Elastic Launched Gliders B

prd06
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Re: Elastic Launched Gliders B

Postby prd06 » December 13th, 2018, 2:24 pm

Hi I'm having an issue with my glider transitioning from the launch to the glide.
The glider does not have flaps and is made entirely of balsa. It has dihedral in the wing and stabilizer (no rudder/fin) When I just threw it, it glided pretty smoothly and was turning, but in the launch, it went straight up, then the glider suddenly pitched down and nose-dived into the floor. Does anyone know what is causing this? Do I need to launch it a certain way, or change the wing incidence, or change the surface area of the wing?

Thanks.

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Re: Elastic Launched Gliders B

Postby bjt4888 » December 13th, 2018, 3:14 pm

Prd06,

Why no fin? The fin provides an important element of yaw stability that balances the wing dihedral lateral area.

What is the current incidence setting of the wing and stabilizer?

What is the current center of gravity location?

If you provide more details about your airplane design and specifications, I can give better feedback.

Two launch angles are critical; the inclination angle and the bank angle. Usually, a glider that is designed to turn in right circles needs to be banked to the right anywhere between 5 and maybe 30 degrees. Start with low power launches with moderate (maybe 30 degrees) inclination angle and maybe 5 degrees of bank. Starting this way should allow you to evaluate the first flight and determine if more or less bank is needed. More is needed if the airplane noses up into a stall and dives to the floor. Less is needed of the glider hooks hard to the right.

Once you have determined a pretty good bank angle, add more power and increase inclination angle to maybe 35 degrees or 40 degrees. As power is added, slight changes to bank angle might be necessary.

Add more power gradually. Our first flights transition at about 10 ft. Second flights maybe 15 ft. 3rd flight 20 ft. Etc. till your at just below the ceiling.

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IvanGe
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Re: Elastic Launched Gliders B

Postby IvanGe » December 15th, 2018, 8:08 pm

I was testing my gliders in the gym today and it was getting launched and then semi-nosediving for around 5-6 feet before transitioning into a glide. However, once it starts gliding it glides nicely and it doesn't dip or stall. I wonder if it is the degree of the angle that I am launching it at or if the center of gravity is too forward. The other thing I was thinking about was moving the vertical stabilizer to a less of an angle. Anyone have any suggestions?
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Re: Elastic Launched Gliders B

Postby bjt4888 » December 16th, 2018, 5:56 am

Ivan,

What is the inclination angle and bank angle of your launch? By “nose diving” are you referring to a sharp hooking at the top of the climb that results in loss of altitude? If so, reduce the bank angle by a few degrees. Make this change gradually as inadequate bank can result in a hard stall and straight in nose dive to the floor.

More details about your glider and your launch would allow me to give better advice.

Brian T

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Re: Elastic Launched Gliders B

Postby BilalHayat19 » December 17th, 2018, 2:38 pm

Does anybody know what materials work best besides wood for building gliders?

And how to use it while building. For example, things I could use that works best for the wing maybe.

there are a few of them but I don't know which one works best. (wood, foam ,paper , plastic film , carbon fiber, tape, thread, and/ or glue.

At an invitational, Kellenburg memorial HS, I saw one team used wood and something else but didn't know what it was.

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isotelus
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Re: Elastic Launched Gliders B

Postby isotelus » December 17th, 2018, 3:41 pm

Hey there, wood is often the main part of building gliders and other balsa/bass wood events, but you can use the other materials listed in the rules manual. Several kits utilize this; I think the Protege has a carbon fiber fuselage (for strength and to be light), and you can use foam, glue, etc. In theory, you could even make a paper airplane, though that probably wouldn't work out too well. Honestly, whatever design you use will have different specifications. For your wing example, you would want to use A grain balsa wood for flexible wings and C grain for more stiff winged designs. You can also attach light materials to increase surface area. Good luck!
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Re: Elastic Launched Gliders B

Postby bjt4888 » December 17th, 2018, 4:07 pm

Billable,

If you are new to this event, I would strongly recommend the Freedom Flight or J&H Aerospace kits. The other companies making kits may be quite good as well, but I don’t have direct experience with them.

ELG May look simpler than Wright Stuff, but it is actually more difficult. Many elements of a successful design are critical, and they may not appear to be so. Wood density and stiffness, different for each critical part, is critical. Alignment of flying surfaces to a high tolerance is critical and overall weight is critical (there is a linear relationship between weight and flight duration). All of these critical elements are taken care of for you in a high quality kit.

If you should try to design on your own, it would be a very good idea to base any design on a close copy of an already successful airplane (ex. Time Machine, Feathershooter, WIF7, etc.).

Balsa of very high quality can be used for all parts of a glider as heavy as 3.5 grams. Foam is ok for flaps if you can’t get balsa of the correct quality. A thread of 1k carbon tow attached to each side of the fuselage may be necessary to strengthen lightweight fuselage wood.

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builderguy135
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Re: Elastic Launched Gliders B

Postby builderguy135 » December 17th, 2018, 6:16 pm

We used only wood for our design. I'm not saying that other materials aren't useful (they definitely are) but the quality of the design, to me, is most important. The plane I flew with had many dents and cracks on the wing (and a broken fuse lol) from improper handling but it still flies very consistently and relatively well.

(Also, you should try to avoid creating a new topic for every response. Try responding on a thread instead, thanks)
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Re: Elastic Launched Gliders B

Postby ZongleYang » December 18th, 2018, 10:29 am

bilal instead of wood, you can use foam for building some gliders but it may not fly well.

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Re: Elastic Launched Gliders B

Postby builderguy135 » December 18th, 2018, 2:40 pm

bilal instead of wood, you can use foam for building some gliders but it may not fly well.
There is nothing wrong with building with foam... :?:
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