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Airfoil for a p-51 Mustang

Old 11-19-2010, 12:29 PM
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MFK
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Default Airfoil for a p-51 Mustang

I am in the planning stage of building a p51. I am starting with the plans from an old Guillow's kit (905).
So far I have up-scaled the plans by X2, and now looking into how I want to build a good flying RC aircraft.
After studying the plans, I found that the airfoil seems to be a Clark Y. This would be ok[&o] for free flight, but I would like this to fly more scale like, with decent aerobatics in mind.

I would like some input into what airfoil would work best for this aircraft.

Wing span 34"

Old 11-19-2010, 12:34 PM
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Tall Paul
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Default RE: Airfoil for a p-51 Mustang

For that size, Clark-Y would be fine.
Note a true Clark-Y is very similar to the NACA 2412.
Old 11-19-2010, 02:36 PM
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MFK
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Default RE: Airfoil for a p-51 Mustang

The airfoil on the plans are flatter on the bottom. From what I can tell (with out looking it up) The NACA 25411, you show, looks like it may work for me.
Old 11-19-2010, 07:10 PM
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CoosBayLumber
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Default RE: Airfoil for a p-51 Mustang

The full sized aircraft had a couple of different laminar flow airfoils. One for straight and the not straight L.E.

Is best to ask your Q at the aero forum here.


Wm.
Old 11-20-2010, 01:07 PM
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PizzaMan
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Default RE: Airfoil for a p-51 Mustang

Your Guillow's kit has a flat-bottomed airfoil that makes it easier to build. For RC aerobatics, I would go more toward a symmetrical or semi-symmetrical (curved on both top and bottom) airfoil. Fully symmetrical airfoils make for better aerobatics; however, my definition of aerobatics and yours might be different. For more scale type aerobatics, a nice semi-symmetrical wing should provide you with what you want. These are also fairly easy to build. The Clark-Y is a nice airfoil.

I wouldn't use the full sized P51 airfoil because airfoils don't scale down that far (only 36") very well. However, I've attached drawings of these for your reference. The first is what was used at the root, and the second is what was used at the tip.
Old 11-20-2010, 05:41 PM
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BMatthews
 
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Default RE: Airfoil for a p-51 Mustang

Keep in mind that the structure of the rubber model is going to be totally inadequite for your new size. You're going to need to totally redesign everything to make it suitable for the new size. Basically all the plans are good for is the outlines and fuselage formers. The tail surfaces aren't TOO bad but you'll want more ribs or just make them from solid 1/8 sheet.

Go with a symetrical airfoil on the wing. The Selig 8020 is a symetrical airfoil that was originally intended for good performance on full flying glider stabilizers. As a result it is optimized for lower reynolds number performance. And on a 34 inch model that's what you have so the airfoil would be a good match for the model. Set the trust line for the motor and the stabilizer at 0-0 degrees to the center line and set the wing at +1 to +1.5. This should prove to work out quite well. In the end you may find that you want to shim the motor for a degree or so of downthrust but if you try shifting the CG back to where the model is "groovy" in pitch rather than trainer like and wanting to pull up sharply on it's own from dives then you should not need any added downthrust.
Old 11-20-2010, 08:13 PM
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racer639
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Default RE: Airfoil for a p-51 Mustang

I have flown several models this past summer with the scale P-51 airfoil on 40" spans composite plane I used in combat they flew very well and were extemely fast, they had no bad habits at all, most negative comments about the scale wing are from people who have never actually flown a model with the scale airfoil
Old 12-05-2010, 09:16 AM
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Default RE: Airfoil for a p-51 Mustang

There are so many plans for the P-51 available I don't know why you would want to scale up a rubber powered model.  They are all a compromise for ease of building and flying with light weight.

good luck!

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