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Old Jul 15, 2012, 08:51 PM
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Herb, I've been going thru pg 1-46 of the posts, and don't see any advice on the vortex generators. I was wondering if you recommend putting those on for problems with stall characteristics of the wing. I know it's only a rc airplane, but wondered if it might help out by having them on.
Your opinion, and any install tips? Shapes, easy designs?
Really appreciate all your input ove rthe building and updating of your 45, hope mine is going to fly as well as yours!
Thanks again!
Steve
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Old Jul 16, 2012, 03:33 AM
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mongo, search "wing fence" you will get details of location and design
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Old Jul 16, 2012, 12:22 PM
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Quote:
Originally Posted by mongo ea6b View Post
... vortex generators. I was wondering if you recommend putting those on for problems with stall characteristics of the wing. I know it's only a rc airplane, but wondered if it might help out by having them on.
Your opinion, and any install tips? Shapes, easy designs? ...
Hi Steve, I would not try to fly a Hawk without wing fences, every half-decent kit (edf or turbine) has them too for good reason. Besides the CMP T-45 wing has no washout, whereas say the flyfly one has.

http://www.rcgroups.com/forums/showp...postcount=1007

I installed Hawk-style wing fences on mine, those T-45 style stubby VG generators are tiny and I doubt they do anything useful in a model - besides causing extra drag. But I could be wrong

So in view of the generally vicious stall characteristic of the CMP wing I would try to keep this particular T-45/Hawk LIGHT.
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Old Jul 17, 2012, 06:32 AM
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Thanks for everyone's input, makes this much more enjoyable!
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Old Jul 17, 2012, 09:08 AM
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Wikipedia also gives a nice overview of the function and purpose of wing fences that I found useful. After looking at the picture of the SU-22, it made me think about putting a second one on their since the hawk is so prone to tip stalls!
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Old Jul 17, 2012, 12:44 PM
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... the FlyFly Hawk has a nice wing twist (washout), that's how the CMP T-45 / Hawk's wing should have been designed There is zero washout in the CMP wing.

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Old Jul 17, 2012, 11:27 PM
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Quote:
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... the FlyFly Hawk has a nice wing twist (washout), that's how the CMP T-45 / Hawk's wing should have been designed There is zero washout in the CMP wing.

.
herb,

can you point our were is the wash out on the wing. I can only see the wing fences.
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Old Jul 18, 2012, 02:16 AM
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Boostoman go get your glasses

And look at the trailing edge line vs the leading edge line... the washout is continuous, e.g. from the root to the tip.
Which typically makes the build of a wing more complicated, more expensive and therefore rare in models
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Old Jul 18, 2012, 03:34 AM
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You only need to pack the trailing edge up when laying the wing out and voila washout. Not rocket science and easy if the jig is set up for it, not much harder than a straight wing jig.
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Old Jul 18, 2012, 07:07 AM
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no rocket science for sure... but a bit more complicated still...

You could have a twisted spar(s), good luck with that!
Or the ribs have to be very carefully angled to the spar(s). Or most probably shaped to the washout Then the skin has to be worked on a 3 iso 2 dimensional pattern.
To make the matter slightly more challenging, most real A/C don't have a linear washout. Many a designer goes for the washout to be more pronounced behind the ailerons to alleviate tip stall, and less pronounced at the roots to provoke a warning buffeting in that area, though I guess this part does not apply to models (yet)

Probably explains why HK et al don't have it on theirs...
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Old Jul 18, 2012, 12:58 PM
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They could have had washout in the wing ... it's not that hard, they just need to build the wing in a suitable mold, with ribs tied down with rubber bands until the glue sets.

I think they (CMP) maybe figured it would be nice in the Hawk but not necessary ? Most straight wing planes (ie warbirds) don't really need it.

Just a little bit of washout is needed in the Hawk, not much. I can see the difference in the slow flying characteristic between the FlyFly and the CMP Hawk, it really has an effect ! The FlyFly Hawk is rock solid at slow speed, the CMP one is ready to flip over. Washout is easier to do in an aluminum mold for foam.

.
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Old Jul 18, 2012, 01:12 PM
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Wouldn't flying around w/ a little bit of reflex in the ailerons also create washout? I know people w/ the Eflite hawk who have done that.
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Old Jul 18, 2012, 01:23 PM
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... Yes that has a similar effect, "poor man's version" of washout

The wing airfoil isn't just as clean then ...
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Old Jul 18, 2012, 03:47 PM
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Herb

may I ask the RTF weight of your Fly Fly hawk and the set up
I'm Just finishing mine which I covered with tissue and finish
cure epoxy .
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Old Jul 18, 2012, 04:47 PM
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Thanks Herb! I'll probably put in a little reflex... I'm hoping to maiden soon. I may hit you up w/ some questions about my LVC and my ESC. My Turnigy Superbrain 80A appears to have it low voltage cut-off during some bench testing I haven't had to a chance to trouble shoot due to my work schedule... I hate it when that gets in the way
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