Supercub Mod - ailerons

[Darlo0161]

Hello All, I bought a Hobbyzone Supercub to learn on. I have a four channel spectrum Tx/ Rx but the model is only 3 channel. I have decided to buy a new wing and add mini servos to give me Aerilons to convert to a four channel plane. The question is i have a wing strut anchor point relatively close to the trailing edge. So do I go for a long thin aerilon and go past the strut without touching, or a short thicker aerilon and not go past the strut ? How will this affect the flight characteristics, depending on if I flatten the wing to reduce dihedral.

[Levanter]

There are squillions of videos for just this mod on youtube. Mostly they take out the dihedral and fit a carbon tube in the wing. The struts then have no structural use and can be moved if necessary but in any case all the ailerons I saw were long and narrow, missing the struts entirely I have a Supercub abd there are some very useful hints and tips to do even to a new model. Wing saddle. Bigger wheels and lots more. The big question is ACT which for most people stands for Automatic Crash Technology. Most people it seems therefore turn it off or take out the sensors. There are other options to go brushless which I shall probably do after the first time I bend the prop shaft and trash the gearbox (soon then!) Let us know how you get on. I might make the mods myself sometime.

[Biggles' Elder Brother - Moderator]

Well, you asked about the physics! So here we go,..

The amount of force an aileron exerts is basically related to how much area is projected into the airflow. That in turn depends on the area of the aileron itself and the throw. In principle - and to rough approximation - there is no real difference between two ailerons of the same area but different depths. In higher speed flight it makes a difference if the aileron intrudes too far away from the trailing edge. But - for the FunCub it won't matter too much if you have a long thin or a short fat aileron - in terms of the force it will generate.

However,....that determines how much aerodynamic force the aileron exerts, but that's not the whole picture. We want the ailerons to bank the model and their effectivness in doing that depends not only on how much force they can exert but the leverage of that force. This means that ailerons further outboard on the wing work better for a given size and throw because they act over a bigger lever arm. This is why full size aircraft nearly always have the ailerons positioned well out from the wing root. So you can have smaller ailerons further out and get the same effect as bigger ailerons close in

However,....(again!) there is another factor. Ailerons that are only at the tips are out of the prop-wash, so as the model slows down they become progressively less effective - less airspeed leads to less aerodynamic force and so less moment. This is why a lot of models - particularly 3D types - have ailerons the full length of the wing. The outer bit works well in normal flight whilst the inner bit, which is in the prop wash, gives control at very slow speed like when harriering or prop hanging.

So, "yer pays yer money and yer takes yer choice" - all of them will work, it depends how you intend to fly the model.

BEB

Edited By Biggles' Elder Brother - Moderator on 08/07/2013 18:26:30

[Darlo0161]

thanks very much. i had seen the youtube stuff but a lot of the details are glossed over.

Beb - brilliant exactly what i was after, understanding the physics really helps me grasp all the things im learning. Your info made perfect sense to me, long and skinny seems to make sense.

reckon i will be ordering a new wing tonight.

can i really straighten a wing with a hairdryer and a carbon rod ? or should i keep the dihedral.

Thanks guys.

[Biggles' Elder Brother - Moderator]

Its very desirable to lose the dihedral if at all possible. Otherwise the ailerons will really just fight against the dihedral, and worse the dihedral in forge a "link" between the rudder and the ailerons in use - and you're much better off if that connection is not so strong.

BEB

[avtur]

Posted by Levanter3 on 08/07/2013 18:12:57:

...... The big question is ACT which for most people stands for Automatic Crash Technology. Most people it seems therefore turn it off or take out the sensors.

just slightly off topic ... but yes ... have never seen a good word written about ACT, this model is so stable it just doesn't need this. I disconnected the sensors before the model ever took to the air ... it is a brilliant introduction (or in my case was a re-introduction) to model flying.

[Simon Chaddock]

Darlo0161

There is one other issue concerning long thin or short fat ailerons and that concerns rigidity.

In most case the aileron is moved from one point yet the aerodynamic load is generated all along its length so it has to be able to transmit a torque from the aileron horn.

A long thin aileron is much more likely to twist so there is a risk that when under load the movement of the horn is not transmitted along the full length of the aileron. A short fat one not only has less distance from the horn to the ends of the aileron but will be much stiffer shape as well.

Do keep us up to date with how you get on.

Edited By Simon Chaddock on 09/07/2013 20:51:55