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Old Aug 29, 2012, 03:51 PM
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Originally Posted by Javatango View Post
So the "caveman" method involves twisting the hell out the wing, eh? I may give that a try.
More or less. When I had the problem with the Bixler I was flying full left AILE to keep it straight. The twist it had in the wing wasnt easily noticable, but the turn was aggressive. The Dynanic-S roll problem is much milder so I don't think a massive adjustment is required. I try and hang all my aircraft up by the tail these days when stored so this problem does not re-occur. Of course I could be completely wrong but I think a laterally balanced aircraft with straight airfoils should fly straight with only minor if any AILE trim input once the setup is correct.

Mick
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Old Aug 29, 2012, 04:49 PM
Earthbound Skyhound
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Something else I've found out about this 'involuntary roll' problem - it's endemic to thin-winged aircraft. I wonder if it's because (in our case; foam) they're easier to warp & concurrently, being thin it doesn't take much, or that they don't provide the lift of thicker airfoils, ie their lift is more precariously balanced on the 'knife edge' figuratively and literally.

I can see if both thin wings aren't aerodynamically synchronized, boundary layer can come off at different times (esp. being thin) as speed increases, and loss of lift on one side equals.....well, you do the math!

About what it all comes down to is, thicker airfoils are more aerodynamically forgiving.
(Methinks!)
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Old Aug 29, 2012, 06:58 PM
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I agree with your comments Starhopper. If the Zephyr wings were sold separately I would be inclined to try and fit it to the Dynamic-S. Its a much more rigid wing which is to far off in size. My friends Dynamic-S flew straight out of the box with any probs I saw appart from the nose rising under power, so I think I'll do some wing twisting this weekend at the field with the Dynamic-S and see what happens. All these cheap foamy's are puzzle games anyhow

Mick
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Old Aug 29, 2012, 11:30 PM
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I wonder if the problem lies with the square carbon between the wings not being set properly on some wings during the build. That would explain why a wing that is perfectly straight to look at could be offer some undesired down or up lift without giving anything away to the naked eye. My other models use a round carbon making them self leveling as you lock the wing down. The Dynamic-S and perhaps the Blaze use square carbon so regardless of the lock down force at the join, the wing could still carry a minor tilt resulting in a turning/rolling aircraft.

Just a thought
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Old Aug 30, 2012, 01:18 AM
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I removed the wing and measured the trailing edges with a set of calipers where they meet the fuse. The right wing comes in at 4mm and the left at 3mm. So when you bolt the wing down it forces the right wing up, leaving the left low which must offer a little right turn input I guess.

Just thinking out loud, in my postings, no outcome yet.
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Old Aug 30, 2012, 11:03 AM
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I seriously doubt that small displacement would cause the kind've disruptions we're seeing. Jeez, if that were so, my ol' banged up Bixler would fly in spirals!!
Think - the channel for the spar tube is molded in, hence there's not much room for it to be misaligned - & what is (the 1mm or so) is likely from the anchoring glue or somesuch displacing it. Plus, the spar itself is about as straight as anything that could be used, & would tend to pull everything back into line, methinks.

Oh - afa warp. Before the test flights I had tried to check that as a potential culprit. We have a large glass-top table out at the field clubhouse & I laid the assembled wings (only) atop that & backed off as far as I could & checked it over, but between the upturned tips on one side, & the aileron linkages on the other, had no way of getting the assy down flat enough to tell. I eyeballed the hell out of 'em tho, & far's I could see everything looked good.

Yet I have the 'peel off' problem.
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Old Aug 30, 2012, 11:30 AM
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Oh, forgot to mention.....
I've got all the control horns (Ails & Elev) removed, prepping for the stiffening project.
FYI you can get a fingernail under a corner of the backing plate & with slow, persistent pressure peel it off from the back, then push the thru-tab out with steady pressure until the horn comes loose. Pretty easy, actually.

I also lightly sanded down all the surfaces, making sure I got all the li'l injection 'grits' smoothed, using 320-grit 3M 'Sandblaster' abrasive foam block; 'works a treat' as they say. I also carefully removed all the small flash-lines of foam on the leading & trailing edges (same sander). Before I started sanding I used a 'chisel' type X-Acto blade to carefully carve away the ahesive remnants where the horns were anchored, plucked the remaining shards with tweezers & cleared the thru-holes as well. I'll stuff those with a couple toothpicks to keep 'em cleared while I varnish & paper-skin the flaps.

While I have everything cleared, I exercised all the hinge-lines per my protocols, starting with the 'push flap forward while half-flexing' all up & down the surface every couple inches, followed by the '50-full-range-flexes' exercise, ending with a 'maximum flex & hold' stretch period (piece of tape holding fully opened, against the seam). I give all those details as, the full process isn't well known, but it really eases up the workload on your servos. Got kinda inventive on my descriptions - hopefully they're graphic enough to make understandable but if not, just ask. The full process leaves hinges pretty relaxed, & less likely to tear.

Speaking of which, good timing on the flexure exercise also as, I discovered the beginnings of a hinge separation on the very inside of one elevator half, hiding right below where the horn anchors. A stitch in time, it'll be! And a final note on that - all this was preparatory to laying on of Dermablend aka 'Hinge Tape' after a good alcohol cleaning. I picked up a roll of 2-inch & will be using that, considering the kinda forces these babies will be subjected to if this fix goes well. The tape will go on first, then the skinning process, & re-fit all the control horns as final stage.

The polycrylic is warming as I type!
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Old Aug 30, 2012, 03:41 PM
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Oh well I'm running out of ideas. So many people don't have this issue, so I guess we are missing something. I think i'll just take it to the field tomorrow, fly it, then assault the wing with my big monkey hands, whilst growling and making other animal sounds.

Mick
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Old Aug 30, 2012, 05:55 PM
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Took the Blaze to my lunchtime field this afternoon and decided to give the left wing a twist. I spent about a minute twisting the wing, then plugged in the battery and gave it a toss. Guess what? I forgot to take out all the left trim in the transmitter. It rolled hard to the left after leaving my hand. I got on the sticks fast and was luckily able to recover, but that got my heartrate going. My transmitter was programmed with 15 clicks of left aileron trim. I eased it out to 5 clicks of left trim and spent the rest of the first flight on easy back and forth passes on 20% thottle just dialing in the trim. A few clicks here, a few clicks there, and it started looking good so I landed the Blaze and looked at my transmitter. I was back at 15 clicks of @#$% left trim!

Turns out that twisting the wing does work, but I either didn't use enough force, or didn't hold it in the twisted position long enough, because it slowly returned to it's original shape thoughout the duration of the flight.

I will be channeling more of my inner caveman during my next outing.
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Old Aug 30, 2012, 06:58 PM
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Originally Posted by Bravo47 View Post
Oh well I'm running out of ideas. So many people don't have this issue, so I guess we are missing something. I think i'll just take it to the field tomorrow, fly it, then assault the wing with my big monkey hands, whilst growling and making other animal sounds.

Mick
Don't forget to fling some dung!
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Old Aug 30, 2012, 08:06 PM
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Don't forget to fling some dung!
Good idea, I'll gather up a pile of kangaroo pellets at the field and toss hand fulls at it if it doesnt yield

@Javatango - If the twisting theory works(and it should). Try taking the wing off at home and resting a small amount of weight on the mid left trailing edge with a book placed under the right wing. Leave it in the sun for half hour. It should stay where it cools. Dont over do it though or you will be trimming right next flight
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Old Aug 30, 2012, 10:26 PM
Knobbs
Friday Harbor, WA -San Juan Island
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I'd almost be happy to be putting right trim in at this point. Anything to not be carrying so much parasitic drag. Can't wait to see how much better it glides without one of the ailerons sticking straight (exaggerating a little) up.

Rishelman
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Old Aug 31, 2012, 06:59 AM
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Woah! I'm getting a differing picture here from what I had in mind y'all were suggesting.
I'd thought like, grabbing the wing near the outer (or inner) end & like, partially 'unscrewing' it a 16th-turn or such & hold it there awhile. Now I'm seeing 'mid left' & 'bookend right' & ....lost me!

Could someone scratch up some diagramming or video or something to show exactly what you're doing here?
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Old Aug 31, 2012, 07:44 AM
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Originally Posted by StarHopper44 View Post
I can see if both thin wings aren't aerodynamically synchronized, boundary layer can come off at different times (esp. being thin) as speed increases, and loss of lift on one side equals.....well, you do the math!
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Originally Posted by Bravo47 View Post
Oh well I'm running out of ideas. So many people don't have this issue, so I guess we are missing something.
Here's another idea for the cause of that left Aileron trim:

The long thin panel of foam that makes up the under side of the wing (covering the spars and servo wires) is sitting proud in most areas on my left wing. In comparison this panel sits nice and flush on the right wing! Take a look at these photos and you will see what I mean.


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Description: Left wing underside leading edge - note raised lip Name: Left wing underside Outboard.jpg
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Description: Left wing underside Outboard of Aileron - note raised lip

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Description: Left wing underside at Aileron - note raised lip Name: Right wing underside at Aileron.jpg
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Description: Right wing underside at Aileron - note flushness

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Description: Left wing underside Inboard of Aileron - note raised lip Name: Right wing underside Inboard.jpg
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Description: Right wing underside Inboard of Aileron - note flushness

Could this additional airfoil thickness on the left wing be generating the extra lift causing that roll to the right?

Anybody else have a left wing that looks like this??
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Old Aug 31, 2012, 07:58 AM
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Oh and I don't believe the thickness of foam panel is to blame. As you know this model is glued together with copious amounts of white silicon rubber like glue. If applied too thickly I could see this glue being difficult to squeeze out from under the panel and might cause the foam panel to sit proud as seen on my left wing.

With difficultly I peeled back the first few inches of the panel from the wing tip end and sure enough found a thick layer of that white rubber underneath (I can upload a photo if any interest). With difficulty I removed some of this sticky rubber glue and was able to press the panel edge down flush.

I don't know what to do next at this point. I would love to remove the panel and rubber glue then refit it using normal thin foam glue, but the panel is quite difficult to remove without damage and the rubber is even harder to remove! If I sand back the panel I'm afraid I may significantly weaken the panel or even break through!

Suggestions?
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