If your A/R is under 3 then you won't need to worry about any of this, as you won't get a defined stall as such anyway.
Evan, WB#12.

If I figured it right my aspect ratio is 6:1...
Root cord is 84" Tip cord is 36" span is 3'

One of our better airo engineers was also a modeler and made some exeriments with symetrical wings. He would increase the thickness of the airfoil as the span increased. Typically an 8% thick at root and 12% at the tip. He said his gut feel was that it improved the landing characteristics a bit by delaying the point at which the tip would stall and allowed lower landing speeds but admitted this was purely his perception and he had no measureable data to back it up.

Here are the coordinates:

http://www.ae.uiuc.edu/m-selig/pub/LSATs/vol3/S8037.LFT

You can find a LOT of airfoils researched by Michael Selig at:

http://www.ae.uiuc.edu/m-selig/

Aspect ratio is span squared divided by area, your wing with a seven foot chord and three foot tip averages as a five foot chord and three foot span. A/R is then less than one, stall will not be a problem, getting it to stall might be.
Evan, WB#12.

Delta planform itself is known to be "non-stalling". Most deltas won't stall.

The thick tip foil (progressively thicker foil from root to tip) -- was marketed in the Funtana model. (Funtana90 example)
the next version of this model ? right back to progressively thinner .
as a practical matter - in these small aerobats - the airfoil only needs be thick enough to be stiff and fre from load failure.
I had two of the Funtanas. they flew fine - but the so called improved stall feature was simply non existant. it was just marketing hype to the uninformed.

Primmnz,
Make sure I have this right..
Span squared = 9 ft
Wing area = 15 ft
So my aspect ratio is .6.
So I am worrying about nothing!

Da Rock,
While this has the proportions of a delta it is a backwards one. Any Idea how that may effect the flight characteristics?

dick,
With this design I am ggoing to be going from a thickroot foil to a thin tip foil, with the top of the wing flat to provide dihedral.

Please check out odball design 101 in the scratch build forum.
All comments welcome!

Have you seen this?
http://www.warbirdbuilder.com/Need%20for%20Speed.htm

Iron Eagle, you have a `reverse delta' for want of a better term, tip stall will not be a worry. with normal deltas the wing has plenty of sweepback for stability (works like dihedral) but I see yours has forward sweep. Probably not a huge problem, but I would make those tailplane/elevators into tailerons for roll control, rather than those tiny ailerons.
Evan, WB#12.

I have intended to make them work as Tailerons but had no idea what it was called, these will also be linked to the ailerons, and the elavons in the vectored thrust setup.

Iron Eagel,

Check out the UIUC Airfoil Database at : http://www.ae.uiuc.edu/m-selig/ads/c...atabase.html#S

THe late Hal De Bolt used a 'progressive' airfoil in many of his designs. He had several fantastic designs. I would encourage you to look into some of his design notes.

turbo

Iron Eagle.

Thanks for the Vulcan photos.

Turbo,
I would have loved to have had the chance to talk with Hal De Bolt, I recall for many years he held records for speed.
I got to look at some of his designs closer....
I had no idea when I asked this question that it would get so much attention.
I know the concept had been applied to full scale, but wondered if it was worth the bother at low R#s.

It is worth the bother doing. I know it helped me with the CL stunters. And their performance is more easily tested than any other kind of model we fly.

But there's also a subtle thing about trying stuff.

If what you try seems to work for you, it has. If you try something and think it helped, it did. It doesn't matter if it really did or not. If we fly with more confidence, we almost always fly better. So indirectly, it did work.

(Unfortunately, if something doesn't seem to work for you, then it hasn't, even if you're wrong and it's really helping. So be slow to decide that your tests disprove anything.)

To make things even easier...deltas fly just fine with a standard symmetric airfoil, no reflex required, the old `draw it around your favourite shoe' type of thing. Really.
Evan, WB#12.

A long time ago a well known modeller had an article in a mag. Had this special CM9 airfoil he used on his planes and they flew well. Everybody was scrambling to find this airfoil and no one could find it. About a yr. later he let the cat out of the bag and told them it was his enitials and his shoe size.

Hello, I,ve been following your thread and I have some info that might help. the wing stalls because it is subjected to a certain angle and turbulance is formed on top of the wing making it loose lift. To make the root stall before the tip the most influencing factor is the sharpness of the leading edge not the thickness of the wing, the sharper the L.E. the earlier the stall.(EX: the funtanaS40's L.E. gets sharper towards the root although the wing manteins the same thickness) thick wings are employed to allow for wider leading edges. making the le wider will allow the wing stall at a steeper angle not to mention that it also gives more lift. to avoid tip stalls the are various methods including making the leading edge sharper towards the root so the root will stall at lower angle than the tip eliminating tip stalls. I'll put up some pics when I get the chance about an article explaining the different techniques to "TAME THE STALL" (great article!!!). I hope this solves lots of your questions and helps you!

This is what I plan to use on this wing.

Fine, but so long as your CG is in front of the aerodynamic centre, and it will be for a pitch stable model, then you don't need a reflexed airfoil, any good symmetric (zero camber) foil will do. This stuff has been known from the early pylon racing days, when 0.19 powered deltas ruled, way back in the early `60's. The foil you have chosen will result in an inferior flying model. Remember, it's a delta, not a `plank' type flying wing.
Evan, WB#12.

Last night as I worked on the design after getting back from the field I have decided to scrap the use of a reflexed foil on the wingtip. This is not going to be a flying wing per say so using the reflex at the tip is not going to be of much use. On top of this this sill be so lightly loaded that the landing should be very tame. I do have one additional question on Jacks Northrop's original flying wing when it got into ground effect it would stay there for a long time, does anyone know what they did to resolve this?
I think I might see the same thing and was thinking about adding a spoiler/airbrake on top of the fuse to get it on the ground.

I fly a delta, 48" span with a .40 up front, landing will not be a problem as you can control the drag with pitch, since these things will fly with what appears to be a huge AOA the also have huge drag, it'll land ok. The problem is if you don't get enough nose up on landing, then they can whistle along the strip without losing much height, just go around again and don't be afraid of up elevator. It takes a couple of flights to get the hang of the things, but they are a lot of fun and performance on much less power than you might think they need.
Evan, WB#12.

Evan,
Thanks for the info, that explains a lot. Like I said when testing with the glider I noticed that once it got into ground effect it seemed that it wanted to go on forever. I am a bit concerned about high AOA approaches with this beast because of tail strike, where the tail is going to have a lot of moving components for the vectored thrust system. I guess I am going to have to work out the landing gear location to min. that possibility.
Regards
Paul

Maybe nice long legs on it like one of my favorite, the Vought Cuttlass. Not quite a delta but close.

Now there is an airplane I had forgotten about, not a delta, not a flying wing, but a little of both in one.