Airfoil suggestions for Mini Ventus

[crashdaily]

Hi,
I bought a Mini Ventus, but I am a bit disappointed with the flying capabilities of that plane. It is prone to tip stall and not very easy to fly. it's quite heavy too. I want to rebuild it - make it lighter and better for thermal flying. A new elevator is not a problem (the original is too heavy and flat). New wings are necessary - I want to make them polyhedral with flaps and ailerons. My question is what airfoil would you suggest? I am a fan of RG15 - but there might be something better for this plane - maybe MH32 (?) or some AG (?), Sellig (?) HQ (?). Once again - I prefer thermal flying.
Thank you for your suggestions.

I should include some more info:
Chord: 200 mm (7.87 inch)
Wingspan: 2680 mm (105.5 inch)
Weight: 1800 g (64 ounce)
Wing trailing edge - elev leading edge: 550 mm (21.6 inch)

[crepincdotcom]

A 7037 has great L/D charactoristics but still can thermal a good bit (as opposed to the 7035 which likes to break through wind). Either the MH32 or the 7037 would be m suggestion.

Also, how big of a polyhedral are we talking here? A 6" uplift at the end of the wing can be cool, but it seems like a scary idea to me to have a serious polyhedral AND flaps/ailerons.

Have fun,

-Jack

[vintage1]

My limited experience of high aspect ratio sailplanes suggests you have a choice. Tip stalls and a fantastic guide, or stick washout on, and get benign handling, and a much worse glide.

YMMV

[crashdaily]

Thank you for your suggestions. I think MH32 will be the choice. It's thick and this add to the strength.
The polyhedral - 600 mm (23.6") flat piece on each half, then 550 mm (21.6") with ailerons 127 mm (5") up and then tip of the wing 150 mm (6") long again 120 mm (5") up (relative to the first poly).
Can I ask you Jack why do you think but it seems like a scary idea to me to have a serious polyhedral AND flaps/ailerons. I designed a 2m (78") plane (is on my avatar) with "a serious poly" and ailerons and it flew well - except that the ailerons were not so effective, but rudder was enough to turn the plane fast. I do not expect the plane to be a hotliner or seriously aerobatic, I want it to be good in thermal and easy to handle.

[crepincdotcom]

Well in my experience ailerons on a polyhedral wing do almost nothing - the primary control is rudder (as you state). I only built one wing as such, and found that I almost never used the ailerons. If you say yourself that the rudder does most of the work, why do you want the ailerons? I'm all for lots of control (please let me know of cool things you can do that I'm not aware of) but frankly I've never found any benefit to the aileron+polyhedron setup.

-Jack

[crashdaily]

Thanks Jack,
I was confused with the flaps/ailerons statement. Now I understand and I fully agree with you. But on my new wings the polyhedral will be small, so the ailerons will help (or won't do a harm).
I will post a photo and my experience once it's out on the field and safely on the ground (I hope). :)
Cheers,
ZB

[crepincdotcom]

Ah ok. Small polyhedrals (both in length and angle) are fairly standard on the end, I though you were going more for a 2m-trainer style HUGE polyhedral. Makes sense now.

Have fun,

-Jack