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Old Oct 21, 2009, 12:42 AM
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Best airfoil for quarter scale P-38 Lighning


Looking for airfoil recommendation for slope soaring quarter scale P-38 Lightning to be used in the next Soar Utah which will be next year. The wing root is about 16 inches. Anyone out there recommend an airfoil to use? Weight will be 27 to 30 lbs. This will be Dave Nash's airplane. His last airfoil was either a 60-60 or 60-61. This may not be a very good choice in airfoils. Seemed like it was wanting to stall all the time. Any recommendations?
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Old Oct 21, 2009, 11:55 AM
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slope'n somewhere in the Andes
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"Best" I don't know, but something thin and cambered comes to mind. I'd check out Don Ayers airfoils with at least 2% camber.

Dieter Mahlein, ShredAir
Old Oct 21, 2009, 01:03 PM
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When I talked to Dave, he said he had not done a final CG check, plus it flew like it was quite tail heavy. I think it would have flown fine with the balance further forward, as there was plenty of wind at the time.
Old Oct 21, 2009, 01:16 PM
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Maybe a 10% rg-14 would work depending on your regular slope you fly at, I assume you have a decent place to fly.

You may consider touching base with joe cormier he has experience with big fast flying pss planes, same with dcairns

Good luck with the project, I flew a 2m p38 at point fermin with a 60oz wing loading it was crazy fast, take lots of pictures

B
Old Oct 21, 2009, 02:02 PM
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The S6060 or the S6061 are perfect for this type of PSS plane. The plane HAS to be balanced properly and it WILL fly fast and must be flown fast. These are relatively low camber and relatively thin airfoils. The 6061 will be faster than the 6060 but not by much.

I have seen many folks fly these airfoils on PSS planes with very great success as long as they realize the airfoils are relatively fast.

I would however, strongly suggest the airfoil be transitioned from one to the other from root to tip to minimize tip stalling. I would put the 6061 at the root, 6060 at the tip with about a 1/2 degree washout.
Old Oct 21, 2009, 02:10 PM
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The slope we are talking about is Point of the Mountain, Utah. This is where Soar Utah is hosted every other year.
Old Oct 21, 2009, 02:41 PM
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You might try the slope section here on RcG, the guys there may have more insight and/or experience since it is a strictly slope model.
Old Oct 21, 2009, 07:40 PM
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It's not going to build itself
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I built two 52" span P-38s about 12 years ago, EPP slopers. I think the foil was either 6060 or 6062. My wing is slightly thicker than some other EPP slope kits I've seen. Although not a floater, mine generally hangs in lighter lift than the others, and still rips in high winds. My tip cord was wider than scale and transitioned slightly symetrical and still needed washout. Mine is also ready for a rehab.
Tom
Old Oct 21, 2009, 09:25 PM
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Thanks for all the replies, but her is the problem as I see it. By the way the P-38 is a 1/5th scale rather the quarter scale as I stated.

You are correct the plane appeared to be tail heavy, but I also wonder if the 60-60 airfoild is a good choice.. Maybe it is, I just don't have enough experience with PSS to know. I was thinking it needed a little more lift.

Also because of the size of the airfoil, what you use on a small slope ship, may not work well on a model that is much larger. I've heard it said that Model airplane airfoils don't necessarily work well on full scale aircraft...and what works well on a small 60 in slope ship may not be very good for a PSS ship with a 16 in wing chord. I guess it all has to do with reynolds numbers.

Anyway, if someone has knowledge of an airfoil for a PSS ship of significant size and knows that it works OK, then I will relay that info to Dave Nash to use on his P-38 for next Soar Utah. Thanks for your help everyone.
Old Oct 21, 2009, 09:43 PM
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I'd go with the airfoil used on this PSS Bearcat.

https://www.rcgroups.com/forums/show....php?t=1002157
Old Oct 23, 2009, 02:34 AM
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It's not going to build itself
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I know someone already suggested Joe Cormier and Dave Cairns, for info. I think Brian Courtice took this photo of Joe and his 109 at the PSS fest


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