Original Posted By: Ted Brousseau
Hi all,I have been looking at Aircamper plans and notes, trying to figure out thebest dimensions for the spars. The origional used a 1" spruce spar, withthe web routed to 1/2". I have seen references to 3/4" spars (I don't knowif these are routed, or if they are spruce or fir). I plan on usingDouglas fir for my project, and want to use the size that makes sense. In the EAA Wood book, there is a section from Noel J. Becar titled"Selection and Evaluation of Wood". In this he describes the differencesbetween spruce, fir, and several other wood species. Using the formulas inthe book for weight and strength, I came up with the following numbers.Spar WeightWidth Height Routed Volume(ft) Spruce(lbs) Fir(lbs)Spar StrengthWidth Height Max load (spruce) Max load (fir)lbs and will support a total load of 83942 lbs. A 7/8" fir spar wouldweigh 40.25 lbs and support a total load of 85129 lbs. This is strongerand lighter that the 3/4" solid spar. So, it would seem that a 7/8" firspar, with a 7/16" routed web would be the best size to use for fir.Has anyone else looked at these numbers, or built a spar of this size? Anythoughts before the saw dust flys.Malcolm Morrison________________________________________________________________________________
Pietenpol-List: Spar Question
Pietenpol-List: Re: Spar Question
Original Posted By: "Larry L. Neal"
> Hi Malcolm: I went through a similar techie analysis of some of these items, and onceagain made a pilgrimage to one of my Mentor builders at Flabob airport near myhome. Please don't let the humor here seem disrespectful, but do you reallythink your body will be in any condition to care if you are under 82,000 poundsof stress or 83,000 pounds of stress (after you deduct the gross weight of theplane) It appears that the Piet is so over designed, that it really is agreat deal more important to pay close attention to the quality of yourassembly work, than it is to worry excessively about the material. (Yeah, Iuse salt when I eat my words guys). This thing is simply hell-for-stout, ifassembled correctly. Otherwise, it won't make any difference how good thematerial is. Warren________________________________________________________________________________
> Hi Malcolm: I went through a similar techie analysis of some of these items, and onceagain made a pilgrimage to one of my Mentor builders at Flabob airport near myhome. Please don't let the humor here seem disrespectful, but do you reallythink your body will be in any condition to care if you are under 82,000 poundsof stress or 83,000 pounds of stress (after you deduct the gross weight of theplane) It appears that the Piet is so over designed, that it really is agreat deal more important to pay close attention to the quality of yourassembly work, than it is to worry excessively about the material. (Yeah, Iuse salt when I eat my words guys). This thing is simply hell-for-stout, ifassembled correctly. Otherwise, it won't make any difference how good thematerial is. Warren________________________________________________________________________________
Pietenpol-List: Re: Spar Question
Original Posted By:> Malcolm Morrison
Hi Malcolm,Back in 1970 I was able to obtain some excellent Douglas Firthat was 3/4" x about 5 1/2" dimensionally. It had a nice edgegrain averaging about 12 to 15 annular rings per inch on the5 1/2" face. (I doubt one could easily find stuff like that today.)I elected to duplicate the original spar dimensions (1" x 4 3/4"I -beam) by thickness planing the webs to 1/2" and gluing 1/4"x 3/4" strips on each side, top and bottom. Filler blocks wereused at attachment points together with 3/32" Birch aircraft ply-wood plates. This arrangement has worked well (I'm still flyingthis a/c). I knew at the time it would be over-strength (and overweight, too) but had already built all the wing ribs to accept a1" thick spar, and the prospect of shimming them didn't appeal to me.I believe there are other places where one could save weightbesides reducing spar dimensions: eliminate the wooden leading edge with .020" 2024 T3 (not soft aluminum) wraparound, usethe same material for the trailing edge, and in the covering and finishing of the wing itself. Were I to build another Pietenpol, I definitely would do these things...and would build up aluminumalloy wing ribs using the same .020" 2024 T3 material as well.I have built a few samples of these ribs for the Pietenpol airfoiland they are extremely light and easy to fabricate...and I have used the same technique for thewing ribs on my Wag-A-Bond, with Martin clips to attach the fabric. Of course the purists won'tlike these changes, but I think BHP would not disapprove (methim back in 1982, and he seemed to be receptive to different ideas).Anyway, good luck with your project and I hope you enjoy yourPietenpol as much as I enjoy mine.Cheers,Graham Hansen
Hi Malcolm,Back in 1970 I was able to obtain some excellent Douglas Firthat was 3/4" x about 5 1/2" dimensionally. It had a nice edgegrain averaging about 12 to 15 annular rings per inch on the5 1/2" face. (I doubt one could easily find stuff like that today.)I elected to duplicate the original spar dimensions (1" x 4 3/4"I -beam) by thickness planing the webs to 1/2" and gluing 1/4"x 3/4" strips on each side, top and bottom. Filler blocks wereused at attachment points together with 3/32" Birch aircraft ply-wood plates. This arrangement has worked well (I'm still flyingthis a/c). I knew at the time it would be over-strength (and overweight, too) but had already built all the wing ribs to accept a1" thick spar, and the prospect of shimming them didn't appeal to me.I believe there are other places where one could save weightbesides reducing spar dimensions: eliminate the wooden leading edge with .020" 2024 T3 (not soft aluminum) wraparound, usethe same material for the trailing edge, and in the covering and finishing of the wing itself. Were I to build another Pietenpol, I definitely would do these things...and would build up aluminumalloy wing ribs using the same .020" 2024 T3 material as well.I have built a few samples of these ribs for the Pietenpol airfoiland they are extremely light and easy to fabricate...and I have used the same technique for thewing ribs on my Wag-A-Bond, with Martin clips to attach the fabric. Of course the purists won'tlike these changes, but I think BHP would not disapprove (methim back in 1982, and he seemed to be receptive to different ideas).Anyway, good luck with your project and I hope you enjoy yourPietenpol as much as I enjoy mine.Cheers,Graham Hansen
Pietenpol-List: Re: Spar Question
Original Posted By: stephen
Malcolm,Nice work on the calculations. You're on the right track. Keep in mind thatBernie's 1" spar was more like 15/16" since his measurments were to the kerf ofthe blade. A lot of people have made built up laminated spars. My suggestionfor built up spars would be to scarf all the joints in any one lamination andbe sure that the placement of these scarfs don't intersect with holes forfittings. A laminated spar would allow a one piece wing if you have the space.If you don't have the room, for weight savings, make a 2 piece wing includingthe center section with one half. That way you only have the weight of one setof attach fittings.Good luckMalcolm Morrison wrote:> Hi all,>> I have been looking at Aircamper plans and notes, trying to figure out the> best dimensions for the spars. The origional used a 1" spruce spar, with> the web routed to 1/2". I have seen references to 3/4" spars (I don't know> if these are routed, or if they are spruce or fir). I plan on using> Douglas fir for my project, and want to use the size that makes sense.>> In the EAA Wood book, there is a section from Noel J. Becar titled> "Selection and Evaluation of Wood". In this he describes the differences> between spruce, fir, and several other wood species. Using the formulas in> the book for weight and strength, I came up with the following numbers.>> Spar Weight>> Width Height Routed Volume(ft) Spruce(lbs) Fir(lbs)>> Spar Strength>> Width Height Max load (spruce) Max load (fir)>> >From these numbers it appears that the original spruce spars weigh 39.03> lbs and will support a total load of 83942 lbs. A 7/8" fir spar would> weigh 40.25 lbs and support a total load of 85129 lbs. This is stronger> and lighter that the 3/4" solid spar. So, it would seem that a 7/8" fir> spar, with a 7/16" routed web would be the best size to use for fir.>> Has anyone else looked at these numbers, or built a spar of this size? Any> thoughts before the saw dust flys.>> Malcolm Morrison--David B.Schober, CPEInstructor, Aviation MaintenanceFairmont State CollegeNational Aerospace Education CenterRt. 3 Box 13Bridgeport, WV 26330-9503(304) 842-8300________________________________________________________________________________
Malcolm,Nice work on the calculations. You're on the right track. Keep in mind thatBernie's 1" spar was more like 15/16" since his measurments were to the kerf ofthe blade. A lot of people have made built up laminated spars. My suggestionfor built up spars would be to scarf all the joints in any one lamination andbe sure that the placement of these scarfs don't intersect with holes forfittings. A laminated spar would allow a one piece wing if you have the space.If you don't have the room, for weight savings, make a 2 piece wing includingthe center section with one half. That way you only have the weight of one setof attach fittings.Good luckMalcolm Morrison wrote:> Hi all,>> I have been looking at Aircamper plans and notes, trying to figure out the> best dimensions for the spars. The origional used a 1" spruce spar, with> the web routed to 1/2". I have seen references to 3/4" spars (I don't know> if these are routed, or if they are spruce or fir). I plan on using> Douglas fir for my project, and want to use the size that makes sense.>> In the EAA Wood book, there is a section from Noel J. Becar titled> "Selection and Evaluation of Wood". In this he describes the differences> between spruce, fir, and several other wood species. Using the formulas in> the book for weight and strength, I came up with the following numbers.>> Spar Weight>> Width Height Routed Volume(ft) Spruce(lbs) Fir(lbs)>> Spar Strength>> Width Height Max load (spruce) Max load (fir)>> >From these numbers it appears that the original spruce spars weigh 39.03> lbs and will support a total load of 83942 lbs. A 7/8" fir spar would> weigh 40.25 lbs and support a total load of 85129 lbs. This is stronger> and lighter that the 3/4" solid spar. So, it would seem that a 7/8" fir> spar, with a 7/16" routed web would be the best size to use for fir.>> Has anyone else looked at these numbers, or built a spar of this size? Any> thoughts before the saw dust flys.>> Malcolm Morrison--David B.Schober, CPEInstructor, Aviation MaintenanceFairmont State CollegeNational Aerospace Education CenterRt. 3 Box 13Bridgeport, WV 26330-9503(304) 842-8300________________________________________________________________________________
Pietenpol-List: Re: Spar Question
Original Posted By: Ted Brousseau
It looks like the KERF OF PIETENPOL has struck again! Just Joking,Steve Yahn>Malcolm,>Nice work on the calculations. You're on the right track. Keep in mind that>Bernie's 1" spar was more like 15/16" since his measurments were to the kerf of>the blade. A lot of people have made built up laminated spars. My suggestion>for built up spars would be to scarf all the joints in any one lamination and>be sure that the placement of these scarfs don't intersect with holes for>fittings. A laminated spar would allow a one piece wing if you have the space.>If you don't have the room, for weight savings, make a 2 piece wing including>the center section with one half. That way you only have the weight of one set>of attach fittings.>>Good luck>>Malcolm Morrison wrote:>>> Hi all,>>>> I have been looking at Aircamper plans and notes, trying to figure out the>> best dimensions for the spars. The origional used a 1" spruce spar, with>> the web routed to 1/2". I have seen references to 3/4" spars (I don't know>> if these are routed, or if they are spruce or fir). I plan on using>> Douglas fir for my project, and want to use the size that makes sense.>>>> In the EAA Wood book, there is a section from Noel J. Becar titled>> "Selection and Evaluation of Wood". In this he describes the differences>> between spruce, fir, and several other wood species. Using the formulas in>> the book for weight and strength, I came up with the following numbers.>>>> Spar Weight>>>> Width Height Routed Volume(ft) Spruce(lbs) Fir(lbs)>>>> Spar Strength>>>> Width Height Max load (spruce) Max load (fir)>>>> >From these numbers it appears that the original spruce spars weigh 39.03>> lbs and will support a total load of 83942 lbs. A 7/8" fir spar would>> weigh 40.25 lbs and support a total load of 85129 lbs. This is stronger>> and lighter that the 3/4" solid spar. So, it would seem that a 7/8" fir>> spar, with a 7/16" routed web would be the best size to use for fir.>>>> Has anyone else looked at these numbers, or built a spar of this size? Any>> thoughts before the saw dust flys.>>>> Malcolm Morrison>>>-->>David B.Schober, CPE>Instructor, Aviation Maintenance>Fairmont State College>National Aerospace Education Center>Rt. 3 Box 13>Bridgeport, WV 26330-9503>(304) 842-8300>>________________________________________________________________________________
It looks like the KERF OF PIETENPOL has struck again! Just Joking,Steve Yahn>Malcolm,>Nice work on the calculations. You're on the right track. Keep in mind that>Bernie's 1" spar was more like 15/16" since his measurments were to the kerf of>the blade. A lot of people have made built up laminated spars. My suggestion>for built up spars would be to scarf all the joints in any one lamination and>be sure that the placement of these scarfs don't intersect with holes for>fittings. A laminated spar would allow a one piece wing if you have the space.>If you don't have the room, for weight savings, make a 2 piece wing including>the center section with one half. That way you only have the weight of one set>of attach fittings.>>Good luck>>Malcolm Morrison wrote:>>> Hi all,>>>> I have been looking at Aircamper plans and notes, trying to figure out the>> best dimensions for the spars. The origional used a 1" spruce spar, with>> the web routed to 1/2". I have seen references to 3/4" spars (I don't know>> if these are routed, or if they are spruce or fir). I plan on using>> Douglas fir for my project, and want to use the size that makes sense.>>>> In the EAA Wood book, there is a section from Noel J. Becar titled>> "Selection and Evaluation of Wood". In this he describes the differences>> between spruce, fir, and several other wood species. Using the formulas in>> the book for weight and strength, I came up with the following numbers.>>>> Spar Weight>>>> Width Height Routed Volume(ft) Spruce(lbs) Fir(lbs)>>>> Spar Strength>>>> Width Height Max load (spruce) Max load (fir)>>>> >From these numbers it appears that the original spruce spars weigh 39.03>> lbs and will support a total load of 83942 lbs. A 7/8" fir spar would>> weigh 40.25 lbs and support a total load of 85129 lbs. This is stronger>> and lighter that the 3/4" solid spar. So, it would seem that a 7/8" fir>> spar, with a 7/16" routed web would be the best size to use for fir.>>>> Has anyone else looked at these numbers, or built a spar of this size? Any>> thoughts before the saw dust flys.>>>> Malcolm Morrison>>>-->>David B.Schober, CPE>Instructor, Aviation Maintenance>Fairmont State College>National Aerospace Education Center>Rt. 3 Box 13>Bridgeport, WV 26330-9503>(304) 842-8300>>________________________________________________________________________________
Pietenpol-List: Re: Spar Question
Original Posted By: stephen
I agree the Piet is over designed but thought I would share one bit ofinformation that caught my attention last year at a Piet flyin. I met afellow that landed his Piet in the pine trees and lived to tell about it.It seems that things got a little turbulent and the next thing he knew wasthat he didn't have elevator control. So, down he went.Turns out the control horns (hope that is the correct terminology) comingout of the elevators were not made out of double thickness metal. When thegoing got a little rough they just gave up and bent over. So, the moral ofthe story is to make sure you have substantial control horns and keep an eyeon them to see that they aren't trying to bend over. Also, don't overcontrol the Piet if you find yourself in gusty conditions.Keep em flying - it took too long to build.Ted BrousseauNaples, FLGN-1>It appears that the Piet is so over designed, that it really is a>great deal more important to pay close attention to the quality of your>assembly work, than it is to worry excessively about the material.________________________________________________________________________________
I agree the Piet is over designed but thought I would share one bit ofinformation that caught my attention last year at a Piet flyin. I met afellow that landed his Piet in the pine trees and lived to tell about it.It seems that things got a little turbulent and the next thing he knew wasthat he didn't have elevator control. So, down he went.Turns out the control horns (hope that is the correct terminology) comingout of the elevators were not made out of double thickness metal. When thegoing got a little rough they just gave up and bent over. So, the moral ofthe story is to make sure you have substantial control horns and keep an eyeon them to see that they aren't trying to bend over. Also, don't overcontrol the Piet if you find yourself in gusty conditions.Keep em flying - it took too long to build.Ted BrousseauNaples, FLGN-1>It appears that the Piet is so over designed, that it really is a>great deal more important to pay close attention to the quality of your>assembly work, than it is to worry excessively about the material.________________________________________________________________________________
> Spar Question
Original Posted By: "Warren D. Shoun"
> > Hi all,> > I have been looking at Aircamper plans and notes, trying to figure outthe> best dimensions for the spars. The origional used a 1" spruce spar, with> the web routed to 1/2". I have seen references to 3/4" spars (I don'tknow> if these are routed, or if they are spruce or fir). I plan on using> Douglas fir for my project, and want to use the size that makes sense. > > In the EAA Wood book, there is a section from Noel J. Becar titled> "Selection and Evaluation of Wood". In this he describes the differences> between spruce, fir, and several other wood species. Using the formulasin> the book for weight and strength, I came up with the following numbers.> > Spar Weight> > Width Height Routed Volume(ft) Spruce(lbs) Fir(lbs)> > Spar Strength> > Width Height Max load (spruce) Max load (fir)> > >From these numbers it appears that the original spruce spars weigh 39.03> lbs and will support a total load of 83942 lbs. A 7/8" fir spar would> weigh 40.25 lbs and support a total load of 85129 lbs. This is stronger> and lighter that the 3/4" solid spar. So, it would seem that a 7/8" fir> spar, with a 7/16" routed web would be the best size to use for fir.> > Has anyone else looked at these numbers, or built a spar of this size? Any> thoughts before the saw dust flys.> > Malcolm Morrison> > ________________________________________________________________________________
> > Hi all,> > I have been looking at Aircamper plans and notes, trying to figure outthe> best dimensions for the spars. The origional used a 1" spruce spar, with> the web routed to 1/2". I have seen references to 3/4" spars (I don'tknow> if these are routed, or if they are spruce or fir). I plan on using> Douglas fir for my project, and want to use the size that makes sense. > > In the EAA Wood book, there is a section from Noel J. Becar titled> "Selection and Evaluation of Wood". In this he describes the differences> between spruce, fir, and several other wood species. Using the formulasin> the book for weight and strength, I came up with the following numbers.> > Spar Weight> > Width Height Routed Volume(ft) Spruce(lbs) Fir(lbs)> > Spar Strength> > Width Height Max load (spruce) Max load (fir)> > >From these numbers it appears that the original spruce spars weigh 39.03> lbs and will support a total load of 83942 lbs. A 7/8" fir spar would> weigh 40.25 lbs and support a total load of 85129 lbs. This is stronger> and lighter that the 3/4" solid spar. So, it would seem that a 7/8" fir> spar, with a 7/16" routed web would be the best size to use for fir.> > Has anyone else looked at these numbers, or built a spar of this size? Any> thoughts before the saw dust flys.> > Malcolm Morrison> > ________________________________________________________________________________