Elastic Launched Gliders B

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builderguy135
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Re: Elastic Launched Gliders B

Postby builderguy135 » January 8th, 2019, 4:20 pm

Nba2302 wrote:i am pretty angry that a team got their Glider stuck on the ceiling, and the proctors still counted the time. They got 24 seconds, and got first and i got second!


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Re: Elastic Launched Gliders B

Postby waffletree » January 8th, 2019, 4:49 pm

Nba2302 wrote:i am pretty angry that a team got their Glider stuck on the ceiling, and the proctors still counted the time. They got 24 seconds, and got first and i got second!

dang that sucks
so like it just hung onto the ceiling for a while then fell? and the proctors counted it!?
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Re: Elastic Launched Gliders B

Postby CrayolaCrayon » January 9th, 2019, 10:16 am

waffletree wrote:
Nba2302 wrote:i am pretty angry that a team got their Glider stuck on the ceiling, and the proctors still counted the time. They got 24 seconds, and got first and i got second!

dang that sucks
so like it just hung onto the ceiling for a while then fell? and the proctors counted it!?


That's odd.
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Re: Elastic Launched Gliders B

Postby Hartman » January 9th, 2019, 11:41 am

Nba2302 wrote:i am pretty angry that a team got their Glider stuck on the ceiling, and the proctors still counted the time. They got 24 seconds, and got first and i got second!

Wait...It got stuck...and came down...by itself? That's some insane luck, but I think that the rules say that if it's stopped before it hits the ground, like in a basketball hoop, the timer is stopped. Did you complain to the proctors?

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Re: Elastic Launched Gliders B

Postby builderguy135 » January 9th, 2019, 1:40 pm

CrayolaCrayon wrote:
waffletree wrote:
Nba2302 wrote:i am pretty angry that a team got their Glider stuck on the ceiling, and the proctors still counted the time. They got 24 seconds, and got first and i got second!

dang that sucks
so like it just hung onto the ceiling for a while then fell? and the proctors counted it!?


That's odd.


I've personally only had one or two planes that managed to get down by itself... and they were wright stuffs with moving propellers lol.
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Re: Elastic Launched Gliders B

Postby WMSSO2018-2019 » January 9th, 2019, 2:12 pm

I used one of the freedom flight model kits for my plane for the regional competitions. But i am running into the problem of when it gets up to the top ( or as high as it goes during that flight) it will go down about half the distance of the ceiling and to the floor and then it will start to do its circles. We have had some success with it. We have been getting a 14.2 time. We are happy with this score but we know that we can get a better time. We have tried pulling it back farther and closer. We have been also a justing the angle of the plane and its wings. The main question I am asking is how can i use the whole height of the the building i am launching in how do i get it to circle at the very top and slowly come down.

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Re: Elastic Launched Gliders B

Postby bjt4888 » January 9th, 2019, 2:34 pm

WMS,

Congratulations on building the excellent FF kit. If you can answer a few questions, I think I can help you.

1. What do your gliders weigh?
2. Do you have any shims between the stick that is the wing mount and the fuselage? If so, how thick are the shims and are they at the wing leading edge or trailing edge. The purpose of any shims would be to increase or decrease the wing incidence angle.
3. Measure the flap deflection(downward curve of the flaps) and let me know the measurement. Is the flap deflection even on both wings?
4. What is the location of the center of gravity on your airplanes (balance point; usually reported in inches or cm back from the wing leading edge.
5. Are there any warps or inaccuracies in the wing, stabilizer or fin?
6. Is the fuselage straight right to left?
7. What are your other current trim adjustments (measure and report)(ex. Stabilizer tilt, fin bent to the right, etc.).

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Re: Elastic Launched Gliders B

Postby coachchuckaahs » January 9th, 2019, 4:17 pm

WMS:

Brian's input is critically valuable, he has helped us immensely with his insights.

Following a few of his points, on the flap deflection you want to check the static deflection (how much is each flap deflected downward when unloaded), and the flap stiffness (using a gram scale, how much force does it take at the trailing edge of the flap to move it to straight (take out the deflection).

What is the ceiling height you are shooting to?

What is the launch angle and tilt angle?

On your description of flight, how is the plane losing altitude? Is it stalling at the top of the climb, dropping the nose and then picking up a glide, or is it "zooming" around the corner (to the right), and comes down at to steep an angle for the first few fee or more? This could be showing a need to adjust the tit of the wing during launch. If stalling, tilt more (to the right). If zooming around the corner, tilt less. If it is too sensitive (small tilt change results in change from stall to zoom), try reducing the launch angle.

And answer Brian's questions, he will likely have further inputs.

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Re: Elastic Launched Gliders B

Postby WMSSO2018-2019 » January 9th, 2019, 4:27 pm

I have built a freedom flight model airplane for this year's Regional airplane. I am having trouble though while flying it. It will go up to the top and then go about halfway down and then start doing it circles. How do I get my plane to start doing circles at the top of the building so that way I have more space and a longer flight time? We've tried pulling back the plane further and not so far . We also have tried tilting the wings to the right or to the left. We've had some success with a fight time of about 14.2. I have checked to make sure that each of the Wings weigh the same amount as well. We have put putty at the front a very small amount because it was stalling at first. But now it is fixed except for that it will go to the top of the ceiling go halfway down and then start doing circles.

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Re: Elastic Launched Gliders B

Postby bjt4888 » January 9th, 2019, 7:43 pm

WMS,

If you answer my questions and Coach Chucks questions very carefully, we can help you.

I can pretty much tell you that your glider is “hooking” at the top of the climb, but if you answer the questions, we can tell you why it is hooking and what to do to fix. Glider is a more complex event than Wright Stuff and very specific attention to details, alignment, stiffness of components, etc. is what Coach Chuck and I are ready to help you with.

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Re: Elastic Launched Gliders B

Postby WMSSO2018-2019 » January 9th, 2019, 8:23 pm

Thank you for getting back so quickly. Now I know alignment can play a big part. But every thing is symmetrical. Even before I glued the wings together I measured their weights to make sure that they were equal and they were. If hooking is the problem how can I solve it? Also before gluing I made sure that each Wing looks like a mirror image of itself. The ceiling height is around 25 to 30 ft. Our launch angle is 35°. Then we tilt our wings to the right at about a 35 to 40 degree angle. So when it gets to the top of the building, the plane will ree correct itself show it starts going to the left. But when it gets going towards left it starts to go downwards and then as it gets about 12 to 15 ft in the air it starts doing its perfect circles like it is supposed to. Thank you for your advice this will help us a great deal. What would you consider a good time.

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Re: Elastic Launched Gliders B

Postby bjt4888 » January 10th, 2019, 6:49 am

WMS,

You answered question 5 and 6 from my list above. Please answer the other questions and then I will be able to help.

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Re: Elastic Launched Gliders B

Postby Hartman » January 16th, 2019, 7:58 pm

To increase the height that my glider reaches, should I increase the pull-back, inclination angle up, or some combination of both? Also, I've been testing with more pull-back, and it seems that I need to move my bank angle to the right as I pull back more. Is this what some of you have been experiencing as well?

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Re: Elastic Launched Gliders B

Postby bjt4888 » January 16th, 2019, 8:40 pm

Hartman,

See reply #4 in this forum that I wrote in 2014 with regards to the relationship between bank, inclination and amount of elastic stretch:

http://www.hippocketaeronautics.com/hpa ... ic=16492.0

Good job posting a specific question on the wiki.

Brian T

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Re: Elastic Launched Gliders B

Postby bjt4888 » January 17th, 2019, 7:50 am

Hartman,

A little more info related to your question. You will see in the Hip Pocket Aero post in the link above that the best way to find the optimal bank angle, inclination angle and rubber stretch is to follow progressive steps in initial launches. If, after following this progressive approach, it appears that a moderate inclination angle and a safe and somewhat successful bank angle still do not produce a transition from climb to glide with zero loss of altitude, then you can decide to try steeper launch angles with the same bank angle as previous flights (if they are somewhat successful). Steep inclination angles can be a little risky as a “hammer head” stall (this is a term for an extreme stall), followed by a steep dive and crash is possible. When launching steeper, you’ll need to reduce rubber stretch somewhat as the distance to the ceiling is now shorter.

If you are flying a proven design, and it is built accurately (yes, at launch speed an unintended 1/32” of wing washin, or the same small amount of unintended twist in the stab, will cause poor flying), of proper stiffness and lightweight wood, should transition from a full power launch with a “flop to the side” combination of roll and yaw (look up these Aero terms if you don’t already know them), with zero loss of altitude. Proper stiffness of wood parts (very stiff fuselage, fin and stab, and reasonably stiff wing) and light weight (low 4 grams or better) are very important to achieve good transition.

Brian T


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