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Wing ribs

PostPosted: Sat May 18, 2013 11:48 am
by flying2nc
To Make my cap strip pre bender I laid a piece of wax paper over the rib print {before I drilled any holes} traced it and cut it out then taped it to my remaining board halve and drew it on with a pencil,then went to about the wing CG and started there to put more bend in the airfoil as I went fore and aft, by the time I got to the leading edge I had about an 1" more curve to allow for springback and only had about 3/4" of an inch more at the trailing edge because there isn't as much curve or it's a gentler curve in the airfoil going aft.
I decided to use 1/4" cold rolled steel for my locator pins on the rib jig because the rib jig would never be exposed to the weather so the pins shouldn't rust. also the tolerances are close .003" close enough for what I am doing ALSO a 12 foot length at my local metal shop was only $7 + tax. I cut them into 2" lengths and knocked the edge off with a soft grinding wheel. Then drilled the rib jig board for where I wanted the locator pins. I thought I had done a good job in the placement of the pins leaving enough room to work around the vertical web pin locators but when gluing up my first rib found more room was needed to keep the epoxy from kicking around the pins on the top and bottom inside pins.!
After the epoxy kicked on the first rib, I had some one help me while I held the jig & spruce rib firmly,, and had them drive the pins out from the back! it didn't hurt the rib but there was a "click" when the epoxy broke loose from the pins,,,I re drilled the inside vertical web locator pins and moved them "inboard" approx, 3/4 to 1 inch, then glued 1/4" poplar wooden dowels in the old holes and lightly sanded them smooth . ( if your not making mistakes your not trying new things!)
Next rib came out great even used the same piece of wax paper.. "a little note" after trying a couple methods of putting wax paper on over the pins ,, I tried marking them with a marker and using a hole punch then tried planecrazzzy's method of burning them with a soldering iron over the pins but found the easiest for me was that if I flipped the jig over and weighted the wax paper with paper weights on the jig I had enough hole left over in the bottom to just stick the soldering iron in the hole threw the wax paper move it around a little ,perfect hole perfect fit.