Elastic Launched Gliders B

bjt4888
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Re: Elastic Launched Gliders B

Postby bjt4888 » April 6th, 2019, 3:08 pm

AM,

Good luck. Be sure to note all the steps I suggested in the earlier post.

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Re: Elastic Launched Gliders B

Postby Pythagorean » April 9th, 2019, 12:13 pm

Hello all,

I am new to the forums, but not new to ELG.

So I am going to be flying at the OSU State tournament, where the air will be on. I have found modest success in our high school gym with the air on flying my FF glider at a low pitch (altitude) angle, somewhere between 20 and 25 degrees with a pullback of 55cm. My good flight times where 14.3-15.2 seconds. However, I will be flying against some of the best glider teams and would like some tips on what to do. Please note the air is flowing downward from circular vents and the flyable ceiling height is around 28 feet.

Also, another one of my FF gliders has a major roll issue. At low launch velocity (pullback of 30-40 cm) it banks left where it launches up moderately while rolling and turning around like the rudder/wing are creating to much roll to the left. However, at a higher launch velocity (45-50cm), the glider flies normally but then straightens out mid-flight. I pulled off my wing and its CG is slightly right of the pylon. I wonder if the CG of the wing is counteracting the rudder as the glider loses momentum. Any tips would be great, as I would like to change the CG to dead center over the pylon without reducing wing surface area and with minimal room for error (eg. minimal sanding or room for over/underestimating). I have re-glued my rudder at a less severe angle and will see how that affects flight when I get a chance. Upon further testing, I appeared to reach a "0" where the roll created by the rudder counteracted the CG difference of the wing. However, at the end of my flights, the glider would randomly swoop upwards into a stall, and then nosedive. This is a similar flight pattern to when I launch a glider without much roll, eg. no transition. Is it possible that my glider is "running out" of roll or cannot sustain itself in a circular flight pattern? Please note that this was observed at 35cm of draw length.

Thanks

P.S. I am using 1/16" rubber on a flat piece of 2"x4" softwood.

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Re: Elastic Launched Gliders B

Postby builderguy135 » April 19th, 2019, 3:48 pm

If my glider is flying kind of fast while hand gliding, is it right to increase flap deflection to try to increase lift with its speed?
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Re: Elastic Launched Gliders B

Postby bjt4888 » April 19th, 2019, 6:12 pm

Builder,

Flap deflection for the typical gym ceiling heights at SO competitions would typically be between 1/8” and 1/4”, depending upon flap size and stiffness. We usually use moderate size relatively soft flaps and start with 3/16” flap deflection for this year.

Best to test small differences in flap deflection by flying full flights and seeing what gives the longest flights.

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Re: Elastic Launched Gliders B

Postby builderguy135 » April 25th, 2019, 10:03 pm

What are some things i could do with a flapped foam glider in order to shoot it higher? (40 ft at nationals)
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Re: Elastic Launched Gliders B

Postby AirplaneMan » April 26th, 2019, 7:02 am

Hi everyone,

I've been building/testing the new glider that I made. This one is also from the FF kit, and it weighed 3.3g before adding clay. I then added clay to get the CG in the same place as what the instructions say, and now the glider weighs 3.6 grams. The decalage angle (wing incidence) is about .5 degrees. Flap deflection is a little over 3/16 inches.

I started by doing a hand toss, with the left wing a little lower than the right wing (glider turns in a left circle) and gently tossed the glider very slightly downward. It had a nice smooth glide.

I then launched the glider at about a 70 degree angle, and it started to roll because the right wing was creating too much lift. So then, like this video says, https://www.youtube.com/watch?v=MuNag5fH_EI&t=238, and what you all suggested, I cracked the left wing near the root and bent it up so it would create more lift. After I did that however, when I tested again, this time the glider was creating an insane amount of lift. When I launched it again at the 70 degree angle, it flipped upside down and lost most of it's altitude before landing safely.

So then I launched at a very shallow angle (10 degrees) and the glider had so much lift that it made it to the ceiling, but then it stalled the transition and again lost a lot of altitude. I even got rid of the incidence shim to get rid of some lift, but that didn't work either. I tested various bank angles and inclination angles but every time, the glider is stalling the transition. I am hesitant to add clay because it seems like the incidence is the problem, and I think it was bjt who said that extra clay with extra incidence on the glider isn't good.

Do I need up elevator? If not, how can I fix this?

Thanks,
AirplaneMan

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Re: Elastic Launched Gliders B

Postby coachchuckaahs » April 26th, 2019, 10:36 am

Extra clay up front, with extra incidence, will add to stability. You added additional incidence by breaking the wing, so you ether need to take out some overall incidence (shim the TE if removing LE shims is not enough), or add clay to nose.

Breaking the wing, as noted by Josh, is a very sensitive operation. Sounds like you added a LOT of one-sided incidence. You may have to take some of that out.

The entire trimming process needs to be completed again, as you have changed the incidence (apparently a lot) on one side.

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Re: Elastic Launched Gliders B

Postby builderguy135 » April 26th, 2019, 2:09 pm

builderguy135 wrote:What are some things i could do with a flapped foam glider in order to shoot it higher? (40 ft at nationals)


Also, what's the purpose of tip plates in addition to whole-wing dihedrals? Is it worth it to try out a plane (designed with tip plates) that doesn't have them?
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Re: Elastic Launched Gliders B

Postby coachchuckaahs » April 26th, 2019, 4:25 pm

Builder:

IN general, very high ceiling (Cat 3 and Cat 4) gliders tend to be non-flappers, as the flaps may keep you from getting high enough, If you are using the FFM, see Josh's review on YouTube. The Rhoacell is quite stiff, to the point of not being a true flapper.

Our first plane had rather stiff flaps with significant deflection. It flew very well at the time. However, no matter how much we stretched the rubber, it would not go above 20 feet. The flaps just stopped it.

Therefore, you may try reducing the flap deflection, or substantially softening the flaps.

40' is getting close to non-flap territory, but should still be do-able with flaps, if done right.

At Round Valley I saw guys putting non-flappers within a foot of the girders at 95' overhead! Made quite a sound on launch. The typical SO flapper would never take that kind of launch velocity!

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Re: Elastic Launched Gliders B

Postby builderguy135 » May 16th, 2019, 9:59 pm

Predictions for winning times at nats?
Considering the 40' ceiling id say around 130-135 seconds total would win.
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Re: Elastic Launched Gliders B

Postby Jdh3 » May 17th, 2019, 11:38 am

builderguy135 wrote:Predictions for winning times at nats?
Considering the 40' ceiling id say around 130-135 seconds total would win.


I’m going to guess the winning time total will be 127.5 seconds or a score of 154 counting all
Bonuses. Good luck to everyone

Ps. I’m also going out on a limb and going to guess Tower Heights from Ohio will win.

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Re: Elastic Launched Gliders B

Postby Folgore202 » May 28th, 2019, 11:00 am

I wanted to ask, are there limitations in the rules regarding the shape of the gliders? Should they stay true to the standard shape of a plane, or are alternative designs like flying wings allowed?

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Re: Elastic Launched Gliders B

Postby builderguy135 » May 28th, 2019, 3:25 pm

Folgore202 wrote:I wanted to ask, are there limitations in the rules regarding the shape of the gliders? Should they stay true to the standard shape of a plane, or are alternative designs like flying wings allowed?


I guess you could do that but how would you launch it lol
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Re: Elastic Launched Gliders B

Postby Folgore202 » May 29th, 2019, 8:54 am

builderguy135 wrote:
Folgore202 wrote:I wanted to ask, are there limitations in the rules regarding the shape of the gliders? Should they stay true to the standard shape of a plane, or are alternative designs like flying wings allowed?


I guess you could do that but how would you launch it lol


Eh, I figured that a hook under the nose would do the trick. The short fuselage would make for a poor stabilisation of the glider during the launch though...

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Re: Elastic Launched Gliders B

Postby Jdh3 » June 1st, 2019, 8:33 pm

Jdh3 wrote:
builderguy135 wrote:Predictions for winning times at nats?
Considering the 40' ceiling id say around 130-135 seconds total would win.


I’m going to guess the winning time total will be 127.5 seconds or a score of 154 counting all
Bonuses. Good luck to everyone

Ps. I’m also going out on a limb and going to guess Tower Heights from Ohio will win.


Looks like I predicted this event correctly. Idk how close I was to the time. Does anyone know?


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