Elastic Launched Glider C

jander14indoor
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Re: Elastic Launched Glider C

Postby jander14indoor » February 28th, 2014, 10:56 am

I'm guessing that next year it will be back to Wright Stuff?
I hope so. Wright stuff is a lot easier than gliders.[/quote]
Hmmm, assuming this comes true (likely but never sure) guess we'll have to think of challenging bonuses the FIRST year instead of the second...
Single bladed props?
Two separate props? Three?
Unknown payload (my favorite)? Student chosen for bonus or supervisor chosen for unexpected?
Rise off ground?
Canard?
Biplanes vs monoplanes?
Student made vs commercial props?
Suggestions?

Hmmm, only three months to get a good proposal together for the committee.

Jeff Anderson
Livonia, MI

Asteroidea
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Re: Elastic Launched Glider C

Postby Asteroidea » February 28th, 2014, 1:39 pm

Well I think most people who are still competing would have never done Wright Stuff, b/c Heli was my first two years and ELG was my last two years. So I have zip experience in Wright Stuff XD

bjt4888
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Re: Elastic Launched Glider C

Postby bjt4888 » February 28th, 2014, 6:35 pm

Jeff,
I would suggest the following possible ideas for future year Wright Stuff:

1. Span limit and overall length limit to make transport reasonable
2. No wing chord limit or stabilizer or rudder limits to allow creative designs that push performance
3. Maybe allow student to choose either a modified commercially available propeller or a student designed and constructed propeller; this would provide a built-in bonus for students that make the extra effort to construct their own propeller. I especially like this design possibility as efficient propeller design would hopefully encourage students to some pretty high level research. Also, if a 2.0 gram overall weight minimum were to be used (see #4 below), the aircraft would be a little different than any existing AMA or FAI class and the optimum propeller design would not be a direct copy of current AMA/FAI designs. Creative variations and experimentation would be necessary for top performance.
4. Relatively light minimum overall weight requirement like 2.0 grams to make it likely that the student constructed propeller would be necessary to reach the minimum
5. Monoplane only to keep focus on propeller design and construction
6. Something in the range of a 2.5 gram rubber limit; allows encouraging performance for moderate weight aircraft that may require 3/32" rubber and very high performance from aircraft built to the minimum weight.
7. Probably no limit on motor stick length to keep the number of judging check-in items to four (LOA, span, weight, rubber weight)
8. The usual limits on materials for the sake of safety

Having worked with HS students for the last five years in design modifications and flying indoor rubber powered aircraft, i think that this style of rule set would be both encouraging for the novice to get into the game and challenging for students that want to tackle a serious challenge. Just my opinion though, of course. I think that the people that have been designing SO events for all these years have done a great job.

Bjt4888
AMA 77545 (off and on since 1972)
NFFS (also off and on for many years)
Indoor competitive (but not too competitive) free flight modeler

calgoddard
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Re: Elastic Launched Glider C

Postby calgoddard » March 1st, 2014, 3:14 pm

The moderator may want to move this response off the ELG thread to a new thread.

I sincerely hope traditional Wright Stuff (rubber power) returns in Division C next year. It has been many years since it was a Division C event. Wright Stuff has long been a favorite of students and observers. Students that have competed in Helicopters and Elastic Launched Glider can leverage their knowledge and skill into the Wright Stuff event.

Many people already have winders and commercial suppliers will make suitable width rubber available at reasonable cost. A team could build and fly two very competitive Wright Stuff airplanes for under $20 using materials bought at the local hobby store and plans readily available on the Internet.

I am not a fan of the e-Wright Stuff event. I’d hate to see a flying competition determined by who could find the best (most expensive) precision miniature electric motor and high tech capacitor. In traditional Wright Stuff, a team could win Nationals using rubber from just about any batch of commercially available Tan Super Sport rubber even if the competition had access to the legendary May 99 TAN II rubber. For the sake of brevity, I won’t detail my other objections to e-Wright Stuff here.

I like the idea of allowing student- built propellers in the Wright Stuff event at regional, state and national competitions, because this would encourage further experimentation and learning.

The 2010 Division B Wright Stuff rules were very workable. The max wing span was 40 cm and the max stab span was 28 cm. There was no max chord for the wing or stab and this encouraged testing various aspect ratios and wing loadings. The minimum weight of 7.0 grams allowed most students to build near minimum weight, did not put a premium on finding contest grade balsa, and ensured that flight times would be limited - most were under two minutes. There were very few 3 minute flights in SciOly competitions in 2010. Almost all teams completed their two official flights during their 8-minute flight period even though the 2nd flight counted if the airplane was launched before the expiration of that period, as it should.

I would not put a maximum limit on rubber weight. The maximum 40 cm wing span and minimum 7.0 gram air frame weight limitations will effectively limit flight duration. Why not allow students to experiment with different rubber weights? Also, the check-in will be greatly simplified if parent volunteers don’t have to weigh rubber motors. Students can lube their motors in advance, and use O-rings, without fear of exceeding some rubber motor weight maximum.

There is no need to limit the airplane to a monoplane. If students want to experiment with biplanes, so be it. They should first do some research.

I’d stay away from requiring the airplane to rise off the ground (ROG). Too many Wright Stuff airplanes didn’t take off many years ago when that was a requirement in the Division C Wright Stuff rules. The left wing tip would drag along the ground due to excessive torque and/or inadequate wash in and too many students were disappointed with a “flight” of zero seconds.

I would make a Team’s Score the total of two official flights to reward consistency and skill and devalue the luck factor - e.g. one team that happens to skate the ceiling and get all the right bounces on one flight.

Bonuses should only apply at State and National competitions. The pusher bonus was a nice challenge one year. Twin propellers would be a good bonus for Nationals. Ditto for a canard. I don’t like a payload bonus for many reasons. The bonus should reward novel airframe design and testing skills. I’d much rather see a cool twin flying around the gym, rather than a traditional tractor carrying a penny. So would the crowd.

Just my two cents.
Last edited by calgoddard on March 2nd, 2014, 5:44 am, edited 1 time in total.

fanjiatian
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Re: Elastic Launched Glider C

Postby fanjiatian » March 1st, 2014, 7:33 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
Hm. I added some washout using my breath and fingers, but it turned out to be way more than 1/32 inch. It was also uneven, my glider started doing weird things in the flight circle like you said. I ended up just flattening it out to normal.
Is it just my building skills, or is it possible to add washout accurately using the breath/finger technique? I just thought of something that might work, although it might not. What if I put each wing tip on a flat surface, and inserted a 1/32 thick sheet of wood under the back edge?

bjt4888
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Re: Elastic Launched Glider C

Postby bjt4888 » March 2nd, 2014, 9:52 am

Fanjiatian,
Here is a methodology that my students have used toadd washout to the Littl Sweep wing tips:
1. Usually, the glide circle produced by the plan specs is between 30' and 35', a little too big for a single basketball court sized gym. The students add a very small amount of additional right rudder in by bending the TE of the rudder about 1/16" and breathing on it and holding about 10 seconds (it is necessary to sand the rudder to about .025" from it's original thickness of 1/32" in order to make it more bendable). After this shot amount of time bending the TE, of course, it does not stay 1/16" deflected after you stop actively bending it. This adds an almost imperceptible amount of additional right rudder. Maybe 1/64" or 1/100". A test flight will confirm if it is enough or if the procedure needs to be repeated. A good result for this step is to reduce the glide circle so much that it starts to spin in a little (maybe a circle of almost 20').
2. After the above step, bend in the wingtip washout to about 1/32". It is not necessary to be super precise, 1/16" washout is ok too. Deliberately bend in the washout a little less on the right wing tip (ex. 1/32" on the left tip and 1/16" on the right). This will cause the glide circle to open up and flatten out again. The circle should open to about 25' and the glide should be very smooth, and, best of all, the glider will recover better at transition and when flying in bouncy air giving better average flight times.

The beneficial results of these trimming steps are easiest to observe on very light gliders and, as you have observed, it takes careful testing and documentation of test variables to produce the best result.

Bjt4888

bjt4888
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Re: Elastic Launched Glider C

Postby bjt4888 » March 2nd, 2014, 9:57 am

Fanjiatian,
Sorry, I meant 1/32" washout on the right wing tip and 1/16" on the left. Less washout for the inboard wing panel relative to the glide circle direction.

Bjt4888

fanjiatian
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Re: Elastic Launched Glider C

Postby fanjiatian » March 2nd, 2014, 10:25 am

Ah I see! So less washout on the right wing if you're doing a rightwards turn? The amount of washout is different for both sides?
Do you add the washout before you glue the wingtips to the wing or during testing? How do you make sure the washout stays?

bjt4888
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Re: Elastic Launched Glider C

Postby bjt4888 » March 2nd, 2014, 1:06 pm

Correct, less washout for the right wingtip for a glider that circles to the right. Bend in the washout during test flying. It is not necessary to washout during construction. Be sure to understand my previous post; only the last 1" of the wingtip TE (1" along the span) is washed out. The chordwise distance that is bent up is only about 1/4". And, yes, bent in washout tends to unbend and reduce between sessions. As long as some washout is still present and as long as it appears to still be slightly greater on the left wingtip, I usually suggest to the students that they fly it the way it is and not try to bend the washout back to where it was unless they are unhappy with how it is flying.

Bjt4888

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Re: Elastic Launched Glider C

Postby Smithy0013 » March 3rd, 2014, 2:33 pm

I've built twenty second gliders in a relatively small gym and from my experience, washout just simply is not needed. So long as you taper the wings that alone should move you from an airfoil to approaching basically a flat plate at the tip. I have yet to have problems with tip stall because i didnt put a twist in my wing and personally i think youre risking more than you have to gain. Correct me if I'm wrong and there is some other advantage to washout other than stalling.


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