Future Aviation Events

[wlsguy]

Since we have been talking about gliders, any news on how everyone is coming along?

It was run as a trial event at Wright State this year and the winner had a 2 flight total of 4.71 seconds (2.5 seconds / flight)
I'm sure this will go up but, how is everyone doing now?
Our team is up to ~ 15 seconds / flight and still progressing......

p.s. No, I don't think Eggonaught is scheduled for next year. B division will have Helicopter Egg drop (unless things change which they often do...)

[thsom]

Since we have been talking about gliders, any news on how everyone is coming along?

It was run as a trial event at Wright State this year and the winner had a 2 flight total of 4.71 seconds (2.5 seconds / flight)
I'm sure this will go up but, how is everyone doing now?
Our team is up to ~ 15 seconds / flight and still progressing......

p.s. No, I don't think Eggonaught is scheduled for next year. B division will have Helicopter Egg drop (unless things change which they often do...)

Not including the design from the simple simon (which I haven't completed yet), we have reached 12 seconds, though this was by pure guessing and I'm hoping the simple simon will work much better...

[Orange714]

That's the same website we used. We've built the Simple Simon, but we're having trouble trimming it and the flights vary greatly from one to the next. None of us have had any experience with Wright Stuff though...

[jander14indoor]

OK, perhaps time to start talking about what it takes to succeed in this event. Note, comments are based on AMA experience with indoor and outdoor catapult gliders, but the general principals and approaches should be good.

First, you should know what a good flight is to judge your efforts against, and so we can start talking the critical factors in success.
Stage one launch. Competitor stretches the rubber just enough to launch the glider to just under the ceiling, holds rubber almost vertical, and releases the glider nearly vertically, often tilted so climb is a spiral or corkscrew. This is to prevent launch stalls. Glider climbs to ceiling essentially balistically, NOT on lift. That corkscrew path is aerodynamic, height is ballistic. The most important thing here is to be dead consistent for the next phase. And of course the rubber stretch changes as ceiling height changes. The consistency needed in this phase makes competitor launch SKILLs much more important than for Helicopter & Wright Stuff. Another reason for lots of practice.
Stage two transition. This is probably the trickiest part, trim wise, and depends on dead consistent launches. As the glider reaches the top of the ballistic launch, it almost, but not quite, stops, rolls wing level, points the nose down, accelerates, and transitions to a nice glide. Done right, it is a thing of beauty. Done wrong, well, lets just say a lot of height is lost very quickly. It is dependant on trim conditions (cg, relative wing and horizontal stab angles of attack, differential 'aileron', etc) and sensitive to small changes in those around the optimum point.
Stage three, glide. Now your glider behaves like a normal plane. Your goal is to minimize descent rate, and all that that implies. If you ever did balloon launch, everything you learned there applies. A good glide will be a gentle, floaty, near stall circle to the floor.

So, what how does this help? Well, how is your glider performing against that ideal? What angle are you launching at, what wing tilt, what does the transition look like, the glide. Without details it is hard to help!

OK, this is long enough for now, I'll talk design implications in another note, unless someone else beats me to it.

Oh, what's 'good'. Of course that will depend on ceiling height, but look for way better than 1 second per foot in real low sites, and close to 1 sec per foot for real high ceilings.

Jeff Anderson
Livonia, MI

[Orange714]

I have a couple questions regarding your post. What do you mean by "balistically" as you use it several times in your post. My other question is that does your climb have to be a spiral or corkscrew, I've youtubed a couple of videos on Catapult gliders and all of them seem to go straight up and transition to glide, without the corkscrew or spiral you mentioned. And last question is regarding our own glider which isn't doing too well-When we launch it vertically (around 60?ish) it tends to go up and then instead of "transitioning" it just dives until just before reaching the ground pulling up a little and then gliding for a couple of seconds before landing. Our plane is the simple simon and so the wings are dihedral and around 35 degrees. Thanks in advance

[twototwenty]

jander14indoor - Thank you for putting the time into that post; it was very helpful for understanding the basics of the event. I haven't been able to start working on this yet, but I hope to soon. The one question I had was this: how do you make the glider transition? This was the one thing I really can't figure out.

[jander14indoor]

Ballistically, like a cannon ball. Object moves completely under influence of initial velocity and gravity. This is as opposed to aerodynamically where you get significant lift force from the wings. Note, in truth you never have ANY of these cases purely. My point is the main reason your glider rises to the ceiling is the initial velocity imparted by the rubber, NOT wing lift. Your glider doesn't 'fly' to the ceiling, its thrown to the ceiling. Kind of like launching a rock to the ceiling with a slingshot. Now the PATH is influenced by wing lift, thus the spiral or corkscrew.

Spiral or corkscrew vs what you see on youtube. Yes I mean spiral. BUT, don't think in terms of multiple turns on the way to the ceiling. Think more like a quarter to half turn, maybe a full turn in a really tall site. I went to the videos on the AMA site http://legacy.amaglider.com/assets/indo ... ideos.html you can see the half turn or so on launch. Here's why. The bulk of the flight is at a slow speed in glide, so the glider has to be trimmed to near a stall at that slow speed. But the launch is at HIGH speed, creating HIGH lift. If you launch wings level the plane WILL try to loop around and hit you in the back of the head. Sometimes it succeeds, been there, done that. The tilted launch is meant to turn that loop into a spiral that ends at the ceiling instead of the back of your head, maximizing the height gained for minimum energy input.

The transition. Based on your description you obviously have that bad transition where a LOT of altitude is lost. Then not enough time to know if your glide is any good. Go back to the AMA glider site and read the article "The Big Glider Secret" http://legacy.amaglider.com/assets/gene ... ecret.html It describes what it takes to get a good transition. Basically you have to have the right incidence between the wing and horizontal stab. Transition is VERY sensitive to this. Looking at the Simple Simon glider plan its set up 0-0 meaning both wing and stab have the same 0 degree incidence relative to the fuselage. This is pretty typical. If there is ANY curve in that fuse you don't that. If there is much curve in the surfaces, you don't have that. For a built model, you can tweak by gently bending the fuse, adding or removing curve, same to wing and stab. SMALL amounts of adjustment. Read and understand that article again to see how to get there.

Hope that helps,

Jeff Anderson
Livonia, MI

[Orange714]

That makes a lot of sense, and assuming the transition is very sensitive a tiny bit will make a big difference. When you say " If there is ANY curve in that fuse you don't that. If there is much curve in the surfaces, you don't have that" what do you mean? I'm assuming that you meant that you don't WANT any curve in the fuselage and the second part I just didn't really understand. Also what do you mean by "adding or removing curve"? Do you mean by sanding the wings and the stab to like an airfoil shape? Thanks

[jander14indoor]

Yeah, sorry, that wasn't too clear.

OK, incidence, what is it. Its the angle between some reference line and the flying surface (wing, tail, whatever). Trick is where what is the reference line and where do you measure that angle on the wing? TYPICALLY the reference line is drawn on the plan and is along the fuselage centerline, more or less. And for the wing it is properly measured from the forward most point of the leading edge and the aft most part of the trailing edge. That an be a little tricky for flat bottom wings as most people miss that the leading edge is a little elevated thus the wing should NOT be measured along that flat bottom.

Now lets look at the Simple Simon plan. In that case the wing and stab are FLAT pieces of balsa and you can use either the top or the bottom of the wing. No reference line is drawn on the plan, but there is a nice straight edge along the whole length of the bottom of the fuse. Notice the wing is mounted on top BEFORE it starts tapering, thus its incidence is 0 degrees. And notice the tail is on the bottom along that flat ref line and thus again 0 degrees incidence. Thus the wing and stab are parallel from a side view or 0-0 incidence. Very important to the behavior of the model, especially in transition.

What happens if the fuselage stick is bent along that bottom surface? Now that theoretical straight line in the drawing is a curve and the wing and stab AREN'T parallel. The relative incidences have changed and you aren't at 0-0. What do you do? Well you could rebuild the model with a straight fuse, but that takes a while. In the meantime, you can gently bend the fuse straight and bring the wing and stab back parallel.

What happens if the wing or stab aren't flat? Well, the bottom or top are probably no longer the correct ref line so again the wing and stab probably aren't 0-0. Oh, and 0-0 may not longer be the correct incidence for a good transition. Again, you can rebuild correctly, or you can bend the surfaces flatter to bring things back to 0-0.

You also asked how to add or remove curve. Balsa is a fairly pliable and malleable material. You can just bend by hand beyond where you want to go and get some semi-permanent new shape. Or you can steam and bend to get a more permanent new shape. Sanding to change shape is really back to rebuilding the model correctly.

There are other adjustments to get the right incidence for a good transition, but to start, you are best keeping close to the specs in a proven design.

Hope that's a little more clear.

Jeff Anderson
Livonia, MI

[calliekernick]

I'm a bit confused on what this trial event is looking for. Would a balsa wood and mylar glider (similar to ones seen in the past event Balloon Launch Glider) hold up under the stress of the launch? If not, is a solid balsa wood glider the best way to go?