Elastic Launched Gliders B

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Re: Elastic Launched Gliders B

Post by AdiMohapatra77 » January 31st, 2019, 2:16 pm

does anyone know how tall the gym for gliders will be at the Warrensburg invitational?

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Re: Elastic Launched Gliders B

Post by Tailsfan101 » February 7th, 2019, 8:56 am

Hi everyone, I just volunteered to take on this event yesterday for a Saturday invitational, and I'm not wanting to completely fail. Can anyone give me advice on the launch? I've already read the wiki page, but I'd like to know more. Thanks in advance!
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Re: Elastic Launched Gliders B

Post by builderguy135 » February 7th, 2019, 9:09 am

Tailsfan101 wrote:Hi everyone, I just volunteered to take on this event yesterday for a Saturday invitational, and I'm not wanting to completely fail. Can anyone give me advice on the launch? I've already read the wiki page, but I'd like to know more. Thanks in advance!
Launch it as high as possible and pray it transitions well.

Seriously though, practice launching the glider consistently until you find something that works. It's pretty easy to medal at most invitationals if you figure out how to launch consistently and adjust the CG correctly.
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Re: Elastic Launched Gliders B

Post by fifty_missions » February 8th, 2019, 1:07 pm

Here is a Reference for Trimming-

Flappers and Conventional Gliders

Note #1- When attaching Fin and Stabilizer, just use very little adhesive only at the leading edge and trailing edges. Leave the center open and unglued. This allows much easier removal to adjust such as adding stab tilt or increased rudder. Also, on the fin, glue the front half to the SIDE of the fuselage and this allows wedges aft to increase turn rate.
Note#2- The wing and stabilizer need to be 0-0 degrees or dead parallel to start. Possibly one degree positive on the wing, no more.
Note#3- Mounting the wing assembly on a hard balsa strip with extensions allows the assembly to be taped onto the fuselage and the CG shifted if necessary.
Note#4- Slightly nose high glide is most efficient with slower flight and reduced descending rate. The CG needs to go back around the 2/3's point on the wing towards the trailing edge and the trailing edges of the stab bent down to keep glider from stalling.

Trimming-
1) Hand-Launch Trim for slight Stall (porpoising) in the beginning. This means remove some clay if Glider dives.
2) Observe Left or right Orbit tendencies. Document. (Some add notations to top of wing with Sharpie Marker).
3) Bank the glider to do 1st rubber launch. Pick the line where the ceiling meets the wall as the aiming point.
4) Stretch 1/16' Rubber x 8" loop to about 60cm and release. Observe results. Document.

If Model does not TRANSITION and Dives, remove nose ballast until it stalls for transition.

When model Stalls (slightly) bend in DOWN Elevator (trailing edge od Stabilizer). With Forefinger and Thumb, pinch material to crush some of the air out then bend.
If model still Stalls... A) bend the elevator down another degree and/or B) Add a small amount of clay on the nose-no more that the size of a B-B.

6) If glider rolls severely, too much lift is being created by the opposite wing-
a) Use a Micrometer and using matching locations on both wings, confirm same thicknesses
b) On the wing that "drops" twist and even >crack< the wing so that the leading edge is 1-2 degrees higher. Glue to reinforce.
c) On the wing that drops, Lower the trailing edge slightly out near the tip. Use the same bend technique as described above.
d) Do the opposite on the opposite wing.
e) Other options... stab tilt and opposing rudder trim.

7) Orbit too Big-
a) On outboard wing, raise the leading edge up to induce more orbit.
b) Stab Tilt- The end that is higher is inboard on the turn rate. So if the port tip of the stabilizer is higher, glider will want to orbit to port (left).
c) Rudder Trim- Last Resort as the rudder has different effect with speed changes. Too much and the Glider will have a severe roll on launch.

8) Orbit too Small-
a) Raise the leading edge of the inboard wing a couple of degrees. See 6b above.
b) Add opposing rudder trim.

9) FLAPPER with Cracking Wings-
If the wings are cracking along the grain line, try this technique using old school model airplane cement (MAC) {DUCO or Ambroid not CA}
a) Glue the crack first and let dry 1 hour.
b) Under the wing at the wing root, apply MAC to 2/3's from the wing juncture to the trailing edge. Rub until dry and add camber as you go. Do both wings equally.
c) When the glue is dry, you can sand smooth.

10) Best sanding process-
a) One small sheet of 1/8" thk Birch Ply x 3" x 8"
b) Tropical Sun Fingernail Buffers... Black, Blue, and "Quads" (Blue, Pink. white and Gray)
c) Support part on ply with one hand, sand material with opposite. Roughing with Black, smoothing with Blue, Polishing with Quad

11) Gliders over 4 grams will need a shallower launch to transition. The turn rate is parabolic immediately after launch. Angle Launch to get higher transition. Lighter Gliders 3.5 to 4.0 grams can explore a more vertical launch and get a stall-into transition. This is where the gliders transition into slow speed immediately. Heavier gliders will take much longer to slow down which reduces flight time.

There is more when its needed... 25+ seconds under a 30' ceiling can be done.

Fly Right! 8-)
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Re: Elastic Launched Gliders B

Post by BigPhyungus » February 21st, 2019, 3:00 pm

Are gliders supposed to loop backwards and transition, or are they supposed to just transition down or does it depend on the design

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Re: Elastic Launched Gliders B

Post by fifty_missions » February 21st, 2019, 7:34 pm

It does depend not only on the design but on how carefully it was assembled. Due to the high speed launch, what may seem like a subtle bit a asymmetry as the glider was put together may have dramatic effects under high speed. EACH glider no matter how consistently reproduced will have its own unique flight characteristics. Therefore it is best to work with the variables and clues like an aerial Sherlock Holmes to unlock each mystery. Following this process scientifically yields the best results. I will caution that gliders designed as flappers can quickly exceed the design's speed in ;launch as well. This will cause some erratic launches and transitions.
Good Luck,
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Re: Elastic Launched Gliders B

Post by HMMian993 » February 26th, 2019, 2:24 pm

Sometimes my glider makes a constant arc shape while flying where it lightly goes down and then back up instead of flying stably, and I'm having problems troubleshooting it.
It's a homemade glider based on this one: http://www.amaflightschool.org/diy/how- ... e-olympiad

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Re: Elastic Launched Gliders B

Post by seadog » February 26th, 2019, 6:14 pm

HMMian993 wrote:Sometimes my glider makes a constant arc shape while flying where it lightly goes down and then back up instead of flying stably, and I'm having problems troubleshooting it.
It's a homemade glider based on this one: http://www.amaflightschool.org/diy/how- ... e-olympiad
Have you tried adding more clay to the nose? This is most likely a problem with the center of gravity of your glider. Look at fifty_missions' post for more detail.

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Re: Elastic Launched Gliders B

Post by AirplaneMan » March 3rd, 2019, 3:55 pm

Hi guys I made a flapper glider from the Freedom Flight kit and I'm having some problems with it.
It seems to be flying very very fast. I launched it and it flies pretty quickly to the ground even though it's ~3.75 grams. I launched it to about 15 feet and the flight was about 8 seconds. I noticed that at the top the glider simply turned and went into the glide, it didn't flip or anything (is it supposed to do that?)
Also, The turn circle is very tight (only maybe 10 feet) so it flies very quickly in tight circles down to the ground.
Finally, when I let it glide the glide is pretty smooth but there are some very small stalls, and towards the end there is a bigger stall.
What should I do to fix these things?
Thanks in advance.

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Re: Elastic Launched Gliders B

Post by bjt4888 » March 4th, 2019, 4:34 pm

Airplaneman,

10 ft turn circle is too small. 20 - 25 ft will give better duration. Turn circle is usually controlled by rudder offset and stabilizer tilt but can also be affected by uneven flap deflection, misaligned parts or warps in flying surfaces or the fuselage.

It sounds like your glider is stalling and may either need a wing incidence angle change or a CG change. Study the instructions carefully to be sure that the all trim settings and alignments are perfect and per plan.

If you can supply more details about your airplane and flight, I can give more specific help (ex. CG location, wing incidence, stabilizer tilt, rudder offset, flap curve/deflection, weight, launch inclination angle, launch bank angle, flight character).

Brian T

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