Old Koreelah Posted October 27, 2016 Share Posted October 27, 2016 Thanks for your efforts DJ, but perhaps there's been some miscommunication. Your post #35 implied the wing root cuff fixed the violent wing stall and wing drop. Your post #50 says the wing fence fixed it. Sounds like both posts are talking about the same feature. I'm interested in the aerodynamic effects of the triangular leading edge extension seen on the 4-seat Victa. (It's also seen on the P-51 Mustang and some larger Jodels.) 1 Link to comment Share on other sites More sharing options...
bexrbetter Posted October 27, 2016 Share Posted October 27, 2016 I'm interested in the aerodynamic effects of the triangular leading edge extension seen on the 4-seat Victa. (It's also seen on the P-51 Mustang and some larger Jodels.) Theres a number of articles on them if you Google leading edge stall strips and/or leading edge cuffs How Do Stall Strips Work? wing cuffs | Surjeet Yadav Link to comment Share on other sites More sharing options...
Old Koreelah Posted October 27, 2016 Share Posted October 27, 2016 Thanks for trying Bex, but no, I'm NOT talking about cuffs or stall strips (both of which I have fitted to my Jodel). As I have been trying to explain, I'm interested in the aerodynamic effects of the triangular extensions to the leading edges of several aircraft, including larger Jodels, the P-51 Mustang and the 4-seat Victa: Link to comment Share on other sites More sharing options...
bexrbetter Posted October 27, 2016 Share Posted October 27, 2016 the aerodynamic effects of the triangular extensions to the leading edges of several aircraft, lerx .. https://www.google.com/search?q=wing+leading+edge+lerx&newwindow=1&rlz=1C1AOHY_zh-cnIL708IL708&espv=2&biw=819&bih=542&source=lnms&sa=X&ved=0ahUKEwjk7d3R8_rPAhVKeD4KHUGmACEQ_AUIBSgA or lex https://www.google.com/search?q=wing+leading+edge+lerx&newwindow=1&rlz=1C1AOHY_zh-cnIL708IL708&espv=2&biw=819&bih=542&source=lnms&sa=X&ved=0ahUKEwjk7d3R8_rPAhVKeD4KHUGmACEQ_AUIBSgA#newwindow=1&q=wing+leading+edge+lex 2 Link to comment Share on other sites More sharing options...
djpacro Posted October 27, 2016 Share Posted October 27, 2016 Thanks for your efforts DJ, but perhaps there's been some miscommunication. definitely was, sorry Your post #50 says the wing fence fixed it. Sounds like both posts are talking about the same feature.I'm interested in the aerodynamic effects of the triangular leading edge extension seen on the 4-seat Victa. (It's also seen on the P-51 Mustang and some larger Jodels.) Yes, my old memory mixed two data sets. The Aircruiser WT test report I have is the same wing configuration as the prototype - both wind tunnel model and flight test of the prototype displayed the same sudden stall of one wing. Fixed by the wing fence on the prototype.That triangular LE extension I call the wing root cuff. The one on the Aircruiser is bigger than the one on the T-34C - somewhere there is data on a wing like the T-34C with and without cuff - perhaps I will find it before long. My recollection is that this data shows the benefits in stall behaviour of the wing root leading edge cuff as used on the Nash Petrel here http://aviadejavu.ru/Images6/JS/Janes75/1/296-1.jpg this was based on the Kittiwake which had a straight wing https://doc8643.com/static/img/aircrafts/3D/KITI.jpg Prototypes of both flew so must be data on them somewhere too ..... https://www.flightglobal.com/FlightPDFArchive/1981/1981%20-%203419.PDF ...... https://www.flightglobal.com/FlightPDFArchive/1967/1967%20-%201297.PDF The root LE cuff is fairly common http://www.zlinaircraft.eu/galerie/slider/slider-26.jpg wish I could find the data The following link for wing design, generic and specific to T-34C is relevant but doesn't fully address your interest so I will keep looking. https://www.google.com.au/url?sa=t&rct=j&q=&esrc=s&source=web&cd=7&cad=rja&uact=8&ved=0ahUKEwiK9JWs8_rPAhXGp5QKHY12AnYQFggwMAY&url=http%3A%2F%2Fwww.public.navy.mil%2Fnavsafecen%2FDocuments%2Faviation%2FSAS%2Faero%2FCH4-Stal.doc%3FMobile%3D1%26Source%3D%252Fnavsafecen%252F_layouts%252Fmobile%252Fview.aspx%253FList%253D8006e81c-b3d9-4e6f-a528-d2944db57cae%2526View%253D24fea1bc-5ae2-4542-a47b-901dc8d264d2%2526RootFolder%253D%25252Fnavsafecen%25252FDocuments%25252Faviation%25252FSAS%25252Faero%2526CurrentPage%253D1&usg=AFQjCNGir6y6kRJW7_CdV23m9Gkqq_69yg&sig2=5l_XF3_XD2SwoVGDRha41A All of the above was a generation before this stuff that you see on some modern wings Leading-edge extension - Wikipedia 1 Link to comment Share on other sites More sharing options...
Old Koreelah Posted October 27, 2016 Share Posted October 27, 2016 Thanks Bex and DJP. Lots of reading ahead of me. Why am I interested? With all the improvements I made to my Jodel D-9 the weight crept up and so did the stall speed. I made a few changes to flying surfaces which helped, but the stall is now a little quicker than I like, and the right wing tends to drop. Using ideas from Dafydd Llewellyn I've been experimenting with fences and stall strips, which is helping. Still a bit more testing to do there. Meanwhile, still open to other ideas. 1 Link to comment Share on other sites More sharing options...
JEM Posted October 27, 2016 Share Posted October 27, 2016 Wasn't MVR registered thus to recognise Mervyn Victor Richardson. Link to comment Share on other sites More sharing options...
geoffreywh Posted October 28, 2016 Share Posted October 28, 2016 go with invigorators or turbulators (which ever you like to call them) .. Great sucsess on my D11. got mine in QLD about 6 years ago. They will drop the stall a little and the aeroplane will be easwier to control at low speeds Link to comment Share on other sites More sharing options...
Oscar Posted October 28, 2016 Share Posted October 28, 2016 You are talking VGs. IF they are installed correctly - and that is subject to proper flight testing - theycan be bloody good. BUT: do not be deceived that they can just be chucked on and will work as expected. The Sunbird Seeker with properly-installed VGs, was reported by the FAA 'Light Aircraft Division' test p[ilot, to be 'perhaps the best stalling behavious aircraft I have ever tested - and the FAA should consult with (Dafydd Llewellyn, who did that work) to derive specifications for VG installs (paraphrased). The implicit message there was: even the FAA does not know how to best use VGs - go talk to someone who does. Now here's the evidence: When the FAA test pilot came out to run the Seeker through its paces, it showed a serious wing drop at extreme crossed-control stall. Contrary to the test flying results. Sunbird got back to Dafydd Llewellyn. It transpired that Sunbird had re-painted that aircraft, removing the VGs to do the re-paint for the job, and had re-installed one of them around 1/2" out of position. It happened to be a critical one. With all VGs in correct position, the Seeker can be flown at just above the stall speed, level, at nearly 20 degrees of yaw angle, quite happily. I have flown that test aircraft, and even to me as a novice power pilot, it was incredibly easy to control in attitudes that one would not hope to contemplate in most aircraft. It was designed to do Power Line Inspections with a forward-facing camera, at low speed and very low altitude: the job normally done by Helicopters. It succeeded in that - having only NOT the ability to hover. This is NOT a rant against VGs: they are marvelous aids to low-speed control PROVIDED that they are correctly installed, and they do not detract from cruise speed.. BUT: if incorrectly installed, they can produce a result that they hold control down to an airspeed below which separation is abrupt and violent. You need to take into account not only the wing spanwise airflow to ensure that the centre section stalls before the ailerons, but also that the downwash from the centre section does not affect the elevator authority. 1 Link to comment Share on other sites More sharing options...
geoffreywh Posted October 28, 2016 Share Posted October 28, 2016 OH yes VG's , I've been using / working with them since the early seventies. BUT if you are telling me that one VG thingy out of place on a thirty foot wing caused a serious problem then I need to be doing something else as this thread has just gone to the dogs. . 1 1 Link to comment Share on other sites More sharing options...
Oscar Posted October 28, 2016 Share Posted October 28, 2016 GW: if you have better knowledge than a CASA accredited Test Pilot and the Aero-engineer responsible for the certification of, amongst others, the Gazelle, Jabiru LSA55 through to 160, Sunbird Seeker, AND the FAA Light Aircraft Division Chief Test Pilot, I salute you. 1 1 Link to comment Share on other sites More sharing options...
Old Koreelah Posted October 28, 2016 Share Posted October 28, 2016 You are talking VGs. IF they are installed correctly - and that is subject to proper flight testing - they can be bloody good...if incorrectly installed, they can produce a result that they hold control down to an airspeed below which separation is abrupt and violent... That's the crux of the issue, Oscar. VGs might reduce stall speed, but they can't do miracles. If you're flying too slowly, you fall out of the sky. How violently you fall depends on how the VGs are installed (and whether you have the altitude to recover). My own VGs have been tried at three different locations and do help, but my short wings are prone to wing drop. Link to comment Share on other sites More sharing options...
turboplanner Posted October 28, 2016 Share Posted October 28, 2016 OK, haved a close look at the V115 I posted; I can't remember whether there was anything special at the wing root, just remember a normal join with non-skid material glued to the top surface for a walkway. While it had a short wingspan, it was a very stable aircraft to fly, and I stalled it power off and power on with a pronounced nose up attitude many times (in the straight ahead position) and can't remember any wing drops. 1 1 Link to comment Share on other sites More sharing options...
Old Koreelah Posted October 28, 2016 Share Posted October 28, 2016 OK, haved a close look at the V115 I posted... Thanks for that Turbs, but the only reference to the V115 I could find in one of your posts doesn't mention stalling. 1 Link to comment Share on other sites More sharing options...
turboplanner Posted October 28, 2016 Share Posted October 28, 2016 See post #63 Link to comment Share on other sites More sharing options...
Old Koreelah Posted October 28, 2016 Share Posted October 28, 2016 See post #63 Still a bit too cryptic for me. Link to comment Share on other sites More sharing options...
turboplanner Posted October 28, 2016 Share Posted October 28, 2016 I stalled it power off and power on with a pronounced nose up attitude many times (in the straight ahead position) and can't remember any wing drops. Link to comment Share on other sites More sharing options...
Old Koreelah Posted October 28, 2016 Share Posted October 28, 2016 I stalled it power off and power on with a pronounced nose up attitude many times (in the straight ahead position) and can't remember any wing drops. Yes Turbs, I had read that bit, but your post "OK, haved a close look at the V115 I posted" had me looking for a previous post with more detail. I'll look at a Victa 115 wing to see what I can learn. Link to comment Share on other sites More sharing options...
turboplanner Posted October 28, 2016 Share Posted October 28, 2016 The photo I posted is #46; looks a clean wing. 1 Link to comment Share on other sites More sharing options...
djpacro Posted October 29, 2016 Share Posted October 29, 2016 I'll look at a Victa 115 wing to see what I can learn. You should see that it is a copy of the Provost wing. Different aerofoil sections root to tip combined with washout designed to give good stall behaviour - didn't quite work as inboard leading edge stall strips were required. The Model T-6 doesn't have those stall strips and, in my opinion, is stretching FAR 23 requirements for uncommanded roll at the stall.See page 13 of http://airtourer.asn.au/airtourer/images/Newsletter/Newsletter%20153.pdf (from memory, not quite right - it is a 23012 not a 2312) 1 1 Link to comment Share on other sites More sharing options...
Oscar Posted October 29, 2016 Share Posted October 29, 2016 OK, Dafydd Llewellyn worked at Victa with Henry M. I don't think he worked on the four-seater, but may be able to give you some background on the l/e 'cuff' aerodynamics. Link to comment Share on other sites More sharing options...
Old Koreelah Posted October 29, 2016 Share Posted October 29, 2016 OK, Dafydd Llewellyn worked at Victa with Henry M. I don't think he worked on the four-seater, but may be able to give you some background on the l/e 'cuff' aerodynamics. Oscar he's already spent lots of time helping me with my wing fences and stall strips (although I've haven't yet completed testing them.) The LE cuffs that DJP is referring to is what intrigue me. My mate's Jodel D-150 has them, but I thought they were just fuel tanks. Link to comment Share on other sites More sharing options...
djpacro Posted October 29, 2016 Share Posted October 29, 2016 .... but I thought they were just fuel tanks. that's also my recollection - Henry wanted basically the same wing as the Airtourer but some more wing area and space for fuel in the Aircruiser.Regardless, I'd been looking for some sensible info on these cuffs wrt aerodynamic design of the wing/fuselage junction and effect on stall characteristics. Ideally, the local lift coefficient would be maximum at the outboard end of the cuff so stalls there first. But interference from the fuselage is significant and simple theory not really applicable. 1 Link to comment Share on other sites More sharing options...
djpacro Posted October 30, 2016 Share Posted October 30, 2016 .... looking for some sensible info on these cuffs wrt aerodynamic design of the wing/fuselage junction and effect on stall characteristics .... This is probably going to be all I can find amongst free stuff: http://www.mas.bg.ac.rs/_media/istrazivanje/fme/vol42/2/01_ikostic.pdf - see Figures 32 & 33 with associated text on that page. 1 Link to comment Share on other sites More sharing options...
Old Koreelah Posted October 30, 2016 Share Posted October 30, 2016 Thanks for that link, DJP. Too many numbers for me, but I enjoyed the piccies! The analysis of wing strikes on p104 is interesting. 1 Link to comment Share on other sites More sharing options...
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