Elastic Launched Glider C

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sr243
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Re: Elastic Launched Glider C

Post by sr243 » February 24th, 2013, 4:54 pm

Yeah, people have been able to crack 20 seconds. I know teams in my state have gotten 21 seconds in a gym. It is going to be fun to contest that with my 10-15 second glider...

Lake101258
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Re: Elastic Launched Glider C

Post by Lake101258 » February 24th, 2013, 9:33 pm

What is a better way to adjust incidence, adjusting the main wing angle or the horizontal stab

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sciencegreek
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Re: Elastic Launched Glider C

Post by sciencegreek » February 25th, 2013, 5:11 am

sr243 wrote:Yeah, people have been able to crack 20 seconds. I know teams in my state have gotten 21 seconds in a gym. It is going to be fun to contest that with my 10-15 second glider...
How high was the ceiling?
We have been getting 20-21 seconds per flight but our ceiling is only 21 feet tall

sr243
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Re: Elastic Launched Glider C

Post by sr243 » February 25th, 2013, 4:21 pm

sciencegreek wrote:
sr243 wrote:Yeah, people have been able to crack 20 seconds. I know teams in my state have gotten 21 seconds in a gym. It is going to be fun to contest that with my 10-15 second glider...
How high was the ceiling?
We have been getting 20-21 seconds per flight but our ceiling is only 21 feet tall
Yeah, the ceiling is way higher than that. Not exactly sure. That time is pretty amazing though.

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fifty_missions
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Re: Elastic Launched Glider C

Post by fifty_missions » March 1st, 2013, 2:20 pm

Adding incidence to a new built glider or one that is finished has its issues. For a new build, attach the wing assembly to a separate hard balsa stick that is slightly longer than the chord of the wing. Use thin strips of masking tape to anchor the wing "assembly" to the fuselage. Now, multiple adjustments may be made. These include..

1) Leading edge incidence: small wedge between wing assembly and fuselage.
2) Center-of-Gravity (CG): mount the wing assembly closer or further from the nose.
Make fine colored marks on the fuselage to orient the wings as you test (and document in a log). I recommend PIGMA MICRON 02 marking pens for this task. Create a color key in your log for reference.

Note that indoor glider designs tend to fit these guideline ratios... 1/3 fuselage length ahead of wing leading edge to possibly 1/5 fuselage length ahead of the wing leading edge. Too long, the glider will fly to stable in the pitch axis and follow its nose into an arching, arrow-like flight path. Too short, the glider may become pitch sensitive with little consistencies in flight and need a TON of clay to counter the mass aft.

Now, what about the incidence issue after the glider is built? To raise the nose (slightly!!) during the glide, the simple, most effective method is to add up elevator. The process is simple BUT only if the stabilizer has been sanded down around 1/20" or 1/64" thickness. Any thicker, no dice, it will crack! If the trailing edge (last 1/3 of the chord) has been made thin, simply COMPRESS the wood between your forefinger and thumb and bend up a couple of degrees. Hot breath during this procedure is helpful. Make a couple of test flights to note any changes. Be diligent and record your results. You can make further adjustments to add or reduce that adjustment.
This method does add a smidgen of drag but that trade off is cheaper than the weight of removal and re-gluing.

BTW, NEVER, bend the stabilizer's trailing edge DOWN below the leading edge! Why??, during the speed changes in flight, at some point that adjustment will have more authority and nose the glider right over into a DIVE!

Off to another mission,

_HenryHscioly_
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Re: Elastic Launched Glider C

Post by _HenryHscioly_ » March 2nd, 2013, 5:40 pm

is it more important to watch weight or drag?
testing different wing planforms and airfoils and lifting area, or
building something super light..1.5 grams
eg. 2.2gram glider, good transition and 20 second flight in school gym
what sets it apart from making 30 seconds..or even 40 seconds..

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Re: Elastic Launched Glider C

Post by jander14indoor » March 2nd, 2013, 9:06 pm

My vote is always save weight first, second and third.

With less weight, you can fly slower, automatically reduces drag.

Then drag.

That all assumes you have a good transition and can get the glider to the ceiling.

Jeff Anderson
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Re: Elastic Launched Glider C

Post by Asteroidea » March 3rd, 2013, 7:15 pm

hi! I was wondering how you can improve a transition? Our glider currently gets around 11ish seconds in an average gym space, but I have no idea how to improve our transition so that it transitions closer to the ceiling or has a lower sink rate, besides losing weight XD thanks!

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fifty_missions
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Re: Elastic Launched Glider C

Post by fifty_missions » March 3rd, 2013, 9:36 pm

An SO Indoor glider transition is based on weight (3.5 grams or less), relatively small areas on the stabilizer and fin. Those gliders with higher wing loadings (over 4 grams) and skinny wings (2.5" wing or less wing chord) will require a wide climbing orbit after launch to gain altitude, reduce speed and transition into a glide. These heavier airplanes must maintain speed to stay flying into their downhill glide path.

Those airplanes that weigh less ANDalso have a wider chord (3"plus) while featuring small areas on the tail may be launched almost vertically and transition as they stall from speed loss (from the launch). It can even happen as a slight backslide into a horizontal attitude and then enter their downhill glide.

Coaxing the transition usually happens if the stabilizer's trailing edge (elevator) has some up elevator added. Just a couple degrees. This may mean adding some nose weight, but, that up elevator will assist the transition.

What may also help is adjusting the turning orbit that the glider transitions into. This could mean adding more or less turn and simply something you must try on your specific glider.

One last thought, add a little banking that compliments the glider orbit direction when you launch. For instance, if the glider has a counter-clockwise orbit, launch the glider with the port wingtip lower than the starboard tip.

The launch attitude is also critical. The degree of launch incidence and power is just something you test.

I am a very strong proponent to having enough up elevator so that the glider stalls and will be less apt to diving and crushing the nose on impact when you BEGIN the trim process. As you come to understand you glider's capability, you can make adjustments to cure the stalls and also get the most from the transition.

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Re: Elastic Launched Glider C

Post by 314chocolate » March 4th, 2013, 6:20 am

Those gliders with higher wing loadings (over 4 grams) and skinny wings (2.5" wing or less wing chord) will require a wide climbing orbit after launch to gain altitude, reduce speed and transition into a glide. These heavier airplanes must maintain speed to stay flying into their downhill glide path.
So is it worth adding the additional weight and making the wing chord wider? Right now I get about 10 sec flights.

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