Original Posted By: Doug413(at)aol.com
I did a search on our archives for "box spar", and around 1999 thebuilders went over the subject. Message 9335 from Leo Ponton had dimensionsand more than what we recently talked about. Message #9338 had Jim WillsUK address, too. It sounded like he was selling plans at one time. In 1999 a Mike Bell talked about designing a box spar and having anengineer associate from work check everything when he finished. Is Mikestill here? It sounded like he had started something, anyway. In message 9304 a Joe Krzes said he had a "wood Handbook" that hadformulas for calculating dimensions.Kent________________________________________________________________________________
Pietenpol-List: Box / UK spars, some more info
Re: Pietenpol-List: Box / UK spars, some more info
Original Posted By: Larry Neal
Re: Pietenpol-List: Box / UK spars, some more info
Original Posted By: "Kent Hallsten"
Guys,Greg Cardinal and myself have all the books for designing the spar. Theproblem begins when we must have airfoil data to determine the chordwiseload distribution at various angles of attack. Max rear spar loading occusat some particlular AOA and max front spar loading occurs at another AOA.We then take these critical loads and multiply them by the load factor (Say4 G's) and a safety factor of 150 to 200 percent and come up with thedesign load on the spar.As Bernard Pietenpol designed the airfoil by trial and error, a wind tunneldetermined set of data has never been made available, to my knowledge. Weneed plots of Coefficients of Lift, Drag, pitching moments, etc., just likewhat shows up in the old NACA reports and the book, Theory of Wing Sections.I was hoping to find the time to build a useable either full size or scalemodel which could have been sent to Kip gardner when he was still working atOld Dominion U where he could talk someone into running the analysis intrade for a case of beer but he does not work there anymore.An I beam shaped spar, rather than a box shaped spar is more efficient asthe cap cross section would be the same whereas you would need, say ( as anexample only - do not use this thickness wood), only one 1/4 inch web versustwo 3/16" webs with the box spar. Savings would be substantial in that youwould be scarfing half the amount of wood, buying half (albeit thicker) thesquare footage of material, and you would have to carry two wingspan lengthsof 1/16 inch more material around so it the ship would weigh more.Also, a continuous spar from tip to tip is more efficient than a two pieceor three piece spar both from a structures standpoint and weight savingsstandpoint. The spar design could be made different for each and the singlepiece wing boys could enjoy the enhanced performance due to the weightsavings.Chris Bobka----- Original Message -----
Guys,Greg Cardinal and myself have all the books for designing the spar. Theproblem begins when we must have airfoil data to determine the chordwiseload distribution at various angles of attack. Max rear spar loading occusat some particlular AOA and max front spar loading occurs at another AOA.We then take these critical loads and multiply them by the load factor (Say4 G's) and a safety factor of 150 to 200 percent and come up with thedesign load on the spar.As Bernard Pietenpol designed the airfoil by trial and error, a wind tunneldetermined set of data has never been made available, to my knowledge. Weneed plots of Coefficients of Lift, Drag, pitching moments, etc., just likewhat shows up in the old NACA reports and the book, Theory of Wing Sections.I was hoping to find the time to build a useable either full size or scalemodel which could have been sent to Kip gardner when he was still working atOld Dominion U where he could talk someone into running the analysis intrade for a case of beer but he does not work there anymore.An I beam shaped spar, rather than a box shaped spar is more efficient asthe cap cross section would be the same whereas you would need, say ( as anexample only - do not use this thickness wood), only one 1/4 inch web versustwo 3/16" webs with the box spar. Savings would be substantial in that youwould be scarfing half the amount of wood, buying half (albeit thicker) thesquare footage of material, and you would have to carry two wingspan lengthsof 1/16 inch more material around so it the ship would weigh more.Also, a continuous spar from tip to tip is more efficient than a two pieceor three piece spar both from a structures standpoint and weight savingsstandpoint. The spar design could be made different for each and the singlepiece wing boys could enjoy the enhanced performance due to the weightsavings.Chris Bobka----- Original Message -----
Re: Pietenpol-List: Box / UK spars, some more info
Original Posted By: Larry Neal
Re: Pietenpol-List: Box / UK spars, some more info
Original Posted By: "Warren D. Shoun"
> Re: Pietenpol-List: Box / UK spars, some more info
Original Posted By: Matt Dralle
Living here in Western australia I shudder to think of the airfreight costs of a set of spruce wing spars on top of the spruce itself. (Check out the exchange rate for the Aussie dollar and you will see what I mean), so I am very interested in exploring any alternate means of fabricating spars. Just had another look at Mike Cuy`s video and it appears he used 1/2" spruce for the web with 1" x 1" spruce spar caps.Any thoughts on substituting the spruce web with one of ply ?Cheers,Rod W. Tail feathers finished, two Corvair engines sitting at the docks and 500 feet of rib cap on the way.>From: "Warren D. Shoun" >Reply-To: pietenpol-list(at)matronics.com>To: pietenpol-list(at)matronics.com>Subject: Re: Pietenpol-List: Box / UK spars, some more info>Date: Fri, 30 Nov 2001 21:09:10 -0800>>>>Spruce isn't even a "local" product. They buy it from here and the freight >charges>for long lengths are huge, so they need to get the most use out of a solid >spar. With>this method, 3 guys can make spars from one of ours. It was a design >driven by>economics, and approved by the PFA.>Cheers,>~Warren>>________________________________________________________________________________Date: Sat, 01 Dec 2001 00:29:46 -0800
Living here in Western australia I shudder to think of the airfreight costs of a set of spruce wing spars on top of the spruce itself. (Check out the exchange rate for the Aussie dollar and you will see what I mean), so I am very interested in exploring any alternate means of fabricating spars. Just had another look at Mike Cuy`s video and it appears he used 1/2" spruce for the web with 1" x 1" spruce spar caps.Any thoughts on substituting the spruce web with one of ply ?Cheers,Rod W. Tail feathers finished, two Corvair engines sitting at the docks and 500 feet of rib cap on the way.>From: "Warren D. Shoun" >Reply-To: pietenpol-list(at)matronics.com>To: pietenpol-list(at)matronics.com>Subject: Re: Pietenpol-List: Box / UK spars, some more info>Date: Fri, 30 Nov 2001 21:09:10 -0800>>>>Spruce isn't even a "local" product. They buy it from here and the freight >charges>for long lengths are huge, so they need to get the most use out of a solid >spar. With>this method, 3 guys can make spars from one of ours. It was a design >driven by>economics, and approved by the PFA.>Cheers,>~Warren>>________________________________________________________________________________Date: Sat, 01 Dec 2001 00:29:46 -0800