Elastic Launched Glider C

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chalker7
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Re: Elastic Launched Glider C

Post by chalker7 » November 15th, 2012, 7:58 pm

_HenryHscioly_ wrote:if fuselage has square cross section, which side, A or C grain, should face up?
I made my fuselage taller than wide, and put A grain on the side, just cuz it looked nice..

I got about 10 seconds on my glider.
My problem is, i have a really hard time transitioning.
I got it to work twice, at about 20degrees from vertical, 30degree left-bank.
If i get the degrees from vertical, off by a tiny bit, it doesnt work..
If too vertical, it kinda stalls, and nose-dives.
If too flat, it flys in an upside down parabola.
tried a total of about 20 times... 2/20.... :(

it's ~3grams, ~2" chord.
It has long tail-arm...tiny horizontal stabilizer...
um.,,12" moment, 1.5" x 1"
I was guessing it's because my stabilizer isnt big enough?
The A grain should be on the side, C grain on top (although it probably doesn't matter too much when the component is primarily under tension like the fuselage.)

The stabilizer size could certainly be the problem, it could also be a CG issue or even just a launch consistency issue. I'd make modifications to each of those (one at a time!) and record your results to see what works best.
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Re: Elastic Launched Glider C

Post by jander14indoor » November 15th, 2012, 8:23 pm

illusionist wrote:If I were to take the Simple Simon Plan (20cm wingspan), and enlarge it so that it has ~30cm wingspan, would I have to lengthen all the other measurements by the same percentage in order to maintain proper balance and flying characteristics?
As a starting point, yes, change all dimensions accordingly. Except, don't thicken the wing or tail pieces for this small a change. Personally I think the motor stick is too large (tall?) except you need to Make sure the tip is large enough to follow the rules. I'd also make the tip a little longer so you need less clay.

At least that's what I did and it seems to fly OK.

Jeff Anderson
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Re: Elastic Launched Glider C

Post by Orange714 » November 17th, 2012, 1:42 pm

I'm a little confused on the subject of incidence. I've read the article on AMA Gliders regarding this subject, but I'm still not sure on how to ensure that my incidence on my glider (Simple Simon) is correct. How would you get the angle of the wing and the horizontal stab to be "0-0." If anyone could help clarify for me it'd be much appreciated! Thanks!

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Re: Elastic Launched Glider C

Post by copyrightcat23 » November 17th, 2012, 7:03 pm

I'm currently having trouble with my glider.

For my wing and stab, I curved pieces of balsa by wetting them with water and banding them to a curved surface, letting them dry. However, I currently have the wing about two millimeters higher in the leading edge than the trailing edge and the stabilizer is close to horizontal, relative to the fueselage.

Without any ballast, the glider stalls immensely, so to correct the CoG, I added ballast to the front end of the fueselage. However, once an appropriate glide is achieved, if the glider is released pointed downwards, it will immediately nose-dive and crash. I thought the slight angle of attack in the wing would cause lift and pull the glider up, but it seems to not be "catching" any air.

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Re: Elastic Launched Glider C

Post by jander14indoor » November 17th, 2012, 8:56 pm

Orange714 wrote:I'm a little confused on the subject of incidence. I've read the article on AMA Gliders regarding this subject, but I'm still not sure on how to ensure that my incidence on my glider (Simple Simon) is correct. How would you get the angle of the wing and the horizontal stab to be "0-0." If anyone could help clarify for me it'd be much appreciated! Thanks!
Simplistically, for flat plate wing/stab like the the Simle Simon, this means they are in parallel planes. The design of the motor stick automatically gives you that if it is straight. Notice the wing is on the top and the stab is on the bottom of what started as parallel sides of the stick. the taper starts back of the wing and is on the top.

More completely, The incidence of an lifting surface is the angle between the chord line and some arbitrary reference on the airplane, typically a straight line from the front to the back of the fuselage. So setting the wing and stab 0-0 means the chord line of each is parallel to that reference line. Of course you need to know what a chord line is. It is NOT the bottom surface of the wing, or the line the wing might sit on. By definition, its from the center of curvature of the leading edge to the trailing edge. Careful, its locating that leading edge point right that tends to mess folks up. And can be hard to see on a model.

So, how do you set it for more complex design? Well, for existing designs, follow the designers instructions. They've probably built and flown it and found what works for that configuration. When you start going off on your own, keep the definition in mind as you draw a side view and use the recommendations from sites like AMA Gliders as a starting point.

Note, in almost all cases, its hard to build exactly what you mean to with balsa, thus the need for trimming!

Good luck, hope that helps.

Jeff Anderson
Livonia, MI

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Re: Elastic Launched Glider C

Post by chalker7 » November 18th, 2012, 12:25 pm

copyrightcat23 wrote:I'm currently having trouble with my glider.

For my wing and stab, I curved pieces of balsa by wetting them with water and banding them to a curved surface, letting them dry. However, I currently have the wing about two millimeters higher in the leading edge than the trailing edge and the stabilizer is close to horizontal, relative to the fueselage.

Without any ballast, the glider stalls immensely, so to correct the CoG, I added ballast to the front end of the fueselage. However, once an appropriate glide is achieved, if the glider is released pointed downwards, it will immediately nose-dive and crash. I thought the slight angle of attack in the wing would cause lift and pull the glider up, but it seems to not be "catching" any air.
I would start by simply using flat wood. Curving balsa with a wet technique is not effective in the long term (it almost always starting flattening out over time) and is very difficult to control accurately.

What you're seeing is the precarious level of stability that can result from having weird lift/drag/length ratios. What I mean by that is that you're probably getting quite a bit of both lift and drag off of your curved wing and don't have long enough of a fuselage to get a decent amount of recovery lift off the tail.

I'd suggest building a new glider following existing plans to get an understanding of the mechanics of gliders and building/trimming techniques. Once you get a good foothold, I'd then move on to your own designs. Lots of people are having luck with plans from http://amaglider.com/ in particular the Simple Simon plan.
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Re: Elastic Launched Glider C

Post by _HenryHscioly_ » November 18th, 2012, 8:36 pm

could someone explain how the transition works please?

i made my glider's vertical and horizontal stabilizer both for left turn
I am right-handed

i kept tryng to get my glider to transition with 30-60degrees right bank, and 50-80degrees from horizontal
didn't get it to work even once today

then tried 45degrees left bank, it was kinda awkward for my hands...BUT
2/4 tries transitioned, didnt time it, but maybe 10-15 seconds

i tried to stick to what I thought i learned online, but i guess my planes werent meant for right bank?

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Re: Elastic Launched Glider C

Post by hunterboy+ » November 19th, 2012, 11:26 am

Does anyone know how to make the glider spiral to the ground so you get a longer flight time? :D

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Re: Elastic Launched Glider C

Post by XXGeneration » November 19th, 2012, 2:34 pm

Try putting the wings off-center.

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Re: Elastic Launched Glider C

Post by Balsa Man » November 19th, 2012, 3:22 pm

Go back to the beginning of this thread, read through. There is both discussion of how, and links to more detailed info on how to do this.
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