REPLACING A BYRON A-4 WING SET. DONT LIKE THE FOAM THEY USE. I THINKING OF USEING A NACA 9% SYM.AIRFOIL.. NOT A CAMBER ONE. NEED LESS DRAG. BUT ALSO WOULD LIKE TO HAVE IT PULL TIGHT TURNS.. MY SECOND CHOICE WAS A- RG 9.3 AIRFOIL. .045 NEG.MOMENT.. MAY NEED 1 DEG POS. IN MAIN WING OR .5 NEG IN STAB.. ANY OTHER SUGGESTIONS?? THANKS LOOKS LIKE EPPLER 193@ 9.1%1.5 %CAMBER. DONT HAVE DRAG INFO YET..

To both go fast AND be able to pull tight turns you are best off looking for an airfoil with some low amount of positive camber. When you look at the Cl vs Cd chart look for airfoils that have the more vertical portion of their lift where the drag changes but little centered at around the Cl=0.3 region of the vertical axis. You want an airfoil which extends this more vertical portion down to the Cl=0 like and up as high as possible but which still gives you a good thin airfoil to work with.

I'm not familiar with the airfoil used on the original model. But it's highly likely that you can put the new wing onto the fuselage at the same angle as the old. Then play with the CG location to achieve as small an amount of pitch stability as you can manage. Doing so will aid in allowing the model to turn as best as possible.

A degree of washout would likely not hurt either. But if you use too much washout then the tips will be flying at a negative angle of attack at high speeds and produce more drag than you want. But around -1.0 to -1.5 degrees of washout SHOULD aid in avoiding tip stalls in high G turns.

THANK YOU VERY MUCH .. 1.2 TO 1.5 CAMBER IS WERE ILL START.

If you want it to do tight turns, the airfoil really does not matter, the weight does. With model airfoils all performing much the same, regardless of section shape cause the all stall around the same AOA, the determining factor in accelerated flight, ie turning, is wing loading. Make it lighter, and it will turn better.
Evan, WB #12.

YEP.. THAT ALWAYS WORKS

If you're cutting new cores and want decent turn and stall characteristics, consider going progressive, with say the 9% at the root transitioning to a 10 or 11% towards the tip. With sheeted foam its easy. You'll feel a stall approaching with this scheme - it won't hit you like a hammer suddenly.

Cutaway, could you explain the reasoning behind this? At low Reynolds numbers adding thickness makes for a lower CL_max and would make 'tip stall' worse. I've heard quite a few people advocate this but I'm genuinely interested in why it's caught on or what empirical evidence there is for it.

To my mind it makes no sense to conisider thickness without the context or looking at camber and washout.

To some extent it will depend on the Re you operating at...



Evan, your right to a point IMO, weight is a big factor in the lift equation and you won't get 'more' lift from the airfoil with camber... but you may be able to get less drag. And that's the point - tune the camber for the kind of lift coeffients you will be flying at and it will loose less energy in the high g turns. Like in a pylon racer it's a compromise between speed in the straights and the turns.

That's pretty much what Bruce was saying. You want a wide 'drag bucket' that gives you low drag at a range of CL's.

Use thinnest section which is strong enough
all the camber and washout really means nothing on this type model
it's- just -too -small
Wing loading is EVERYTHING
All the fiddling with sections and twists is just an attempt to fix overweight conditions
Build more - theorize less - you will learn more.
Not trying to minimize others opinions - but having built hundreds of different setups - the only real fix I have found ,is to build as light and strong as possible . Theairfoil shape stuff including sharp vs round LE- simply of little or no actual value
fudging the planform to increae tip chord IS of value

Thanks..I like that idea....I have done ,wash-out, that way..I dont want to much neg. pitch.moment..

I tried cambered airfoils-{1-2%}- in the simulator. ,,on jets only.. I can feel the change alot. But they are slower.. 22 inch root,6 tip ,span 19 inches..1.4 Aspect...tip stall to death!!! lol.. I found on my F-22, planform, over rides, airfoil..Like ,F-15..Reflex helps with C/G on this crazy planform.. I have had 3 YELLOW AIRCRAFT A-4.They use some kind of cambered airfoil,..Pulls great through high banked turns.. May go more span ,and less L/E sweep. Then, i will feel better about no camber.. Thanks for building tip..

Thanks for info. Can you show me a "WIDE" drag bucket airfoil or a pic.?? I never added camber and made less C/L..?? I did some crude test.. A.O.A ,adds C/L faster,per deg., than camber does. But camber stalled, slower and later. ?? Also, L/E radius. was super critical.. You can see how crazy this wing planform is from pic...Thanks for info. and time...

Yep . I cut new cores , with more span,less sweep and wider tip.... Im still not sure what to do yet.. Im sorry ,but i found the,little "magic" we use on the wings do help.. Fences,vortex generators, L/E RADIUS for sure. Crow also on many aircraft.. T-45 is a DEMON ,without these design patches.. what planform wings do you fly?? Thanks for info and time

More area and fences are GOOD, simple stuff on small wings which are required to work in a broad speed range -carring a sizable load

Found an airfoil that you can add camber and still has- 0- pich moment. Used 1.5 at root anr 2.5 at tip. 2 inch more span per side.