Airfoils: Quabeck vs. Selig

[green66]

Hi all,

Just curious - What's the story with the popularity of the Quabeck (HQ, HQW) airfoils on so many large scale euro gliders, but not on US gliders which seem to favor the Selig (SD, SG) profiles?

Given the higher wing loading of the scale ships, and the greater popularity of sloping big gliders in Europe, are the Quabeck sections considered better (in terms of L/D, penetration, etc) at higher Reynolds numbers?

Chart below is HQ2/9 (black) vs. SD7037 at Re of about 205,000 (actual wind tunnel data). We (in the US) hear so much about the Selig profiles, but the HQ2/9 looks pretty good to me! Unfortunately, the website http://www.nasg.com/afdb/index-e.phtml didn't have polars for the more popular 3% camber HQ sections (anyone know where to get this data?).

I'd like to get some insight on this, since I'll be doing a 5-meter own-design.

Any comments appreciated!

[Gary Retterbush]

Here is the URL for Quabeck: www.hq-modellflug.de

Gary

[scalesoar]

Gary:
Personally I think the Europeans favor Harold Quabeck designs because he is European and they are familiar with him and his work, plus they do seem to work very well in the 2-3 percent thicknesses. and they camber/reflex well.
americans favor Selig because he in turn is their home grown guru of airfoil design.
I don't see a great difference in performance, but I am also an anti airfoil kind of guy who believes it is the overall package that makes a plane have favorable flight characteristics. (rather than an airfoill choice alone).

Best,
John
scalesoaring (http://www.scalesoaring.net)

[Gary Retterbush]

First off, the Europeans use a lot of SD stuff. But, I basically agree with your thoughts on the subject. The current mode also plays a roll.

I am not an advocate of any "name brand" airfoil. I fly what works for me in a given circustance. Heck, I even wear "no name" shorts! :rolleyes:

Joking aside, I think there is way too much talk about flying and not enough doing it. Not to say that a little scientific info is not good but as I recall the engineers are still trying to figure out how the bumble bee can fly.

DP has also proven time and again that it is mostly the pilot and not the plane that counts.

But, if it works for you, then that is all that counts. It's a hobby; enjoy!:)

[scalesoar]

Yes there are exceptions, and the one that comes to mind in the scale arena is Gerhard Bruckmann who uses the S-6060-61 on his incredible flying Swifts and Foxes. I know, I have his big Swift. Gerhard designs planes that are very easy to fly, but part of that is due to his generous use of Decalge. I usually flatten the stab and take out nose weight.
JD
scalesoaring (http://www.scalesoaring.net)

[green66]

. . . .but I am also an anti airfoil kind of guy who believes it is the overall package that makes a plane have favorable flight characteristics. Agreed, there's way more to it than the airfoil - how all parts of the plane interact as a whole, piloting skill, one's familiarity with the ship, etc. However, the choice of airfoil is still a basic consideration, and since my project is an own-design, I have freedom to use any section. My concern isn't in tweaking performance as much as avoiding use of an obviously inappropriate airfoil. As for the post, it seemed there's such a stark contrast in airfoil preferences between US and euro designers, I figured maybe the reason was more than just cultural.

I think there is way too much talk about flying and not enough doing it. Not to say that a little scientific info is not good. . . . Yes, certain hobby endeavors, especially own-design models, can easily turn into research projects (at which point the Fun Factor starts to diminish), which I'm consciously trying to avoid with this project. It's tempting to say to oneself "If I just learn about such-and-such technical issue, I might be able to squeeze out another 0.5% of performance." At some point you've got to say "It's good enough, time to launch."

Many competition pilots probably delve into highly-detailed technical nuances to give themselves an edge, but I don't have the time/will to fly competitively. I'm into r/c as a solo diversion - entertainment, if you will (although not necessarily for relaxation!) :)

[Terry Lyttle]

Wow. I have been looking at graphs for 40 years, and yet in practical terms, the graphs only dictate how difficult the wing will be to build, as far as I can see. I stick to Eppler 193 for my models because of its practical performance for me from F3B to sport sloper, and through reverse engineering one can see that its l/d profile works as advertised in the graph. My buddy built a model using a Wortmann (I think) airfoil, but he is into self-flagellation when it comes to building wings; model flies fine, up to its requirements.

Exactly right about science killing the fun, but one of the more interesting things I have done was building f/f wings to MAC, just out of curiosity...