CARDFAN

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I will build a 1/4 scale Boeing "Peashooter" using Jim Pepino drawings.Actually it's a "tad" less than 1/4 scale; W.S. is 80". My question is in regard to the use of an airfoil for the wing. It doesn't have to be exact scale as I would rather have good flying characteristics than an exact representation. The full size used a Boeing 109 foil which is a flat bottom shape with a rather blunt leading edge leading to a thick root early in the section. I've read the full size had good stall properties. The wing has no dihedral out to the fixed landing gear then slight dihedral to the tip. Over time I have been advised that NACA 23012 section(semi symetrical) has good low number Reynolds performance(read that as low sped only) and balances good lift/drag characteristics with good inverted performance properties. Almost as good as symetrical. In any event, would like an opinion(s) with someone knowledgeable on the subject. I don't intend much aerobatics but I do want reasonable performance from it.

All Day Dan

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I am knowledgeable about the subject because I have designed, built and flown so many models using it. It’s the NACA2415 or 17 depending on how thick you need the wing. Dan.

CARDFAN

My Feedback: (64)

Great, could you share your thoughts?? Obviously your happy with it

smithcreek

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I built the Royal version and it uses a flat bottom wing similar to the full scale, but thicker I think. I assumed the Royal used a Clark-Y or something very similar. It works great for that plane, though I can't say I do much aerobatics other than loops and rolls with that plane. On a different subject, if I was building with the Pepino plans I would alter the fuselage shape. It's so far out of scale from the rear of the cockpit forward it looks terrible. Even the Royal plans are off quite a bit, but the finished model does not stand out as wrong like the Pepino. This picture shows the real shape pretty good. Good enough to improve the plans if you want.

All Day Dan

My Feedback: (5)

Card, during the good old days, when the model magazines were of some value, lots of construction articles and information about models in general, this was a popular subject. The airfoils that were recommended for model use were the Clark Y and NACA four digit ones. It was something gleaned from experience more than anything else. As the radios developed from single channel, where the Clark Y was heavily used, through reeds and then proportional, the more aerodynamic airfoils became popular, leading to the four digit use. They are still good for my type of flying. I am not interested in unlimited vertical performance, 3D, snap rolls or inverted low passes. Taking off and landing in one piece is all I’m looking for. I’ll attach two of my designs that appeared in the now defunct Flying Models magazine. They both used the NACA 2417. On sport models, where I don’t need the extra stability when landing, I use the 00XX airfoil. On the P26, I would recommend the NACA 2417 because of the plan form of the wing. Dan.

CARDFAN

My Feedback: (64)

Thanks Dan; Super!!!

BMatthews

For that size if you expect to build it a little heavy you may want to consider the Selig 8036 or 8037. These were originally designed for use on some Top Flite scale kits. The idea being that at model sizes these airfoils are tolerant of heavier than ideal wing loadings. They tend to be rather stall resistant which makes them easier to set up on landing approaches and avoid surprises during climb outs from takeoffs that might be a little early and a touch slower than idea.