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Old Sep 07, 2012, 12:43 PM
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Joel K. Scholz's Avatar
Kingsland, Texas USA
Joined Aug 2000
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5 Foot EPP Foam Kestral

I have been reading the threads on the foam Peregrine bird and Eagle airplanes, and it has inspired me to attempt one of my own. This one will use an eppler 128 airfoil and be cut from 1.9 oz EPP. I might have use another flying wing type foil. but that would require me making a whole new set of templates for my foam cutter. Instead of starting from scratch, I will utilize some templates used to make my Sharkey's wing
http://www.rcgroups.com/forums/showthread.php?t=1021602
Here is a preliminary drawing. I am still in the process of making some design choices. I believe a downward facing V tail may be more realistic, but will be vunerable in landings.
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Old Sep 07, 2012, 02:03 PM
skumgummi dave
Gresham, OR.
Joined Mar 2004
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Joel:

I like the look of your preliminary drawing. I'll be lurking...

Dave-
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Old Sep 07, 2012, 03:41 PM
Smells like SCIENCE!!!
ibillwilson's Avatar
Canada, ON, Toronto
Joined Jun 2012
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Sweet. I just decided a couple of hours ago to add a soaring bird-of-prey to my must-build list, and briefly considered the kestrel... but instead chose the red-tailed hawk because. I'm still really interested in what you're going to do though. I look forward to your design/build/maiden progress!
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Old Sep 07, 2012, 07:11 PM
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Joel K. Scholz's Avatar
Kingsland, Texas USA
Joined Aug 2000
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Progress today. I got the 4 cores cut and roughed out the wingtips. Used Dupont 77 spray to lightly attach printout of the wing to cores. Next step will be to chop cut the core ends to the proper angles. Debating how to cover the foam for painting. Had originally thought of using craft paper, but fear it may cause warps. Probably go with fiberglass. The great thing about epp, almost nothing chemical wise seems to effect it.
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Old Sep 09, 2012, 02:19 PM
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Kingsland, Texas USA
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Wing is now more or less complete. I made a few modifications to simplify the build and save on materials. Wing is now around 58 1/2 inches, 5.6 oz. The ailerons were decreased in size somewhat and simplified. I am looking more for a realistic bird flight than aerobatic. Used flat carbon to strengthen the span. I also decreased the angles of the polyhedral somwhat. I am debating on whether to alter the design to become a Peregrine as this will make it easier to have a more or less scale beak using a spinner. I am a bit concerned the narrow tips may lead to a tip stall tendency, but if the weight is kept down feel it will be manageable.
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Old Sep 09, 2012, 08:13 PM
Smells like SCIENCE!!!
ibillwilson's Avatar
Canada, ON, Toronto
Joined Jun 2012
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Looking good! This will be one huge kestrel... A switch to peregrine might make sense from that perspective. The wing shape is even close.

To prevent tip stalling, you might consider adding a strip to the bottom of the leading edge for the outermost panels... You could consider it a leading edge droop, or maybe a partial KFm1 airfoil. You can also shape the tips so they have washout, and perhaps reflex the ailerons a bit.

I can't wait to see how this turns out!
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Old Sep 09, 2012, 10:50 PM
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I built 2 degrees of washout into the tips. Hopefully that will suffice.
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Last edited by Joel K. Scholz; Sep 11, 2012 at 11:35 AM.
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Old Sep 11, 2012, 11:06 AM
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Joel K. Scholz's Avatar
Kingsland, Texas USA
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Progress yesterday. I tried using gap filling Elmers carpenter filler on the top wing to make painting easier. It added about 2 oz so I don't think I will use it on the bottom . I have been trying to figure out how to conceal the motor and still make it interchageable and accessible. This is the best I could come up with. It will be difficlt to replace the motor should the need arise, but not impossible. I am using a 250 watt Dualsky I had laying around. Dualsky motors are the best I have found in my 12 years experimenting with electric flight. I have yet to burn one up. I have shaped and roughed in fuselage (body) and today I will make the tail feathers and start installing the electronics. I plan on using a folding propeller, and all I can find is an old aeronaut. I cant find the proper size propeller yoke, so initail flights (if it flys) will be with a fixed prop.
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Old Sep 11, 2012, 02:06 PM
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birdofplay's Avatar
United States, IN, Indianapolis
Joined Dec 2005
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Heres another pic of my local Kestral.

Bob
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Old Sep 11, 2012, 04:13 PM
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Joel K. Scholz's Avatar
Kingsland, Texas USA
Joined Aug 2000
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Thanks Bob, picture are always helpful . Here are a few photos of progress so far today. I redesign the hing line on the tail as I didn't like the large gap needed for the original.
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Old Sep 11, 2012, 09:14 PM
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G-LO's Avatar
Va.Beach VA.
Joined Aug 2007
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Joel, you are a man after my own hart! I'm glad someone made a larger version of the Peregrine.

I have purchased a bata prototype from Lee Aston. I have to say it looks pretty good. He had three left I think. Unlike me, I'm glad you have experience in cutting foam. I am very interested in your building. I somewhat trying to finish my falcon. It so hard to figure out how to "I " want to place my electronics. I hope I can glean some idea from you as you progress. I have ALWAYS Loved bird planes. It seems the Only thing I rather fly is a bird plane...can't help it I guess.

Looking forward to seeing more of your project*
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Old Sep 12, 2012, 02:00 AM
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This looks very interesting! Please let us know how it performs in the air both with and without throttle, Im very interested in a birdplane that's able to glide and thermal aswell. Do you think this airfoil is good enough for sloping without motor aid?
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Old Sep 12, 2012, 08:48 AM
Smells like SCIENCE!!!
ibillwilson's Avatar
Canada, ON, Toronto
Joined Jun 2012
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Quote:
Originally Posted by Joel K. Scholz View Post
Thanks Bob, picture are always helpful . Here are a few photos of progress so far today. I redesign the hing line on the tail as I didn't like the large gap needed for the original.
It' looking good... Nice work! And fast!! I've never built anything with this much detail, yet I'm still much slower... A testament to your building skills.

Really looking forward to first flight, hopefully with video...
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Old Sep 12, 2012, 09:40 AM
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Joel K. Scholz's Avatar
Kingsland, Texas USA
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Regarding the glider abilities. I am estimating the wingloadinrg as somewhere between 9 and 10 oz. psf. which puts it well within the glider wingloading range. The eppler airfoil I used by default is not a glider type foil. It is a high lift low drag foil. Assuming it flys , it will probably have decent glide characteristics, Whether or not it will thermal remains to be seen. It is not exactly a low drag setup, the foils are relatively crude. Progress is definitely going to slow as the motor I built the body around is not running properly and I wont be able to get another for 10 days or more.I'm bummed. I may switch motors and rebuild. I wish I could find a smaller spinner. One that was more to scale, but I don't think it exist.
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Old Sep 12, 2012, 10:11 AM
Smells like SCIENCE!!!
ibillwilson's Avatar
Canada, ON, Toronto
Joined Jun 2012
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Oh, too bad about the motor... you're so close to finishing!

About the spinner... why don't you just use a collet or set-screw prop adapter that already has a spinner on it? Those spinners tend to be relatively small already and I bet it would look pretty scale. You could probably even paint it.
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