Elastic Launched Glider C

calgoddard
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Re: Elastic Launched Glider C

Postby calgoddard » February 23rd, 2014, 4:08 pm

A top competitor might be able to get 18 - 19 second flight times with 20 feet of ceiling height.

A top competitor might be able to get 26 - 28 second flight times in 30 feet of ceiling height.

The sink rate of a properly trimmed CLG with a 28 cm max wing span and weight near the 3 gram minimum is around one foot per second, once it assumes a stable glide. Of course the glider must first transition into a stable glide, which occurs below its apogee.

The 2014 ELG rules place a premium on consistency because the Team's Score is the total of the best three of five official flights. This is a good thing, in my opinion.

In addition to ceiling height, the Team Score needed to medal (top three finish) in the 2014 ELG event at a particular regional or state SciOly competition largely depends on the level of competition, i.e. the experience and expertise of the students competing that they have gained through building and practice. Some regions in states such as California, Illinois, Indiana and Ohio, have historically, had very good builders and flyers in the SciOly flying events. Also the more ELG teams there are competing, typically the higher the Team Score you will need to win a medal. Some regional SciOly competitions may have 30+ teams competing. The just-completed San Diego Division C SciOly regional competition had 80 teams and probably a majority of them competed in the ELG event.

Bear in mind that the best ELG team(s) may not be at a state competition because their school did not advance from regionals to the state level.
Last edited by calgoddard on February 25th, 2014, 7:00 am, edited 1 time in total.

bjt4888
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Re: Elastic Launched Glider C

Postby bjt4888 » February 24th, 2014, 8:59 am

About a week ago, I posted a plan and some construction notes for a basic flapper style glider that meets the 2014 SO rules on the Hip Pocket Aeronautics Builders Plan Gallery. The plan is called "Flapper SO 2014 CLG". Also posted under the "Science Olympiad" subject on the Hip Pocket Aero site are some posts relating performance and adjusting and flying experiences. The students that I am coaching are finding that this design performs well, and like other flapper gliders, has more variables to keep track of in order to adjust and fly successfully. For top performance, there are still many other ideas beyond this design, and beyond AMA style designs, for students to research and test, including solving the canard.

Bjt4888

fanjiatian
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Re: Elastic Launched Glider C

Postby fanjiatian » February 26th, 2014, 3:27 pm

Can someone recommend an accurate way to add washout? I feel like using just your hands and warm breath would make the washout uneven on both sides of the wing
The wing I"m working with looks like the one in the Simple Simon except the edges are rounded and the center is mounted on a curved pylon
I'm just not sure how the trailing edge should be bent upwards, should it just be the back edge raised, or diagonal, including the furthest tips of the wing tips?

bjt4888
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Re: Elastic Launched Glider C

Postby bjt4888 » February 26th, 2014, 7:55 pm

Fanjiatian,
For the typical tapered, semi-eliptical small glider planform, washout of the wingtips should improve performance by reducing lift induced drag. For thin wing wood like 1/32" or thinner, heating the area with your breath and bending works fine. Typically, for this size glider the area bent up is the last 1" of the trailing edge nearest to each wing tip with the bend starting about 1/4" from the trailing edge in the chordwise direction as measured at the very tip. I have found that for the Stan Buddenbohm Littl Sweep about 1/32" of washout on each tip works pretty well. Larger, higher aspect ratio gliders with very narrow tip chord,like the Ron Whittman Super Sweep (hand launch glider), use as much as 1/8" washout bent in. For thicker winged gliders like the Littl Sweep Category III/IV glider, washout can be sanded in. Hope this helps. Also, if the washout is not identical on both wing tips, even if it is only 1/64" different, it can cause the glide circle to change. Washout for very large gliders is sometimes progressively added to the trailing edge in progressively increasing amounts over the entire length of each wing (from center to tip).

Bjt4888

wiseowl63
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Re: Elastic Launched Glider C

Postby wiseowl63 » February 26th, 2014, 8:45 pm

So before I go all crazy and start building for next year, does anyone know whether or not Gliders will still be around or is it going to be replaced. I know in the past they have run on about two year cycles, but can anyone confirm this.

Asteroidea
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Re: Elastic Launched Glider C

Postby Asteroidea » February 26th, 2014, 10:23 pm

It's usually run on a 2 year, 3 event cycle (similar to bridges/boomi/towers) or so I hear....
I'm guessing that next year it will be back to Wright Stuff?

wiseowl63
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Re: Elastic Launched Glider C

Postby wiseowl63 » February 27th, 2014, 7:17 pm

I'm guessing that next year it will be back to Wright Stuff?[/quote]
I hope so. Wright stuff is a lot easier than gliders.

lchs
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Re: Elastic Launched Glider C

Postby lchs » February 27th, 2014, 8:18 pm

I believe that it will be Wright Stuff. On the following link, you can find the schedule for the Coaches Summer Clinic, and Wright Stuff is indeed listed there.

http://www.soinc.org/summer_institute

Smithy0013
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Re: Elastic Launched Glider C

Postby Smithy0013 » February 28th, 2014, 7:02 am

So the canard issue. Has anyone actually achieved success with it? I've gone through 4 different designs each improving on the last but still no clean transition, no steady glide and the circle is eh. The pitch instability is just wrecking havoc. I know its inherently unstable along that axis for canards but has anyone improved this by shifting CG around or incidence angles or anything like that?

goswal
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Re: Elastic Launched Glider C

Postby goswal » February 28th, 2014, 7:51 am

So the canard issue. Has anyone actually achieved success with it? I've gone through 4 different designs each improving on the last but still no clean transition, no steady glide and the circle is eh. The pitch instability is just wrecking havoc. I know its inherently unstable along that axis for canards but has anyone improved this by shifting CG around or incidence angles or anything like that?
My team hasn't had any issues with steady glide, but aside from that, we've experienced all of these problems. Our biggest breakthrough has been the increase of our static margin (shifting our CG forward) counterbalanced by a massive increase in angle of incidence. This has allowed us to achieve relatively consistent transitions.

I think one of our main reasons for flight and transition stability (or lack thereof) is the ratio of wing SA to canard SA. We're using a massive canard, relatively speaking, nearly half the SA of the wing. I think this has contributed to a stable and slow glide, but it may also have contributed to a very mediocre transition: we're having trouble getting the glider to "flip over" like our gliders last year did, near the peak of their ascent. We're losing several feet on each transition with our canards.

As for the "circle," my team has experimented with the two main methods: turn originating from a relative roll between the canard and the main wing, and turn originating from the vertical stab. We think that turn originating from roll is more efficient and would be the ideal way, but we're having issues with consistency: the difference in roll angle between the canard and the wing is so small that we often glue our canard with too much roll angle, resulting in a "dive-bomb" effect after the transition. Although turn originating from the vertical stab seems less efficient and stable (and is not ideal according to several AMA guys with whom I've spoken), we've been able to achieve it more consistently with canards. That said, we're still attempting to get our turn out of roll angle.

Hope this helps, and if anyone has any advice for me (or wants to tell me I'm wrong) it would be greatly appreciated!


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