruising but throttling up becomes stick waggling time with a vengance. I broke a propeller on one and replaced it with one which I thought was equivalent and it was unflyable!

After chatting with some electric control line chaps - their recommendation is to reverse the rotation (easy with electric, swap any two of the three wires to the ESC) and use a pusher propeller. This turns the torque effect to advantage for control line.

It does make me wonder if there would be an advantage to this with the Bee powered control liners, as the Bee will run quite happily in the opposite direction, and is there any clear advice on control line plane design?

It is obvious that there are clear favourites for stunt flying. The Skyray, Twister and Yak to name a few. What is there in the design of these and the other popular 1/2As that make them popular and comfortable to fly? What are the similar features in the designs?

I would welcome all comments and observations.