---------------------------------------------------------- Pietenpol-List Digest Archive --- Total Messages Posted Wed 06/12/13: 12 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 05:59 AM - Re: Tippiness (Gary Boothe) 2. 05:59 AM - Re: Tippiness (Gary Boothe) 3. 02:55 PM - Re: Attaching ribs to spars question (John Francis) 4. 03:01 PM - Re: Re: Attaching ribs to spars question (Gary Boothe) 5. 03:14 PM - Re: Re: Attaching ribs to spars question (Gary Boothe) 6. 03:36 PM - Re: Re: Attaching ribs to spars question (Lion Mason) 7. 03:36 PM - Re: Attaching ribs to spars question (John Francis) 8. 03:51 PM - Re: Re: Attaching ribs to spars question (Gary Boothe) 9. 06:36 PM - Re: Tippiness (jarheadpilot82) 10. 07:43 PM - Re: Tippiness (tools) 11. 09:29 PM - Re: Re: Tippiness (Ken Bickers) 12. 10:58 PM - Re: Tippiness (jarheadpilot82) ________________________________ Message 1 _____________________________________ Time: 05:59:18 AM PST US From: "Gary Boothe" Subject: RE: Pietenpol-List: Tippiness Nicely done, Ken. I live on 'precise estimates!' J Gary Boothe NX308MB From: owner-pietenpol-list-server@matronics.com [mailto:owner-pietenpol-list-server@matronics.com] On Behalf Of Ken Bickers Sent: Tuesday, June 11, 2013 10:54 AM Subject: Pietenpol-List: Tippiness Guys, This past weekend, I was discussing the question of potential tippiness of parasol winged airplanes with a flying buddy of mine who happens to be a physicist at the University of Colorado. The question I posed was how could we estimate the location of the center of gravity in the vertical dimension, based on doing weight and balance calculations. Knowing that location would allow for precise estimates of the relative tippiness of different airplanes. He thought this would make a great homework question for his undergraduates. He sent me the solution, which I've attached for you. To do the math, you'll need to do weight and balance measurements with the fuselage in at least two different orientations. The easiest would be one while the plane rests on the landing gear and one with the tail elevated to make the top longeron level with the ground. Key here is that you'll need to measure the change in angle at the top longeron, using an angle finder that you can buy at any hardware store. After that you just need to plug values into a calculator that can take sines and cosines using the formula that is in the attached document. The one you want is the one marked (4). One more thing. I'd suggest loading the cockpits and fuel tank with normal weights that would be seen on takeoff or landing, as this will affect the vertical center of gravity just as surely as it will affect the longitudinal center of gravity in any standard weight and balance calculation. Cheers, Ken ________________________________ Message 2 _____________________________________ Time: 05:59:19 AM PST US From: "Gary Boothe" Subject: RE: Pietenpol-List: Tippiness Nicely done, Ken. I live on 'precise estimates!' J Gary Boothe NX308MB From: owner-pietenpol-list-server@matronics.com [mailto:owner-pietenpol-list-server@matronics.com] On Behalf Of Ken Bickers Sent: Tuesday, June 11, 2013 10:54 AM Subject: Pietenpol-List: Tippiness Guys, This past weekend, I was discussing the question of potential tippiness of parasol winged airplanes with a flying buddy of mine who happens to be a physicist at the University of Colorado. The question I posed was how could we estimate the location of the center of gravity in the vertical dimension, based on doing weight and balance calculations. Knowing that location would allow for precise estimates of the relative tippiness of different airplanes. He thought this would make a great homework question for his undergraduates. He sent me the solution, which I've attached for you. To do the math, you'll need to do weight and balance measurements with the fuselage in at least two different orientations. The easiest would be one while the plane rests on the landing gear and one with the tail elevated to make the top longeron level with the ground. Key here is that you'll need to measure the change in angle at the top longeron, using an angle finder that you can buy at any hardware store. After that you just need to plug values into a calculator that can take sines and cosines using the formula that is in the attached document. The one you want is the one marked (4). One more thing. I'd suggest loading the cockpits and fuel tank with normal weights that would be seen on takeoff or landing, as this will affect the vertical center of gravity just as surely as it will affect the longitudinal center of gravity in any standard weight and balance calculation. Cheers, Ken ________________________________ Message 3 _____________________________________ Time: 02:55:05 PM PST US Subject: Pietenpol-List: Re: Attaching ribs to spars question From: "John Francis" [quote="gboothe"]Once covered and stitched, those ribs ain't goin' nowhere! My spar replace project got infinitely easier without glued ribs!! Gary, But maybe that spar wouldn't of broken if the ribs were glued to it??? Just saying..... -------- John Francis Read this topic online here: http://forums.matronics.com/viewtopic.php?p=402568#402568 ________________________________ Message 4 _____________________________________ Time: 03:01:48 PM PST US Subject: Re: Pietenpol-List: Re: Attaching ribs to spars question From: Gary Boothe Don't see how they would add any strength. They did not move, and they did not break. I don't know, but I think slapping 1,000 lbs of aircraft down on one spar was the culprit! ;-) Gary Sent from my iPhone On Jun 12, 2013, at 2:54 PM, "John Francis" wrote: > > [quote="gboothe"]Once covered and stitched, those ribs ain't goin' nowhere! My spar replace project got infinitely easier without glued ribs!! > > Gary, > > But maybe that spar wouldn't of broken if the ribs were glued to it??? > Just saying..... > > -------- > John Francis > > > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=402568#402568 > > > > > > > > > > ________________________________ Message 5 _____________________________________ Time: 03:14:25 PM PST US Subject: Re: Pietenpol-List: Re: Attaching ribs to spars question From: Gary Boothe That came out a little harsh...sorry John! What I really mean to say is that, after completing and flying my plane, I am amazed by how little I know. If someone can explain how fastening the ribs to the spar will increase strength...I'm all ears! Gary Sent from my iPhone On Jun 12, 2013, at 3:01 PM, Gary Boothe wrote: > > Don't see how they would add any strength. They did not move, and they did not break. I don't know, but I think slapping 1,000 lbs of aircraft down on one spar was the culprit! ;-) > > Gary > > Sent from my iPhone > > On Jun 12, 2013, at 2:54 PM, "John Francis" wrote: > >> >> [quote="gboothe"]Once covered and stitched, those ribs ain't goin' nowhere! My spar replace project got infinitely easier without glued ribs!! >> >> Gary, >> >> But maybe that spar wouldn't of broken if the ribs were glued to it??? >> Just saying..... >> >> -------- >> John Francis >> >> >> >> >> Read this topic online here: >> >> http://forums.matronics.com/viewtopic.php?p=402568#402568 > > > > > ________________________________ Message 6 _____________________________________ Time: 03:36:03 PM PST US Subject: Re: Pietenpol-List: Re: Attaching ribs to spars question From: Lion Mason I thought that's what rib lacing is for . Gardiner Sent from my iPhone On Jun 12, 2013, at 6:14 PM, Gary Boothe wrote: > > That came out a little harsh...sorry John! > > What I really mean to say is that, after completing and flying my plane, I am amazed by how little I know. If someone can explain how fastening the ribs to the spar will increase strength...I'm all ears! > > Gary > > Sent from my iPhone > > On Jun 12, 2013, at 3:01 PM, Gary Boothe wrote: > >> >> Don't see how they would add any strength. They did not move, and they did not break. I don't know, but I think slapping 1,000 lbs of aircraft down on one spar was the culprit! ;-) >> >> Gary >> >> Sent from my iPhone >> >> On Jun 12, 2013, at 2:54 PM, "John Francis" wrote: >> >>> >>> [quote="gboothe"]Once covered and stitched, those ribs ain't goin' nowhere! My spar replace project got infinitely easier without glued ribs!! >>> >>> Gary, >>> >>> But maybe that spar wouldn't of broken if the ribs were glued to it??? >>> Just saying..... >>> >>> -------- >>> John Francis >>> >>> >>> >>> >>> Read this topic online here: >>> >>> http://forums.matronics.com/viewtopic.php?p=402568#402568 > > > > > ________________________________ Message 7 _____________________________________ Time: 03:36:37 PM PST US Subject: Pietenpol-List: Re: Attaching ribs to spars question From: "John Francis" Gary, I really have no idea what I'm talking about. How's the rebuild going? -------- John Francis Read this topic online here: http://forums.matronics.com/viewtopic.php?p=402572#402572 ________________________________ Message 8 _____________________________________ Time: 03:51:42 PM PST US Subject: Re: Pietenpol-List: Re: Attaching ribs to spars question From: Gary Boothe Slowly. We had just moved, and my wife thinks that un-packing is more important than fixing airplanes....haven't come up with a good argument! So far, just got the fabric off... Gary Sent from my iPhone On Jun 12, 2013, at 3:36 PM, "John Francis" wrote: > > Gary, I really have no idea what I'm talking about. How's the rebuild going? > > -------- > John Francis > > > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=402572#402572 > > > > > > > > > > ________________________________ Message 9 _____________________________________ Time: 06:36:28 PM PST US Subject: Pietenpol-List: Re: Tippiness From: "jarheadpilot82" Ken, I have only briefly looked at your attachment. My question is this- based on the formulas you have provided, how will that influence/affect my build? I am familiar with the concept of a lateral CG when flying helicopters. What do I do to make this vertical CG a part of my project? I am just not sure I see the significance. Thanks for your help on this. -------- Semper Fi, Terry Hand Athens, GA Read this topic online here: http://forums.matronics.com/viewtopic.php?p=402583#402583 ________________________________ Message 10 ____________________________________ Time: 07:43:41 PM PST US Subject: Pietenpol-List: Re: Tippiness From: "tools" I was wondering at first too, but came up with this... I imagine nearly ALL our planes will have similar vert cg locations with respect to, say, the top longeron. However, the distance of the vert cg to the ground... is going to be quite different. I suspect what that will tell us is, you're best to keep the location of the vert CG near where it was originally. OR, if it's gonna be much higher, you might be better off with a stiffer than average suspension to help maintain control. I'm now starting to understand rigid gear like a Fly Baby. Probably makes it a bit tamer on the gear, not necessarily GETTING it on the gear. Seems EVERYTHING has its compromises. Quick caveat. MANY of our planes have the wing raised a bit. THAT is gonna change the vert cg really fast, which will affect ground handling. Read this topic online here: http://forums.matronics.com/viewtopic.php?p=402585#402585 ________________________________ Message 11 ____________________________________ Time: 09:29:54 PM PST US Subject: Re: Pietenpol-List: Re: Tippiness From: Ken Bickers Terry, The formulas may or may not be of use to you in building your plane. I was prompted to see if there was a way to identify the CG in the vertical dimension by the article on Pazmany's thoughts on landing gear design posted by Chris Tracy on June 6th (re-attached here). Maybe it would be more accurate to say that I was prompted by Gary's incident dragging a wing tip. One of the key variables in the design of landing gears is the location of the CG vertically. It affects both how far forward or aft to place the gear (especially on tail wheel airplanes) and how wide to make the wheel base. As all of us make decisions about where to locate fuel tanks (nose or center section or both), lengthening cabane struts, sticking to the wheel base called out in the original plans or widening the wheel base, extending the motor mount, etc., it is useful to be able to think through the implications of those decisions. Having the ability to run through different scenarios using the formula that I forwarded, along with the Pazmany formulas Chris provided, might lead to better decisions. Or it might allow for some diagnostics after the fact to figure out why a particular airplane behaved in a particular way. Personally, I enjoy stuff like this. For others, mileage may vary. Cheers, Ken On Wed, Jun 12, 2013 at 7:36 PM, jarheadpilot82 wrote: > jarheadpilot82@hotmail.com> > > Ken, > > I have only briefly looked at your attachment. My question is this- based > on the formulas you have provided, how will that influence/affect my build? > > I am familiar with the concept of a lateral CG when flying helicopters. > What do I do to make this vertical CG a part of my project? I am just not > sure I see the significance. > > Thanks for your help on this. > > -------- > Semper Fi, > > Terry Hand > Athens, GA > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=402583#402583 > > ________________________________ Message 12 ____________________________________ Time: 10:58:57 PM PST US Subject: Pietenpol-List: Re: Tippiness From: "jarheadpilot82" Ken, Thanks for uploading the Forum paper about landing gear design. The last paragraph on page 1 gave me what I was looking for- "On a front view, the angle between vertical and a line from CG to point of wheel contact with ground should not be less than 25 degrees." That is what I was looking for. With so many differing dimensions of gear width that have been mentioned, I agree that some guidance needs to be published, and this article gives it. My question pertained to the usefulness of the information, and this article does put it to use. Thanks for bringing that out. I guess the Grumman engineers slept through the landing gear design class in college when they designed the gear on the F4F Wildcat! -------- Semper Fi, Terry Hand Athens, GA Read this topic online here: http://forums.matronics.com/viewtopic.php?p=402593#402593 Attachments: http://forums.matronics.com//files/f4f_4a_145.jpg ------------------------------------------------------------------------------------- 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.