Elastic Launched Glider C

nikoruhe54
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Re: Elastic Launched Glider C

Postby nikoruhe54 » December 30th, 2012, 7:59 pm

Hi I am a student coach in OH and my team and I are having some difficulties during our test flights. One of our problems is that when we do some basic hand drops, our glider flies fine; when we launch the glider, it ascends beautifully, but the transition leads to the plane going into a nose dive. It's frustrating because when we do some basic hand drops the glider flies very well. My question is how important is the stabilizer in the transition phase? Our stabilizers are very small (about 5cm by 2.5 cm) and the main wing is about 7.5cm by 29.8cm. Does the stabilizer play into the transition at all, or is it all just weight distribution and angle of incidence?
We originally thought it was the angle of incidence, so I had my builders insert a small piece of 3/64" wood under the leading edge of the front wing, and as our launches kept looping, we sanded this down until the loop stopped, we finally then glued the wing down, and the loop is gone, but the transition is just awful, we are nosediving and I've personally broken several planes because of this. Any help would be appreciated, thank you so much.

Senior Builder at Mentor High School, OH

theging
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Re: Elastic Launched Glider C

Postby theging » December 31st, 2012, 8:51 am

Hi I am a student coach in OH and my team and I are having some difficulties during our test flights. One of our problems is that when we do some basic hand drops, our glider flies fine; when we launch the glider, it ascends beautifully, but the transition leads to the plane going into a nose dive. It's frustrating because when we do some basic hand drops the glider flies very well. My question is how important is the stabilizer in the transition phase? Our stabilizers are very small (about 5cm by 2.5 cm) and the main wing is about 7.5cm by 29.8cm. Does the stabilizer play into the transition at all, or is it all just weight distribution and angle of incidence?
We originally thought it was the angle of incidence, so I had my builders insert a small piece of 3/64" wood under the leading edge of the front wing, and as our launches kept looping, we sanded this down until the loop stopped, we finally then glued the wing down, and the loop is gone, but the transition is just awful, we are nosediving and I've personally broken several planes because of this. Any help would be appreciated, thank you so much.

Senior Builder at Mentor High School, OH
I had problems similar to this on my first few planes. Have you tried switching up how you launch it? Sometimes the regular way of launching makes it screw up. (By "regular" I mean angle at about 75 degrees, tilt in direction of turn, etc.) Try tilting it the other direction, taking some of the angle off, or even launch it at an angle of over 90 degrees (a little upside-down).

Also, in my experience, just because it glides perfectly when you hand launch it does not mean it will fly beautifully when you fling it up with a rubber band. My planes normally stall after about 2 meters when I hand glide them, but then do fine when I launch them. Don't ask me why...that's a question for Mr. Anderson or Chalker.

To answer your actual question, yes. In my experience (again, I'm just as new as any other student. Ask the more experienced people.) stabilizers make or break the plane, sometimes literally. If you can't get it to work, I would suggest you rebuild and try to get everything squared up.

Finally, being from Mentor, you probably have access to some pretty great builders from years past. Mentor is a very competitive school in Ohio and has had success in building events in the past. Try to get in contact with some of the old builders from Mentor and see if they can help. I'm sure you'll do great!

chalker7
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Re: Elastic Launched Glider C

Postby chalker7 » January 1st, 2013, 11:01 am


Also, in my experience, just because it glides perfectly when you hand launch it does not mean it will fly beautifully when you fling it up with a rubber band. My planes normally stall after about 2 meters when I hand glide them, but then do fine when I launch them. Don't ask me why...that's a question for Mr. Anderson or Chalker.
I can think of two likely culprits behind your stalling during hand gliding tests. The first is that you're probably throwing the glider a little faster than its natural gliding speed. The extra airspeed will give the glider a bit more lift initially, which will eventually throw it into a stall by raising the overall incidence of the glider too much.
The second (and less likely, unless it happens when you're really close to the ground) explanation is that you could be experiencing ground effects. Ground effects are a variety of forces and complications that occur when a flying object is near to the ground, mostly due to air reflecting back off the ground. You might notice your glider (or Wright Stuff plane or Helicopter or whatever) climb a little bit right before it hits the ground, that's because of ground effects. They are not usually strong enough to throw something into a stall, but it's conceivable.
National event supervisor - Wright Stuff, Helicopters
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liutony66
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Re: Elastic Launched Glider C

Postby liutony66 » January 2nd, 2013, 1:44 pm

Hey guys,

So apperently one of the rules for the glider is that it must weigh equal to or less than 15 grams. When you convert that to ounces. Its HALF AN OUNCE. Thats like less than half the weight of a pencil... So how does that work? :?

iwonder
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Re: Elastic Launched Glider C

Postby iwonder » January 2nd, 2013, 1:51 pm

(I don't compete in this event... but...) At contests I've been to these gliders aren't very large, and they seem to be made of very light balsa, so 15g isn't unreasonable.
'If you're the smartest person in the room, you're in the wrong room' - Unknown

schen
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Re: Elastic Launched Glider C

Postby schen » January 2nd, 2013, 3:03 pm

15 grams is way too heavy of a glider for pretty much all ceiling heights. Seeing as we're going to be mainly competing in high school gyms, which have low ceilings, a target weight for your gliders would be between 2-3 grams, or even below 2 grams if your building is good and your balsa is at least decently light. The most competitive gliders would be under 2 grams, but you would do very well with a glider between 2-3 grams. Balsa wood actually varies greatly in weight, so take a scale or something and take the lightest wood you can get. I would suggest getting wood under 5 pounds per cubic foot.

For higher ceilings, 5-8 grams is a good range.

theging
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Re: Elastic Launched Glider C

Postby theging » January 2nd, 2013, 5:22 pm

15 grams is way too heavy of a glider for pretty much all ceiling heights. Seeing as we're going to be mainly competing in high school gyms, which have low ceilings, a target weight for your gliders would be between 2-3 grams, or even below 2 grams if your building is good and your balsa is at least decently light. The most competitive gliders would be under 2 grams, but you would do very well with a glider between 2-3 grams. Balsa wood actually varies greatly in weight, so take a scale or something and take the lightest wood you can get. I would suggest getting wood under 5 pounds per cubic foot.

For higher ceilings, 5-8 grams is a good range.
For competition, you're gonna want about 3 grams with ballast at the very most. schen got it right. Keep in mind you need less wood than you think. Pretty much everything can be cut down and sanded until it's barely there. If you do it right, your landings and the like will be so slow and gentle it won't break.

schen
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Re: Elastic Launched Glider C

Postby schen » January 3rd, 2013, 7:27 am

Another big factor in weight that I've found is glue. You don't need a lot of glue! Make sure there are no gaps in your joints before you glue, and use as little as you can. I also suggest wiping off excess glue before it dries.

science8
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Re: Elastic Launched Glider C

Postby science8 » January 3rd, 2013, 12:17 pm

Suggestions for width and weight of fuselage? What I have been using is too heavy.

jander14indoor
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Re: Elastic Launched Glider C

Postby jander14indoor » January 3rd, 2013, 2:51 pm

Hey guys,

So apperently one of the rules for the glider is that it must weigh equal to or less than 15 grams. When you convert that to ounces. Its HALF AN OUNCE. Thats like less than half the weight of a pencil... So how does that work? :?
The ONLY reason for the 15 gm upper limit is safety. We didn't want heavy gliders being flung willy-nilly around the gym and injuring students!!

PHYSICS says your glider should weigh as LITTLE as possible. IF you can get it to the ceiling safely a 2 gm glider will beat a 3 gm glider every time. And a 1 gm glider will beat both! As for how, others have hinted, but look back up this string for extensive discussion and especially look for the links to the AMA Glider site.
Suggestions for width and weight of fuselage? What I have been using is too heavy.
Look back up this string for discussion, and at the AMA Glider site for competitive plans, also mentioned back up this string. Note, ONLY the nose has to pass the bluntness test, as you see on the AMA site, the rest can be very thin.

Jeff Anderson
Livonia, MI


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