kleinatze

....is to be recommend for Q 500?

Now I use an eppler 220. What do think about the mh 18 b?
As far as I know the predator has an symmetric - airfoil. To my mind, this is a bad solution, isn´t it?

What could be recommand?



Thanks a lot!!

Andreas

Here are the german Q 500 - Pilots (....there are just 3... unfortunately):

R.Bridge

The Q500 that won the Nationals 3 years in a row and set fast time 4 years in a row........has a fully symetrical airfoil.. it seems to work pretty good..

Finding the right airfoil is sometimes a trial and error experience, but it sounds like your on the right track with the MH stuff...


Randy Bridge
Team JR

Pylon-RCU

The new airfoil I am trying is symetracal from the wing tip and ten inches in, then it graduly go to 1/2 degree of camber at the root. I am hopping this works for me, I hope this adds more info for you...Marty

bl10

The VORTEX, arguably the best quickie on the planet, uses the NACA 66 airfoil. It is fully symmetrical with no washout. To date everything I have tried including a modified MH18b, MH18b and MH27 just aren’t as good for me. I was flying a VORTX last year and got several high 104’s (I’m just not as good as Randy and Travis). After losing it I built a couple of MH18b’s and the best I could go was mid 108’s. I put together another VORTEX and ran 104’s again. Currently picked up a N-QUE and clicked off a couple of high 107’s. You decide.


Barry

kleinatze

Hi!

have a look on: http://www.mh-aerotools.de/airfoils/index.htm


go fast turn left
Andreas

Daniel Z

I´m very curious about NACA 66, does it reach the usefull reynolds numbers with an standard OS40FX? That´s what we all are using here to race; I´m acually using MH18b airfoil with nice results.
I´m afraid that maybe without a nelson or a jett that airfoil will not perform as well, but if not, it could be interesting to build and test

Daniel

Pylon-RCU

Take a look at the mh 24,25,26,27

Daniel Z

OK, mh27 can be used but for Re of 500.000-1.000.000, are they usefull at 140-180 km/hr?

Pylon-RCU

Let me know what you think

Daniel Z

Have to know how to calc the Re we are working on.
Can someone help on this?

stand-RCU

Re calculation is somewhat complex. The RE for 428 is around 1,350,000 (180 mph) and the RE for 424 is around 1,000,000 (140 mph)this the RE for 120 mph would be around 900,000.

There are programs around for calculating the RE.The above are from R/C Model Airplane Design by Andy Lennon

Stan D.

Pylon-RCU

I dropped the mh 27 foil into compufoil and changed the camber, thickness and cord. I gave it to my buddy's brother who is an Aeronautical engineer. he said because the air is not scaled down with the foil it is hard to get good re numbers. He told me the foil I chose was really good for the speed we are traveling. Every one has there own idea of the perfect foil and this is mine. I hope this adds fuel to your quest. Marty

stand-RCU

About the NACA 66 airfoil. There is no such thing. There is a 6 (six) series of airfoils. Example: Naca 65-018 or NACA 66-012. The first digit indicates the series and the second indicates the area in tenths of the cord behind the leading edge that the minimum pressure occurs. I would guess that the Vortex, if it's using a NACA 66-xxx airfoil, is using something like NACA 66-012 (actually 012.3) The last two digits indicate the percent of thickness of the cord of the thickest part of the wing. In our case with a cord of 9.6875 we need to have 1.1875 thickness or ~ 12.25%.

Not all 6 series airfoils are symmetrical. The NACA 66-218 has camber. That's what the digit after dash is telling us; i.e., lift coefficient in tenths. So saying that the Vortex uses a 66 airfoil is very vague and tells nothing about the airfoil except the max. thickness of the wing is around 60% of the cord from the leading edge.

Altering an airfoil even slightly will have impact on the lift and drag characteristics. I recently cut cores for a new wing design. The first two cores suffered from wire lag; not enough wire tension and cutting too fast.
This caused a slight cupping of the leading edge that got worse as you moved from tip to root. At the root it was about 1/64" and ľ" long. The rest of the wing was ok. I modified the airfoil in CompuFoil to incorporate the cupping and then fed the results into JavaFoil. The cupping caused the drag at to increase sooner at lower angles of attack; i.e., slower in the turns. I double checked the CL vs alpha in Xfoil with the same results. So those first two wings are not as good theoretically than the next five I cut.

The point is that I can mess up an airfoil (or possibly make it better) by incorrectly sanding the surface or miss-shaping the leading edge. With a composite wing once the wing is cast in a good mold the wing is reproduced exactly and with a perfectly smooth surface. The problem is arriving at the "good" wing in the first place.

Oh, and then we go and tape quarters on the low wing! I don't even know how to model the excessive drag that causes.

Regards,
Stan D.

PS: If you're going to tweak an airfoil in Compufoil you need to compare the results of the new one to the original. If you don't you have no idea what the effect was. You can do this with JavaFoil or Xfoil (difficult to learn). Just use RE values between 800,000 and RE 1,200,000.

crashinmike

Hello, does anyone know where is can get a plot of the NACA 66-12 airfoil. I would gladly pay someone for it. Also if I could get it showing 3/32" sheeting on top and 1/16" shheting on the bottom.

Crashin Mike

PylonWorld

Send me an email if no one has sent you a plot yet. What format do you want it in? DXF, TIFF, BMP, Visio, etc

Also, I need to know the chord size.

I can't remember at the moment if I can use different sizes for the top and bottom sheeting , but a full outline, and one each with the 1/16" and 3/32" will get you there.

SSAN

You're SHARP, Stand... and getting Sharper!!!

Sam

Daniel Z

Don,
I´m interested in the airfoil too in DXF can be optimum
thanx

[email protected]

stand-RCU

NACA 66-012
(Stations and ordinates given
in per cent of airfoil chord)
----x-----y----dy/dx
0.0000 0.0000 0.0000
0.5000 0.9064 0.8331
0.7500 1.0872 0.6387
1.2500 1.3519 0.4537
2.5000 1.8068 0.3142
5.0000 2.4939 0.2428
7.5000 3.0382 0.1968
10.0000 3.4939 0.1695
15.0000 4.2335 0.1292
20.0000 4.7994 0.0991
25.0000 5.2366 0.0763
30.0000 5.5657 0.0560
35.0000 5.7986 0.0376
40.0000 5.9424 0.0197
45.0000 5.9981 0.0022
50.0000 5.9641 -0.0163
55.0000 5.8336 -0.0366
60.0000 5.5859 -0.0659
65.0000 5.1478 -0.1097
70.0000 4.5119 -0.1398
75.0000 3.7681 -0.1571
80.0000 2.9426 -0.1706
85.0000 2.0801 -0.1723
90.0000 1.2350 -0.1643
95.0000 0.4734 -0.1351
100.0000 0.0000 -0.0055
L.E. radius = 0.870 percent chord

----------- or cor file ---------------
1.000000 0.000000
0.994350 0.000413
0.977520 0.001694
0.950000 0.004308
0.926890 0.007301
0.900000 0.011423
0.850000 0.019564
0.800000 0.028046
0.750000 0.036348
0.700000 0.043990
0.649990 0.050545
0.600000 0.055499
0.550000 0.058233
0.500000 0.059627
0.450000 0.060000
0.400000 0.059467
0.350000 0.058020
0.300000 0.055652
0.250000 0.052332
0.200000 0.047931
0.150000 0.042229
0.100000 0.034741
0.075000 0.030093
0.050000 0.024605
0.025000 0.017644
0.012500 0.013016
0.007500 0.010476
0.005000 0.008822
0.001270 0.004721
0.000000 0.000000
0.001270 -0.004721
0.005000 -0.008822
0.007500 -0.010476
0.012500 -0.013016
0.025000 -0.017644
0.050000 -0.024605
0.075000 -0.030093
0.100000 -0.034741
0.150000 -0.042229
0.200000 -0.047931
0.250000 -0.052332
0.300000 -0.055652
0.350000 -0.058020
0.400000 -0.059467
0.450000 -0.060000
0.500000 -0.059627
0.550000 -0.058233
0.600000 -0.055499
0.649990 -0.050545
0.700000 -0.043990
0.750000 -0.036348
0.800000 -0.028046
0.850000 -0.019564
0.900000 -0.011423
0.926890 -0.007343
0.950000 -0.004308
0.977520 -0.001694
0.994350 -0.000413
1.000000 0.000000

Enjoy
Stan D.

Bill Vargas

My Feedback: (5)

Man thats a lot of typing!!!

(umm, you forgot one, hehe, just kidding )

BV

Daniel Z

In fact, is this the vortex airfoil?

stand-RCU

BV
Cut and paste ---- ctrl-c and ctrl-v no typing involved.

And, no that's NOT necessarily the Vortex airfoil. It is the NACA 66-012. I have no idea of what the Vortex airfoil is. If you crash one at the Winterfest and throw it in the trash can I will.

I would assume that what makes the Vortex so good is because it deviates some what. Because the NACA 66-012 doesn't stack up very well against some others in JavFoil or X-foil.

Stan Douglas

bl10

The Vortex airfoil is a pure N-66012, probably N-66012.03 to get thickness correct. There is no camber or washout. This is the same airfoil N-66010, (different thickness) used on the Vendetta Gino DelPonte set the SR Q40 record with at Whittier this year. As far as the computer analysis programs goes it’s like Fred’s brother Otto, who did the cnc wing mold software, and is one of the better airfoil engineers around, he also did all the software for APC props, says, “The only way you really know if its good is to fly it” referring to the various airfoil analysis programs. As an example of how far off things can get Fred looked at the polars for the MH-27 (same as the MH-24 used on some Q40 and FAI wings only thicker to meet the rules), and it looked better then the N-66012 of MH18b so he cut a mold from which we have built 5 planes. Carl Silva crashed the first on the first flight, Fred crashed the second on the first flight and the third on the 3rd flight. I crashed the 4th on about the tenth flight and the fifth one at about 30 flights. This airfoil looks very good in computer analysis but was virtually unflyable at first. We finally figured it out on the fifth plane. I managed a 107.70 with the last one before a glitch put it in. After all that I managed to come within three seconds of my best times with a Vortex.



Barry

Jerry Knols

My Feedback: (1)

Hello,
I have loved reading this thread, it at least shows everyone is thinking. Although i am retired now, I was a miniature airframe analyst with a RPV manufacturer for quite some time. I can tell you for a fact that all the number crunching in the world will not tell you with more than 85% accuracy what an airfoil will do on a small model such as a Q-500 . There is one very good airfoil that no one has mention that foe years has been used in RPV's that flew in the 150-200 mph range with wings in a 5 or 6 to 1 aspect ratio. That is the NACA 65-012 It is not spectacular at anything HOWEVER it is a fairly efficient airfoil over a wide range of speeds and angles of attack. Maybe take a peak at it. By the way, it works best with a 16% of wing area stab size and balanced in the 29% range. Fusalage distance between the CG and the elevator hinge line should be close to 45% wingspan in a 5 to 1 aspect ratio wing planform model


Jerry

stand-RCU

Jerry,
That's interesting. I used to manufacture a double tappered wing used for combat. At first I was just making the wing from a plan in one of the mags called the Combat Grimlin. It flew pretty well. I modified the airfoil to symetrical and it flew better, called this the Bird of Prey.

But I wanted my own design so I studied the "Theory of Wings Sections" by Abbott and Doenhoff and thought the NACA 65-010 looked good and I tried it. The first prototype flight was outstanding. It was about 50% faster than the old one and on my first landing I overshoot by about 150 feet because it was so clean.

I wound up selling over 2000 of them, the Raptor. I still have the jigs and made a couple last year to fly combat here. They still perform great and fly circles around the conventional tail planes and the original Grimlin. The wing was totally symmetrical and I just needed to reflex the elevons slightly to achieve level flight. CG was at 13%.

I also did some experimenting with strakes to increase AoA that worked out rather well, but that's another story.

Stan D.

banktoturn

kleinatze,

Back to your original question, a symmetrical airfoil is not a bad solution for a pylon plane, actually, it is close to the ideal one. The ideal solution, by definition, would be an airfoil with the optimum camber. The camber can be viewed as the coefficient of lift ( CL ) at which drag is minimized. This next part can be confusing, but here goes: an airfoil with higher camber has a higher minimum drag, but probably has lower drag at a particular CL, than an airfoil with lower camber. In other words, if you have a value of CL at which you need to operate, you can choose a camber which will give minumum drag. Since a pylon plane flies so fast, the CL needed for level flight is very low. The CL needed for turns is moderate, but not huge. The 'optimum' camber is thus a compromise between the optimum for level flight and the optimum for turns. Generally, the ideal value is pretty low, or close to a symmetrical airfoil. Probably better to be too low than too high, since the extra drag created by extra camber penalizes you the whole time you are flying. I have advocated variable camber for pylon planes ( a pretty decent implementation of variable camber would be flaperons ) in a couple threads here, so I won't get on my soap box here. If you 'set' your camber to give you about the right CL for level flight ( ie., generating enough lift to carry the weight of the plane ), you won't be far off, and you will have an almost symmetrical airfoil. The '6' series NACA airfoils actually denote the camber in the form of an intended CL, although the CL observed in our pylon planes may not match up exactly. You would need to get some Xfoil results or something to be sure. However, it is very significant that the clever guys/gals at NACA spoke of camber in terms of CL. We should do the same.

banktoturn