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Nov 13, 2003, 11:26 AM
Faster Faster!!
RCFlybry's Avatar

High Aspect Wing's What's your take on 'em?


After browsing through some of my uncles old plans from the early '70s I spied a few designs that really caught my eye.
After taking a closer look at these I began to notice that a lot of these designs have some really skinny wings with not much wing area. One was the Gypsy designed by Jack Headley. 64" in wingspan with only 250 sq" of wing area. It boasts an all up weight of 16 ounces which leads to a wing loading of around 9.20 ounces per sq". Seems a little high doesn't it? I found a number of others that were in the same range. According to Dave Thornburg High aspect ratios went up and down as if in some sort of fad. Here's a couple of pics of some that caught my eye.
What's your take on 'em? They're probably better suited for the slope.. but that's ok too.
The Kittiwake


And Here's the Gypsy



Bryan
Last edited by RCFlybry; Nov 13, 2003 at 11:28 AM.
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Nov 13, 2003, 03:54 PM
Hot Dawg Glider Pilot
schrederman's Avatar
Back in those dark ages we were just beginning to pay attention to Reynolds numbers, and so on. We were still trying to make everything look sort of scale-like. As we progressed through aerodynamics 101, wings got wider, airfoils changed, and wing loadings became more important. That's when we learned that everything's a trade-off. What you think you might gain with the high aspect ratio, you might lose with the low Rn. I always liked what my Magnum 12 looked like, but I think it would have flown better with a wider chord, longer tail moment, and a thinner airfoil...

Jack Headley's models were always a treat. I used to watch for his new designs in RCM.

Regards

Jack Womack
Nov 13, 2003, 06:01 PM
Registered User
viti's Avatar
i have no data to back me up but its been said that high aspect ratio wings are far better suited for high alt. and that there not suited well for low level [r/c ]flying,,,differant strokes for differant folks i guess

in the east we focus on handling at low level to able us to take better avantage of small weaker thermals,in the west they depend more on L/D for high wind big lift stuff

like shrederman said,,its always a trade off!

its obvious on paper what performs better but far harder to figure out WHAT is really needed

my 2 cents viti
Nov 13, 2003, 10:42 PM
ORGAN MOUNTAIN AIR FORCE
rloose's Avatar

Fly fast-Don't turn slow


The local sailplane guru took one look at my 96" Windex, and said "Tip stall waiting to happen". He was right. The high aspect ratio wing is prone to tip stall in a slow turn, so don't do it near the ground. They sure are beautiful when flying high and fast.

Rich
Last edited by rloose; Nov 14, 2003 at 10:16 AM.
Nov 14, 2003, 04:39 AM
Registered User
"An airplane is a set of compromises flying in formation."

Aspect ratio is one of many characteristics that must be harmonized with each other for best results. Some airfoils perform better at low reynolds numbers than others. The best low reynolds number airfoils work best with high aspect ratios and the other airfoil work best at lower aspect ratios. The design point is where the rate of profile drag increase with decreasing reynolds number equals the rate of induced drag decrease with increased aspect ratio.

There are many factors that affect tip stall in a turn in addition to aspect ratio. Among them are air speed, wing loading, angle of bank, sweep, twist and taper. With the right combination of air speed, wing loading, angle of bank, sweep, twist and taper a high aspect ratio wing can turn tightly without tip stalling.

If the wing span is held constant and the aspect ratio is varied, an optimum aspect ratio can be found. If the wing area is held constant and the aspect ratio is varied, then a different optimum aspect ratio may be found.

Choosing an appropriate aspect ratio depends very heavily on many, many other things, especially the purpose of the model.
Last edited by Ollie; Nov 14, 2003 at 04:47 AM.
Nov 14, 2003, 10:22 AM
ORGAN MOUNTAIN AIR FORCE
rloose's Avatar

Pilot's Skill


Ollie-

My guru friend was taking one other consideration into account- and that was my experience as an rc sailplane pilot. He had seen me tip stall a Thermalaire and a Spectra. As a newbie pilot, I was not planning ahead enough for my final approach, not paying enough attention to wind direction and the field layout, going too slow, and over controlling the plane. All issues that I am still working on.

Rich
Nov 14, 2003, 07:38 PM
Registered User
They're lovely....

Cheers,
Dave
Nov 14, 2003, 07:40 PM
Hot Dawg Glider Pilot
schrederman's Avatar
What's all that white stuff on the ground?

Jack Womack
Nov 14, 2003, 08:18 PM
Registered User
Jack,

With all the ski hills and snowmobile trails around here, they call it "white gold". And we'll be blessed (?) with 275+ inches of it before spring comes around again

Cheers,
Dave
Nov 14, 2003, 09:14 PM
Registered User
He's not kidding about the snow... I was stationed at K.I. Sawyer AFB just out of Marquette in the Upper Peninsula when I retired from the Air Force. The last winter I was there they recorded a total of 350 inches...not all at the same time, Thank GOD!
Nov 15, 2003, 07:57 PM
Registered User
In the 70s there was a guy who went over to r/c from c/l (Fast Richard? one of that group), and decided that a/r was missing on a hlg, so why not build a r/c sailplane on the same philosophy? Result was the LARS (low aspect ratio sailplane) and he reported that it gave away very little to the toothpick wings then in vogue. Better yet, it would turn on a dime and core thermals that were too small for the others. Center of Pressure travel seemed to be its problem, due to the huge chord. I'll look it up just out of curiosity...
Nov 15, 2003, 08:04 PM
Registered User
T. Lyttle.
Do you mean Dick Sarpolus? He published a LARS in Flying Models.
Nov 15, 2003, 08:14 PM
Hot Dawg Glider Pilot
schrederman's Avatar
From my limited experience, the best handling RES model I've ever flown is a 100" Legionair. It can core handlaunch thermals and ride them out, making these tiny little circles with the stick full back...it's incredible. Mine weighs 40 oz. (was 39 until I had some ouchies to fix) and has 935 sq.in. of wing area. The root chord is 10.5" and the tip chord is 7". I won several contests with one in the '70s and now have a scratch built one that is a winner as well. It has a pretty low aspect ratio, but it's more fun to fly than the Legionair 140 I have. It seems to be a good balance between high aspect ratio and Rn. It doesn't hurt that the airfoil is 7% thick, either... You can see it on the SKYBENCH AEROTECH website.

Regards

Jack Womack
Nov 15, 2003, 08:19 PM
Hot Dawg Glider Pilot
schrederman's Avatar
Oh by the way, that white stuff would be fun to visit, but I wouldn't want to shovel it! We have lots of heat here in Houston, but about 300 flyable days per year, the rest are just wet or windy...I've had 1 hour flights in January!

Come on down!

JW
Nov 17, 2003, 12:17 AM
Registered User
Yeah, Ollie, that's the guy; now I don't have to beat up my AAM and MB mags looking for it! Seems to me that "Fast Richard" and Dick Sarpolus were one and the same, could be wrong. I know that he was part of a group that got into everything, c/l, hlg, r/c, published lots of different designs. Still going to look the article up to see what the final analysis was; philosophy never caught on, don't know why other than the LARS just didn't look as graceful...


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