Original Posted By: "Richard Schreiber"
Subject: Pietenpol-List: tail bracingThere is a TON of propwash over the tailfeathers that is CONSTANTLY vibrating all the brace cables, elevator, and rudder cables. I would stick with the 3/32 on the tailfeathers and also from the bellcrankback to the elevator controls.When I look over my shoulder I'm amazed at how much the propwash messes with everything back there.So just like you do when you have a forced night landing "if you don't like what you see......turn the landing light off"Mike C.PS-On the other hand I've seen many Piets using 1/8" tail brace cable and aileron cable which to me is justoverkill and is a weight penalty to boot. No offense to those seeking more security though using the 1/8" cables--- byall means that beats risking your life going too thin just to save a few oz.________________________________________________________________________________
Pietenpol-List: tail bracing
RE: Pietenpol-List: Re: tail bracing
Original Posted By: VAHOWDY(at)aol.com
HiJust quickly read this post and wondered if you had figured the load on the wire is not vertical but at quite an angle.- This will up the load quite a bit.Just thinking about the load on sailboat shrouds and how the angles come into play.Steve in Maine
HiJust quickly read this post and wondered if you had figured the load on the wire is not vertical but at quite an angle.- This will up the load quite a bit.Just thinking about the load on sailboat shrouds and how the angles come into play.Steve in Maine
Re: Pietenpol-List: Re: tail bracing
Original Posted By: Steve Glass
My Piet has 1/16 cables for tail bracing it more than strong enough.-Like Howdy, I calculated the load but in reverse, I started with max cable strength and worked it out from there.My conclusion was that all the wood will break long before any of the 1/16 cable would.-Close to 100 Flying hours no problems noticed-Hans-NX15KV-----Original Message-----
My Piet has 1/16 cables for tail bracing it more than strong enough.-Like Howdy, I calculated the load but in reverse, I started with max cable strength and worked it out from there.My conclusion was that all the wood will break long before any of the 1/16 cable would.-Close to 100 Flying hours no problems noticed-Hans-NX15KV-----Original Message-----
Re: Pietenpol-List: Re: tail bracing
Original Posted By: "David Paule"
Speedbrake,-- I think that there would be minimal vibration on the bolt.- I think the wood it passes through would dampen any vibration.- Now the tab is a different story.- I just feel that a wire that has a harmonic vibration could fatigue the fitting over time.- Harmonic vibration is a funny thing.- a small change in speed/load/RPM will make it-come and go,-but at just the right speed it adds force, just like someone on a trampoline, each jump adds force/height.- Changing the location of the cable is not a good idea.- Their placement, even though thru trial and error, are where they are out of need.- The one thing that could be done is to make each cable a slightly -different length.- that way each one would have a different harmonic.-- I have seen small V's- added to power lines to stop this harmonic.-Maybe you have seen them too.-I guess It would work on a plane that was having a problem.- I wouldn't do anything unless I had a problem first.- I think a design change could be made using tubing for the cable.- It should cost less (no turnbuckles) but weigh more.- This would not vibrate at Piet flight speeds.-Many of aircraft us this method.-Ryan,-- You could be right about me and T-88 usage.- I do remember my shop being in the 60's in the winter.The first break was an accident.- My table saw jammed and sent a piece of wood into my wing.- This broke out-two ribs-.- These were not stick ribs but 1/4 ply to a box spar.-The joint was 5 in. long. To my surprise the joints came apart with all the T-88 on one side, mostly on the ribs.- I know others love T-88. - I would just suggest doing a little destructive testing.- This should be done with each mixed batch.-There is always a little leftover. -Howdy-________________________________________________________________________________
Speedbrake,-- I think that there would be minimal vibration on the bolt.- I think the wood it passes through would dampen any vibration.- Now the tab is a different story.- I just feel that a wire that has a harmonic vibration could fatigue the fitting over time.- Harmonic vibration is a funny thing.- a small change in speed/load/RPM will make it-come and go,-but at just the right speed it adds force, just like someone on a trampoline, each jump adds force/height.- Changing the location of the cable is not a good idea.- Their placement, even though thru trial and error, are where they are out of need.- The one thing that could be done is to make each cable a slightly -different length.- that way each one would have a different harmonic.-- I have seen small V's- added to power lines to stop this harmonic.-Maybe you have seen them too.-I guess It would work on a plane that was having a problem.- I wouldn't do anything unless I had a problem first.- I think a design change could be made using tubing for the cable.- It should cost less (no turnbuckles) but weigh more.- This would not vibrate at Piet flight speeds.-Many of aircraft us this method.-Ryan,-- You could be right about me and T-88 usage.- I do remember my shop being in the 60's in the winter.The first break was an accident.- My table saw jammed and sent a piece of wood into my wing.- This broke out-two ribs-.- These were not stick ribs but 1/4 ply to a box spar.-The joint was 5 in. long. To my surprise the joints came apart with all the T-88 on one side, mostly on the ribs.- I know others love T-88. - I would just suggest doing a little destructive testing.- This should be done with each mixed batch.-There is always a little leftover. -Howdy-________________________________________________________________________________
Re: Pietenpol-List: Re: tail bracing
Original Posted By: Michael Perez
Stainless steel bolts will have a very low yield strength, less than half the yield strength of steel AN bolts.-I sure as heck wouldn't use them in a structural application.-They should only be used where specified by the designer.-David Paule-------- Original Message -----
Stainless steel bolts will have a very low yield strength, less than half the yield strength of steel AN bolts.-I sure as heck wouldn't use them in a structural application.-They should only be used where specified by the designer.-David Paule-------- Original Message -----
RE: Pietenpol-List: tail bracing
Original Posted By: owner-pietenpol-list-server(at)matronics.com
Mike,I've heard the same from more than one Piet owner. As you know this alsoincludes the leading edge of the vertical stab. Because of this it has beensuggested by some to attach the vertical stab wires forward and aft on thetop. I may do this myself.JackDSM _____
Mike,I've heard the same from more than one Piet owner. As you know this alsoincludes the leading edge of the vertical stab. Because of this it has beensuggested by some to attach the vertical stab wires forward and aft on thetop. I may do this myself.JackDSM _____
Re: Pietenpol-List: airworthiness papers display
Original Posted By: Ryan Mueller
Douwe, Just keep it on board, without undue looking. New rule ???????Pieti LowellRead this topic online here:http://forums.matronics.com/viewtopic.p ... ______Date: Thu, 7 Jan 2010 08:54:43 -0600Subject: Re: Pietenpol-List: airworthiness papers display
Douwe, Just keep it on board, without undue looking. New rule ???????Pieti LowellRead this topic online here:http://forums.matronics.com/viewtopic.p ... ______Date: Thu, 7 Jan 2010 08:54:43 -0600Subject: Re: Pietenpol-List: airworthiness papers display
Pietenpol-List: Re: tail bracing
Original Posted By: Michael Perez
I would like to emphasis the excellent (an extremely important) point Mike bringsup about tail flutter and "harmonics". I know BP did not have access to thisinformation, but certainly came up with a very successful design. As late asthe 1980's the F-18 was plagued with a tail vibration cracking problem whichgrounded the fleet for weeks. This was due to the wind vortices' caused by theleading edge extensions (LEX), generally at lower speeds. Very similarly, propwash acts on tail surfaces (in many different directions), causing flutter andharmonics (and in IMHO, to a greater degree then the example above). Althoughvery controllable when understood and designed accordingly, I would recommendobtaining a good understanding of all the forces and stresses at work beforestraying to far from the tried and true, especially on a Piet with a less stoutempennage. Im not an engineer, just my personal experience. Actual engineers,feel free to correct my interpretation as required.SteveRead this topic online here:http://forums.matronics.com/viewtopic.p ... ttachments: http://forums.matronics.com//files/f18_ ... ______Date: Thu, 7 Jan 2010 08:08:46 -0800 (PST)
I would like to emphasis the excellent (an extremely important) point Mike bringsup about tail flutter and "harmonics". I know BP did not have access to thisinformation, but certainly came up with a very successful design. As late asthe 1980's the F-18 was plagued with a tail vibration cracking problem whichgrounded the fleet for weeks. This was due to the wind vortices' caused by theleading edge extensions (LEX), generally at lower speeds. Very similarly, propwash acts on tail surfaces (in many different directions), causing flutter andharmonics (and in IMHO, to a greater degree then the example above). Althoughvery controllable when understood and designed accordingly, I would recommendobtaining a good understanding of all the forces and stresses at work beforestraying to far from the tried and true, especially on a Piet with a less stoutempennage. Im not an engineer, just my personal experience. Actual engineers,feel free to correct my interpretation as required.SteveRead this topic online here:http://forums.matronics.com/viewtopic.p ... ttachments: http://forums.matronics.com//files/f18_ ... ______Date: Thu, 7 Jan 2010 08:08:46 -0800 (PST)
RE: Pietenpol-List: Corvair Piet Oil Cooler locations?
Original Posted By: fmetcalf(at)bellsouth.net
I wrote yesterday about the cowling edges as to if they were wire edged or hemmed or what. I forgot to ask what gauge aluminum you used for the engine cowling. We are ready to start on that this weekend. Thank you for your help. We hope ours will soon look as nice as yours . Vic GroahDate: Wed=2C 6 Jan 2010 08:59:02 -0800
I wrote yesterday about the cowling edges as to if they were wire edged or hemmed or what. I forgot to ask what gauge aluminum you used for the engine cowling. We are ready to start on that this weekend. Thank you for your help. We hope ours will soon look as nice as yours . Vic GroahDate: Wed=2C 6 Jan 2010 08:59:02 -0800
Re: Pietenpol-List: Re: tail bracing
Original Posted By: Frank Metcalfe
Subject: Re: Pietenpol-List: Re: tail bracingAt the risk of "scarring the hell" out of Rambo. I think using 1/16 cable would be more than strong enough. The load on the stabilizer is much like the load on the wing. With the cable placement, one third of the load is carried by the fuselage and the other two thirds are carried by the cables. The loading of the tail is less than the wing. I will use a very heavy load of 10 lb. sq. ft. for my example. The load on the tail moves the arm of the fuselage about the C. G. The sq. ft. load is 90"x 36" or less than 3240 sq .in. 3240/144= less than 22.5 sq.feet 22.5 sq. ft. x 10 lb per sq. ft. tail loading = 225 lbs max load on the tail. Of the 225 lbs. 1/3 carried by the fuselage or 85 lbs. 170 lbs are carried by the 4 wires. Four in tension on the fin, or four in tension on the fuselage. If you use a safety factor of 4 than each wire would carry 170 lbs. If you can hang off of one of your made up cables they are more than strong enough. And for vibration, a tight wire is much more likely to vibrate. These wires should not be that tight. They stop the deflection of the stabilizer and carry the load of the elevator. The back wire carries 1/2 the stabilizer plus the elevator, so the back wire carries more load that the frontone. One back wire would carry the load fine but would not triangulate the stabilizer front to back. And while I'm on my soap box, I think T-88 is not so wonderful. I have made multiple test breaks and have seen at least four joint failures. T-88 can lay on top of the would and not penetrate. These breaks are most often spruce to ply. The glue pulling off the ply with a few splinters. I think I remember reading in their directions that it can be thinned to help with penetration, but then you lose that nice filet. Roughing the ply helps with this. Rambo, I was not saying to use a grade 3 bolt. lb for lb you should the strongest part. The way things are engineered on an aircraft is to use apart that is strong enough to do the job plus a safety factor. Other wise we would be using 3/4 inch bolts for everything. I still think SS bolts are stronger than they need to be for this application. Harmonic vibration is a separate problem to itself. Harmonic vibration and vibration are two different things. I really like Malcolm Morrison's way of saving 8 turnbuckles. I can make tail cables several times to get the right length and still save a gob of money. Howdy________________________________________________________________________________Date: Thu, 7 Jan 2010 11:31:51 -0800 (PST)
Subject: Re: Pietenpol-List: Re: tail bracingAt the risk of "scarring the hell" out of Rambo. I think using 1/16 cable would be more than strong enough. The load on the stabilizer is much like the load on the wing. With the cable placement, one third of the load is carried by the fuselage and the other two thirds are carried by the cables. The loading of the tail is less than the wing. I will use a very heavy load of 10 lb. sq. ft. for my example. The load on the tail moves the arm of the fuselage about the C. G. The sq. ft. load is 90"x 36" or less than 3240 sq .in. 3240/144= less than 22.5 sq.feet 22.5 sq. ft. x 10 lb per sq. ft. tail loading = 225 lbs max load on the tail. Of the 225 lbs. 1/3 carried by the fuselage or 85 lbs. 170 lbs are carried by the 4 wires. Four in tension on the fin, or four in tension on the fuselage. If you use a safety factor of 4 than each wire would carry 170 lbs. If you can hang off of one of your made up cables they are more than strong enough. And for vibration, a tight wire is much more likely to vibrate. These wires should not be that tight. They stop the deflection of the stabilizer and carry the load of the elevator. The back wire carries 1/2 the stabilizer plus the elevator, so the back wire carries more load that the frontone. One back wire would carry the load fine but would not triangulate the stabilizer front to back. And while I'm on my soap box, I think T-88 is not so wonderful. I have made multiple test breaks and have seen at least four joint failures. T-88 can lay on top of the would and not penetrate. These breaks are most often spruce to ply. The glue pulling off the ply with a few splinters. I think I remember reading in their directions that it can be thinned to help with penetration, but then you lose that nice filet. Roughing the ply helps with this. Rambo, I was not saying to use a grade 3 bolt. lb for lb you should the strongest part. The way things are engineered on an aircraft is to use apart that is strong enough to do the job plus a safety factor. Other wise we would be using 3/4 inch bolts for everything. I still think SS bolts are stronger than they need to be for this application. Harmonic vibration is a separate problem to itself. Harmonic vibration and vibration are two different things. I really like Malcolm Morrison's way of saving 8 turnbuckles. I can make tail cables several times to get the right length and still save a gob of money. Howdy________________________________________________________________________________Date: Thu, 7 Jan 2010 11:31:51 -0800 (PST)
Re: Pietenpol-List: Re: tail bracing
Original Posted By: hvandervoo(at)aol.com
Subject: Re: Pietenpol-List: Re: tail bracing- At the risk of "scarring the hell" out of Rambo.- I think using 1/16 cable would be more than strong enough.- The load on the stabilizer is-much like the load on the wing.- With the cable placement, one third of the load is carried by the fuselage and the other two thirds are carried by the cables.- The loading of the tail is less than the wing. I will use a very heavy load of 10 lb. sq. ft. for my example. The load on the tail moves the arm of the fuselage about the C. G.-- The sq. ft. load is----- -90"x 36"-or -less than 3240 sq .in.-------- 3240/144= less than 22.5 sq.feet---- 22.5 sq. ft. x 10 lb per sq. ft. tail loading-=- 225 lbs max load on the tail.---Of -the 225 lbs. 1/3 carried by the fuselage-or 85 lbs.--- 170 lbs-are carried by the 4 wires.---Four in-tension on the fin, or-four in tension on the fuselage. If you use a safety factor of 4 than each wire would carry 170 lbs.-- If you can hang off of one of your made up cables they are more than strong enough.---And for vibration, a tight wire is much more likely to vibrate.- These wires should not be that tight.- They stop the deflection-of the stabilizer and carry the load-of the elevator.- The back wire carries 1/2 the stabilizer plus the elevator, so the back wire carries more load that the front one.-One back wire would carry the load fine but would not triangulate the stabilizer front to back.-----And while I'm on my soap box, I think T-88 is not so wonderful.-- I have made multiple test breaks and have seen at least four joint failures.- T-88 can lay on top of the would and not penetrate.- These breaks are most often spruce to ply.- The glue pulling off the ply with a few splinters. I think I remember reading -in their directions that it can be thinned to help with penetration, but then you lose that nice filet. Roughing- the ply helps with this.-- Rambo, I was not saying to use a grade 3 bolt. - lb for lb you should the strongest part.- The way things are engineered on an aircraft is to use-a part that is strong enough to do the job plus a safety factor.- Other wise we would be using 3/4 inch bolts for everything.- I still think SS bolts are stronger than they need to be for this application.- Harmonic vibration is a separate problem to itself.- Harmonic vibration and vibration are two different things.-- I really like Malcolm Morrison's way of saving 8 turnbuckles.-I can make tail cables several times to get the right length and still save a gob of money.- -Howdyhttp://www.matronicshref="http://www.matronics.com/contribution">http://www.matronics.com/con================________________________________________________________________________________Subject: Re: Pietenpol-List: Re: tail bracingDate: Thu, 07 Jan 2010 15:04:29 -0500
Subject: Re: Pietenpol-List: Re: tail bracing- At the risk of "scarring the hell" out of Rambo.- I think using 1/16 cable would be more than strong enough.- The load on the stabilizer is-much like the load on the wing.- With the cable placement, one third of the load is carried by the fuselage and the other two thirds are carried by the cables.- The loading of the tail is less than the wing. I will use a very heavy load of 10 lb. sq. ft. for my example. The load on the tail moves the arm of the fuselage about the C. G.-- The sq. ft. load is----- -90"x 36"-or -less than 3240 sq .in.-------- 3240/144= less than 22.5 sq.feet---- 22.5 sq. ft. x 10 lb per sq. ft. tail loading-=- 225 lbs max load on the tail.---Of -the 225 lbs. 1/3 carried by the fuselage-or 85 lbs.--- 170 lbs-are carried by the 4 wires.---Four in-tension on the fin, or-four in tension on the fuselage. If you use a safety factor of 4 than each wire would carry 170 lbs.-- If you can hang off of one of your made up cables they are more than strong enough.---And for vibration, a tight wire is much more likely to vibrate.- These wires should not be that tight.- They stop the deflection-of the stabilizer and carry the load-of the elevator.- The back wire carries 1/2 the stabilizer plus the elevator, so the back wire carries more load that the front one.-One back wire would carry the load fine but would not triangulate the stabilizer front to back.-----And while I'm on my soap box, I think T-88 is not so wonderful.-- I have made multiple test breaks and have seen at least four joint failures.- T-88 can lay on top of the would and not penetrate.- These breaks are most often spruce to ply.- The glue pulling off the ply with a few splinters. I think I remember reading -in their directions that it can be thinned to help with penetration, but then you lose that nice filet. Roughing- the ply helps with this.-- Rambo, I was not saying to use a grade 3 bolt. - lb for lb you should the strongest part.- The way things are engineered on an aircraft is to use-a part that is strong enough to do the job plus a safety factor.- Other wise we would be using 3/4 inch bolts for everything.- I still think SS bolts are stronger than they need to be for this application.- Harmonic vibration is a separate problem to itself.- Harmonic vibration and vibration are two different things.-- I really like Malcolm Morrison's way of saving 8 turnbuckles.-I can make tail cables several times to get the right length and still save a gob of money.- -Howdyhttp://www.matronicshref="http://www.matronics.com/contribution">http://www.matronics.com/con================________________________________________________________________________________Subject: Re: Pietenpol-List: Re: tail bracingDate: Thu, 07 Jan 2010 15:04:29 -0500
Re: Pietenpol-List: Re: tail bracing
Original Posted By: VAHOWDY(at)aol.com
Subject: Re: Pietenpol-List: Re: tail bracing At the risk of "scarring the hell" out of Rambo. I think using 1/16 cable would be more than strong enough. The load on the stabilizer is much like the load on the wing. With the cable placement, one third of the load is carried by the fuselage and the other two thirds are carried by the cables. The loading of the tail is less than the wing. I will use a very heavy load of 10 lb. sq. ft. for my example. The load on the tail moves the arm of the fuselage about the C. G. The sq. ft. load is 90"x 36" or less than 3240 sq .in. 3240/144= less than 22.5 sq.feet 22.5 sq. ft. x 10 lb per sq. ft. tail loading = 225 lbs max load on the tail. Of the 225 lbs. 1/3 carried by the fuselage or 85 lbs. 170 lbs are carried by the 4 wires. Four in tension on the fin, or four in tension on the fuselage. If you use a safety factor of 4 than each wire would carry 170 lbs. If you can hang off of one of your made up cables they are more than strong enough. And for vibration, a tight wire is much more likely to vibrate. These wires should not be that tight. They stop the deflection of the stabilizer and carry the load of the elevator. The back wire carries 1/2 the stabilizer plus the elevator, so the back wire carries more load that the front one. One back wire would carry the load fine but would not triangulate the stabilizer front to back. And while I'm on my soap box, I think T-88 is not so wonderful. I have made multiple test breaks and have seen at least four joint failures. T-88 can lay on top of the would and not penetrate. These breaks are most often spruce to ply. The glue pulling off the ply with a few splinters. I think I remember reading in their directions that it can be thinned to help with penetration, but then you lose that nice filet. Roughing the ply helps with this. Rambo, I was not saying to use a grade 3 bolt. lb for lb you should the strongest part. The way things are engineered on an aircraft is to use a part that is strong enough to do the job plus a safety factor. Other wise we would be using 3/4 inch bolts for everything. I still think SS bolts are stronger than they need to be for this application. Harmonic vibration is a separate problem to itself. Harmonic vibration and vibration are two different things. I really like Malcolm Morrison's way of saving 8 turnbuckles. I can make tail cables several times to get the right length and still save a gob of money. Howdyhttp://www.matronicshref="http://www.matronics.com/contribution">http://www.matronics.com/con===================================================-= - The Pietenpol-List Email Forum --= Use the Matronics List Features Navigator to browse-= the many List utilities such as List Un/Subscription,-= Archive Search & Download, 7-Day Browse, Chat, FAQ,-= Photoshare, and much much more:--= --> http://www.matronics.com/Navigator?Piet ... ========-= - MATRONICS WEB FORUMS --= Same great content also available via the Web Forums!--= --> http://forums.matronics.com--===========================================================-= - List Contribution Web Site --= Thank you for your generous support!-= -Matt Dralle, List Admin.-= --> http://www.matronics.com/contribution-= ... __________
Subject: Re: Pietenpol-List: Re: tail bracing At the risk of "scarring the hell" out of Rambo. I think using 1/16 cable would be more than strong enough. The load on the stabilizer is much like the load on the wing. With the cable placement, one third of the load is carried by the fuselage and the other two thirds are carried by the cables. The loading of the tail is less than the wing. I will use a very heavy load of 10 lb. sq. ft. for my example. The load on the tail moves the arm of the fuselage about the C. G. The sq. ft. load is 90"x 36" or less than 3240 sq .in. 3240/144= less than 22.5 sq.feet 22.5 sq. ft. x 10 lb per sq. ft. tail loading = 225 lbs max load on the tail. Of the 225 lbs. 1/3 carried by the fuselage or 85 lbs. 170 lbs are carried by the 4 wires. Four in tension on the fin, or four in tension on the fuselage. If you use a safety factor of 4 than each wire would carry 170 lbs. If you can hang off of one of your made up cables they are more than strong enough. And for vibration, a tight wire is much more likely to vibrate. These wires should not be that tight. They stop the deflection of the stabilizer and carry the load of the elevator. The back wire carries 1/2 the stabilizer plus the elevator, so the back wire carries more load that the front one. One back wire would carry the load fine but would not triangulate the stabilizer front to back. And while I'm on my soap box, I think T-88 is not so wonderful. I have made multiple test breaks and have seen at least four joint failures. T-88 can lay on top of the would and not penetrate. These breaks are most often spruce to ply. The glue pulling off the ply with a few splinters. I think I remember reading in their directions that it can be thinned to help with penetration, but then you lose that nice filet. Roughing the ply helps with this. Rambo, I was not saying to use a grade 3 bolt. lb for lb you should the strongest part. The way things are engineered on an aircraft is to use a part that is strong enough to do the job plus a safety factor. Other wise we would be using 3/4 inch bolts for everything. I still think SS bolts are stronger than they need to be for this application. Harmonic vibration is a separate problem to itself. Harmonic vibration and vibration are two different things. I really like Malcolm Morrison's way of saving 8 turnbuckles. I can make tail cables several times to get the right length and still save a gob of money. Howdyhttp://www.matronicshref="http://www.matronics.com/contribution">http://www.matronics.com/con===================================================-= - The Pietenpol-List Email Forum --= Use the Matronics List Features Navigator to browse-= the many List utilities such as List Un/Subscription,-= Archive Search & Download, 7-Day Browse, Chat, FAQ,-= Photoshare, and much much more:--= --> http://www.matronics.com/Navigator?Piet ... ========-= - MATRONICS WEB FORUMS --= Same great content also available via the Web Forums!--= --> http://forums.matronics.com--===========================================================-= - List Contribution Web Site --= Thank you for your generous support!-= -Matt Dralle, List Admin.-= --> http://www.matronics.com/contribution-= ... __________
Re: Pietenpol-List: Re: tail bracing
Original Posted By: Michael Perez
Subject: Re: Pietenpol-List: Re: tail bracing- At the risk of "scarring the hell" out of Rambo.- I think using 1/16 cable would be more than strong enough.- The load on the stabilizer is-much like the load on the wing.- With the cable placement, one third of the load is carried by the fuselage and the other two thirds are carried by the cables.- The loading of the tail is less than the wing. I will use a very heavy load of 10 lb. sq. ft. for my example. The load on the tail moves the arm of the fuselage about the C. G.-- The sq. ft. load is----- -90"x 36"-or -less than 3240 sq .in.-------- 3240/144= less than 22.5 sq.feet---- 22.5 sq. ft. x 10 lb per sq. ft. tail loading-=- 225 lbs max load on the tail.---Of -the 225 lbs. 1/3 carried by the fuselage-or 85 lbs.--- 170 lbs-are carried by the 4 wires.---Four in-tension on the fin, or-four in tension on the fuselage. If you use a safety factor of 4 than each wire would carry 170 lbs.-- If you can hang off of one of your made up cables they are more than strong enough.---And for vibration, a tight wire is much more likely to vibrate.- These wires should not be that tight.- They stop the deflection-of the stabilizer and carry the load-of the elevator.- The back wire carries 1/2 the stabilizer plus the elevator, so the back wire carries more load that the front one.-One back wire would carry the load fine but would not triangulate the stabilizer front to back.-----And while I'm on my soap box, I think T-88 is not so wonderful.-- I have made multiple test breaks and have seen at least four joint failures.- T-88 can lay on top of the would and not penetrate.- These breaks are most often spruce to ply.- The glue pulling off the ply with a few splinters. I think I remember reading -in their directions that it can be thinned to help with penetration, but then you lose that nice filet. Roughing- the ply helps with this.-- Rambo, I was not saying to use a grade 3 bolt. - lb for lb you should the strongest part.- The way things are engineered on an aircraft is to use-a part that is strong enough to do the job plus a safety factor.- Other wise we would be using 3/4 inch bolts for everything.- I still think SS bolts are stronger than they need to be for this application.- Harmonic vibration is a separate problem to itself.- Harmonic vibration and vibration are two different things.-- I really like Malcolm Morrison's way of saving 8 turnbuckles.-I can make tail cables several times to get the right length and still save a gob of money.- -Howdyhttp://www.matronicshref="http://www.matronics.com/contribution">http://www.matronics.com/con================t" target=_blank>http://www.matronics.com/Navigator?Piet ... ______Date: Thu, 7 Jan 2010 12:28:08 -0800 (PST)
Subject: Re: Pietenpol-List: Re: tail bracing- At the risk of "scarring the hell" out of Rambo.- I think using 1/16 cable would be more than strong enough.- The load on the stabilizer is-much like the load on the wing.- With the cable placement, one third of the load is carried by the fuselage and the other two thirds are carried by the cables.- The loading of the tail is less than the wing. I will use a very heavy load of 10 lb. sq. ft. for my example. The load on the tail moves the arm of the fuselage about the C. G.-- The sq. ft. load is----- -90"x 36"-or -less than 3240 sq .in.-------- 3240/144= less than 22.5 sq.feet---- 22.5 sq. ft. x 10 lb per sq. ft. tail loading-=- 225 lbs max load on the tail.---Of -the 225 lbs. 1/3 carried by the fuselage-or 85 lbs.--- 170 lbs-are carried by the 4 wires.---Four in-tension on the fin, or-four in tension on the fuselage. If you use a safety factor of 4 than each wire would carry 170 lbs.-- If you can hang off of one of your made up cables they are more than strong enough.---And for vibration, a tight wire is much more likely to vibrate.- These wires should not be that tight.- They stop the deflection-of the stabilizer and carry the load-of the elevator.- The back wire carries 1/2 the stabilizer plus the elevator, so the back wire carries more load that the front one.-One back wire would carry the load fine but would not triangulate the stabilizer front to back.-----And while I'm on my soap box, I think T-88 is not so wonderful.-- I have made multiple test breaks and have seen at least four joint failures.- T-88 can lay on top of the would and not penetrate.- These breaks are most often spruce to ply.- The glue pulling off the ply with a few splinters. I think I remember reading -in their directions that it can be thinned to help with penetration, but then you lose that nice filet. Roughing- the ply helps with this.-- Rambo, I was not saying to use a grade 3 bolt. - lb for lb you should the strongest part.- The way things are engineered on an aircraft is to use-a part that is strong enough to do the job plus a safety factor.- Other wise we would be using 3/4 inch bolts for everything.- I still think SS bolts are stronger than they need to be for this application.- Harmonic vibration is a separate problem to itself.- Harmonic vibration and vibration are two different things.-- I really like Malcolm Morrison's way of saving 8 turnbuckles.-I can make tail cables several times to get the right length and still save a gob of money.- -Howdyhttp://www.matronicshref="http://www.matronics.com/contribution">http://www.matronics.com/con================t" target=_blank>http://www.matronics.com/Navigator?Piet ... ______Date: Thu, 7 Jan 2010 12:28:08 -0800 (PST)
RE: Pietenpol-List: Re: tail bracing
Original Posted By: VAHOWDY(at)aol.com
HiJust quickly read this post and wondered if you had figured the load on the wire is not vertical but at quite an angle. This will up the load quite a bit.Just thinking about the load on sailboat shrouds and how the angles come into play.Steve in Maine
HiJust quickly read this post and wondered if you had figured the load on the wire is not vertical but at quite an angle. This will up the load quite a bit.Just thinking about the load on sailboat shrouds and how the angles come into play.Steve in Maine
Re: Pietenpol-List: Re: tail bracing
Original Posted By: Michael Perez
Subject: Re: Pietenpol-List: Re: tail bracingSteve, You are right. You would have to add the compression load of the stabilizer strut to the 170 lbs. The lower the angle the higher this compression. My point is, the flight loads are low on the stabilizer. 1/16cable has a breaking strength of 480 lbs. lots of margin. All this being said I'm using 3/32 on my Scout. I thought the question was, is it strong enough? Howdy________________________________________________________________________________Date: Thu, 7 Jan 2010 12:29:24 -0800 (PST)
Subject: Re: Pietenpol-List: Re: tail bracingSteve, You are right. You would have to add the compression load of the stabilizer strut to the 170 lbs. The lower the angle the higher this compression. My point is, the flight loads are low on the stabilizer. 1/16cable has a breaking strength of 480 lbs. lots of margin. All this being said I'm using 3/32 on my Scout. I thought the question was, is it strong enough? Howdy________________________________________________________________________________Date: Thu, 7 Jan 2010 12:29:24 -0800 (PST)
Re: Pietenpol-List: Re: tail bracing
Original Posted By: Michael Perez
Re: Pietenpol-List: Re: tail bracing
Original Posted By: Michael Perez
Subject: Re: Pietenpol-List: Re: tail bracingSpeedbrake, I think that there would be minimal vibration on the bolt. I think the wood it passes through would dampen any vibration. Now the tab is a different story. I just feel that a wire that has a harmonic vibration couldfatigue the fitting over time. Harmonic vibration is a funny thing. a smallchange in speed/load/RPM will make it come and go, but at just the right speed it adds force, just like someone on a trampoline, each jump adds force/height. Changing the location of the cable is not a good idea. Their placement, even though thru trial and error, are where they are out of need. The one thing that could be done is to make each cable a slightly different length. that way each one would have a different harmonic. I haveseen small V's added to power lines to stop this harmonic. Maybe you have seen them too. I guess It would work on a plane that was having a problem. I wouldn't do anything unless I had a problem first. I think a design change could be made using tubing for the cable. It should cost less (no turnbuckles) but weigh more. This would not vibrate at Piet flight speeds. Manyof aircraft us this method.Ryan, You could be right about me and T-88 usage. I do remember my shop being in the 60's in the winter.The first break was an accident. My table saw jammed and sent a piece of wood into my wing. This broke out two ribs . These were not stick ribs but 1/4 ply to a box spar. The joint was 5 in. long. To my surprise the joints came apart with all the T-88 on one side, mostly on the ribs. I know others love T-88. I would just suggest doing a little destructive testing. This should be done with each mixed batch. There is always a little leftover. Howdy________________________________________________________________________________Date: Thu, 7 Jan 2010 14:00:39 -0800 (PST)
Subject: Re: Pietenpol-List: Re: tail bracingSpeedbrake, I think that there would be minimal vibration on the bolt. I think the wood it passes through would dampen any vibration. Now the tab is a different story. I just feel that a wire that has a harmonic vibration couldfatigue the fitting over time. Harmonic vibration is a funny thing. a smallchange in speed/load/RPM will make it come and go, but at just the right speed it adds force, just like someone on a trampoline, each jump adds force/height. Changing the location of the cable is not a good idea. Their placement, even though thru trial and error, are where they are out of need. The one thing that could be done is to make each cable a slightly different length. that way each one would have a different harmonic. I haveseen small V's added to power lines to stop this harmonic. Maybe you have seen them too. I guess It would work on a plane that was having a problem. I wouldn't do anything unless I had a problem first. I think a design change could be made using tubing for the cable. It should cost less (no turnbuckles) but weigh more. This would not vibrate at Piet flight speeds. Manyof aircraft us this method.Ryan, You could be right about me and T-88 usage. I do remember my shop being in the 60's in the winter.The first break was an accident. My table saw jammed and sent a piece of wood into my wing. This broke out two ribs . These were not stick ribs but 1/4 ply to a box spar. The joint was 5 in. long. To my surprise the joints came apart with all the T-88 on one side, mostly on the ribs. I know others love T-88. I would just suggest doing a little destructive testing. This should be done with each mixed batch. There is always a little leftover. Howdy________________________________________________________________________________Date: Thu, 7 Jan 2010 14:00:39 -0800 (PST)
Re: Pietenpol-List: Re: tail bracing
Original Posted By: Michael Perez
Stainless steel bolts will have a very low yield strength, less than half the yield strength of steel AN bolts.I sure as heck wouldn't use them in a structural application.They should only be used where specified by the designer.David Paule ----- Original Message -----
Stainless steel bolts will have a very low yield strength, less than half the yield strength of steel AN bolts.I sure as heck wouldn't use them in a structural application.They should only be used where specified by the designer.David Paule ----- Original Message -----
Re: Pietenpol-List: Re: tail bracing
Original Posted By: Michael Perez
Re: Pietenpol-List: Re: tail bracing
Original Posted By: Michael Perez
Subject: Re: Pietenpol-List: Re: tail bracing At the risk of "scarring the hell" out of Rambo. I think using 1/16 cable would be more than strong enough. The load on the stabilizer is much like the load on the wing. With the cable placement=2C one third of the load is carried by the fuselage and the other two thirds are carried by the cables. The loading of the tail is less than the wing. I will use a very heavy load of 10 lb. sq. ft. for my example. The load on the tail moves the arm of the fuselage about the C. G. The sq. ft. load is 90"x 36" or less than 3240 sq .in. 3240/144= less than 22.5 sq.feet 22.5 sq. ft. x 10 lb per sq. ft. tail loading = 225 lbs max load on the tail. Of the 225 lbs. 1/3 carried by the fuselage or 85 lbs. 170 lbs are carried by the 4 wires. Four in tension on the fin=2C or four in tension on the fuselage. If you use a safety factor of 4 than each wire would carry 170 lbs. If you can hang off of one of your made up cables they are more than strong enough. And for vibration=2C a tight wire is much more likely to vibrate. These wires should not be that tight. They stop the deflection of the stabilizer and carry the load of the elevator. The back wire carries 1/2 the stabilizer plus the elevator=2C so the back wire carries more load that the front one. One back wire would carry the load fine but would not triangulate the stabilizer front to back. And while I'm on my soap box=2C I think T-88 is not so wonderful. I have made multiple test breaks and have seen at least four joint failures. T-88 can lay on top of the would and not penetrate. These breaks are most often spruce to ply. The glue pulling off the ply with a few splinters. I think I remember reading in their directions that it can be thinned to help with penetration=2C but then you lose that nice filet. Roughing the ply helps with this. Rambo=2C I was not saying to use a grade 3 bolt. lb for lb you should the strongest part. The way things are engineered on an aircraft isto use a part that is strong enough to do the job plus a safety factor. Other wise we would be using 3/4 inch bolts for everything. I still think SS bolts are stronger than they need to be for this application. Harmonic vibration is a separate problem to itself. Harmonic vibration and vibration are two different things. I really like Malcolm Morrison's way of saving 8 turnbuckles. I can make tail cables several times to get the right length and still save a gob of money. Howdy ________________________________________________________________________________Date: Thu, 7 Jan 2010 12:00:16 -0800 (PST)
Subject: Re: Pietenpol-List: Re: tail bracing At the risk of "scarring the hell" out of Rambo. I think using 1/16 cable would be more than strong enough. The load on the stabilizer is much like the load on the wing. With the cable placement=2C one third of the load is carried by the fuselage and the other two thirds are carried by the cables. The loading of the tail is less than the wing. I will use a very heavy load of 10 lb. sq. ft. for my example. The load on the tail moves the arm of the fuselage about the C. G. The sq. ft. load is 90"x 36" or less than 3240 sq .in. 3240/144= less than 22.5 sq.feet 22.5 sq. ft. x 10 lb per sq. ft. tail loading = 225 lbs max load on the tail. Of the 225 lbs. 1/3 carried by the fuselage or 85 lbs. 170 lbs are carried by the 4 wires. Four in tension on the fin=2C or four in tension on the fuselage. If you use a safety factor of 4 than each wire would carry 170 lbs. If you can hang off of one of your made up cables they are more than strong enough. And for vibration=2C a tight wire is much more likely to vibrate. These wires should not be that tight. They stop the deflection of the stabilizer and carry the load of the elevator. The back wire carries 1/2 the stabilizer plus the elevator=2C so the back wire carries more load that the front one. One back wire would carry the load fine but would not triangulate the stabilizer front to back. And while I'm on my soap box=2C I think T-88 is not so wonderful. I have made multiple test breaks and have seen at least four joint failures. T-88 can lay on top of the would and not penetrate. These breaks are most often spruce to ply. The glue pulling off the ply with a few splinters. I think I remember reading in their directions that it can be thinned to help with penetration=2C but then you lose that nice filet. Roughing the ply helps with this. Rambo=2C I was not saying to use a grade 3 bolt. lb for lb you should the strongest part. The way things are engineered on an aircraft isto use a part that is strong enough to do the job plus a safety factor. Other wise we would be using 3/4 inch bolts for everything. I still think SS bolts are stronger than they need to be for this application. Harmonic vibration is a separate problem to itself. Harmonic vibration and vibration are two different things. I really like Malcolm Morrison's way of saving 8 turnbuckles. I can make tail cables several times to get the right length and still save a gob of money. Howdy ________________________________________________________________________________Date: Thu, 7 Jan 2010 12:00:16 -0800 (PST)