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Livermore, CA
Joined Sep 2004
8,430 Posts
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Luckly, a well trimed 24g outrunner WW Boomer, will glide 40ft on a good toss. Butch |
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I've got another question about the horizontal stabilizer. I've started on this 25" chuck glider/boomer conversion and was wondering if there is a prefered placement for the horizontal stab? In looking at the boomers pictured in this thread I've noticed that most of them have the h-stab a couple of inches or more higher than the wing itself. Is there a reason for this?
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Livermore, CA
Joined Sep 2004
8,430 Posts
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In the beginning, the h-stab was wing level, so the tails were more vulnerable to breakage. Next I tried the h-stab on top of the tails, but again the tails were weak at the base and the control rod was longer to reach it. So I decided to put the h-stab about 2/3's up the tails, so anywhere from 1/2-3/4's up seems fine.
Also, I noticed I got more control from the elevator with power at 2/3's, as the prop puts out the most thrust in the outer 1/3rd of the prop. Butch |
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Livermore, CA
Joined Sep 2004
8,430 Posts
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Well I just couldn't wait since I just soldered up the batts for the Micro-Boomer, so I took it out front under the street light on a calm evening.
I did a few glide tests and had to power up to keep it out of the bushes. It was nose heavy and a bit pitch sensitive. I got it close and flew it around a bit. Very sensitive and too fast in the dark. It would fly at under 50% power and the inexpensive 3.7g servos seemed a little step-ie. Its too early to tell, but it seemed like part of the pitch sensitivety was like that of a flat plate wing. The extra wide cord may make it more so. But! It turned out weighing 2.3ozs/65g's and has plenty of power, so maybe a thicker airfoil would be the next step. The wings do need a little stiffining, so extra EPP instead of a spar might be better. I'll post some pics later, Butch |
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Livermore, CA
Joined Sep 2004
8,430 Posts
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I got off work early enough to take the Micro-Boomer out to a grass field, just before dark.
It flys, but not good. It has plenty of power, loops real tight and rolls well. But it would pitch down when pulling out of dives. Luckly it was light enough to see the wings flexed too much. With the angle of the aileron pushrods, the flexing up of the wings would push the ailerons both down and of course pitch the nose down. If I flew it slow and smooth, it did ok, but any abrupt up elevator, caused it to pitch down. The easy fix is a C/F rod, but I may just make a thicker wing. Maybe even hollow, with EPP ribs and a spar. I'll have to think about it. Butch |
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At that size, hollow will save almost nothing in terms of weight. Which is something to toss into the think pot. But it can add some stiffness from the glue joints.
Here's another thought: laminated layers might also be stiffer than just epp. Probably add a hair of weight though, depending on the glue used to make the layers. Two at most, of course, if you're shaping a foil. Dave |
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Livermore, CA
Joined Sep 2004
8,430 Posts
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To stiffen the Micro Boomer's wing, i tried some scotch tape accross the bottom.
That helped, but just not enough. So I ran a piece of kevlar thread from tip to tip. That helped a lot so I took it out saturday morning with the boys, on a nice calm day. It helped a lot, but still not enough. I ended up just adding a .080 CF spar across the bottom. That really stiffened the wing. Flying weight went from 2.3ozs to 2.4ozs. I took it out just now, in a breeze, 3-4mph. It loops and rolls very tight, has great climb, but still I get a slight pitch down when turning into the wind. I think with the large wing cord, the flat-plate airfoil pitchyness, is increased. All in all it flys good. It will fly very slow and still have control at under 50% power. I think I'll get some thin EPP sheet and do a built up wing next. The size, weight, power seems to be about right. Butch |
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