Brodhead Pietenpol Association

Original Posted By: bwm
Subject: Pietenpol-List: Re: Weight and BalanceHi Ian, sure, I really ought to have a set. How much, and where to send thecheck?Robert Hensarlinghttp://www.mesquite-furniture.comrhrocker(at)admin.hilconet.comUvalde, Texas>Robert, if you want a complete set of plans for a GN-1 for reference,>let me know. I bought them and never pursued it. Make me an offer.>-=Ian=->>________________________________________________________________________________

Original Posted By: robert hensarling
Subject: Pietenpol-List: Re: Weight and BalanceThanks Bert for the info. The log book indicates a weight of 706, and a CGof 14.5, and that the leading edge was used as the datum. I just wanted totry it myself to see if I could get close to the original calculations.Robert>robert hensarling wrote:>>>> Hi List!>>>> When I aquired my GN-1, it didn't include the GN-1 plans used in its>> construction. I'm interested in checking the CG, and am wondering if Ican>> use the formulas that were in the last newsletter (which I think were for>> the Pietenpol) for th GN-1, or is there another way to figure the GN-1CG.>> Mine has a 65 HP Cont, and the fuel tank in the forward cockpit.>>>> Thanks in advance!>> Robert Hensarling>> ASC BFI>> PPL GN-1 N83887>>>Robert,>>Tony Bingelis's book "The Sportplane Builder" has a good section on>weight and balance. You can get from EAA. You should be able to use it>with no problem.>>Basically, if all your trying to do is locate where the CG is, you>should be able to find it without much effort. There's an old>engineering trick called "summation of moments about a point" that will>tell you exactly where the CG is. No real voodoo there.>>Or, you should be able to do one similar to the one in the BPA>newsletter (third quarter 1998). Unfortunately, there was a mistake in>the data sheet printed that indicated a pilot weight of 115 lbs. That>should have read 155 lbs - I E-mailed Grant Mclaren with the correction>later but I am not sure if it was ever corrected. The CG on that one>(Poplar Pete) turned out to be right where it' supposed to be. I got a>hop in it the other day and it flies right in trim.>>Ask around the local airport or talk to a local engineer-type. There>should be someone that can help you. Good Luck.>>PS: I've got a GN-1 on the gear now and am putting together a site for>"Aircampers" both Piets and GN-1s. I just got it up and running in a>basic form today-its still under construction. You guys visit when you>can.... I'm no expert but if I can help with the weight and balance ->ring me up at...>>bwm(at)planttel.net>www.bwmproductions.com/GN1>>Cheers>Bert ... __________

Original Posted By: jmcnarry(at)techplus.com (John McNarry)
Hi List!When I aquired my GN-1, it didn't include the GN-1 plans used in itsconstruction. I'm interested in checking the CG, and am wondering if I canuse the formulas that were in the last newsletter (which I think were forthe Pietenpol) for th GN-1, or is there another way to figure the GN-1 CG.Mine has a 65 HP Cont, and the fuel tank in the forward cockpit.Thanks in advance!Robert HensarlingASC BFIPPL GN-1 N83887________________________________________________________________________________

Original Posted By: robert hensarling
robert hensarling wrote:> > Hi List!> > When I aquired my GN-1, it didn't include the GN-1 plans used in its> construction. I'm interested in checking the CG, and am wondering if I can> use the formulas that were in the last newsletter (which I think were for> the Pietenpol) for th GN-1, or is there another way to figure the GN-1 CG.> Mine has a 65 HP Cont, and the fuel tank in the forward cockpit.> > Thanks in advance!> Robert Hensarling> ASC BFI> PPL GN-1 N83887Robert, Tony Bingelis's book "The Sportplane Builder" has a good section onweight and balance. You can get from EAA. You should be able to use itwith no problem. Basically, if all your trying to do is locate where the CG is, youshould be able to find it without much effort. There's an oldengineering trick called "summation of moments about a point" that willtell you exactly where the CG is. No real voodoo there.Or, you should be able to do one similar to the one in the BPAnewsletter (third quarter 1998). Unfortunately, there was a mistake inthe data sheet printed that indicated a pilot weight of 115 lbs. Thatshould have read 155 lbs - I E-mailed Grant Mclaren with the correctionlater but I am not sure if it was ever corrected. The CG on that one(Poplar Pete) turned out to be right where it' supposed to be. I got ahop in it the other day and it flies right in trim.Ask around the local airport or talk to a local engineer-type. Thereshould be someone that can help you. Good Luck. PS: I've got a GN-1 on the gear now and am putting together a site for"Aircampers" both Piets and GN-1s. I just got it up and running in abasic form today-its still under construction. You guys visit when youcan.... I'm no expert but if I can help with the weight and balance -ring me up at... bwm(at)planttel.netwww.bwmproductions.com/GN1CheersBert________________________________________________________________________________

Original Posted By: Ian Holland
-----Original Message-----

Original Posted By: bwm
-----Original Message-----

Original Posted By: Ian Holland
The plans I have are incomplete for my GN-1, but they include the weightand balance information. The plans and a few other items are at a friendsright now, but should be home this week-end. If you still need the W/B whenI get them, you are welcome to it.Thanks, Larry > Hi List!> > When I aquired my GN-1, it didn't include the GN-1 plans used in its> construction. I'm interested in checking the CG, and am wondering if Ican> use the formulas that were in the last newsletter (which I think were for> the Pietenpol) for th GN-1, or is there another way to figure the GN-1 CG.> Mine has a 65 HP Cont, and the fuel tank in the forward cockpit.> > Thanks in advance!> Robert Hensarling> ASC BFI> PPL GN-1 N83887> > > ________________________________________________________________________________

Original Posted By: robert hensarling
Robert, if you want a complete set of plans for a GN-1 for reference,let me know. I bought them and never pursued it. Make me an offer.-=Ian=-________________________________________________________________________________

Original Posted By: oil can
Bert, I tossed you an e-mail re the extra fork ends that you had.I amnot sure if it went. I am interested if you can let me know what youwant for two sets.________________________________________________________________________________

Original Posted By: Ian Holland
Ian Holland wrote:> > Robert, if you want a complete set of plans for a GN-1 for reference,> let me know. I bought them and never pursued it. Make me an offer.> -=Ian=-I've got to ask but don't want to sound stupid. What is a GN-1? Isthere a web site for the GN-1? Does it compare to the Piet and if sohow? Thanks in advance and may you be blessed with a tailwind. RandyGaskins________________________________________________________________________________

Original Posted By: Michael D Cuy
Randy,Long time no hear! The GN-1 is a Piet look a like. It was based on thepiet, but modified to accept what was once redily available Cub parts, and acontinetal engine. It is generally 50-100lbs heavier than a stock piet, anduses a different airfoil. There are other differences, but they look verysimilar. I have heard they fly similarly as well, but I haven't had thechance to fly one yet.Steve EldredgeIT ServicesBrigham Young University> -----Original Message-----> RGASKIN> Sent: Wednesday, May 12, 1999 5:00 AM> To: Pietenpol Discussion> Subject: Re: Weight and Balance>>> Ian Holland wrote:> >> > Robert, if you want a complete set of plans for a GN-1 for> reference,> > let me know. I bought them and never pursued it. Make me an offer.> > -=Ian=-> I've got to ask but don't want to sound stupid. What is a GN-1? Is> there a web site for the GN-1? Does it compare to the Piet and if so> how? Thanks in advance and may you be blessed with a tailwind. Randy> Gaskins>________________________________________________________________________________

Original Posted By: Christian Bobka

Original Posted By: "Larry Nelson"
The simplest (and most accurate) is to level the plane with EMPTY tanks butready to fly (leave "unusable" fuel in the tank). Weigh it and determinethe CG location. Then put yourself in the cockpit (in what you would wearto fly, no cheating! Most of us seem to use our weight just before gettinginto the shower but not many of us fly "buck neked". If you do, and if youaren't a beautiful under 30 female, I don't want to know about it.) andweigh it and determine CG again. Next, put full fuel in and repeat theprocess. Don't forget to MEASURE THE GALLONS OF FUEL YOU ADD! Last, putyour backside in the cockpit with the full fuel and do it a fourth time.Most will think this is excessive but, you wouldn't believe how often thenumbers you measure WON'T match what you calculated they "should be". Yourseat probably isn't exactly where you think it is, your tank probablydoesn't hold exactly what you think it does, the tank probably isn't exactlywhere you think it is and none of our bodies CGs are where we usually thinkthey are.Once you have the location of the CG on the fuselage (for each condition)you need to measure where it falls ON THE WING CHORD. No matter what ANYONEELSE TELLS YOU, all that matters is where the CG is on the wing NOT THEDISTANCE FROM THE FIREWALL, THE PROP FLANGE OR ANY OTHER PLACE. THE WING!JUST THE WING! ONLY THE WING! There are some guys out there on some of thegroups that have stretched tails and noses and moved wings and think the CGshould still fall at the same fuselage station. I have 30 years as anaerospace engineer and you have GOT TO TRUST ME, those guys are going tokill someone. Keep the CG in the limits ON THE WING. You have to be in thelimits for all of the conditions you measured. If you aren't you need tomove something to make sure it is, even if it requires ballast. You haven'thad a thrill till you burn fuel from a nose tank that puts you in an aft CGcondition and fly into turbulence. Weight transfers from your body to theseat FAST but it doesn't move the CG to help you, it just ruins the seat.If you need help with the math or in set up methods for measuring, just ask,but this ISN'T a place to scrimp. An incorrect CG can and will kill you.Hank J----- Original Message -----

Original Posted By: Larry Nelson

Original Posted By: "Larry Nelson"
Here's 4 programs that I used. They are the 4 different scenes that youwill run into in a Piet. Worst is pilot only with low fuel, and best isfull gross with full nose fuel. Use the one you want. Just change thenumbers and the final CG changes before your eyes!!!walt evansNX140DL----- Original Message -----

Original Posted By: "hjarrett"
Your warning is correct. You need to locate the CG on the wing.However most use a convenient point on the plane as their reference ordatum. The distance that the leading edge is from that datum will be in thecomputed distance to the CG. The actual CG can be referenced by subtractingthat distance. Most designers specify a distance from a datum instead ofthe distance or percent of chord. Either method IF done correctly, willwork.For further details, check AC 43.13-1B There is a complete method set up bythe FAA for weight and Balance.Cy GalleyEAA Safety Programs EditorAlways looking for ideas and articles for EAA Sport Pilot----- Original Message -----

Original Posted By: "Larry Nelson"
Hank,Excellent detailed procedure. Couldn't agree more with the pros and cons ofusing anything but the LE of the wing for determining CG and limits. Addingand subtracting ARMs to do moments, isn't brain surgery. Some guys like allpositive arms, but all homebuilts are different. Second issue, the purposeof homebuilding is to LEARN. Learning about CG, MAC, materials limts inconstruction, contruction techniques is the reason for homebuilts. It isespecially a problem when an non-builder pilot becomes PIC test pilot of anewly bought toy someone else built from scratch.Now to the question of Larry. Wing Chord- and CG. Just about allstraight wing (verus swept backward like a canard pusher type), I've seenuse 20% of chord for loaded forward CG limit max. (this depends on theelevator authority available to keep the nose in the air at flare), 32% ofChord for loaded AFT CG limit. So when you run low on fuel, and you're 300lbs, have you slowly slid past the AFT CG limit on your wing as you burntoff fuel, therefore going into a tail heavy unrecoverable stall, or do youdo your homework about MAC and CG limits before you start your engine?Every homebuilder should build there own CG envelope based on Hank'sexcellent procedure outlined below. Do the flight test work on the plane,using a guideline of loaded configuration - forward CG max. 25%, Aft CG of28%, in test loaded configuration. Maintain this very narrow CG envelopetest area until you can safely expand the loaded configuration to the max of20% forward and max. 32% aft. and max takeoff weight configuration. Any ofyou aerospace wing design Engineers can jump on these % numbers with otherhard data or facts, I'm only a reporting these numbers from observations ofmany types of homebuilts with straight wings. Every homebuilt airplane is going to have a different looking CG envelope.Maybe sloped forward at max. fuel and max passenger wt, or maybe slopedbackward to account of fuel burn-off. This is something you learn abouthomebuilts just like the fuel plumbing or wiring.Every Pilot, by default is a TEST pilot on a homebuilt. You gotta learn oryou'll burn.Gordon BowenN-1033B----- Original Message -----

Original Posted By: Larry Nelson

Original Posted By: BARNSTMR(at)aol.com
Subject: Re: Pietenpol-List: Weight and BalanceIn a message dated 10/3/04 4:34:58 PM Central Daylight Time, lnelson208(at)yahoo.com writes:>Larry, CG has always been a popular topic of Pietenpol aircraft. Last year at Brodhead, Doc Moser pointed to the last two digits of my registration number and said "Chuck, that's the most aft CG I've ever seen !!" If your plane is in the same configuration as the previous owner, I can all but guarantee that with you in the cockpit, you will be AFT of the aft limit of the Center of Gravity...a dangerous place to be. Pietenpol's are notoriously tail heavy, probably due to the fact that Bernard Pietenpol weighedabout 160 to 170 lbs. B.H.P. called out the center of gravity range to be between 1/4 and 1/3 of the Chord. This translates to 25% to 33 1/3% of the chord. The chord is 60", so your C G range is between 15" and 20" aft of the leading edge. The aft limit called out by BHP has always concerned me. Very few aircraft have an aft limit that far back. I believe it is due to the undercamberedairfoil. This airfoil has a LOT of negative pitching moment, allowing the aftCG limit to be so far back. If your Pietenpol does not have the airfoil called out in the plans, you CAN NOT use the aft limit called out. If you look at the last few pages of the 'Pietenpol Operation Manual' that I sent you, you can see how to compute C G with paper & pencil. Simple math, but very unforgiving of mistakes. Do the math three times !!Chuck G.NX770CG________________________________________________________________________________

Original Posted By: Rcaprd(at)aol.com
Subject: Re: Pietenpol-List: Weight and BalanceIn a message dated 10/4/04 7:14:52 AM Central Daylight Time, lnelson208(at)yahoo.com writes:>Larry,I just sent you direct, the weight & balance portion of the opps manual. The whole thing contained quite a bit of text, and I wonder if your server limits how much can be included in an e-mail. Let me know if you compute !!Chuck G.________________________________________________________________________________

Original Posted By:
Subject: Pietenpol-List: Weight and BalanceIn a message dated 5/28/2006 6:29:57 PM Central Standard Time, harvey.rule(at)bell.ca writes:I need to know the two balance points on the aircraft.I suspect one is on the seat arm rest(for for and aft) and the other on the top of the wing for left and right.I have searched through the drawings and have come up empty as to thebalance locations on the aircraft for a weight and balance.The AME hasasked me to get in touch with the web to find out what theseare.Thankyou in advance for any info you can provide. I think what you are looking for is the forward and aft Center of Gravity locations. This is the tolorance where the weight of the aircraft loadsthe wing. When doing Weight & Balance, there is no right & left balance points. For the Pietenpol Airfoil, Bernard H. Pietenpol said that it should bemaintained between 1/4 to 1/3 of the chord. This amounts to 25% of the chord for the forward limit, and for the aft limit it would be 33 1/3%. The chord is 60", so the forward limit is 25% of 60", which is 15" behind the leading edge. For the aft limit it would be 33 1/3% of 60", which is 20" behind the leading edge. Therefore, your C. of G. limits are between 15 and 20 inches behind the leading edge. Pietenpols are notorious for coming out with the C. G. close to the aft limit. If the C.G. is behind the aft limit, this is a very dangerous way to fly the plane. Should the wing stall in flight, it might be impossible to get it out of the stalled condition. I don't know of any other airfoils with an aft limit as far back as the Pietenpol. I believe this is because of the undercambered airfoil, which has alarge amount of nose down pitching moment. In saying that, if you use anything other than the Pietenpol airfoil, you Should Not use these limits. YouMust use the limits of the particular airfoil being used.Chuck G.NX770CG________________________________________________________________________________Subject: RE: Pietenpol-List: Weight and BalanceDate: Mon, 29 May 2006 22:30:39 -0400

Original Posted By:
Harvey,A traditional rectangluar wing, flat bottomed, so called NACA wing, has a standard loaded CG range. The CG range is calculated to provide the CG range slightly forward of the center of lift. This forward shift of loaded CG is due to the nature of the weight of the tail feathers and whether they provide additional lift in flight. This standard NACA wing loaded CG range is 25% to 33% of chord. So, assuming a 60" chord line, then this means the loaded operational CG range is 12" to 20" from the leading edge of the wing. The center of lift would be slightly behind the 20" back limit, to assure a nose over stall instead of a tail heavy flat non-recoverable stall. Each moveable item loaded in the plane would have a calculated ARM or distance forward of or behind this datum point (in the case above, meaning the leading edge of the wing). The empty (setting longerons level in hanger) is less important, other than the fact the plane may fall over on it's prop if the empty CG is too far forward of the landing gear. So, here's how you do it, assuming the Pietenpol undercamber wing qualifies as a NACA type. Level up the top longerons, north/south and east/west. You may have to add weight to the tail wheel to keep the nose from tipping over. Now weigh the plane at all three wheels. Drop plumb from the leading edge of the wing and mark it on the floor. Now measure the distance each wheel behind this zero datum line. Multiply the weights at each point the plane touches the ground x distance from datum and you'll get moment. Example- the tail wheel could weigh 10 lbs and be 170" behind the leading edge of wing therefore it's moment is 1700"/lbs. Main gear axles could weigh each 300lbs and be 3" behind the leading edge therefore 1800"/lbs. Divide total moment by total weight and you'll get the empty CG of the plane. Example above continued-- total weight= 610lbs. total moment= 3500"/lbs, therefore empty CG is 5.7" behind the leading edge of the wing. Each plane is different. The empty CG in inches will probably be within a couple inches of the actual main gears axles'. Now sit in the pilot's seat and repeat the process, back calulating the actual movement aft of the loaded CG vs the empty CG, therefore you'll get the actual ARM of the pilot's seat. Do the same for the passenger seat and back calculate the ARM of the passenger. Do the same for fuel added and back calculate. Etc. Do back calculation technique for each moveable thing to be added to the empty plane, to get the safe range for flying loaded CG. Make a chart for your plane and stay within the safe loaded CG range for flying. You'll need help so get someone from the local EAA chapter to help and maybe they have nice accurate scales you can use for these needed weighings. The only variable in the above procedure is the fact that the Piete traditional wing may have less than the 25-33% of chord tolerances for safe loaded flying.Good luckGordon Bowen----- Original Message -----

Original Posted By: Clif Dawson
Subject: Pietenpol-List: Weight and BalanceIn a message dated 12/7/2006 7:10:24 PM Central Standard Time, dslane(at)logical.net writes:I also would like information about weight and balance limits on the airplane.Don,You probably already realize that weight and balance is a term relative to the where the weight balances within the wing chord. Bernard Pietenpol said itshould be between 1/4 and 1/3 of the wing chord. The chord is 60", therefore,the limits are between 15" and 20" behind the leading edge of the wing. I have all the loading configurations for my airplane listed on at the bottom ofthis page of my web site:http://nx770cg.com/OperationsManual.htmlChuck G.NX770CG________________________________________________________________________________Date: Fri, 08 Dec 2006 00:20:26 -0800

Original Posted By: Jeff Boatright
Greetings! Anyone have an excel spreadsheet for weight and balance calculationsfor a Model A powered Aircamper. Fuselage length firewall to tailwheel is 161.5inches. You can contact my email... dwilson(at)ci.austin.mn.usRead this topic online here:http://forums.matronics.com/viewtopic.p ... ______Date: Thu, 30 Oct 2008 23:22:58 -0400

Original Posted By: "Ryan Mueller"

Original Posted By: "Ryan Mueller"

Original Posted By: "walt"

Original Posted By: Michael Perez

Original Posted By: Jeff Boatright

Original Posted By: "KMHeide, BA, CPO, FAAOP"
Jeff,I think I understand the question now. You are concerned about buckling.In compression, the strut assembly will act like a column. The longer anunsupported column is, the more prone to buckling it becomes. If thecompression forces on the ends of a column are large enough (based on thespecific geometry and physical characteristics of the column), once thecolumn starts to buckle, it can suffer a catastrophic collapse. This type offailure can be avoided by a couple of methods. One is to change thestructure of the column (larger profile, thicker wall thickness, differentmaterials, etc), and the other method is to provide some intermediatesupport(s) to effectively shorten the unsupported length of the column. Thesecond of these methods is recommended for the Pietenpol. This is achievedby the addition of jury struts. The lift struts on the Air Camper are abouteight feet long, but with the addition of jury struts, the unsupportedlength becomes roughly half of that. Since the relationship between bucklingforce and column length is an inverse square, reducing the length by halfmeans that the forces required to buckle the new shorter length increase bya factor of four (likewise, if the length of a column is doubled, the forcerequired to buckle the longer column is only one fourth). The jury strutsdo very little in ideal flight conditions - straight, level flight, in calmair, followed by a perfect, soft-as-a-feather landing on a smooth-as-glassrunway. The only possible problem under these conditions would be if theairflow over the lift struts were to cause the struts to flutter, orvibrate. The addition of the jury struts will help to alleviate thissituation. In this instance, the jury struts should be attached at a pointthat is NOT the midpoint of the strut length, as attachment at the midpointcan allow harmonic vibration to occur, and multiply. Unfortunately, most ofus have to live in the real world (except for one weekend in July each year,at a small airport in southern Wisconsin). That real world includesturbulent air, and occasional hard landings and rough runways (or fields)among other things. These conditions all have the power to impart negative Gforces on the plane and its occupants. When the Air Camper is put intonegative G conditions, the wings (especially the 3-piece wing) will tend topivot downward, putting the lift struts into compression, rather thantension. When the lift struts are in compression, they begin to act like thecolumns mentioned above. Unsupported, the lift struts might collapse whensubjected to these negative G forces. The consequences are nasty if ithappens on the ground, but likely fatal if occuring in flight. So, jurystruts are a good thing to have on an Air Camper.Now, with respect to your question, as I mentioned, the calculations todetermine the "side loads" the strut ends might encounter are difficult todetermine. But, just out of curiosity, I did a few calculations to try todetermine how much longer your lift struts might need to be extended, inorder to give the wing the dihedral you are desiring. I randomly chose adimension of 2" for the dihedral (seems about right). Since the lift strutsare attached at roughly half way between the fuselage and the wingtip, andthe struts are angled at approximately 30 degrees, the resulting lift strutwill only need to be extended by approximately 1/2". I'm not sure, but Ithink that Cub lift strut ends are 7/16" (correct me if that's not right).The forces required to bend a 7/16" diameter bolt would be huge. I wouldthink that your strut attachment brackets would get ripped out of the planebefore the strut ends would fail (the old "weakest link in the chain", onceagain).The short answer is that I don't think that extending your strut ends anextra 1/2" is going to put you at risk (provided the threaded rod is longenough to keep the threads properly engaged).Anybody have a differing view on this matter?Bill C. ________________________________________________________________________________Date: Fri, 31 Oct 2008 11:46:19 -0700 (PDT)

Original Posted By: "dwilson"
________________________________________________________________________________Subject: Pietenpol-List: Weight and Balance