freeCAD and fuselage creation

Always use 2 separate channels for the ailerons when possible

jon
This shows a mechanical differential set up.

With the arm angled forward at say 45 degrees when the servo is in its mid position will give nearly twice the 'up' control surface travel compared to 'down'. It requires no additional parts to do it.
How much forward angle determines the degree of differential. Much over 45 degrees can result at maximum servo travel that the down aileron starts to reverse direction and reduce the amount of down.

Just a historical note.
This 'reverse' effect did actually happen on the down aileron at full control deflection on the full size Slingsby Skylark 4 glider. It had considerable aileron differential due to its huge wing span relative to the fuselage. For what was a high performance glider at the time it was very well mannered.

Thanks for the sketch. Before I saw this post I had looked and found some examples on the web. I am working up some adjustments to trial and see if I can get the down angle to be about half the up angle for a start. Will see about filming the movement and measure the angles....

The Skylark 4 aileron only reduced the down movement at the last bit of full control movement.
Not everyone even noticed it and I never found out if it was done on purpose or was just a result of the substantial differential geometry it used.

I posted a brief video of a test differential servo arm and horn arrangement on the 'widgets' thread. It kind of works, so many variables to try out.... Would appreciate comments. -Jon

Interesting thing I noticed - the sketches are with the servo at the base of the wing and the linkage below. I seem to have a patter of the linkage above the wing - probably to keep it away from the wet grass. Perhaps it would work better if I went with a below linkage? -Jon

I have put almost all the final touches to my latest Clarke-Y wing - just the linkages to the ailerons left to do.

Here is it just before I glued on the top skin...



It has been a bit of a journey. I gathered the three Clarke-Y epochs in the image below.

The upper wing is the original attempt which turned out a bit heavy. Original Clarke-Y wing:
153mm chord x 960 span, 260g 9.171 oz (inc wiring & servos). area = 0.1468m^2 1.58 ft^2
wing (only) density 5.8 oz/ft2, aspect ratio 6.27, constant rib section.

The bottom wing in the photo is the 2nd iteration which is considerably lighter:
115mm chord x 700mm 123g 4.338 oz (including wiring & servos). area = 0.0805m^2 0.866 ft^2
wing (only) density 5.01 oz/ft2, aspect ratio 6.08, constant rib section. Yesterday I tweaked the
aileron horns to give a bit of mechanical differential (it uses a Y harness and thus I can't use
the transmitter functions for this).

In the middle is my 3rd iteration which has several rib depths:
123mm chord x 1000mm span, 178g 6.278 oz (inc wiring & servos). area = 0.123 m^2 1.324 ft^2
wing (only) density 4.742 oz/ft2, aspect ratio 8.13, rib section varies. The ailerons are (as previously
commented a bit small but workable). I have setup a mechanical differential.



From the front the changing depth of the wing from the root to the tip is slightly apparent. It has a bit more dihedral than the 2nd iteration.



I remember Simon showed a strength test. I did a quick one - with no load, 500g in the centre and 1kg in the centre.







I did a calculations to compare the 1st, 2nd and 3rd iterations vs the oval fuselage. My last flight with the 2nd generation wing indicated it was not quite the slow flyer I was hoping for:

Oval fuselage with 3cell 650mAhr battery, 2206 motor, 155mm slow prop (216g for everything but the wing)
orig large wing 476g 16.79 oz / 1.58 ft2 = 10.62 oz/ft2, cube loading 8.45
2nd generation small wing 334g 11.781 oz / 0.866 ft2 = 13.6 oz/ft2, cube loading 14.6
3rd generation medium wing 394g 13.897 oz / 1.324 ft2 = 10.496 oz/ft2, cube loading 9.122

The cube loading for the small wing reflects the need for speed.

The 3rd generation (medium) wing has a much better loading. Interesting that the 1st generation (heavier) wing has a slightly better loading - but not quite the aspect ratio.

Really, to get a decent loading with the 2nd generation small wing I will need to go to a 'stick' fuselage with a smaller motor and battery. If I can get the weight down somewhat here is what I am looking at:
small wing + light front non-wing 279 g 9.841 oz / 0.866 ft2 = 11.36 oz/ft2, cube loading 12.21

If I can find a lighter ESC and perhaps shift from the 8mm carbon fibre boom (30g) and pay through the nose for a 3 or 4g servos for the aileron and a skinned rather than printed aileron the small wing might begin to be a bit more of a floater. I have ordered some lighter servos.

I still need to see what tweaks are needed to get an initial COG for this new wing on the oval. Given that the field is likely to be sodden and thus a risk of a muddy motor if the landing spot is unlucky. . -Jon

I measured and the up angle is 30 degrees. -Jon

jon
Nice load test!
At 1kg at the centre for a 9 oz model suggest the wing is considerably stronger (heavier) that it really need be. Your test would suggest the wing is good for pulling a 12g manoeuvre. That's up in company with the Euro fighter!
No harm in being plenty strong but if you are looking for a slow flyer then every little helps.