Pietenpol-List Digest Archive

Thu 05/26/05


Total Messages Posted: 10



Today's Message Index:
----------------------
 
     1. 01:02 AM - horsepower (Clif Dawson)
     2. 05:30 AM - Re: Pitch Trimming (FTLovley@AOL.COM)
     3. 05:43 AM - flying at 19 or 20" of aft CG (Michael D Cuy)
     4. 05:51 AM - Re: flying at 19 or 20" of aft CG (Phillips, Jack)
     5. 09:01 AM - Re: flying at 19 or 20" of aft CG (Gordon Bowen)
     6. 09:39 AM - Re: flying at 19 or 20" of aft CG (Phillips, Jack)
     7. 10:48 AM - spar testing (Oscar Zuniga)
     8. 01:54 PM - Re: Pitch Trimming (GCARDINAL@mn.rr.com)
     9. 03:43 PM - Re: Pitch Trimming (Ed G.)
    10. 11:30 PM - Re: Pitch Trimming (Rcaprd@aol.com)
 
 
 


Message 1


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    Time: 01:02:10 AM PST US
    From: Clif Dawson <CDAWSON5854@shaw.ca>
    Subject: horsepower
    Play with this for a while boys; http://www.tc.gc.ca/CivilAviation/Regserv/Affairs/cars/Part5/Standards/549/sub-b.htm#549.109 Also in combo with 111 right below it. The Vimy is now in Toronto! Now that's one huge Pietenpol! Clif, controls almost done; http://clifdawson.ca/Pietenpol4.html There is nothing, absolutely nothing, half as much worth doing as simply messing about in airplanes! ( Wind In The Willows )


    Message 2


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    Time: 05:30:37 AM PST US
    From: FTLovley@AOL.COM
    Subject: Re: Pitch Trimming
    --> Pietenpol-List message posted by: FTLovley@aol.com Chris...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


    Message 3


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    Time: 05:43:38 AM PST US
    From: Michael D Cuy <Michael.D.Cuy@grc.nasa.gov>
    Subject: flying at 19 or 20" of aft CG
    --> Pietenpol-List message posted by: Michael D Cuy <Michael.D.Cuy@grc.nasa.gov> Starts getting light in the nose at about 20" aft CG and I have to hold forward stick at 21". The stab should be in line with the top longerons. You should not have to mess with that. Something doesn't add up. Mike C.


    Message 4


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    Time: 05:51:36 AM PST US
    Subject: flying at 19 or 20" of aft CG
    From: "Phillips, Jack" <jphillip@alarismed.com>
    --> Pietenpol-List message posted by: "Phillips, Jack" <jphillip@alarismed.com> I agree with you, Mike. My Piet has the long fuselage, 65 Continental, wire wheels. At CG 20" aft of the LE, I have to hold a little forward stick, even with full nose down trim. I will shim the leading edge of the stabilizer up a little more when I finish the rebuild. Jack Phillips -----Original Message----- --> Pietenpol-List message posted by: Michael D Cuy <Michael.D.Cuy@grc.nasa.gov> Starts getting light in the nose at about 20" aft CG and I have to hold forward stick at 21". The stab should be in line with the top longerons. You should not have to mess with that. Something doesn't add up. Mike C.


    Message 5


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    Time: 09:01:55 AM PST US
    From: "Gordon Bowen" <gbowen@ptialaska.net>
    Subject: Re: flying at 19 or 20" of aft CG
    --> Pietenpol-List message posted by: "Gordon Bowen" <gbowen@ptialaska.net> 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 nose down/stick forward pressure at 20" aft loaded CG, but if normally operating in the back side of the CG envelope while still below gross limit, I think any builder should consider moving around some heavy stuff inside the plane to get their loaded CG forward to 15"-17" aft of LE wing.. It's common in a lot of other homebuilts to build a "pocket" somewhere forward or aft to hold extra bags of lead shot. The pilot determines when they need to add more 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 a lightweight pilot cannot get into a tail heavy (repeat repeat NON-RECOVERABLE) stall. Gordon Bowen -Homer Alaska Cozy IV N64CY Osprey II N64SY Pietenpol N-1033B " But such is the constitution of my mind I cannot avoid forming an opinion", John Adams ----- Original Message ----- From: "Phillips, Jack" <jphillip@alarismed.com> Subject: RE: Pietenpol-List: flying at 19 or 20" of aft CG > --> Pietenpol-List message posted by: "Phillips, Jack" <jphillip@alarismed.com> > > I agree with you, Mike. My Piet has the long fuselage, 65 Continental, > wire wheels. At CG 20" aft of the LE, I have to hold a little forward > stick, even with full nose down trim. I will shim the leading edge of > the stabilizer up a little more when I finish the rebuild. > > Jack Phillips > > -----Original Message----- > --> Pietenpol-List message posted by: Michael D Cuy > <Michael.D.Cuy@grc.nasa.gov> > > Starts getting light in the nose at about 20" aft CG and I have to > hold > forward > stick at 21". The stab should be in line with the top longerons. You > > should not > have to mess with that. Something doesn't add up. > > Mike C. > >


    Message 6


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    Time: 09:39:56 AM PST US
    Subject: flying at 19 or 20" of aft CG
    From: "Phillips, Jack" <jphillip@alarismed.com>
    --> Pietenpol-List message posted by: "Phillips, Jack" <jphillip@alarismed.com> I agree Gordon. However, extensive stalls (I have not spun it, yet) show the plane recovers quickly and easily. I have read that undercambered wings like the Pietenpol can be flown at further aft cg's than more "normal" airfoils. My centersection fuel tank does not change the CG much as fuel burns off, but what change there is tends to move the CG forward. I don't think a pilot that weighs more than my 200 lbs should fly it without adding ballast in the baggage compartment. After the rebuild the CG situation should be much improved. My new axle is 8 lbs heavier than the original, and I am using the BHP coil spring tailwheel design in place of the leafspring type I had before, which saves a whopping 1-1/2 lbs at the tail. Both should help shift the CG forward a bit. Jack Phillips NX899JP -----Original Message----- From: owner-pietenpol-list-server@matronics.com [mailto:owner-pietenpol-list-server@matronics.com] On Behalf Of Gordon Bowen Subject: Re: Pietenpol-List: flying at 19 or 20" of aft CG --> Pietenpol-List message posted by: "Gordon Bowen" <gbowen@ptialaska.net> 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 nose down/stick forward pressure at 20" aft loaded CG, but if normally operating in the back side of the CG envelope while still below gross limit, I think any builder should consider moving around some heavy stuff inside the plane to get their loaded CG forward to 15"-17" aft of LE wing.. It's common in a lot of other homebuilts to build a "pocket" somewhere forward or aft to hold extra bags of lead shot. The pilot determines when they need to add more 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 a lightweight pilot cannot get into a tail heavy (repeat repeat NON-RECOVERABLE) stall. Gordon Bowen -Homer Alaska Cozy IV N64CY Osprey II N64SY Pietenpol N-1033B " But such is the constitution of my mind I cannot avoid forming an opinion", John Adams ----- Original Message ----- From: "Phillips, Jack" <jphillip@alarismed.com> Subject: RE: Pietenpol-List: flying at 19 or 20" of aft CG > --> Pietenpol-List message posted by: "Phillips, Jack" <jphillip@alarismed.com> > > I agree with you, Mike. My Piet has the long fuselage, 65 Continental, > wire wheels. At CG 20" aft of the LE, I have to hold a little forward > stick, even with full nose down trim. I will shim the leading edge of > the stabilizer up a little more when I finish the rebuild. > > Jack Phillips > > -----Original Message----- > --> Pietenpol-List message posted by: Michael D Cuy > <Michael.D.Cuy@grc.nasa.gov> > > Starts getting light in the nose at about 20" aft CG and I have to > hold > forward > stick at 21". The stab should be in line with the top longerons. You > > should not > have to mess with that. Something doesn't add up. > > Mike C. > >


    Message 7


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    Time: 10:48:35 AM PST US
    From: "Oscar Zuniga" <taildrags@hotmail.com>
    Subject: spar testing
    --> Pietenpol-List message posted by: "Oscar Zuniga" <taildrags@hotmail.com> Dave asked- >How did you do your testing? There is another (simple) methodology on my website, at http://www.flysquirrel.net/wing/spartest.html Oscar Zuniga San Antonio, TX mailto: taildrags@hotmail.com website at http://www.flysquirrel.net


    Message 8


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    Time: 01:54:37 PM PST US
    From: GCARDINAL@mn.rr.com
    Subject: Re: Pitch Trimming
    --> Pietenpol-List message posted by: GCARDINAL@mn.rr.com 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@aol.com 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. > >


    Message 9


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    Time: 03:43:17 PM PST US
    From: "Ed G." <flyboy_120@hotmail.com>
    Subject: Re: Pitch Trimming
    --> Pietenpol-List message posted by: "Ed G." <flyboy_120@hotmail.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@mn.rr.com >Reply-To: pietenpol-list@matronics.com >To: pietenpol-list@matronics.com >Subject: Re: Pietenpol-List: Pitch Trimming >Date: Thu, 26 May 2005 15:54:40 -0500 > >--> Pietenpol-List message posted by: GCARDINAL@mn.rr.com > >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@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. > > > > > >


    Message 10


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    Time: 11:30:44 PM PST US
    From: Rcaprd@aol.com
    Subject: Re: Pitch Trimming
    It seems to me you have some aerodynamic stuff going on here. I have to assume Greg & Dale built the fwd cabane struts 1" longer than the aft ones.=20 This sets the wing at approximately 3=BA positive incidence. That's according to plans...no matter if they are all lengthened a couple of inches. However, if there is a great deal of washout in both wings, this will cause a nose down tendency. Also, if the wing is not square with the fuse, it will cause a roll tendency, especially with too much washout...that's why I suggested re-checking symmetry and washout. Rig the wing by measuring from the exact=20same spot of each wing tip, to a point in the center of the fuselage (aft edge of turtle deck), just ahead of the leading edge of the horiz / vert stab. Make a dot with a sharpie pen, to measure to. In fact, I do it from two different points on the wing - one at the outboard trailing edge of the wing, ahead of the aileron, and another time at the inboard end of the aileron, trailing edge of the wing. Not the aileron, but the wing. Two people with a tape measure stretched tight, and it only takes a couple of minutes. Record your measurements on the sketch of a plan view of the plane. To check for washout, level the longerons for & aft and left & right, and use a 4 foot level (confirm the level reads the same both sides up) at a point on the bottom of the rib, just outboard of the cabane struts. Note the gap at the fwd end of the level. Measure again at the lift strut attachment, then again at the tip rib. Record all these measurements. 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 both sides. 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 strut bolts, cabane strut bolts, and jury strut bolts to change the symmetry. Then you 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 pendulum effect of parasitic drag, the negative pitching moment of an undercambered airfoil, 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 the turnbuckles, and go fly. You can even raise the trailing edge up about one=20or two 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 take advantage of the unique design feature of the Pietenpol, in that you can move your wing aft, to bring the CG forward to a safer range. It would likely require making some new cables, but re-terminate the long ones, to use them on the short side. Like others have said to guard against an aft CG...it just simply gives me the Hiebie Jiebies !! Adding ballast also gives me the Hiebie Jiebies - that's why I made the engine mount on my plane so long. My wing is 3 1/2" aft of vertical, and with my 210 - 215 lbs. of fat butt in there, the C.G. is just under 20" aft of Leading Edge of the wing, even with Zero fuel in both tanks. The Hard Line, No More Aft C.G. is 20" aft of Leading Edge - No Excuses !! Adding ballast in the front seat does very little to effect the CG. I doubt if 100 lbs would move it more than 1/8" forward. If you can't possibly move the wing aft, and you don't want to build a new engine mount, cowling,=20and everything else, here is one suggestion: Cast a couple of long Lead ingots (using shotgun shot) to fit the outer diameter of the lower tubes on the engine mount. Use thin rubber strips to=20isolate them from the steel tubes, and isolate some type of clamp, to keep from scratching the paint off the engine mount. This could possibly even reduce=20the vibration of the engine from being transmitted to the fuselage. Another option is using a metal prop. Greg - I'll get a couple of low resolution pictures of my trim tabs tomorrow, 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=20bunji chord method of pulling on the top elevator cable. And like I said, I was able to re-adjust the horizontal stabilizer back to neutral and flat. I couldn't shim the aft edge of the horizontal stab up, because my ship was complete and flying, and I already had the lower rudder hinge located. Chuck Gantzer NX770CG I spent 45 minutes playing in the pattern this evening, shooting landings. I used an abbreviated pattern, but still got up to over 600' agl=20on downwind, turn base early, pull power to 1500 and let the nose drop to maintain 65 mph. On base leg, I pull power almost all the way to idle and slip it down=20past the cones at the beginning of the runway to about 10', but I maintained above 65 mph the whole way down. Very steep decent. My landing gear Vee's are NOT covered. Easily comes out of the slip, align right up with the runway, and it bleeds of speed like she had a drag chute !! Before anyone ever tries this so close to the ground, you need a properly rigged ship, and become VERY familiar with your ship at 2500 or 3000 agl. I was also practicing a unique takeoff. Clear the runway, hold brakes tight, full power, smoke ON, lots of forward stick, lift the tail off the ground before beginning to roll, drag the brakes for the first 50 feet so the tail wouldn't come back down, then let 'er go !! Ya can't practice this one from 2500' agl :) Two hot air balloons took off about 100 feet from my hanger. What an Excellent evening !!




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