Original Posted By: Ron Gipson
Subject: Pietenpol-List: Re: Rib strength & testing>Richard,>You can use one or two. Although remember the larger your>sample the more accurate your test.. If you test one, you>will know the results for that one. If you test two and>there is not a significant deviation, you have a better>answer. Remember, you can do NDT ("non-destructive>testing", also known as "quality control") just by bringing>the weight up to minimum numbers (for instance the 400 lbs>in my example) once you have satisfied yourself it will>hold, stop. If it fails before you reach the minimum,>wouldn't you rather know that on the ground? Decide what>you want to know. If you want to know how much weight the>rib can withstand, you have to take it to failure. If you>want to know if you have a good glue joint, then take it to>the minimum weight (personally, I would take it to min +20%,>it is known as a safety factor). By the way make sure you>use gross weight and not dry. Also don't fudge the>numbers. If the expected gross weight is 857 pounds, use>857. don't say " 857, let's call it 900 to be safe" it>compounds the problem . because if you use 900 then add a>safety factor of 20% you are now 30% above. I cringe at>this but.... but. Write a procedure. determine what you>want to do and write it down and how you plan to accomplish>this. Then give it to an engineer type and ask them to>review it, see if they concur. (I hope none of you work>with me, I could never live this down, suggesting you write>a procedure). One last thing, you don't have to test every>rib. If you are satisfied after doing "x" number without a>failure, assume they are all of that quality. (assuming you>don't change the process, i.e.. different glue, scuffing vs>not, etc.) Good luck and great website>>________________________________________________________________________________
Pietenpol-List: Rib strength & testing
Pietenpol-List: Rib strength & testing
Original Posted By: RdwdSgn(at)aol.com
I have actually run out of capstrip for the moment, having purchasedjust enough the last time I ordered, but I do have 2 spare ribs I canuse for testing. Does anyone have a method for testing single ribs? ortwo at a time? (can't do 4 just now).Finishing rib #28 tomorrow! RD---Bill Talbert wrote:>> Sorry guys, but i feel I have to put my two cents worth in> on this, too. Richard, if you are to do destructive> testing, do it right and controlled. I like the idea of> placing them on mock spars. But the dancing on the 2x4, I> don't. You want to establish if the ribs will safely carry> the wing loads. The 2x4 does not spread the load, it> concentrates it. You need to determine the load strength of> the wing. I don't recall what the wing is rated for, I> think it is +4 g's -1g. You can find it on Grant's page.> Then establish the wing loading (lbs/sqft). Now line the> ribs on the mock spars and cover them. You can use an old> bed sheet and probably latex paint. This is not important,> as you are trying to establish a minimum (threshold)> number. After the test bed is stretched, load the panel> with bags of sand. The amount of weight you add is a simple> calculation. e.g. if the loading is 5 lb/sqft, stressed 4g+> 1g- and you have a 20 sqft test area you load a minimum 400> lbs evenly across the surface. Actually you want to take it> beyond that. (You can keep adding weight till it fails and> then you know how well it is built). Another test you can> do is if you get to, say 500 lbs, remove the weight and flip> it over and try the other side. By all means, if it fails> prematurely, examine the pieces and identify the failure.> Now here is the kicker. If you look closely at the blue> prints, the ribs are designed to rest on the main spars,> the truss work on the ribs between the spars will make for a> very strong design. I would be curious where that rib> failed, but it may take a lot of sand. Piece of mind is> much better than pieces of debris on the ground. Remember,> you are going to bet your life on it.> > ==http://www.wrld.com/w3builderNow you can buy my CD at MP3.com:http://db.mp3.com/Visitor/order.php3?cd ... __________
I have actually run out of capstrip for the moment, having purchasedjust enough the last time I ordered, but I do have 2 spare ribs I canuse for testing. Does anyone have a method for testing single ribs? ortwo at a time? (can't do 4 just now).Finishing rib #28 tomorrow! RD---Bill Talbert wrote:>> Sorry guys, but i feel I have to put my two cents worth in> on this, too. Richard, if you are to do destructive> testing, do it right and controlled. I like the idea of> placing them on mock spars. But the dancing on the 2x4, I> don't. You want to establish if the ribs will safely carry> the wing loads. The 2x4 does not spread the load, it> concentrates it. You need to determine the load strength of> the wing. I don't recall what the wing is rated for, I> think it is +4 g's -1g. You can find it on Grant's page.> Then establish the wing loading (lbs/sqft). Now line the> ribs on the mock spars and cover them. You can use an old> bed sheet and probably latex paint. This is not important,> as you are trying to establish a minimum (threshold)> number. After the test bed is stretched, load the panel> with bags of sand. The amount of weight you add is a simple> calculation. e.g. if the loading is 5 lb/sqft, stressed 4g+> 1g- and you have a 20 sqft test area you load a minimum 400> lbs evenly across the surface. Actually you want to take it> beyond that. (You can keep adding weight till it fails and> then you know how well it is built). Another test you can> do is if you get to, say 500 lbs, remove the weight and flip> it over and try the other side. By all means, if it fails> prematurely, examine the pieces and identify the failure.> Now here is the kicker. If you look closely at the blue> prints, the ribs are designed to rest on the main spars,> the truss work on the ribs between the spars will make for a> very strong design. I would be curious where that rib> failed, but it may take a lot of sand. Piece of mind is> much better than pieces of debris on the ground. Remember,> you are going to bet your life on it.> > ==http://www.wrld.com/w3builderNow you can buy my CD at MP3.com:http://db.mp3.com/Visitor/order.php3?cd ... __________
Pietenpol-List: Re: Rib strength & testing
Original Posted By: jmcnarry(at)techplus.com (John McNarry)
Richard,You can use one or two. Although remember the larger yoursample the more accurate your test.. If you test one, youwill know the results for that one. If you test two andthere is not a significant deviation, you have a betteranswer. Remember, you can do NDT ("non-destructivetesting", also known as "quality control") just by bringingthe weight up to minimum numbers (for instance the 400 lbsin my example) once you have satisfied yourself it willhold, stop. If it fails before you reach the minimum,wouldn't you rather know that on the ground? Decide whatyou want to know. If you want to know how much weight therib can withstand, you have to take it to failure. If youwant to know if you have a good glue joint, then take it tothe minimum weight (personally, I would take it to min +20%,it is known as a safety factor). By the way make sure youuse gross weight and not dry. Also don't fudge thenumbers. If the expected gross weight is 857 pounds, use857. don't say " 857, let's call it 900 to be safe" itcompounds the problem . because if you use 900 then add asafety factor of 20% you are now 30% above. I cringe atthis but.... but. Write a procedure. determine what youwant to do and write it down and how you plan to accomplishthis. Then give it to an engineer type and ask them toreview it, see if they concur. (I hope none of you workwith me, I could never live this down, suggesting you writea procedure). One last thing, you don't have to test everyrib. If you are satisfied after doing "x" number without afailure, assume they are all of that quality. (assuming youdon't change the process, i.e.. different glue, scuffing vsnot, etc.) Good luck and great website________________________________________________________________________________
Richard,You can use one or two. Although remember the larger yoursample the more accurate your test.. If you test one, youwill know the results for that one. If you test two andthere is not a significant deviation, you have a betteranswer. Remember, you can do NDT ("non-destructivetesting", also known as "quality control") just by bringingthe weight up to minimum numbers (for instance the 400 lbsin my example) once you have satisfied yourself it willhold, stop. If it fails before you reach the minimum,wouldn't you rather know that on the ground? Decide whatyou want to know. If you want to know how much weight therib can withstand, you have to take it to failure. If youwant to know if you have a good glue joint, then take it tothe minimum weight (personally, I would take it to min +20%,it is known as a safety factor). By the way make sure youuse gross weight and not dry. Also don't fudge thenumbers. If the expected gross weight is 857 pounds, use857. don't say " 857, let's call it 900 to be safe" itcompounds the problem . because if you use 900 then add asafety factor of 20% you are now 30% above. I cringe atthis but.... but. Write a procedure. determine what youwant to do and write it down and how you plan to accomplishthis. Then give it to an engineer type and ask them toreview it, see if they concur. (I hope none of you workwith me, I could never live this down, suggesting you writea procedure). One last thing, you don't have to test everyrib. If you are satisfied after doing "x" number without afailure, assume they are all of that quality. (assuming youdon't change the process, i.e.. different glue, scuffing vsnot, etc.) Good luck and great website________________________________________________________________________________
Pietenpol-List: Re: Rib strength & testing
Original Posted By: Bill Talbert
Bill and Richard; Bill, I appreciate your sensible advice. It is what this list should beall about. The education and learning is as much fun as the flying. Wellalmost.
Just a side note: We are allowed to build our own airplaneshere, in Canada, for the purposes of recreation and education. Richard, the education is still going on, but the big question is are wehaving fun yet? I'll bet that answer is yes. Knowing that as you are flyingyour pretty bird with wings that are tested and true will be a comfortablefeeling. Recreating instead of worrying. I have built several parts over andbeen happier with the second go around. It seemed tough at first but thenwhen I do fly it I'll be working on pilotage not worrying if the wings orwhatever are going to fall off.If you do the NDT or decide to go all the way to failure, record the testand let us know what happens.John Mc-----Original Message-----
Bill and Richard; Bill, I appreciate your sensible advice. It is what this list should beall about. The education and learning is as much fun as the flying. Wellalmost.
Just a side note: We are allowed to build our own airplaneshere, in Canada, for the purposes of recreation and education. Richard, the education is still going on, but the big question is are wehaving fun yet? I'll bet that answer is yes. Knowing that as you are flyingyour pretty bird with wings that are tested and true will be a comfortablefeeling. Recreating instead of worrying. I have built several parts over andbeen happier with the second go around. It seemed tough at first but thenwhen I do fly it I'll be working on pilotage not worrying if the wings orwhatever are going to fall off.If you do the NDT or decide to go all the way to failure, record the testand let us know what happens.John Mc-----Original Message-----Pietenpol-List: Re: Rib strength & testing
Original Posted By:> Bill Talbert
Hi All!Here's my $.02 worth on ribs & testing!I found my copy of the 1962 FAA Basic Glider Criteria handbook - a lot ofgood info on figuring loads, etc. for flying machines in our speed range! There is a section that describes how to load a wing rib.If the wing fabric is attached by using rib stiching, the rib may be loadedon the bottom cap strip ( in the test the rib is mounted upside down onstub spars & the test loads are applied to the bottom cap strip) The loadsare to be 125% the ultimate air load (125% x 4 - 4.5 g's?) each rib willhandle (rib spacing x chord will give the sq. ft. each rib is supporting(1ft rib spacing x 5 ft chord = 5 sq ft x ult load per sq ft x 125% = loadper rib -- my math gave about 40.75 # sq. ft.-- 1050# gross / 145 sq ftwing area = 7.25# sq. ft. x 4.5 x 1.25) This is about 204# applied to yourtest rib! This load is divided up into (16) equal loads (12 3/4# each)that are applied at various points along the rib -- most of the points areon the front 1/2 of the rib. (i.e at .007, .02, .04, .063, .080, .114,.148, .185, .228, .272, .327, .38, .448, .528, .72, .9 the chord length) The loads can be applied to the rib thru 1" blocks to prevent localcapstrip faliure.Interesting stuff -- don't know how much of this load a Piet rib willhandle -- the test engineers I worked with always said that if the partdidn't break, the test wasn't a good one (it was better to have a failurethan not -- if the part survived, you didn't know if it was 5% or 200%stronger than it needed to be!) Mike ConklingPretty Prairie, KSP.S. My Model A engine is now in our barn -- it's a former combine engine! Pulled the head the other day & the cylinders look pretty good -- onlyabout .005 ridge to clean up at the cylinder top. It came with a WICOmagneto that is driven off the old spark distributer drive! Maybe we won'tneed to make a mag. drive off the end of the crank !?
Hi All!Here's my $.02 worth on ribs & testing!I found my copy of the 1962 FAA Basic Glider Criteria handbook - a lot ofgood info on figuring loads, etc. for flying machines in our speed range! There is a section that describes how to load a wing rib.If the wing fabric is attached by using rib stiching, the rib may be loadedon the bottom cap strip ( in the test the rib is mounted upside down onstub spars & the test loads are applied to the bottom cap strip) The loadsare to be 125% the ultimate air load (125% x 4 - 4.5 g's?) each rib willhandle (rib spacing x chord will give the sq. ft. each rib is supporting(1ft rib spacing x 5 ft chord = 5 sq ft x ult load per sq ft x 125% = loadper rib -- my math gave about 40.75 # sq. ft.-- 1050# gross / 145 sq ftwing area = 7.25# sq. ft. x 4.5 x 1.25) This is about 204# applied to yourtest rib! This load is divided up into (16) equal loads (12 3/4# each)that are applied at various points along the rib -- most of the points areon the front 1/2 of the rib. (i.e at .007, .02, .04, .063, .080, .114,.148, .185, .228, .272, .327, .38, .448, .528, .72, .9 the chord length) The loads can be applied to the rib thru 1" blocks to prevent localcapstrip faliure.Interesting stuff -- don't know how much of this load a Piet rib willhandle -- the test engineers I worked with always said that if the partdidn't break, the test wasn't a good one (it was better to have a failurethan not -- if the part survived, you didn't know if it was 5% or 200%stronger than it needed to be!) Mike ConklingPretty Prairie, KSP.S. My Model A engine is now in our barn -- it's a former combine engine! Pulled the head the other day & the cylinders look pretty good -- onlyabout .005 ridge to clean up at the cylinder top. It came with a WICOmagneto that is driven off the old spark distributer drive! Maybe we won'tneed to make a mag. drive off the end of the crank !?
Pietenpol-List: Re: Rib strength & testing
Original Posted By: Ken Beanlands
Michael,I have also found an old Model A engine form a combine. Is it the sameengine, same block etc. I wondered if it was the same engine and ok to us. Ididn't know how much of it was usable for a Piet. Where is Pretty Prairie at?I'm near Burlington. The engine I found had a coil and electric system. Tobad....Greg YotzMichael Conkling wrote:> Mike Conkling> Pretty Prairie, KS>> P.S. My Model A engine is now in our barn -- it's a former combine engine!> Pulled the head the other day & the cylinders look pretty good -- only> about .005 ridge to clean up at the cylinder top. It came with a WICO> magneto that is driven off the old spark distributer drive! Maybe we won't> need to make a mag. drive off the end of the crank !?>________________________________________________________________________________
Michael,I have also found an old Model A engine form a combine. Is it the sameengine, same block etc. I wondered if it was the same engine and ok to us. Ididn't know how much of it was usable for a Piet. Where is Pretty Prairie at?I'm near Burlington. The engine I found had a coil and electric system. Tobad....Greg YotzMichael Conkling wrote:> Mike Conkling> Pretty Prairie, KS>> P.S. My Model A engine is now in our barn -- it's a former combine engine!> Pulled the head the other day & the cylinders look pretty good -- only> about .005 ridge to clean up at the cylinder top. It came with a WICO> magneto that is driven off the old spark distributer drive! Maybe we won't> need to make a mag. drive off the end of the crank !?>________________________________________________________________________________
> Re: Rib strength & testing
Original Posted By: Ray Masters
> > Richard,> You can use one or two. Although remember the larger your> sample the more accurate your test.. If you test one, you> will know the results for that one. If you test two and> there is not a significant deviation, you have a better> answer. Remember, you can do NDT ("non-destructive> testing", also known as "quality control") just by bringing> the weight up to minimum numbers (for instance the 400 lbs> in my example) once you have satisfied yourself it will> hold, stop. If it fails before you reach the minimum,> wouldn't you rather know that on the ground? Decide what> you want to know. If you want to know how much weight the> rib can withstand, you have to take it to failure. If you> want to know if you have a good glue joint, then take it to> the minimum weight (personally, I would take it to min +20%,> it is known as a safety factor). By the way make sure you> use gross weight and not dry. Also don't fudge the> numbers. If the expected gross weight is 857 pounds, use> 857. don't say " 857, let's call it 900 to be safe" it> compounds the problem . because if you use 900 then add a> safety factor of 20% you are now 30% above. I cringe at> this but.... but. Write a procedure. determine what you> want to do and write it down and how you plan to accomplish> this. Then give it to an engineer type and ask them to> review it, see if they concur. (I hope none of you work> with me, I could never live this down, suggesting you write> a procedure). One last thing, you don't have to test every> rib. If you are satisfied after doing "x" number without a> failure, assume they are all of that quality. (assuming you> don't change the process, i.e.. different glue, scuffing vs> not, etc.) Good luck and great website________________________________________________________________________________
> > Richard,> You can use one or two. Although remember the larger your> sample the more accurate your test.. If you test one, you> will know the results for that one. If you test two and> there is not a significant deviation, you have a better> answer. Remember, you can do NDT ("non-destructive> testing", also known as "quality control") just by bringing> the weight up to minimum numbers (for instance the 400 lbs> in my example) once you have satisfied yourself it will> hold, stop. If it fails before you reach the minimum,> wouldn't you rather know that on the ground? Decide what> you want to know. If you want to know how much weight the> rib can withstand, you have to take it to failure. If you> want to know if you have a good glue joint, then take it to> the minimum weight (personally, I would take it to min +20%,> it is known as a safety factor). By the way make sure you> use gross weight and not dry. Also don't fudge the> numbers. If the expected gross weight is 857 pounds, use> 857. don't say " 857, let's call it 900 to be safe" it> compounds the problem . because if you use 900 then add a> safety factor of 20% you are now 30% above. I cringe at> this but.... but. Write a procedure. determine what you> want to do and write it down and how you plan to accomplish> this. Then give it to an engineer type and ask them to> review it, see if they concur. (I hope none of you work> with me, I could never live this down, suggesting you write> a procedure). One last thing, you don't have to test every> rib. If you are satisfied after doing "x" number without a> failure, assume they are all of that quality. (assuming you> don't change the process, i.e.. different glue, scuffing vs> not, etc.) Good luck and great website________________________________________________________________________________
> Re: Rib strength & testing
Original Posted By: arkiesacres(at)juno.com
> > Michael,> I have also found an old Model A engine form a combine. Is it the same> engine, same block etc. I wondered if it was the same engine and ok tous. I> didn't know how much of it was usable for a Piet. Where is PrettyPrairie at?> I'm near Burlington. The engine I found had a coil and electric system. To> bad....> > Greg Yotz> > Michael Conkling wrote:> > > Mike Conkling> > Pretty Prairie, KS> >> > P.S. My Model A engine is now in our barn -- it's a former combineengine!> > Pulled the head the other day & the cylinders look pretty good -- only> > about .005 ridge to clean up at the cylinder top. It came with a WICO> > magneto that is driven off the old spark distributer drive! Maybe wewon't> > need to make a mag. drive off the end of the crank !?> >> > ________________________________________________________________________________
> > Michael,> I have also found an old Model A engine form a combine. Is it the same> engine, same block etc. I wondered if it was the same engine and ok tous. I> didn't know how much of it was usable for a Piet. Where is PrettyPrairie at?> I'm near Burlington. The engine I found had a coil and electric system. To> bad....> > Greg Yotz> > Michael Conkling wrote:> > > Mike Conkling> > Pretty Prairie, KS> >> > P.S. My Model A engine is now in our barn -- it's a former combineengine!> > Pulled the head the other day & the cylinders look pretty good -- only> > about .005 ridge to clean up at the cylinder top. It came with a WICO> > magneto that is driven off the old spark distributer drive! Maybe wewon't> > need to make a mag. drive off the end of the crank !?> >> > ________________________________________________________________________________