Original Posted By: "Jack Phillips"
Subject: Re: Pietenpol-List: wingtip bowIn a message dated 2/18/02 2:28:48 PM Pacific Standard Time, rambog(at)erols.com writes:> > Now for a different discussion: The plans state that the wingtip bow is> curved to match the centerline of the wing rib, which makes sense because> many tip bows do. HOWEVER, the tip bow on the Piet also serves as the > outer> compression rib. Is this another oops in the plans? I would think that > the> bow would have to be straight because it is a compression rib.> > Opinions??> > Gene> > > Gene,It does indeed act as a compression strut. It needs to be to the plans and will work just fine. I make mine (making a set now for the Scout) by laminating three pieces 1/3 inch x 1 inch to form a final 1x1. Doug Bryant________________________________________________________________________________
Re: Pietenpol-List: wingtip bow
Re: Pietenpol-List: wingtip bow
Original Posted By: Doug413(at)aol.com
Now for a different discussion: The plans state that the wingtip bow iscurved to match the centerline of the wing rib, which makes sense becausemany tip bows do. HOWEVER, the tip bow on the Piet also serves as the outercompression rib. Is this another oops in the plans? I would think that thebow would have to be straight because it is a compression rib.Opinions??Gene________________________________________________________________________________
Now for a different discussion: The plans state that the wingtip bow iscurved to match the centerline of the wing rib, which makes sense becausemany tip bows do. HOWEVER, the tip bow on the Piet also serves as the outercompression rib. Is this another oops in the plans? I would think that thebow would have to be straight because it is a compression rib.Opinions??Gene________________________________________________________________________________
RE: Pietenpol-List: wingtip bow
Original Posted By: owner-pietenpol-list-server(at)matronics.com
Hi Gene,You are correct, the wing tip is curved, and the wingtip is the outercompression member. I've never seen that done on any other plane. I tooworried a little about a curved compression member (at least you know whichdirection it is going to buckle), so I laminated my wingtips in the correctcurve. I made a form from a 2 x 4 cut to the centerline curve minus onehalf the tip thickness and used 1/4" laminations glued together withresorcinol. Man, are those tips stiff! Tony Bingelis tells how to laminatewood in one of his books, or it might be in the EAA Wood book. If you needdetailed instructions I can send them to you, or can scan the appropriatearticles (I got a scanner for Christmas).I had so much fun laminating those tips that I have done a bunch morelaminations in the plane, including the circular cutout I added to thecentersection, the landing gear struts, and some circular bows to reinforcethe instrument panels. Laminated parts are unbelievably rigid, and are verylight.Jack -----Original Message-----
Hi Gene,You are correct, the wing tip is curved, and the wingtip is the outercompression member. I've never seen that done on any other plane. I tooworried a little about a curved compression member (at least you know whichdirection it is going to buckle), so I laminated my wingtips in the correctcurve. I made a form from a 2 x 4 cut to the centerline curve minus onehalf the tip thickness and used 1/4" laminations glued together withresorcinol. Man, are those tips stiff! Tony Bingelis tells how to laminatewood in one of his books, or it might be in the EAA Wood book. If you needdetailed instructions I can send them to you, or can scan the appropriatearticles (I got a scanner for Christmas).I had so much fun laminating those tips that I have done a bunch morelaminations in the plane, including the circular cutout I added to thecentersection, the landing gear struts, and some circular bows to reinforcethe instrument panels. Laminated parts are unbelievably rigid, and are verylight.Jack -----Original Message-----
Re: Pietenpol-List: wingtip bow
Original Posted By: Kip & Beth Gardner
Re: Pietenpol-List: wingtip bow
Original Posted By:
That doesn't answer the question. Why would/should a compression strut becurved? The more you try to tighten the drag/antidrag wires, the more itwill bow.----- Original Message -----
That doesn't answer the question. Why would/should a compression strut becurved? The more you try to tighten the drag/antidrag wires, the more itwill bow.----- Original Message -----
Re: Pietenpol-List: wingtip bow
Original Posted By: Fisherman Caye
Re: Pietenpol-List: wingtip bow
Original Posted By: Fisherman Caye
Re: Pietenpol-List: wingtip bow
Original Posted By: "Michael Brusilow"
Jack and others:I also had reservations about the curved wingtip bow beingused as a compression member in the drag truss. And I wasalso a bit concerned about the rather long cantilevered por-tion of the wing beyond the lift strut attachment possibly lack-ing torsional rigidity, so I incorporated two 3/4 inch square spruce struts at the outboard tip rib, similar to the the parallelstruts at the lift strut fittings. The drag/antidrag cable attach-ment fittings are mounted at the centerline of the spars bet-ween these struts which butt against the spar flanges, and are held in place by 1/8 inch plywood gussets at the top and bot-tom spar surfaces. This, I hoped, would slightly increase thetorsional rigidity of the outboard portion of the wing and let the wingtip bow be just a "wingtip bow". In comparison with other Piets that use the wing tip bow as a compression member per the plans, I think my wing is slightlystiffer in torsion outboard from the lift struts, but this could be due to my use of Douglas fir for my spars. So the results areinconclusive at best.In the final analysis of all this, I don't think it was worthwhile be-cause it seems there has never been a problem with the wingas designed. Having a curved member loaded in compressionis contrary to sound engineering practice, but the outboard bayof the Pietenpol drag truss is lightly loaded in comparison withthe inboard bay and the curved tip has done the job well for along time. As I recall, the plans call for 3/32" cable bracing in bothbays; I used 1/8" cable for both, but now would go with 3/32" forthe outer and 1/8" for the inner.I laminated my tip bows in much the same way that Jack descri-bed and they have been completely satisfactory for 31(+) years.There are a few places where the design could be improved but,in my view, the wing tip bow-in-compression isn't one of them---especially when it is laminated. I built mine a long time ago, andexperience has taught me that I didn't have to second guess BHPin a lot places where I did so. Cheers,Graham Hansen (CF-AUN)________________________________________________________________________________
Jack and others:I also had reservations about the curved wingtip bow beingused as a compression member in the drag truss. And I wasalso a bit concerned about the rather long cantilevered por-tion of the wing beyond the lift strut attachment possibly lack-ing torsional rigidity, so I incorporated two 3/4 inch square spruce struts at the outboard tip rib, similar to the the parallelstruts at the lift strut fittings. The drag/antidrag cable attach-ment fittings are mounted at the centerline of the spars bet-ween these struts which butt against the spar flanges, and are held in place by 1/8 inch plywood gussets at the top and bot-tom spar surfaces. This, I hoped, would slightly increase thetorsional rigidity of the outboard portion of the wing and let the wingtip bow be just a "wingtip bow". In comparison with other Piets that use the wing tip bow as a compression member per the plans, I think my wing is slightlystiffer in torsion outboard from the lift struts, but this could be due to my use of Douglas fir for my spars. So the results areinconclusive at best.In the final analysis of all this, I don't think it was worthwhile be-cause it seems there has never been a problem with the wingas designed. Having a curved member loaded in compressionis contrary to sound engineering practice, but the outboard bayof the Pietenpol drag truss is lightly loaded in comparison withthe inboard bay and the curved tip has done the job well for along time. As I recall, the plans call for 3/32" cable bracing in bothbays; I used 1/8" cable for both, but now would go with 3/32" forthe outer and 1/8" for the inner.I laminated my tip bows in much the same way that Jack descri-bed and they have been completely satisfactory for 31(+) years.There are a few places where the design could be improved but,in my view, the wing tip bow-in-compression isn't one of them---especially when it is laminated. I built mine a long time ago, andexperience has taught me that I didn't have to second guess BHPin a lot places where I did so. Cheers,Graham Hansen (CF-AUN)________________________________________________________________________________