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        Help! Pattern type airfoils

#1 Dereck Nov 21, 2012 12:23 PM

Pattern type airfoils
 
Figure you pattern guys can help me out here.

Background - competed some, but years ago. It left me with a strong yearning to fly in 'pattern' fashion rather than just ambling a model around the sky while tossing in the odd loop or roll.

I also have this really strange quirk - I design my own models :eek:

Down to business - after years of using basically two airfoils on my OD (Own Design) models, I think I could do better.

So - what are the favoured airfoils for 'pattern' type models these days? I can handle CAD and Profili, but date back to drawing airfoils off percentage chords and above/below chord line dimensions, so should be able to draw a symmetrical airfoil up from most sources.

Thank you in advance,

Dereck

#2 Curare Nov 21, 2012 09:48 PM

Heh, if you ask someone like Dick Hanson he'll tell you "it doesn't matter". I tend to agree.

Wing area, planform and percentage thickness have more of an effect than airfoil shape in determining a good pattern plane.

The old school planes were all using the NACA 00 series airfoils or slight derivatives thereof.

These days I've noticed (well, last time I looked) that most designs were using a NACA64a010 or something similar.

Chord and taper have increased, (sweep is the new black) and percetage thickness has reduced, and as a result, aspect ratio is also reduced.

#3 Dereck Nov 23, 2012 09:52 AM

Cheers Curare - had a feeling that'd be a good answer.

One of my two airfoils is Bruce Tharpe's TLAR off his Four Star series, or at least a close relative. No-one's ever told me that a Four Star is boring to watch...

The other's NACA 00** - have it in CAD format, real easy to change the ** bit for thickness.

Amateur night still, but if % thickness has reduced, does that mean that flying speeds have gone up some? I got to a couple of pattern comps in England just before turnaround became the Big Thing and the speed some of those babies could hit on the display line was pretty staggering.

Low AR for a stiffer wing framework, but sharper taper on the wings to keep snap/spin departures within easy reach - sounds good.

Time for a new blank CAD file.

Thanks again

Dereck

#4 perttime Nov 23, 2012 12:15 PM

I'm pretty sure top speeds have gone way down since the old days. Fuselages are now huge, engines are powerful and set up to produce more thrust than speed. Top competitors have gone for electric power for consistent performance.

#5 Curare Nov 23, 2012 06:00 PM

Yeah, pert time is right, speeds are down, compared to the 'olden days', and power is up.

Having the ability to control your upline speed and your downline speed with an electric is also a nice thing. (I like it:)) I also like the repeatability of each flight, just add a fresh pack and go.

It might be worth checking out a pattern comp in your area some time. Pick the pattern nerds' brains!

#6 viva_peru Nov 23, 2012 10:28 PM

Hi Dereck,

I know that this is heresy to you, but if you are thinking about building something that will fly on 4 or 5 cells there are a few very reasonably priced ARFs out there. I doubt that you will be able to build anything that is significantly lighter or straighter.

I am pretty new to pattern, but after 3 years at it, I have come to the conclusion that I will be assembling my pattern planes rather than building them. As a compromise, I do build my sport/scale planes as an outlet to deal with my need to cut and glue things together.

By the way, the newer designs fly very well, so much so, that sometimes I struggle to fly my students trainers well which is rather embarrassing. Pattern planes just make flying that much easier.

Teo

#7 viva_peru Nov 23, 2012 10:33 PM

Oops.... Sorry double post

#8 perttime Nov 24, 2012 03:48 AM

Of course, there are still people enthusiastic about "Classic" Pattern designs and that style of flying. That just doesn't cut it in the higher levels of modern competition.

At lower levels of competition, anything that will do a roll and a loop is just fine. In my corner of the world, using the latest 2x2 meter designs in the beginner and intermediate classes would be frowned upon.

#9 Dereck Nov 25, 2012 11:00 AM

Teo - you're probably right. But I have this thing about finding an identical model in the pits... As I am way past competing now, for many reasons, it's not worth the bother to 'spend to pretend'.

It's how competition goes, any sport. When I was heavily into bike racing in the last century, I could strip my bike down and rebuild it for fun. Now, most cyclists in the serious end of the sport can't tell which end of a screwdriver's best to hold, but they know how to spend on New! Exciting! Stuff when told to.

Though the nearest I get to 'pattern' is reading their columns in MA and FM, it is immediately obvious it is a way more complex game, both in equipment and flying abilities, than not even that long ago.

Also read that a new 'status symbol' is a bright red $2000 Honda generator for pits charging those 5000mA 10S packs. Now we are getting into other realms...

If you ever want fun at a local level, back in my old day job in the last century, we had a huge association long weekend competition cum aeromodelling party. One event was 'three channel aerobatics'. Rudder/ele/throttle only, you picked your maneuvres out of a list and went at it. It was a pretty big organisation - the pattern judges were both internationally ranked FAI pattern status in Europe at the time.

Most folk flew old trainer trainers with some degree of overpowering. I cheated and built a large scale model of the 'Smog Hog' at 54" span for a 19 diesel. Hard to imagine it was once the top of the aerobatic heap, but I've seen few RET models that could handle a repeatable and on-order Avalanche Loop...

And now back to my drawing board (figuratively speaking, of course) - maybe my 'other airfoil' - NACA 00** - isn't all that bad after all?

Thank you all for your inputs.

D

#10 viva_peru Nov 25, 2012 02:39 PM

Dereck,

Good luck and make sure to post a few photos a long way. Fortunately, pattern planes are not that common so only occasionally does the other guy who also owns an Angel show up on the same day as I do.

In the lower classes, sportsman and intermediate, a .50 sized plane can be competetive if the winds are light. Anything more than 10 to 15 mph and the bigger planes have a definite advantage. I had one contest this summer where the average winds were running around 22 mph gusting to 33 mph. That was a challange. I really struggled that day.

Teo

#11 gaRCfield Nov 25, 2012 03:27 PM

Take a look at BJ Craft's airplanes (Nuance, Prolog, Monolog, Episode, etc) - the designer is an aero engineer who designs the wings by the numbers.

Some of the current 'tricks' are with combining two airfoils, with a stepped transition somewhere near 2/3 to 3/4 of the span. I think the purpose is to 'loosen up' a stable wing for better snap performance, etc.
http://rcone.kr/board/index.html?id=bjair1&page=2&no=87
http://www.krill-model.com/download/.../index_usa.htm

#12 Dereck Nov 26, 2012 09:53 AM

Those wings are, well, cool beyond cool!

Competition spirit? My Spousal Unit came out to a pylon race meet I won back in England, first time she'd ever seen me compete. We were fairly newlyweds back then. She told me later that she never realised I had much of a competitive spirit, but when she saw me head to the start of the final, she felt sorry for the other three guys.

Unfortunately, travel and long hours are now somewhat beyond me, but the drive to be in charge of my model and push my envelope a little hasn't left me. Hence my preference for the pattern type aircraft I came to like a long while back.

Though I must admit that my favourite comp was scale - where you try to come up with a true representation of an aircraft and make it perform good, when in fact it handles like a bad-tempered pig that will bite your backside as soon as look at you.

Perhaps if we ever win the lottery, I'll order me one of those top end electric F3A birds with all the support gear. Shortly before rushing down to the Tesla dealership to buy a new car - dream on D :rolleyes:

Will track down BJ Craft, sounds a neat idea.

Regards

Dereck

#13 JohnAV8R Jan 28, 2013 11:47 AM

Wingmaster can be used to design airfoils and wings.
 
Dereck you may have forgotten about the old Model Cad and Wingmaster programs, in which case you may be interested in the following.

Wingmaster, is a an old program for Designing Airfoils.
It will export to a CAD program.

Wingmaster can be used to design airfoils and wings. To Design a NACA airfoil, select the Airfoil Design menu, and choose NACA 6-Series, NACA 5-digit, or NACA 4-digit airfoil. You can then enter the NACA number, or the thickness and camber parameters. These values can be entered, or you can use the scroll bar to change the value. As you change values, the changes are reflected in the airfoil.

Be aware that Wingmaster performs no aerodynamic analysis. It is possible to design an airfoil with very bad flight characteristics. When you test a new airfoil, be careful!

The Independent option lets you set the parameters for the top and the bottom of the airfoil independently. If the "Independent" option is not checked, a change to the top or bottom of the airfoil will be reflected in both the top and bottom.

The Grid option displays a grid over the airfoil. The grid is spaced in tenths of the root chord.

You can also edit an airfoil, scaling the thickness and camber up or down. This can be done by selecting Edit Airfoil under the Edit menu. NACA airfoils and airfoils loaded from disk can be modified in this manner.

There are three airfoils on the main Wingmaster screen -- the Root, the Tip, and the Current airfoil. When you design a NACA airfoil or load an airfoil from disk, it normally becomes the current airfoil. This airfoil can be moved to the root or tip position by clicking on an arrow button. You can also edit or design an airfoil by double-clicking on one of the airfoil picture boxes.
John

#14 TimBle Jan 31, 2013 04:06 PM

also consider cbmodellisme.com PHOENIX

#15 Dylan_Anderson Feb 11, 2013 09:03 AM

I highly doubt this thread is still active; but just in case... Originally I had posted some info stating (quite ignorantly infact) that the NACA 4 Series were preferred over the 6 series. And that is just incorrect!
I also said that the 6 series was efficient at specific speeds but outside those speeds became inefficient. This is true, but your talking about a full size aircraft flying faster that Mach 0.7, or the Rn being over 10,000,000. RC Rn's are more around the 100,000 for F3A.

The 6 series is being used most commonly on the main wing and the rear stabs are 4 series as - when correctly designed - will produce the drag an F3A design wants. There are and always will be exceptions! I just didn't want misleading info posted.
Cheers


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