C-130 airfoil

[GPerk]

I am planning to build 'close to scale' model of a C-130. I have drawn some plans based on what I believe are true scale drawings. It appears the the airfoil on the C-130 is very close to NACA 2320 airfoil.
I am looking at a model with 50 inch wingspan. The chord (inboard of #2 engine) would be 7 inches. The thickness would be 1.4 inches.
My question is:
Should I use the 2320 airfoil or should I use something less scale - flat bottom or thinner?
I want it to be at least 'stand-off scale' but, most importantly, I want it to fly. I hope to power the plane with 4 speed-400 motors, or similar.
Any comments? Suggestions?

[Ollie]

A 20% thick airfoil on a seven inch chord will be very draggy indeed. The wing will absorb a lot of the available power just to push it through the air. A 10 or 12% thick airfoil will take a lot less power. A 7 or 8% thick airfoil would be even more efficient but then you would have to pay a lot of attention to the wing spar design. Stick with about 2 or 3% mean camber and you will get a high enough coefficient of lift. The best airfoil selection will depend somewhat on the wing loading and what speed range you want.

[BMatthews]

I find it hard to believe that the full scale 130 uses a 20% thick airfoil. Are you sure about that number? I'm also quite sure that a more modern aircraft like the 130 would not use an older NACA 4 digit airfoil. It may LOOK similar but I'll bet it's something else.

None of this changes the fact that what Ollie said is spot on. For the sake of your model I would choose something more model specific. The Selig 4233 springs to mind as does the Eppler 201 or 195. I used the 201 on an electric sailplane and can vouch for it's excellent performance with a load (2 meter span and 56 oz). The E195 is from the same family but with slightly less camber but a shape that may be easier to build. All three are around the 11 to 12% thick range so will provide good strength without resorting to large or exotic materials. My glider wing started as a highstart and winch launched 2 meter model and suffered no problems even with it's 1/8x1/4 top and bottom spruce spars and 1/16 webbing.

[vintage1]

A lot depends on what sort of speed you want to fly at. Personally a 50" span model of a lumbering giant of a transport plane ought to be flying at about 6mph, weigh just an oz or two, and have a couple of GWS IPS motors and two freewheelers...:D

4 speed 400's is gong to be a fighter plane at that span...

Personally, I'd go for 4 IPS' 'A' boxes, 7x6 props and a 3s1p LIPO, and shoot for not more than 25oz AUW, to get a flying speed in the mid teens of mph. At that sort of speed it probably makes no difference WHAT the wing section is, so make it as scale as you like.

All cargo planes are just powered draggy gliders really. That's how they ought to fly.

Of course its going to be a real hard job to make that weight at that size, and retain a scale look, but its definitely where I would be aiming.

[AndyKunz]

I have a 86" span C-130 powered by Unobtanium motors (discontinued Pittmans). It uses a flat bottom Clark Y-ish airfoil and flies WELL on 400 watts max total (20 cells with a 20A fuse). It's all built-up balsa, and my uncalibrated hand says 5-6 pounds AUW. It was built about 10 years ago by Ken Stinson and has had numerous flights at KRC and such.

Pictures are at www.montanadesign.com/planes/C-130 and here's one that defines my project for next winter:

http://www.montanadesign.com/transient/C-130_Down.jpg

Andy

[Sparky Paul]

According to "The Incomplete Guide to Airfoil Usage:"
http://www.aae.uiuc.edu/m-selig/ads/aircraft.html
C-130 uses a 64A318... 18% thick.
12% would be a better choice.

[BMatthews]

I hadn't seen the reference to the 50 inch span until I read Vintage1's post. Yeah I agree that it'll fly more like a jet fighter than a scale like cargo model with 4 400's and the battery pack(s) to run them. But I differ on the method to take towards lightening the power loading. I'd be more likely to use the GWS EPS100's with the 280 size motors for a 50 inch span model. AUW should come in at about 35 to 37 oz and at that weight a scale model of a Herc at that size should still have a decently slow enough flight speed to look nicely scale like. I'm guessing it'll have around 400 sq inches to hold it up?

[uscra112]

I've got a half-finished sorta-scale "Shadower" (Vintage knows what that is, right?) about the same size. I calculated that 4 280 can motors running DD will fly it just fine.

Doesn't that foamy "Cargo" use a 4x 280 setup?

[GPerk]

According to "The Incomplete Guide to Airfoil Usage:"
http://www.aae.uiuc.edu/m-selig/ads/aircraft.html
C-130 uses a 64A318... 18% thick.
12% would be a better choice.

Sparky Paul is right. But the thickness tapers to 12% at the wing tips.
That site also says the root chord is 16 feet. So the root thickness would be 2.88 feet!!! I guess Lockheed wanted a very strong wing for those hard landings on rough fields.

[uscra112]

Or a thick airfoil for high lift.

[gkamysz]

I have a kit for a C-130 at 71" powered by geared S400's. It uses an Eppler 205. I would also suggest a lighter power system for a 50" version. Cargo is 67" with direct S400's.

Greg

[jawadravian]

hi evry1...
can anyone here provide me with the coordinates of 64A318 airfoil?
im having trouble designing it on designfoil...and i really need it for my project.
I'll be grateful
thankx

[JetPlaneFlyer]

Here are the coordinated in a .dat file.

What do you plan to use it for?... While it may work well on a full scale C-130 performance of this airfoil even at giant scale model Reynolds Numbers is pretty horrible. A Clark Y would be infinitely better and easier to build.
Unless you are willing to sacrifice everything for scale fidelity?

Steve