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Old Jul 20, 2006, 12:13 AM
ASK
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Super Gee II continued (thread # 4)

Here is thread #4, continuing our collaboration in building and flying Dr. Mark Drela's SuperGee II DLG (discus launch glider).

To follow the discussion from the beginning, learn building and setup tips, and get a good introduction to the Super Gee II, see this and the previous threads:
SuperGee
SuperGee II (continued #2)
SuperGee II (continued #3)
What's a SuperGee II?
The SuperGee II is a discus launch glider designed by Dr. Mark Drela. The SG-II is best known for it's superb flying performance, extreme light weight, elegant and functional design, and enthusiastic community of home builders. Many modern discus launch gliders take inspiration from it's design. The typical competition-class DLG made today uses it's blended airfoil series or some variation thereof.













Mark has written extensive plans, most of which can be found at the Charles River Radio Controllers club website. Other information is available at the Yahoo SALGlider Group.

Builder's Guide
A group of interested builders are working on a step-by-step building guide for the Super Gee II. Steadily improving, you'll find the draft guide at this address
http://67.99.200.162/sg2_guide/welcome.htm

We are writing procedures for many of Mark's building methods, and when appropriate alternative methods. All contributors are welcome, and can write and provide photos in any format.

Notes
Thanks to Don Vetter and Jose Bruzual for the images of Mark and his latest SG-II. This plane was built by Aradhana Singh Khalsa and Fateh Singh Khalsa, and outfitted and prepared for flight by Mark. Different in some small ways from the plan spec SG-II, it has a one-piece wing made on white Spyder foam, plus the classic boom, pylons, tails, and control system. It also has a prototype of a new pod variation, adding a rear hatch and mounting inside the boom.
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Old Jul 21, 2006, 09:13 AM
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SGII evo program

I programmed my evo9 using M. Drela's program in the files section of the SAL yahoo group. What I can't determine by the program is how the 3-position J switch on the right side of the tx gives the 3 camber settings. Indeed, the program works and the camber is affected differently at each J-switch setting, but where in the program are the 3 settings listed?

I can find only one on the Aileron+ mixer which gives a symm. FLAP input into the mixer of 7%. Perhaps 7% is added with each click of the J switch?

Thanks,

Kevin Kuczek
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Old Jul 21, 2006, 09:47 AM
Flying IS the hobby
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On a side note, I am not sure if Mark has updated that file, but you should remove the aileron differential. It was discussed in one of the threads a while back, and Mark stressed it again on a clinic last weekend.
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Old Jul 21, 2006, 10:27 AM
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Quote:
Originally Posted by kkooch
I can find only one on the Aileron+ mixer which gives a symm. FLAP input into the mixer of 7%. Perhaps 7% is added with each click of the J switch?
The Flap control must be assigned to the J switch:
- Setup ("wrench") menu
- Assignment
- Controls
- Flap/RPM , set J, up-arrow

Also, you must turn off the Fixed-Value for the Flap control:
- Control ("stick") menu:
- Flap
- Fixed Value OFF (for all flight modes, perhaps changed with O switch or whatever)


Anytime you set up a new model on the Evo, you should always first turn OFF all the Fix.Val. settings for the Flap and Spoiler controls, for all flight modes. For some dumb reason these have nonzero default values, which cause all sorts apparently weird behavior and confusion for a new Evo user.
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Old Jul 21, 2006, 12:00 PM
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Quote:
Originally Posted by markdrela
The Flap control must be assigned to the J switch:
Yes, but how does the J-switch give 3 different camber positions per the program? Is it the 7% symm flap input to the Ail+ mixer and each position of the J-switch gives -7%, 0 and 7%?

thanks,

-KK
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Old Jul 21, 2006, 12:21 PM
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Quote:
Originally Posted by kkooch
Yes, but how does the J-switch give 3 different camber positions per the program? Is it the 7% symm flap input to the Ail+ mixer and each position of the J-switch gives -7%, 0 and 7%?
Yes.

If you want assymmetric throws, e.g. -7%, 0, +10%, then you must define the Flap input into the AILERON mixer to be assymetric.

Setup
Mixer Def.
AILERON
Flap ------- assym

That's what I use now.
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Old Jul 22, 2006, 08:03 AM
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Guys,

I am thinking of building a Super Gee IIusing 1.7 oz Kevlar for the wing instead of 1 oz. Do I need to put in the tip and aileron doublers and instead of triple layering the root, can I get away with only 2 layers of 1.7 at the root? If I did do the doublers, how bad would the weight penalty be? I am not planning on facing the ailerons at this time.

I will be using .060" rods instead of sparcaps and will build the wing like the Taboo.

Any suggestions/comments?

Frank
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Old Jul 22, 2006, 10:27 PM
ASK
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Quote:
Originally Posted by Fly2High
Guys,

I am thinking of building a Super Gee IIusing 1.7 oz Kevlar for the wing instead of 1 oz. Do I need to put in the tip and aileron doublers and instead of triple layering the root, can I get away with only 2 layers of 1.7 at the root? If I did do the doublers, how bad would the weight penalty be? I am not planning on facing the ailerons at this time.

I will be using .060" rods instead of sparcaps and will build the wing like the Taboo.

Any suggestions/comments?

Frank
Keep the tip doublers, keep two doublers at the root. If you use an SG-II wing joiner, you can probably come down to one doubler and skin at the center. We use two doublers T&B plus the skin, but want certain things to happen (and not happen) if the flyer noses it in hard. We omit the flaperon doubler, except for a little bit of glass at the root. Choices...

Frank, a little treat for you
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Old Jul 22, 2006, 10:56 PM
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Quote:
Originally Posted by ASK
Keep the tip doublers, keep two doublers at the root. If you use an SG-II wing joiner, you can probably come down to one doubler and skin at the center. We use two doublers T&B plus the skin, but want certain things to happen (and not happen) if the flyer noses it in hard. We omit the flaperon doubler, except for a little bit of glass at the root. Choices...

Frank, a little treat for you
What does such a wing weigh?
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Old Jul 22, 2006, 11:20 PM
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Quote:
Originally Posted by El Diablo
What does such a wing weigh?
The LightHawk wing above, just out of the bag, is basically an SG-II wing with similar variations to Frank's list and a vivid tip painting. It will finish out at 115-117 grams. The range for LightHawk wings in a few prototype variations has been 107 to 119, and production gliders will average around 115. A more typical home build would be 125-140 grams, depending on a number of variables including the amount of epoxy in the lay-up and how much the foam weighs.

Even at 140 grams bare weight, a well-built wing will fly very nicely. The SG-II design has weight concentrated inboard, making for low tip inertia / agile handling. The center doublers Frank is talking about are part of the solution that allows the servos to be inboard.
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Old Jul 23, 2006, 06:55 AM
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You Have Me Drooling With Desire!!! I Can't Wait For It To Arrive! Looks Fantastic!
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Old Jul 23, 2006, 02:15 PM
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Hi ASK,
I'm building a SG-II now, but I don't have 1 oz. Kevlar I have only 2 oz. Kevlar (unlimited supply, I work in a UAV factory so all the other stuff is no problem)....
What is proper wing layout you can suggest me?
thanks,
Eitan.
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Old Jul 23, 2006, 03:23 PM
ASK
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Espanola, NM USA
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Quote:
Originally Posted by eitanro
I'm building a SG-II now, but I don't have 1 oz. Kevlar I have only 2 oz. Kevlar (unlimited supply, I work in a UAV factory so all the other stuff is no problem)....
What is proper wing layout you can suggest me?
Eitan,
Let's go with the assumptions that this "2 oz." Kevlar isn't much different than Frank's 1.7 oz. (61 gr. sq meter). That means it has a similar balanced plain weave with a 34 by 34 yarn per inch count in Aramid 195 yarn.

Then I'd suggest you use the same layup as Frank (and our LightHawk).

If not, you'll either have to do the calculations on all the materials and their interactions, or rationalize based on existing designs.

That's one of the great gifts Dr. Drela gives us in the hobby. He's given us calculated and well-analyzed designs with material specifications and construction methods. If you are going to attempt design based on rationale and experience, his work makes a great place to start.

If the aramid you have is truly heavier than the 1.7 oz. / 61 gram material most commercial builders use, your wing will probably be heavier, with no escape I can see. I wouldn't recommend foam under 25 lb. density.

BTW, HL-60 foam will add another 12-14 grams to a SG-II planform and airfoil, as compared to 25 lb. foam. Mark combines HL-60 with 1 oz / 36 gram aramid to work his magic. The loose weave of 1 oz. is a pain to work with, hence most of the builders stay with the fully-filled weave in 1.7 oz..

Aradhana Singh
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Old Jul 23, 2006, 05:25 PM
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Supergee II Pod plug CNC file?

Before I attempt to rebuild the Supergee II pod in my 3D CAD tool (with all the attendant pain and gnashing of teeth), does anyone have this done already (and care to share it)? The end goal is to CNC mill a plug and make a mold.

Thanks.

73 John
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Old Jul 23, 2006, 05:29 PM
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I would be interested in the file also.

Scott
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