Elastic Launched Glider C

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schen
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Re: Elastic Launched Glider C

Post by schen » February 2nd, 2013, 12:22 pm

erikb wrote:
schen wrote:It's not a matter of the amount of pull on the rubber band or the amount of left roll. It "falls" into the glide because of the flaps.
Then how do solid winged gliders "fall" into their glide?

What the flaps do is change the wings shape to reduce lift in acceleration. If the wings did not flatten out, the gliders would loop back onto themselves.

Only after the glider has decelerated the flap changes the wing shape to provide more lift. The flap does not act as a brake. If the flap changes the wing shape before fully decelerated then you get those gliders that loop over at the very top and are upside down for a few feet before rolling over into the glide.

No matter what, the plane must decelerate first before transition into the glide. You have to get the glider in the right path with the enough deceleration that the inertia will be stopped, so the glider can transition into the glide at the slowest possible speed. Solid wing or flapped it makes no difference. You still have to have just enough energy to get it to the glide but, no more.

If not, you carry that inertia into the glide and if you have a "flapper" the flap will still be pushed up, the lift will be less and will not slow down and drop faster.

It's all in the launch, angles and energy placed into the glider.
I meant the way the glider looped into the glide. It's not because of how much energy is put into it. Some flapped gliders have a tendency to do that.

arooj1a2b3c
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Re: Elastic Launched Glider C

Post by arooj1a2b3c » February 2nd, 2013, 5:53 pm

I was wondering how effective it would be to add a piece of paper bent to a side on the vertical stabilizer to act as a rudder to generate turn instead of tilting the entire vertical stabilizer or horizontal stabilizer. I'm thinking about scaling a Simple Simon plane to make the wing length just under the limit. Also, what sort of an effect would adding straws to the bottom of wings have on the lift?

jander14indoor
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Re: Elastic Launched Glider C

Post by jander14indoor » February 3rd, 2013, 6:00 am

Horizontal Stab Tilt vs vertical rudder tab. Both are effective at inducing turn, problem is under what conditions and what's the drag penalty.
At slow speeds, turns out the horizontal stab tilt is more effective, while at high speeds the rudder tab is more effective, but also pretty draggy.
So, typically, if you are trying to control glide turn, horizontal stab tilt is most efficient. If you are trying to control climb turn (generally better controlled through tilt on launch) you would use rudder tab.
Typically.

Why do you want to add straws under the wing? What size and kind? I don't see much advantage, seems like it would just add drag. But maybe I'm not understanding why you want to do it.
I've scaled up the Simple Simon lengths and widths, kept thicknesses the same, with no problems. Plastic drinking type straws may not be legal the way I read the rules. Opinion only.

Jeff Anderson
Livonia, MI

fanjiatian
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Re: Elastic Launched Glider C

Post by fanjiatian » February 3rd, 2013, 6:11 am

Freedom Flights is taking a super long time to ship...
Anyone else experiencing the same problem?

erikb
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Re: Elastic Launched Glider C

Post by erikb » February 3rd, 2013, 10:29 am

schen wrote:I meant the way the glider looped into the glide. It's not because of how much energy is put into it. Some flapped gliders have a tendency to do that.
Sorry i miss understood you. In this case, yes it is the flaps that allow for the "bunt" launch.

However, you can also have a "bunt" launch without flaps. Only your glider is coming to the ground quickly because of the negative incidence in the wings.
--
Poudre High School, Fort Collins CO.

erikb
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Re: Elastic Launched Glider C

Post by erikb » February 3rd, 2013, 10:30 am

fanjiatian wrote:Freedom Flights is taking a super long time to ship...
Anyone else experiencing the same problem?

Contact Zeigler @ freedom flights directly and have your receipt. The same thing happened to us. He corrected the situation quickly
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Poudre High School, Fort Collins CO.

arooj1a2b3c
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Re: Elastic Launched Glider C

Post by arooj1a2b3c » February 3rd, 2013, 2:33 pm

jander14indoor wrote:Horizontal Stab Tilt vs vertical rudder tab. Both are effective at inducing turn, problem is under what conditions and what's the drag penalty.
At slow speeds, turns out the horizontal stab tilt is more effective, while at high speeds the rudder tab is more effective, but also pretty draggy.
So, typically, if you are trying to control glide turn, horizontal stab tilt is most efficient. If you are trying to control climb turn (generally better controlled through tilt on launch) you would use rudder tab.
Typically.

Why do you want to add straws under the wing? What size and kind? I don't see much advantage, seems like it would just add drag. But maybe I'm not understanding why you want to do it.
I've scaled up the Simple Simon lengths and widths, kept thicknesses the same, with no problems. Plastic drinking type straws may not be legal the way I read the rules. Opinion only.

Jeff Anderson
Livonia, MI
I just want to add segments of regular drinking straws spanning the wing's width glued under the wings in the center , as I heard it can increase lift because of something to with air concentrating under the wings; but I wasn't sure if the claim was valid.

Also a quick question about the vertical stabilizer on the Simple Simon: Is it supposed to be at the very end of the tail as in the plans or on top of the part of the tail directly above the horizontal stabilizer as in the photo so the segment of the tail at the very tip is left bare?
Last edited by arooj1a2b3c on February 4th, 2013, 12:48 pm, edited 1 time in total.

retired1
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Re: Elastic Launched Glider C

Post by retired1 » February 3rd, 2013, 2:57 pm

erikb wrote:
fanjiatian wrote:Freedom Flights is taking a super long time to ship...
Anyone else experiencing the same problem?

Contact Zeigler @ freedom flights directly and have your receipt. The same thing happened to us. He corrected the situation quickly
The late delivery of the rules did not help with a timely finishing of the design. His quality of product as well as having
both a B chopper and a C glider caused a large number of orders. His original balsa/laser vendor did not meet delivery times. Further the quality of the balsa declined. He has a new vendor but started out at over 200 glider kits in the hole.

The new vendor is making good progress, but it is a time consuming process, especially on the choppers.

Last I heard, he was about 2 weeks behind on orders , which are filled in the order received.

It is probably worth waiting for as his gliders are winning invitationals and the Montana Regional.

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Re: Elastic Launched Glider C

Post by _HenryHscioly_ » February 3rd, 2013, 4:30 pm

I received freedom flight kit just built 2 gliders.
Everything was good and I like the kit, except that one of the sheets had a split horizontal stabilizer, but that's ok since I will just trace the shape onto another sheet of balsa and cut it out.

"11/12/2012 - 21:08 Can the launch handle be like a cross-bow?
Yes, the launch handle can be any configuration desired, as long as energy to launch comes from elastic stored energy and the launch handle is safe."

If you were to stretch a rubber band(pulling from one end), but the other is not stationary(some resistance with an object), is the energy making object accelerate coming from elastic stored energy..?
I would think that, by pulling on one end, I store a tiny bit of energy, until the force of the rubber band is sufficient to overcome any resistance and being to accelerate the object. Then, afterwards, I am constantly charging the rubber band with elastic energy in order to keep accelerating the object....is this unsound logic/physics?

This is because my glider wouldn't detach itself from the rubber band; I'm not sure what was happening, I tried different angles and pulling back different lengths...but 9/10 launches would fail and the glider would get tangled.
It worked wen i pulled back by 1 foot, but it would only go about 10-15feet(1/2 of the gym) up.
Finally, after trying over 20 times with 3 gliders(2 broke) I got my last surviving glider to launch consistently(~50%). Holding the glider with my right hand and launch handle with my left hand, I would pull back about 1 foot, and then right when I let go of the glider, I whip my left hand up about 1 feet, and bring it down, following a curved path the entire time. This increased the average height I could get my glider to reach, maybe just more than 15feet?

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Re: Elastic Launched Glider C

Post by jander14indoor » February 3rd, 2013, 8:04 pm

As usual, only opinion, but...
_HenryHscioly_ wrote:<SNIP> "11/12/2012 - 21:08 Can the launch handle be like a cross-bow?
Yes, the launch handle can be any configuration desired, as long as energy to launch comes from elastic stored energy and the launch handle is safe."
<SNIP, not sure I understood what you were saying, but wanted to comment on the rest>
This is because my glider wouldn't detach itself from the rubber band; I'm not sure what was happening, <SNIP>
I whip my left hand up about 1 feet, and bring it down, following a curved path the entire time. This increased the average height I could get my glider to reach, maybe just more than 15feet?
If your glider isn't releasing easily, something is seriously wrong. That part of the launch just isn't that hard. What kind of launcher are you using? A loop on the end of a stick or something fancier? What kind of hook does your glider have? It only needs a pretty open/small hook. Not even really a hook, just a notch.

Something is really weird about only stretching one foot. To reduce the forces on your glider you should select an elastic that lets you stretch as as far as you can arrange. The energy to reach altitude is (simplified slightly as the force changes over the launch) equal to the distance stretched times the peak force. So you can get to the same place by a short stretch, but high force or long stretch but low force. Since these things are light, low force is good. Less stress on the glider.

Pushing your hand forward, be careful. That clarification is pretty clear all energy to launch must come from elastic stored energy. You are certainly adding energy with your hands above elastic stored energy with the launch you describe. Some event supervisors may call you on that. Again, opinion, not official.

Jeff Anderson
Livonia, MI

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