P-51 Mustang 1:10 (44.4") Airfoil help?

[Veloc-E-raptor]

I'm looking for a good airfoil to use on a P-51 III (B/C), 1:10 scale (44.4" wingspan), with scale retracts+doors (thick root..), approx 6lbs (or less!! :) ). I am looking for scale-type flying/mild(ish!) aerobatics.
Would the original/full scale NACA 45-100 (root and tip) work?(I suspect the answer is 'not well....', and something semi-symetrical would be better)
All help would be appreciated

[Ollie]

The S8036 and S8037 were developed for the size and scale-type flying/mild(ish!) aerobatics.

See:
http://www.nasg.com/afdb/show-airfoil-e.phtml?id=1060
http://www.nasg.com/afdb/show-airfoil-e.phtml?id=1061

[Guille]

I'd recommend to avoid any laminar flow airfoil... the never-fail ones are the NACA 230xx and 44xx (xx represents the thickness). Another recommendation: try to get a plane as ligh as possible...
Regards!

[hul]

I used a Ritz 2-30-xx for my 1/8 FW190, 15% at the root, 13% at the last rib. Mark Rittinger uses something very similar (according to him) for his warbrids. The Ritz has a low cm, which let you use smaller horizontal stabilizers.

Hans

[Veloc-E-raptor]

Thanks for the info. I certainly agree on getting the airplane as light as possible, but I'm building from scratch and looking at the pesimistic side of things. All things being well it should be alot lighter than my 6lb estimate (but you know how the scale bits start to add up!!!).
Any more suggestions on suitable airfoils? (whilst I review the ones already suggested.. S8036 looks promising... :) )

[Ollie]

http://www.top-flite.com/airplanes/topa0140.html
http://www.top-flite.com/airplanes/topa0140.html
"An effective combination of Selig 8036 and 8037 airfoils offers a slow stall speed, excellent stall resistance and superior handling throughout the rpm range."
http://www.top-flite.com/airplanes/topa0135.html
"The airfoils used on the P-47D Thunderbolt were developed by Dr. Michael Selig of the Low Speed Airfoil Test Program at the University of Illinois at Urbana-Champaign. They provide stable, more forgiving R/C warbird flight."

[Veloc-E-raptor]

What would you say would be 'an effective combination', S8036 at root transitioning to S8037 at tip, 2deg washout?

[Ollie]

Use this:
http://aero.stanford.edu/WingCalc.html

[BMatthews]

At 44 1/2 inch wingspan the wing area is going to be quite small. Under 400 sq inches I suspect. At this size you'll find that you really do not want your weight to go higher than 3.5 lbs and even this is on the heavy side for this size of model. 3 lbs would ensure that it will be a decent flyer.

If your previous background is with larger models it is easy to see why you came up with the 6 (or less) lb weight. But I suspect you forgot the scale factor that says each model size range category has it's own best wingloading range. A 400 sq inch model at 3 lbs is pretty much as heavy as you want for a 40 to 50 inch span range model design. The 3 lb weight combined with a nice .25 will ensure you can do pretty much all the maneuvers that the original Mustang did and have them look nicely scale like. As the wing loading becomes heavier than that things get ugly very quickly.

I also concur with the idea of the S8036 and S8037 with the lower camber of the 8036 being a better option for doing those scale like aerobatics. But even a good airfoil can only make up for so much extra wing loading. You'll still need to aim at a 3lb AUW or suffer from the flying brick syndrome. A couple of ounces over won't be the end of the world but having flown a 3.7 lb ARF model that had a little over 400 sq inches a few times I'm not keen on repeating that sort of nasty experience.

[Veloc-E-raptor]

Ok, the S8036 is looking to be my best option, and I think I will keep the same profile from root to tip (unless anyone would advise against that), with a couple of degrees washout.
It appears to be approx 333 Sq inches, so with a wing loading of about 21 oz/sq ft, a revised max target weight of 3lb. I must admit that I should have done the maths before guessing at 6 lb!!!! Now looking out for helium filled materials!!!
Many thanks to everyone.

[Igwe Aneke]

How about good old NACA 2415 (or 24xx)? For a 60" warbird I looked at different airfoils (Rn 432k) and NACA 2415 in all cases had the highest Clmax...(1.35 vs. 1.1-1.2 for all the others.)

[Ollie]

"How about good old NACA 2415 (or 24xx)?"

It is fine.

I agree with BMatthew.

You must budget weight item by item for every piece of equipment and structure to better performance. You should use a digital scale to pick the balsa stock, etc. Low weight is equaly important to picking an airfoil.

[BMatthews]

.......It appears to be approx 333 Sq inches,......

OUCH! When I suggested that it would be less than 400 I was thinking it would only be JUST under. 333 sq inches is smack dab in .15 engine territory. You didn't mention what power you were considering but if it's a 25'ish size engine and you're still keen on retracts I would strongly suggest a size increase that'll provide something in the order of 400 to 430 sq inches. Or if you're keen on the 45'ish span then a change in philosophy about the amount of mechanical detials you incorporate and the structural design.

Micro or at least mini radio components, something like the Robart retracts originally intended for the House of Balsa series models and a keen eye on the gram scale to ensure you use wood that is no more than 6 lb/cu foot for most parts will help a lot. Even if you bump the size up to the bigger wing area I would suggest mini sized servos and battery pack to help keep the weight under control as well as that gram scale.

Anyway, best of luck with your project.

[mrittinger]

My 42" P51 is right around 250 sq, and it has flown well at 45 ounces, but not any heavier. I switched to a 2450 Tanic 3 cell, and now it comes in at 36, and man does it fly well at that weight!
I use something similar to the Ritz 3-30-13, but it just ended up that way from trial and error. My section has a rearward low point, and a forward high point, and I run 1/8" washout.Flys like it's on rails, great penetration, wonderful lift, and soft stall.

If you get anywhere near 4 1/2 pounds at 44", you are in for a lead sled. You ahve to learn to build light, yet strong. Thats why my designs are single piece models, they become one cohesve unit with great strength for thier weight.

The Multiplex BL4804G with a 4.4:1 box spins a 12.5 x 6.5 very nice at 22 amps. (stright up with my 37 ounce fw190a8)
You can go with a 5 turn and go 13.5" prop for scale on your bird, or add another cell and really get the power up with the amps. If you want a scale 4 blade, I'd suggest running the 6 turn geared 4.4 on 3s1p lipo, and build LIGHT.