Dakota stepped airfoil help

[alligood]

A recent issue of MA magazine showed a pic. of the glide killing
all balsa airfoil used on an old FF Dakota Bipe. I want to try the airfoil, but I've misplaced the mag. Can anyone help me by posting an image of the airfoil?

[BMatthews]

I just happen to have the plans. The wing is 1/4 x 1 trailing edge stock used as the leading edge and 3 inches of 1/16 balsa with a slight curve to it for the trailing edge. The curve doens't quite match up to be tanget with the leading edge stock but it's not quite level either. It rises up from where it attaches to the LE stock along it's upper edge for another 1/32 or so and then curves down to the trailing edge. There's half ribs with a simple arc to support the rear sheeting.

I'm not sure if it's this miracle wing section that slows it down or just the fact it's a Dakota. Take yer pick.... :D

So what are you building that requires such a "headwind" anyway?

[alligood]

Thanks, BMathews for the detailed description. I fly in fairly small spaces in an area that's often windy and where the terrain is uneven and scrubby.

I like to fly rudder-only, so I am on the hunt for a small plane that will come down fast and not blow off the field when the power quits. I like the Fred Reese LS because it has the right qualities.

A similar sheet wing plane appeals to me. I can quickly build a handful of wings and not get too bothered if I ding one up by clipping a prickly pear cactus or a scrub cedar on landing.

[BMatthews]

If you're flying rudder only in stiff winds then my hat is off to you...

I just recently did my own rudder only model and conquered the monster. And it only took me 38 years of modelling to learn how to do it... :D

I think you may be going in the wrong direction though. Far from not blowing off the field the extra drag and resulting slower speeds will hamper you when the idea is to fly upwind. As I'm sure you know if you've done much of this the best way to fly upwind is a series of short shallow S turns to keep the nose down and the flying speed up. The Dakota wing won't let you do this as effectively. Not to mention that the extra drag will hamper you in the spiral dives when you are trying to build up speed for doing maneuvers.

I would suggest that you stick with a PROPER Clark Y airfoil. The real thing as printed out from the proper coordinates actually has a pretty good set of flying charactaristics compared to even modern glider airfoils. This will let you penetrate upwind by encouraging speed rather than fighting it all the way as the Dakota airfoil would do. And your energy retention during stunts would be better as well. Far from being a prblem when the engine quits the better airfoil and higher speed would mean that you would be able to gain ground against the wind rather than be blown backwards. Proper trimming to accomadate the needs of the winds would then finish the combination package. A ground adjustable trim tab could be used to retrim for a more bouyant climb and glide on the calmer days.

That last bit is what I'm finding with my model. It's great on low wind days but it's a handful in stiffer winds. A little ground tab would let me control the climb to adjust to conditions and, hopefully, only affect the stunting slightly. Or I could just change the stabilizer shim I suppose...... but that's SO lo tech.... :D

Cheers...

[alligood]

Thanks again BMatthews. I really like the force balance arrangement of the LS. I had one years ago and I found it pretty easy to manage in the breeze. I guess I was thinking I could duplicate its behavior with the Dakota airfoil. Maybe I should define breeze - I'm talking 5 -10 MPH. Anything more and I crave ailerons. Anyhow, I appreciate your point about the Dakota's lack of penetration.

I've always enjoyed odd airplanes - I'm a big Roy Clough fan. ;)
So...maybe I'll build a Dakota just for nostalgia kicks. I noticed that BMJR has it as a kit.

[T. Lyttle]

Hah! Another Roy Clough fan, me too.
When I was into Ace stuff, I built a "trainer" using an old Ace wing kit, and it taught me a lot about "energy management". Got it stuck in a number of trees, went for long walks, the usual beginner stuff. Eventually, I could make it loop, Immelmann, the usual limits to pure single channel. Great but ugly model.

Finding legs on "breezy" days is certainly a positive, and I can't help but give credit to that Ace wing; the airfoil was just the best for s/c; wonder why? Still look at the old Reese designs, the Ace High, Cessna 150, Whizard, etc, and now I may have time to build a few. Single Channel: the ultimate radio cantrol challenge!

[alligood]

T. Lyttle - I used to "build" a pylon wing plane in about half an hour with an Ace wing, a spruce boom and some 1/16 tail feathers. I just stuck the radio stuff on the side of the pylon and used ply or plastic to keep the glow slime out of it. It had proportions like some of the old FF pylon jobs. It sounds like your experience parallels mine. I lost 'em in cornfields, wheat fields and treetops. I loved seeing my plane way up high, so I'd try to get as much altitude as I could before the Baby Bee cut out.

I liked to try to thermal them then circle down and S-turn to land. I agree with you that the Ace is a wonderful SC wing. I scratch built my first SC and R-E designs with them.

I tell you what else - I miss Model Builder magazine. You could count on it to have some kind of silly fun design just about every month. Roy Clough inspired me to make my own designs, too...
They might have been ugly up close but they sure were beautiful
in the air.


Rudder-only is terrific. :)

[T. Lyttle]

Yeah, is it Model Builder, or Bill Northrup you miss most? Northrup really understood the hobby, same way Bill Winter did. Model Builder (it seems) became kinda vidictive about advertisers, and tried to stick to its content/advertising ratio, which is far better than, say, RCModeler; I haven't bought a copy of that catalogue.. sorry, magazine in over a decade. I always check it out, always put it back on the rack, then buy the Brit AMI instead. I figure it is the advertising that keeps it alive, certainly not modeller participation; most of the designs seem to be based on a redesigned Ugly Stik (lessee, this month will it be more engines, or rudders, or a fake cockpit, or...)

Then I look at an old MAN and find Northrop's Big John or somesuch, and immediately go to my back issues of Model Builder for inspiration. Ah, nostalgia ain't what it used to be...

[BMatthews]

The SAM guys are flying a time target event down in Tacoma for the Dakota models. It's a great windy day event because they just don't get high enough for long enough to drift far. And they are tough for when they do come down.

I'm planning on making one this winter and using a super reliable instant starting Wen Mac engine on mine. And I even got a back up engine at a swap meet. All I have to do is melt the goo holding it together so it'll turn over.... :rolleyes:

Alligood, why don't you do the 150% Littlest Stick that LynnS is promoting in the thread here? That would be a quick build but still offer some super performance. Trimmed right you wouldn't even have to worry about those 10 mph breezes.

[alligood]

BMatthews - I'm gonna build that LS. I signed on for that on
another forum.... in fact, today is Veterans' Day holiday in the US,
so I have a holiday and I'm off to the LHS for balsa as soon as
they open this morning.

To all the veterans who read this - thank you for your service and sacrifice.