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Author Topic: 60% Reduction in Size  (Read 965 times)
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USch
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« Reply #25 on: July 26, 2017, 03:13:40 PM »

I would define it a bit different. Look at the second pic, which seems similar to a Bubble Dancer, it is not the tailplane moving forward, it's the fin which moved behind the fuselage. Look at the boom length....

Urs
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kukailimoku
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« Reply #26 on: July 26, 2017, 03:22:11 PM »

I agree but my hope is to not extend anything further back than it already is to avoid having to add extra weight in the nose to pull the CG back into place. Moving something forward would make it better than it currently is.
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USch
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« Reply #27 on: July 26, 2017, 04:34:43 PM »

That's ok for the mass balance but less for the aerodynamic behaving. You are already short on tail-boom length, so further reducing means even less controlling power. Your model is very short coupled, maybe you have to heavy a tailplane or fin or both, because to get the CG right the nose length seems more than adequate looking at the photo's.

Urs
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kukailimoku
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« Reply #28 on: July 26, 2017, 05:20:45 PM »

The overall length is a stock Oly 650 so I'm thinking I've got some wiggle room, we'll see.
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OZPAF
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« Reply #29 on: July 27, 2017, 07:55:26 PM »

My preference would be to leave the stab where it is and move the fin if you need to. This would maintain your pitch stability which I think is more important than losing a small amount of rudder authority. Rudder power should be ample in any case with the small size and inertia of this model.

John
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kukailimoku
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« Reply #30 on: July 27, 2017, 09:11:31 PM »

That's what I settled on as well. The change in nose weight for getting the CG right would be minimal but the whole setup would be easier to build and a lot more durable. Thanks for the input!
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kukailimoku
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« Reply #31 on: July 31, 2017, 02:17:40 PM »

Nearly done, just waiting for the hinges to arrive. This is what the final configuration should look like (the rudder isn't attached yet, but that's my planned location). Clothespin included to give a bit of scale.

I found an old spare soft diving weight back in a corner with all the SCUBA and snorkel stuff and had an epiphany. Not needing it, I sliced it open and now have about a zillion 1/16" lead balls to use to make CG locations as perfect as possible. Yay me. You can get such a thing on Amazon for under $10 and pretty much be set for lead forever.

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OZPAF
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« Reply #32 on: July 31, 2017, 07:47:51 PM »

That's a large peg Smiley

John
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kukailimoku
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« Reply #33 on: July 31, 2017, 07:50:04 PM »

Resist.

Bad.

Genital.

Joke.

 Lips sealed
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kukailimoku
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« Reply #34 on: August 07, 2017, 01:57:55 PM »

Final configuration with the new positioning of the vertical stab. Dang near ready to fly (having a job gets in the way).

I want to thank my sponsors, Pacifico beer Herradura Anejo tequila. Without their inspiration sailplanes remain grounded.

 Grin

(And that's not a peg. It's the back screw for a wooden clamp I got from my grandfather that's got to be somewhere around 100 years old by now. It still gets a lot of use.)
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kukailimoku
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« Reply #35 on: August 14, 2017, 01:40:32 PM »

It lives (sorta). With all the tinkering and re-tinkering (I think this is tail section #5) I went ahead and re-covered it. I'm ready to get it airborne to see if it flies at all but the CG is a challenge and I'm taping lead solder to the nose for the test flying. If it works I'll extend the beak to get the leverage necessary to do it less Flintstone-like.

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kukailimoku
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« Reply #36 on: August 21, 2017, 02:22:19 PM »

Confucious say...if you're ready to do some trim flying the tradewinds shall boom and water shall fall from the sky. Until you don't have time any more and then it will be a glorious Hawaiian day. Argh.

Looking for thoughts on this: with the regular Oly 650 fuse length I've got to add enough weight in the nose to defeat a lot of the lightening that I've done. I'm considering extending the beak out a couple inches for better leverage/less tonnage. I can't think of any reason not to...is there one?
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kukailimoku
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« Reply #37 on: August 28, 2017, 02:02:41 PM »

A very interesting trimming session and I've got it nice and flat in the air now. It's not quite as floaty as I thought it would be but handles exactly like its big brother. I was concerned about the overall weight and thought I would need to extend the nose as I was working off the Oly 650 CG location which is pretty much right on the spars. Not this little guy, it was well back of there, nearly an inch. I was able to peel more and more weight off the beak to get it perfectly balanced and ended up with a surprisingly light finished bird.

And then, of course, the wind blew strong and sideways. Sigh.
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