Original Posted By: "Jack Phillips"
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 outerpanel spar ends butt together with "0 clearance at assembly. How does onecut the spar ends accurately enough to achieve this and not introduce any dihedralor anhedral when assembled (i.e. flat panel from tip to tip)? Can shimsbe used at final assembly to get proper alignment?Does the lack of any fitting holding the upper edges of the spars together botheranyone but me? Lots of these craft are flying with 3 piece wings built tothe plans but it just to seems odd to me that the only thing keeping the sparsbutted together is lift force and any preload provided by the lift strut. Whatam I missing here?Grant ZiebellSavannah, TNRead this topic online here:http://forums.matronics.com/viewtopic.p ... __________
Pietenpol-List: 3 Piece Wing Question
RE: Pietenpol-List: 3 Piece Wing Question
Original Posted By: owner-pietenpol-list-server(at)matronics.com
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/tutor ... alues.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 PhillipsNX899JPSmith Mountain Lake, Virginia-----Original Message-----
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/tutor ... alues.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 PhillipsNX899JPSmith Mountain Lake, Virginia-----Original Message-----
Pietenpol-List: Re: 3 Piece Wing Question
Original Posted By: "Cuy, Michael D. (GRC-RXD0)[Vantage Partners, LLC]"
Fantastic answer to his question. The only thing I can add is that (as far asI 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 offlight.Happy landings,--------Scott LiefeldFlying N11MS since March 1972Steel TubeC-85-12Wire WheelsBrodhead in 1996Read this topic online here:http://forums.matronics.com/viewtopic.p ... __________
Fantastic answer to his question. The only thing I can add is that (as far asI 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 offlight.Happy landings,--------Scott LiefeldFlying N11MS since March 1972Steel TubeC-85-12Wire WheelsBrodhead in 1996Read this topic online here:http://forums.matronics.com/viewtopic.p ... __________
Re: Pietenpol-List: 3 Piece Wing Question
Original Posted By: Steven Dortch
Grant,My center section spars and L & R wing panel spar ends do not butt up against each other. I respect Jack Phillips mechanical load analysis as he is a professional mechanical/aerotypeengineer 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 littlebecause 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 ends and the outer wing panel sparends so I assume (after flying mine for the past 16 years) that the metal fittings and bolts which join the CC and wing panels together is sufficient to take the loads given that I know fora fact my spar ends are not flush against each other.Mike C.Ohio________________________________________________________________________________Date: Tue, 6 May 2014 14:13:57 -0500Subject: Re: Pietenpol-List: 3 Piece Wing Question
Grant,My center section spars and L & R wing panel spar ends do not butt up against each other. I respect Jack Phillips mechanical load analysis as he is a professional mechanical/aerotypeengineer 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 littlebecause 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 ends and the outer wing panel sparends so I assume (after flying mine for the past 16 years) that the metal fittings and bolts which join the CC and wing panels together is sufficient to take the loads given that I know fora fact my spar ends are not flush against each other.Mike C.Ohio________________________________________________________________________________Date: Tue, 6 May 2014 14:13:57 -0500Subject: Re: Pietenpol-List: 3 Piece Wing Question
Re: Pietenpol-List: 3 Piece Wing Question
Original Posted By: Ken Bickers
Subject: Re: Pietenpol-List: 3 Piece Wing Question
Subject: Re: Pietenpol-List: 3 Piece Wing Question
Re: Pietenpol-List: 3 Piece Wing Question
Original Posted By: , "LLC]" >
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 metal straps that extend several inches down the length of the spars, with bolts 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 overlap 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=97Don=92t know if it=92s safe, but the plane has been flying that way since 1978.--Jeffrey H. Boatright, PhD, FARVOProfessor of OphthalmologyEmory University School of Medicine
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 metal straps that extend several inches down the length of the spars, with bolts 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 overlap 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=97Don=92t know if it=92s safe, but the plane has been flying that way since 1978.--Jeffrey H. Boatright, PhD, FARVOProfessor of OphthalmologyEmory University School of Medicine
RE: Pietenpol-List: 3 Piece Wing Question
Original Posted By: "Jack Phillips"
I know of Piet spars (one on a flying Scout) that have notches dug into them in order for the wing strut attach 'straddle' fitting to go lowenough so the bottom of the fitting fit thru the fabric of the lower wing enough to bolt on the four lift struts........I've seen others that havePiet 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 beenflying since 1978? Nice!Mike C.Ohio________________________________________________________________________________
I know of Piet spars (one on a flying Scout) that have notches dug into them in order for the wing strut attach 'straddle' fitting to go lowenough so the bottom of the fitting fit thru the fabric of the lower wing enough to bolt on the four lift struts........I've seen others that havePiet 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 beenflying since 1978? Nice!Mike C.Ohio________________________________________________________________________________
RE: Pietenpol-List: 3 Piece Wing Question
Original Posted By: owner-pietenpol-list-server(at)matronics.com
You and Jeff Boatright have apparently cheated death every time you haveflown! Obviously, the strap type fittings spread the loads sufficiently through thewood of the spar to lower the stress to safe levels. The numbers I ran thismorning 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 withjust one bolt securing it as it needs to be, and no extra concerns arenecessary to add a slight amount of dihedral or washout ' just do it withthe lift struts.Jack PhillipsNX899JPSmith Mountain Lake, Virginia _____
You and Jeff Boatright have apparently cheated death every time you haveflown! Obviously, the strap type fittings spread the loads sufficiently through thewood of the spar to lower the stress to safe levels. The numbers I ran thismorning 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 withjust one bolt securing it as it needs to be, and no extra concerns arenecessary to add a slight amount of dihedral or washout ' just do it withthe lift struts.Jack PhillipsNX899JPSmith Mountain Lake, Virginia _____
Re: Pietenpol-List: 3 Piece Wing Question
Original Posted By: Cuy, Michael D. (GRC-RXD0)[Vantage Partners,
Lady to tigermoth pilot. "Is this old plane safe to fly?"Pilot replies, " Lady, how do you think this planegot to be so old?"ClifWorry gives a small thing a big shadow. Swedish proverbAll great truths begin as blasphemies. George Bernard Shaw ----- Original Message -----
Lady to tigermoth pilot. "Is this old plane safe to fly?"Pilot replies, " Lady, how do you think this planegot to be so old?"ClifWorry gives a small thing a big shadow. Swedish proverbAll great truths begin as blasphemies. George Bernard Shaw ----- Original Message -----
Pietenpol-List: Re: 3 Piece Wing Question
Original Posted By: Michael Perez
Wow. Wow! I felt my legs start to quiver and turn to jelly as I read about thespar ends having to butt with zero clearance at the centersection spars. Thatis, until I read Mikee's comforting post! And Jeff's! Whew... and I was justabout 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 generousgap between the main spar and centersection spar butts. Very similar towhat Jeff describes for his setup. So... reading Jack's stress analysis, thewing spar attach bolts on my wings carry all of the loads in single shear, becausethere 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 replacedall the wing and strut attach bolts/nuts and those particular ones showedno 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 mywing, from wingtip to wingtip, for the very reason that the dihedral distinctlytransitions down one wing, to perfectly flat at the centersection flop, andback up as it goes out to the opposite tip. I thought it looked a little curiousat the time, almost like where a bird's wings join its body. I have stretcheda cord between the wingtips once upon a time and in the middle, the cordstood 3" above the centersection. Scout may not have the most dihedral of anyAir 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 decalor patch that can only be worn by "cheaters of death" like us. We need a catchymotto, too, like "I Made The Cut/My Spars Don't Butt". I'll leave the graphicsup to your imagination.--------Oscar ZunigaMedford, ORAir Camper NX41CC "Scout"A75 powerRead this topic online here:http://forums.matronics.com/viewtopic.p ... ______Date: Wed, 7 May 2014 04:54:22 -0700 (PDT)
Wow. Wow! I felt my legs start to quiver and turn to jelly as I read about thespar ends having to butt with zero clearance at the centersection spars. Thatis, until I read Mikee's comforting post! And Jeff's! Whew... and I was justabout 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 generousgap between the main spar and centersection spar butts. Very similar towhat Jeff describes for his setup. So... reading Jack's stress analysis, thewing spar attach bolts on my wings carry all of the loads in single shear, becausethere 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 replacedall the wing and strut attach bolts/nuts and those particular ones showedno 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 mywing, from wingtip to wingtip, for the very reason that the dihedral distinctlytransitions down one wing, to perfectly flat at the centersection flop, andback up as it goes out to the opposite tip. I thought it looked a little curiousat the time, almost like where a bird's wings join its body. I have stretcheda cord between the wingtips once upon a time and in the middle, the cordstood 3" above the centersection. Scout may not have the most dihedral of anyAir 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 decalor patch that can only be worn by "cheaters of death" like us. We need a catchymotto, too, like "I Made The Cut/My Spars Don't Butt". I'll leave the graphicsup to your imagination.--------Oscar ZunigaMedford, ORAir Camper NX41CC "Scout"A75 powerRead this topic online here:http://forums.matronics.com/viewtopic.p ... ______Date: Wed, 7 May 2014 04:54:22 -0700 (PDT)
Pietenpol-List: Re: 3 Piece Wing Question
Original Posted By: "aerocarjake"
Wow! I wish you guys would have posted this a year ago......i agonized over gettingthat joint right and build in some dihedral. spend hours marking finite anglesand filing the center section spars to keep the joint tight......next timethe wings come off, i'm going to take some more off cause i would like a smidgemore dihedral, but i wont be so precise.--------NX321LRNow test flying!!Mitsubishi PoweredRead this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Pietenpol-List: Re: 3 Piece Wing Question
Wow! I wish you guys would have posted this a year ago......i agonized over gettingthat joint right and build in some dihedral. spend hours marking finite anglesand filing the center section spars to keep the joint tight......next timethe wings come off, i'm going to take some more off cause i would like a smidgemore dihedral, but i wont be so precise.--------NX321LRNow test flying!!Mitsubishi PoweredRead this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Pietenpol-List: Re: 3 Piece Wing Question
Re: Pietenpol-List: Re: 3 Piece Wing Question
Original Posted By: glenschweizer(at)yahoo.com
VERY timely...!! I've been working on this joint - last weekend and this upcomingweekend. THANK YOU to everyone who provided input.--------Jake Schultz - curator,Newport Way Air Museum (OK, it's just my home)Read this topic online here:http://forums.matronics.com/viewtopic.p ... ttachments: http://forums.matronics.com//files/wing ... ___Subject: Re: Pietenpol-List: Re: 3 Piece Wing Question
VERY timely...!! I've been working on this joint - last weekend and this upcomingweekend. THANK YOU to everyone who provided input.--------Jake Schultz - curator,Newport Way Air Museum (OK, it's just my home)Read this topic online here:http://forums.matronics.com/viewtopic.p ... ttachments: http://forums.matronics.com//files/wing ... ___Subject: Re: Pietenpol-List: Re: 3 Piece Wing Question
Pietenpol-List: Re: 3 Piece Wing Question
Original Posted By: jim hyde
glen wrote:> Hey Chris > I noticed at the bottom of your post Mitsubishi powered. Please tell me aboutthat! Glen> > Sent from my iPhone> > > > On May 7, 2014, at 5:39 AM, "Chris Rusch" wrote:> > > > > > > > Wow! I wish you guys would have posted this a year ago......i agonized overgetting that joint right and build in some dihedral. spend hours marking finiteangles and filing the center section spars to keep the joint tight......nexttime the wings come off, i'm going to take some more off cause i would likea smidge more dihedral, but i wont be so precise.> > > > --------> > NX321LR> > Now test flying!!> > Mitsubishi Powered> > > > > > > > > > Read this topic online here:> > > > http://forums.matronics.com/viewtopic.p ... 949#422949> > > > > > > > Hi glen,> > Just look up my profile on here and go thru my previous posts....it all inhere somewhere> > > > > > > > > > > > > > > --------NX321LRNow test flying!!Mitsubishi PoweredRead this topic online here:http://forums.matronics.com/viewtopic.p ... ______Date: Wed, 7 May 2014 20:32:09 -0700 (PDT)
glen wrote:> Hey Chris > I noticed at the bottom of your post Mitsubishi powered. Please tell me aboutthat! Glen> > Sent from my iPhone> > > > On May 7, 2014, at 5:39 AM, "Chris Rusch" wrote:> > > > > > > > Wow! I wish you guys would have posted this a year ago......i agonized overgetting that joint right and build in some dihedral. spend hours marking finiteangles and filing the center section spars to keep the joint tight......nexttime the wings come off, i'm going to take some more off cause i would likea smidge more dihedral, but i wont be so precise.> > > > --------> > NX321LR> > Now test flying!!> > Mitsubishi Powered> > > > > > > > > > Read this topic online here:> > > > http://forums.matronics.com/viewtopic.p ... 949#422949> > > > > > > > Hi glen,> > Just look up my profile on here and go thru my previous posts....it all inhere somewhere> > > > > > > > > > > > > > > --------NX321LRNow test flying!!Mitsubishi PoweredRead this topic online here:http://forums.matronics.com/viewtopic.p ... ______Date: Wed, 7 May 2014 20:32:09 -0700 (PDT)
Re: Pietenpol-List: Re: 3 Piece Wing Question
Original Posted By: Michael Perez
RE: Pietenpol-List: 3 Piece Wing Question
Original Posted By: "Cuy, Michael D. (GRC-RXD0)[Vantage Partners, LLC]"
etenpol-list(at)matronics.com>Subject: RE: Pietenpol-List: 3 Piece Wing QuestionGrant,My center section spars and L & R wing panel spar ends do not butt up against each other. I respect Jack Phillips mechanical load analysis as he is a professional mechanical/aerotypeengineer 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 littlebecause 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 ends and the outer wing panel sparends so I assume (after flying mine for the past 16 years) that the metal fittings and bolts which join the CC and wing panels together is sufficient to take the loads given that I know fora 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 ofthe intended recipient(s) and may contain confidential and privilegedinformation. If the reader of this message is not the intendedrecipient, you are hereby notified that any dissemination, distributionor copying of this message (including any attachments) is strictlyprohibited.If you have received this message in error, please contactthe sender by reply e-mail message and destroy all copies of theoriginal message (including attachments).________________________________________________________________________________
etenpol-list(at)matronics.com>Subject: RE: Pietenpol-List: 3 Piece Wing QuestionGrant,My center section spars and L & R wing panel spar ends do not butt up against each other. I respect Jack Phillips mechanical load analysis as he is a professional mechanical/aerotypeengineer 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 littlebecause 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 ends and the outer wing panel sparends so I assume (after flying mine for the past 16 years) that the metal fittings and bolts which join the CC and wing panels together is sufficient to take the loads given that I know fora 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 ofthe intended recipient(s) and may contain confidential and privilegedinformation. If the reader of this message is not the intendedrecipient, you are hereby notified that any dissemination, distributionor copying of this message (including any attachments) is strictlyprohibited.If you have received this message in error, please contactthe sender by reply e-mail message and destroy all copies of theoriginal message (including attachments).________________________________________________________________________________