You said "band aid" - is that a reference to Band Aid(R) adhesive bandages or to things like speakers, microphones, and auto-tuners? Or to really aid a band, like by adding a banjo?

Why would an airplane need adhesive bandages? Duct tape over Monokote works so much better!

Why would an airplane be in a band, unless the band's first name was Jefferson?

Andy

Not really an airplane but could be considered a Band Aid, was flown between set changes to keep the audience entertained. Can anyone guess the band who had a " Fly " tour at the turn of the century? Note no washout in the wings and the exceptionally light wing loading. Handled very poorly in wind.

That must be U2.

Here's another band aid.

Originally Posted by JimZinVT

That must be U2.

Here's another band aid.

Nope.

I guess I'm off by a decade or so anyway.

In whitewater kayaking this is what we call the spin cycle. And washout is the solution

Kayaker Stuck In River Rapid | Flippin' Out (0 min 31 sec)

To be honest I was hoping to have a conversation here about which types of models would be well suited to have washout incorporated and which it would not along with other means of designing a wing that would ensure that the inboard wing section would stall prior to the tips. I would also like to learn more about CG placement and how it influences a perceived tip stall.

Ok but you have to give us the answer to post #17's puzzle

The only plane I've had a tip stall problem with is an F20 PSS sloper. I believe it has an RG14 airfoil with no washout, minimal dihedral, 48" span and weighs about 45 oz. Pulling hard into a high speed "bank & yank" turn at an altitude of about 6' it snapped and hit the slope face hard. It's in the basement somewhere waiting to have the front 25% of the fuselage glassed back on

You got it Jim. I have a history of flying R/C blimps for the San Jose Sharks and the Golden State Warriors. Occasionally a different event such as a concert would come into town with a blimp and I would get hired for the location. These were fairly popular in the '90s and early 2000s. When the Dixie Chicks came into town I got the call. When looking the Blimp over it didn't take much time to come to the conclusion that it was unflyable as is. When I made that comment the production manager looked quite perplexed that I could come to that conclusion in just a few minutes but he then admitted that they had unsuccessfully tried four times. The problem was that they were running geared Astro Flight colbalt 25 motors but only feeding them through 6 cell nicad packs with Tamiya connectors. I told him I could fix it and have it ready to fly that night. I set it up to run 12 cells and changed everything over to Deans connectors with peak chargers. That night was the first successful flight. After the concert they made me an offer I could not refuse.


OK back to washout. Being that my main design efforts have been focused on pattern aircraft, I obviously do not want to use washout. However the requirement to have a well mannered predictable airplane remains. One thing that I have noticed is that when running an overly forward CG coupled with excessive elevator throw to compensate for the forward CG leads to the situation you describe with your F-5. Wing loading is obviously a factor as well.

Being an old pylon guy as well the accelerated stall issue has bitten there as well. Again forward CG and too much elevator throw was a factor. I have also started designing airfoils where the tip has the high point moved forward just a bit. On my latest pattern design the airfoil thickness % actually increases from root to tip. It looks correct as from mid span to tip the taper is a bit aggressive.

I guess my question here is: Are there other proven methods of eliminating tip stalls then adding washout?

Please remember that the main technical reason for using washout in full-size aircraft .... especially control-surface variable washout -- it to insure that all wing sections, root to tip, are at optimal AoA.

That noted, for practical purposes most RC models, especially powered ones, are not particularly efficient, so that leaves us with the tip stall issue, which is really a side benefit of washout. I mean low Re is inefficient to start with.

Sure Lee, I get that but what about a model that will have more adverse reactions to washout then benifits? Are there any proven replacements to washout that work just as well inverted as right side up?

Unless you are a glider guider or a speed guy, and just fly stuff under 100 pounds, The numbers and wind tunnel data are really of Little value
Simply building as light as practical is the best way to get improved performance and minimal stall issues

Very cool on the flying Fly! So you ended up on the Dixie Chicks tour payroll?

I'm not smart enough to talk intelligently about aerodynamics when there are bonafide experts in the room
But I enjoy learning about things like this that might improve my home brewed slope designs, so I'll stick around for the party.
I have read discussions of "aerodynamic washout" (different airfoils from root to tip) and "geometric washout" (wing twist). My uneducated guess is that twist may be the less efficient solution? We're taking an airfoil that works best at a certain AOA and using it at a different AOA? Then throw in inverted flight and it gets complicated.

Originally Posted by exf3bguy

Sure Lee, I get that but what about a model that will have more adverse reactions to washout then benifits? Are there any proven replacements to washout that work just as well inverted as right side up?

Getting back to the OP pics of raptor and airliner washout: most full-size aircraft are not designed for sustained inverted flight. I was told at Boeing that in fact their airliners could sustain inverted flight, but only in a glide since the engines would quickly become oil-starved. However that is not true for birds since their washout and camber is both actively and passively controlled (re: aeroelastic feathers and wing design). We know that raptors and crows for sure will flip into an inverted glide and vertically extend their claws as a combined threat and defensive move to counter normal attack from above. And I have seem my Budgie, when his hang glider is in tethered inverted flight (also on the Flying Carpet modified Rogallo) extend one wing -- while inverted -- to provide "glider" (non-flapping) lift negative to his inverted body but positive to the ground .... as well as flapping while inverted with the same vectored lift-thrust, neg. to him but positive to the ground.


So it seems likely that with modern 6-g AS including accelerometers (which I promise you birds have and which probably work better than our AS) it should be possible to have negative control-surface washout (i,.e., washIN) in appropriate situations, such as high-G/high AoA neg. maneuvers. That doesn't directly answer your question, except that washin is different from washout.

Else I go with Richard's above advice (only theoretically and from logic, since I have never flown Pattern).

I too agree with Richards logic of building as light as possible. That is pretty much a given as it is already quite a task to build a 70" WS, 1,300 sq in wing area, 78" length pattern airplane that falls within the 11 lb weight limit. That equates to about 19oz wing loading that does not account for fuselage lift ( a whole different conversation ). My goal is to end up with an airplane that still has a solid feel to it while flying through maneuvers at a
Relatively low airspeed.

Lots of useful info about washout in the following link:

http://modelaviation.com/washout

Summarizing:

All the good that washout does in upright flight can be detrimental in inverted flight -- such as loss of aileron effectiveness, non-uniform roll rate, adverse yaw, surprise snap rolls, and aileron reversal. For these reasons, washout is rarely used in aerobatic aircraft.
In addition, aerobatic aircraft need to be predictably snap-rolled.

Tapered wings need more washout in proportion to the amount of taper.

High wing loading requires more washout because it is prone to tip stalls.

High aspect ratio wings need more washout because their thin wingtips tend to stall.

Underpowered aircraft need more washout because they must fly at higher angles of attack.

Constant-chord wings, such as those found on the J-3 Cub or STOL (short takeoff and landing) aircraft, benefit least from washout.
They are built to maximize wing area and need all the lift they can get.
Instead of washout, they may use stall strips to soften the stall, and shaped wingtips to reduce wingtip vortices in lieu of washout.

Typically, biplanes have their wing incidences adjusted so that the forward wing (typically the top wing in a Stearman or the bottom wing in a Beech Staggerwing) will stall before the rear wing. The ailerons are usually in the rear wing so good aileron control is maintained even if the other wing is stalled.

LE slats can also prevent tip stalls, but slats are usually combined with washout for an extra margin of low-speed control.
Washout can be added after construction by slightly raising both ailerons.
This is recommended for the maiden flights of a new model.

Flaps increase the angle of attack of the wing in the flap area, so flaps also increase washout.

.