JW60 flight issues - RC Groups
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Nov 16, 2008, 06:34 PM
I land when i CFIT!
flytrip's Avatar
Discussion

JW60 flight issues


I maidened my JW today. In order for it to fly, I had some reflex dialed in.
The problem is, with the reflex set where it is now, it ZOOMS like crazy when I am hands off. In order for it to fly level, the reflex has to be dialed down, but the less reflex, the worse it porpoises. I have it balanced right at the suggested mark, and the bench I built it on is nice and level, so the wing did not get a warp or twist built into it.
What am I missing?

Thanks, Colby.
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Nov 16, 2008, 07:08 PM
I'd Rather Fly
Alex May's Avatar
Sounds like you might have your rates too high on the elevator. Tone down the dual rates a bit.
Nov 16, 2008, 07:11 PM
Circle Jockey
D.S.'s Avatar
What he said.
Also, how does it fly inverted? When you get it trimmed out right and the CG in the right place it should take just a little down stick to fly level while inverted. Sight down the wing from the tip to the fuse to check for wing twist and adjust with a little heat while you twist it the opposite direction if it is tweaked. Your CG is probably off and that will make a plank fly like crap. I see you had the same problem getting the CG right with your Zipper and didn't like the way that one flew at first either. Did you ever get the Zipper sorted out? Do you fly with anybody else with experience flying and trimming plank gliders? A little fine adjustment in the right direction can make a huge difference in the way a plank flys and how much fun you will have flying it.

Dean
Nov 16, 2008, 07:12 PM
Registered User
Daemon's Avatar
Ya, rates too high.
And it may have gone from so much reflex that it was hyperstalling
continuously, to less reflex so it actually started flying proper,
but still had too much up elevator so it now zooms up even
more. Take out more reflex, and dial your elevator rates down.
On a plank like the JW60 your elevator rates could easily end up somewhere
down around 15-20%.

ian
Nov 16, 2008, 07:21 PM
Composites Kid
Alex.Schweig's Avatar
Excuse me, what is "zooming"?
Nov 16, 2008, 07:40 PM
Registered User
Daemon's Avatar
Usually it's "going up, fast".
Of course it could be "going up, fast, then going down, fast".
Advice is pretty much the same, either way.

ian
Nov 16, 2008, 07:56 PM
Registered User
bikeman's Avatar
Sounds like how my Bat flew on it's maiden. Mine was due to servos not centering properly due to drag on the buried control rods. If your rates are in check, check the servos and or linkages.

Mike
Nov 16, 2008, 08:02 PM
Obsessed
screamin' eagle's Avatar
If it needs loads of reflex to fly level at cruising speed, you're noseheavy; and if you're noseheavy you'll need more elevator throw, which in turn will make you hyperstall/porpoise.
Nov 16, 2008, 10:35 PM
gas tires and oil
prplgoat's Avatar
hey colby,
too much elevator throw is probably right-on and i would bet your cg is slightly rearward.
total elevator throw shouldn't be more than 1/4". 1/8 up and 1/8 down.
start there and you may add 1/16" more if you feel it needs it when DSing. tape a 1/2 oz to the nose and try again with these elevator throws and tune from there.
dean is right about the inverted flight. i like the dive test best.
once it is flying ok and trimmed level take it up high and dive at a 45* then neutral the sticks. if it pulls out remove some nose weight. if it tucks under add a little more weight. if it continues at 45* it is perfect! it should fly inverted almost hands off.

marty
Nov 17, 2008, 03:22 AM
isoaritfirst
isoaritfirst's Avatar
Try the loop test to set the elevator throws,

dive down and pull full and immediate up.

Now wind the throws down until it doesn't spin out...
Nov 17, 2008, 03:25 AM
isoaritfirst
isoaritfirst's Avatar
When you have settled on where the nuetral surface is, try this set up technique
http://www.rcmf.co.uk/4um/index.php/topic,65729.0.html
Nov 17, 2008, 01:47 PM
I land when i CFIT!
flytrip's Avatar
OK, thanks for the replies fellas.
I do have the rates set up correctly. Again, it would ZOOM, with too much reflex, and porpoise with less than that. Both of the characteristics would happen, HANDS OFF. I cannot see how there is too much throw, when this happens hands off. I have to assume that my reflex setting is off.

o, as I lessened the reflex, that is when it would start to porpoise. Will the porpoising go away with less reflex? Meaning, do I need to work through the porpoising by decreasing the reflex even more, until it does not zoom or porpoise?

Thanks, Colby
Nov 17, 2008, 02:21 PM
Registered User
Daemon's Avatar
Yes.

ian
Nov 17, 2008, 03:57 PM
isoaritfirst
isoaritfirst's Avatar
Porposiing is caused by the wing stalling.

Too much reflex,
balance at 66mm set surfaces to be level with underside surface of wing, have +-2mm elevator movement activated by as much servo throw as you can muster. Use high quality digital servos, ensure surfaces are hinged accuratly and return to neutral reliably from both sides. If you can't achieve this then rebuild it.
Let the model fly a little bit faster, dont try trimming it up to stay up, push it around the sky only asking it to go up when in strong lift or with speed.
Nov 17, 2008, 06:01 PM
Where's the wind?
the_canuck's Avatar
Quote:
Originally Posted by flytrip
OK, thanks for the replies fellas.
I do have the rates set up correctly. Again, it would ZOOM, with too much reflex, and porpoise with less than that. Both of the characteristics would happen, HANDS OFF.

Planks tend to need to fly fast. Slow them down too much and you get the hyperstall.

If the plank is climbing more as the speed increases you DON'T have the CG correct. (It's nose heavy!) It's only officially tail heavy when the plane tucks at high speed.

The recommended CG is a recomendation only. Consider it a starting point to work from. Start nose heavy (needing alot of reflex which will give mushy controls, mushy flight characteristics, and a tendancy to climb at higher speeds). Work CG back slowly (subtract weight from the nose). Each time you adjust the CG back, reduce your elevator throws 5 - 10% and reduce the reflex 2 - 5%.

When the CG is correct the plank will fly very neutral, no ballooning at high speed and very little stick inverted.

Once the CG is correct, if it still hyperstalls alot your elevator rates are still probably too high. You also need to keep your hands off the elevator unless you are turning or doing loops. A plank flies itself and should require very little elevator manipulation. Adding more up stick will make it fall out of the sky hyperstalling to the ground! If the lift just isn't there. Land and fly something else.

Andrew


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