Elastic Launched Glider C

nikoruhe54
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Re: Elastic Launched Glider C

Postby nikoruhe54 » January 9th, 2013, 7:39 pm

I have a new question, will cambering the wings change the ballistic launch of the glider. At Northmont, I launched a flat wing in a "V" shape. It flies fairly decently but I recently have built a slightly cambered wing using the same techniques as my previous glider, and it just wants to nose dive. Any thoughts? Thanks

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Re: Elastic Launched Glider C

Postby Orange714 » January 9th, 2013, 8:03 pm

It says 35-40....but it's an outdoors glider which changes a lot of things.
I have a new question, will cambering the wings change the ballistic launch of the glider. At Northmont, I launched a flat wing in a "V" shape. It flies fairly decently but I recently have built a slightly cambered wing using the same techniques as my previous glider, and it just wants to nose dive. Any thoughts? Thanks
What kind of camber are you using? Under camber? Lower Camber? Upper camber? It might help to specify or show us the plan that you are using.

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Re: Elastic Launched Glider C

Postby jander14indoor » January 10th, 2013, 4:11 am

Changing almost anything on a glider will affect other trim settings,that's what makes them such an interesting device to use for learning data collection and analysis.

More specific to your case, changing camber will almost certainly change what the correct wing and stab incidence settings are. Possibly center of gravity.

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Re: Elastic Launched Glider C

Postby nikoruhe54 » January 10th, 2013, 11:04 am

Sorry, I should have been more specific, we don't build off published plans, but my camber is uniform throughout the wing. Meaning each half of the wing(the front and the back) is symmetrical. It is not a very large camber at all, maybe 1-2 degrees. I have made the stabilizer adjustable by inserting a piece of 1/32 under the front edge which allows me to adjust the angle of incidence by sanding this piece down or by adding paper to it. The other part I don't understand exactly is that my wings aren't warped, they were very straight. My main question is will the ballistic launch of a cambered glider look different than a flat wing because of the lesser amount of lift?

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Re: Elastic Launched Glider C

Postby jander14indoor » January 10th, 2013, 11:53 am

No issue if published plans or not.

First, lets be careful about what you mean by camber. Technically, ALL wings have camber.

Camber is just the mean line between the top and bottom surfaces of the wing. So for a flat wing, the camber line is just a line equi distant between the top and bottom. For a simple curved surface, equal thickness from front to back, the camber is still just the mid-line of the cross section. For fancier surfaces, you have to figure it out, but its still just the series of points marking the midpoint between the top and bottom surface of the wing.

Undercamber wings are ones who's camber is convex up. Note, this is NOT dictated by the shape of the bottom or top surface of the wing alone, it is that mid-line that determines. Most wings with flat bottoms and convex curved tops are in fact undercambered. Undercamber wings tend to have more lift for the same speed and angle of attack. More undercamber (to a point) more lift. They may have a better lift-drag ratio, and may be able to function at a higher angle of attack. It really depends on the detail at that point.

Camber amount is generally NOT measured in degrees, but by the ratio of the distance between the high point of the camber and a straight line between the leading and trailing edge and the distance between the leading and trailing edge.

OK, with all that as background and definition to commonize terms, I'm guessing you sanded the top surface of a flat wing so it's fatter in the center and thinner at the leading and trailing edge? If so, you have a mildly undercambered wing, and probably slightly better lift. That would tend to give more lift at the same launch speed, causing the loop/spiral to tighten up. Not a fundamental change to the launch dynamics, but depending on how close to the edge of one behavior or another in that general model it might look different.

You are doing the right thing in having an adjustable horizontal stab, you may also want to look at CG location as you've probably moved the center of lift too.

Jeff Anderson
Livonia, MI

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Re: Elastic Launched Glider C

Postby science8 » January 10th, 2013, 2:49 pm

I have a new question, will cambering the wings change the ballistic launch of the glider. At Northmont, I launched a flat wing in a "V" shape. It flies fairly decently but I recently have built a slightly cambered wing using the same techniques as my previous glider, and it just wants to nose dive. Any thoughts? Thanks
What place/time did you get at northmont?

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Re: Elastic Launched Glider C

Postby EastStroudsburg13 » January 13th, 2013, 1:22 pm

At the awards ceremony for Conestoga, they said that the winning time was 36 point something seconds.
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Re: Elastic Launched Glider C

Postby science8 » January 13th, 2013, 1:26 pm

At the awards ceremony for Conestoga, they said that the winning time was 36 point something seconds.
I believe it is with both flights together. So it was 2 18's i guess.

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Re: Elastic Launched Glider C

Postby nikoruhe54 » January 13th, 2013, 5:04 pm

I have a new question, will cambering the wings change the ballistic launch of the glider. At Northmont, I launched a flat wing in a "V" shape. It flies fairly decently but I recently have built a slightly cambered wing using the same techniques as my previous glider, and it just wants to nose dive. Any thoughts? Thanks
What place/time did you get at northmont?
I was forth place with flight times of about 10 seconds each. Wright State was similar, but I received 10th place as there were many more teams there.

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Re: Elastic Launched Glider C

Postby EastStroudsburg13 » January 13th, 2013, 7:00 pm

At the awards ceremony for Conestoga, they said that the winning time was 36 point something seconds.
I believe it is with both flights together. So it was 2 18's i guess.
Well, if I heard the words correctly, he said "flight time", so in reality it could be either one. I'd need confirmation from somebody from Conestoga to know for sure.

And the 36 point something was 36.74.
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