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Old Feb 22, 2010, 03:00 PM
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G Norsworthy's Avatar
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XC#9 in a series, Giant Supra and other possible wings

This thread will cover the design and construction of the next XC design being tossed around. Fuse and tail will be more or less the same as #8 but the wing will be an attempt to improve on the blown up XCBD by either changing the airfoils or going to a cambered wing. At least two planes have been committed to foam and at least one more will follow depending on results. The design process will go a step beyond the last one to include XFLR5 analysis.
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Old Feb 23, 2010, 08:02 PM
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Old Feb 23, 2010, 08:03 PM
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We discussed a few designs including blowing up the Supra 1.25, 1.36, 1.36 with clipped tips, 1.36 with scaled down spans, and when the time came to order the cores, all the planets lined up and a phone call was made to Dr. Drela who provided the planform. Here are the results plotted out in XFLR5. I used LLT for the wing only, and used a Re for each individual airfoil from 50K to 1e6 in 50K steps. The comparison is with #8 which I am flying now. What I see from the graphs is that the giant Supra cambered up will outclimb the #8, which if true will be quite impressive based on experience. The speed setting appears to me only useful at really high speeds, and the cruise looks very nice over a wide range. I have a lot more to play around with but this is a good start.
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Old Feb 23, 2010, 08:10 PM
yyz
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This is using the Aegea sections? Can you share the range of AoAs you ran that suggests the climb rate will be better? Wing loading(s) for those runs?

I bet we'd all like to see the planform,

M
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Old Feb 23, 2010, 08:25 PM
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Sound like fun!
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Old Feb 23, 2010, 10:50 PM
Kurt Zimmerman ≡LSF 4461≡
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This sounds like it will be interesting...
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Old Feb 24, 2010, 02:43 PM
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The plane weight was 5kilos. Unless it is a light day with a low level inversion no point in flying lighter.

The AoA range was -2 to 7 degrees for the graph.

The airfoils are the AG40 series from the Supra. I'll work on the planform from a couple of hand sketches I have.
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Old Feb 24, 2010, 07:20 PM
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Planform

Here is the planform as drawn out and entered into XFLR5.
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Old Feb 25, 2010, 01:10 PM
yyz
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Quote:
Originally Posted by G Norsworthy View Post
Here is the planform as drawn out and entered into XFLR5.
12.75" root chord? Seems like you're back where you started? With all due respect, of course!

From recent experience, 10" chord on a 4 meter wing is difficult to see above 1,500 ft and I have good vision.

Mike
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Old Feb 25, 2010, 02:57 PM
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Similar but older plane

12.75 is reasonable. The E374 ship I took to 1780m has a 12" root. The generation of planes before I went back to poly were 12.75 root and were not really a visibility issue with black on bottom. They were all yellow with red trim on top and based on experience white with silver flash is better.

Here are polars for that generation plane along with #8 and the giant Supra design. The polars were generated according to how we flew the plane, not necessarily how it should have been flown, neutral for speed and about 3 degrees camber for float. The polars show #8 better at the speed end and the DS19/21 combo better for climbing. Experience tells me otherwise. There is more to the design than just the wing inputs. I am reasonably certain #8 is better on the float end also because of more accurate foam cutting, less distortion in bagging, cleaner tail design, and cleaner wing without hinges and exposed control rods.

The Supra still comes out on top. The advantage is a newer, more suitable airfoil choice and better planform. The challenge will be to preserve the clean airframe of #8 while adding the camber change to the wing. Even more so is to maintain the structural integrity of the wing with cutouts for the hinge lines and the servos. DS19/21 came apart in the air.
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Old Feb 25, 2010, 05:34 PM
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RDS - cleanup the surfaces - remove all possible drag and inefficient control mech.

[QUOTE=G Norsworthy; Even more so is to maintain the structural integrity of the wing with cutouts for the hinge lines and the servos. DS19/21 came apart in the air.[/QUOTE]

Greg - One consideration is RDS - This maintains the integrity of the airfoil X-section, basically eliminates the localized skin stresses. The new Antres 6.6M scale GPS race glider utilzes this method with Futaba 3150 servos. So the process exists for molded, however what is your thoughts on bagged wings with this design concept? Enough material and data already exists that would provide a cost effective implementation with little engineering required.
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Old Feb 25, 2010, 07:26 PM
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I'm all for RDS to hide the linkages. The other option is top drive which also cuts a hole in the foam and has a little bit of the linkage sticking out. The original Supra has RDS. The concern is the availability of high enough torque servos with matching RDS hardware, or homemade. Years ago the only servo I could find that would both fit and pull down the flaps was the red Multiplex digital slightly bigger than the old "standard". I'm sure there are more options available now. The flap servo cutout should be covered by a beefy spar at the root and the tip servo should be covered by the joiner rod.

The end customer of the first wing will have to decide the servo arrangement on the first wing but if I end up going this route with a second one it will be a 2011 plane and there is plenty of time to figure out how to do RDS.
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Old Feb 26, 2010, 11:25 AM
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Greg,

building rds equipment is pretty easy. I can help out with that if you need it. Keep it comming!

Aaron
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Old Feb 26, 2010, 12:41 PM
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+1 Go RDS
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Old Feb 26, 2010, 03:03 PM
Master of the Wind
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Poly Option

Here is a thinned and decambered wing based on the AG24 series. (not mine) Compared to #8 it appears to widen the range on the fast end without giving up anything on the thermal end. This looks appealing and would save the trouble of adding surfaces to the wing. This looks like a great choice on an active day when thermals are strong and high, and low drag at top speeds is an issue. The giant Supra will still climb through it, though there are days when this does not matter much. This wing is getting built so we will be able to see it in action. The structure will have to be modified a bit for the thinner section but it should still be fine. Lots of options here. It will be nice to compare some of these models in the coming year.
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