Original Posted By: AMsafetyC(at)aol.com
Subject: Pietenpol-List: perplexed at wood testing ?I have to wonder why anyone would need to test an 80 year old airfoil design thathas never (to my knowledge) had a failure ? I'm sure there is some satisfaction with finding out if you're ribs are built safelybut who of us has enough knowledge to even setup a proper scenario thatwould represent a realistic load on the rib ? Instead of doing all this fiddle-fartingaround I would rather just build my plane with a/c grade materialsand accepted practices and enjoy flying it. Just my opinion but unless you'rebuilding with knotty pine lumber and Elmer's glue you shouldn't really evenbe concerned with the strength of a Pietenpol wing rib. Mike C. ________________________________________________________________________________
Pietenpol-List: perplexed at wood testing ?
Re: Pietenpol-List: Re: Wood Options
Original Posted By: owner-pietenpol-list-server(at)matronics.com
Subject: Re: Pietenpol-List: Re: Wood OptionsNot that I have a desire to do loops or other aerobatic maneuvers in a Piet but you're saying the piet wing is good for 10Gs. In the overall is would be nice to kown what the aircraft as built to plans is capable of just as a matter of general information purposes and not something I would be willing to test through actual empirical methodology. Do we have a realistic stress value for the Piet, For discussion purposes and with no mathematical or engineering proof I have told people when asked it is estimated at 3.5 Gs positive and negative. If I have under or over estimated I would like to know what the real number is, again for no practical purpose other than discussion regarding the safety of the structure is all.JohnIn a message dated 9/29/2009 1:10:17 P.M. Eastern Daylight Time, eng(at)canadianrogers.com writes:Now THAT sounds like a well thought out, sound, engineering-based approach. I think everybody would appreciate a photo of that. Well, I would, anyway (even though it doesn't involve 1000 pounds of tractor weights or a small elephant balanced precariously atop the capstrip). Bill C. -----Original Message-----
Subject: Re: Pietenpol-List: Re: Wood OptionsNot that I have a desire to do loops or other aerobatic maneuvers in a Piet but you're saying the piet wing is good for 10Gs. In the overall is would be nice to kown what the aircraft as built to plans is capable of just as a matter of general information purposes and not something I would be willing to test through actual empirical methodology. Do we have a realistic stress value for the Piet, For discussion purposes and with no mathematical or engineering proof I have told people when asked it is estimated at 3.5 Gs positive and negative. If I have under or over estimated I would like to know what the real number is, again for no practical purpose other than discussion regarding the safety of the structure is all.JohnIn a message dated 9/29/2009 1:10:17 P.M. Eastern Daylight Time, eng(at)canadianrogers.com writes:Now THAT sounds like a well thought out, sound, engineering-based approach. I think everybody would appreciate a photo of that. Well, I would, anyway (even though it doesn't involve 1000 pounds of tractor weights or a small elephant balanced precariously atop the capstrip). Bill C. -----Original Message-----
Pietenpol-List: Re: perplexed at wood testing ?
Original Posted By: "899PM"
I would be concerned about a -3.5G load on the lift strutson my airplane. Let's use very quick, rough, and conservativenumbers and say that the airplane is at gross, using arough 1100 lb. max gross. Under 3.5G loading, that's 3850 lbs.and if we get really rough and say each of the four lift strutsis sharing that load equally (not even close to the actualcondition, but let's just say)- that's nearly 1000 lbs. thateach of the lift struts sees in compression loading. The jurystruts provide resistance against buckling failure in one mode,but even at that- I would feel very iffy about that kind ofloading, particularly if there was any buffetting going on.The attach bolts would be fine, even the ones at the wing- ifI recall, those are AN4 and in double shear, so with a shearstrength of 76000 psi, they should be good for something like7000 lbs. each.I believe I've heard it said that there has never been acatastrophic structural failure of a Piet. Knowing how many ofthem have flown and are flying, and how many zillions of peoplehave piloted them through all sorts of conditions, I think it'ssafe to say that you really have to mistreat one to breaksomething structural on them.And that's probably about as close as you're going to get to anengineering analysis of the ultimate load rating on the airframeunless someone wants to model it with a finite element analysisor something sharper than a hardware-store yardstick.Oscar ZunigaAir Camper NX41CCSan Antonio, TXmailto: taildrags(at)hotmail.comwebsite at http://www.flysquirrel.net ________________________________________________________________________________Subject: Pietenpol-List: Re: perplexed at wood testing ?
I would be concerned about a -3.5G load on the lift strutson my airplane. Let's use very quick, rough, and conservativenumbers and say that the airplane is at gross, using arough 1100 lb. max gross. Under 3.5G loading, that's 3850 lbs.and if we get really rough and say each of the four lift strutsis sharing that load equally (not even close to the actualcondition, but let's just say)- that's nearly 1000 lbs. thateach of the lift struts sees in compression loading. The jurystruts provide resistance against buckling failure in one mode,but even at that- I would feel very iffy about that kind ofloading, particularly if there was any buffetting going on.The attach bolts would be fine, even the ones at the wing- ifI recall, those are AN4 and in double shear, so with a shearstrength of 76000 psi, they should be good for something like7000 lbs. each.I believe I've heard it said that there has never been acatastrophic structural failure of a Piet. Knowing how many ofthem have flown and are flying, and how many zillions of peoplehave piloted them through all sorts of conditions, I think it'ssafe to say that you really have to mistreat one to breaksomething structural on them.And that's probably about as close as you're going to get to anengineering analysis of the ultimate load rating on the airframeunless someone wants to model it with a finite element analysisor something sharper than a hardware-store yardstick.Oscar ZunigaAir Camper NX41CCSan Antonio, TXmailto: taildrags(at)hotmail.comwebsite at http://www.flysquirrel.net ________________________________________________________________________________Subject: Pietenpol-List: Re: perplexed at wood testing ?
Original Posted By: "Dave Abramson"
Mike,All good points. I originally tested a wing rib to 1) Like Ken, give me a warm and fuzzy that myt-88 gluing was up to snuff and 2) to prove to others(on this list 11 years ago)that the Piet rib per plans is built like the proverbial brick crap-house.You may remember that healthy debate. Few of the "old timers'" with the bulkof the knowledge were(or are) on the web to defend the design and LOTS of goodintentioned folks were probably scared off from the remarks of some non-buildingknow-it-alls. I have a fairly healthy wooden wing rib collection. None are built as heavily asthe Piet...not even the Ford built Waco GC-4A glider ribs. An example of lightnesson the other end is the Porterfield CP-50 rib. Slightly less than 1/4"square.--------PAPA MIKERead this topic online here:http://forums.matronics.com/viewtopic.p ... __________
Mike,All good points. I originally tested a wing rib to 1) Like Ken, give me a warm and fuzzy that myt-88 gluing was up to snuff and 2) to prove to others(on this list 11 years ago)that the Piet rib per plans is built like the proverbial brick crap-house.You may remember that healthy debate. Few of the "old timers'" with the bulkof the knowledge were(or are) on the web to defend the design and LOTS of goodintentioned folks were probably scared off from the remarks of some non-buildingknow-it-alls. I have a fairly healthy wooden wing rib collection. None are built as heavily asthe Piet...not even the Ford built Waco GC-4A glider ribs. An example of lightnesson the other end is the Porterfield CP-50 rib. Slightly less than 1/4"square.--------PAPA MIKERead this topic online here:http://forums.matronics.com/viewtopic.p ... __________
RE: Pietenpol-List: perplexed at wood testing ?
Original Posted By: "Bill Church"
RE: Pietenpol-List: Air Camper load rating
Original Posted By: owner-pietenpol-list-server(at)matronics.com
Greetings all!There has been at least 1 catastrophic wing failier on a Pietenpol....In Chet Peeks book..... There is a story of someone doing aerobatics, andhis Pietenpol fell apart in the air. (back in the 20's or 30's)Just wanted to throw that out there!Dave-----Original Message-----
Greetings all!There has been at least 1 catastrophic wing failier on a Pietenpol....In Chet Peeks book..... There is a story of someone doing aerobatics, andhis Pietenpol fell apart in the air. (back in the 20's or 30's)Just wanted to throw that out there!Dave-----Original Message-----
Re: Pietenpol-List: perplexed at wood testing ?
Original Posted By: Rados Svagelj
RE: Pietenpol-List: these West Coast guys -- FUEL TANKS
Original Posted By:> timothywillis(at)earthlink.net
vinyl ester resin is compatable with av gasDoug DeverIn beautiful Stow Ohio> Date: Tue=2C 29 Sep 2009 09:36:29 -0500
vinyl ester resin is compatable with av gasDoug DeverIn beautiful Stow Ohio> Date: Tue=2C 29 Sep 2009 09:36:29 -0500
RE: Pietenpol-List: perplexed at wood testing ?
Original Posted By: "Bill Church"
> Re: Pietenpol-List: perplexed at wood testing ?
Original Posted By:> ken@cooper-mtn.com
You don't need toapproximate loading. All you need to do is see if the wood failed or the glue joint failed first. The method of destruction doesn't really matter.Doug DeverIn beautiful Stow Ohio> To: pietenpol-list(at)matronics.com> Subject: Re: Pietenpol-List: perplexed at wood testing ?> Date: Tue=2C 29 Sep 2009 12:18:04 -0600
You don't need toapproximate loading. All you need to do is see if the wood failed or the glue joint failed first. The method of destruction doesn't really matter.Doug DeverIn beautiful Stow Ohio> To: pietenpol-list(at)matronics.com> Subject: Re: Pietenpol-List: perplexed at wood testing ?> Date: Tue=2C 29 Sep 2009 12:18:04 -0600