Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by Monty, Mar 8, 2019.
The Rogallo wing has a very real airfoil. If you slice a cone at an angle.......
Take a cone, cut in half, tip to base. Lay imaginary half cones on table, edge to edge. Sliced parallel to the join are airfoil sections, varying in washout, root to tip. Pure conic projection, a half parabola.....
Although, I believe In real life it's a catenary curve, not the ideal parabola.
In a real world rogallo, you cut the trailing edge in a curve ( modified catenary) to eliminate unsupported, fluttering, drag area.
You can make the Rogallo wing from sheet aluminum, but it's generally a waste of effort to do so, since it's the foldable nature of a membrane/cloth wing that made such wings attractive, first for kites then space craft landing parachutes, the Flying jeeps..... Then hang gliders.
The irony and humor that the most advanced NASA reentry tech technology was being flown by amateur pilots did not escape us at the time.
I will point out the conic curves from the Rogallo wing were used as wing tip shapes on F-106 Mach 2 interceptors. Greatly improved low speed performance.
I'm not suggesting using a Rogallo on your design, just pointing out that although the projected platform of a delta is the same, it's an apples to plums comparison.
For thin sections, the airfoil shape does not have as much of an effect as on thicker sections, especially in a design like this. In general, however, the emphasis is well deserved.
Not as much of an issue with a delta as with others. The wing itself is it's own tapered root fillet.
You can just stick it on a slab side.
>squints harder< ... That's still just a conic intersecting another shape. It doesn't distort the conic, it just dictates how the base of the conic is trimmed. If you're actually talking about the fillet, then that, like a wingtip, is another matter, one usually handled either with non-structural composites or an English Wheel.
Keep squinting....Have you used an English wheel??
Slab side is not an attractive look...
Please see original post. How much difference does it make?? No one has given a number. I want a number, not a feeling.
Reference post #2. " Would it fly, yes. How well? [There is] only one way to tell."
If you want numbers you need to do the work or have someone else do the work for you. I appears you are looking for the second solution. So am I (and many others).
This would be great for a supersonic wing made of unobtainium.
I haven't read any papers showing that vortex lift has the magic lift enhancing abilities implied here. It might allow you to reach a fairly normal Cl with a low aspect ratio wing, I suppose.
I don't expect anyone to do the numbers for me. What I would like is constructive reference to appropriate documents or publications, or commentary from those that might have actual real world experience with this type of planform. Honestly the model aircraft people are more helpful than this place. Unfortunately the reynolds #s are not comparable.
This is one of those cases where xfoil would probably tell you everything you need to know. My guess is that you'll see a big separation bubble at the forward edge of the flat section starting at fairly low angle of attack. That nobody around here has tried it is probably not a good sign.
I do not have experience with xfoil but it is my impression that the xfoil equations do not support the LE "vortex lift" flow of delta wings at high angle of attack. Can anyone with xfoil comment on that?
I don't really place much stock in 2D vortex panel methods. Especially in a case where span-wise flow and 3D effects predominate. I was hoping for some publications to help validate CFD analysis, which I can do....
Unfortunately I think most of this work is in the dark world or internal documents..oh for the days of NACA.
Would any of these reports be of any help?
View attachment 19930090363-min.pdf
View attachment Low-speed static stability and rolling characteristics of low-aspect-ratio wings of triangular a.pdf
View attachment naca-rm-a6g24.pdf
The first report describes a configuration close to what you are suggesting:
That last report has some good info. Virtually no penalty in cruise. About .2 CL hit for the double wedge at low mach numbers. I would expect my wing to be between the two somewhere. That study was for a plank wing. I would expect since there is a great deal of spanwise flow with a delta it will present more like an actual airfoil to the flow, and should not be much worse than a 0.1 CL hit. At least this brackets the problem. Thanks!
Nope. I'd do a non-structural fillet in composites, like, well... most people. But my real point is this: Your flat-box delta has flat-wrap conic leading edges (in the form of a strake) and, one presumes, a flat-wrap conic trailing edge aft of the main box. So, in the end, not really any different than a conventional-airfoil wing fore and aft of the box, in terms of the wing-fuselage intersection. You're still going to have to merge the conic projections with the fuselage shape somehow.
Well, if this is really your question...
That's not a question someone is going to be able to give a numeric answer for without 1) A better definition of "performance" as you intend to mean it here, as in which parameters are you wanting to measure. Cruise drag? Low-speed lift and drag? Pitching moment? Yaw moments at low speed and some given yaw angle? 2) A heck of a lot of CFD, and pretty high-end CFD at that. Vortex lift isn't something you can just toss up on XFLR5 and get a reasonable answer, and the answer, like structural FEA, is going to depend a lot on how you mesh and set up the model and problem. 3) An actual model to run the CFD upon.
Separated flow is still devilishly hard to model accurately even with "prosumer" CFD software, although that situation is improving as the high-end codes the "big boys" use are filtering down to us layfolk. Boeing could give you a very clear numeric answer to your question (once the parameters are defined and the model provided) but I would imagine that few here on HBA have access to that level of code. Orion used to have some semi-empirical ways of estimating values and coefficients for vortex lift, but in the end he'd send out his model to a paid consultant with appropriate software to get actual numeric answers. His Raspberry design being the most prominent one described here on HBA.
After a bit of reading on vortex lift, and on Ed Heinemann and the A4 development, I think you're on the right track. As long as you stay in the neighborhood of the A4's thrust/mass ratio, a RIFPIB plank delta will work fine.
Actually, Bill Husa (Orion) published a paper on "Airfoil selection" that included that information. Copies are available on the web; here's one link.
Considering what passed for an "airfoil" on the F104 and the F117 (and the Hiperbipe, for that matter), I'll bet you won't suffer that much with this concept.
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