help with Navion airfoil

[Vanning]

Hey all.
Im building a 67" Navion from some old Berkeley plans i got from Uncle Willies. The full scale subject im modeling (see pic) has a totally different airfoil than whats on my plans.
The plans show a plain semi-symmetrical 'foil, but the real plane has a flat bottomed airfoil at the root and an undercambered tip. I would love to have the trainer-like handling of the flat bottom with the undercamber (I get to fly about once every couple months :o ) Im concerned about what airfoil i should choose and additionally i dont know how to get the AoA correct.

[nmasters]

According to The Incomplete Guide to Airfoil Usage (http://www.ae.uiuc.edu/m-selig/ads/aircraft.html) the Navion's airfoil sections are:

NACA 4415 (http://www.ae.uiuc.edu/m-selig/ads/coord/naca4415.dat) R at the root
NACA 6410R at the tip

I have no idea what the "R" stands for. The 6410 is not in my catalog of antique airfoils and I wasn't able to find the coordinates on line. It's just a 10% NACA 64xx so if you have airfoil software you could just change the thickness of the 6409 (http://www.ae.uiuc.edu/m-selig/ads/coord/n6409.dat) . Or even just use that airfoil. At the model's Reynolds number the whole wing could stand to be a bit thinner than the full scale plane.

--Norm

[JetPlaneFlyer]

I think that you will also find that the Navion uses quite a bit of washout. You would usually set the washout at the difference between the zero lift angles of the two airfoils. If you want good low speed handling then washout is critical.

Steve

[MarkusN]

The NACAs will work (I could provide true coords of the 6410 if you want, although thickening the 6409 won't give too much of an error), but with your spec what you want from the wing I'd simply use a Clark Y througout. Robust, good lift, easy to build, forgiving. Add a bit of washout to improve handling / stall cahracteristics and you're all set.

As for the "R" in the profile designation: Wasn't that used in the NACA measurements to denominate "standard roughness"? It's more of a characteristic of the measurement data than of the actual airfoil.

[Vanning]

Thanks guys! Wow Norm thats some list you have there. I'll hafta bookmark that.
Let me get all this loaded into Wingmaster and see what i come up with.
Mike

[coosbaylumber]

I was the one who did the plan for Miller back a couple years ago. The Berkeley kit used one of the formulae airfoils which worked good for their intended purpose. The model A/C was designed to be flown single channel, or multi.

The airfoil used was off a set of Musciani plans for same A/C (but as a multi).

There was a discussion about this A/C model at RCSCALEBUILER a few months ago.

Wm.

[Vanning]

Yep thats me - i cross posted the question. Honestly i didnt think the answer would come so quickly. I plugged the airfoil into Wingmaster and printed out the ribs already! Much easier than i had anticipated.
Progress hasnt been quick, but she's looking good.

[coosbaylumber]

I cannot remember exactly, but found pencilled note on old Miller plan leading me to believe we used a NACA23015 airfoil set at 3 degrees incidence. C.G. was to be at 25% of chord.

Wm.