Original Posted By: Isablcorky(at)aol.com
Back when Corky was doing his final w&b on NX41CC, he posted the weights and measurements used for the calculations on his airplane. After some worrying about whether it was going to work or not, things turned out just fine and I saved his w&b post in my "keeper" file along with Doc Mosher's useful info from some of the old CAA design manuals. Last night I took out Corky's data again to do some 'what-if' calculations to see what it would take to throw a Piet out of balance. It's tough! The worst-case forward CG scenario I could come up with was full fuel and a very light pilot (my 90 lb. daughter), which put the CG at 13.9" aft of datum (wing LE) and all-up weight of 817 lbs. Worst-case aft CG scenario I dreamed up was a 220 lb. pilot, 200 lb. passenger, 6 lbs. of charts and water bottle in the "baggage compartment", and nothing but fumes in the fuel tank (2 gal.)... let's call it the last ride of the day at a fly-in ;o) This produced a weight of 1153 lbs. and a CG 19.53" aft of datum. Now I don't know what NX41CC's max gross is, but this weight would really be pushing any Piet except John Dilatush's on a hot afternoon. The CG would still be OK on paper.A similar situation, with 185 lb. pilot, no passenger, 6 lbs. of "baggage" and 2 gals. of fuel, pushed the CG to 20.66" aft of datum at a weight of 834 lbs. and turned out to be about the furthest aft I could get the CG in a real-life situation. The gross weight would be much better than the previous scenario which means climb would be OK but control might be iffy as far as getting a little funny on the elevator and easy to stall without enough nose-down authority.The suggested design limits of 22% to 34% of MAC would be about 13" to 20" aft of LE for the Pietenpol with a 60" chord, so it would appear that Corky's plane is about as close to perfect as you can get these things.That guy Pietenpol...! If you build it the way he designed it, I guess it will work!Oscar ZunigaSan Antonio, TX________________________________________________________________________________
Pietenpol-List: weight & balance
Re: Pietenpol-List: weight & balance
Original Posted By: Michael D Cuy
Subject: Re: Pietenpol-List: weight & balanceOscar,Yes, 41CC does fly near perfect and Edwin and I are proud. However; we changed from a 22 lb metal prop to a 7 1/2 wooden prop. Flying last Sat for nearly 2 hrs I had to hold forward pressure on the stick when at climb or cruise. Not much but enough that when I released the stick the nose just turned upwards. Not abruptly. We came in with about 5 gals, forward fuel tank, with no noticable tail heaviness more than when we took off. I don't plan any rigging change until I fly it solo, soon I hope. I have a simple Rude Goldberg trim system which works satisfactorily. With no passenger and my extra weight, 190 lbs, I may have to move the wing rearward about 1/2 inch. We'll see.Corky________________________________________________________________________________Date: Fri, 11 Apr 2003 15:15:06 -0400
Subject: Re: Pietenpol-List: weight & balanceOscar,Yes, 41CC does fly near perfect and Edwin and I are proud. However; we changed from a 22 lb metal prop to a 7 1/2 wooden prop. Flying last Sat for nearly 2 hrs I had to hold forward pressure on the stick when at climb or cruise. Not much but enough that when I released the stick the nose just turned upwards. Not abruptly. We came in with about 5 gals, forward fuel tank, with no noticable tail heaviness more than when we took off. I don't plan any rigging change until I fly it solo, soon I hope. I have a simple Rude Goldberg trim system which works satisfactorily. With no passenger and my extra weight, 190 lbs, I may have to move the wing rearward about 1/2 inch. We'll see.Corky________________________________________________________________________________Date: Fri, 11 Apr 2003 15:15:06 -0400
Re: Pietenpol-List: weight & balance
Original Posted By: "walter evans"
Subject: Re: Pietenpol-List: weight & balanceMike,Can't answer the fuel differential question as I can't afford to fill the tank. Maybe I'll get a loan from Edwin and we'll answer. However it's not too much and with my little tab rigging it won't even be noticable.Corky________________________________________________________________________________
Subject: Re: Pietenpol-List: weight & balanceMike,Can't answer the fuel differential question as I can't afford to fill the tank. Maybe I'll get a loan from Edwin and we'll answer. However it's not too much and with my little tab rigging it won't even be noticable.Corky________________________________________________________________________________
Pietenpol-List: weight & balance
Original Posted By: "Fairfield, Mike"
Okay, so really, builders don't need to be waiting till their aircraft are almostfinished before thinking about W&B. In fact, the earlier you start to thinkabout it and start getting numbers in your head, the more confident you'll beabout it when it comes time to do the final, actual W&B and fill in the formsthat you'll show at the end. Once you have the bare fuselage -covered or not-on the gear, you're ready to start measuring and weighing. At that point youcan start plugging some numbers into a W&B spreadsheet and it will be eveneasier if you don't have the wings or engine on the bare fuselage because youcan move it around the shop or hangar very easily. Not only that but if you don'thave the cabanes and centersection mounted yet, it will be even easier toget your helper to climb into that front cockpit to do the weighing to get thepassenger moment arm calculated.With the fuselage on the gear (as long as the geometry is locked in and the gearmounting brackets are actually bolted to the fuselage or at least pinned inplace in final locations), you can determine the various moment arms for the maingear and tailwheel, as well as the moment arms for pilot and passenger. Ifyou're using a nose tank you can also determine the moment arm for it if youhave the tank fabricated and can set it temporarily in place in the forward fuselage.All of this can be done with nothing more than masking tape, markers,a string and plumb bob or fishing weight, and a couple of simple bathroom scalessince the accuracy of the scales doesn't matter too much at that point. They just need to be reasonably accurate and the readings repeatable, and theactual weights won't matter much in order to determine moment arms.As a starting point I can offer the Excel spreadsheet that I've used for the W&Bon 41CC, and I can probably also cook up a simple spreadsheet for coming upwith the passenger and pilot moment arms after you've taken some simple readingson a rainy workshop day when you and a helper are able to make some measurementsslowly, carefully, and thoughtfully. If you do it right the first time,you'll never have to do it again. The upside to all of this is that if you startthe process early, you can make adjustments as you go along and not get surprisedat the very end when you find out your airplane has a heavy tail andyou have to find a way to offset or move it.--------Oscar ZunigaMedford, ORAir Camper NX41CC "Scout"A75 powerRead this topic online here:http://forums.matronics.com/viewtopic.p ... __________
Okay, so really, builders don't need to be waiting till their aircraft are almostfinished before thinking about W&B. In fact, the earlier you start to thinkabout it and start getting numbers in your head, the more confident you'll beabout it when it comes time to do the final, actual W&B and fill in the formsthat you'll show at the end. Once you have the bare fuselage -covered or not-on the gear, you're ready to start measuring and weighing. At that point youcan start plugging some numbers into a W&B spreadsheet and it will be eveneasier if you don't have the wings or engine on the bare fuselage because youcan move it around the shop or hangar very easily. Not only that but if you don'thave the cabanes and centersection mounted yet, it will be even easier toget your helper to climb into that front cockpit to do the weighing to get thepassenger moment arm calculated.With the fuselage on the gear (as long as the geometry is locked in and the gearmounting brackets are actually bolted to the fuselage or at least pinned inplace in final locations), you can determine the various moment arms for the maingear and tailwheel, as well as the moment arms for pilot and passenger. Ifyou're using a nose tank you can also determine the moment arm for it if youhave the tank fabricated and can set it temporarily in place in the forward fuselage.All of this can be done with nothing more than masking tape, markers,a string and plumb bob or fishing weight, and a couple of simple bathroom scalessince the accuracy of the scales doesn't matter too much at that point. They just need to be reasonably accurate and the readings repeatable, and theactual weights won't matter much in order to determine moment arms.As a starting point I can offer the Excel spreadsheet that I've used for the W&Bon 41CC, and I can probably also cook up a simple spreadsheet for coming upwith the passenger and pilot moment arms after you've taken some simple readingson a rainy workshop day when you and a helper are able to make some measurementsslowly, carefully, and thoughtfully. If you do it right the first time,you'll never have to do it again. The upside to all of this is that if you startthe process early, you can make adjustments as you go along and not get surprisedat the very end when you find out your airplane has a heavy tail andyou have to find a way to offset or move it.--------Oscar ZunigaMedford, ORAir Camper NX41CC "Scout"A75 powerRead this topic online here:http://forums.matronics.com/viewtopic.p ... __________
RE: Pietenpol-List: weight & balance
Original Posted By: owner-pietenpol-list-server(at)matronics.com [mailto:owner-pietenpol-list-server(at)matronics.com] On Behalf Of taildrags
Good morning Oscar, I for one, would be interested in your spreadsheet if you would be so kind.Thanks, Mike the canuck-----Original Message-----
Good morning Oscar, I for one, would be interested in your spreadsheet if you would be so kind.Thanks, Mike the canuck-----Original Message-----
Re: Pietenpol-List: weight & balance
Original Posted By: "Charles N. Campbell"
Subject: Re: Pietenpol-List: weight & balance
Subject: Re: Pietenpol-List: weight & balance
Pietenpol-List: Re: Corvair College
Original Posted By: Ray Krause
Folks,I want to second the recommendation about attending a Corvair College. Even if you are going to install an XYZ engine, certified or otherwiseyou will come a way with a better understanding of internal combustionengines. Even if you do not have a Corvair engine, go a meet peoplethat brought theirs and ask them if you can be their "slave". Help themin any way you can. Take some nitrile gloves and a gallon of paintthinner with you. Pick up a couple of empty antifreeze jugs, lay on theside and cut out the label area, and use as a small parts cleaner. Offer to use the thinner and clean parts for them. You will meet somewonderful people and make some wonderful memories. Take a responsibleand interested kid with you. I think that the Corvair College iswithout a doubt, the best technical event in homebuilding. You pay foryour meals....no fees are charged for the learning you will get....whatis not to like? William Wynne is a great teacher. Wright downquestions you have about engines before you go and you can get theanswers there. No politics or religion discussions are allowed, justengine talk. Sign up early......Just do it!I went to Barnwell, SC Corvair College and hope to go back this year.Jim BrewerAlbemarle, NC________________________________________________________________________________
Folks,I want to second the recommendation about attending a Corvair College. Even if you are going to install an XYZ engine, certified or otherwiseyou will come a way with a better understanding of internal combustionengines. Even if you do not have a Corvair engine, go a meet peoplethat brought theirs and ask them if you can be their "slave". Help themin any way you can. Take some nitrile gloves and a gallon of paintthinner with you. Pick up a couple of empty antifreeze jugs, lay on theside and cut out the label area, and use as a small parts cleaner. Offer to use the thinner and clean parts for them. You will meet somewonderful people and make some wonderful memories. Take a responsibleand interested kid with you. I think that the Corvair College iswithout a doubt, the best technical event in homebuilding. You pay foryour meals....no fees are charged for the learning you will get....whatis not to like? William Wynne is a great teacher. Wright downquestions you have about engines before you go and you can get theanswers there. No politics or religion discussions are allowed, justengine talk. Sign up early......Just do it!I went to Barnwell, SC Corvair College and hope to go back this year.Jim BrewerAlbemarle, NC________________________________________________________________________________
Re: Pietenpol-List: weight & balance
Original Posted By:>> owner-pietenpol-list-server(at)matronics.com [mailto:owner-pietenpol-l
I would like it, too. But for a one wholer! Ran the engine yesterday! Progress gets slower and slower, but going forever forward.Ray KrauseSkyScout N667RKSent from my iPad> On Feb 17, 2016, at 5:42 AM, Charles N. Campbell wrote:> > Me, too. Chuck> >> On Wed, Feb 17, 2016 at 8:08 AM, Fairfield, Mike wrote:t.ca>>> >> Good morning Oscar,>> >> I for one, would be interested in your spreadsheet if you would be so kind.>> >> Thanks, Mike the canuck>> >> -----Original Message-----
I would like it, too. But for a one wholer! Ran the engine yesterday! Progress gets slower and slower, but going forever forward.Ray KrauseSkyScout N667RKSent from my iPad> On Feb 17, 2016, at 5:42 AM, Charles N. Campbell wrote:> > Me, too. Chuck> >> On Wed, Feb 17, 2016 at 8:08 AM, Fairfield, Mike wrote:t.ca>>> >> Good morning Oscar,>> >> I for one, would be interested in your spreadsheet if you would be so kind.>> >> Thanks, Mike the canuck>> >> -----Original Message-----
>> Pietenpol-List: weight & balance
Original Posted By: Jim Boyer
Re: Pietenpol-List: weight & balance
Original Posted By: Jim Boyer
Pietenpol-List: Re: weight & balance
Original Posted By: "taildrags"
Tim,Very interesting comments and well written, thanks.Ray KrauseSent from my iPad> On Feb 18, 2016, at 10:03 AM, Timothy Willis wrote:> > =8B> Oscar is certainly right to recommend a pre-build spreadsheet for W&B, in order to plan well and to save iterations-- Plan B,C,D.... Years ago I wrote a fab pre-build W&B spreadsheet. Unfortunately that was a PC crash and several PCs ago, and I no longer have it. However I will share a feature and some findings. > > I had a "what if" feature in the Excel model so that I could move a battery fore or aft to improve balance. Of course moving it away from the firewall also adds longer heavy wiring. Thus IMO this partial solution falls among the category of "desperate corrective measures."> > Slanting the wings aft obviously is a very effective way to alter CG to within bounds. My major concern as a fat boy has been my nearly 100 lbs. over the 170-pound "FAA pilot." I discovered that every 25 pounds of added pilot weight required a movement of the wing back one inch. My setup features an A-65, and while I did also test for a Corvair instead, I do not recall those comparative data. I did not run versions with a Model A engine, radiator, etc. > > My setup also features an 18 gallon fuselage tank, which accentuates W&B considerations... about 100 lbs. (16 gals) difference between full and empty-useable. In this regard a wing tank empty/full and a passenger yes/no made almost no difference. I added a "thousand pound passenger" as a test, and it moved the resultant CG nearly nil, under an inch, since both are right at the CG. > > I have concluded that I will slant my cabanes aft 6 inches. If in actual practice that is not enough, I will develop a close relationship with Jenny Craig, a virtuous step in its own right.> > Tim in Central TX > =================> > >> Okay, so really, builders don't need to be waiting till their aircraft are almost finished before thinking about W&B. In fact, the earlier you start to think about it and start getting numbers in your head, the more confident you'll be about it when it comes time to do the final, actual W&B and fill in the forms that you'll show at the end. Once you have the bare fuselage -covered or not- on the gear, you're ready to start measuring and weighing. At that point you can start plugging some numbers into a W&B spreadsheet and it will be even easier if you don't have the wings or engine on the bare fuselage because you can move it around the shop or hangar very easily. Not only that but if you don't have the cabanes and centersection mounted yet, it will be even easier to get your helper to climb into that front cockpit to do the weighing to get the passenger moment arm calculated.> >> > >> With the fuselage on the gear (as long as the geometry is locked in and the gear mounting brackets are actually bolted to the fuselage or at least pinned in place in final locations), you can determine the various moment arms for the main gear and tailwheel, as well as the moment arms for pilot and passenger. If you're using a nose tank you can also determine the moment arm for it if you have the tank fabricated and can set it temporarily in place in the forward fuselage. All of this can be done with nothing more than masking tape, markers, a string and plumb bob or fishing weight, and a couple of simple bathroom scales since the accuracy of the scales doesn't matter too much at that point. They just need to be reasonably accurate and the readings repeatable, and the actual weights won't matter much in order to determine moment arms.> >> > >> As a starting point I can offer the Excel spreadsheet that I've used for the W&B on 41CC, and I can probably also cook up a simple spreadsheet for com ing up with the passenger and pilot moment arms after you've taken some simple readings on a rainy workshop day when you and a helper are able to make some measurements slowly, carefully, and thoughtfully. If you do it right the first time, you'll never have to do it again. The upside to all of this is that if you start the process early, you can make adjustments as you go along and not get surprised at the very end when you find out your airplane has a heavy tail and you have to find a way to offset or move it.> >> --------> >> Oscar Zuniga> >> Medford, OR> >> Air Camper NX41CC "Scout"> >> A75 power________________________________________________________________________________Subject: Pietenpol-List: Re: weight & balance
Tim,Very interesting comments and well written, thanks.Ray KrauseSent from my iPad> On Feb 18, 2016, at 10:03 AM, Timothy Willis wrote:> > =8B> Oscar is certainly right to recommend a pre-build spreadsheet for W&B, in order to plan well and to save iterations-- Plan B,C,D.... Years ago I wrote a fab pre-build W&B spreadsheet. Unfortunately that was a PC crash and several PCs ago, and I no longer have it. However I will share a feature and some findings. > > I had a "what if" feature in the Excel model so that I could move a battery fore or aft to improve balance. Of course moving it away from the firewall also adds longer heavy wiring. Thus IMO this partial solution falls among the category of "desperate corrective measures."> > Slanting the wings aft obviously is a very effective way to alter CG to within bounds. My major concern as a fat boy has been my nearly 100 lbs. over the 170-pound "FAA pilot." I discovered that every 25 pounds of added pilot weight required a movement of the wing back one inch. My setup features an A-65, and while I did also test for a Corvair instead, I do not recall those comparative data. I did not run versions with a Model A engine, radiator, etc. > > My setup also features an 18 gallon fuselage tank, which accentuates W&B considerations... about 100 lbs. (16 gals) difference between full and empty-useable. In this regard a wing tank empty/full and a passenger yes/no made almost no difference. I added a "thousand pound passenger" as a test, and it moved the resultant CG nearly nil, under an inch, since both are right at the CG. > > I have concluded that I will slant my cabanes aft 6 inches. If in actual practice that is not enough, I will develop a close relationship with Jenny Craig, a virtuous step in its own right.> > Tim in Central TX > =================> > >> Okay, so really, builders don't need to be waiting till their aircraft are almost finished before thinking about W&B. In fact, the earlier you start to think about it and start getting numbers in your head, the more confident you'll be about it when it comes time to do the final, actual W&B and fill in the forms that you'll show at the end. Once you have the bare fuselage -covered or not- on the gear, you're ready to start measuring and weighing. At that point you can start plugging some numbers into a W&B spreadsheet and it will be even easier if you don't have the wings or engine on the bare fuselage because you can move it around the shop or hangar very easily. Not only that but if you don't have the cabanes and centersection mounted yet, it will be even easier to get your helper to climb into that front cockpit to do the weighing to get the passenger moment arm calculated.> >> > >> With the fuselage on the gear (as long as the geometry is locked in and the gear mounting brackets are actually bolted to the fuselage or at least pinned in place in final locations), you can determine the various moment arms for the main gear and tailwheel, as well as the moment arms for pilot and passenger. If you're using a nose tank you can also determine the moment arm for it if you have the tank fabricated and can set it temporarily in place in the forward fuselage. All of this can be done with nothing more than masking tape, markers, a string and plumb bob or fishing weight, and a couple of simple bathroom scales since the accuracy of the scales doesn't matter too much at that point. They just need to be reasonably accurate and the readings repeatable, and the actual weights won't matter much in order to determine moment arms.> >> > >> As a starting point I can offer the Excel spreadsheet that I've used for the W&B on 41CC, and I can probably also cook up a simple spreadsheet for com ing up with the passenger and pilot moment arms after you've taken some simple readings on a rainy workshop day when you and a helper are able to make some measurements slowly, carefully, and thoughtfully. If you do it right the first time, you'll never have to do it again. The upside to all of this is that if you start the process early, you can make adjustments as you go along and not get surprised at the very end when you find out your airplane has a heavy tail and you have to find a way to offset or move it.> >> --------> >> Oscar Zuniga> >> Medford, OR> >> Air Camper NX41CC "Scout"> >> A75 power________________________________________________________________________________Subject: Pietenpol-List: Re: weight & balance
Pietenpol-List: Re: weight & balance
Original Posted By: "taildrags"
For all those who asked, I've uploaded my W&B spreadsheet to the forum but if you'reunable to get it that way, email me privately and I'll send it to you. The usual caveats apply, especially "the numbers in this spreadsheet are for NX41CCONLY!" Do not use them for your airplane except as a starting point soyou can check to see if your numbers are reasonable. The other thing I'd liketo mention is that I did not author this spreadsheet. It was generously sharedwith me and it is in that spirit that I share it with others. Like Tim, Ialso added another tab so that I would have a "what-if sandbox" to play in withoutmessing up the REAL sheet with the real numbers. In fact, I would suggestthat once you enter your final numbers into the real sheet, that you lock thosecells so you can't inadvertently change the numbers that shouldn't change.Ray: the spreadsheet doesn't care if you have a one-holer, two-holer, or twelve-holer...you can either leave the numbers for passenger weight and moment armas "zero", or else eliminate those cells to streamline the spreadsheet. Andif you're building a 3-cockpit Air Camper, just add rows for another cockpit andpassenger ;o)As I mentioned, you don't need to have a complete airplane to start entering valuesinto the sheet. For sure you can add the basic information at the top, butthen as you measure the moment arms relative to the datum that you choose,you can start entering those values into the sheet and begin playing what-ifs.If the datum that you choose is going to be the wing leading edge and you don'thave the centersection mounted yet, you'll have to enter values relative tothe firewall and then later adjust those numbers when the distance from leadingedge to firewall is determined. I have set the precision of weights and momentarms to one decimal place (roughly to the nearest 2 oz and 1/8"). I'veplayed with it by increasing the precision of them one at a time and then bothtogether, but I decided that I do not have eyes or tools that can measure closerthan that. I've tried decreasing the precision to whole pounds and inchesonly, but that is unsatisfactory. If I were going to simplify one of the two,I would use whole pounds but keep tenths of an inch of length.You may argue about the acceptable range of 15 to 20" aft of wing leading edgefor the CG and you may argue about the allowable maximum gross weight of 1,088lbs. You just won't be arguing them with me ;o)Anyway, here is the spreadsheet.--------Oscar ZunigaMedford, ORAir Camper NX41CC "Scout"A75 powerRead this topic online here:http://forums.matronics.com/viewtopic.p ... ttachments: http://forums.matronics.com//files/nx41 ... ___Subject: Pietenpol-List: Re: weight & balance
For all those who asked, I've uploaded my W&B spreadsheet to the forum but if you'reunable to get it that way, email me privately and I'll send it to you. The usual caveats apply, especially "the numbers in this spreadsheet are for NX41CCONLY!" Do not use them for your airplane except as a starting point soyou can check to see if your numbers are reasonable. The other thing I'd liketo mention is that I did not author this spreadsheet. It was generously sharedwith me and it is in that spirit that I share it with others. Like Tim, Ialso added another tab so that I would have a "what-if sandbox" to play in withoutmessing up the REAL sheet with the real numbers. In fact, I would suggestthat once you enter your final numbers into the real sheet, that you lock thosecells so you can't inadvertently change the numbers that shouldn't change.Ray: the spreadsheet doesn't care if you have a one-holer, two-holer, or twelve-holer...you can either leave the numbers for passenger weight and moment armas "zero", or else eliminate those cells to streamline the spreadsheet. Andif you're building a 3-cockpit Air Camper, just add rows for another cockpit andpassenger ;o)As I mentioned, you don't need to have a complete airplane to start entering valuesinto the sheet. For sure you can add the basic information at the top, butthen as you measure the moment arms relative to the datum that you choose,you can start entering those values into the sheet and begin playing what-ifs.If the datum that you choose is going to be the wing leading edge and you don'thave the centersection mounted yet, you'll have to enter values relative tothe firewall and then later adjust those numbers when the distance from leadingedge to firewall is determined. I have set the precision of weights and momentarms to one decimal place (roughly to the nearest 2 oz and 1/8"). I'veplayed with it by increasing the precision of them one at a time and then bothtogether, but I decided that I do not have eyes or tools that can measure closerthan that. I've tried decreasing the precision to whole pounds and inchesonly, but that is unsatisfactory. If I were going to simplify one of the two,I would use whole pounds but keep tenths of an inch of length.You may argue about the acceptable range of 15 to 20" aft of wing leading edgefor the CG and you may argue about the allowable maximum gross weight of 1,088lbs. You just won't be arguing them with me ;o)Anyway, here is the spreadsheet.--------Oscar ZunigaMedford, ORAir Camper NX41CC "Scout"A75 powerRead this topic online here:http://forums.matronics.com/viewtopic.p ... ttachments: http://forums.matronics.com//files/nx41 ... ___Subject: Pietenpol-List: Re: weight & balance