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Old Jun 14, 2012, 11:28 AM
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United States, WA, Port Angeles
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again all I can say is WOW! what a plane!

ok I'm no expert, but I'm pretty shure your gonna wanna move the CoG "rearward" ta make the plane fly lighter!
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Old Jun 14, 2012, 12:48 PM
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well, I can't argue with a real pilot . I can only recount what I've read (heresay) from the internet and from my own experiences in designing model aircraft.

I'd agree with whiskykid, moving the CoG forward will make the plane less responsive. I think you meant to say "less responsive" as you mentioned some pitch instability issues which correlates to a rearward CoG?
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Old Jun 16, 2012, 04:29 AM
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Newport South Wales
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I saw a picture of a Cherokee in the service shop without the wings and was surprised to see how much positive incidence there appeared to be on the main wing.
I built my model with 1 degree positive incidence and after searching the web I found that the full size has 2 degrees positive incidence (this is not indicated in the full size manual)
A further 1 degree of incidence will raise the front of the main wing approximately 7.5 mm (almost 3/8")
This will probably explain the flying characteristics that we have been experiencing.
I must bite the bullet and carve up some areas of the model to rectify this.
Fortunately the construction method for the mounting of the wings to the fuz that I utilised will enable me with some difficulty to change the incidence without any noticable marks on the exterior of the model (I hope !!).
I will make start this morning wish me luck.
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Old Jun 16, 2012, 04:42 AM
Jack of all master of none
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Baltimore MD USA
Joined Jan 2011
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Well Keith given your skill level I think you can pull it off, one thing I use to tell the guys in my shop was you know your good when you can correct a problem and not tell there ever was a problem!! Good Luck with the come back.

Bruce
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Old Jun 16, 2012, 11:33 AM
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I went back in the thread and reviewed the wing-to-fuse attachment. I have all the confidence that you'll tackle this task with more than stunning results.

EJWash
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Old Jun 16, 2012, 11:24 PM
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wow!! are you changing the incidence due to the pitch instability? incidence doesn't play a large roll in pitch stability.
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Old Jun 17, 2012, 01:52 AM
Scale Builder
United States, AZ, Litchfield Park
Joined Jul 2002
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On an airplane with a full flying stab what will you achieve by adding a degree of positive incidence to the main wing? Seems to me all you will be doing is trimming the fuselage to fly slightly more tail high or, basically, adding a degree of down thrust. Am I missing something?
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Old Jun 17, 2012, 12:44 PM
team sleprock
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KPTR: Wing incidence helps turn what would otherwise be an unstable airplane, into a neutral, honest, and predictable one!
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Old Jun 17, 2012, 12:46 PM
Scale Builder
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Quote:
Originally Posted by whiskykid View Post
KPTR: Wing incidence helps turn what would otherwise be an unstable airplane, into a neutral, honest, and predictable one!
How so in this case?
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Old Jun 17, 2012, 01:16 PM
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Quote:
Originally Posted by whiskykid View Post
KPTR: Wing incidence helps turn what would otherwise be an unstable airplane, into a neutral, honest, and predictable one!
I take it that you're referring to this Site:

http://www.rcflightschool.com/

And this lesson in particular:

http://www.rcflightschool.com/Inter_...ter_0A4-13.pdf

EJWash
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Old Jun 17, 2012, 04:53 PM
Biplane Fan
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Keith, what airfoil do you have in your model? Is the same as the real one??
I agree with Chad....it`s a full flying stab, is ot the same as other typical ones....
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Old Jun 18, 2012, 07:07 AM
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Thanks for all your comments.
I do realise that the all moving stabiliser will compensate for variation in main wing incidence. One of the main reasons for making the change is that we needed about 4 degrees up on the stab to maintain level flight.
When flaring for the landing the rear of the model is practically on the deck. Also the model is a bit sluggish to lift off ( this was exagerated to some degree we think by grass in the spats applying effective brakes.
From the overall results to date we wonder if the CofG is not quite right
When the incidence change is completed we plan to critically re-weigh the model and calculate the CogG as per the empty weight of the full size to ensure that the CofG is within spec before test flying again and re-trimming from scratch.
I will report the results in due course.
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Old Jun 18, 2012, 12:10 PM
team sleprock
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ya EJ thats the artical!

didn't want ta hijack the thread! just point out that, allthough 1 deg. doesn't seem like much, it will change the way a plane flys, hopefully in a better way!
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Old Jun 24, 2012, 02:13 PM
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The change to the incidence is completed and there are no visible effects on the model. We have also changed the elevator servo to 15kg Savox digital which should ensure reliable centering of the stabiliser after each movement. The Hitek Hi-torque units do not reliably centre and with the all moving stabiliser very small errors are much more critical than with a conventional stabiliser/elevator.
Due to the terrible weather that we have in the UK at the moment we have not had the oportunity to carry out any further test flights. We hope to be able to take thw model to some place with a much longer runway than we have at our field so that Doug can carry out much more detailed testing and setup the programming to get a more reliable result.
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Old Jul 25, 2012, 10:12 AM
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We took the cherokee down to our own field last evening and just after take off there was a loud bang and the spinner disintegrated Doug brought the model round and landed. we checked her over and everthing appeared ok so we went for a further flight.
It was very clear that the flight characteristics were very significantly improved and the model was very stable inflight and approach to landing.
On the third flight we had a problem with the engine dropping off to idle and had to emergency land in the long grass off the runway area. the airframe and all the oleo legs were undamaged the fork on the nose leg broke off and the spats were slightly damaged. we got away very lightly considering a model of almost 20kgs coming to an abrupt stop in the long grass.
This means we will probably not be able to take the model to the scale meeting at Old Warden this coming weekend.
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