---------------------------------------------------------- Pietenpol-List Digest Archive --- Total Messages Posted Tue 10/08/13: 19 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 06:34 AM - front strut to rear strut brace? (nightmare) 2. 07:08 AM - Re: Re: One bladed propeller (Steven Dortch) 3. 08:08 AM - Re: Re: One bladed propeller (Steve Emo) 4. 08:26 AM - Re: Re: One bladed propeller (David) 5. 09:27 AM - Re: Re: One bladed propeller (Bkemike) 6. 09:34 AM - Re: Re: strut attachment (TOM MICHELLE BRANT) 7. 10:24 AM - Need email (danhelsper@aol.com) 8. 10:32 AM - Re: Need email (Ken Bickers) 9. 12:26 PM - Re: Mr Sam - Pietenpol N687MB (Fun2av8) 10. 12:52 PM - Re: How straight is straight? (Larry Williams) 11. 02:59 PM - Re: Mr Sam - Pietenpol N687MB (taildrags) 12. 05:01 PM - Re: Re: How straight is straight? (danhelsper@aol.com) 13. 05:14 PM - Re: Re: Mr Sam - Pietenpol N687MB (John Weber) 14. 05:45 PM - Re: Mr Sam - Pietenpol N687MB (Fun2av8) 15. 06:02 PM - Re: Mr Sam - Pietenpol N687MB (Fun2av8) 16. 06:31 PM - Re: Re: How straight is straight? (Dan Yocum) 17. 06:40 PM - Re: Re: How straight is straight? (Steven Dortch) 18. 07:00 PM - Re: Re: Mr Sam - Pietenpol N687MB (Steven Dortch) 19. 09:04 PM - Re: Mr Sam - Pietenpol N687MB (taildrags) ________________________________ Message 1 _____________________________________ Time: 06:34:05 AM PST US Subject: Pietenpol-List: front strut to rear strut brace? From: "nightmare" Not sure its name. But in reference to the brace that goes from the forward strut to the rear strut just below the jury struts, is it really needed? What does it actually do? -------- Paul Donahue Started 8-3-12 do not archive Read this topic online here: http://forums.matronics.com/viewtopic.php?p=410059#410059 ________________________________ Message 2 _____________________________________ Time: 07:08:51 AM PST US Subject: Re: Pietenpol-List: Re: One bladed propeller From: Steven Dortch WF2, Why was it not practical for everyday flying? Granted it is a more complex prop and would be more expensive to build. It would require more thought to make sure it was installed correctly. Once installed and setup, it has all the advantages of an adjustable prop without the additonal hardware and complexity. What are the wear issues? On my other list there is an aerodynamacyst and he has explaned the advantages of one blade. But quite simply, it is easier to build a two bladed fixed prop. On my Vtail it has a two bladed 88 inch prop. This is more efficient than the later and shorter 84 inch prop. Newer models have IO 550s (300HP) that all have 3 blade props. The 3 blade is less efficient, but shorter (less ground strikes) and quieter. Besides it looks "sexier". For a given HP about 1000 to 1300 RPM with a big bladed prop (fewer blades is better) is the most efficient. However, most engines make their HP at higher RPM. On Mon, Oct 7, 2013 at 12:42 PM, womenfly2 wrote: > > Seen it fly at Sentimental Journey this year. They did a demo flight > comparing a standard prop J-3 to an Everal Prop J-3. Everal prop was hard > to beat! > > Climbed faster at a more AOA, faster in level flight. Great idea, but was > not practical for every day flying. > > Cool video! > WF2 > > -------- > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=410007#410007 > > ________________________________ Message 3 _____________________________________ Time: 08:08:59 AM PST US Subject: Re: Pietenpol-List: Re: One bladed propeller From: Steve Emo wouldn't a one bladed prop side load the crankshaft/bearing? Putting a bend ing moment at the hub that isn't there with a two or more bladed design. The trailing blades don't get the clean air the leading blade had. Steve > On Oct 8, 2013, at 10:08 AM, Steven Dortch wro te: > > WF2, Why was it not practical for everyday flying? > > Granted it is a more complex prop and would be more expensive to build. I t would require more thought to make sure it was installed correctly. > Once installed and setup, it has all the advantages of an adjustable prop w ithout the additonal hardware and complexity. > > What are the wear issues? > > On my other list there is an aerodynamacyst and he has explaned the advant ages of one blade. But quite simply, it is easier to build a two bladed fixe d prop. > > On my Vtail it has a two bladed 88 inch prop. This is more efficient than the later and shorter 84 inch prop. Newer models have IO 550s (300HP) that a ll have 3 blade props. The 3 blade is less efficient, but shorter (less grou nd strikes) and quieter. Besides it looks "sexier". > > For a given HP about 1000 to 1300 RPM with a big bladed prop (fewer blades is better) is the most efficient. However, most engines make their HP at hi gher RPM. > >> On Mon, Oct 7, 2013 at 12:42 PM, womenfly2 wrote : > >> >> Seen it fly at Sentimental Journey this year. They did a demo flight comp aring a standard prop J-3 to an Everal Prop J-3. Everal prop was hard to bea t! >> >> Climbed faster at a more AOA, faster in level flight. Great idea, but was not practical for every day flying. >> >> Cool video! >> WF2 >> >> -------- >> >> >> >> >> >> >> Read this topic online here: >> >> http://forums.matronics.com/viewtopic.php?p=410007#410007 >> s List Un/Subscription, >> www.matronics.com/Navigator?Pietenpol-List" target="_blank">http://www. matronics.com/Navigator?Pietenpol-List >> ronics.com/" target="_blank">http://forums.matronics.com >> Matt Dralle, List Admin. >> ==== > > > 3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3 D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D 3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3 D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D 3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3 D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D 3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3 D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > ________________________________ Message 4 _____________________________________ Time: 08:26:01 AM PST US From: "David" Subject: RE: Pietenpol-List: Re: One bladed propeller Single bladed props were used in the 50s for control line racing models for this exact reason. I recall that the efficiency of a single bladed prop is only matched by contra-rotating props, but I could be wrong on that. Like most things. :-) _____ From: owner-pietenpol-list-server@matronics.com [mailto:owner-pietenpol-list-server@matronics.com] On Behalf Of Steve Emo Sent: Tuesday, October 08, 2013 8:08 AM Subject: Re: Pietenpol-List: Re: One bladed propeller wouldn't a one bladed prop side load the crankshaft/bearing? Putting a bending moment at the hub that isn't there with a two or more bladed design. The trailing blades don't get the clean air the leading blade had. Steve On Oct 8, 2013, at 10:08 AM, Steven Dortch wrote: WF2, Why was it not practical for everyday flying? Granted it is a more complex prop and would be more expensive to build. It would require more thought to make sure it was installed correctly. Once installed and setup, it has all the advantages of an adjustable prop without the additonal hardware and complexity. What are the wear issues? On my other list there is an aerodynamacyst and he has explaned the advantages of one blade. But quite simply, it is easier to build a two bladed fixed prop. On my Vtail it has a two bladed 88 inch prop. This is more efficient than the later and shorter 84 inch prop. Newer models have IO 550s (300HP) that all have 3 blade props. The 3 blade is less efficient, but shorter (less ground strikes) and quieter. Besides it looks "sexier". For a given HP about 1000 to 1300 RPM with a big bladed prop (fewer blades is better) is the most efficient. However, most engines make their HP at higher RPM. On Mon, Oct 7, 2013 at 12:42 PM, womenfly2 wrote: Seen it fly at Sentimental Journey this year. They did a demo flight comparing a standard prop J-3 to an Everal Prop J-3. Everal prop was hard to beat! Climbed faster at a more AOA, faster in level flight. Great idea, but was not practical for every day flying. Cool video! WF2 -------- Read this topic online here: http://forums.matronics.com/viewtopic.php?p=410007#410007 s List Un/Subscription, www.matronics.com/Navigator?Pietenpol-List" target="_blank">http://www.matronics.com/Navigator?Pietenpol-List ronics.com/" target="_blank">http://forums.matronics.com Matt Dralle, List Admin. ==== ________________________________ Message 5 _____________________________________ Time: 09:27:27 AM PST US From: Bkemike Subject: Re: Pietenpol-List: Re: One bladed propeller Steve, You're quite correct that a hard-mounted one-blade prop would put significan t bending moments into the shaft...shades of crank-snapping Corvairs. You may not have noticed in the video that the one-blade prop is free to mov e fore and aft about an axis through the hub. This eliminates all the bendin g moments that a hard-mounted one-blade would produce. Mike Hardaway Scratched on an iPad with blunt instruments. On Oct 8, 2013, at 8:08 AM, Steve Emo wrote: > wouldn't a one bladed prop side load the crankshaft/bearing? Putting a be nding moment at the hub that isn't there with a two or more bladed design. > > The trailing blades don't get the clean air the leading blade had. > > Steve > > On Oct 8, 2013, at 10:08 AM, Steven Dortch wro te: > >> WF2, Why was it not practical for everyday flying? >> >> Granted it is a more complex prop and would be more expensive to build. I t would require more thought to make sure it was installed correctly. >> Once installed and setup, it has all the advantages of an adjustable prop without the additonal hardware and complexity. >> >> What are the wear issues? >> >> On my other list there is an aerodynamacyst and he has explaned the advan tages of one blade. But quite simply, it is easier to build a two bladed fix ed prop. >> >> On my Vtail it has a two bladed 88 inch prop. This is more efficient tha n the later and shorter 84 inch prop. Newer models have IO 550s (300HP) that all have 3 blade props. The 3 blade is less efficient, but shorter (less gr ound strikes) and quieter. Besides it looks "sexier". >> >> For a given HP about 1000 to 1300 RPM with a big bladed prop (fewer blade s is better) is the most efficient. However, most engines make their HP at h igher RPM. >> >> On Mon, Oct 7, 2013 at 12:42 PM, womenfly2 wrote : m> >>> >>> Seen it fly at Sentimental Journey this year. They did a demo flight com paring a standard prop J-3 to an Everal Prop J-3. Everal prop was hard to be at! >>> >>> Climbed faster at a more AOA, faster in level flight. Great idea, but wa s not practical for every day flying. >>> >>> Cool video! >>> WF2 >>> >>> -------- >>> >>> >>> >>> >>> >>> >>> Read this topic online here: >>> >>> http://forums.matronics.com/viewtopic.php?p=410007#410007 >>> s List Un/Subscription, >>> www.matronics.com/Navigator?Pietenpol-List" target="_blank">http://www .matronics.com/Navigator?Pietenpol-List >>> ronics.com/" target="_blank">http://forums.matronics.com >>> Matt Dralle, List Admin. >>> ==== > > 3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3 D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D 3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3 D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D 3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3 D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D 3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3 D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > ________________________________ Message 6 _____________________________________ Time: 09:34:33 AM PST US From: TOM MICHELLE BRANT Subject: RE: Pietenpol-List: Re: strut attachment good catch - forgot about that feature. > Subject: Pietenpol-List: Re: strut attachment > From: tkreiner@gmail.com > Date: Mon=2C 7 Oct 2013 20:25:29 -0700 > To: pietenpol-list@matronics.com > > > If you need to change the position of your wing - and almost EVERYONE nee ds to - in order to correct your cg location=2C you need to use your "B" me thod. > > Hopefully=2C you can visualize the parallelogram that "B" provides=2C whi ch will allow for the cabane struts to be moved fore and back. > > With the sketch shown in "A=2C" what happens is that the front and rear c abanes will be locked into a fixed relationship. What they need is to be f ree to act as hinges in the front / rear swing directions. > > Follow the plans... > > -------- > Tom Kreiner > > > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=410045#410045 > > > > > > > =========== =========== =========== =========== > > > ________________________________ Message 7 _____________________________________ Time: 10:24:37 AM PST US Subject: Pietenpol-List: Need email From: danhelsper@aol.com Can someone give me Malcolm Morrison's email address? Thanks. Dan Helsper Puryear, TN ________________________________ Message 8 _____________________________________ Time: 10:32:19 AM PST US Subject: Re: Pietenpol-List: Need email From: Ken Bickers Dan, this may be what you are looking for: gliderx5@comcast.net. On Tue, Oct 8, 2013 at 11:24 AM, wrote: > Can someone give me Malcolm Morrison's email address? Thanks. > > Dan Helsper > Puryear, TN > > * > > * > > ________________________________ Message 9 _____________________________________ Time: 12:26:08 PM PST US Subject: Pietenpol-List: Re: Mr Sam - Pietenpol N687MB From: "Fun2av8" Weight & Balance (WB) / Datum / Center of Gravity (CG) ====================================== Perhaps I am just having too much fun over thinking this...... I would like to figure this out for my piece of mind. Attached below for N687MB are: W&B Spreadsheet W&B Arm Chart (screen shot) W&B Calculations (screen shot) Snap shots of Page 1 of the 1933 plans that hint that the Datum is actually 7.5 inches ahead of the leading edge. Center of Gravity Can someone figure out where I went wrong in the spreadsheet? The Weight/Arm/Moment table says CG is at 17.7 aft of the datum. The long hand calculations / Percent of Wing Chord says the CG is at 15.2 inches aft of the datum. I can't find the error that is causing the 2.5 inch difference. Datum I read posts that say the Datum is the leading edge of the Wing. My question right now is based on the attached snap shots of my 1933 plans for N687MB. I can find no notes any where on the plans that says that Datum is the LE. However, in the snap shots of page 1 - there is vertical line 7.5" ahead of the LE and a penciled in note that says its 9.5 inches ahead of the LE. Could this line be the Datum? I am hoping someday soon I will be able to talk with Mr. Brusilow, the builder, and ask him. [/u] -------- Jim McWhorter N687MB (New Owner) Culpeper, VA KCJR Read this topic online here: http://forums.matronics.com/viewtopic.php?p=410086#410086 Attachments: http://forums.matronics.com//files/n687mb__1933_plans__main_wheel_cl_aft_of_datum_759.jpg http://forums.matronics.com//files/n687mb__1933_plans__pg_1__datum__386.jpg http://forums.matronics.com//files/n687mb__1933_plans__wing_aft_of_datum_108.jpg http://forums.matronics.com//files/n687mb__1933_plans__ident_box__496.jpg http://forums.matronics.com//files/n687mb_wandb_detailed_calculations_600.png http://forums.matronics.com//files/n687mb_wandb_arm_measurements_345.png http://forums.matronics.com//files/pietenpol_wandb_profile_final_ver_1_679.xls ________________________________ Message 10 ____________________________________ Time: 12:52:53 PM PST US Subject: Pietenpol-List: Re: How straight is straight? From: "Larry Williams" When you come across a question like this it's always reassuring to recall where the original came from. You're worrying about a dimension that probably wouldn't have bothered the original builder in the 30's who was laying out dimensions on a wood floor and using equipment of the era. Don't lower your personal standards but don't get caught up in the mind-set that you can't build an 80 year old design unless you have a CNC machine to cut the pieces. A piet ain't a Saturn 5!![/list] -------- L.V.Williams XCG, XCMR,EPP USHPA, EAA, AMA Read this topic online here: http://forums.matronics.com/viewtopic.php?p=410090#410090 ________________________________ Message 11 ____________________________________ Time: 02:59:10 PM PST US Subject: Pietenpol-List: Re: Mr Sam - Pietenpol N687MB From: "taildrags" Jim; the "mystery vertical line" is, of course, the plane of the firewall. It's a very handy and uniform place from which to measure other things (such as the axle or the wing). It can also be used as the datum for doing your W&B but so can anything else that you choose. Some people use the very front of the prop hub, simply so that all moment arms are measured in the same direction from that point and all moments are clockwise and positive (no subtracting of moments). It is useful to have the wing leading edge as the datum because that's the reference that we typically refer the acceptable range of CG location to, and it's also what most people use. If you keep your + and - signs correct for moment arms that are forward and aft of the datum, the math is pretty simple and it all works out. I have not checked through your calculations to see where things may have gone amiss, but I'll be happy to do so this evening when I have some time. Math errors are common in W&B calculations. -------- Oscar Zuniga Medford, OR Air Camper NX41CC "Scout" A75 power Read this topic online here: http://forums.matronics.com/viewtopic.php?p=410101#410101 ________________________________ Message 12 ____________________________________ Time: 05:01:07 PM PST US Subject: Re: Pietenpol-List: Re: How straight is straight? From: danhelsper@aol.com Which one of these denotes "Top Curmudgeon"? -------- L.V.Williams XCG, XCMR,EPP USHPA, EAA, AMA Dan Helsper Puryear, TN -----Original Message----- From: Larry Williams Sent: Tue, Oct 8, 2013 6:19 pm Subject: Pietenpol-List: Re: How straight is straight? When you come across a question like this it's always reassuring to recall where the original came from. You're worrying about a dimension that probably wou ldn't have bothered the original builder in the 30's who was laying out dimension s on a wood floor and using equipment of the era. Don't lower your personal stan dards but don't get caught up in the mind-set that you can't build an 80 year old design unless you have a CNC machine to cut the pieces. A piet ain't a Satu rn 5!![/list] -------- L.V.Williams XCG, XCMR,EPP USHPA, EAA, AMA Read this topic online here: http://forums.matronics.com/viewtopic.php?p=410090#410090 ________________________________ Message 13 ____________________________________ Time: 05:14:31 PM PST US Subject: Re: Pietenpol-List: Re: Mr Sam - Pietenpol N687MB From: John Weber Hi Jim, Was looking at your figures and one thing I had a question about is your empty weight. Your figures are showing the mains at 176 and 178 and the tailwheel at 20 lbs. This gives an empty weight of 374 lbs. I haven't built a Piet, but have built a Rans S-6 and Rans S-12, so perhaps this could be a "little light"? Would like to see some empty weights from the other builders. Just my $.02 and certainly not throwing any stones. John Weber On Oct 8, 2013, at 3:25 PM, "Fun2av8" wrote: > > Weight & Balance (WB) / Datum / Center of Gravity (CG) > ====================================== > Perhaps I am just having too much fun over thinking this...... I would like to figure this out for my piece of mind. > > Attached below for N687MB are: > W&B Spreadsheet > W&B Arm Chart (screen shot) > W&B Calculations (screen shot) > Snap shots of Page 1 of the 1933 plans that hint that the Datum is actually 7.5 inches ahead of the leading edge. > > Center of Gravity > Can someone figure out where I went wrong in the spreadsheet? The Weight/Arm/Moment table says CG is at 17.7 aft of the datum. The long hand calculations / Percent of Wing Chord says the CG is at 15.2 inches aft of the datum. I can't find the error that is causing the 2.5 inch difference. > > Datum > I read posts that say the Datum is the leading edge of the Wing. My question right now is based on the attached snap shots of my 1933 plans for N687MB. I can find no notes any where on the plans that says that Datum is the LE. > > However, in the snap shots of page 1 - there is vertical line 7.5" ahead of the LE and a penciled in note that says its 9.5 inches ahead of the LE. Could this line be the Datum? > > I am hoping someday soon I will be able to talk with Mr. Brusilow, the builder, and ask him. > > > [/u] > > -------- > Jim McWhorter > N687MB (New Owner) > Culpeper, VA KCJR > > > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=410086#410086 > > > > > Attachments: > > http://forums.matronics.com//files/n687mb__1933_plans__main_wheel_cl_aft_of_datum_759.jpg > http://forums.matronics.com//files/n687mb__1933_plans__pg_1__datum__386.jpg > http://forums.matronics.com//files/n687mb__1933_plans__wing_aft_of_datum_108.jpg > http://forums.matronics.com//files/n687mb__1933_plans__ident_box__496.jpg > http://forums.matronics.com//files/n687mb_wandb_detailed_calculations_600.png > http://forums.matronics.com//files/n687mb_wandb_arm_measurements_345.png > http://forums.matronics.com//files/pietenpol_wandb_profile_final_ver_1_679.xls > > > > > > > ________________________________ Message 14 ____________________________________ Time: 05:45:54 PM PST US Subject: Pietenpol-List: Re: Mr Sam - Pietenpol N687MB From: "Fun2av8" You are absolutely right about the weights . I just took the weights off the sheet provided to me at the time of sale and plugged them in. The light just didnt go off that these were really under stated. I just checked an archive and found that a Piet with the long fuse and an 0-200 should come in at about 775 pounds empty weight. Nice catch. -------- Jim McWhorter N687MB (New Owner) Culpeper, VA KCJR Read this topic online here: http://forums.matronics.com/viewtopic.php?p=410105#410105 ________________________________ Message 15 ____________________________________ Time: 06:02:32 PM PST US Subject: Pietenpol-List: Re: Mr Sam - Pietenpol N687MB From: "Fun2av8" Hi Oscar, Thanks for chiming in. I do understand that the Datum can be anything the builder wants it to be including some point in space beyond the hub - why some would is beyond me. But the FAA W&B book says its possible. Since I didn't build Mr. Sam and at the moment can't get in touch with the builder - what do i do now? The airplane flies fine and probably could just accept that and life goes on. But, I just one of those guys who just has to know for my own piece of mind. Just for fun, I did this crap for flights in my Maule. Hows this for a theoretical approach to the problem. Could one put the Piet on a fulcrum (a heavily padded saw horse) and just find the empty weight balance point and call that the CG point. Then, put in a pilot and a full load of fuel and rebalance the Piet. That would be the approximate aft limit of the CG. Then put in a passenger and once again re-balance the Piet. Could one call that the forward limit of the CG? Then could one measure from the empty weight CG to the Leading edge and call that the Initial datum measurement? From there just re-measure everything. Then, how would one prove this using conventional W&B / CG calculations? Or, maybe I should just go flying ......javascript:emoticon('[Laughing]') taildrags wrote: > Jim; the "mystery vertical line" is, of course, the plane of the firewall. It's a very handy and uniform place from which to measure other things (such as the axle or the wing). It can also be used as the datum for doing your W&B but so can anything else that you choose. Some people use the very front of the prop hub, simply so that all moment arms are measured in the same direction from that point and all moments are clockwise and positive (no subtracting of moments). It is useful to have the wing leading edge as the datum because that's the reference that we typically refer the acceptable range of CG location to, and it's also what most people use. If you keep your + and - signs correct for moment arms that are forward and aft of the datum, the math is pretty simple and it all works out. > > I have not checked through your calculations to see where things may have gone amiss, but I'll be happy to do so this evening when I have some time. Math errors are common in W&B calculations. [Laughing] -------- Jim McWhorter N687MB (New Owner) Culpeper, VA KCJR Read this topic online here: http://forums.matronics.com/viewtopic.php?p=410106#410106 ________________________________ Message 16 ____________________________________ Time: 06:31:53 PM PST US From: Dan Yocum Subject: Re: Pietenpol-List: Re: How straight is straight? On 10/08/2013 02:52 PM, Larry Williams wrote: > > When you come across a question like this it's always reassuring to recall where the original came from. You're worrying about a dimension that probably wouldn't have bothered the original builder in the 30's who was laying out dimensions on a wood floor and using equipment of the era. Don't lower your personal standards but don't get caught up in the mind-set that you can't build an 80 year old design unless you have a CNC machine to cut the pieces. A piet ain't a Saturn 5!![/list] Speaking of the Saturn V, here's one of my favorite cartoons as of late: http://www.xkcd.com/1133/ do not archive > > -------- > L.V.Williams > XCG, XCMR,EPP > USHPA, EAA, AMA > > > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=410090#410090 > > > > > > > > > > ________________________________ Message 17 ____________________________________ Time: 06:40:10 PM PST US Subject: Re: Pietenpol-List: Re: How straight is straight? From: Steven Dortch Larry, your words of wisdom make me feel much better about the precision (not) work I did tonight. At times I far exceed the quality of Mr. Waterman (he made my plane.) at other times I feel like a gorilla with a BFR. Blue Skies, Steve D. On Tue, Oct 8, 2013 at 2:52 PM, Larry Williams wrote: > > When you come across a question like this it's always reassuring to recall > where the original came from. You're worrying about a dimension that > probably wouldn't have bothered the original builder in the 30's who was > laying out dimensions on a wood floor and using equipment of the era. Don't > lower your personal standards but don't get caught up in the mind-set that > you can't build an 80 year old design unless you have a CNC machine to cut > the pieces. A piet ain't a Saturn 5!![/list] > > -------- > L.V.Williams > XCG, XCMR,EPP > USHPA, EAA, AMA > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=410090#410090 > > ________________________________ Message 18 ____________________________________ Time: 07:00:44 PM PST US Subject: Re: Pietenpol-List: Re: Mr Sam - Pietenpol N687MB From: Steven Dortch For my "real" plane I carry several example W&Bs with me. Then I can simply reference them Probably not as important on Most Piets, but perhaps for some. Examples I would do are. Tanks full, Pilot only. Main (front) tank full, Pilot only. Aux tank full. Pilot only. Tanks empty Pilot only. Tanks full, pilot and front Pax. Front tank, pilot and pax Tanks empty pilot and front Pax. I would also figure out how where you go past the aft CG. IE with the front tank empty how big can the back seater be? Where do you go past Forward CG? How skinny can the pilot be with the front tank full? Don't forget, If you carry a full craftsman took kitl in the box behind your rear seat it should be included, As well as the full set of Clydesdale horseshoes you carry in the custom storage bag hung under the engine. Once you have figured out these calculations you will have a very good feel for what (and who) you can carry. Y'all be careful out there. Steve D Far Forward CG and the plane gets more twitchy, far back CG and the plane responds sluggishly. On Tue, Oct 8, 2013 at 4:58 PM, taildrags wrote: > > Jim; the "mystery vertical line" is, of course, the plane of the firewall. > It's a very handy and uniform place from which to measure other things > (such as the axle or the wing). It can also be used as the datum for doing > your W&B but so can anything else that you choose. Some people use the > very front of the prop hub, simply so that all moment arms are measured in > the same direction from that point and all moments are clockwise and > positive (no subtracting of moments). It is useful to have the wing > leading edge as the datum because that's the reference that we typically > refer the acceptable range of CG location to, and it's also what most > people use. If you keep your + and - signs correct for moment arms that > are forward and aft of the datum, the math is pretty simple and it all > works out. > > I have not checked through your calculations to see where things may have > gone amiss, but I'll be happy to do so this evening when I have some time. > Math errors are common in W&B calculations. > > -------- > Oscar Zuniga > Medford, OR > Air Camper NX41CC "Scout" > A75 power > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=410101#410101 > > ________________________________ Message 19 ____________________________________ Time: 09:04:05 PM PST US Subject: Pietenpol-List: Re: Mr Sam - Pietenpol N687MB From: "taildrags" Jim; Do you keep your plane in a hangar? If so, this can be pretty easy and you won't be in any hurry to get it done. Since the airplane is flying, you don't have to worry about getting it done any certain time and you can do it in two sessions. You could probably do it all yourself, but it's far easier with two people. In one session you'll be measuring things and in the second session you'll be weighing the airplane. Get some tape (painter's tape is fine and it comes off your hangar floor easily, but anything else will do), plus a length of nice strong twine and a plumb bob or anything heavy that you can tie to the end of the twine. A point on the end of it just helps you get closer on your measurements but it can be a big lag bolt or anything similar if you don't have a plumb bob. Get a Sharpie to mark on the tape, plus a piece of paper and pencil to write down your measurements. Then get a steel measuring tape that's at least 20 or 25 ft. long and you're ready. With the airplane out of the hangar (or in it... doesn't matter but it's easier to do if you don't have to crawl around under the airplane), lay a straight stripe of tape on the floor, in line with the nose and tail of the airplane and close to where you usually park the airplane and you know the wings and tail will clear everything. Next, lay a second stripe of tape across the first to form a cross, and try to get it so it falls more or less where your tires will sit when you roll the plane in to line up with the first stripe. Before you roll the plane in though, check to make sure the second stripe is at right angles to the first. You can do this a number of ways but you have twine and a measuring tape, so you can always just pick a number (like 4 ft.) and make a mark on each tape stripe that distance away from where they cross. Then measure the distances diagonally between the marks to make sure they are the same. Pick up the cross tape and adjust it if need be to get it square to the other stripe. Now roll the airplane in, lining it up on the long stripe. Guide the tailwheel down the stripe till the mains roll right onto the cross stripe. You may need to roll it back and forth a bit till the tailwheel is on the stripe and a plumb line dropped from the propeller hub drops right onto the tape. If the main axles are also right over the cross stripe, chock the mains and you're ready to start measuring. There are a lot of interesting measurements that you can take with this setup that don't have much to do with weight and balance, but they can be useful at other times. I won't worry with those now. You'll need a sawhorse or ladder, or you could also use a rope or hoist slung from your hangar roof, but you've got to raise the tail till the fuselage is in the straight and level position. A rope and pulley could be the best way to do this, but blocking up the tail with boxes or a sawhorse can do it too, as long as you can get the fuselage level and steady, and as long as you can drop a plumb line from the center of the tailwheel to the floor. Setting the tailwheel up on a stand won't usually let you do this. And watch it when you're raising the tail, since some aircraft get a little light on the tail in the level attitude, and can go on their nose if you overshoot. Get an accurate level and put it on the straightest section of fuselage longeron that you have easy access to. Usually that will be right inside the rear cockpit, the top longerons. A bubble level will do, but if you have one of those "angle finder" gizmos or a digital level, that's best. If you do it carefully and slowly, you'll only ever have to do this once. Airplane is level. Axles are directly over the cross tape, nose and tailwheel are directly over the longitudinal tape. Wheels are chocked. Now it's just a matter of taking your plumb line and measuring tape and getting the important measurements. The biggie is that leading edge, since it's your datum. Pick a side of the airplane that you want to work on and you can take all the measurements on that side. It doesn't matter which. Let the plumb line drape over the wing so the plumb bob goes down to the floor from the leading edge. Let the plumb bob stop swinging, then put down a piece of tape with a nice clear mark right where the plumb bob points. Now you can measure anything you want or need. Drop a line from the face of the firewall and measure aft to the leading edge. Measure from the leading edge mark back to the line that the landing gear make. Drop your plumb line from the center of the tailwheel and measure from the landing gear tape back to where the tailwheel plumb bob drops. And, as long as you've got everything set up, you can measure from the face of the prop hub to the firewall, you can measure the track (distance between contact patches of the two mains, you can measure from the firewall to the tailpost to determine which of the various Air Camper fuselage lengths you have, you can put your angle finder on the wing cabanes and determine if they are inclined and if so, by how much (usually measured at the top where the cabanes attach to the underside of the wing, and measured in inches aft of vertical). With these measurements, you can determine all the other moment arms once you do the weighing because you have determined the locations of the three weighing points and their positions relative to the leading edge, which is the datum. All of the laying out and measuring can be done in about an hour, if you have help and have the few simple tools that are needed. The weighing is next, and you could move right on to it if you have the scales available. With some prior planning, you could also do the whole thing in one process by setting the airplane up on the scales and doing the weighing and measuring all at one shot. Let's say you're doing it in two phases, so now the tape and marks are all off your hangar floor and you're not measuring anything this time... only reading scales. You'll want to pick a day when it's not too windy. You'd be surprised what even a breeze or gust will do to the reading on a digital scale when it flows around an airplane. So, get the best scales you have available but even if you decide to go with digital bathroom scales, at least make the two that you use on the mains identical. they have to go up to at least about 400 pounds. The one for the tailwheel can be smaller, but if all three are identical, even better. I used digital electronic race car scales for weighing my airplane, but Mr. Pietenpol very likely didn't have any of those and his airplanes flew just fine. Roll the mains onto two of the scales using ramps. Easier with two people. Raise the tail to the level position again, but this time you can use a small table, tool chest, or other stable platform to put the tailwheel right on the scale with the fuselage leveled using your angle finder or level to get it nice and level. In the best case, you will have drained all fuel out of the airplane so you get an empty weight. You can fool with draining the gascolator, but it's not a big deal. I would weigh it with the normal operating level of oil in the engine and make note of that. Make sure you've taken handheld radio, water bottle, knee board, headsets, spare parts and tools, fuzzy dice, and any other loose items out of the cockpits and stowage areas. Remember, it's "basic EMPTY weight". Read the scales and record the weights. Left main, right main, tailwheel. Those are important numbers and they should be something like in the 300s for the mains and less than 30 for the tail. Now to determine the moment arms for fuel, passenger, and pilot. I'll describe the situation for a fuel tank in the nose. With the airplane still level and on the scales, take a KNOWN quantity of fuel, something reasonable like 5 or 6 gallons, and pour all of it into the fuel tank. Replace the tank cap. Read all three scales again and write down the numbers. Later, you can go back and reverse-calculate the fuel moment arms by knowing those three weights and the amount of weight of fuel that you added. You will then know the fuel moment arm, which should never change unless you make changes in the tank location. To determine the passenger and pilot moment arms, find a volunteer and get their weight. Don't let them guess at their weight... have them weigh themselves either before you use the scales for the plane weighing, or on another set of scales. Have them climb into each cockpit slowly and carefully, make sure nothing moves on the scales, and record the weights in both configurations. Again, later on you can reverse-calculate the moment arm distances for passenger and pilot if you know what the person's weight was and what the new readings are on your scales. You're done in the hangar. Probably another hour to do the weighing, but if you did it carefully and remembered to record all the numbers, you'll never have to do it again. You can do all of the above on a rainy or wintry day when you don't have anything else to do, and of course you can work out the formulas and W&B diagrams later on when you're at home and comfortable. That should do it. No mystery vertical lines, and everything you have will be useful at one time or another. I probably missed something along the line, but I'm sure someone will chime in if I have. -------- Oscar Zuniga Medford, OR Air Camper NX41CC "Scout" A75 power Read this topic online here: http://forums.matronics.com/viewtopic.php?p=410118#410118 ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message pietenpol-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/Pietenpol-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/pietenpol-list Browse Digests http://www.matronics.com/digest/pietenpol-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.