Minimum Washout?

What is the minimum washout people have flown? Has anyone run with zero washout?

the douglas DC-3 has no washout and also many older aircraft

a wing with no washout is faster but it will not stall from the root to the wingtip.

so you will not retain aileron control into the stall.

cub are great to fly in the slow end for stol performance
why would you give away safety and aileron control ? for little speed gain

want speed ? consider a lancair

I am not all that interested in top end speed. My objective is to see if I can reduce the stall speed not increase cruise speed.

Luscombe...........

A Luscombe Sedan has no washout, and in my humble opinion, should never be full stalled at less than 7000 feet, and then only if you are current on your spin recovery.

Mike in NC

For those who forgot this discussion, and those that didn't see it in the first place, Jerry Burr addresses the topic with literary flair. This is one of my favorite threads ever.
http://www.supercub.org/phpbb2/viewtopic.php?t=221&postdays=0&postorder=asc&start=0
SB

I ditto what stewartb said. Glad you found the post. I was about to start looking. Another reason I love this site. Posts don't disappear they just keep getting revived.

StewartB said:

For those who forgot this discussion, and those that didn't see it in the first place, Jerry Burr addresses the topic with literary flair. This is one of my favorite threads ever.
http://www.supercub.org/phpbb2/viewtopic.php?t=221&postdays=0&postorder=asc&start=0
SB

Click to expand...

Can this link contained above be made active? I get a redirect to the index page. I'd like to read the old thread.

gdafoe said:

Can this link contained above be made active? I get a redirect to the index page. I'd like to read the old thread.

Click to expand...

+1 to what gdafoe said. Plus I'm always enlightened by Jerry Burr's way of putting fairly complex technical discussions in a way that even I can begin to understand.

Thanks. cubscout

if you install the old super cub Biplane wings STC, it has you rig your main wings to zero wash.. weather or not the biplane wings are installed...

You should lower your stall speed as you reduce washout. If you add in some dihedral it should help with the stall making it a mush instead of sharp drop. No two aircraft aircraft are the same so proper testing a safe distance from the ground is recommended once you have taking washout out to correct any rigging issues as recommended by the book.;-)
DENNY

My experimental cub has zero washout, half dihedral and it fly. Never tried it with different rigging, so can't compare.

StewartB said:

For those who forgot this discussion, and those that didn't see it in the first place, Jerry Burr addresses the topic with literary flair. This is one of my favorite threads ever.
http://www.supercub.org/phpbb2/viewtopic.php?t=221&postdays=0&postorder=asc&start=0
SB

Click to expand...

+ 2 to having this link re-activated.
The link Tempdoug posted can't be the right link, as the quote posted above is from 2004, and the beginning of the thread tempdoug posted starts in 2006
Is there anyway to get the original thread back up? And why would a thread ever go away anyways? Why dispose of knowledge?

Reducing washout to zero slightly reduces stall speed and makes the plane far more subject to spinning.
Reducing the top wing to zero was one of the reasons there were so many stall-spin accidents with the biplane conversion.

I too, would like to see Jerry's thread bumped back to the top, or made a sticky.
Jery is not only articulate, he knows what he is doing, and why. And is generous in sharing his time and knowledge.

I to would love to see all of Jerry s Works as a Cub Guy he is the best and it is hard to dig out his work. Ron

Hi All I should have wrought that Jerry should put his wrights in a book about cubs and sell it and I would be his first sail. Ron

Why wouldn't zero washout with stall strips installed be the best solution?

remember some years back when the FAA was all upset about tundra tires washing out the tail in a stall & causing spins? turns out that it wasn't the tires at all.... it was wings out of rig. zero wash and "booster flap" & maybe other crazy stuff people were trying. all it really does is turn you into a test pilot

With less dihedral and wash out the ailerons are much more brisk in roll in and roll out as I will bet Olibuilt has a great flying airplane. I will bet that it won't stall with power on .Ron

stability and maneuverability are opposites. thats why a modern fighter can not be flown without computers making corrections 200 time per second... no human can react fast enough. dihedral is there to make the aircraft right itself, hands off, after a minor deviation... positive dynamic stability, it was required for type certification. wash is there to give the pilot a stall warning before he loses control. if a mechanic rigs a type certified aircraft in some way contrary to the manufacturer's instructions that would be a violation that can cost your license. and oh yea... it makes the aircraft more touchy to fly and yes, more dangerous.

I always was told the float guy took the washout out for increased lift?


Glenn

the basic angle of incidence for the wing is fixed by the attach fittings at the wing root. washing the wing "out" at the tip flattens the incidence at the tip, which decreases angle of attack and lift. it is the approved way to rig so that when the wing root area stalls, the outer wing still flies and lateral stability is still there. and, the ailerons still have some control. so ya, I suppose if you get rid of wash it would give a slight bit of increase in lift compared to what it would have if rigged per instructions. what happens then when you stall though is it all goes away at once with no warning... no lift, no stability, no aileron control. ya sure, maybe you can practice & be OK but when when it bites you is when you don't expect it... maybe a bit over gross, a bit steeper turn, a bit of wind shear, hot day, high altitude, whatever.... it will be the day you discover what an accelerated stall really is

other things guys did to boost low speed performance and get quicker take offs was to rig the flaps and ailerons slightly drooped from the fared position. that would get you off quick, improve slow flight, but costs in drag at cruise.

dihedral.... remember the 4 forces. lift is always vertical and opposite gravity. for a given wing size, more dihedral means fewer square feet of wing lifting. when the plane rolls though, the wing that moves down will produce more effective lift. the one that moves up produces less. that provides positive roll stability which means the aircraft will right itself after a disturbance.

there is pitch stability too.... down force on the tail, cg ahead of the center of lift, etc and in order for an aircraft to be certified it has to display this three axis stability. the rigging is a critical part of that design. the manufacturer defines the rigging procedure and alternate riggings are illegal and potentially fatal. and, there is no alternate wing rigging for a cub on floats

The elliptical wing of the Spitfire stalls evenly across the wingspan, the rectangular Super Cub will stall root to tip due to the effect of 3D flow on effective angle of attack. Not sure washout on a Super Cub of less than 2 degrees has that much effect on Clmax, but in any event robust aileron input near the stall will have more effect on reducing critical alpha due to camber, and creating asymmetric lift, than the washout effect.

robust aileron at stall on a miss-rigged aircraft might induce control reversal, especially on aircraft that don't have differential aileron (cub). proper wash on the cub is 2.5 degrees. Cl changes with pitch, ClMax is dependent on airfoil cross section & design, but ya, you right.... at maximum lift there is a couple degrees (alpha) where there is very little change in lift, so why chase it. moot point in any case for a certified aircraft... they only have one approved rig setting