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  #11  
Old 10-16-2005, 11:38 PM
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surdumil surdumil is offline
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I finished off the final details and the X-21 is complete (except for glide trimming). This includes some tidbits that aren't included in the assembly drawings/instructions or in the Semroc parts set. I hope Craig at Semroc will note the elevon release clip and elevon control stop notes below, or will suggest better alternatives.

For the elevon tension cord I used about 4 1/2 inches of elastic thread. I cut slits in the elevons instead of poking holes. I thought this would ease thread replacement.

I used black sewing thread for the neutral elevon release. I poked holes for this and used a sewing needle to insert the thread into the holes, securing the thread in place with square knots bolstered by surgeons knots.

I was a little stumped for a while regarding the release clip, but found a solution that seems to work well. The X-21 instructions give no details to work from, so here's my suggestion. Get an empty soda can. You know that piece of metal that gets pushed and folded into the can when you pull the tab to open the can? That's the piece of metal that keeps the drinking hole sealed until the can is opened. Get that piece out of the can. Cut a 1/8-inch wide, 3/4-inch long strip from this piece. Cut the corners off of one end of the strip, giving you a pointed end. Bend about 1/16" to 3/32" of the other end of the strip over, but not completely over. Slip the center of the eleveon release thread under this end of the strip and crimp the end over the thread. Voila, a crimped elevon release clip.

I formed control stops out of a straightened-out metal paper clip, adding zig-zags that lay flat against the wing to stop that part of the control stop from twisting when adjusting elevon height.

I gave the rocket a swing test, prepped with a B6-2 motor, and found that the model is stable without needing extra nose weight. I suspect the custom-turned nose is a bit more massive than the original nose.

All that needs doing is to do some glide testing and adjust the control stops for a hand-tossed flat glide. Then, wahoo!!!! Launch time!
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  #12  
Old 10-17-2005, 12:28 AM
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Quote:
Originally Posted by surdumil
I hope Craig at Semroc will note the elevon release clip and elevon control stop notes below, or will suggest better alternatives...


If only Craig DID work at SEMROC!

You know something I don't???
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  #13  
Old 10-17-2005, 01:11 AM
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Doh!

Sorry Craig. I meant Carl. (I think?)
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  #14  
Old 10-23-2005, 12:50 AM
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Today, the wind dropped down to around zero km/h. What a perfect launch day! I prepped the X-21 with an A8-3. Attached is an image of the X-21 on the launch pad, to give you an idea of the size of it... pretty bad picture though. I need a better digital camera.

The X-21's boost was very straight and very quick. Despite all that balsa, she's a very light bird. Transition to glide was smooth and graceful. The glide was quite flat, with a moderate right spiral. I'd like to open the turn up a bit next time with some adjustments to the elevon stop wires. The landing was gentle and flat.

I was going to send it up again with a B4-2, but as I was tensioning the elevon hold-down thread, the thread snapped. I think the clip nicked the thread or cut through it. I had no thread on hand, so had to put the X-21 away for the day.

A SAROS launch is scheduled for tomorrow. If the wind is acceptable, I can try another flight then.

Pretty cruddy image, eh? I need a better digital camera!
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  #15  
Old 10-23-2005, 10:23 AM
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Quote:
Originally Posted by surdumil
The X-21's boost was very straight and very quick. Despite all that balsa, she's a very light bird. Transition to glide was smooth and graceful. The glide was quite flat, with a moderate right spiral. I'd like to open the turn up a bit next time with some adjustments to the elevon stop wires. The landing was gentle and flat.

Thanks for the flight report!

Now, let's put a grasshopper in the payload section for the next flight to see how she glides then.
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