Brodhead Pietenpol Association

I purchased the full size rib print plans. I have read that there is a difference between the scaled blueprints and the full size rib. Does anyone have experience with the full sized print? How significant are these two?

Well, if you now have the full-size rib plan, the first thing you can do is compare the overall look and layout to readily-available rib layout plans like the one that's in the 1929 Flying & Glider Manual. Since the wing spars are what they are and they're spaced where they have to be on the airframe, you have those two fixed items to use to compare what the full-size rib plan shows. You also know the wing chord dimension, so there's another hard dimension that you can measure on your full-size rib plan. From there, it's just a matter of laying out the airfoil outline on the board that you'll be using to build your ribs on, and from there you just draw in the rib diagonals so everything joins up. It's hard to go very far wrong if you have the wing chord, the spar locations, and the geometry of the rib diagonals and verticals where they need to be.

What you may have heard about is the stationing, which is a list of dimensions of each point along the airfoil that you use to fair in the curve of the outline. There may be one or two of those station dimensions that are a little off such that if you try to connect the dots directly instead of just using a "best fit" smooth curve that lies between the points, there may be some points that are slightly offset. It's a rewarding and interesting afternoon exercise to set up a flat board about 6 ft long, draw in a base line representing the bottom reference of the airfoil, draw in the nose tip and tail lines, draw in the rectangles that represent the spars in their proper locations, and then start playing with the airfoil outline to get it to fit the known fixed points that you've laid out. Use slender sticks that you can bend to follow the curves so your pencil can follow them smoothly as you connect things up.

Oscar Zuniga
Medford, OR
Air Camper NX41CC, A75 power

I drew it out using the station measurements. I have photos here: https://imageevent.com/hatz/piet/ribs and video comparison here: https://youtu.be/rIYrQKmhiwU?si=JIIAtyhENT0dSgwr&t=120

Nice work.

Thanks Oscar and John. I appreciate your suggestions and insight.