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Old May 09, 2012, 09:59 AM
Registered User
Canada, ON, Newmarket
Joined Dec 2005
105 Posts
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Mini hawk pusher - tip stall issue

I built a mini hawk for fun and it flies really well except for one problem. It has a nasty tip-stall issue when slowing down for a landing. The model is based on a 3-view drawing and is 100% scale in terms of overall size. The wing is a flat bottom with a basic airfoil sanded on the top. Where should I start to look to resolve the issue.
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Old May 09, 2012, 04:31 PM
Registered User
Canada, ON, Newmarket
Joined Dec 2005
105 Posts
Anyone....

Anyone....


Buler..................
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Old May 09, 2012, 11:40 PM
Fremont, CA
United States, CA, Fremont
Joined Jan 2009
1,617 Posts
It's not a glider, so you must land at relatively high speed. One wing will naturally stall before the other. If you really want to come in slower, you might try twisting the wing tips leading edge downwards.
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Old May 10, 2012, 04:25 AM
Gravity Sucks
Somewhere in the Nations Capital
Joined Sep 2007
51 Posts
Hi gdimonte,

being a jet and since you have indicated that you used scale proportions, this will likely be an airspeed thing as mentioned above. A sanded airfoil may not produce sufficient lift at low (or even just reduced) airspeeds. You may need to review your wing (span, area and/or airfoil). Also with a pusher config, keep in mind you won't havethe prop blowing air over the wing and helping to generate lift. Are your controls mussy on approach?

Lots of the hawks modelled have an enlarged (i.e. non-scale) wing to achieve suitable flying characteristics. Also, the real hawk has wing fences on the LE about 2/3 of the way out. My understanding is that they work to stop exactly the type of thing you are descibing.

Try having a look at these 2 threads by Nitro.

http://www.rcgroups.com/forums/showthread.php?t=689156
http://www.rcgroups.com/forums/showthread.php?t=1386094

He has a fantastic looking and flying mini EDF hawk. He has a built up airfoil and has the wing fences. I think his wing may have been enlarged too (IIRC).

Good luck with it. It's a great looking little model and hope you get it sorted. If nothing else, just fly it WOT and like you stole it - that should fix things!
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Old May 10, 2012, 03:36 PM
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Canada, ON, Newmarket
Joined Dec 2005
105 Posts
Thanks for the input. I'm going to play around with a larger wing area and see what I get. In the mean time, I'm going to knock-off a couple of airframes to play with.
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