Improving on the Clark Y Airfoil

[Peasant_Pilot]

Good afternoon, looking to see anyone's thoughts on a good improvement on from the Clark Y airfoil, I believe these are a good airfoil with relatively stable stall characteristics but is o tad on the older side.

 

not wanting to reinvent the wheel but looking for honest opinions on maybe a better designed airfoil for better STOL Characteristics, 90kn cruise etc.

 

Cheers

 

Rob

[bushcaddy105]

The BushCaddy family (no longer in production) used a modified Clark Y with a completely flat underside. Works well for me, with lots of lift and a benign stall at 32 knots indicated. That's without flaps. The R80 is the baby of the models and doesn't use them.

[facthunter]

It still works as good as it ever did. You certainly don't want to go laminar.  Nev

[spacesailor]

The Hummel-Bird used the " clark- Y- airfoil .

Then a ' modified ' Clark. Y .

spacesailor

[LoonyBob]

The Clark Y, and 43012, were far and away the best low Reynolds number sections tested by NACA... 43012 doesn't have the most benign stall, but as used in the Jodel D18, the upper surface fabric bulges just enough to give it a trailing edge first-stage stall, nice and easy. The Austers with 23012 (j5?) were capable of stol performance, and the stall was manageable. CY and CYH both have very progressive TE stalls...

[facthunter]

A small radius leading edge will give a quicker break away.   Nev

[djpacro]

The Aviat Husky has a modified Clark Y, it works well.

One of my favourites is the NACA 4412.

 

However, at least as important as the aerofoil is the wing planform and washout etc. 

NASA CR-1646 A DESIGN SUMMARY OF STALL CHARACTERISTICS OF STRAIGHT WING AIRCRAFT

https://ntrs.nasa.gov/api/citations/19710021678/downloads/19710021678.pdf 

[facthunter]

Some aircraft have different wing sections along the span of the wing. The DC-4 has two.  There's no reason why not. Nev

[LoonyBob]

Errum, a small radius LE may give a quick break-away, or it might give short-bubble separation - which in turn may result in a LE stall character, or a TE stall character, depending on what's behind it... the "original" CY, about 9.3%? T/C, has quite a small LE radius. Certainly a lot of WW1 airfoils w/tight LE radii gave bitey stalls. The Gottingen 398 (from memory) is a bit of a weirdo; it has a high maximum lift coefficient at lower Reynolds numbers, which works out quite well for the Thruster T300/500... Va, Vb, and Vc are very close!

 

Interestingly, if you use the NACA system to expand the ordinates of CY to 12% thick, it becomes astonishingly close to 4412. As a speed freak, I don't like 4412's pitching moment; but for a STOL aircraft, that scarcely matters.

 

Yes, planform, twist, and Reynold's number, dogteeth, slots, slats, VGs... HS size and position... the Jodel wing is quite a sophisticated solution to the challenges of a small runaround.

 

WRT section changes, yes indeed - the Jodel uses a 5-digit section for the constant chord bit, then transitions to (ignoring the aileron) what looks like Clark Y at the tip. This combination was popular for a while; there are a few gliders with the same mix (can't remember which, offhand!).

Interestingly, most such transition by straight generators, meaning the intervening airfoils are unknown/untested... there is no telling where along the span, the separation may transit from TE to LE.

Caproni made a few gliders that used "step" transitions, and seem to lose no performance as a result.