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Old May 14, 2006, 10:27 PM
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Laguna Beach, California
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Portable Plane with Ripstop Nylon Wings (70" wingspan)

Here's my new scratch-built plane. I designed it for aerial photography, but wanted it to be small enough to fit on the rear parcel shelf of my MX-5 Miata.

It's got a 70" wingspan, but as you can see from the pics it collapses down pretty small. The fabric collapses like an accordian while on the lower carbon wing spars. When the upper spars are attached the wing pulls out and attaches to nocks on the ends of the spars using shock chord (elasticated thick string).

The airfoil is created by shaped alumium ribs that I slid in to pockets sewn in to the wing. The ends of the rods plug in to kite standoff connectors that slide along the carbon spars.

Two Slow Stick aluminum booms are stuck end to end to create the fuselage. I used magnets to provide linkage between the servo control rods on the two booms. However, it turned out that the magnets weren't strong enough so I'm going to replace them with much stronger ones.

I've got it to fly, but it seems that the rudder isn't big enough for the job. On the two occassions I've flown it so far I had trouble steering at times. That was in 6+ mph wings. I'm going to make the rudder larger. This isn't exactly a fast plane, so at times the airspeed across the rudder must be very low.
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Last edited by LittleJon; May 15, 2006 at 06:55 PM.
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Old May 14, 2006, 10:40 PM
BEC
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Auburn, Washington USA
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Increase the dihedral angle to get better turning on rudder....

Very interesting project!
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Old May 14, 2006, 10:55 PM
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Laguna Beach, California
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Thanks for the suggestion. I've got a fair amount of dihedral. If I remember correctly the holes that the lower carbon wing spars fit in to are drilled at a 4 degree angle. The tension of the bracing lines increases the dihedral further. I could increase the tension on the lines next time to get more. At the moment they're adjustable, but at some point I'll make them fixed.
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Old May 15, 2006, 01:53 PM
BEC
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Auburn, Washington USA
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Somewhere around 6-7 degrees seems to be a good number for most "high wing" types. I was just looking at the in-flight picture and thinking it might need a bit more. This is a review I did of a plane about that same size, but rather heavier.... in it I discuss exactly this question: http://www.rcgroups.com/links/index.php?id=4014
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Old May 16, 2006, 01:45 AM
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Laguna Beach, California
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Thanks for the link. The carbon tubing I used turned out to be stiffer than I expected, so it's not as easy to put a lot of dihedral in as I thought. However, I'm sure I can give it quite a bit more. I certainly didn't have that much tension in the bracing lines for the previous flights.

I'm sure I can easily add another few degrees.
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Old May 16, 2006, 02:17 PM
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Crawley, West Sussex, UK
Joined Jun 2004
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The dihederal is most important at the wing tips (where it's got most leverage), so is OK if just the wing tips bend up. (which is what can happen if you tension the rigging wires)

BTW, that translucent wing looks beautiful in the air!
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Old May 16, 2006, 03:47 PM
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Quote:
Originally Posted by RobinBennett
BTW, that translucent wing looks beautiful in the air!
Thanks, but it attracts insects like you wouldn't believe!
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