Yet another Super Cub - but a bit different.

Decided on a contrasting colour scheme!

Still a bit more finishing to do.

As it suffers seriously from motor torque at slow speed I am thinking of changing to a 3s along with a smaller and finer pitch prop (6x3 rather than the current 7x4).

It won't be torque from the motor Quorneng, it will be the prop wash that's causing it and 2 degrees of right side thrust will put it right.

I am not sure you can say it isn't motor torque after all the rotating prop wash is a direct result of the motor's torque.
Side thrust counters it by simply dragging the plane sideways through the air which creates a counter roll effect.

The Super Cub is fine except at very low speed, like 4 or 5 mph, when the ailerons simply have insufficient power.
I doubt if side thrust would make much difference in this sort of situation.

Of course the only positive solution is either to have the ailerons directly in the prop wash or counter rotating props!

In the mean time I have increased the nose radius of the wing section to better control the airflow at high angles of attack and it has improved things somewhat.
This mornings video.

This afternoon I actually managed to achieve a proper landing and take off. Not bad for 1.75" wheels with 2" long grass!

Hopefully I will be able to video one this evening.

Try looking at it this way;
Someone builds a model and because of what he thinks is engine torque he applies 2degrees of right side thrust, and so now it flies straight.
but what happens if he flies the model inverted? the engine still turns the same way but now he has left thrust.

Engine torque causes the model to twist and not to just pull the model to the left and is corrected with the ailerons.
If you look at a model in the pits when it's running just see where the grass is being blown behing the prop, if it has no side thrust the prop wash will be blowing slightly to one side.

In free air the rotating column of prop wash does not move off to the side but when on the ground the surface drag slows the lower part of the rotating column with the result it no longer travels straight. As it now strikes the side of the fuselage and fin it causes the 'swing' on take off. This is corrected by the rudder. I am not sure side thrust has much effect on the ground.
Once clear of the ground the prop wash is no longer 'bent' so the swing disappears but the effect of motor torque does not and has to be corrected by aileron trim or side thrust.

Nice!!! It looks so smooth and graceful in the air, well done Simon.
Ps whats that beat sound on the video? Am hoping thats not your heartrate :ohmy: if it is thats one strong mic on that camera and a very bradycardic BPM!!

Quorneng wrote: Once clear of the ground the prop wash is no longer 'bent' so the swing disappears but the effect of motor torque does not and has to be corrected by aileron trim or side thrust.

I disagree, any motor torque cannot be corrected with the rudder, remember that it is a twisting force and can only be corrected by the use of ailerons.

Surely every single engined plane, particularly high powered ones have to use the rudder to stop the swing on take off, unless of course it has contra rotating props!

I managed to complete a full take off and landing sequence this afternoon.

All of a sudden it has started sounding like it has a gearbox!
I fear a motor bearing is on the way out and that's after only about 5 minutes running!

Sarah
The interesting noise is the well drilling company sinking a 3' diameter steel lined shaft using what can only be described as a big hammer!
It actually a big weight that is repeatedly lifted up about 3' and then dropped crushing the rock under it. The bits are then washed to the surface. It has been pounding away all day every day for a week! :woohoo:
They finish at 5 so it is not on the second video.

I commented the Super Cub now sounded like it had a gear box so the motor had to come out.

Looks brutal but it is the penalty for a lightweight build it all in technique.
When I took the motor apart and extracted the front bearing you could feel it grating when it was rotated. :woohoo:
Fortunately I have a spare.
I will take the opportunity during the rebuild to add more down thrust.

The new motor tube.

A bit larger diameter this time to give more clearance to the motor bell and flush with the top of the cowl giving about 3 degrees down thrust.
All complete.

And you can hardly see the join!

I'm sure you've already said this Q, but how and what are the wings struts?

The struts are hard balsa.
The rear is smaller, 5x1.6mm so 2 laminations of 0.8mm sanded to profile.
The front is bigger, 8x2.6mm so the skins are actually formed over an 1mm spar with just the leading and trailing edges sanded to an air-foil section.
At the moment it does not have the scale intermediate struts so has a limited negative g capability but it has been static tested to 8g positive.
The wood content in the struts is just about the same as I would have used if the wings were cantilevered with spars.

The latest update is it looks like the wretched ESC has failed on me despite being tested twice during the rebuild installation. BEC still works but the motor just spins once and then stops.
Rated at 10A, cheap and of dubious quality I had hoped I could get away with the light duty in the Cub. It will require another hole making (probably in the underside) to replace it. Better quality 12A ordered.