Pietenpol-List: Pitch Trimming

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Original Posted By: "Ed G."
Subject: Re: Pietenpol-List: Pitch Trimming> Adjusting the leading edge of the horiz stab down, does > indeed help the > nose down pitch tendency. I adjusted mine down on three different > occasions, > lengthening the top turnbuckles by 2 turns, and tightening the > bottom ones by > 2 turns. Each time it helped, but didn't cure it. Standing in > front of the > plane, you could see the leading edge of the stab, how it curved > down on each > side. I finally added a fixed trim tab on the elevators > (flippers). I made > it from balsa wood, blending the trailing edge of the flippers > into the trim > tabs. Each is about 5" long, and have a chord of about 2" and > angled down about > 10. Initially, I tested the positon of the trim tab holding it > on with duct > tape. When I was satisfied with the placement, I used fabric & > paint for the > final install. With these trim tabs, I was able to remove all the > leading > edge down adjustments of the horiz stab, and now the stab is > straight. I could > take some pictures of it if you're interested.> I believe some of the pitch down tendency when you pull power, > can be > attributed to the drag of the landing gear. Does it climb with > full power, and > no back pressure on the stick ? I would also suggest you check > the symatry > again, as well as wing washout - doesn't take much time.> >________________________________________________________________________________

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Original Posted By: TRichmo9(at)aol.com
NX18235 is displaying a significant nose-down pitching tendency. Approximately6 pounds of aft stick force is required to maintain level flight.Has anyone corrected a pitching tendency by simply adjusting the forward stabilizerbracing cables?Shimming the stabilizer at this point in the game would require a significant amountof work.Greg Cardinal________________________________________________________________________________

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Original Posted By: Gene Hubbard
Subject: Re: Pietenpol-List: Pitch TrimmingIn a message dated 5/25/05 9:43:19 P.M. Central Daylight Time, gcardinal(at)mn.rr.com writes:NX18235 is displaying a significant nose-down pitching tendency. Approximately 6 pounds of aft stick force is required to maintain level flight.Has anyone corrected a pitching tendency by simply adjusting the forward stabilizer bracing cables?Shimming the stabilizer at this point in the game would require a significant amount of work.Greg Cardinalgreg i think the work on your plane is awsome the seats are a work of art and the wood work is top notch . tom________________________________________________________________________________Date: Wed, 25 May 2005 21:47:43 -0700

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Original Posted By: "Christian Bobka"
Subject: Re: Pietenpol-List: Pitch TrimmingIn a message dated 5/25/2005 9:43:19 PM Central Standard Time,gcardinal(at)mn.rr.com writes:NX18235 is displaying a significant nose-down pitching tendency.Approximately 6 pounds of aft stick force is required to maintain level flight.Has anyone corrected a pitching tendency by simply adjusting the forwardstabilizer bracing cables?Shimming the stabilizer at this point in the game would require a significantamount of work.Greg CardinalGreg,A big Congratulations to you and Dale for the completion of your plane !!And Chris B. for doing the first flights, with a very informative report ofthe first flights. Adjusting the leading edge of the horiz stab down, does indeed help thenose down pitch tendency. I adjusted mine down on three different occasions,lengthening the top turnbuckles by 2 turns, and tightening the bottom ones by2 turns. Each time it helped, but didn't cure it. Standing in front of theplane, you could see the leading edge of the stab, how it curved down on eachside. I finally added a fixed trim tab on the elevators (flippers). I madeit from balsa wood, blending the trailing edge of the flippers into the trimtabs. Each is about 5" long, and have a chord of about 2" and angled down about10=BA. Initially, I tested the positon of the trim tab holding it on with ducttape. When I was satisfied with the placement, I used fabric & paint for thefinal install. With these trim tabs, I was able to remove all the leadingedge down adjustments of the horiz stab, and now the stab is straight. I couldtake some pictures of it if you're interested. I believe some of the pitch down tendency when you pull power, can beattributed to the drag of the landing gear. Does it climb with full power,=20andno back pressure on the stick ? I would also suggest you check the symatryagain, as well as wing washout - doesn't take much time.Chuck GantzerWichita KSNX770CGShort Fuselage, Continental A65, engine mount with 1/8" right thrust andplans amount of down thrust - built 8" longer than plans (with heavier walltubing), no ballast, no vertical stab offset, 630 lbs. empty weight. I weigh210lbs________________________________________________________________________________

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Original Posted By: Rcaprd(at)aol.com
Chuck,It requires the same back pressure on the stick whether power at full or at idleand at all airspeeds (hi and low alpha), both with full or idle power. In otherwords, the pitchdown tendency is independent of the power and the angle ofattack of the wing.Greg and Dick Navratil had a conference call this evening and we determined thatwe are operation at very close to the same CG which is about 19-20" aft of theleading edge of the wing. What about with your ship?ChrisBraumeister und Inspektor der Flitzer und Flitzermotoren ----- Original Message -----

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Original Posted By: Clif Dawson

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Original Posted By: Michael D Cuy
Subject: Re: Pietenpol-List: Pitch TrimmingChris...be really carefull while flying a Continental powered Pietenpol with its extra forward side area while having a CG at 20 inches aft of the leading edge. It will probably fly just fine, but if you spin it , you will be in deep do-do. They are even worse if the landing gear V's are covered with fabric,increasing the forward area. Also, be careful slipping the airplane close to the ground, as they can sometimes take extra time to recover. I've been away from the Piets for a while, but my memory is still good, and I learned some of this stuff the hard way. I had 1000 hours in Pietenpols before I was old enough to vote, but that was back when I was bullet proof and invisible. Fly Safe...Forrest Lovley________________________________________________________________________________Date: Thu, 26 May 2005 08:43:15 -0400

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Original Posted By: "Phillips, Jack"

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Original Posted By: "Phillips, Jack"
Flying on the back edge of CG limit is an invitation to a tail heavy(non-recoverable) stall. Most everyone should have to hold a little nosedown/stick forward pressure at 20" aft loaded CG, but if normally operatingin the back side of the CG envelope while still below gross limit, I thinkany builder should consider moving around some heavy stuff inside the planeto get their loaded CG forward to 15"-17" aft of LE wing.. It's common ina lot of other homebuilts to build a "pocket" somewhere forward or aft tohold extra bags of lead shot. The pilot determines when they need to addmore shot when flying alone or with a non-standard load. All Longezes,Variezes and Cozys have a pocket in the nose to add lead shot so alightweight pilot cannot get into a tail heavy (repeat repeatNON-RECOVERABLE) stall.Gordon Bowen -Homer AlaskaCozy IV N64CYOsprey II N64SYPietenpol N-1033B" But such is the constitution of my mind I cannot avoid forming anopinion", John Adams----- Original Message -----

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Original Posted By: "Phillips, Jack"

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Original Posted By: Rcaprd(at)aol.com
Hi Everyone...If my waneing memory serves me right Corky posted that on his test flights that he had to twist the leading edge of his Stabilizer down three times until he cured his nose down tendency...Now Greg is haveing a similar problem and Chuck comes back and says that he had to add a trim tab for the same reason...I havent installed my lower rudder hinge yet so there is still time to ask a question that I really struggled with when building my Horiz. Stab....I built my stab. with the center line parralell to the upper longerons because that is what some trusted people on the list said it should be...Reading the plans carefully shows that the leading edge should be up more than 1/16" beacuse; The trailing edge member is 1" thick and the narrow section where the 3/16" plywood sits is 5/8" ( the plywood sits flush with the 1")...The center beam is 3/4" thick with 3/16" ply top and bottom; 3/4' + 3/16"+ 3/16" = 1 1/8" ....Divideing by two to get the center line = 9/16" at the center beam and 1/2' at the trailing edge. this would put the center beam's C/L 1/16" higher than the trailing edge and the leading edge slightly higher yet...Sooo...if you build to the plans the the stabilizer's C/L is NOT parallel to the upper longeron but raised at the front...So my question is; Did Corky, Chuck and Greg build theirs to the plans or did they build them parallel to the longerons?? This will help those of us who are still building get a better idea of what the incidence should be...If theirs were parallel maybe we should build in adjustments to drop ours even more if needed and if they built theirs to the plans we might be okay.... thanks in advance...Ed Grentzer assembleing my engine and fuel system>From: GCARDINAL(at)mn.rr.com>Reply-To: pietenpol-list(at)matronics.com>To: pietenpol-list(at)matronics.com>Subject: Re: Pietenpol-List: Pitch Trimming>Date: Thu, 26 May 2005 15:54:40 -0500>>>Chuck,>Changing power does not affect the nose down tendency. It is something>aerodynamic.>Please send picture of your trim tab.>>Thanks, Greg>>----- Original Message ----->From: Rcaprd(at)aol.com>Date: Wednesday, May 25, 2005 11:57 pm>Subject: Re: Pietenpol-List: Pitch Trimming> > Adjusting the leading edge of the horiz stab down, does> > indeed help the> > nose down pitch tendency. I adjusted mine down on three different> > occasions,> > lengthening the top turnbuckles by 2 turns, and tightening the> > bottom ones by> > 2 turns. Each time it helped, but didn't cure it. Standing in> > front of the> > plane, you could see the leading edge of the stab, how it curved> > down on each> > side. I finally added a fixed trim tab on the elevators> > (flippers). I made> > it from balsa wood, blending the trailing edge of the flippers> > into the trim> > tabs. Each is about 5" long, and have a chord of about 2" and> > angled down about> > 10. Initially, I tested the positon of the trim tab holding it> > on with duct> > tape. When I was satisfied with the placement, I used fabric &> > paint for the> > final install. With these trim tabs, I was able to remove all the> > leading> > edge down adjustments of the horiz stab, and now the stab is> > straight. I could> > take some pictures of it if you're interested.> > I believe some of the pitch down tendency when you pull power,> > can be> > attributed to the drag of the landing gear. Does it climb with> > full power, and> > no back pressure on the stick ? I would also suggest you check> > the symatry> > again, as well as wing washout - doesn't take much time.> >> >>>________________________________________________________________________________

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Original Posted By: Rick Holland
Subject: Re: Pietenpol-List: Pitch Trimming It seems to me you have some aerodynamic stuff going on here. I have toassume Greg & Dale built the fwd cabane struts 1" longer than the aft ones.=20This sets the wing at approximately 3=BA positive incidence. That's accordingtoplans...no matter if they are all lengthened a couple of inches. However, ifthere is a great deal of washout in both wings, this will cause a nose downtendency. Also, if the wing is not square with the fuse, it will cause a rolltendency, especially with too much washout...that's why I suggestedre-checking symmetry and washout. Rig the wing by measuring from the exact=20samespot ofeach wing tip, to a point in the center of the fuselage (aft edge of turtledeck), just ahead of the leading edge of the horiz / vert stab. Make a dotwith a sharpie pen, to measure to. In fact, I do it from two different pointsonthe wing - one at the outboard trailing edge of the wing, ahead of theaileron, and another time at the inboard end of the aileron, trailing edge of thewing. Not the aileron, but the wing. Two people with a tape measure stretchedtight, and it only takes a couple of minutes. Record your measurements on thesketch of a plan view of the plane. To check for washout, level thelongerons for & aft and left & right, and use a 4 foot level (confirm the levelreadsthe same both sides up) at a point on the bottom of the rib, just outboard ofthe cabane struts. Note the gap at the fwd end of the level. Measure againat the lift strut attachment, then again at the tip rib. Record all thesemeasurements. Very little washout is all you need - maybe 1/8" at the very=20most.Just so you err on the side of washout, and it's the same amount on bothsides. Sit down and study the measurements. If you have to change the symmetry,it will change the washout also. You will have to loosen all the lift strutbolts, cabane strut bolts, and jury strut bolts to change the symmetry. Thenyou have to re-check and re-adjust the washout. Record every measurement, date& time, you take. I think your gremlins are in the rigging. Check it all,and chase 'em out !! The other things that inherently cause nose down pitch is the pendulumeffect of parasitic drag, the negative pitching moment of an undercamberedairfoil, and the actual mass of the flippers being behind the hinge line. Adjusting the leading edge of the stab down maybe 2 or 3 turns on theturnbuckles, and go fly. You can even raise the trailing edge up about one=20ortwo turns on the turnbuckles. This is an effective method to trim the nose=20up,but you need to use small increments between flights. How far back is the wing from vertical ? I think you should takeadvantage of the unique design feature of the Pietenpol, in that you can move yourwing aft, to bring the CG forward to a safer range. It would likely requiremaking some new cables, but re-terminate the long ones, to use them on the shortside. Like others have said to guard against an aft CG...it just simplygives me the Hiebie Jiebies !! Adding ballast also gives me the Hiebie Jiebies - that's why I made theengine mount on my plane so long. My wing is 3 1/2" aft of vertical, and withmy 210 - 215 lbs. of fat butt in there, the C.G. is just under 20" aft ofLeading Edge of the wing, even with Zero fuel in both tanks. The Hard Line, NoMore Aft C.G. is 20" aft of Leading Edge - No Excuses !! Adding ballast in the front seat does very little to effect the CG. Idoubt if 100 lbs would move it more than 1/8" forward. If you can't possiblymove the wing aft, and you don't want to build a new engine mount, cowling,=20andeverything else, here is one suggestion:Cast a couple of long Lead ingots (using shotgun shot) to fit the outerdiameter of the lower tubes on the engine mount. Use thin rubber strips to=20isolatethem from the steel tubes, and isolate some type of clamp, to keep fromscratching the paint off the engine mount. This could possibly even reduce=20thevibration of the engine from being transmitted to the fuselage. Another optionis using a metal prop. Greg - I'll get a couple of low resolution pictures of my trim tabstomorrow, and post them to the group. I'm very satisfied with these trim tabs,because they work well holding the nose up aerodynamically, as opposed to a=20bunjichord method of pulling on the top elevator cable. And like I said, I wasable to re-adjust the horizontal stabilizer back to neutral and flat. Icouldn't shim the aft edge of the horizontal stab up, because my ship was completeand flying, and I already had the lower rudder hinge located.Chuck GantzerNX770CG I spent 45 minutes playing in the pattern this evening, shootinglandings. I used an abbreviated pattern, but still got up to over 600' agl=20ondownwind, turn base early, pull power to 1500 and let the nose drop to maintain65mph. On base leg, I pull power almost all the way to idle and slip it down=20pastthe cones at the beginning of the runway to about 10', but I maintained above65 mph the whole way down. Very steep decent. My landing gear Vee's are NOTcovered. Easily comes out of the slip, align right up with the runway, andit bleeds of speed like she had a drag chute !! Before anyone ever tries thisso close to the ground, you need a properly rigged ship, and become VERYfamiliar with your ship at 2500 or 3000 agl. I was also practicing a unique takeoff. Clear the runway, hold brakestight, full power, smoke ON, lots of forward stick, lift the tail off the groundbefore beginning to roll, drag the brakes for the first 50 feet so the tailwouldn't come back down, then let 'er go !! Ya can't practice this one from2500' agl Two hot air balloons took off about 100 feet from my hanger. What an Excellent evening !!________________________________________________________________________________Date: Fri, 27 May 2005 06:48:20 -0700

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Original Posted By:
thanks forrest.ChrisBraumeister und Inspektor der Flitzer und Flitzermotoren----- Original Message -----