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  #41  
Old 04-22-2019, 08:31 AM
aeppel_cpm aeppel_cpm is offline
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Okay glider fliers, I would like opinions:

It took 7g of wingtip clay to trim the left roll out of my glider. Would I be better off with the lump of clay on the wingtip, or making an aileron?

My thought is that they would behave nominally the same during glide, but may behave quite differently during boost.
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  #42  
Old 04-22-2019, 08:39 AM
jetlag jetlag is offline
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ALWAYS achieve the balance of the aircraft first.
Then can use a little aileron. You may find a little rudder is all that is needed.
If you use only aileron to correct roll, the effect magnifies as the craft increases airspeed. Increasing your dihedral is another way to make the aircraft seek level flight. If you need more lift, either slide the wing forward a little (if possible) or increase the wing leading edge angle of attack slightly. It's important to do only one adjustment at a time, so you can tell immediately whether the one adjustment you performed worked.
Balance first. Then test fly.

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  #43  
Old 04-23-2019, 07:09 AM
aeppel_cpm aeppel_cpm is offline
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Thanks for the guidance, jetlag.
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  #44  
Old 04-23-2019, 09:50 AM
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+1 to what jetlag just said.
Balance first, aileron/rudder second.
That thing sure is requiring a LOT of weight though.
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  #45  
Old 04-23-2019, 10:12 AM
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Quote:
Originally Posted by ghrocketman
+1 to what jetlag just said.
Balance first, aileron/rudder second.
That thing sure is requiring a LOT of weight though.



Yeah, that was my first thought. 19g...........almost 3/4 oz. Yikes! Any suggestions as to how to correct the problems without adding so much weight? I'm particularly interested in this thread because I built a couple of gliders last year and have done test glides, but I still haven't gotten up the nerve to boost them.


Joe
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  #46  
Old 04-23-2019, 10:23 AM
aeppel_cpm aeppel_cpm is offline
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Recall, it started off at 200g.

Given that I'm upscaling a Tercel, I don't know that I could have done much to make the fore-aft balance better. I don't think the tail is -that- overbuilt, or that the RC horns are adding that much weight. I think it's part of the design and upscaling it just amplified the noseweight needed. That said, I noticed after testing that I had left a little up elevator trim in the servos from the last test. So it probably doesn't need -quite- 12g up front.

The 7g on the wingtip bothers me more. I sanded my own airfoils out of foamcore and then laminated 1/32" balsa over them. I suspect that I just ended up unsymmetrical in either the original sanding, or in the lamination (it was vacuum bagged) and that the angle of attack is different left vs right. And that's just poor construction skills on my part. To my defense, it -is- my first attempt at a glider this size, or using these techniques. I didn't want to spend the money on a kit, so I scratch built, and am suffering the consequences. Though I did enjoy most of the build itself.
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  #47  
Old 04-23-2019, 10:47 AM
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How about "lightening" the heavy wing tip ?
Punch holes in the solid material near the tip then cover with Monokote ?
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  #48  
Old 04-23-2019, 10:55 AM
aeppel_cpm aeppel_cpm is offline
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From the hang tests, I don't think the other wingtip is actually heavy - I think I've got a differential lift problem. Which will vary with airspeed.

I don't know that I can take out 7g and leave much of the other wingtip remaining :-)
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  #49  
Old 04-23-2019, 01:30 PM
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You might be surprised.
7g is just 1/4 ounce. GH is right. You can lighten the heavy side, then use less weight on the light side. Your weight difference most probably is due to variation in the balsa density. 1/4 ounce could easily be due to this issue.
Correct one thing at a time. Get that right. Then see what else can be done.
Please let us know how it goes!
I'd be happy to trim it for you, but you'd have to send it to me.
Good Luck!
Allen
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  #50  
Old 05-04-2019, 02:38 PM
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Quote:
Originally Posted by LeeR
Another option is a heat gun. It works well, with moisture, to get parts straight. If clamping is difficult, you may even be able to hold it for a few minutes in the correct position long enough for cooling to cause it to set in its new position.

If you donít have a heat gun, you can get them for as little as $10 at Harbor Freight, using a 20% off coupon.
Yes--model HLG (Hand-Launched Glider) and catapult glider books recommend using the hot steam (which is really hot water vapor--the true steam is the narrow, invisible portion of the plume closest to a spout) from a tea kettle's spout, combined with gently bending (or twisting, if that's the problem) a warped balsa or basswood part in the direction opposite the warp, until it is straight. (*Deliberately* steam-warping fins has also been recommended for clustered-motor models, to induce a little spin--which evens out slight thrust line misalignments and/or thrust variations between the motors--during powered ascent.) Also:

Stove-top--for gas or electric stoves--tea kettles with narrow-aperture, whistling spout lids (which are opened for pouring out the hot water using an included finger "trigger" on the kettle handle) provide a narrow stream of steam and (above the steam) hot water vapor, which is ideal for such work. If the area of warpage is larger, the stream from the kettle is wider farther from the whistle aperture; one can use whatever height above the aperture that "blankets" the warped area. If the warp is very long, it can be 'steamed and straightened' in sections, until the entire warp is straightened out.
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