Brodhead Pietenpol Association

Original Posted By: TXTdragger(at)aol.com
Unhappy with my first attempt at a spar jig, I threw it away and lofted thewing. I'm glad I did, because it allowed me to work through a few detailsand smooth the airfoil to my satisfaction.In making measurements for the spars and the internal rib braces, I'm faceto face with the problem of what to do with the extra space resulting fromusing a 3/4" spar instead of the 1" spar to which the rib drawings weremade. At this time I see five options:1. Leave it as is and position the spars against the aft vertical brace asindicated, leaving the 1/4" "free" space on the front edge of the spar.2. Position spar as indicated and adjust the forward and aft rib braceaccordingly to take up the 1/4" spacing.3. Move the spars and their single aft vertical brace the 1/4 inch frontand rear, thus increasing the distance between the spars from 27 3/4" to 281/4".4. Split the difference fore and aft for each spar and adjust the positionof the internal bracing accordingly.5. Leave spar and internal bracing as indicated but insert a secondvertical brace on the front edge of the spar and thus lock in the spar toeach rib. This is what appears to be done in the ribs offered byReplicraft.See http://www.replicraftaviation.com/piet%20qb%204.htmI like the last option. What say the rest of you builders out there?The archives are great, but I went through 114 rib messages without findingan answer before sending this.Thanks for your help.Michaelsylph(at)uswest.netPietenpol Rib Jig in Portland________________________________________________________________________________

Original Posted By: FordPiet(at)aol.com
Subject: Re: Pietenpol-List: 3/4" Spar Spacing in RibsIn a message dated 11/13/1999 11:33:26 AM Central Standard Time, sylph(at)uswest.net writes:>6. caulk it with 1/4" caulk (construction term) LOLJohn D (#10)________________________________________________________________________________

Original Posted By: Replicraft(at)aol.com
Subject: Re: Pietenpol-List: 3/4" Spar Spacing in RibsMichael-In answer to your rib question: If I were using the 3/4" spars I would keep the center to center distances the same as if using the 1" spar. This center to center dimension is carried down to the cabane mounts on the fuselage and on to the gear mounts. Do not move the spars forward or rearward, simply move your up-rights 1/8" on either side, rather than the full 1/4" on one side.Our ribs pictured in your reference, are for the 1" spars, not the 3/4"... I have simply added up-rights on both sides of the spars. We also add 1/2" square members on each side of the spar on the butt ribs only, to allow material to carve out for the fittings.SteveReplicraft Aviation________________________________________________________________________________

Original Posted By:> Sylph [SMTP:sylph(at)uswest.net]
Hi Michael,I kept the 27-3/4" measurement constant and just extended the plywooddoublers on the front side of the front spar and the rear side of the rearspars, but didn't add any extra vertical struts to the ribs (why addweight?). Even these doublers are probably not necesarybecause once thedrag wires are tight, the whole thing compresses against the uprights on theinternal side of the ribs. The doublers I added were loose enough to fitover the piece of spar material I included in my rib jig, but once the sparswere varnished, they were too tight and had to be sanded to allow the ribsto slip into place. Jack Phillips> -----Original Message-----