How much washout is built in to rv12 kits?
ZERO. Washout is not needed with a "square" wing planform.
Could you provide a little more justification for your statement please?
ZERO. Washout is not needed with a "square" wing planform.
He means, conveyed in a rather abrupt manner, that the stall progression in a rectangular wing platform travels from root to tip, leaving the aileron effective until the entire wing is fully stalled.
Other planforms, like tapered, the stall pattern is more evenly distributed, making the aileron ineffective at a lower alpha. Therefore, twist is used to delay the stall towards the tip, providing some control by the ailerons as the stall progresses.
Hope this helps.
He means, conveyed in a rather abrupt manner, that the stall progression in a rectangular wing platform travels from root to tip, leaving the aileron effective until the entire wing is fully stalled.
Other planforms, like tapered, the stall pattern is more evenly distributed, making the aileron ineffective at a lower alpha. Therefore, twist is used to delay the stall towards the tip, providing some control by the ailerons as the stall progresses.
Hope this helps.
Really?
Try rigging a cub wings without washout and then go stall it. Not a very pleasant experience.
Hi,
A rectangular wing does not need washout because it naturally stalls first at the inboard regions of the wing. Washout is added to some wings for two reasons. First is to achieve a more nearly elliptical lift distribution, which is more efficient. Second is to prevent the outer wing region from stalling first, which can lead to undesirable stall characteristics.......
ZERO. Washout is not needed with a "square" wing planform.
Swept wing stall progression starts at the tips, hence the pitch up and loss of aileron control.
I?ve got a bit over 13,000 hours in the 767/757, flew it yesterday stateside from Paris, but I?ve never stalled it, because I don?t trust aeronautical engineers. Flying is magic, and aerodynamic performance is largely derived by microscopic beings called ?Lifties?. They instinctively push on things...
Proving otherwise is impossible.
Yes, interesting case about Cubs. Champs and Citabrias too. Rectangular wings, yet they need some washout. I think the difference is that with the higher aspect ratio, any slight asymmetry can cause a lot of roll moment (wing drop) at stall. But one would think that the large ailerons would be very effective.
I don't think I fully understand why.
Very thoughtful and thorough explanation.
If you have ever looked at many Boeing wings, you will notice Krueger flaps on the inboard leading edge and traditional slats further outboard. This was one method of forcing the inboard section of the wing to stall first. When we were working on the 767, the wind tunnel tests were showing a pronounced pitch up moment at stall - which as Steve said - not desirable and in fact, not allowed. There was a lot of effort coming up with aerodynamic fixes for this issue - which turned out not to be an issue at all on the full scale airplane.
I didn't find the reply to be abrupt, just somewhat incomplete.
In my defense, the question was "How much washout is built into RV-12 kits?"
The first word, "ZERO", was a complete answer. The rest was additional.
Swept wing stall progression starts at the tips, hence the pitch up and loss of aileron control.
I?ve got a bit over 13,000 hours in the 767/757, flew it yesterday stateside from Paris, but I?ve never stalled it, because I don?t trust aeronautical engineers. Flying is magic, and aerodynamic performance is largely derived by microscopic beings called ?Lifties?. They instinctively push on things...
Proving otherwise is impossible.
?Lifties?, like any other living creature, are made of molecules. Is this what you are referencing?
What makes lifties decide what to push on, and how? Why don't they push on me while climbing a steep road on my bike? Or push on that big bale of hay my wife expects me to throw onto the back of the truck, which gets harder as you get older.
Clearly, the way to corral the lifties into doing what you want is to make something round on the front, sharp on the back, and blow wind over it.
if you ignore the initial buffet and keep pulling, the stall can propagate outboard quickly to where it envelopes much of the wing, and it generally doesn't do it symmetrically. The pilot had me stall from the back seat. Nice stall warning buffet, stop pulling, recover. Lovely. Then he said "do it again, but keep pulling". The sky disappeared and the canopy was filled with a nice clear view of the earth and a reflection of my eyeballs wide open. hmmm. I was glad he showed me that.
Interesting. A little knowledge can be a dangerous thing, eh?
How much increased performance was gained by being smarter than the designers of the airplane?
The above description is not typical of all RV's (even RV-4's)
There is a lot of variation from one to another because of many different factors (many of which are related to the fact that the airplanes are after all, amateur built.)
Since I am contemplating purchasing a kit, I?ve read the usual reviews, which cover stalls in varying detail, often disagreeing.
What is the progression of cues available as you approach imminent and then full stall?
Some say lightening of stick forces, tail buffet, little warning or plenty of warning. Yes, varying construction means varying characteristics, but what is the most common indicators, including for accelerated stalls under G, and flaps vs clean?
Are stall strips used on any of the RV series to help with warning? Is an AOA system worthwhile? I grew up using AOA, but flew airplanes with lots of buffet cue in all regimes.
Since I am contemplating purchasing a kit, I’ve read the usual reviews, which cover stalls in varying detail, often disagreeing.
What is the progression of cues available as you approach imminent and then full stall?
Some say lightening of stick forces, tail buffet, little warning or plenty of warning. Yes, varying construction means varying characteristics, but what is the most common indicators, including for accelerated stalls under G, and flaps vs clean?
Are stall strips used on any of the RV series to help with warning? Is an AOA system worthwhile? I grew up using AOA, but flew airplanes with lots of buffet cue in all regimes.
Since I am contemplating purchasing a kit, I?ve read the usual reviews, which cover stalls in varying detail, often disagreeing.
What is the progression of cues available as you approach imminent and then full stall?
Some say lightening of stick forces, tail buffet, little warning or plenty of warning. Yes, varying construction means varying characteristics, but what is the most common indicators, including for accelerated stalls under G, and flaps vs clean?
Are stall strips used on any of the RV series to help with warning? Is an AOA system worthwhile? I grew up using AOA, but flew airplanes with lots of buffet cue in all regimes.
I have found quite a variation between models and between different examples of the same model.
Start with the realization that the wing airfoil on the 3/4/6/7/8 is an NACA 23013.5, which has a notoriously terrible stall break. On a high-aspect ratio wing, this would create a very harsh stall. But with the low aspect ratio, rectangular wing, the stall progression outboard is slowed by the large downwash outboard, giving a seemingly gentler stall. For reasons I don't quite understand, accelerated stalls are harsher.
The RV-12 has an NACA 4-digit airfoil, which is noted for having a more gentle stall, with a smooth progression of separation from trailing edge fwd.
You designed the airfoil and with all of the RV-10's flying, no one has offered you a chance to fly one? With Van's is just up the road from you - that is just wrong.On the RV-10 and -14, the airfoil of which I designed, I worked pretty hard to try to get a more docile stall than the NACA 230xx, and I think I succeeded. Would love to get to fly one sometime.
The three has an airfoil unlike the 4,6,7 & 8.
Even though the -3 has a shorter chord than the 4, 6, 7, & 8, I'm pretty sure that the airfoil is the same.
With all of this talk about airfoils and stall characteristics - I hope our resident aerodynamicist can answer this.
I've noticed the RV-14 has blunt (divergent) trailing edges on the ailerons (and I assume the flaps). My very limited knowledge of the aerodynamics associated with this feature led me to believe the benefits in drag reduction were only apparent at higher mach numbers (like 0.5 and above).
Is there some other benefit besides drag reduction or was this done primarily to simplify the construction?
(Sorry, I know this was an RV-12 thread originally)
You designed the airfoil and with all of the RV-10's flying, no one has offered you a chance to fly one? With Van's is just up the road from you - that is just wrong.
Mark Cooper (VAF - "CharlieWaffles") has the nicest RV-10 I've seen and is near Portland. Maybe he will read this and offer to come fly with you
I have found quite a variation between models and between different examples of the same model.
My RV-8 has a complete mush stall. I can get the stick all the way back without the nose dropping. .[/B]