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KastAway |
May '03
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Years ago I've built a hand launch glider from Bridi, not sure if it was the Tercel or Kastaway. I just remember the finger hole at the bottom of the fuse to hand launch the glider (it says on the box "grenade-launch"). That project was never completed. Went as far as covering but never installed the radio equipments. This time, this project almost faced the same fate, but the weather just changed for the better (Spring '03 has been a wild wet one) so I put off completing the WindSurfer 100 (coming soon, heavily modified) and try to get the Kastaway flying. I've started both a few months back, and it's time to get one in the air. I live by foothills here in Fremont, California (south east bay of the San Francisco Bay Area); and I actually have a small slope right in my backyard. There's no landing area to speak off so if I want to fly "at home", I will need a small hand launch variety. The Kastaway seems to be the perfect candidate. As I was hunting around the country for vintage Bridi glider kits, I did get a few for the collection. The only issue is wind; since the backyard slope faces south west, I usually get sinking air since the wind mostly comes from north west. Once in a while, a perfect south-west wind would come... I find myself logging in to this USGS wind page quite a bit lately. The Kastaway features (some from the box):
Kit and building Comments: The Kastaway features a thin modified 205 airfoil, which would mean better penetration for slope flying. It's possible to build this kit with standard servos, but I chose some micros for the light wind days - also the chance of catching some thermals. The one piece bolt-on wing is a bit bulky for transportation, but at 1.5m it's not too bad. I was contemplating a two piece modification but that would add weight so it was built almost as the plan calls for (with one modification, guess?) Another Bridi kit with "word only" building instructions (no pictures). The "Easy Assembly" claim is almost true, this is a simpler plan to build than other Bridi gliders. Die-Cut wing ribs and solid horizontal and vertical stabs. The stabs are very thin (1/8") so the "monokote" hinge technique is used (strips of covering material as hinges). I just use clear packaging adhesive tape for the hinges. Note: In my opinion, the tail skid does not go down enough to keep the vertical stab from dragging the ground on landing, so add another 1/4" or so. Modifications: Yes, those winglets. No stick construction this time, a solid 1/8" piece cut to shape with flat bottom airfoil for each winglet. The outer panels dihedral was lowered by 1". The winglets were built with about 1 degree "twist" to the outside and about 30 degree "toe" out. Supposedly the twist out effect is similar to washout to help with tip-stalling. Please note that I do this by "cut and look", no airfoil calculations here. I just want the cool look of winglets. The fuse, stabs, winglets, and control surfaces were painted. Decided for transparent red monokote for the back half of the wing (showing off the ribs). Since this is a smaller model, I decided to paint the control surfaces dark blue to help me with orientation. The bright yellow fuse and winglets should be visible for quite a way. Note on flying: I'm trying to build an altimeter recorder for my gliders. But that is usually after-the-fact numbers. I've always wanted a way to estimate the height of my gliders. Especially when it's reaching "speck" altitude. How high is it? I've found out a quick trigonometry calculations using the tip of my antenna as a guide. As I hold up the radio to have the antenna approximately pointing in the direction of the glider, when I see the entire wing span or the glider just fit inside the tip of the antenna (about 1 cm in diameter), I can guestimate the distance of the glider from me. So, for a 1.5m wing span and a 1cm antenna tip, how does it work out? The following math is approximate for small angle, assuming sin(theta) = theta; also with a 1m length antenna.
As it worked out with my approximate dimensions, just multiply the wing span by ratio of antenna length to antenna tip diameter (in this case 100). I hope my high school trig hasn't failed me, it's more than 25 years since I took that class... ;-) Of course, this is just the distance away, actual height will depend on how far off the direct "straight up" line of sight (another angle, I'll leave that calculation to you...) Some pictures of the completed glider, sorry no construction photos (couldn't find them).
Flying Update... She will fly with the lightest of lift, catching thermals is made easier since the response is inherently more twitchy with the smaller wing, you can spot those mini thermals and small lift areas. However, the true test came with a high wind slope. I took the Kastaway to one of the local gem, Coyote Hills (aka. heart attack hills, the nick name came from the fairly steep climb to the slope, limiting this site to the younger croud). After adding almost half a pound of ballast, she darts around the sky in 20mph wind with the other foamie wings (zagis) with ease. Of course with just rudder and elevator, she can't do the rolls as the aileron equipped flying wings. But for this day, she was the coolest looking craft on the slope (me bias...). I set up the control throws to maximum deflection and she will almost turn on the tip of the wing. Although not a recommended plane for a beginner, the Kastaway is equally comfortable catching lazy thermals as zipping around on the slope. True to its (modifed) 205 airfoil.
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