mazjag

Guys, I know that a lot of 3D planes have a tapered chord wing( caps, extras, sukhoi) ,but doesn`t that have a bad tendency to tip stall?? It seems when you pull back and get setup to hover a plane like that would be a handful.

My current 3D plane is an Addiction and it really doesn`t tip stall at all. I just bought an E-flite Su-26 and it has that same tapered wing and I`m thinking its gonna be prone to that as all the planes I fly on the SIM like that are hard to get to hover and tip stall pretty a good bit..BTW.. I know the Su-26 is not a 3D beast...any thoughts on the tip stall...thx..Jason

wind junkie

My Feedback: (1)

In general I think you're right. However much depends on the degree of taper, sweep direction and angle, the wing loading of the plane and thickness of the wing and bluntness of the LE. Also, vertical fuse areas (before and aft of CG) will affect willingness to snap or wing rock and will act differently inverted or upright.

Planes with constant cord wings aren't as fun to fly as ones which do snap easier. Design for aerobatics is always a compromise between many aspects which dictate handling qualities. If you prize stability over spin/snap type maneuvers, then you should keep flying constant cord thick wing planes which echo design trends pioneered by the fun fly planes of the early 90's.

Current trends for 3D prowess feature thinner wings with sharper LE and moderate sweep for a better balance and unstability when commanded.

I feel great planes are "just on the edge" of wing rocking, but will not wing rock in harrier at most alpha angles.

mazjag

Thanks,, I`m sure there is a compromise there for sure, because the Addiction is not a snap machine, but you can fly it a crawl and do tight turns no problem. I`ll keep it high when I attempt my first hover with the SU-29...

wallace.tharp

Re tip stall, Wind Junkie hit it pretty good in my view. My background is CFII full scale, 1100 hours taught & an Associates in Aviation Tech. No PHD or engineering degree to be sure, but the basics that CFIs are taught, pretty much out of the Private pilot handbook follow; hearshey-bar wing, no taper, are easy and cheap to build and have good general flight and stall characteristics. Tip stall comes into play whne one tip stalls before the other. This was very common in early RC and even full scale production of the P-39 for the U. S. Army. I had instructors that flew the P-39 that said they had to fly it coordinated, that is aleron and rudder right down to touchdown. Those who got slopy saw a wing drop a few feet above the ground and sometimes it resulted in hard landings or even damage. The idea is to get the wing to stall from the root near the fuse first and the progressively out to the tip. The idea her is you can still have good aleron control if the outer portion stalls last on both wings. All kinds of little tricks have been used to make this happen. A Beachcraft Bonanza had little half triangle strips about 3 feet out from the fuse on the leading edge to make for a sharper airfoil and earlier stalling portion of he wing. Washout is the next best thing. It involves having a warp in the tips & outer end of the wings that result in a lower angle of attack than the rest of the wing. Good RC technique on a first flight or triming flight is to stall the airplane with power on idle without using any rudder or aeleron and see if a wing drops. If it does and all is true and not warped, use rudder trim to make it stall without dropping a wing. Helps with landings too just like keeping the P-39 coordinated. Sideslip ok, skid not ok. My 3D is a PA Extra 260 I also have an Addiction. Hope this helps. wally.tharp

Jezmo

I am right in line with Wind Junkie. While my 50cc AeroWorks Extra 260 does not wing rock and just starts falling when stalled (also called an elevator because it appears to be falling pretty much straight down but still level in attitude). My little EFlite Extra sorta does the same but it does begin to wing rock just slightly after it settles in to the fall.

ircfly

In our models most of what is called a tip stall would be better called a yaw stall. The surface stalling is the fin/rudder. Often , particularly, a plane that wing rocks or has the yaw departure is easily fixed by by filling in a bit of the spot where the front of the fin meets the fuselage. On a 30cc plane such as my QQ yak 3 sq in worked very well. That completely made the wing rock stop and made harriers and elevators much solider as well as improving the hover. Snaps stopped a bit sooner needing held just a bit longer to stop at the same place.

Jezmo

Cool idea, gotta try that on my little Extra.

Bill Clark

what I have gathered so far is that tip stall or wing rock (if tip stall isallowed to continue) has as muchto do with wing loading as anything else, the lower the less.theAOA is also a big factor.as for wing taperone very well known 3d plane supplier (with well known designers behind him)mentioned that a tapered wing design is utilized when goodautorotation (i.e. spinning/snapping) characteristics are desired. this partial article http://pdf.aiaa.org/jaPreview/JA/2010/PVJA45719.pdfmentions thatthe wing rock phenomenon is believed to bea limit cycle oscillation (LCO) caused either by the loss of dynamic roll damping at high angles-of-attack or an aerodynamic hysteresis that generates the springlike forces required to drive the LCO. the article also discusses vertical fin size. personally Ilike to useside force generators (SFG's) tostraighten up a tip stall/ wing rocker or atleast improve the situation. I believe this is probabley from a combination of pressure entrapment or stopping span wise spill off at the tip. all 6 of my currently flying 3d planes use sfg's. My dad is a full scale (and newbie rc) pilot and he taught me that in a tip stall situation hardopposite rudder of the stalled wing will yaw the planespeeding up that wing toget it flying again. this works well as long as your fast enough to catch it

wallace.tharp

Good one Bill Clark and I think you are right on with the rudder correction. Old time flight instructors that taught on stuff like Sterman, Cubs etc., that were so called "rudder airplanes" meaning you could not do a coordinated turn, non slipping or skidding turns.....without coordinating rudder with aleron. Matter of fact, one of my first instructors would make me fly a full scale Aronca 7AC Champ with rudder only after triming it back and putting it in a nose high position with just enough power to not stall. You learn to correct all wing drops with heavy rudder correction in the opposite direction of the falling wing. Same technegue is used to pick up a wing in slow flight, MCA, if a wing starts to drop. wallace.tharp