Pietenpol-List Digest Archive

Tue 05/06/14


Total Messages Posted: 14



Today's Message Index:
----------------------
 
     1. 05:07 AM - 3 Piece Wing Question (GrantZ)
     2. 05:51 AM - Re: 3 Piece Wing Question (Jack Phillips)
     3. 08:00 AM - Re: 3 Piece Wing Question (AircamperN11MS)
     4. 11:39 AM - Re: 3 Piece Wing Question (Cuy, Michael D. (GRC-RXD0)[Vantage Partners, LLC])
     5. 12:14 PM - Re: 3 Piece Wing Question (Steven Dortch)
     6. 12:25 PM - Re: 3 Piece Wing Question (Ken Bickers)
     7. 12:29 PM - Re: 3 Piece Wing Question (Boatright, Jeffrey)
     8. 01:19 PM - Re: 3 Piece Wing Question (Cuy, Michael D. (GRC-RXD0)[Vantage Partners, LLC])
     9. 01:33 PM - Re: 3 Piece Wing Question (Jack Phillips)
    10. 01:42 PM - Re: 3 Piece Wing Question (Cuy, Michael D. (GRC-RXD0)[Vantage Partners, LLC])
    11. 01:51 PM - Re: progress on Scout (taildrags)
    12. 07:27 PM - Re: Re: progress on Scout (Gary Boothe)
    13. 07:57 PM - Re: 3 Piece Wing Question (Clif Dawson)
    14. 08:56 PM - Re: 3 Piece Wing Question (taildrags)
 
 
 


Message 1


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    Time: 05:07:19 AM PST US
    Subject: 3 Piece Wing Question
    From: "GrantZ" <grantz5906@aol.com>
    Tail feathers completed. Basic fuselage frame-up completed. 15 ribs done. Learning to TIG weld all over again! Starting wing construction. 3 piece plans state that the center section and outer panel spar ends butt together with "0 clearance at assembly. How does one cut the spar ends accurately enough to achieve this and not introduce any dihedral or anhedral when assembled (i.e. flat panel from tip to tip)? Can shims be used at final assembly to get proper alignment? Does the lack of any fitting holding the upper edges of the spars together bother anyone but me? Lots of these craft are flying with 3 piece wings built to the plans but it just to seems odd to me that the only thing keeping the spars butted together is lift force and any preload provided by the lift strut. What am I missing here? Grant Ziebell Savannah, TN Read this topic online here: http://forums.matronics.com/viewtopic.php?p=422879#422879


    Message 2


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    Time: 05:51:50 AM PST US
    From: "Jack Phillips" <jack@bedfordlandings.com>
    Subject: 3 Piece Wing Question
    Grant, Don't worry about it. The spars need to butt together to carry the considerable compressive load between the main spars and the centersection spar. Since the lift struts attach at the center of the wing panels, virtually all of the lift load is carried by the lift struts. However, since they attach at about a 30=C2=B0 angle, if each lift strut is carrying 500 lbs of lift (vertical component) the tensile load carried by the lift strut on each side is 1000 lbs down the line of the strut, which means the lift strut is pulling the wing horizontally (towards the centersection) with a tensile force of 866 lbs. This is the compressive force between the wing spars and the centersection spars. By letting the spars butt together, the whole cross-sectional area of the spar is available to help carry this load. If you are using =C2=BE=9D spars 4-3/4=9D tall, the area is 3.56 sq inches, so the compressive stress is 866/3.56 or 243 psi, which spruce can easily carry. If you put a bolted fitting there to carry this load, you are now reducing the area to carry it to the width of the spar x the diameter of the bolt. Assuming you use a 5/16=9D bolt, this area is .23 sq inches, and the compressive stress induced in the wood is now 866/.23 or 3,694 psi, which is getting pretty close to the limit for spruce (spruce can carry 4200 psi compressive stress parallel to the grain, according to the tables found in http://www.recreationalflying.com/tutorials/scratchbuilder/wood_strength_ values.html . As for adding dihedral, unless you are wanting significant dihedral, you can just flex the wing enough to add up to a degree or two. I have about =C2=BD degree of dihedral per side on mine =93 just enough to avoid the illusion of drooping wings (if such an illusion actually exists) that some say a perfectly straight wing causes. Besides, having just one attach bolt per spar makes it MUCH easier to attach and remove the wing panels, rather than having to line up four bolts simultaneously. With just one bolt per spar, the wingtip can actually be left on the ground and the spars attached, before lifting the wing and attaching the lift struts. As has often been said before on this site: =9CBuild it to the plans=9D. Good Luck! Jack Phillips NX899JP Smith Mountain Lake, Virginia -----Original Message----- From: owner-pietenpol-list-server@matronics.com [mailto:owner-pietenpol-list-server@matronics.com] On Behalf Of GrantZ Sent: Tuesday, May 06, 2014 8:07 AM Subject: Pietenpol-List: 3 Piece Wing Question Tail feathers completed. Basic fuselage frame-up completed. 15 ribs done. Learning to TIG weld all over again! Starting wing construction. 3 piece plans state that the center section and outer panel spar ends butt together with "0 clearance at assembly=C3=A2=82=AC=C5=93. How does one cut the spar ends accurately enough to achieve this and not introduce any dihedral or anhedral when assembled (i.e. flat panel from tip to tip)? Can shims be used at final assembly to get proper alignment? Does the lack of any fitting holding the upper edges of the spars together bother anyone but me? Lots of these craft are flying with 3 piece wings built to the plans but it just to seems odd to me that the only thing keeping the spars butted together is lift force and any preload provided by the lift strut. What am I missing here? Grant Ziebell Savannah, TN Read this topic online here: http://forums.matronics.com/viewtopic.php?p=422879#422879


    Message 3


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    Time: 08:00:10 AM PST US
    Subject: Re: 3 Piece Wing Question
    From: "AircamperN11MS" <Scott.liefeld@lacity.org>
    Fantastic answer to his question. The only thing I can add is that (as far as I know) that there has NEVER been an in flight structural failure of a Pietenpol. Just build it to the plans and feel very safe in it during all phases of flight. Happy landings, -------- Scott Liefeld Flying N11MS since March 1972 Steel Tube C-85-12 Wire Wheels Brodhead in 1996 Read this topic online here: http://forums.matronics.com/viewtopic.php?p=422887#422887


    Message 4


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    Time: 11:39:32 AM PST US
    From: "Cuy, Michael D. (GRC-RXD0)[Vantage Partners, LLC]" <michael.d.cuy@nasa.gov>
    Subject: 3 Piece Wing Question
    Grant, My center section spars and L & R wing panel spar ends do not butt up again st each other. I respect Jack Phillips mechanical load analysis as he is a professional mechanical/aerotype engineer but when I made up my center section spar ends I intentionally cut a small angle inward at the top on each of them so I could pivot the outer wing panels upward just a little because I wanted dihedral. I would doubt that very few Pietenpols with 3 -piece wings have really good and full contact between the CC butt spar end s and the outer wing panel spar ends so I assume (after flying mine for the past 16 years) that the metal f ittings and bolts which join the CC and wing panels together is sufficient to take the loads given that I know for a fact my spar ends are not flush against each other. Mike C. Ohio


    Message 5


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    Time: 12:14:23 PM PST US
    Subject: Re: 3 Piece Wing Question
    From: Steven Dortch <steven.d.dortch@gmail.com>
    Mike your plane must be unairworthy. Please box it up and ship it to me and I will deal with disposal. ;+} Blue Skies, Steve D


    Message 6


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    Time: 12:25:13 PM PST US
    Subject: Re: 3 Piece Wing Question
    From: Ken Bickers <bickers.ken@gmail.com>
    I fear the repercussions when the Top Curmudgeon and associated Council of Curmudgeons get wind of MC's deviation from the plans. The masses will certainly be disconcerted. On Tue, May 6, 2014 at 1:13 PM, Steven Dortch <steven.d.dortch@gmail.com>wrote: > > Mike your plane must be unairworthy. Please box it up and ship it to me > and I will deal with disposal. ;+} > > Blue Skies, > Steve D > > > * > > > * > >


    Message 7


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    Time: 12:29:12 PM PST US
    From: "Boatright, Jeffrey" <jeffboatright@emory.edu>
    Subject: Re: 3 Piece Wing Question
    I=92ll do you one better. My spar ends are at least an inch apart from one another. I=92m out of town and so cannot send photos, but my spars have met al straps that extend several inches down the length of the spars, with bol ts through the spars and straps. At the spar ends, the straps extend about an inch and go from a rectangle to a triangle. The tips of the triangles ov erlap and a bolt runs through that overlap. Sort of like this: =97=97=97=97 =97=97=97=97 Center \ / Wing =97> Section / \ =97=97=97=97 =97=97=97=97 Don=92t know if it=92s safe, but the plane has been flying that way since 1 978. -- Jeffrey H. Boatright, PhD, FARVO Professor of Ophthalmology Emory University School of Medicine From: <Cuy>, "LLC]" <michael.d.cuy@nasa.gov<mailto:michael.d.cuy@nasa.gov>> >" <pietenpol-list@matronics.com<mailto:pietenpol-list@matronics.com>> etenpol-list@matronics.com<mailto:pietenpol-list@matronics.com>> Subject: RE: Pietenpol-List: 3 Piece Wing Question Grant, My center section spars and L & R wing panel spar ends do not butt up again st each other. I respect Jack Phillips mechanical load analysis as he is a professional mechanical/aerotype engineer but when I made up my center section spar ends I intentionally cut a small angle inward at the top on each of them so I could pivot the outer wing panels upward just a little because I wanted dihedral. I would doubt that very few Pietenpols with 3 -piece wings have really good and full contact between the CC butt spar end s and the outer wing panel spar ends so I assume (after flying mine for the past 16 years) that the metal f ittings and bolts which join the CC and wing panels together is sufficient to take the loads given that I know for a fact my spar ends are not flush against each other. Mike C. Ohio ________________________________ This e-mail message (including any attachments) is for the sole use of the intended recipient(s) and may contain confidential and privileged information. If the reader of this message is not the intended recipient, you are hereby notified that any dissemination, distribution or copying of this message (including any attachments) is strictly prohibited. If you have received this message in error, please contact the sender by reply e-mail message and destroy all copies of the original message (including attachments).


    Message 8


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    Time: 01:19:55 PM PST US
    From: "Cuy, Michael D. (GRC-RXD0)[Vantage Partners, LLC]" <michael.d.cuy@nasa.gov>
    Subject: 3 Piece Wing Question
    I know of Piet spars (one on a flying Scout) that have notches dug into the m in order for the wing strut attach 'straddle' fitting to go low enough so the bottom of the fitting fit thru the fabric of the lower wing e nough to bolt on the four lift struts........I've seen others that have Piet spars with a cut in them for various other reasons as well. Now this 1" gap Jeff Boatright.....I'm jealous. My gap is only about a =BC " between butt spar ends and wing panel spar ends. And yours has been flying since 1978? Nice! Mike C. Ohio


    Message 9


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    Time: 01:33:58 PM PST US
    From: "Jack Phillips" <jack@bedfordlandings.com>
    Subject: 3 Piece Wing Question
    You and Jeff Boatright have apparently cheated death every time you have flown! Obviously, the strap type fittings spread the loads sufficiently through the wood of the spar to lower the stress to safe levels. The numbers I ran this morning assumed that the top fitting would just be a bolt through the spar, which would be marginal at best. My point to Grant was that if built to the plans, the spar is as strong with just one bolt securing it as it needs to be, and no extra concerns are necessary to add a slight amount of dihedral or washout ' just do it with the lift struts. Jack Phillips NX899JP Smith Mountain Lake, Virginia _____ From: owner-pietenpol-list-server@matronics.com [mailto:owner-pietenpol-list-server@matronics.com] On Behalf Of Cuy, Michael D. (GRC-RXD0)[Vantage Partners, LLC] Sent: Tuesday, May 06, 2014 4:19 PM Subject: RE: Pietenpol-List: 3 Piece Wing Question I know of Piet spars (one on a flying Scout) that have notches dug into them in order for the wing strut attach =91straddle=92 fitting to go low enough so the bottom of the fitting fit thru the fabric of the lower wing enough to bolt on the four lift struts=85=85..I=92ve seen others that have Piet spars with a cut in them for various other reasons as well. Now this 1=94 gap Jeff Boatright=85..I=92m jealous. My gap is only about a =BC=94 between butt spar ends and wing panel spar ends. And yours has been flying since 1978? Nice! Mike C. Ohio


    Message 10


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    Time: 01:42:46 PM PST US
    From: "Cuy, Michael D. (GRC-RXD0)[Vantage Partners, LLC]" <michael.d.cuy@nasa.gov>
    Subject: 3 Piece Wing Question
    You and Jeff Boatright have apparently cheated death every time you have fl own! That is such a true statement, at least for me, Jack and it has nothing to do with my wing spars.....just my nature as a pilot sometimes! Looks like I picked a bad week to stop amphetamines. McCrosky: 'Johnny, how bout some coffee?' Johnny: 'no thanks.' Rapunzel, the Tower, the Tower!!! [cid:image001.jpg@01CF694A.2A9EA490]


    Message 11


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    Time: 01:51:51 PM PST US
    Subject: Re: progress on Scout
    From: "taildrags" <taildrags@hotmail.com>
    So I got over to the hangar for just a few minutes today and pulled the airplane out into the sun. Tied down the tail, turned on the fuel, and pulled the engine through four blades. Made the mags hot and then propped it off with gusto. It fired on about the 4th arm, which isn't bad considering the carb has just been overhauled and fuel had to make its way into all the passageways and ports. Warmed it up and then hesitatingly applied throttle to see if it was going to gag and cough without pulling carb heat. It did not. Power ran up, ran down, and idle is smooth. I shut it down and will play with it some more this weekend, but it appears to be ready to put the cowling back on and resume taxi testing. If all goes well, I should get some air under the wings on Saturday. Oh, yeah, and a quick check of the new main seal confirmed that it's bone dry, so hopefully no more oil mist after the oil gets good and hot and thin. I'll find out after I can fly it for at least a few circuits of the field. -------- Oscar Zuniga Medford, OR Air Camper NX41CC &quot;Scout&quot; A75 power Read this topic online here: http://forums.matronics.com/viewtopic.php?p=422922#422922


    Message 12


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    Time: 07:27:22 PM PST US
    From: "Gary Boothe" <gboothe5@comcast.net>
    Subject: Re: progress on Scout
    Well done, Oscar! Gary Boothe NX308MB -----Original Message----- From: owner-pietenpol-list-server@matronics.com [mailto:owner-pietenpol-list-server@matronics.com] On Behalf Of taildrags Sent: Tuesday, May 06, 2014 1:52 PM Subject: Pietenpol-List: Re: progress on Scout --> <taildrags@hotmail.com> So I got over to the hangar for just a few minutes today and pulled the airplane out into the sun. Tied down the tail, turned on the fuel, and pulled the engine through four blades. Made the mags hot and then propped it off with gusto. It fired on about the 4th arm, which isn't bad considering the carb has just been overhauled and fuel had to make its way into all the passageways and ports. Warmed it up and then hesitatingly applied throttle to see if it was going to gag and cough without pulling carb heat. It did not. Power ran up, ran down, and idle is smooth. I shut it down and will play with it some more this weekend, but it appears to be ready to put the cowling back on and resume taxi testing. If all goes well, I should get some air under the wings on Saturday. Oh, yeah, and a quick check of the new main seal confirmed that it's bone dry, so hopefully no more oil mist after the oil gets good and hot and thin. I'll find out after I can fly it for at least a few circuits of the field. -------- Oscar Zuniga Medford, OR Air Camper NX41CC &quot;Scout&quot; A75 power Read this topic online here: http://forums.matronics.com/viewtopic.php?p=422922#422922


    Message 13


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    Time: 07:57:19 PM PST US
    From: "Clif Dawson" <cdawson5854@shaw.ca>
    Subject: Re: 3 Piece Wing Question
    Lady to tigermoth pilot. "Is this old plane safe to fly?" Pilot replies, " Lady, how do you think this plane got to be so old?" Clif Worry gives a small thing a big shadow. Swedish proverb All great truths begin as blasphemies. George Bernard Shaw ----- Original Message ----- From: Cuy, Michael D. (GRC-RXD0)[Vantage Partners, You and Jeff Boatright have apparently cheated death every time you have flown! That is such a true statement, at least for me, Jack and it has nothing to do with my wing spars...just my nature as a pilot sometimes!


    Message 14


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    Time: 08:56:50 PM PST US
    Subject: Re: 3 Piece Wing Question
    From: "taildrags" <taildrags@hotmail.com>
    Wow. Wow! I felt my legs start to quiver and turn to jelly as I read about the spar ends having to butt with zero clearance at the centersection spars. That is, until I read Mikee's comforting post! And Jeff's! Whew... and I was just about to take the chainsaw to poor old Scout for being of questionable integrity. I just re-hung the wings recently, and if memory serves, there is a generous gap between the main spar and centersection spar butts. Very similar to what Jeff describes for his setup. So... reading Jack's stress analysis, the wing spar attach bolts on my wings carry all of the loads in single shear, because there is no continuous path between inner and outer spars through the wood. I'll have to analyze what those stresses might be, although I just replaced all the wing and strut attach bolts/nuts and those particular ones showed no distress and certainly didn't have any shear deformation on them. As far as dihedral, just a few days ago I sighted down the trailing edge of my wing, from wingtip to wingtip, for the very reason that the dihedral distinctly transitions down one wing, to perfectly flat at the centersection flop, and back up as it goes out to the opposite tip. I thought it looked a little curious at the time, almost like where a bird's wings join its body. I have stretched a cord between the wingtips once upon a time and in the middle, the cord stood 3" above the centersection. Scout may not have the most dihedral of any Air Camper out there, but it does have more than many. I'm thinking we need to have one of the artists among us create a special decal or patch that can only be worn by "cheaters of death" like us. We need a catchy motto, too, like "I Made The Cut/My Spars Don't Butt". I'll leave the graphics up to your imagination. -------- Oscar Zuniga Medford, OR Air Camper NX41CC &quot;Scout&quot; A75 power Read this topic online here: http://forums.matronics.com/viewtopic.php?p=422939#422939




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