Friday, January 20, 2017

glide ratio

Super coolness has just occurred, only a few minutes ago.

I just finished building a 1/5th scale model of a Rogallo wing, the biggest I've made yet. The wingspan is 52" - a little more than four feet. Full scale is a 22' wingspan. 22 feet, that is. The one I made is 52 inches. This is the fifth model of a Rogallo wing that I've made. You know... for the hang glider.

The first one was just WRONG. It was built out of bamboo shiskabob sticks and a tall kitchen trash bag. This is the one that, when launched, performed the unashamed, instant stall with a loop-duh-loop. It had about a 3 foot wingspan.

The second one, I rebuilt from the ashes of the first one. It was completely destroyed when it plummeted straight into the ground from about a hundred feet in the air, at about 30 mph I'm guessing, when I was flying it like a kite at Northlakes Park a couple of months ago. 3 foot wingspan.

The third one I built out of wire clothes hangers instead of wooden utensils. This one was like the first one, but smaller, and on acid.  When I launched it, 45% of the time it would nose straight down and 45% of the time it'd do a psychotic loop-duh-loop after a dramatic stall. 10% of the time it would do just the most amazingly perfect glide. 2 foot wingspan.

The fourth one I built just like the third one, but using shishkabob sticks again. My reasoning was that maybe the metal clothes hangers were too heavy. I never got to test fly this one, because I stepped on it when it was buried under a mound of dirty clothes, and it just broke, all over. 2 foot wingspan.

The fifth one I just completed a couple of hours ago. I was way more carefuller with the measurements on this one than I was on any of the others, because this one is a big one, and errors tend to magnify on a logarithmic scale by orders of magnitude. Who knows. So I had to nail a great big, unfolded lawn and garden hefty bag onto the wall, and I used one of those roll-up sewing rulers and a sharpie marker and a regular short 12 inch ruler for a straight edge to draw the shape of the borders of the most precise Rogallo wing ever, ever, onto that hefty bag nailed to my wall. When it was finished, I very carefully cut it out with one of my many thrillions of knives that I keep on hand, ready for deployment at an instants notice.

The final shape of the flat, unmounted wing was that of a right triangle with an outwardly curved hypotenuse, with the point of the right angle serving as the exact center of a circular border defined by the curve of the hypotenuse, which covered about 30 degrees of arc. I mounted it onto these long wooden dowels that I found in the crafts and hobbies department at WalMart, and all of a sudden it was a wing, for flying.

I just took it out for its maiden voyage, and man. How the wings billowed and took shape as they slipped easily, like a form-fitting garment, onto the wind. Just a trash bag taped to wooden dowels... but oh how it sailed. It was so pretty. And stable. No sudden nose dives, or psychotic stalls with a backwards loop-duh-loop right into the ground. This one just flew straight, with a glide ratio of about 4:1. That is, for every four increments of flight, it lost one increment of altitude. That's a pretty crappy glide ratio actually, but the important thing is, it was a glide ratio, and not a nose dive or a psychotic stall, ending in a loop-duh-loop. Every time I launched this one, it glided. It glided, like something that's built for gliding is suppose to do.

So, now it's just a matter of scaling it up 5 times.

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