---------------------------------------------------------- Kolb-List Digest Archive --- Total Messages Posted Mon 03/21/16: 12 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 09:08 AM - Re: FireStar 2 Kit Received ! (Richard Girard) 2. 09:29 AM - Re: long legs (Richard Girard) 3. 09:57 AM - Re: long legs (Patrick Ladd) 4. 10:22 AM - Re: long legs (Bill Berle) 5. 10:55 AM - Re: Elevator/Stabilizer hinge ass'y (Bill Berle) 6. 02:41 PM - Re: Elevator/Stabilizer hinge ass'y (Richard Girard) 7. 03:13 PM - Re: Elevator/Stabilizer hinge ass'y (Eugene Zimmerman) 8. 03:28 PM - Re: Elevator/Stabilizer hinge ass'y (Gary Aman) 9. 03:30 PM - Re: Elevator/Stabilizer hinge ass'y (Bill Berle) 10. 03:31 PM - Re: Elevator/Stabilizer hinge ass'y (Bill Berle) 11. 04:54 PM - Re: long legs (John Hauck) 12. 05:10 PM - Re: long legs (John Hauck) ________________________________ Message 1 _____________________________________ Time: 09:08:36 AM PST US Subject: Re: Kolb-List: FireStar 2 Kit Received ! From: Richard Girard Bill, IMOH powder coating is great for patio furniture, office machinery, and other expendibles, but is not suitable for an airframe. It looks great straight out of the oven, but once it gets some time on it cracks form letting moisture in and brown streaks, just like those you are seeing on your airframe, begin to form. The only solution is to grind it off and patch it with paint. I much prefer two part epoxy paint (urethanes, like Aerothane, release cyanide gas so you must have an air supply to shoot them). You can get it from O'Reilly's Auto Parts (about $40 a quart) http://www.oreillyauto.com/site/c/detail/TRS2/6101/N2541.oap?ck=Search_N2 541_-1_-1&pt=N2541&ppt=C0171 and the small gun in the Harbor Freight HVLP set (usually about $45) works great for tubes; http://www.harborfreight.com/air-tools/paint/2-pc-professional-automotive-h vlp-air-spray-gun-kit-61472.html Give it at least four days to fully harden before applying fabric if using the Poly Fiber system so the solvents won't attack the epoxy. Now you have something you can repair as necessary. Anyway, that's what I use and I like it. Also works great on aluminum parts if you alodine them first. Rick Girard On Thu, Mar 17, 2016 at 7:24 PM, Dennis Rowe wrote: > > Man, let me know if you ever want to sell Miss Pfer. =F0=9F=94=BD=F0=9F =94=BD that was quite > the sales pitch! > > Dennis "Skid" Rowe > > > > On Mar 17, 2016, at 9:22 AM, John Hauck wrote: > > > > I always thought dragging the tail boom straight, instead of sideways > through the air, would clean it up a bit and increase cruise. The SS and > Kolbra utilize that design technique with lower incidence to increase > cruise. John Williamson's Kolbra, with 912ULS, same engine on my MKIII, > cruised 10 mph faster at the same rpm. Top speed is about 10 to 15 mph > quicker. The major difference in drag between the Kolbra/SS and the MKII I > was the difference between the width and shape of the fuselage. Also, th e > Kolbra had less wing area because it did not have flaps. The MKIII flies > slower and gets off the ground quicker. > > > > Actually, the fuselage of the FS would have to be redesigned because th e > tail boom was designed to fly tail high. Flying with the tail boom > horizontal would make the pilot feel as though he were laying on his back > and climbing all the time. > > > > My original Firestar was faster and flew slower than the FSII. It had > full span ailerons. The FSII is like the Kolbra with half span. > > > > I am a firm believer is extremely tight fabric. I believe this is one > of the major differences between air speed/flight characteristic > differences of the same model Kolbs. My MKIII has never been outrun by > another MKIII. Same for my original FS. Both aircraft had fabric that > bowed the tubes on wings and empennage. Soft fabric changes shape much > more than tight fabric. > > > > There were a lot of things I would have liked to experiment with my > Kolbs over the last 32 years, but age caught up with me before I got them > all done. Then I got to the stage that what I have now is great. It doe s > what I need. It is an 85 mph cruise aircraft. If I can find a 15 mph > tailwind, then I've got a temporary 100 mph airplane across the ground. It > will carry everything I can cram into it to keep me and it going for > extended periods of time. So far, the longest duration flight was 48 > days. The longest flight was 17,400 sm in 41 days and 232.0 flight hours .. > It will keep me in the air for 5 hours, if I could do that without wettin g > my pants. It gets me in and out of tiny fields, two track trails, gravel > bars, beaches on the Atlantic, the Gulf of Mexico, the Arctic Ocean, and > small dry lakes in the dessert. It does much more than Homer Kolb and Jo hn > Hauck ever dreamed one of his little airplanes would do. It takes me whe re > I want to go. All I have to do is! > put gas in it, take off and point the nose in that direction. > > > > john h > > mkIII > > Titus, Alabama > > > > > > > > -----Original Message----- > > From: owner-kolb-list-server@matronics.com [mailto: > owner-kolb-list-server@matronics.com] On Behalf Of Bill Berle > > Sent: Thursday, March 17, 2016 3:01 AM > > To: kolb-list@matronics.com > > Subject: RE: FW: Kolb-List: FireStar 2 Kit Received ! > > > > > > I have no Kolb experience whatsoever. This is my first Kolb. So some of > my ideas may not work out as well as I hope, and some of them may work > better than I imagined. The challenge and enjoyment of improving the > performance of an already good airplane is one of the things I'm looking > forward to. > > > > I have a specific question which you might be able to answer: If you pu t > the wing on a FireStar at the lower incidence angle of the Slingshot, and > then put on the taller gear from the Slingshot, would you get both benefi ts > (a higher cruise speed from the tailboom flying straight), AND better STO L > performance (from the higher ground angle)? > > > > Bill Berle > > www.ezflaphandle.com - safety & performance upgrade for light aircraft > www.grantstar.net - winning proposals for non-profit and > for-profit entities > > > > -------------------------------------------- > > On Wed, 3/16/16, John Hauck wrote: > > > > Subject: RE: FW: Kolb-List: FireStar 2 Kit Received ! > > To: kolb-list@matronics.com > > Date: Wednesday, March 16, 2016, 8:03 PM > > > > "John Hauck" > > > > Hi Folks: > > > > The paragraphs in quotation marks are Bill B's. > > > > Homer Kolb didn't design the Kolbra. That aircraft was designed and > built some time after the original Kolb Aircraft Co was sold. > > > > "Mr. Kolb himself changed the wing dimensions to create the Slingshot, > Kolbra, Firelfy, and others. He also changed the angle of incidence (win g > mounting angle) to create different characteristics on different models. " > > > > All Kolb wing dimensions are the same, except length of the wing > panel. Shape of the rib and cord is the same on all models. > > > > The Slingshot had less incidence because of the high main gear and the > nose high attitude the aircraft sat on the ground. It also flew faster, > pulling the tail boom parallel through the air stream. At slower speeds > the SS really drags its tail. Very tail low. Other Kolb models fly > tail high because of the excessive incidence. > > > > "Raked wingtips are shown to work, especially at high AoA and low > speeds. They create a pressure field that slightly reduces the wingtip > vortex." > > > > I think you will find that Homer's wingtip takes care of the above. > > > > "VG's are shown to work great, especially on simple turbulent flow > airfoils like the Cub, Kolb, and Aeronca. > > They help the airflow stay attached to the wing at higher AoA. This > results in better control authority at low speeds, which will be a > lifesaver in off-airport STOL operations." > > > > All Kolb models have excellent low speed flight characteristics withou t > VGs. About the only thing I have been able to determine with the additi on > of VGs on a Kolb is more gentle break on landing, and slightly less sta ll > speed. > > > > "Mr. Kolb designed the landing gear to be as easy and low-risk for new > or low-time pilots as possible. It worked, and the Kolb has a wonderful > reputation for easy ground handling. This is just what the doctor ordere d > for a kit plane that was safe for low time pilots. But this mellow grou nd > handling comes at the cost of losing the ideal ground angle for the win g > to take off and land slower. A longer or taller landing gear requires a > slightly more experienced pilot, but you get better STOL performance in > the bargain." > > > > The Hauck Brothers have been designing and building "tall" > > landing gear for Kolb aircraft for 30 years. We put the first pair of > heat treated 4130 legs on a Kolb. The main reason we started experimenti ng > with long legs on my FS was the lack of brakes. One of the first mods t o > my FS was 4130 streamlined lift struts. They cleaned up the FS so much I > couldn't get it stopped on my short grass strip. The 36" legs turned th e > bottom of the wing up more and helped slow the FS down on landing. They > also made nice springs, and worked wonders for softening up the suspensi on. > > > > BTW Bill B, tell us about your Kolb experience, please. > > > > john h > > mkIII > > Titus, Alabama > > > > > > > > > > > > > > > > > > > > > > Lists This Month -- > > Some AWESOME FREE Gifts!) > > Raiser. Click on > > more about > > Gifts provided > > www.buildersbooks.com > > -Matt > > Dralle, List Admin. > > Forum - > > - MATRONICS WEB FORUMS - > > List Contribution Web Site - > > -Matt > > Dralle, List Admin. > > > > > > > > > > > > > > > > > > > > =========== =========== =========== =========== =========== > > -- =9CBlessed are the cracked, for they shall let in the light.=9D Groucho Marx ________________________________ Message 2 _____________________________________ Time: 09:29:27 AM PST US Subject: Re: Kolb-List: long legs From: Richard Girard Patrick, My Mk III has aluminum legs, my friend's Mk IIIX has steel legs and lower wing incidence. Neither can get a full stall landing. If I do I land tail wheel first. Perhaps a full stall landing could be achieved with longer legs and higher incidence. When I get my Mk III rebuilt perhaps I'll know. Rick Girard On Sat, Mar 19, 2016 at 10:26 AM, Charlie England wrote: > Since typical AOA is around 14-15 degrees at stall, a 1.5 degree increase > could be close to a 10% increase in 3 point attitude. Not something to > sneeze at. > > Again, you must decide if it applies to Kolbs, and whether it actually > matters to you for your style of flying. Who would think that a stock Sup er > Cub needed shorter field performance, but a lot of bush fliers obviously > consider it inadequate for their purposes. > > On Sat, Mar 19, 2016 at 9:40 AM, Patrick Ladd > wrote: > >> Thanks Charlie, >> i can see the reasoning and in fact I saw a guy up in Fairbanks in a >> Super Cub pulling the `tail up, full throttle trick`. He powered up, >> standing on the brakes, hauled it off the ground by pushing the tail dow n >> and climbing out at just above stall speed.. He did a circuit and landed >> again, tail down and hanging on his prop at full chat, like a helicopte r. >> All in an incredibly short time. I filmed it with a video camera in one >> take. >> I somehow doubt that many Kolbers have the brakes, to be able to come >> close to emulating that performance. Without some actual measurements it is >> impossible to calculate accurately the increased AOA available and I was >> never any good at trig anyway but assuming 10ft between mains and tail >> wheel and an increase in height of the gear legs of say 4 inches, by how >> many degrees does that increase the AOA? 1 degree? 1.5 degrees.? No doub t >> someone on the list will work it out. >> It may well be worth extending legs for other reasons but STOL?. >> Questionable. >> >> Pat >> >> *From:* Charlie England >> *Sent:* Saturday, March 19, 2016 1:34 PM >> *To:* kolb-list@matronics.com >> *Subject:* Re: Kolb-List: long legs >> >> >> >> On Sat, Mar 19, 2016 at 5:58 AM, Patrick Ladd >> wrote: >> >>> I may be sticking my neck out here and asking get slapped down but will >>> someone explain why having longer legs increases the STOL capability of our >>> a/c. Excepting of course the case where you deliberately hold the tail down >>> on take off. >>> I agree with all the advantages which John listed, more wing area >>> exposed thus slowing landing run etc. However the first thing which mo st >>> of us do on take off is to get the tail up into flying position thus >>> reducing drag and allowing increased acceleration. When the tail is up the >>> the length of the u/c is irrelevant. In fact having the extra wing area >>> exposed by having long legs slows the planes acceleration for exactly t he >>> same reason that it shortens the landing run. >>> When the plane is up on two wheels the AOA is that which was designed i n. >>> Comments about commercial a/c are largely irrelevant as they are >>> (mainly) tricycle gear and the wing is in flying position (more or less ) >>> the whole time. >>> There may be good reasons for making u/c legs longer but I am not >>> convinced that STOL is one of them except the `keep the skid on the gr ound >>> until she drags herself off` scenario which I mentioned.. >>> Enlightenment please. >>> Pat >>> >> >> I'll take a crack at it, in general terms. You can decide if it applies >> to Kolbs. >> >> If you watch videos of hard core bush flying, the pilot will hold the >> brakes and raise the tail prior to starting the takeoff roll (to minimiz e >> wing drag, as you point out). When he's got max available power, he >> releases the brakes. As soon as he's got minimum flying speed, he rotate s & >> the plane jumps into the air. Now, most taildraggers sit on the ground w ith >> the wing at a significantly lower angle than critical (stall) AOA. So in >> stock condition, they can't be rotated to lift off at anywhere near stal l >> speed. So, their minimum speed for takeoff is limited (made higher) by t he >> length of the main gear legs. If the same trick is tried with 'short leg s', >> the pilot would slam the tailwheel into the ground when he rotates. FWIW , >> there are videos of airliners actually dragging the rear of the fuselage on >> the ground when they over-rotate. Airliners (at least some of them) >> actually give up significant landing speed reduction because they don't >> want the weight of long gear legs when they always have plenty of runway >> for 'driving it on' in landing. >> >> In landing mode, it's just as important. In normal flying, a pilot would >> try to '3 point', having the mains & tailwheel touch at the same time to >> land at minimum airspeed. But, since the wing isn't at critical AOA in 3 >> point attitude, he's not really landing at minimum airspeed. If the main s >> were longer, he could land slower. In bush flying, it gets worse. Again, >> watching extreme bush flying, you'll see the pilot wheel land and keep t he >> tail off the ground until he's almost stopped. With a typical taildragge r, >> he's carrying quite a bit of extra airspeed to 'wheel land' the plane, b ut >> he does it to protect the tailwheel from damage, from rough ground and f rom >> impact damage of dropping it in. If the legs are extended enough, he can >> have full stall AOA available from the wing, without the tailwheel being on >> the ground. Obviously, this will let him land slower & shorter. >> >> Does any of that apply to Kolbs? >> > > -- =9CBlessed are the cracked, for they shall let in the light.=9D Groucho Marx ________________________________ Message 3 _____________________________________ Time: 09:57:58 AM PST US From: Patrick Ladd Subject: Re: Kolb-List: long legs I look forward to a definitive statement. The guy in the Super Cub, at full throttle, lowered his plane onto the tail wheel at almost nil forward speed, cut back on the throttle and then the mains crashed down onto its balloon bush tyres.Hard on the system. Breaking my heart not to have a plane to fly any more. We have had a week in the middle of a large High pressure system. Glorious flying weather and me stuck here playing with a 18=9D diameter quadrocopter my wife bought me fro Christmas.Oh! Bugger. Pat From: Richard Girard Sent: Monday, March 21, 2016 4:29 PM Subject: Re: Kolb-List: long legs Patrick, My Mk III has aluminum legs, my friend's Mk IIIX has steel legs and lower wing incidence. Neither can get a full stall landing. If I do I land tail wheel first. Perhaps a full stall landing could be achieved with longer legs and higher incidence. When I get my Mk III rebuilt perhaps I'll know. Rick Girard On Sat, Mar 19, 2016 at 10:26 AM, Charlie England wrote: Since typical AOA is around 14-15 degrees at stall, a 1.5 degree increase could be close to a 10% increase in 3 point attitude. Not something to sneeze at. Again, you must decide if it applies to Kolbs, and whether it actually matters to you for your style of flying. Who would think that a stock Super Cub needed shorter field performance, but a lot of bush fliers obviously consider it inadequate for their purposes. On Sat, Mar 19, 2016 at 9:40 AM, Patrick Ladd wrote: Thanks Charlie, i can see the reasoning and in fact I saw a guy up in Fairbanks in a Super Cub pulling the `tail up, full throttle trick`. He powered up, standing on the brakes, hauled it off the ground by pushing the tail down and climbing out at just above stall speed.. He did a circuit and landed again, tail down and hanging on his prop at full chat, like a helicopter. All in an incredibly short time. I filmed it with a video camera in one take. I somehow doubt that many Kolbers have the brakes, to be able to come close to emulating that performance. Without some actual measurements it is impossible to calculate accurately the increased AOA available and I was never any good at trig anyway but assuming 10ft between mains and tail wheel and an increase in height of the gear legs of say 4 inches, by how many degrees does that increase the AOA? 1 degree? 1.5 degrees.? No doubt someone on the list will work it out. It may well be worth extending legs for other reasons but STOL?. Questionable. Pat From: Charlie England Sent: Saturday, March 19, 2016 1:34 PM To: kolb-list@matronics.com Subject: Re: Kolb-List: long legs On Sat, Mar 19, 2016 at 5:58 AM, Patrick Ladd wrote: I may be sticking my neck out here and asking get slapped down but will someone explain why having longer legs increases the STOL capability of our a/c. Excepting of course the case where you deliberately hold the tail down on take off. I agree with all the advantages which John listed, more wing area exposed thus slowing landing run etc. However the first thing which most of us do on take off is to get the tail up into flying position thus reducing drag and allowing increased acceleration. When the tail is up the the length of the u/c is irrelevant. In fact having the extra wing area exposed by having long legs slows the planes acceleration for exactly the same reason that it shortens the landing run. When the plane is up on two wheels the AOA is that which was designed in. Comments about commercial a/c are largely irrelevant as they are (mainly) tricycle gear and the wing is in flying position (more or less) the whole time. There may be good reasons for making u/c legs longer but I am not convinced that STOL is one of them except the `keep the skid on the ground until she drags herself off` scenario which I mentioned.. Enlightenment please. Pat I'll take a crack at it, in general terms. You can decide if it applies to Kolbs. If you watch videos of hard core bush flying, the pilot will hold the brakes and raise the tail prior to starting the takeoff roll (to minimize wing drag, as you point out). When he's got max available power, he releases the brakes. As soon as he's got minimum flying speed, he rotates & the plane jumps into the air. Now, most taildraggers sit on the ground with the wing at a significantly lower angle than critical (stall) AOA. So in stock condition, they can't be rotated to lift off at anywhere near stall speed. So, their minimum speed for takeoff is limited (made higher) by the length of the main gear legs. If the same trick is tried with 'short legs', the pilot would slam the tailwheel into the ground when he rotates. FWIW, there are videos of airliners actually dragging the rear of the fuselage on the ground when they over-rotate. Airliners (at least some of them) actually give up significant landing speed reduction because they don't want the weight of long gear legs when they always have plenty of runway for 'driving it on' in landing. In landing mode, it's just as important. In normal flying, a pilot would try to '3 point', having the mains & tailwheel touch at the same time to land at minimum airspeed. But, since the wing isn't at critical AOA in 3 point attitude, he's not really landing at minimum airspeed. If the mains were longer, he could land slower. In bush flying, it gets worse. Again, watching extreme bush flying, you'll see the pilot wheel land and keep the tail off the ground until he's almost stopped. With a typical taildragger, he's carrying quite a bit of extra airspeed to 'wheel land' the plane, but he does it to protect the tailwheel from damage, from rough ground and from impact damage of dropping it in. If the legs are extended enough, he can have full stall AOA available from the wing, without the tailwheel being on the ground. Obviously, this will let him land slower & shorter. Does any of that apply to Kolbs? -- =9CBlessed are the cracked, for they shall let in the light.=9D Groucho Marx ________________________________ Message 4 _____________________________________ Time: 10:22:56 AM PST US From: Bill Berle Subject: Re: Kolb-List: long legs >From my research, and hearing from other people who have been around Kolbs for many many years, I think it is safe to say that Homer Kolb designed this series of aircraft for good handling, good manners, and able to be flown easily by a low time pilot. By all accounts he succeeded and created a fantastic little airplane. But physics do not lie... in order to be a great airplane in one area, design sacrifices must be made in some other area. This is why a LearJet is not appropriate for a low time pilot, and this is why a Cessna 172 is (usually) not very exciting for a high time pilot. I have no doubt that Mr. Kolb understood this, and chose safety/easy handling over maximum possible performance. The sales and success of the Kolb fleet has proven him right. The Kolbs are world renowned for being docile and not demanding. The price paid for that is that some performance has been sacrificed. Raising the ground angle high enough so that the airplane can perform a full-stall 3 point landing will clearly allow the airplane to realize the maximum STOL performance that the wing and engine combination is capable of delivering. That is basic textbook aeroduynamics. But since the Kolb apparently has good STOL performance with the stock configuration, it's been a non-issue for the majority of Kolb pilots. Speaking ONLY for myself, I would like to maximize the STOL performance of my aircraft, because I am heavier than an average pilot, and my airplane will not meet the 254 UL weight either. So rather than having to put a $20K, 100HP engine on it, I believe I will get 2/3 of the same benefit by having a tall enough landing gear for the wing to fly sooner. The price I have to pay for that is that I cannot be a low-time, beginner pilot, and the airplane will be a little slower (higher drag and drag further underneath the CG). The modifications that I am planning for my aircraft will not be for everyone. But I'm hopeful that they will suit my needs. Bill Berle www.ezflaphandle.com - safety & performance upgrade for light aircraft www.grantstar.net - winning proposals for non-profit and for-profit entities -------------------------------------------- On Mon, 3/21/16, Richard Girard wrote: Subject: Re: Kolb-List: long legs To: "kolb-list@matronics.com" Date: Monday, March 21, 2016, 9:29 AM Patrick, My Mk III has aluminum legs, my friend's Mk IIIX has steel legs and lower wing incidence. Neither can get a full stall landing. If I do I land tail wheel first. Perhaps a full stall landing could be achieved with longer legs and higher incidence. When I get my Mk III rebuilt perhaps I'll know. Rick Girard On Sat, Mar 19, 2016 at 10:26 AM, Charlie England wrote: Since typical AOA is around 14-15 degrees at stall, a 1.5 degree increase could be close to a 10% increase in 3 point attitude. Not something to sneeze at. Again, you must decide if it applies to Kolbs, and whether it actually matters to you for your style of flying. Who would think that a stock Super Cub needed shorter field performance, but a lot of bush fliers obviously consider it inadequate for their purposes. On Sat, Mar 19, 2016 at 9:40 AM, Patrick Ladd wrote: Thanks Charlie, i can see the reasoning and in fact I saw a guy up in Fairbanks in a Super Cub pulling the `tail up, full throttle trick`. He powered up, standing on the brakes, hauled it off the ground by pushing the tail down and climbing out at just above stall speed.. He did a circuit and landed again, tail down and hanging on his prop at full chat, like a helicopter. All in an incredibly short time. I filmed it with a video camera in one take. I somehow doubt that many Kolbers have the brakes, to be able to come close to emulating that performance. Without some actual measurements it is impossible to calculate accurately the increased AOA available and I was never any good at trig anyway but assuming 10ft between mains and tail wheel and an increase in height of the gear legs of say 4 inches, by how many degrees does that increase the AOA? 1 degree? 1.5 degrees.? No doubt someone on the list will work it out. It may well be worth extending legs for other reasons but STOL?. Questionable. Pat From: Charlie England Sent: Saturday, March 19, 2016 1:34 PM To: kolb-list@matronics.com Subject: Re: Kolb-List: long legs On Sat, Mar 19, 2016 at 5:58 AM, Patrick Ladd wrote: I may be sticking my neck out here and asking get slapped down but will someone explain why having longer legs increases the STOL capability of our a/c. Excepting of course the case where you deliberately hold the tail down on take off. I agree with all the advantages which John listed, more wing area exposed thus slowing landing run etc. However the first thing which most of us do on take off is to get the tail up into flying position thus reducing drag and allowing increased acceleration. When the tail is up the the length of the u/c is irrelevant. In fact having the extra wing area exposed by having long legs slows the planes acceleration for exactly the same reason that it shortens the landing run. When the plane is up on two wheels the AOA is that which was designed in. Comments about commercial a/c are largely irrelevant as they are (mainly) tricycle gear and the wing is in flying position (more or less) the whole time. There may be good reasons for making u/c legs longer but I am not convinced that STOL is one of them except the `keep the skid on the ground until she drags herself off` scenario which I mentioned.. Enlightenment please. Pat I'll take a crack at it, in general terms. You can decide if it applies to Kolbs. If you watch videos of hard core bush flying, the pilot will hold the brakes and raise the tail prior to starting the takeoff roll (to minimize wing drag, as you point out). When he's got max available power, he releases the brakes. As soon as he's got minimum flying speed, he rotates & the plane jumps into the air. Now, most taildraggers sit on the ground with the wing at a significantly lower angle than critical (stall) AOA. So in stock condition, they can't be rotated to lift off at anywhere near stall speed. So, their minimum speed for takeoff is limited (made higher) by the length of the main gear legs. If the same trick is tried with 'short legs', the pilot would slam the tailwheel into the ground when he rotates. FWIW, there are videos of airliners actually dragging the rear of the fuselage on the ground when they over-rotate. Airliners (at least some of them) actually give up significant landing speed reduction because they don't want the weight of long gear legs when they always have plenty of runway for 'driving it on' in landing. In landing mode, it's just as important. In normal flying, a pilot would try to '3 point', having the mains & tailwheel touch at the same time to land at minimum airspeed. But, since the wing isn't at critical AOA in 3 point attitude, he's not really landing at minimum airspeed. If the mains were longer, he could land slower. In bush flying, it gets worse. Again, watching extreme bush flying, you'll see the pilot wheel land and keep the tail off the ground until he's almost stopped. With a typical taildragger, he's carrying quite a bit of extra airspeed to 'wheel land' the plane, but he does it to protect the tailwheel from damage, from rough ground and from impact damage of dropping it in. If the legs are extended enough, he can have full stall AOA available from the wing, without the tailwheel being on the ground. Obviously, this will let him land slower & shorter. Does any of that apply to Kolbs? -- Blessed are the cracked, for they shall let in the light. Groucho Marx ________________________________ Message 5 _____________________________________ Time: 10:55:52 AM PST US From: Bill Berle Subject: Re: Kolb-List: Elevator/Stabilizer hinge ass'y Are there any Kolb people on this list who are qualified mechanical or aero-structure engineers? I want to ask a question about the tail attachment mechanism. Before I even mention the question, I want to assure everyone that I AM COMPLETELY AWARE that there are X thousand Kolbs flying around safely with this stabilizer attachment. I understand that there have not been many (or perhaps any) failures of this mechanism. What I am asking about is the theoretical "correctness" of the design, and whether any other "old-school" airplane people think that this system is a little wonky. It took a few moments to finally understand how the mechanism works, and after looking at everything several times it was clear that there is no direct structural attachment between the main spar tube of the stabilizer to the fuselage tube (tailboom). The primary structural load path between the root end of the main stabilizer spar tube and the fuselage is transmitted through the elevator hinge... and this hinge isn't even the aircraft style extruded hinge. So if the air loads try to lift up or push down on the root end of the stabilizer, it puts all that load through the hinge, into the elevator pivot, and then finally into the steel ring at the back of the fuselage. But that's not even the biggest issue in my head. The larger issue is that (according to plan) the flat hinge is riveted to the tubes along one thin "point of contact" line tangent to the tube. So the root stabilizer load is all acting on a hinge, which itself is cantilevered off of one tangent point on the tube. Now I'm not a degreed engineer, and I'm not a mathematician. So I called a friend of mine who is a retired aerospace structural engineer, with 50+ years of experience. I showed him the plans and explained my concern, and I was informed that my concerns about this system were valid. My Kolb will be built with a more stable attachment. My question for any real, degreed, qualified, aircraft-experience engineers is... has anyone looked at the stabilizer root attachment load path and had these same concerns? ONCE AGAIN, this is not an attack on Mr. Kolb or his design, and it is not intended to cause any panic or concern at this point. What I want to know is why this load path - through two tangent mounted hinge halves, into a movable elevator, and then into the fuselage - is good enough, and why it was not appropriate to install an attachment bracket onto the fuselage at the rear stabilizer spar. Bill Berle www.ezflaphandle.com - safety & performance upgrade for light aircraft www.grantstar.net - winning proposals for non-profit and for-profit entities ________________________________ Message 6 _____________________________________ Time: 02:41:00 PM PST US Subject: Re: Kolb-List: Elevator/Stabilizer hinge ass'y From: Richard Girard The rear attachment of the horizontal stabilizer is NOT through the hinge. It is through the rear folding weldments that also act as the inner hinge. When it is set up correctly the hinge line is on the same center as the swivel bolt in the weldment, however there is some allowance for misalignment. In that case the weldment in the elevator spar (forward tube of the elevator), can slide on the bolt in the swivel weldment. I've seen folding mechanisms on the Kit Fox and repaired the mechanism on the Highlander and in my HO Homer's is the most clever. All you have to do to fold the HS on a Kolb is to take out a single bolt that attaches the lower wires to the rudder post. I'm not sure how you would make it any simpler. Rick Girard On Mon, Mar 21, 2016 at 12:55 PM, Bill Berle wrote: > > Are there any Kolb people on this list who are qualified mechanical or > aero-structure engineers? I want to ask a question about the tail > attachment mechanism. > > Before I even mention the question, I want to assure everyone that I AM > COMPLETELY AWARE that there are X thousand Kolbs flying around safely wit h > this stabilizer attachment. I understand that there have not been many (o r > perhaps any) failures of this mechanism. What I am asking about is the > theoretical "correctness" of the design, and whether any other "old-schoo l" > airplane people think that this system is a little wonky. > > It took a few moments to finally understand how the mechanism works, and > after looking at everything several times it was clear that there is no > direct structural attachment between the main spar tube of the stabilizer > to the fuselage tube (tailboom). The primary structural load path between > the root end of the main stabilizer spar tube and the fuselage is > transmitted through the elevator hinge... and this hinge isn't even the > aircraft style extruded hinge. > > So if the air loads try to lift up or push down on the root end of the > stabilizer, it puts all that load through the hinge, into the elevator > pivot, and then finally into the steel ring at the back of the fuselage. > > But that's not even the biggest issue in my head. The larger issue is tha t > (according to plan) the flat hinge is riveted to the tubes along one thin > "point of contact" line tangent to the tube. So the root stabilizer load is > all acting on a hinge, which itself is cantilevered off of one tangent > point on the tube. > > Now I'm not a degreed engineer, and I'm not a mathematician. So I called a > friend of mine who is a retired aerospace structural engineer, with 50+ > years of experience. I showed him the plans and explained my concern, and I > was informed that my concerns about this system were valid. My Kolb will be > built with a more stable attachment. > > My question for any real, degreed, qualified, aircraft-experience > engineers is... has anyone looked at the stabilizer root attachment load > path and had these same concerns? > > ONCE AGAIN, this is not an attack on Mr. Kolb or his design, and it is no t > intended to cause any panic or concern at this point. What I want to know > is why this load path - through two tangent mounted hinge halves, into a > movable elevator, and then into the fuselage - is good enough, and why it > was not appropriate to install an attachment bracket onto the fuselage at > the rear stabilizer spar. > > > Bill Berle > www.ezflaphandle.com - safety & performance upgrade for light aircraft > www.grantstar.net - winning proposals for non-profit and > for-profit entities > > =========== =========== =========== =========== =========== > > -- =9CBlessed are the cracked, for they shall let in the light.=9D Groucho Marx ________________________________ Message 7 _____________________________________ Time: 03:13:42 PM PST US From: Eugene Zimmerman Subject: Re: Kolb-List: Elevator/Stabilizer hinge ass'y > On Mar 21, 2016, at 1:55 PM, Bill Berle wrote: > So I called a friend of mine who is a retired aerospace structural engineer, with 50+ years of experience. LOL The cognitive acuity of anyone with 50+ years of experience should probably be suspect. Trust me, I have 50+ years of experience. ;) ________________________________ Message 8 _____________________________________ Time: 03:28:27 PM PST US From: Gary Aman Subject: Re: Kolb-List: Elevator/Stabilizer hinge ass'y Have to realize Bill,we are talking sub sonic here.A Kolb may not be what you=99re looking for if you don=99t care what it weighs.A TBM may be down your ally.I hear they=99re pretty stout .Good luck finding a kit. > On Mar 21, 2016, at 6:13 PM, Eugene Zimmerman wrote: > > >> On Mar 21, 2016, at 1:55 PM, Bill Berle > wrote: > >> So I called a friend of mine who is a retired aerospace structural engineer, with 50+ years of experience. > > LOL > > The cognitive acuity of anyone with 50+ years of experience should probably be suspect. > Trust me, I have 50+ years of experience. ;) ________________________________ Message 9 _____________________________________ Time: 03:30:07 PM PST US From: Bill Berle Subject: Re: Kolb-List: Elevator/Stabilizer hinge ass'y I hope I'm wrong, but my review of the plans indicated that there is no traditional DIRECT structural connection between the rear spar tube and the fuselage tube. All the load paths have to take a serpentine route and go rearward through the elevator hinges first, and only then into the U-joint and pivot bolt in the steel ring. If you removed the elevator hinges (from either the elevator or the stabilizer), or if you took the pin out of the hinges, you could move the stabilizer up and down freely while the elevator remained bolted to the fuselage. Even WITH all the hinges in place, all up and down movement of the stabilizer is transmitted through the rivets that hold the hinge onto the tubes, and there is no significant stiffness or bracing against this movement. Essentially you could move the root end of the stabilizer up and down by hand and this movement would bend the (un-supported section of) the hinge material. This would attempt to pry the rivets out of the tube and/or bend the thin metal back and forth. Also, because of this design the forward stabilizer attach bolt must be a loose fit, and the stabilizer has to be able to slide back and forth a little. The only thing that is gained by this unusual structural load path is that 4 ounces of weight for a pair of fittings (at the rear stabilizer spar) is saved. Can any one explain to me why this was a good bargain? Bill Berle www.ezflaphandle.com - safety & performance upgrade for light aircraft www.grantstar.net - winning proposals for non-profit and for-profit entities -------------------------------------------- On Mon, 3/21/16, Richard Girard wrote: Subject: Re: Kolb-List: Elevator/Stabilizer hinge ass'y To: "kolb-list@matronics.com" Date: Monday, March 21, 2016, 2:40 PM The rear attachment of the horizontal stabilizer is NOT through the hinge. It is through the rear folding weldments that also act as the inner hinge. When it is set up correctly the hinge line is on the same center as the swivel bolt in the weldment, however there is some allowance for misalignment. In that case the weldment in the elevator spar (forward tube of the elevator), can slide on the bolt in the swivel weldment.I've seen folding mechanisms on the Kit Fox and repaired the mechanism on the Highlander and in my HO Homer's is the most clever. All you have to do to fold the HS on a Kolb is to take out a single bolt that attaches the lower wires to the rudder post. I'm not sure how you would make it any simpler. Rick Girard On Mon, Mar 21, 2016 at 12:55 PM, Bill Berle wrote: Bill Berle Are there any Kolb people on this list who are qualified mechanical or aero-structure engineers? I want to ask a question about the tail attachment mechanism. Before I even mention the question, I want to assure everyone that I AM COMPLETELY AWARE that there are X thousand Kolbs flying around safely with this stabilizer attachment. I understand that there have not been many (or perhaps any) failures of this mechanism. What I am asking about is the theoretical "correctness" of the design, and whether any other "old-school" airplane people think that this system is a little wonky. It took a few moments to finally understand how the mechanism works, and after looking at everything several times it was clear that there is no direct structural attachment between the main spar tube of the stabilizer to the fuselage tube (tailboom). The primary structural load path between the root end of the main stabilizer spar tube and the fuselage is transmitted through the elevator hinge... and this hinge isn't even the aircraft style extruded hinge. So if the air loads try to lift up or push down on the root end of the stabilizer, it puts all that load through the hinge, into the elevator pivot, and then finally into the steel ring at the back of the fuselage. But that's not even the biggest issue in my head. The larger issue is that (according to plan) the flat hinge is riveted to the tubes along one thin "point of contact" line tangent to the tube. So the root stabilizer load is all acting on a hinge, which itself is cantilevered off of one tangent point on the tube. Now I'm not a degreed engineer, and I'm not a mathematician. So I called a friend of mine who is a retired aerospace structural engineer, with 50+ years of experience. I showed him the plans and explained my concern, and I was informed that my concerns about this system were valid. My Kolb will be built with a more stable attachment. My question for any real, degreed, qualified, aircraft-experience engineers is... has anyone looked at the stabilizer root attachment load path and had these same concerns? ONCE AGAIN, this is not an attack on Mr. Kolb or his design, and it is not intended to cause any panic or concern at this point. What I want to know is why this load path - through two tangent mounted hinge halves, into a movable elevator, and then into the fuselage - is good enough, and why it was not appropriate to install an attachment bracket onto the fuselage at the rear stabilizer spar. Bill Berle www.ezflaphandle.com - safety & performance upgrade for light aircraft www.grantstar.net - winning proposals for non-profit and for-profit entities ========== br> fts!) r> > w.buildersbooks.com" rel="noreferrer" target="_blank">www.buildersbooks.com rel="noreferrer" target="_blank">http://www.matronics.com/contribution -Matt Dralle, List Admin. ========== -List" rel="noreferrer" target="_blank">http://www.matronics.com/Navigator?Kolb-List ========== FORUMS - eferrer" target="_blank">http://forums.matronics.com ========== b Site - -Matt Dralle, List Admin. rel="noreferrer" target="_blank">http://www.matronics.com/contribution ========== -- Blessed are the cracked, for they shall let in the light. Groucho Marx ________________________________ Message 10 ____________________________________ Time: 03:31:32 PM PST US From: Bill Berle Subject: Re: Kolb-List: Elevator/Stabilizer hinge ass'y Understood, but in this case the person in question is sharp as a tack. It's MY cognitive acuity that is suspect ! Bill Berle www.ezflaphandle.com - safety & performance upgrade for light aircraft www.grantstar.net - winning proposals for non-profit and for-profit entities -------------------------------------------- On Mon, 3/21/16, Eugene Zimmerman wrote: Subject: Re: Kolb-List: Elevator/Stabilizer hinge ass'y To: "Kolb list" Date: Monday, March 21, 2016, 3:13 PM On Mar 21, 2016, at 1:55 PM, Bill Berle wrote: So I called a friend of mine who is a retired aerospace structural engineer, with 50+ years of experience. LOL The cognitive acuity of anyone with 50+ years of experience should probably be suspect.Trust me, I have 50+ years of experience. ;) ________________________________ Message 11 ____________________________________ Time: 04:54:24 PM PST US From: "John Hauck" Subject: RE: Kolb-List: long legs Rick/Kolbers: I've been experimenting and flying with heat treated 4130 tubular gear legs on Kolbs since 1987. Had 36" legs on the original FS. Completely different main gear on my MKIII, with axles 8" forward and nice nose high attitude. Yes, they did and do fine full stall landings, get off the ground quick, and have no nose over problems, even at full throttle and brakes. john h mkIII Fort Campbell, Kentucky From: owner-kolb-list-server@matronics.com [mailto:owner-kolb-list-server@matronics.com] On Behalf Of Richard Girard Sent: Monday, March 21, 2016 11:29 AM Subject: Re: Kolb-List: long legs Patrick, My Mk III has aluminum legs, my friend's Mk IIIX has steel legs and lower wing incidence. Neither can get a full stall landing. If I do I land tail wheel first. Perhaps a full stall landing could be achieved with longer legs and higher incidence. When I get my Mk III rebuilt perhaps I'll know. Rick Girard On Sat, Mar 19, 2016 at 10:26 AM, Charlie England wrote: Since typical AOA is around 14-15 degrees at stall, a 1.5 degree increase could be close to a 10% increase in 3 point attitude. Not something to sneeze at. Again, you must decide if it applies to Kolbs, and whether it actually matters to you for your style of flying. Who would think that a stock Super Cub needed shorter field performance, but a lot of bush fliers obviously consider it inadequate for their purposes. On Sat, Mar 19, 2016 at 9:40 AM, Patrick Ladd wrote: Thanks Charlie, i can see the reasoning and in fact I saw a guy up in Fairbanks in a Super Cub pulling the `tail up, full throttle trick`. He powered up, standing on the brakes, hauled it off the ground by pushing the tail down and climbing out at just above stall speed.. He did a circuit and landed again, tail down and hanging on his prop at full chat, like a helicopter. All in an incredibly short time. I filmed it with a video camera in one take. I somehow doubt that many Kolbers have the brakes, to be able to come close to emulating that performance. Without some actual measurements it is impossible to calculate accurately the increased AOA available and I was never any good at trig anyway but assuming 10ft between mains and tail wheel and an increase in height of the gear legs of say 4 inches, by how many degrees does that increase the AOA? 1 degree? 1.5 degrees.? No doubt someone on the list will work it out. It may well be worth extending legs for other reasons but STOL?. Questionable. Pat From: Charlie England Sent: Saturday, March 19, 2016 1:34 PM Subject: Re: Kolb-List: long legs On Sat, Mar 19, 2016 at 5:58 AM, Patrick Ladd wrote: I may be sticking my neck out here and asking get slapped down but will someone explain why having longer legs increases the STOL capability of our a/c. Excepting of course the case where you deliberately hold the tail down on take off. I agree with all the advantages which John listed, more wing area exposed thus slowing landing run etc. However the first thing which most of us do on take off is to get the tail up into flying position thus reducing drag and allowing increased acceleration. When the tail is up the the length of the u/c is irrelevant. In fact having the extra wing area exposed by having long legs slows the planes acceleration for exactly the same reason that it shortens the landing run. When the plane is up on two wheels the AOA is that which was designed in. Comments about commercial a/c are largely irrelevant as they are (mainly) tricycle gear and the wing is in flying position (more or less) the whole time. There may be good reasons for making u/c legs longer but I am not convinced that STOL is one of them except the `keep the skid on the ground until she drags herself off` scenario which I mentioned.. Enlightenment please. Pat I'll take a crack at it, in general terms. You can decide if it applies to Kolbs. If you watch videos of hard core bush flying, the pilot will hold the brakes and raise the tail prior to starting the takeoff roll (to minimize wing drag, as you point out). When he's got max available power, he releases the brakes. As soon as he's got minimum flying speed, he rotates & the plane jumps into the air. Now, most taildraggers sit on the ground with the wing at a significantly lower angle than critical (stall) AOA. So in stock condition, they can't be rotated to lift off at anywhere near stall speed. So, their minimum speed for takeoff is limited (made higher) by the length of the main gear legs. If the same trick is tried with 'short legs', the pilot would slam the tailwheel into the ground when he rotates. FWIW, there are videos of airliners actually dragging the rear of the fuselage on the ground when they over-rotate. Airliners (at least some of them) actually give up significant landing speed reduction because they don't want the weight of long gear legs when they always have plenty of runway for 'driving it on' in landing. In landing mode, it's just as important. In normal flying, a pilot would try to '3 point', having the mains & tailwheel touch at the same time to land at minimum airspeed. But, since the wing isn't at critical AOA in 3 point attitude, he's not really landing at minimum airspeed. If the mains were longer, he could land slower. In bush flying, it gets worse. Again, watching extreme bush flying, you'll see the pilot wheel land and keep the tail off the ground until he's almost stopped. With a typical taildragger, he's carrying quite a bit of extra airspeed to 'wheel land' the plane, but he does it to protect the tailwheel from damage, from rough ground and from impact damage of dropping it in. If the legs are extended enough, he can have full stall AOA available from the wing, without the tailwheel being on the ground. Obviously, this will let him land slower & shorter. Does any of that apply to Kolbs? -- =9CBlessed are the cracked, for they shall let in the light.=9D Groucho Marx ________________________________ Message 12 ____________________________________ Time: 05:10:05 PM PST US From: "John Hauck" Subject: RE: Kolb-List: long legs Flying a Kolb with extra long spring steel gear legs is a no brainer. It is easier to fly and ground handle than the original configuration. With long legs one does not have to worry about nosing over, as much, which is very easy with regular length legs. One does not have to be a s**t hot pilot to fly with long legs. That all changed when we designed and built the new main gear for my MKIII. By moving the axles 8" forward we placed about 100 lbs on the tail wheel which is stuck on the end of a long tail boom. I have to stay on top of and ahead of my MKIII on the ground. It is a real tail dragger with a lot of pendulum effect. Took some getting used to initially, but has paid for itself many times over the last 3300+ hours. Never been on its nose or even given a hint that it wanted to do such a nasty thing. On the other hand, a friend with a RANS S7 landed on my 750' strip a couple weeks ago. Got a little close to the end while turning around to take off. Main wheel went into a depression and the RANs ate a 1300.00 WARP Drive prop in warp speed. To maneuver on wet, rough, soft ground, and high weeds and brush, an aircraft has to have to ability to keep the tail on the ground when power is applied. A pusher aircraft does nothing to help prevent this. In fact, it helps you put you Kolb on its nose. A tractor aircraft is pulling forward and up. Our pushers are trying to rotate the Kolb around the axles and on its nose. john h mkIII Fort Campbell, KY -----Original Message----- From: owner-kolb-list-server@matronics.com [mailto:owner-kolb-list-server@matronics.com] On Behalf Of Bill Berle Sent: Monday, March 21, 2016 12:20 PM Subject: Re: Kolb-List: long legs >From my research, and hearing from other people who have been around Kolbs for many many years, I think it is safe to say that Homer Kolb designed this series of aircraft for good handling, good manners, and able to be flown easily by a low time pilot. By all accounts he succeeded and created a fantastic little airplane. But physics do not lie... in order to be a great airplane in one area, design sacrifices must be made in some other area. This is why a LearJet is not appropriate for a low time pilot, and this is why a Cessna 172 is (usually) not very exciting for a high time pilot. I have no doubt that Mr. Kolb understood this, and chose safety/easy handling over maximum possible performance. The sales and success of the Kolb fleet has proven him right. The Kolbs are world renowned for being docile and not demanding. The price paid for that is that some performance has been sacrificed. Raising the ground angle high enough so that the airplane can perform a full-stall 3 point landing will clearly allow the airplane to realize the maximum STOL performance that the wing and engine combination is capable of delivering. That is basic textbook aeroduynamics. But since the Kolb apparently has good STOL performance with the stock configuration, it's been a non-issue for the majority of Kolb pilots. Speaking ONLY for myself, I would like to maximize the STOL performance of my aircraft, because I am heavier than an average pilot, and my airplane will not meet the 254 UL weight either. So rather than having to put a $20K, 100HP engine on it, I believe I will get 2/3 of the same benefit by having a tall enough landing gear for the wing to fly sooner. The price I have to pay for that is that I cannot be a low-time, beginner pilot, and the airplane will be a little slower (higher drag and drag further underneath the CG). The modifications that I am planning for my aircraft will not be for everyone. But I'm hopeful that they will suit my needs. Bill Berle www.ezflaphandle.com - safety & performance upgrade for light aircraft www.grantstar.net - winning proposals for non-profit and for-profit entities -------------------------------------------- On Mon, 3/21/16, Richard Girard wrote: Subject: Re: Kolb-List: long legs To: "kolb-list@matronics.com" Date: Monday, March 21, 2016, 9:29 AM Patrick, My Mk III has aluminum legs, my friend's Mk IIIX has steel legs and lower wing incidence. Neither can get a full stall landing. If I do I land tail wheel first. Perhaps a full stall landing could be achieved with longer legs and higher incidence. When I get my Mk III rebuilt perhaps I'll know. Rick Girard On Sat, Mar 19, 2016 at 10:26 AM, Charlie England wrote: Since typical AOA is around 14-15 degrees at stall, a 1.5 degree increase could be close to a 10% increase in 3 point attitude. Not something to sneeze at. Again, you must decide if it applies to Kolbs, and whether it actually matters to you for your style of flying. Who would think that a stock Super Cub needed shorter field performance, but a lot of bush fliers obviously consider it inadequate for their purposes. On Sat, Mar 19, 2016 at 9:40 AM, Patrick Ladd wrote: Thanks Charlie, i can see the reasoning and in fact I saw a guy up in Fairbanks in a Super Cub pulling the `tail up, full throttle trick`. He powered up, standing on the brakes, hauled it off the ground by pushing the tail down and climbing out at just above stall speed.. He did a circuit and landed again, tail down and hanging on his prop at full chat, like a helicopter. All in an incredibly short time. I filmed it with a video camera in one take. I somehow doubt that many Kolbers have the brakes, to be able to come close to emulating that performance. Without some actual measurements it is impossible to calculate accurately the increased AOA available and I was never any good at trig anyway but assuming 10ft between mains and tail wheel and an increase in height of the gear legs of say 4 inches, by how many degrees does that increase the AOA? 1 degree? 1.5 degrees.? No doubt someone on the list will work it out. It may well be worth extending legs for other reasons but STOL?. Questionable. Pat From: Charlie England Sent: Saturday, March 19, 2016 1:34 PM To: kolb-list@matronics.com Subject: Re: Kolb-List: long legs On Sat, Mar 19, 2016 at 5:58 AM, Patrick Ladd wrote: I may be sticking my neck out here and asking get slapped down but will someone explain why having longer legs increases the STOL capability of our a/c. Excepting of course the case where you deliberately hold the tail down on take off. I agree with all the advantages which John listed, more wing area exposed thus slowing landing run etc. However the first thing which most of us do on take off is to get the tail up into flying position thus reducing drag and allowing increased acceleration. When the tail is up the the length of the u/c is irrelevant. In fact having the extra wing area exposed by having long legs slows the planes acceleration for exactly the same reason that it shortens the landing run. When the plane is up on two wheels the AOA is that which was designed in. Comments about commercial a/c are largely irrelevant as they are (mainly) tricycle gear and the wing is in flying position (more or less) the whole time. There may be good reasons for making u/c legs longer but I am not convinced that STOL is one of them except the `keep the skid on the ground until she drags herself off` scenario which I mentioned.. Enlightenment please. Pat I'll take a crack at it, in general terms. You can decide if it applies to Kolbs. If you watch videos of hard core bush flying, the pilot will hold the brakes and raise the tail prior to starting the takeoff roll (to minimize wing drag, as you point out). When he's got max available power, he releases the brakes. As soon as he's got minimum flying speed, he rotates & the plane jumps into the air. Now, most taildraggers sit on the ground with the wing at a significantly lower angle than critical (stall) AOA. So in stock condition, they can't be rotated to lift off at anywhere near stall speed. So, their minimum speed for takeoff is limited (made higher) by the length of the main gear legs. If the same trick is tried with 'short legs', the pilot would slam the tailwheel into the ground when he rotates. FWIW, there are videos of airliners actually dragging the rear of the fuselage on the ground when they over-rotate. Airliners (at least some of them) actually give up significant landing speed reduction because they don't want the weight of long gear legs when they always have plenty of runway for 'driving it on' in landing. In landing mode, it's just as important. In normal flying, a pilot would try to '3 point', having the mains & tailwheel touch at the same time to land at minimum airspeed. But, since the wing isn't at critical AOA in 3 point attitude, he's not really landing at minimum airspeed. If the mains were longer, he could land slower. In bush flying, it gets worse. Again, watching extreme bush flying, you'll see the pilot wheel land and keep the tail off the ground until he's almost stopped. With a typical taildragger, he's carrying quite a bit of extra airspeed to 'wheel land' the plane, but he does it to protect the tailwheel from damage, from rough ground and from impact damage of dropping it in. If the legs are extended enough, he can have full stall AOA available from the wing, without the tailwheel being on the ground. Obviously, this will let him land slower & shorter. Does any of that apply to Kolbs? -- Blessed are the cracked, for they shall let in the light. Groucho Marx ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message kolb-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/Kolb-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/kolb-list Browse Digests http://www.matronics.com/digest/kolb-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.