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

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

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.

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

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.

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!

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

Oops.... Sorry double post

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.

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

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

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

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

Will track down BJ Craft, sounds a neat idea.

Regards

Dereck

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

also consider cbmodellisme.com PHOENIX

Always stay with NACA 00; 4 series. The 6 series is optimised for constant pressure ( boundary layer ) from laminar to transition to turbulent flow. For example, a 747 vertical fin would be a 00x 6 series.

Almost all the oxai's / krill / comp ARF F3A's don't deviate much from the modified 00x - 4 series. Something like a 0007_3_34 (3 being the radius of the leading edge, 34% is where chord is thickest).

The only heads up is scale the shape section as you move towards the wing-tip; don't change it. If you do the foil becomes very inefficient and unpredictable. Krill are on the mark with the cut-back; less inertia to overcome in the snap. Andrew Jesky has taken this to his design.

Hope this helps
Cheers
D
Aerospace Eng.