---------------------------------------------------------- Pietenpol-List Digest Archive --- Total Messages Posted Sun 02/19/06: 3 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 06:54 AM - Washout & Rigging (Rcaprd@aol.com) 2. 09:19 AM - Re: Rudder bar or rudder pedals (Dick Navratil) 3. 04:36 PM - Re: Rudder horn location (Rcaprd@aol.com) ________________________________ Message 1 _____________________________________ Time: 06:54:17 AM PST US From: Rcaprd@aol.com Subject: Pietenpol-List: Washout & Rigging In a message dated 2/18/2006 9:05:06 AM Central Standard Time, BARNSTMR@aol.com writes: Tim Willis and I have been discussing a few things off list and lately about washout. For all of you guys with flying Piets, 1) how much washout do you have? 2) have you ever tried changing it any to see if handling is improved? I recently found an interesting article about the subject. (link below) It is a a NACA report done by engineers at Texas A&M in 1953 using washout tests on a Taylorcraft. (I have been trying to investigate to see if it was my Taylorcraft. It was owned by A&M at that time). Anyway - The tests looked=20at the effects of washout and slots on lateral control near stall. The washout was varied from zero to 8 degrees. They used tufts all across the top surface of the wing to detect disturbed airflow. The idea is to have the inboard and center section of the wing stall first with the singtips still flying, so that the ailerons remain effective throughout the stall. I believe the NACA report conclusion was that 4 degrees washout was optimal for the taylorcraft and thus recommended for light planes. http://naca.larc.nasa.gov/reports/1953/naca-tn-2948/index.cgi?thumbnail11 It might be interesting to consider tests of such on the Piet wing to determine its optimum. Any thoughts? Terry B. Hey Terry, This is an area of aerodynamics that has always interested me. I tried printing the pages of that naca report, because it's easier for me to relax=20in the lazy boy chair to read, but my printer cut off the right side of the page. Here is my understanding on the subject, and what I did: A Hershey bar wing inherently stalls first at the inboard portion of the wing, and washout increases drag. Washout is much more common in Tapered Wings, because they inherently stall the tips first. Therefore, why even rig any washout in the wing ? Because any slight discrepancies in construction, slight errors in rigging, and in the event you don't keep the ball in the middle, I suppose you could stall one wing before the other, albeit a rare occasion. =20I have Never felt one tip stall before the other...it always breaks, or actually just Mushes, straight ahead, however, I haven't tried it with the ball way off center - at altitude of course. The Pietenpol wing has a fairly sharp leading edge, which causes a sharper stall break, than say the ol' T-craft. Have you ever noticed how big the leading edge radius is on an aerobatic plane ? Those wings have a higher critical angle of attack (the angle at which the wing begins to stall), but=20pay for it with an increase in drag. They have excess power to overcome the drag penalty. Nothing is free !! The Pietenpol wing is All about Lift. It creates a Lot of lift at airspeeds that the T-craft wing isn't even considering flying yet. When I was flying in the Test Phase of my plane, I re-rigged my wing several times, because I had a slightly Left Wing Heavy condition. I use the plans built 'Lollipop' fittings at the upper lift strut fittings, so when I re-rigged it was more of an adjustment in Symmetry, as opposed to changing the length of the lift struts. I came to find that the front strap across the bottom of the fuselage was the primary cause of the left wing heavy condition. I nitially I didn't have any bolts through that strap, into the ash cross member. Early on, that strap began to have a gap between it, and the bottom of the fuselage. I thought it was because of the dimension change in the wood with the season, and couldn't imagine that slight dimension change could cause some washout, and a wing heavy condition. Came to find the cause was hard landings. I installed a #10 bolt down through the center of the ash cross piece and strap... Presto !! Most all of the left wing heavy condition disappeared. =20Then the darn thing began to show a gap again, between the center, and the left side. I now have three bolts down through the ash cross piece / cross strap, spaced evenly. Hard landings in a Pietenpol are because as you roundout for landing and increase the angle of attack, the drag increases dramatically and rapidly decreases the airspeed...as opposed to a sharp stall break. The sharp stall break just isn't there in the Pietenpol wing. To conclude, I have about 1/16" to 1/8" washout in my wingtips, which probably is about 1=BA or so. The wing is rigged straight (no dihedral), and just slightly err towards washout. Now, instead of testing the 'Runway Hardness', I try to land as softly as a butterfly with sore feet !! Chuck G. NX770CG p.s. them ol' boys from Texas A&M probably got hold of some Federal money to go play around in the sky with the Taylorcraft, learned a Lot, shared their findings with us, and I'm sure they had a Lot of Fun !! ________________________________ Message 2 _____________________________________ Time: 09:19:06 AM PST US From: "Dick Navratil" Subject: Re: Pietenpol-List: Rudder bar or rudder pedals On the rudder horn, the GN-1 mounts the horn in a totally different location. Structurally it shouldn't be a problem although you may want to look at the location of the hinge and keep one hinge close to the horn. On the question of the rudder bar, I currently have a rudder bar, which I really don't care for that much. On my new project I'm putting in J-3 pedals. I dont have any specific complaints about the bar but with the pedals, I will be able to adjust them better for distance. It's a matter of choice. Dick N. ----- Original Message ----- From: John and Phyllis Smoyer To: pietenpol-list@matronics.com Sent: Saturday, February 18, 2006 11:50 AM Subject: Pietenpol-List: Rudder bar or rudder pedals Pieters: from a pilot's point of view, which is preferred? If rudder pedals are used, how big should the pedals be, and where should they be located? Thanks. John Smoyer ________________________________ Message 3 _____________________________________ Time: 04:36:56 PM PST US From: Rcaprd@aol.com Subject: Re: Pietenpol-List: Rudder horn location In a message dated 2/18/2006 12:11:26 PM Central Standard Time, jpsmoyer@verizon.net writes: Have any of you ever experimented with the vertical position of the rudder horn? I've located it about where the plans indicate, although that location is not dimensioned. What would happen if the horn were at a lower location? Reason I ask is that it seems like this would make for an easier (straighter) cable run from the rudder bar, maybe even avoid the need for a pulley or hard wood block to guide the control cable back to the horn. Thanks and best regards, John Smoyer John, If you locate the rudder horn down low, you will increase the torsional load on the upper portion of the rudder, which could lead to Flutter. No worries about the cable run with hardwood fairleads. Definitely not pulleys. AC43.13 says you can deflect a cable up to 7=BA without a pulley. It's much more than that, where the control stick to bellcrank pass under the seat, and because=20of the design load of the cables, there's not even a need for pulleys in that location, either. Just don't use stainless cables where a change in direction is needed. As far as rudder pedals go, they add a Lot of additional pieces that Must be there, or you will over stress the rudder horn. Just remember - 'If it isn't there, it can't break', and the Pietenpol motto : Keep it Simple !! Chuck G. NX770CG