Elastic Launched Glider B

musicalcoconut
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Re: Elastic Launched Glider B

Post by musicalcoconut »

JonnyL wrote:What would be the best design to use for a glider? Does anyone have recommend a design to use?
Hi, here are some designs you could look at.

A basic, fairly easy-to-build design is the Flicka design. You can modify the online plans to try to improve it and to conform to scioly rules. The highest times I ever got with a modified Flicka design were around 14 seconds in a standard gym, but you could probably get higher times if you adjust the design and make the glider light.

If you're looking for a glider which can get higher times than the Flicka, build a flapper glider. There are lots of flapper designs available on the internet. Specifically which one you choose doesn't actually matter that much since it all depends on how you build the glider and how consistently it launches. The flapper designs have wings built with the front portion of the wing mounted on a pylon. The back part of the wings flap up during launch and then fall back down to an airfoil shape after transitioning into a glide. Flapper designs can get 20+ seconds in a regular height gym.

A lot of people use the Freedom Flight glider kit, but I don't really recommend it. I tried using the kit a couple of years ago and there's a lot of complicated sanding involved and it's hard to get a nice transition out of the glider. I've seen tons of people use Freedom Flight gliders at competitions and although a few of them were successful, most of the gliders couldn't transition into a glide at all. You could always try it but I personally think that just building a flapper from scratch would be better.

Also, like bernard said in an earlier post, the most important factor really isn't the design. Even when you try to build several gliders the same way, there are always fluctuations and sometimes gliders just randomly do things. Build a ton of gliders, build them really light, and practice launching a lot.

Good luck!
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Re: Elastic Launched Glider B

Post by jander14indoor »

One additional recommendation. You need to pick a design that is appropriate to your current building skills. You need to get a well built glider of any design into your hands NOW to start developing the launch and trimming skills so essential to this event. The best designed and built glider will be NO good if you can't trim and launch it right. And if you don't have those skills developed you won't be able to tell if the issue is with the design or the trim and launch.

If you've never done this kind of work before, start with the simple designs like Simple Simon scaled to SO dimensions.
A flapper is within the skill ranges that div B students can attain, but they are definitely on the more challenging end of that range.

AFTER you have a couple of well built gliders in hand to work on building those trimming skills you can start on developing the skills to build more advanced designs when you can't get access to a flying site.

Thanks,

Jeff Anderson
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Re: Elastic Launched Glider B

Post by Bilbo McSwaggins »

JonnyL wrote:What would be the best design to use for a glider? Does anyone have recommend a design to use?
There are many good designs out there, but if you have had some experience building with kits, I would order a freedom flight kit. It costs $50(last time I checked ;) ) and can build 4 gliders.
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Re: Elastic Launched Glider B

Post by fifty_missions »

P2P wrote:So... we (my partner and I) decided to rebuild some of our gliders from scratch. We focused on keeping them light and they glide really slow now! But one of our gliders seems to work perfectly when handlaunching it, but has a few problems when we launch with the elastic.

First, the glider seemed to nosedive a lot, but I think we got that fixed from the wiki's troubleshooting page.
Next, the glider would seem to stall every time it slows down a lot (about every 10-15 seconds), it is a very small stall so I was just wondering whether it is really worth to fix it while having the rest of the glide become a little faster.
Last, and the biggest problem, we have one glider that never stabilizes and stays in the angle of the initial wing bank (about 45), we have tried to adjust the wing bank, but it doesn't seem to affect it until we launch it almost totally flat. This problem leads to the glider making a very fast arc towards the ground. While this glider does not have to be used in the competition, I would preferably like to use it because it has a very slow descent.

Thanks!
On the biggest problem glider-
1) Bend the leading edge UP a couple of degrees of the of the wing that flies low. This will help that wing create more lift with the added incidence.
2) Bend the trailing edge DOWN a couple of degrees of the wing that flies low.
3) If the glider orbits towards the wing that is low check for too much stab tilt.
4) " " add opposite rudder trim to oppose that orbit.

Good Luck,
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Re: Elastic Launched Glider B

Post by bernard »

How do you decide how stretchy the rubber for your launch handle should be? What are the effects of using more/less elastic rubber?
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Re: Elastic Launched Glider B

Post by fifty_missions »

Determining the size of the rubber "motor" is a bit of hocus-pocus but we can dial-in a few factors-

1) 1/16" cross-section is a good starting point for typical gym heights and begin with at least a 7" loop. The glider and the pilot will dictate the effectiveness.

2) For ceilings higher than 50', gradually moving up to a max cross-section of 3/32" x 7" loop may be required.

What we want to have is a substantial stretch for launching the glider. For instance, if a loop uses 3/32" with a smaller loop such as 5", the tendency will be for the glider to experience gun-shot launches that cause shock waves that impact the leading edges of the wings and tail assembly especially on designs like the Freedom-Flight Glider. If the wing does not fail on the first launch, it will eventually as those stresses weaken the structure over numerous launches. It may be a contributing factor for wing failure from high speed vertical impacts on the floor.

A good indicator that the glider is too fragile for the size of rubber loop will be when the glider "Hums" when launched. This means the flying surfaces are fluttering excessively due to that shock wave. The fluttering also damages the flying surfaces over successive launches to a point of failure.

Give the glider more time to speed-up to the launch velocity. Using relatively thinner rubber (closer to 1/16" than 3/32") will allow this to work. It also may mean that the student with longer arms gets to do the launches. Its just one of the many variables to test. Another "compensator" is to add a 1/32 plywood tab at the CG as a finger grip for launches.

This info should prove practical.

Regards,
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Re: Elastic Launched Glider B

Post by bernard »

Does anyone know times for this event from the National Tournament?
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Re: Elastic Launched Glider B

Post by bernard »

Pilgrimage Homeschool (Division B), which was 7th, had a time of about 90 seconds.
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Re: Elastic Launched Glider B

Post by asthedeer »

bernard wrote:Pilgrimage Homeschool (Division B), which was 7th, had a time of about 90 seconds.
Um...okay...find it weird to have OUR time posted. :P (It's fine, unless the people actually doing gliders mind). We had ~30 per flight, so I'd guess around 31/flight for 1st 3 places?
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Re: Elastic Launched Glider B

Post by bearasmith »

Nope, don't mind at all. :D
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