P-38 Wing Incidence
10-11-2010, 12:40 PM
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P-38 Wing Incidence
I am building a 1/4 scale P-38 and am finalizing the design.
I have started with 3-views which show about 4 1/3 degrees of positive incidence at the wing root. They also show 2 1/2 degrees of washout at the wing tip.
Are these observations accurate?
Are there any concerns on the flying characteristics using these measurements?
This plane will have very scale lines based on the 3 views.
Please excuse any misuse of terminology.
I have started with 3-views which show about 4 1/3 degrees of positive incidence at the wing root. They also show 2 1/2 degrees of washout at the wing tip.
Are these observations accurate?
Are there any concerns on the flying characteristics using these measurements?
This plane will have very scale lines based on the 3 views.
Please excuse any misuse of terminology.
10-11-2010, 02:01 PM
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RE: P-38 Wing Incidence
Based on those drawings your figures seem accurate enough. And with the extreme taper of the P38 wings you certainly do want to have a generous amount of washout. On top of your measured washout I'm also seeing that the tip airfoil has what appears to be more camber than the root. That is also something that will aid in resisting tip stalling and it should be kept. But overall given the lower reynolds numbers and how it affects our models I'd suggest upping the washout angle to 3 or even 3.5 degrees.
10-11-2010, 02:25 PM
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RE: P-38 Wing Incidence
*Root chord 30" (max thickness 4.75") NACA 23016
*Tip Chord 9" (max thickness 1.2") NACA 4412
The airfoil profile is a smooth transition over the 156 inch wingspan from the NACA 23016 at the root to a NACA 4412 at the tip
*Tip Chord 9" (max thickness 1.2") NACA 4412
The airfoil profile is a smooth transition over the 156 inch wingspan from the NACA 23016 at the root to a NACA 4412 at the tip
10-11-2010, 04:34 PM
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RE: P-38 Wing Incidence
Oh, that IS big 
With a 9 inch chord and that airfoil you should be fine with the original 2.5 inch washout. Or maybe bump it up to an even 3 degrees for a little extra insurance. Not being in the cockpit it's hard to sense the oncome of stalls and with models of this sort a tip stall generally does not come with a nice ending. An extra half degree will make the wing a trifle less efficient over all but the tradeoff of some added resistance to a tip stall will be worth it.
With a 9 inch chord and that airfoil you should be fine with the original 2.5 inch washout. Or maybe bump it up to an even 3 degrees for a little extra insurance. Not being in the cockpit it's hard to sense the oncome of stalls and with models of this sort a tip stall generally does not come with a nice ending. An extra half degree will make the wing a trifle less efficient over all but the tradeoff of some added resistance to a tip stall will be worth it.
