[Frank Colver]

This is an interesting new wing development. The fact the they tested it on a model glider and are now going to another model glider almost hang glider size would indicate that its low speed performance is good.

Check it out: http://www.techbriefs.com/component/con ... qotw/23443

Also notice that the article mentions the possibility of a roll-up wing version going to mars. That would be interesting for the "5 foot packed" thread on this forum. However, I have no idea how that would be done.

Frank C.

[Bob Kuczewski]

I don't know ... it looks a lot like a Colver Sky Sail.

Al_Bowers.png (329.68 KiB) Viewed 5703 times

[Rick Masters]

Don Mitchell also insisted that vertical surfaces were completely unnecessary on flying wings.

[Dayhead]

We HGer's prefer the flying wing design because it provides a means to fly with the minimum parts count. Parts= weight.

Of course I'm referring to the big parts here. The FW has only what we need: two wings and a 'handle'-the control bar.

It seems to me that the FW found it's home in HG. But it also has found a home in the military, where it's stealthiness is an advantage.

Other uses include 'drones' of various purposes, and I include the Mars glider here.

My own personal feeling is that the lack of vertical surfaces is a mixed bag. The speed and ease of rigging the small tail fin on my Sensor indicates that maybe the finless swept-aft planform might get some competition from HG designs having little or no sweep, and a simple fin instead of sweep.

Swept wings present us with torsional rigidity issues. It's easy to understand why we have stuck with them, as they simply evolved from the Delta design we started with.

The problem, as I see it, is the marriage of pitch stability and washout. When I fly a modern high-performance HG, I'm impressed with how much of our parts count and weight budget is devoted to this area. Two washout struts per side, and a spar that is robust enough to handle the loads imposed by them. And the not-so-funny thing is, on many flights we never even use them.

I suppose I should have posted this on the "Different way" forum, but here I am.

We might be able to reduce parts count and therefore weight by divorcing washout from pitch. I'm impressed with how effective the small tail fin is, and I don't need a whole lot of creative visualization to see that a larger one could be rigged and de-rigged almost as easily as the small one. And it just might be lighter than the current beefy leading edge with struts that we now use.

We all love the graceful, simple beauty of the aft-swept and finless Horten design. But I wonder if we couldn't do better with some re-thinking of our goals.

Hoping all here enjoyed their Thanksgiving holiday. I am truly thankful.

[Rick Masters]

it also has found a home in the military, where it's stealthiness is an advantage.

Don't forget that the FW has a much higher load-carrying capacity as a function of wing span than any conventional (or any other) aircraft.


Mock up of MOP inside a bomb bay of a B-2 simulator, 2007.

The U.S. Air Force has not officially recognized specific military requirement for an ultra-large bomb, but it does have a concept for a collection of massively sized penetrator and blast weapons, the so-called "Big BLU" collection, which includes the MOAB (Massive Ordnance Air Burst) bomb. Development of the MOP was performed at the Air Force Research Laboratory, Munitions Directorate, Eglin Air Force Base, Florida with design and testing work performed by Boeing. It is intended that the bomb will be deployed on the B-2 bomber, and will be guided by the use of GPS.Northrop Grumman announced a $2.5-million stealth-bomber refit contract on 19 July 2007. Each of the U.S. Air Force's B-2s is to be able to carry two 14-ton MOPs. -- Wikipedia

[KaiMartin]

The problem, as I see it, is the marriage of pitch stability and washout.

Ack.
The traditional way to overcome this limitation is a regular tail plane on a long boom. The vertical component of the tail plane also does away with the need for sweep. At the end of this route you reinvent the sail plane with its promises (incredible lift/drag) and limitations (no way to foot launch, needs an air field, towing infrastructure,...). So the traditional approach probably will not save hang gliding.

When I fly a modern high-performance HG, I'm impressed with how much of our parts count and weight budget is devoted to this area. Two washout struts per side, and a spar that is robust enough to handle the loads imposed by them. And the not-so-funny thing is, on many flights we never even use them.

Much of the required effort boils down to less than optimum geometry when it comes to forces and torque. To pull the trailing edge down, the flex wing pulls not down but almost horizontally. In addition, the flex uses the longest lever possible to pull. The leading edge tubes have to be strong enough to not yield prematurely and maintain a nice flat sail. The very fact that the leading edge tubes are placed at the leading edge contributes to the problem. Because of this position, the sail tries to bend the tubes rather than compress it. And of course the sail cloth itself has to be strong enough to resist the tension.

Unfortunately, an aerodynamically efficient flex wing requires a tightly pulled flat sail. In combination, this makes the weight of the wing grow to about the maximum level which is compatible with foot launching. It also makes (very) short packaging a hard task. Every additional joint tends to weaken the air frame and/or adds to the weight.

The quest for drastically lighter wings would look like a lost case if it wasn't for the glaring counter example PG. The above argument fails to apply to them. Their wings are floppy as a feather pillow even when fully inflated by ram air. This is possible because their lines pull almost vertically rather than horizontally. Consequently, the cloth of their sail can be very light weight -- ridiculously light weight when compared to flex wing laminates. In addition, every single line can be quite light weight too. Imagine a PG with lines made from HG side wires.

It is probably not possible to successfully apply the PG design principle to anything other than a PG, though.

---<)kaimartin(>---

[Frank Colver]

I keep thinking about the modern inflatable hang glider every time I look at my packraft. A boat that can carry me and a weeks worth of backpacking gear through whitewater rapids, grind over rocks, and smash into obstacles, all without damage and it only weighs 6-3/4 pounds. There has got to be a way to put this technology to use in the air.

Frank

[Dayhead]

What kind of material that is easily worked with could be used to make a model?

I'm wondering if cheap plastic sheeting can be heat-sealed with a tool such as a regulated soldering iron. once the workbench is properly set up, it shouldn't be too difficult to make some small, or large, flying models using inflatable tech.

Time to Google RC Blimp-making.

[Dayhead]

Please forgive the rambling. Too much stuff going on....


Washout and sweep versus a reflexed straight wing.

I guess around 15 to 20 years ago, swept aft flying wings became popular for RC, mostly for the slope, and now with LiPo batteries and brushless motors they are used for a variety of flying styles.

Here over the last few years the "plank", or straight-wing-with-a-fin design has become quite popular. They typically use elevons, but occasionally I see one with separate elevator and aileron systems. A now popular one called "Zulu" features "drooperons", which are droopable leading edges that move with elevon movement. To roll right, the right elevon moves up and the leading edge bends down, and the opposite happens on the left. For pitch, raising the elevons brings the drooperons down. Some folks are using extra servos so that the LE droop can be controlled separately from the elevons, using transmitters that can be programmed in some interesting ways.

I always hated using reflex for pitch control. It seems to me that as you are asking for more lift, you shouldn't be hampering the wing's ability to produce lift by adding reflex to the airfoil. So for a flying wing, I think weight-shift for pitch CONTROL might be more efficient. Pitch STABILITY of a sufficient amount can come from reflex.

For a foot-launched 103 glider, the vertical tail could be built with a wheel or skid mounted on the bottom. The tail could be hinged so that on launch the pilot can control pitch attitude of the wing, while the tail rests on it's wheel or skid.

My idea here is for a plank style flying wing HG, with a modest span but gobs of chord. Yes, aspect ratio equals a flatter glide, but more wing area will reduce stall speed and at low speeds, such as a PG's, a very good sink rate might be found. Somewhere on another forum I mentioned that the PG phenomenon inspired me to re-think the whole concept of "performance", and that explains what I'm considering here.

What I'd like to build is a hangie that is compromised towards the PG performance end of the spectrum. I watch my PG friends having a great time, especially in the late day glass-off, and I want to join them. But the issues the PG has tempers my desire to go that route.

While I am all for the inflatable way, at this time I'm focusing on using rigid materials. I'm much more familiar with them. When I can I will order the plans for Steve Woods' "Skypup" ultralight. It uses foam and wood, mostly Douglas Fir, to create an inexpensive and very light airframe. It also uses a pitch neutral airfoil, which it seems to me can contribute to a lighter wing structure.

There is a wealth of ideas to consider. Like many, I seem to be a victim of "paralysis by analysis", and so nothing gets built. But I'm working on my Self, a work in progress, and I'll stay subscribed to optimism.

[Bob Kuczewski]

"paralysis by analysis"

The world belongs to those who act ... carefully!!