Slotted Flaps, a New Way - Klingberg Wing MkII Development
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- čas přidán 14. 04. 2024
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Note: Please post in English so the maximum number of people (including me) can benefit from your thoughts. - Věda a technologie
On an aircraft design I worked on we gave the ailerons a small increase in thickness. This, combined with hinge placement, kept the top surface of the aileron protruding into the boundary layer as it sips off the wing surface.
Yep, that would be standard design procedure. You can see me test that option in my earlier videos. It proved ineffective, probably because of the low Re. Near stall speed my wing operates at an Re range that is largely unexplored. See this vid for my CFD analysis of the issue: czcams.com/video/2mh8szvuD40/video.html
Thank you for sharing. Interesting concept and I'm looking forward to seeing the results.
Be sure to sign up at my Patreon site to get the results
Beautiful idea. All the best engineering is, of course, beautiful. Elegant solution.
Thank you very much!
Good luck Rol.
Thanks!
Thanks for the informative video. I hope this works out.
I had one question though; in of your videos from not too long ago, you hypothesized that the Reynolds numbers out at the tip are too low and that's what's causing all these problems.
So why not make a custom airfoil that performs well at those low Re? It seems to me that if the designers of the swift and the carbon dragon could do that in the 70s and 80s, with your level of knowledge, skill and experience and the software tools available today, that should be possible.
Thanks again for sharing your work
Yes, that would be quite easy. However, there is a price to pay. Low Re airfoils are inherently low speed. When taken to higher speeds (low AoA) the drag goes way up. In one of my vids I describe the drag polar for the low Re airfoils and why they get draggy. Gliders such as the Swift were not designed to go fast. I think they had a Vne of about 70 mph. I want a Vne around 100 mph, so this requires a different airfoil. This is all a very sticky problem because we have never really strived for an aircraft that has high performance over such a wide speed range - a vexing problem that requires airfoils that can change shape for different speed ranges (doable but very heavy) or a unique solution the will appear to be "like magic" if I ever find it.
@@KlingbergWingMkII Oh! I hadn't realized that. I'll go watch that video now. Thanks
Best of luck on you impending test flight.
To differentiate the effect of trip strip, you could also just close the air intake with a tape.
No, the cover on the upper surface could still act as a trip strip even if the bottom slot is closed. Good engineering dictates that the configuration for the upper cover be as close to identical as possible.
Looks like you are creating a slotted panel surface with the intent of keeping the flow from separating. The ME-163 has a similar slot detail near the leading edge of each wing to minimize flow separation. The Cessna 177 uses a short reverse (upside down) slot on the stabilator for better control response. You could also try VGs as a quick way to energize airflow over the flap. I would curve the internal channel for a smooth transition from bottom to top and eliminate the big flat piece. Interesting concept.
All good pts. There are many aircraft that have employed leading edge slats. I think the most interesting is the Tiger Moth (or was it the Gypsy?) which had LE slats that deployed automatically when it hit a predetermined AoA. If you check out my earlier videos you will see I've tried dozens of different VG options. Problem is, at 20 mph and a very low Re (under 500K) it is very difficult to energize the flow. VGs bring high energy flow from the freestream into the boundary layer but if there isn't much energy in the freestream, then they are useless. What I'm doing here is a simple first rough cut (my common approach to problem solving). Optimizing the solution comes later if the method proves to be effective.
I have a prediction, the flow will be interrupted by the deflector and act as a spoiler in the flap up position. Flap down it will act as a choke point and cause undesirable characteristics. better design may be to design a slotted flap that has a smooth airfoil leading edge and eliminate the excess hardware. Notice on the illustrations you've used from the laminar air flow style wing that very much attention was paid to SMOOTH airflow.
Interesting thoughts. Given the format we are working in, I'm not sure I'm correctly visualizing what you describe. That said, the best I can do is to note that I'm not doing this test to use on my flaps. I use the word "flap" as a generic term for a control surface. The elevons for my wing are flaps that must travel up and down, so I'm not sure what you are describing would work. The test I'm going to do is set up for down only to represent what happens on my wing. On my wing I'm having problems with the flow over the elevons only when they are deflected down. Does this make sense?
Rather than the reverse duct sticking up, why not reprofile so the duct follows the same profile as the wing and make the leading edge of the flap dive inside the duct?
Of course as that would be lower drag. However, this is an initial experiment and before I spend a lot of time do a bunch of fancy building, let's see if it even works.
I had one more question, that I hope you won't mind answering;
Won't the slotted elevons add drag? how do you plan to handle the additional drag?
Yes, the slots will add drag but probably a small amount compared to a low Re airfoil. The low Re airfoils have their high drag at AoAs of 1 degree or less. At those low AoAs the slots will be parallel to the flow so the added drag should be minimal because the pressure differential between the lower and upper surfaces is close to zero. There will be added drag only when the flap is deflected downward when turning. Most high speed runs involving minimal turning, so a limited negative impact. However, I still think the best answer will be the flat plate elevons attached to the TE of the wing. That currently looks like the lowest drag option. This upcoming test is an interesting side quest while I wait for good flying weather to test the flat plate elevons. Plus, it could be a good option for the flaps on my wing to make them more effective for pitch trim and landings.
@@KlingbergWingMkII Thank you
Hi Rol, Tehachapi, Labor Day Weekend?
Will they let me test my wing there?
@@KlingbergWingMkII I'll check. in the past we demoed the Carbon Dragon on auto tow after the sailplanes were down. We'll call it demo flights not test flights due to fatal at airport with powered homebuilt. There are hang glider sites near by. Airport runway is about 5000'.