Dear Akram,
thanks for all your inputs. Based on those I checked a couple of things, but step by step.
First Impression based on first inputs
• Thrust axis is too less --> 4°
• Angle of attack (fuselage) 2,5° is locking good
• CG is to much in the front --> must be nose heavy, but maybe compensated by thrust axis*
• Inner profile is matching with my choice
• Washout only on main wing with 3,3° --> Little bit high
• Transition to a NACA (tip of the wing) --> influence on stability?
• NACA on wingtip with no additional negative angle of attack --> influence on stability?
• 2,5kg --> bumble bee, flying brick…..
Second impression based on additional information
• Inner and outer profile of main wing identical --> same for my P212
• CG movement to the rear makes it instable --> first impression wrong*, but still wondering because my CG is more at the rear --> Influence by the fuselage or something else?
• 2,5kg with 1m wingspan and it fluw --> wow great design
• Small rudder surface
FLZ analysis
For this project I`ve chosen flz voretex for the airfoil definition the first time, due to the uncommen wing design. Up to the first flights I have had no feeling, if it would work also in reality, but with the flying prototypes I built up a good trust into this program. I scaled my flz model down to 1m and made some calculation with your figures and please have a look to following result.
• Stability index due to same profile on inner and outer profile going down from 10% to 7%!
• Only 9,5 degree angle of attack leads to stall
Recommendations based on theoretical and prototype experience
• Build up your next model a little bit bigger so that the duct inlet diameter has 70mm. You get more space to install the fan, also with a thrust angle of minus 2-4 degree
• Save weight: 1m wing span -30%; 1,2m -20%.
• Airfoil adoption
- Possibility one: use the profiles of the plan
- Possibility two: Inner and outer profile similar (in accordance to your profile) with -3,3° washout. BUT additional -2,2 ° angle of attack for the outer small wing with the NACA profile
- Possibility three: Inner and outer profile similar (in accordance to your profile) with -3,0° washout. Usage of same profile for the outer small wing and in addition -2,5 ° angle of attack
-->I would use possibility three due to the highest angle of attack with 12°
• Add an additional control surface on the outer small wing
• Be carefully with hand launch due to stall behavior (huge washout, low speed --> less rudder controle)
Hopefully this will help you in building up a new one!
Hopefully we have next year a couple of P212-3 maiden videos on youtube!
BR and nice weekend
Markus