Original Posted By: Rcaprd(at)aol.com
Oh soooo brave, to do spins in a Piete, it'd scare me to death.On secondary subject of long fuselages and CG's. I just completed the CGstuff on the rebuild of Piete N-1033B. This plane was built by Dick Greideback in 1979 and crashed in a MO cornfield in 1996 on the way back fromOshkosh, due to engine failure. Because the wings were off of an Aeronca1300 payload, and Greide moved the wings back, longer 4130 fuselage, Idecided to utilize the full advantage of this planes payload abilities byputting on an o-235 100 hp and shifting the CG as needed to fly my 280 lbs,plus wife's 130 lbs. Had to move the pilot's rudder petals forward about 4"due to 6'4" and long legs. It's a cozy fit by all measurement standards.Here's how the numbers came out: LE of wing used as datum point.1) gear axles 2"2) empty CG 5.5" with wt of 680#3) fuel at negative 12"4) tail wheel at 161" (had wt of 14 lbs when longerons level, min fuel,with full tank the bird will fall on nose without lead on tailwheel)5) Passenger's front seat moment was 20"6) Pilot's back seat moment was 53"Using 20% of chord as forward CG min. limit or 12" back from datum, and 33%of chord as aft loaded max. CG limit or 20". Trial (paper) loaded weightand balance came out as follows: 1) 170# passenger, 300# pilot, 120 #fuel. The initial takeoff CG was 17" behind LE, after burning off all butabout 2 gal of fuel, CG moved back to 19". Both in the operational window,but wouldn't want to do a couple spins, pilot may wantta lose a couple BigMacs too..Minimum pilot weight without supplimental weights in tail or baggage rackis about 150# with full fuel. This depends on the elevator's authority tohold the nose up during flareMax pilot weight with min. 2 fuel is about 305#. Moral of story, it ispossible to build a fat boy's Piete, hope this info is helpful for theother couple non-FAA standard 170#'ers out there. Hope to be airborne nextweek or two.Gordon Bowen________________________________________________________________________________
Re: Pietenpol-List: Piets and spins, CG Stuff
Re: Pietenpol-List: Piets and spins, CG Stuff
Original Posted By: Rcaprd(at)aol.com
Subject: Re: Pietenpol-List: Piets and spins, CG StuffIn a message dated 3/6/2005 9:49:43 AM Central Standard Time, gbowen(at)ptialaska.net writes:Using 20% of chord as forward CG min. limit or 12" back from datum, and 33%of chord as aft loaded max. CG limit or 20". Gordon,If I read you e-mail correctly, you have wings off of an Aronca on your Pietenpol. If this is true, then you CAN NOT use the 33% of chord as the aft loaded max. The 33% aft limit (or as BHP listed it as 1/3 of the wing chord),is for the Pietenpol Airfoil...not the Aronca Airfoil. You MUST use the CG rangeof the Aronca Airfoil, which probably has an aft limit of no more than 30%. Loading in an aft CG range is where you will be in serious trouble if you entera spin. On several occasions I've seen Radio Controlled Model Planes spin all the way to the ground, because they were intentionally loaded with an aft CG, in an effort to attain a sensitive pitch control.Chuck Gantzerp.s. Arm X Weight = Moment________________________________________________________________________________
Subject: Re: Pietenpol-List: Piets and spins, CG StuffIn a message dated 3/6/2005 9:49:43 AM Central Standard Time, gbowen(at)ptialaska.net writes:Using 20% of chord as forward CG min. limit or 12" back from datum, and 33%of chord as aft loaded max. CG limit or 20". Gordon,If I read you e-mail correctly, you have wings off of an Aronca on your Pietenpol. If this is true, then you CAN NOT use the 33% of chord as the aft loaded max. The 33% aft limit (or as BHP listed it as 1/3 of the wing chord),is for the Pietenpol Airfoil...not the Aronca Airfoil. You MUST use the CG rangeof the Aronca Airfoil, which probably has an aft limit of no more than 30%. Loading in an aft CG range is where you will be in serious trouble if you entera spin. On several occasions I've seen Radio Controlled Model Planes spin all the way to the ground, because they were intentionally loaded with an aft CG, in an effort to attain a sensitive pitch control.Chuck Gantzerp.s. Arm X Weight = Moment________________________________________________________________________________
Re: Pietenpol-List: Piets and spins, CG Stuff
Original Posted By: FTLovley(at)aol.com
Chuck,I hope to never even approach within 2" of the aft limit on these wings,for safety reason. But, the Aeronca has a straight constant chord of 60"like most of the storebought tail draggers, and a lot of tricycle gearedplanes. The limits of 33% of chord aft CG and 20% of chord forward CGlimit has nothing to do with Pietes or Aeroncas, these are standardpercentages used since the first Piper's and T-Crafts, due to the standardshape of the wing. Look at any oldtime builders book, use to be availablefrom EAA bookstore, on how to build wooden homebuilt plane, these old booksalways used the 33% and 20% rule of thumb numbers due to the shape andchord of the wings they were building. Some designers recommended 32%,like the Osprey, others like Rutan had other numbers due to the sweep ofwing and the constantly changing chord. For safety reasons, eachhomebuilder (aka Test Pilot), has to understand CG limits and how to safelyexperiment with their homebuilt wings and, if feasible, expand the safe CGenvelope.The purpose of my prior email was to let a few of the other Big Macchallenged potential builders/lurkers know, it's possible to build aquasi-plans Piete that will safely handle their weights, if adequateattention is paid to placement of stuff that affect CG. Plus moving thewings LE back to approx. 18" behind the firewall.Gordon BowenP.S. I stand corrected, I provided the approx. ARMS of the moveable stuff,not moment. Also N-1033B has a GM starter motor hanging out there by theprop and a 20lb battery between the passengers legs. ________________________________________________________________________________
Chuck,I hope to never even approach within 2" of the aft limit on these wings,for safety reason. But, the Aeronca has a straight constant chord of 60"like most of the storebought tail draggers, and a lot of tricycle gearedplanes. The limits of 33% of chord aft CG and 20% of chord forward CGlimit has nothing to do with Pietes or Aeroncas, these are standardpercentages used since the first Piper's and T-Crafts, due to the standardshape of the wing. Look at any oldtime builders book, use to be availablefrom EAA bookstore, on how to build wooden homebuilt plane, these old booksalways used the 33% and 20% rule of thumb numbers due to the shape andchord of the wings they were building. Some designers recommended 32%,like the Osprey, others like Rutan had other numbers due to the sweep ofwing and the constantly changing chord. For safety reasons, eachhomebuilder (aka Test Pilot), has to understand CG limits and how to safelyexperiment with their homebuilt wings and, if feasible, expand the safe CGenvelope.The purpose of my prior email was to let a few of the other Big Macchallenged potential builders/lurkers know, it's possible to build aquasi-plans Piete that will safely handle their weights, if adequateattention is paid to placement of stuff that affect CG. Plus moving thewings LE back to approx. 18" behind the firewall.Gordon BowenP.S. I stand corrected, I provided the approx. ARMS of the moveable stuff,not moment. Also N-1033B has a GM starter motor hanging out there by theprop and a 20lb battery between the passengers legs. ________________________________________________________________________________
Re: Pietenpol-List: Piets and spins, CG Stuff
Original Posted By: Rcaprd(at)aol.com
Subject: Re: Pietenpol-List: Piets and spins, CG StuffActually, if all of us self styled engineers want to get it right...as Bernard said, we are moving the fuselage forward, not the wing back...the wingstays right where it is.Forrest Lovley________________________________________________________________________________
Subject: Re: Pietenpol-List: Piets and spins, CG StuffActually, if all of us self styled engineers want to get it right...as Bernard said, we are moving the fuselage forward, not the wing back...the wingstays right where it is.Forrest Lovley________________________________________________________________________________
Re: Pietenpol-List: Piets and spins, CG Stuff
Original Posted By: Larry Nelson
Subject: Re: Pietenpol-List: Piets and spins, CG StuffIn a message dated 3/6/2005 4:55:39 PM Central Standard Time, gbowen(at)ptialaska.net writes:Chuck,I hope to never even approach within 2" of the aft limit on these wings,for safety reason. But, the Aeronca has a straight constant chord of 60"like most of the storebought tail draggers, and a lot of tricycle gearedplanes. The limits of 33% of chord aft CG and 20% of chord forward CGlimit has nothing to do with Pietes or Aeroncas, these are standardpercentages used since the first Piper's and T-Crafts, due to the standardshape of the wing. Look at any oldtime builders book, use to be availablefrom EAA bookstore, on how to build wooden homebuilt plane, these old booksalways used the 33% and 20% rule of thumb numbers due to the shape andchord of the wings they were building. Some designers recommended 32%,like the Osprey, others like Rutan had other numbers due to the sweep ofwing and the constantly changing chord. For safety reasons, eachhomebuilder (aka Test Pilot), has to understand CG limits and how to safelyexperiment with their homebuilt wings and, if feasible, expand the safe CGenvelope.Gordon,I wasn't aware of those other airfoils with 33% aft CG limits. I thought the Pietenpol's undercambered airfoil could get away with it, because of such a high negative pitching moment. A flat bottom airfoil does not have as much negative pitching moment (nose down) as an undercambered airfoil.Chuck G.p.s. the Wittman Tailwind has somewhat of a semi-semetrical airfoil, and has an aft CG limit of 28%.________________________________________________________________________________Date: Sun, 6 Mar 2005 17:58:26 -0800 (PST)
Subject: Re: Pietenpol-List: Piets and spins, CG StuffIn a message dated 3/6/2005 4:55:39 PM Central Standard Time, gbowen(at)ptialaska.net writes:Chuck,I hope to never even approach within 2" of the aft limit on these wings,for safety reason. But, the Aeronca has a straight constant chord of 60"like most of the storebought tail draggers, and a lot of tricycle gearedplanes. The limits of 33% of chord aft CG and 20% of chord forward CGlimit has nothing to do with Pietes or Aeroncas, these are standardpercentages used since the first Piper's and T-Crafts, due to the standardshape of the wing. Look at any oldtime builders book, use to be availablefrom EAA bookstore, on how to build wooden homebuilt plane, these old booksalways used the 33% and 20% rule of thumb numbers due to the shape andchord of the wings they were building. Some designers recommended 32%,like the Osprey, others like Rutan had other numbers due to the sweep ofwing and the constantly changing chord. For safety reasons, eachhomebuilder (aka Test Pilot), has to understand CG limits and how to safelyexperiment with their homebuilt wings and, if feasible, expand the safe CGenvelope.Gordon,I wasn't aware of those other airfoils with 33% aft CG limits. I thought the Pietenpol's undercambered airfoil could get away with it, because of such a high negative pitching moment. A flat bottom airfoil does not have as much negative pitching moment (nose down) as an undercambered airfoil.Chuck G.p.s. the Wittman Tailwind has somewhat of a semi-semetrical airfoil, and has an aft CG limit of 28%.________________________________________________________________________________Date: Sun, 6 Mar 2005 17:58:26 -0800 (PST)
Re: Pietenpol-List: Piets and spins, CG Stuff
Original Posted By: "gbowen(at)ptialaska.net"
Aaahhh!!!!!!!!! The 30's, Golden Age of Aviation and those with memoriesthereof, when fuselages were swept forward rather than wings swept backward.Forrest, didn't you make a posting a while back that you saw Bernie cut thetop out of a dope can for making metal tabs? If so, maybe you can answer aquestion about his history and plans for wings. Question: The NationalAdvisory Commission for Aeronautics (NACA) issued it's Tech Rept. #460 in1933, advising future aviators and builders of planes on the pros and consof 78 different airfoils. NACA had been around since 1915. Did Bernie'swing design come from this original NACA windtunnel work? Thanks.Gordon Bowen________________________________________________________________________________
Aaahhh!!!!!!!!! The 30's, Golden Age of Aviation and those with memoriesthereof, when fuselages were swept forward rather than wings swept backward.Forrest, didn't you make a posting a while back that you saw Bernie cut thetop out of a dope can for making metal tabs? If so, maybe you can answer aquestion about his history and plans for wings. Question: The NationalAdvisory Commission for Aeronautics (NACA) issued it's Tech Rept. #460 in1933, advising future aviators and builders of planes on the pros and consof 78 different airfoils. NACA had been around since 1915. Did Bernie'swing design come from this original NACA windtunnel work? Thanks.Gordon Bowen________________________________________________________________________________
Re: Pietenpol-List: Piets and spins, CG Stuff
Original Posted By: TBYH(at)aol.com
Chuck,I believe test pilots/Designers like Steve Wittman set CG design limitsafter a tad of flying trial and error and he assummed the future buyers ofhis plans actually built the plan to plans, which many did not. The testpilot who flew Nat Puffer's Cozy (one of the first serious modification ofRutan's proven designs), used a 20# chunk of lead within a slotted plasticpipe in the passenger seat. Nat may have learned this trick from MikeMelvil, Rutan's longterm crash test dummy and space cadet. The test pilotcould slide the chunk of lead backward and forward, inside the plasticpipe, as needed to recover from tail heavy stalls. By default each Pietenpol builder is a test pilot, and has to set designlimits for his or her unique aircraft. I saw one the other day on E-Baythat used a T-Craft wing. The % of chord CG limit rule of thumbs comes from the original testing doneby NACA in the 1930's, with windtunneling of 78 different wing shapes,aspects, chord and camber designs. I think just about every modern daystraight wing, constant chord wing is referred to as a NACA wing. Thefunny thing is, NACA didn't issue it's report #460 until 1933, a year afterBernie introduced his wing design.Gordon Bowen________________________________________________________________________________
Chuck,I believe test pilots/Designers like Steve Wittman set CG design limitsafter a tad of flying trial and error and he assummed the future buyers ofhis plans actually built the plan to plans, which many did not. The testpilot who flew Nat Puffer's Cozy (one of the first serious modification ofRutan's proven designs), used a 20# chunk of lead within a slotted plasticpipe in the passenger seat. Nat may have learned this trick from MikeMelvil, Rutan's longterm crash test dummy and space cadet. The test pilotcould slide the chunk of lead backward and forward, inside the plasticpipe, as needed to recover from tail heavy stalls. By default each Pietenpol builder is a test pilot, and has to set designlimits for his or her unique aircraft. I saw one the other day on E-Baythat used a T-Craft wing. The % of chord CG limit rule of thumbs comes from the original testing doneby NACA in the 1930's, with windtunneling of 78 different wing shapes,aspects, chord and camber designs. I think just about every modern daystraight wing, constant chord wing is referred to as a NACA wing. Thefunny thing is, NACA didn't issue it's report #460 until 1933, a year afterBernie introduced his wing design.Gordon Bowen________________________________________________________________________________
Re: Pietenpol-List: Piets and spins, CG Stuff
Original Posted By: N321TX(at)wmconnect.com
Subject: Re: Pietenpol-List: Piets and spins, CG StuffMr Bowen...In my posting I stated that Bernard, (I absolutely NEVER said Bernie.!!) used the tops of dope cans to make aileron and elevator horns, not "tabs". The information on how he developed his airfoil from a Gottengen 397 iswritten in his "How to Build" series in Popular Aviation during the thirties. He knew that a commercially produced airplane that he had previously owned withan undercambered airfoil got off the ground good, so he merely went ahead and built a wing that way to try it out. I have no idea on whether he ever saw the NACA Tech report #460. I also never stated that we were "sweeping" the fuselage forward or back...I merely pointed out that when a Pietenpol is adjustedto get the CG in the proper place, we are moving the weight of the fuselage forward, not moving the wing back, to compensate for a lighter engine than theFord Model A. Quite possibly, it's time for me to quit reading the postings on this list, and get back to building...I think my old friend Bernard would like the idea.Forrest Lovley________________________________________________________________________________
Subject: Re: Pietenpol-List: Piets and spins, CG StuffMr Bowen...In my posting I stated that Bernard, (I absolutely NEVER said Bernie.!!) used the tops of dope cans to make aileron and elevator horns, not "tabs". The information on how he developed his airfoil from a Gottengen 397 iswritten in his "How to Build" series in Popular Aviation during the thirties. He knew that a commercially produced airplane that he had previously owned withan undercambered airfoil got off the ground good, so he merely went ahead and built a wing that way to try it out. I have no idea on whether he ever saw the NACA Tech report #460. I also never stated that we were "sweeping" the fuselage forward or back...I merely pointed out that when a Pietenpol is adjustedto get the CG in the proper place, we are moving the weight of the fuselage forward, not moving the wing back, to compensate for a lighter engine than theFord Model A. Quite possibly, it's time for me to quit reading the postings on this list, and get back to building...I think my old friend Bernard would like the idea.Forrest Lovley________________________________________________________________________________
Re: Pietenpol-List: Piets and spins, CG Stuff
Original Posted By: "John and Phyllis Smoyer"