Make Dihedral Magnus Effect Gliders for Walkalong Flight and Payloading
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See this link to learn more about how to launch gliders.
|If YouTube is blocked at your school, you can view this compressed Quicktime movie (30MB)|
This text page is linked to embedded video about making and flying a simple kind of glider, or sending it high up in helicopters.
Below is the transcript of the narration, plus some additional details. The numbers are time markers that tell you where to go in the video to see it. If you have a question, contact me about it and I’ll try to answer it on this page.
Although I have tried to be very forthright about saying that these paper gliders are harder to fly as walkalong gliders than thin foam gliders, I still think it's a good idea to start with paper gliders. It might be a struggle with lots of frustration, but it's a worthwhile struggle nevertheless. I've observed that groups that start with paper gliders do very well when they move to foam gliders. Maybe it's because newbies tend to crush gliders with their careless or nervous hands. But it's so fast and easy--and essentially free--to make new paper gliders as needed. Whatever the reason, it's a good idea to try flying paper gliders first; the effort won't be wasted!
Hi I’m Slater aka sciencetoymaker. These strips of paper tucked away in the helicopter: do they look like gliders? Let’s try them out in the Troposphere! When you become fascinated by things that fly, then you become aware that we live at the bottom of an ocean of air called the Troposphere. Here’s a good page about that:
And it’s even possible to fly this strange glider inside on a deflected wave of air.
The name, Dihedral Magnus Effect glider, is long, but it’s quick and easy to build.
But first, dihedral is the slight upward bend of airplane wings for better flight stability. Without dihedral, the glider slips sideways. Then the Magnus effect is what makes spinning soccer balls curve as if by magic. Physics Girl did a stellar job of explaining the Magnus Effect in this video. https://www.youtube.com/watch?v=YIPO3W081Hw
Even when the glider is traveling so slowly that it seems like it ought to stall and dive out of the air, the Magnus Effect keeps giving it… almost magical lift.
And when I fly the Dihedral Magnus Effect glider like this, it’s called walkalong gliding. The upwardly deflected air lifts the glider up as much as gravity pulls it down—similar to the way hang gliders can stay in updrafts for hours, not just glide.
I don’t want to oversell these. Although Magnus gliders are easy to make and launch in a helicopter, the tradeoff is that they are not very efficient; and paper is actually quite heavy. So they’re difficult to launch and fly. Fixed-wing walkalong gliders made of half-millimeter foam are easier to fly. http://www.sciencetoymaker.org/airsurf/index.htm
But hey, paper’s here and free, so let’s make a glider now.
To start you’ll need some telephone book paper. Newspaper is a little heavier still, but newspaper can be ok too. Now here’s something interesting: all machine-made paper has a grain, so paper is much stronger one way than the other. I’ve cut two rectangles out of one phone book page; identical except that one is parallel to the text while the other one is long perpendicular to text. When you cantilever them off an edge, this one is clearly more rigid so we’ll cut strips parallel to the text. But test your assumptions! This small newspaper is strong parallel to the text; but this large newspaper is the opposite!
The strips should be about 25 mm wide by 155 mm long (1 inch by 6 inches). To get the dihedral, you fold gently in half. Folding in half before cutting means less cutting. It also insures symmetrical halves, so it will glide better. You can save a lot at a time by folding and cutting lots of gliders at once.
You might be able to launch the glider now, but another fold will make it stronger. Origami people say that this is a valley fold. Make a gentle mountain fold perpendicular to the first fold, then mostly unbend it. That hint of a fold makes it less floppy and creates a crude airfoil that helps the glide a little.
If you have too much dihedral angle, then it will not fly. Just a little.
If you are sending gliders up as a payload in a helicopter, slide 3 or 4 under the rubber band at the bottom. The rubber band ejects them as it unwinds. See this link to learn more about how to launch gliders.
For walkalong gliding, you need dead-calm air. That usually means inside, away from air vents. I’ve been in many science museums where it was all but impossible to fly because of air turbulence. However, usually I was able to find a hallway or something where the air was still enough to fly.
If you want to try walkalong gliding, your first hurdle is launching. Your glider should glide away from you, not toward you. Hold the glider from the back like this. There is only a slight dihedral. Give a short push—really just a tiny flick of the wrist--and let go. You can also try launching like this. Practice launches and when 2 out of 3 glide straight, then you’re ready to fly. Experiment with dihedral angle.
The bigger your board is, the better. The top of a pizza box works well. Hold the board almost vertical. It has slant a lot to deflect air upward. Launch high. Keep the glider level with the top of the board. Keep the board so close to the glider that it almost blows over the top.
To gain altitude, make the top of the board go so close that the glider goes over the top. Notice how it went higher just before going over. So this time, raise the board so the glider can’t go over; it gains altitude instead. Try pulses of getting closer to see where the sweet spot is.
You turn by pushing one side of the board closer to one side of the glider. You cannot make sharp turns with this glider and fast moves don’t work. Keep your board smooth and steady.
I learned to fly with a similar Magnus glider and I struggled for weeks before getting it. It takes even longer for the pioneers who charge ahead without anyone to show you how to fly. Flying the glider is like riding a bike: it takes time and practice to learn, then gets easier.
Let’s tip our hats to John Collins, AKA the Paper Airplane Guy, for inventing the first Magnus Effect paper glider, which he calls the Tumbling Wing.
Very humid air makes paper limp and useless
Dihedral Magnus Effect gliders made from thin slices of foam are not affected by humidity; and they are so light that they fly slowly. In fact, I can fly them with just my hands deflecting the air. You can have a single piece of North American standard foam from sciencetoymaker.org, cut it in half and sliced into 13mm or ½ inch strips. They’re very easy to make but are still tricky to launch. Foam fixed-wing gliders are easier to launch but harder to make. Life is full of tradeoffs.
Besides being delicate—you need to handle them very gently--the foam gliders are even more sensitive to how much dihedral you have. If the glider seems to slide or it keeps tipping over like this, then you need more dihedral. If the glider is clunky or won’t glide at all, then less dihedral. There’s not much difference between too much and not enough, so you’ll have to experiment
Fixed-wing foam gliders are easier to launch and fly but harder to make. You can learn about foam here
and buy thin foam sheets here http://www.sciencetoymaker.org/airsurf/store.html