Larger inboard wing models?

[Avaiojet]

Some designs have done away with larger inboard wings.

Which CL model airplanes are still offered as kits, ARF's, ARC, with larger inboard wings?

I know the All American Senior is.

Thanks in advance.

CB

[PJ Rowland]

Nobler - all series that Im aware of.

[Clancy Arnold]

CB
Just about every Stunt model design uses that trick to help keep the wings straight in the turns.  The idea behind it is equalizing the lift on each wing panel by enlarging (lengthening) the inboard wing to make up for it's actual slower air speed.
Clancy

[Randy Powell]

My buddy Pat Johnston has designed many planes and believes in equal panel wings. Usually takes more tip weight, but his planes fly very well.

[Mark Scarborough]

all comments aobve are true,,
however it should be noted in all fairness that the assymetrical spans on todays airplanes are far less different than they used to be, or at least in my observation.
Normally now we see less than an inch, whereas it seems that older birds showed over an inch

[PJ Rowland]

5/8's - 3/4 is standard today.

[Chris Wilson]

Yeah it used to be an extra wing bay and that's probably 2".

Today its about half of that but mind you there is a school that believes in equal flap area regardless though so that you don't roll in maneuvers.

[Jim Thomerson]

Years ago there was a full page table in Stunt News of how much longer inside wing was needed with different spans, and whatever.  As I recall all the recommendations were well under one inch longer.  I design equal length wing airplanes and they fly to suit me. 

[Randy Powell]

And Paul Walker has used a larger outboard flaps on planes to allow him to carry more tip weight.

[Chris Wilson]

And Paul Walker has used a larger outboard flaps on planes to allow him to carry more tip weight.

How does that work out in the overheads?

[Brett Buck]

How does that work out in the overheads?

  Just like everyplace else in the pattern.

    Brett

[Bill Little]

Equal span wings (or very close to it) and a larger outboard flap really does work!  (I know most of you already knew that)

BIG Bear
RNMM/AMM

[Chris Wilson]

  Just like everyplace else in the pattern.

    Brett

Ok .......... let me be more acute then.

Tip weight always refers to gravitational forces which changes its orientation as it applies to the model during maneuvers.
Aerodynamic devices do not.

So if the model goes through a 90º change in gravitational orientation as in 'going overhead' the tip weight balances out nothing yet the compensatory larger flap still exists.

It would logically appear to cause the model to roll the more away from level flight it travels.

In other words if you change only one side of a balancing equation the result must differ as well.

How is that ever going to be a constant, or as you say "like everyplace else in the pattern?"

I am not looking for an argument mate, just a resolution.

Thanks.

[John Stiles]

Equal span wings (or very close to it) and a larger outboard flap really does work!  (I know most of you already knew that)

BIG Bear
RNMM/AMM

I didn't!

[Randy Cuberly]

Ok .......... let me be more acute then.

Tip weight always refers to gravitational forces which changes its orientation as it applies to the model during maneuvers.
Aerodynamic devices do not.

So if the model goes through a 90º change in gravitational orientation as in 'going overhead' the tip weight balances out nothing yet the compensatory larger flap still exists.

It would logically appear to cause the model to roll the more away from level flight it travels.

In other words if you change only one side of a balancing equation the result must differ as well.

How is that ever going to be a constant, or as you say "like everyplace else in the pattern?"

I am not looking for an argument mate, just a resolution.

Thanks.

Well, let's remember that tip weight does a little more than just balance the wing relative to gravitational forces.  It also moves the moment of inertia of the wing relative to the acceleration force of the engine.  As the airplane slows as in climbing the thrust of the engine is no longer steady state and the resulting accleration force will cause the heavier outboard wing to lag behind that accelleration causing a yaw to the outside.  This may be responsible for incerasing pull in overhead maneuvers.   Also in more verticle maneuvers the gravitational force on the lines is vectored very differently and is no longer trying to pull just the inboard wing down. If you doubt this launch your airplane directly tangent to the circle and watch the outboard wing swing back.  This is because without the drag of the lines which is a variable with speed the moment of inertia is located considerably outboard of the thrust of the engine so the wing pivots on that point.
I also have used a larger outboard flap for many years but believe that it helps because our modles fly in a slightly crabbed attitude relative to the airflow and that the fuselage effectively blanks a portion of the outboard flap and makes it less effective, while the fuselage tends to act as an airdam for the inboard flap actually making it more effective.
The end result of all this is that there are simply a lot more variables in your equation than you are considering for "balance".

Randy Cuberly

Edited to correct moment of inertia to be outboard of thrust line instead of inboard...sorry...it gets confusing without a sketch.

[Chris Wilson]

Thanks for the reply Randy, that is the kind of thing that I will have to read a few times over to digest it.

Much obliged.

[Randy Cuberly]

Thanks for the reply Randy, that is the kind of thing that I will have to read a few times over to digest it.

Much obliged.

Please note that I edited my text above to correct an error in the location of the moment of inertia.

Randy Cuberly

[Brett Buck]

Ok .......... let me be more acute then.

Tip weight always refers to gravitational forces which changes its orientation as it applies to the model during maneuvers.
Aerodynamic devices do not.

   No. Tip weight shifts the lateral CG.  It doesn't care about the orientation WRT to the local gravity, it cares about the load factor/acceleration/"G loading" The load factor in an overhead loop is not a lot different than one starting from level flight, as far as the airplane is concerned. So, say Paul added excess tipweight (which he would never do, of course). Doing an inside round loop from level flight, that would roll the airplane to the right in the airplane frame. The load at the bottom of the loop is about 4 Gs and the load at the top is something like 3.something Gs but in the same direction in the airplane frame. The airplane would be rolled "out" at the bottom AND the top, i.e. you would see the bottom of the wing all the way around the loop, you would never see the top. If you did an outside loop starting from level flight, you would see the top of the wing all the way around.

   The exact same thing would happen in overhead 8 loops - you would see the bottom of the wing all the way around the inside part. At the intersection, it would make an abrupt roll from one orientation to the other, and you would see that top of the wing all the way around. The size of the acceleration varies but the direction doesn't because the load factors even in round loops are much more than 1 G.

   If Paul then added some outboard flap to prevent the roll, it would correct it in overheads very similarly to low maneuvers.

   If I misunderstood your premise, I apologize, but I have been surprised at the number of people who misunderstand what the tip weight is doing and think that it always pulls the wing towards the ground.

    Brett

[Brett Buck]

Please note that I edited my text above to correct an error in the location of the moment of inertia.

Randy Cuberly

  I think you mean CG. Technically it also shifts principle moments of inertia because they are by definition centered on the CG but the effect is just a matter of the relative position of the CG and CP, and the change in the moment of inertia from any reasonable CG shift from tipweight is close to negligible.

    Brett

[Mark Scarborough]

Brett,
thanks for taking time to write that response, I kinda knew what I wanted to say with respect to this. I could see it  but I could not put it into meanigfull words.. YOur response made it perfectly clear,,,,,
Again, thanks for helping make it clear,,

[peabody]

Okay then....is it a "wive's tale", or do most of the winning designs from the west coast have some (I have been told 3/4") wing offset with the flaps of EQUAL area?
Thanks
 

[Serge_Krauss]

For those of you who hate math and anyone who practices that heresy, please travel at your own risk, but you might consider that I'm just going to give you a formula for approximating your wing offset, if you want to use offset. It involves multiplying, adding, and dividing. I do an example for you.

For a number of years, Martin Hepperle had a  simplified analysis of what he called the lift "eccentricity" across the wing of a control line aircraft. He used elementary calculus, but confined himself to rectangular wings with neither assumed tip losses nor twist. This eccentricity was the distance the center of pressure moves outward from the wing's center, due to increasing air speed outward along the span. He did this by dividing computed rolling moment by total lift. Intuitively I see this  as giving a larger eccentricity than would be true for tapered wings with tip losses. Nonetheless, his figures come out smaller than the usual old offsets. I suppose factoring in the line weight would enlarge the figure. Maybe including line weight and taper/tip loss effects would balance each other.

Unfortunately, while Martin's site still has many fascinating things for modelers, I can no longer find this and a related CL derivation there. However, FWIW, below is what I got from that site and my own similar derivation along the same lines. I did not try the derivation for tapered wings, but that shouldn't be really difficult. In fact, it might even be easier to just do it for an ellipse. If you know your line length and span, you can compute the approximate fuselage offset to have equal lift (really lifting moment about the fuselage) on both wings. For my planes, (.25 - .40 power, approx. 50" spans), offsets have usually been around .5" - .75", again not taking into effect the line weight nor the non-linear lift distribution, which would tend to counteract each other.

For instance if I had 60" lines, then l would be about 60' + 1.5' + 2' = 63.5' or about 762". For a 50"-span plane the eccentricity would be...

(50")²/(6 x 762" + 50^2//(2 x 762")) = 2500 in²/(4572" + 1.64") = 2500 in²/4574 in = .55".

So for this plane, you'd come close by moving the fuselage .55" or about 9/16" outward along the span.

Below is the "formula" as formerly derived on the Hepperle site.

[Randy Cuberly]

 I think you mean CG. Technically it also shifts principle moments of inertia because they are by definition centered on the CG but the effect is just a matter of the relative position of the CG and CP, and the change in the moment of inertia from any reasonable CG shift from tipweight is close to negligible.

    Brett

Brett,

PHHHTTTTTTTTT....

I'll stick by what I said!!!

Randy Cuberly

[Avaiojet]

Thanks guys,

All great information. I learned things I didn't know.

However, I was expecting the names of models. And if any have been reproduced with the inboard wing size change?

Or in other words, and just for the example, the Thunderbird "had" a larger inboard wing. Does the new kits of the Thunderbird, have a wing change or is it the same offering as when it was first designed and kitted.

I'm probably not explaining this correctly. 

Thanks,

CB

[Mark Scarborough]

Classic airplanes are built as designed so they were not changed
modern stunt ships are designed per the designers preference. There is no comprehensive list that I know of.
YOu need to research designs you like, or want to study, and see what the designer did and perhaps why

the information you have recieved in this thread is akin to the "why" portion,, I dont think you can get a list per'se' on which do and dont, to my knowledge it has not been compiled in that manner for that purpose,,

looks like a great way for you to spend your winter LOL

[Brett Buck]

Okay then....is it a "wive's tale", or do most of the winning designs from the west coast have some (I have been told 3/4") wing offset with the flaps of EQUAL area?
Thanks
 

Generally the Ted/Brett/David designs have a moderate offset (5/8-3/4) and a larger outboard flap, and I think at least the Impact and Bad News are similar. I have avoided equal-span wings because of the significant weight penalty, but as long as we put asymmetry in the wing but not the tail, we will tend to need larger outboard flaps.

    I don't think it make a huge difference which way you do it, within reason,  as long as you trim the airplane correctly otherwise. It will take much more tipweight to balance out equal span wings but more tipweight in and of itself does nothing useful (as long as you trim it to fly level all the time). You can balance out how much variation you get in the roll angle by altering the tipweight and flap area to whatever you want within reason. In many cases, that means letting it roll out a little on rounds and less or none on squares, which leads to more tipweight and more outboard flap. It's pretty rare to do it the opposite way (at least on purpose).

     Brett

[Bill Little]

Thanks guys,

All great information. I learned things I didn't know.

However, I was expecting the names of models. And if any have been reproduced with the inboard wing size change?

Or in other words, and just for the example, the Thunderbird "had" a larger inboard wing. Does the new kits of the Thunderbird, have a wing change or is it the same offering as when it was first designed and kitted.

I'm probably not explaining this correctly. 

Thanks,

CB

Hi Charles,

I think you will find that very few, if any, of the older designs are being changed since competition is a means for change.  On the TOP level, today's stunt planes are very good at what they are designed for.  No doubt the Thunder Gazer, Infinity, Paul Walker's new plane, are all better flying planes for what we do now.  None of the top guys are probably going to get out a Nobler kit and change all things to modern standards because there planes are already doing it, and they are bigger which some think presents better.

10 to 15 years ago, maybe more, Tom Dixon published the upright engine Thunderbird i Model Aviation.  He included all the modern mods as options.  So far I have only seen the one he did, no others.  Those planes do best in the Classic/Nos.30 classes where they cannot be changed in those ways.

It has been fairly well proven that a lot of asymmetry is not needed nor wanted in a modern CLPA nodel.

 BIG Bear
RNMM/AMM

[Chris Wilson]

  No. Tip weight shifts the lateral CG.  It doesn't care about the orientation WRT to the local gravity, it cares about the load factor/acceleration/"G loading" The load factor in an overhead loop is not a lot different than one starting from level flight, as far as the airplane is concerned. So, say Paul added excess tipweight (which he would never do, of course). Doing an inside round loop from level flight, that would roll the airplane to the right in the airplane frame. The load at the bottom of the loop is about 4 Gs and the load at the top is something like 3.something Gs but in the same direction in the airplane frame. The airplane would be rolled "out" at the bottom AND the top, i.e. you would see the bottom of the wing all the way around the loop, you would never see the top. If you did an outside loop starting from level flight, you would see the top of the wing all the way around.

   The exact same thing would happen in overhead 8 loops - you would see the bottom of the wing all the way around the inside part. At the intersection, it would make an abrupt roll from one orientation to the other, and you would see that top of the wing all the way around. The size of the acceleration varies but the direction doesn't because the load factors even in round loops are much more than 1 G.

   If Paul then added some outboard flap to prevent the roll, it would correct it in overheads very similarly to low maneuvers.

   If I misunderstood your premise, I apologize, but I have been surprised at the number of people who misunderstand what the tip weight is doing and think that it always pulls the wing towards the ground.

    Brett

Again, that is the kind of thing I will have to read twice over and the misunderstanding is mine not yours.

(Just when I thought I had it all figured out too!)

Thanks mate.

[Kim Mortimore]

So what I don't understand is, looking at Mike Scholtes' Brodak Original Nobler kit in the bare bones the other day, with the very asymmetrical wing panels and larger inboard flap......along with all those other very asymmetrical early designs.....did those guys routinely (and intentionally) get a very very very good view of the bottoms of their wings on insides and versey vicea on outsides?  Could they do eight-point snap rolls?  You can only reduce tip weight to zero (I know one guy who tried inboard tip weight in an attempt to stop rolling).  Or did they have some other way to prevent roll? 

[Brett Buck]

So what I don't understand is, looking at Mike Scholtes' Brodak Original Nobler kit in the bare bones the other day, with the very asymmetrical wing panels and larger inboard flap......along with all those other very asymmetrical early designs.....did those guys routinely (and intentionally) get a very very very good view of the bottoms of their wings on insides and versey vicea on outsides?  Could they do eight-point snap rolls?  You can only reduce tip weight to zero (I know one guy who tried inboard tip weight in an attempt to stop rolling).  Or did they have some other way to prevent roll? 

   No, that was what they did/do. Aldrich was trying to fly at 6+seconds a lap with a Fox so there had to be some way to get line tension.

     Brett

[PJ Rowland]

Thats exactly right.

They were flyign very slow, and not to concerned about having the model not roll, ultimate line tension was the key, we now do this with power.

Incidently - one of the things I did to help the roll on all of my high powered Noblers, was to run very little tip weight ( less that 5g ) and more recently Ive had brilliant success running 18tho lines.

[Howard Rush]

For those of you who hate math and anyone who practices that heresy, please travel at your own risk, but you might consider that I'm just going to give you a formula for approximating your wing offset, if you want to use offset. It involves multiplying, adding, and dividing. I do an example for you.

For a number of years, Martin Hepperle had a  simplified analysis of what he called the lift "eccentricity" across the wing of a control line aircraft. He used elementary calculus, but confined himself to rectangular wings with neither assumed tip losses nor twist. This eccentricity was the distance the center of pressure moves outward from the wing's center, due to increasing air speed outward along the span. He did this by dividing computed rolling moment by total lift. Intuitively I see this  as giving a larger eccentricity than would be true for tapered wings with tip losses. Nonetheless, his figures come out smaller than the usual old offsets. I suppose factoring in the line weight would enlarge the figure. Maybe including line weight and taper/tip loss effects would balance each other.

Unfortunately, while Martin's site still has many fascinating things for modelers, I can no longer find this and a related CL derivation there. However, FWIW, below is what I got from that site and my own similar derivation along the same lines. I did not try the derivation for tapered wings, but that shouldn't be really difficult. In fact, it might even be easier to just do it for an ellipse. If you know your line length and span, you can compute the approximate fuselage offset to have equal lift (really lifting moment about the fuselage) on both wings. For my planes, (.25 - .40 power, approx. 50" spans), offsets have usually been around .5" - .75", again not taking into effect the line weight nor the non-linear lift distribution, which would tend to counteract each other.

For instance if I had 60" lines, then l would be about 60' + 1.5' + 2' = 63.5' or about 762". For a 50"-span plane the eccentricity would be...

(50")²/(6 x 762" + 50^2//(2 x 762")) = 2500 in²/(4572" + 1.64") = 2500 in²/4574 in = .55".

So for this plane, you'd come close by moving the fuselage .55" or about 9/16" outward along the span.

Below is the "formula" as formerly derived on the Hepperle site.

I tried repeating this, but got it in a peculiar form.  If X1 is the distance from the center of the circle to the left tip, X2 is the distance from the center of the circle to the spanwise aerodynamic center, and X3 is the distance from the center of the circle to the right tip, X2 = 3/4 * (X3^4 - X1^4) / (X3^3 - X1^3) .  Then I beheld that b = X3 - X1, a = X2 - L, and L = (X3 + X1) / 2.  Then I gave up.  This is a good algebra exercise for Matt.  I can tell you how I got to where I did.  Mind you, this is from a person who as we speak is making bean soup, which took three pots before I got one the right capacity.  

I did this for combat planes, including taper, without fancy math by integrating 1/10" slices of span using Excel. You can do the same thing to calculate relative wing bending moment if you are sizing structure for something new based on something old.   Results can be surprising.   For example, Mr. Walker's 105-oz. B-17 has less wing root bending moment than an Impact.  

One really oughta consider spanwise wing loading when doing this ciphering.  I came close with the Son of Snort, but it still needed tip weight, to my disappointment.  I'll know how to do that pretty soon, because I'm learning it (42 years too late) for another project.  

[Howard Rush]

Brett,

PHHHTTTTTTTTT....

I'll stick by what I said!!!

I'll stick by what Brett said.

[Howard Rush]

Okay then....is it a "wive's tale", or do most of the winning designs from the west coast have some (I have been told 3/4") wing offset with the flaps of EQUAL area?

This gets into the esoteric realm of design parameters being functions of time.  To wit, I "design" by going to P. Walker's house and measuring things.  When I built my first Impact, he was flirting with equal flap tip chords, so I made mine equal for the next two airplanes.  Other parameters I measured on subsequent "design" expeditions didn't play with the obsolete and forgotten equal flap tip chord, requiring me to keep an eye on my plane at contests to prevent Brett from hacking off a good piece of left flap. 

[Randy Cuberly]

I'll stick by what Brett said.

I knew you would Howard...that just makes you both confused...You're both over simplifying the problem.

So Phhhhtttttt to you too 

Randy Cuberly

[Howard Rush]

I looked again, and I still don't get it.  Thrust (and lift) make moments about the cg, which tip weight moves to the right, increasing the moment arm.  Is that what you had in mind?   We are simplifying this relative to principal-axis stuff, the effect of which Brett says is too small to worry about, and I hope he's right.

"Phhhhtttttt" is in my cat's vocabulary, but he only uses it when addressing two critters: Jessica, the three-year-old up the street, and Lorenzo, a miniature Greyhound, possibly the craziest dog I've ever met.   

[Brett Buck]

I looked again, and I still don't get it.  Thrust (and lift) make moments about the cg, which tip weight moves to the right, increasing the moment arm.  Is that what you had in mind?   We are simplifying this relative to principal-axis stuff, the effect of which Brett says is too small to worry about, and I hope he's right.

     To be entirely clear, I think the shift from side to side of the principle axes 0.020" is a lot less of a problem (or, essentially, no problem) than the more straightforward shift of the CG by the same amount.  In terms of the mass properties the airplane doesn't care much if it rotates about an axes .010 to the right. It does care about the CG not being aligned with the CP - that's exactly the effect you are trying to create/correct. Since we know that you can casually observe a difference of a mere 3 grams of tipweight while sipping a Diet Squirt and talking to your buddies, that's only about .003" of CG shift. Proof is left to the reader about how much the overall Roll moment of inertia changes, pergentage-wise,  with 3 grams at 26", and it's small. It's a free body so it's far less than the parallel axis theorem would suggest and the r^2 from that is only 9x10^-6 in^2.   And, all it affects is how fast you respond to the CG shift, not how much torque the CG shift provides.

 I don't think the likely (but unknown) skew of the principle axes WRT the physical axes of symmetry of the airplane is negligible but that's really a different argument.

    Brett

[Randy Powell]

Amazing how many posts an off hand comment can generate.   

[John Stiles]

Amazing how many posts an off hand comment can generate.   

You thinks that's sump'm, try one a little off-color!

[Kim Mortimore]

   No, that was what they did/do. Aldrich was trying to fly at 6+seconds a lap with a Fox so there had to be some way to get line tension.

     Brett

Could inboard tip weight possibly be useful when trying to fly old, very asymmetric designs at modern lap times (if all outboard tip weight has been removed and roll continues), or is there some rule of fizziks that would make this unworkable?  Thanks for the input. 

[Brett Buck]

Could inboard tip weight possibly be useful when trying to fly old, very asymmetric designs at modern lap times (if all outboard tip weight has been removed and roll continues), or is there some rule of fizziks that would make this unworkable?  Thanks for the input. 

    In principle, the universe doesn't care where you put tip weight. The problem with this in the extreme cases (like the All-American) is that are other serious problems present as well, like the thrust line being well outboard of the CG even without weight on the inboard tip.

     Brett

[Randy Cuberly]

    To be entirely clear, I think the shift from side to side of the principle axes 0.020" is a lot less of a problem (or, essentially, no problem) than the more straightforward shift of the CG by the same amount.  In terms of the mass properties the airplane doesn't care much if it rotates about an axes .010 to the right. It does care about the CG not being aligned with the CP - that's exactly the effect you are trying to create/correct. Since we know that you can casually observe a difference of a mere 3 grams of tipweight while sipping a Diet Squirt and talking to your buddies, that's only about .003" of CG shift. Proof is left to the reader about how much the overall Roll moment of inertia changes, pergentage-wise,  with 3 grams at 26", and it's small. It's a free body so it's far less than the parallel axis theorem would suggest and the r^2 from that is only 9x10^-6 in^2.   And, all it affects is how fast you respond to the CG shift, not how much torque the CG shift provides.

 I don't think the likely (but unknown) skew of the principle axes WRT the physical axes of symmetry of the airplane is negligible but that's really a different argument.


    Brett

Brett,
Thanks, and I agree completely with what you've said but there are other considerations.  What about the variation in line drag with speed changes and their effect on accelleration and yaw with respect to the "CG" as a result of the moment relative to the tip weight?

This is in my opinion not a small variable.  Also the momentum of the lines is during accelleration changes between level and verticle flight is significant.

Randy Cuberly

[Larry Cunningham]

I seem to remember a post where the author was advocating a larger area on the OUTBOARD wing.. Do you remember?

Several larger top competition models have symmetrical wings. And in 1/2A stuff, I don't remember any concern for asymmetrical wings.. there may have been, I just don't remember it.

It could be a secret weapon.. Something like: greater tip weight to overcome the larger outboard wing lift => greater roll stability! Maybe we could finally get rid of that pesky wart on the outboard flap.

... yeh! That's it. ;->

L.

"My grandfather invented Cliff's Notes. It all started back in 1912...Well, to make a
long story short..." -Steven Wright

[Tim Wescott]

For instance if I had 60" lines, then l would be about 60' + 1.5' + 2' = 63.5' or about 762". For a 50"-span plane the eccentricity would be...

I absolutely positively don't remember where I saw it (it was probably in Paul Walker's 1991 "Impact" article or Bob Hunt's 1977 "Genesis" article, though, because I've re-read both of those recently.  Or maybe it was on line).  I also don't remember the exact wording.  But the argument about wing span offset boiled down to "longer wings on the inside are theoretically good, but the airplane 'crabs' a bit as it goes through the air, blanking the outer panel and making up the difference".

Maybe it was Mr. Walker, because that would also be an argument for longer outboard flaps.  (It would, for that matter, be an argument for not starting the flap until you're considerably outboard of the fuselage -- but then Mr. Rush would complain about turbulence being generated at the spot where the flap begins).

I got the same answer as you did going from first principals and assuming a rectangular wing (and also assuming no blanking of the outboard panel due to crabbing).  I didn't get nearly as elegant an expression for it as Mr. Hepperle did, however.

[Brett Buck]

Thanks, and I agree completely with what you've said but there are other considerations.  What about the variation in line drag with speed changes and their effect on accelleration and yaw with respect to the "CG" as a result of the moment relative to the tip weight?

This is in my opinion not a small variable.  Also the momentum of the lines is during accelleration changes between level and verticle flight is significant.

     
   No argument here - we were talking tipweght changes or asymmetry.  It just don't seem to have anything to do with the change in the moments of inertia or location of the principle axes.

   Brett

[Brett Buck]

Several larger top competition models have symmetrical wings.

<snip>

It could be a secret weapon.. Something like: greater tip weight to overcome the larger outboard wing lift => greater roll stability! Maybe we could finally get rid of that pesky wart on the outboard flap.

     I don't think there are a lot of current top designs that use equal-span wings - maybe Matt Neumann.

    I think this "less asymmetry so I can carry more tip weight" is a misunderstanding from something Al wrote long ago. Adding tip weight and changing nothing else always increases (the average) line tension. The reason it does is that it moves the lift vector towards the outside of the circle where it adds to the tension. This is the result of the roll torque it induces, which rolls the model away from you.

     All the monkeying with the asymmetry and flap tabs/flap differential does is change how it works from level flight to round maneuvers to square maneuvers. If you put in no asymmetry, or even more so, asymmetry the wrong way, but otherwise trim the airplane to fly level, the fact that it takes 3 oz instead of 3/4 oz *does nothing to add to the tension* aside from just being heavier. The more sophisticated trim people can play with this to allow a little roll in the rounds where it doesn't hurt the maneuvering very much, but none in the square corners, where it typically kills you. But to get more tension you have to give something up, that is living with more roll sometimes.

    So it makes little or no sense to "carry more tipweight" if you just turn around an negate the effects by altering the flap or asymmetry to keep it from rolling.

    Over small ranges it doesn't seem to make any significant difference to have small amounts of asymmetry or equal-span wings aside from having to put in a lot more tip weight on the equal spans. Whether it gives more or less line tension depends on the other trim goals.

     Brett

[Howard Rush]

..."longer wings on the inside are theoretically good, but the airplane 'crabs' a bit as it goes through the air, blanking the outer panel and making up the difference".

Maybe it was Mr. Walker, because that would also be an argument for longer outboard flaps. ...

I doubt it.  One thing I've noticed about Mr. Walker is that he does a lot of experimenting to understand the flight characteristics of an airplane, but then does not make up a theoretical explanation for it.  

[Larry Cunningham]

I seem to remember that ubiquitous and successful stunt model - Mike Pratt's SIG Magnum, had symmetrical wings. Am I wrong? I know it's not a tip top current competition design now, but the Magnum was quite a common winner back in the late 80s and early 90s. Many were restyled slightly and called Mustangs or even custom names..

Are all the Randy Smith models asymmetrical winged? I seem to remember the SV-11 foam wing I used in my Shogun being symmetrical. Probably it's old age creeping in, maybe I'm mis-remembering; it's quite easy to cut a bit off the outboard tip of a symmetrical foamie design.

There must be something to this asymmetry business - crabbing flight WRT the airflow, fuselage blanking the wing, CG being altered. Most of the classic designs seem to have it.

L.

"Nobody grows old merely by living a number of years. We grow old by deserting our
ideals. Years may wrinkle the skin, but to give up enthusiasm wrinkles the soul." -Samuel Ullman

[Brett Buck]

There must be something to this asymmetry business - crabbing flight WRT the airflow, fuselage blanking the wing, CG being altered. Most of the classic designs seem to have it.

   i am not sure what you mean by "crabbing sideways". Kit Noblers and Twisters do that but there's not much of it in any current competitive airplane - once again, the only competitive model I see doing that is Matt Neumann's but that's clearly his trim choice (create lots of line tension and live with the consequences). It doesn't have much to do with wing asymmetry or lack thereof. One year (2009?) it was so extreme he wouldn't fly level without Herculean effort with severe hunting. Most current airplanes have excellent yaw stability (mine probably at the top of the list) so they aren't going to be able to be flown at a severe angle.

     Moreover there's no reason to talk about "blanking out" parts (presumably, running in turbulence) because the taper in the wing has an effect that is indistinguishable from any sort of "blanking" effect. Whichever wing has the air hitting it straighter-on (at less angle to the relative wind) has both more lift and more drag which is both why you see tapered wings almost universally used because of the tendency to stabilize the yaw axis, and the reason you don't want it yawing around in the first place.

   All this is pretty far afield from the original question but it is interesting and important. The "symmetrical wing to I can carry more tipweight" theory is one my pet peeves, however.

     Brett

[Howard Rush]

I keep mentioning rolling moment due to sideslip, but I think folks prefer to think of the effect of air hitting their airplanes being the superposition of the effect of head-on flow and the effect of pure sideways flow.  Must be that "linear thinking" that New Age people complain about.