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Author Topic: Wings aspect ratio (slenderness)  (Read 3578 times)

Offline Matt Piatkowski

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Wings aspect ratio (slenderness)
« on: June 07, 2017, 05:53:54 AM »
Hello,
What wings aspect ratio (slenderness) is recommended for good stunt planes?
Thank you,
Matt

Offline Tim Wescott

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Re: Wings aspect ratio (slenderness)
« Reply #1 on: June 07, 2017, 08:10:59 AM »
I'm just quoting stuff I've read here plus a few years of observation.  5 to 5.5 seems to be what people are using.  You'll see anything from about 4.5 to 6.5 in published designs. 

Fat stubby wings seem to lose too much velocity in the corners; long skinny wings seem to be too sensitive to wind -- and, paradoxically, can be so efficient that they don't lose enough velocity in the corners, making planes "wind up".

Folks have experimented with high aspect ratio designs because of their cornering advantage, and always seem to come back down to the "normal" range.

You'll get other comments, I'm sure.
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Offline Randy Powell

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Re: Wings aspect ratio (slenderness)
« Reply #2 on: June 07, 2017, 01:56:15 PM »
Ah, yea, I got nothing.
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Offline Will Hinton

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Re: Wings aspect ratio (slenderness)
« Reply #3 on: June 07, 2017, 03:53:17 PM »
What Tim said.
John 5:24   www.fcmodelers.com

Dennis Leonhardi

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Re: Wings aspect ratio (slenderness)
« Reply #4 on: June 07, 2017, 04:24:27 PM »
No argument with above comments referring to "performance"; I personally feel lower aspect ratio wings tend to be more sturdy and less prone to warp ...  Life is often a series of compromises.   :)

Dennis

Offline M Spencer

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Re: Wings aspect ratio (slenderness)
« Reply #5 on: June 07, 2017, 11:48:49 PM »
think structurally , and arodynamically , you need ' horses for courses . Or theres the easy way , and theres the hard way . VD~

Certainly Wing Loading / Structurally - a ' mainstream model has evolved this way ( Er Modded Noblers !  %^@ )

HOWEVER , theres a clip on one of Windy's videos showing something like THIS performing the FULL SCHEDULE .

If it flys that well at that stage of development , obviously conventional ships will be obsolette in a few years .  LL~ S?P



Id just about got into a replacement 72 in. 8 : 1 Mewgull , as it was a hot groovey ship that handled the wind well . But Highly ?? unconventional,
Flaps maybe 1/3 span only . Plus coulda done with being lighter to get out past 5.0 Lap comfortably . which maybe got it out of the ' TENSION & STREERING '
parameters that were its forte . was 630 Sq In and 70 + Oz . So a ' Off run ' was an impairment .

I think a convention designs advantage is its less critical there , but most of that is Wing & Power Loading advantage .

The new smaller Mewgull with Full span Flaps , the drag further out turning is more susceptable to gust stability. Or Instability ! .

Long wings , 3/16 or 1/4 spars let in FLAT on the ARCH , Tapered from say 1/4 x 2 in at root to 1/8 x 1 in at tip , stop thw wings falling off .
But my opinion is the whole ship should be long and skinny ish , not just the wing . Look at a aerobatic GLIDER . full Size .

PLANK Fuselages , as in the current trend !  L O N G     -    D E E P  fuselages , seem to ' keep out there ' the best .Sometimes , maybe.

As T Tapered circular effort , its discernable the Flying surfaces , Do the Work . To rich - slow ( for manouvres ) it putters along gently
osccilating slightly . At under 6.0 / Lap , it ' Locks In ' as the air pressure generated ' glues ' it to the atmosphere .

This is one with a sharpish L E Tail Plane - Full sized said to give most accurate control , a knife edge responasive , tho ' locked in ' aeroplane,
generally unbothered by rough air - wind .

I think like Vehicals , its a mistake to do a ' sum of the parts '  type UNLESS its within existing perameters . Mid field Aeriodynamically .

Dunno if the yatsenko is as said , He measured most existing good ships , and did a ' Law of Averages ' on the ' Classic ' . ( first one .)

But for ' Outside the Norm ' , a think you need a theme / concept of useage . To get the perameters to cohere .

As in a Hillclimb sucker MUST steer under hard brakes , turn in , balance on the throttle , And Not be ' Hair Trigger ' - unless you want to visit the scenary .

Thous find you Altitude - density . Season - Climate .. and try for a ' cutting edge ' at one extreme . Or go for good midfield ( of use ) parameters .

But like ' theres no such thing at too much horsepower ' ,

USEABILITY - thuss not a critical set up , power train , or loading ,are going to make your life a lot easier .

Draggy things way out asideways from the fuselage are going to steer the tips , and likely the whole ship , if yr Not Carefull .

The BEAR .46 Trip is worth a look , on N-30 or Classic . The Original Treatesse , Via link there . After All Gieske wasnt to bad a Pilot .  S?P

Was a laser cut kit around for it at one stage .

http://stunthanger.com/smf/nostalgia-30/gieseke-nobler-46/

To make a long story short , the idea is , you put a . 60 in it .  ;D

Offline Chris Wilson

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Re: Wings aspect ratio (slenderness)
« Reply #6 on: June 09, 2017, 09:06:12 PM »
Tim, does this golden mean include any form of taper?
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Offline Tim Wescott

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Re: Wings aspect ratio (slenderness)
« Reply #7 on: June 10, 2017, 08:21:42 AM »
Tim, does this golden mean include any form of taper?

Yes, but keep in mind that I'm not an aerodynamicist -- just an experienced engineer who knows (from bitter experience) that straying too far from established practice without good reason is foolish more often than not.

Look at what's out there.  It's all tapered about the same.  Paul Walker, in his 1991 Impact build article, notes that flaps with a swept hinge line cause wierd yaw problems.  So does Howard Rush.  In fact, Howard has a very good rational for why combat planes have straight or nearly-straight leading edges with swept-forward trailing edges, yet stunt planes have swept leading and trailing edges -- it's because taper is good, and some overall forward sweep is good, but forward sweep on the flap hingeline is much worse than any goodness you get from the extra sweep of the flap trailing edge.

Go figure.  Life is full of mysterious compromises.  If you don't fly as well as Paul or Igor, and you're not willing to spend a LOT of time experimenting, you're probably best just following what the Big Guys do.  Blathering about it here, unless it's accompanied by shop and field time, is probably not the least bit productive.

In fact, my shop is calling me now...
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Online Brett Buck

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Re: Wings aspect ratio (slenderness)
« Reply #8 on: June 10, 2017, 05:46:56 PM »
Hello,
What wings aspect ratio (slenderness) is recommended for good stunt planes?
Thank you,
Matt

   You won't go too far wrong in the range of 5-5.5 to 1. It's a good compromise between induced drag, sensitivity to upsets/turbulence, and structural considerations. Much lower and you will demand vastly more power out of the engine. Much higher and you might get better performance in some cases, but you had darn better well be fully on top of you engine/prop/pipe combination to be able to dial in exactly the right propulsion response or you will wind up with big problems, particularly in the wind. If you were running electric, I think higher aspect ratio might be just what you want, both to save battery, and because the power is very tightly controlled.

  On the latter topic, just based on my observations, and in no way attempting to be negative - its pretty clear that you don't have a really good handle on making the engines work the way you want and/or need them to, so I would suggest that sticking to the middle of the range (and in fact, to established good designs like the SV-series, Trivial Pursuit, Impact) while you master engine development. Then, maybe it would be work considering alternatives and changes to those designs based on what you like or don't like about the way they work.

   All stunt design has to start with the engine (and or motor) first. The ideal airplane for an ST60 is definitely not the same as that for a OS40VF, and if you want to split hairs even further, the ideal airplane for a RO-Jett 61 BSE "Brett" version isn't the same as for a Stage III PA61. Neither are going to yield an airplane that is ideal for a "governor-style" motor setup , and that's different from a "feedback control" motor setup.

    Stuff like that is why people keep doing it for decades, but you would probably be best served starting with something that is known to work, so you can distinguish between design and trim/setup issues.  If your Impact/40VF doesn't work, it's probably not because the design is wrong or the engine is not good enough.

      Brett

Offline Mark Scarborough

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Re: Wings aspect ratio (slenderness)
« Reply #9 on: June 10, 2017, 11:28:14 PM »
Ah, yea, I got nothing.
Seriosyly Powell? come on,,
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Offline Randy Powell

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Re: Wings aspect ratio (slenderness)
« Reply #10 on: June 12, 2017, 02:51:51 PM »
Mark, I spent a lot of time with high AR planes. I don't build them any more.
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Offline M Spencer

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Re: Wings aspect ratio (slenderness)
« Reply #11 on: June 13, 2017, 12:10:23 AM »
http://www.control-line.org.au/content/dkd/clmodels/clstunt/art/beathtb.jpg[/img]





As Reginald Mitchell realised ! ' aerodynamic washout ' , so the Outer Wing is Still Flying , when your aiming to outurn the oposition , maintains the equilibrium .

Unfortunately , On High A/R wings ,, with full span flaps  , maybe the ' P ' factor , on tight turns , gets coplicated and involved reactions under certain conditions.
Which may be teminal .
However a 8 : 1 A/R can be highly satisfactory even in 20 Kt coastal breezes .With the poviso that a little wing rock is 12 in at the tips , not 6 . Thus this & other factors
grab your attenion initially . Untill your familiar with them . Im fairly certain a co ordinated rudder will resolve certain roll / yaw concerns .

Offline Matt Piatkowski

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Re: Wings aspect ratio (slenderness)
« Reply #12 on: June 13, 2017, 03:47:40 AM »
Hello,
Like always, I thank you all for your thoughts, suggestions and comments.
Slenderness range 5-5.5 goes to my little black book containing the data useful for stunt.
Regards,
Matt

Offline Chris Wilson

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Re: Wings aspect ratio (slenderness)
« Reply #13 on: June 13, 2017, 07:11:26 PM »
Are we now moving onto the AR of the tailplane?

(Just saying cause its a wing also.)
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 Nothing in life is so exhilarating as to be shot at without result.  It's not enough that we do our best; sometimes we have to do what's required

Offline M Spencer

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Re: Wings aspect ratio (slenderness)
« Reply #14 on: June 15, 2017, 10:19:46 PM »
Was going to put this on as a example of a highish A/R . But its 5.5 : 1 odd .  LL~



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