Skyaak-ing with Patrizio Bronzi

Dear Michael,
Thank you very much for your appreciation about my work. I am honored you posted my photos on that blog too.
DNA is the result of the work of more than two years, tons of problems was to be solved.
Carter helped me so much than I can call him a friend.
DNA flown on april 25. It is not an easy plane to control; it is "nervous and sensitive" (after all it is an aerobatic plane), so I’ll need a new computerized RC transmitting set for next tests.
I get a glance at your www.skyaak.blogspot.com and at the impressive futuristic prototypes (they seem coming form a Star Wars movie), but they are somewhat different from Hummingbird (HB) configuration. There is something I cannot understand: the diameter of the duct at the leading edge in HB (could I call it "inlet area"?) is larger than that of the trailing edge (outlet area), in Skyaak it is the contrary.
Air speed inside HB duct, when it move in the air, became greater then the outside air speed. This increase the trust of the props (pic1). Furthermore when HB fly with a positive incidence the the airfoil in the upper half of the duct has a greater incidence than the lower airfoil, that increase the lift of the plane. I think these two situation induce an opposite moment (torque?) in the two configurations (pic2). Your Skyaak model seems to have some holes in the annular surfaces, that maybe allow the air to go into the duct to compensate the pressure (?), but I don't think it can generate a positive vortex.
This is fantasy, I don’t know what happens in the real world. I have linked an aeronautic engineer who offered me to test DNA in the wind-tunnel of the university where he works, I hope to do it on summer.
I have some doubt about the efficiency of the HB configuration. For example I have tested the leading edge flux of the duct by means of tufts so I observed a separation bubble that increase the drag. Another doubt concerns the lift generated by the airfoil. In fact the aerodynamic theory says that the lift is generated by the different speeds of the flow: greater on the upper surface in respect to the lower surface. But what happens when the air is accelerated by the props inside the duct? The speed on the lower surface becomes greater than that on the upper surface.. HB should not fly!
I think something is wrong (and maybe it is me, but after all it is only toys matter.)
Michael, I’d like to know the aerodynamic specifications (CG position, wing load, efficience, Rn, airfoil etc..) of your Skyaak if it is possible, so I could study this configuration.
I hope you understood my english...
Ciao

Patrizio, do you have a DNA web-page, or a blog? A blog is FREE and very simple to set up and operate for anybody. Just go to www.blogger.com for easy instructions to get started, if you're interested. And/or you may want to join my blog as a team member. It is also FREE and can be UBER FUN. And easy. Let me know, OK?
Congratulations again on the HB RC model! It is very impressive. I know what it's like to work for a long time on a project. Many hurdles to get over.

Hi Michael, I don’t know what exactly a BLOG is, but if you think it is interesting please join me as team member, i’ll get a glance every now and then.
Patrizio, I will check out what is involved to have you join up as a skyaak team member, and let you know.

The fact is that I don’t like to spend many time in front of a PC monitor!

I have a Samsung SyncMaster 740N flat screen monitor. Very easy on the eyes. Low glare. Have you tried something like that?

The Skyaak configuration exhibits super-stability in flight. Skyaak has a natural tendency to rotate swiftly on its axis in flight because the three inner struts act as agitators and also propellers. It is this spinning motion in concert with the ring-wing configuration that creates the theoretical vortex drive. Spinning on its axis helps to stabilize an already stable design.

Of course, rotation induces gyroscopic forces that make the system stable. On the contrary it should induces a precession* moment, did you observe that? It‘d be eliminate making the rear ring wing turning on the contrary respect the forering-wing (don’t smile, I’d like to read your Italian!), I'm not laughing, sir. but wigs shold turn freely respect the main hub...In any case, the possibility of free-turning is necessary on a RC model (or on a full scale plane).
* 'precession' : "the slow movement of the axis of a spinning body around another axis"

We have discussed a tubular bearing that would permit the ring-wing to spin freely on the shaft. Maybe powered by an electro-magnetic turbine, that would spin at very high RPMs. I imagine both the front and rear wing could spin, depending on desired trajectory, etc. Perhaps the rear ring-wing could be employed with a push-prop at take-off, while the front pull-prop could be used intermittently to keep the nose up. Mix and match thrusters.
When the Skyaak ring-wing spins rapidly on its axis in flight, it appears to self-generate an energetic path, or vortex, that it rides along on. The trajectory is determined by speed. At very fast scale-speed ( I can spin an 18" model in a 34' orbit in about 1 second. Scaled up to an 18' long model translates to approximately 5000 MPH. )

We must take the Reynolds number into consideration, not geometrical proportions.

Excerpt from Wikapedia entry on the 'Reynolds number':
"Laminar flow occurs at low Reynolds numbers, where viscous forces are dominant, and is characterized by smooth, constant fluid motion, while turbulent flow, on the other hand, occurs at high Reynolds numbers and is dominated by inertial forces, producing random eddies, vortices and other flow fluctuations. The transition between laminar and turbulent flow is often indicated by a critical Reynolds number (Recrit), which depends on the exact flow configuration and must be determined experimentally. Within a certain range around this point there is a region of gradual transition where the flow is neither fully laminar nor fully turbulent, and predictions of fluid behaviour can be difficult."

Patrizio, it would appear that the way to arrive at the Reynolds number for Skyaak would require wind-tunnel testing, or do you have the technology to get the correct reading experimentally with a working prototype? I anticipate that the Reynolds number will be low, as the trajectory tends to be smooth and flowing.
The Skyaak configuration behaves itself very well when tether-flown. It cuts a very crisp trajectory that is highly maneuverable on the tether, as I believe I explained earlier. The CG is critical with the tether flight. A fraction of an inch off the CG renders it into a dumb stick, whereas the precise CG snaps it to attention. Free-spinning props at the nose and rear spin furiously in tether flight, and seem to enhance the stability even further!

Is the tether-flown acrobatic-kite like?

Yes. Except it must travel forward, and can be greatly accelerated with crisp, flowing trajectory. It seems to gain weight and vitality when it is flown on a pivoting tether. I souped up a retractable dog-leash by winding the internal spring up tighter. With this and a fishing leader at the anchorage, I get incredible results. Amazing speed and agility with an 18" model!

The position of the CG is not the same of the tether anchorage.

The tether anchorage is a bit ahead on the shaft of the CG.

I am curious to see it flying

I will try out the tether on a 'Mykro-Skyaak', that is only 14" in length. See it on the blog. If I get good results, I will send you one. If not, I can certainly hand-build a crude 18" model. It won't be laser-cut, but will certainly perform well.
I would be fascinated to get Skyaak Model 3 and the Mykro-Skyaak into a wind-tunnel for analysis. What, if any, are costs involved in this? Can we just do it for fun? To advance the design?

I’ll ask my friend what are the costs for a wind tunnel test, that possibility depend on the Director of the University

Cool. Thanks for that.

Maybe the rest of the configuration outside of the annular wing is what creates much of the lift, and the HB annular ducted prop provides thrust more than lift?

I think something is wrong (and maybe it is me, but after all it is only toys matter.)

I have built 300+ rough working prototypes over 5 years to figure out the exact correct proportions of ring-wing pitch and scale vs the overall length vs the ballast weight(s). I was excited to discover that the aerodynamic performance of Model 3 was enhanced big time with the addition of a second ballast exactly behind the CG, where the cockpit would be. The Model 3 likes weight on board. Must have it! The 2 ballast weights further enhance the stability of the trajectory when Skyaak is successfully hand-launched. It is very exciting and promising!

Maybe it is wing load matter.

I would be happy to send you a sample unit if you wish so you can build it and fly it yourself.

Of course, Michael let me know the address where I can send cash (I do not have credit card, I hate it...)

I will, Patrizio. Thanks for your interest. I will look forward to hearing your response. I will send you a demo video as well. You will get your Skyaak in a flat package that is designed for shipping. From this flat kit, you can assemble the Model 3. Glue-free. You will receive everything in the package that you need to construct a Model 3 that you can throw around with your pals, to witness the aerodynamic performance of the design yourself.

Very stimulating conversation. Your English is very clear. I understood perfectly. Patrizio, I want to tell you how much I appreciate the positive energy you have put into your response. Thanks very much for this! I remember one time Philip said to me that this is a lonely path, and also something about the power of co-operative spirits with a common vision. I believe he is right.

And I believe it too

P.S. I am sending a photo attachment of glow-in-the-dark Skyaak. How cool is that? It is a very weird sensation to throw and catch the
glow-in-the-dark Skyaak in pitch dark. But very cool and fun! It glows like crazy. I bet it will be huge once it catches on.

It seems like an Abiss creature...

Do you have any ideas how we can market Skyaak units to help create an R&D fund to advance the technology to the next level?

I am not an economist, but I think the best way is to show it at model airshows (I’ll go to Bologna next week, the most important show in italy, maybe next year...) and toy trade fair;
advertising is the very soul of trade

Patrizio, do you mind if I stick this dialogue and the drawings you sent on my blog? I will not do this without your permission. I think it is very interesting.
Please advise:)

Of course Michael It make me happy, ciao.