Pietenpol-List: Rib CAD Dwgs
Posted: Fri Apr 16, 1999 1:22 pm
Original Posted By: Gary Gower
Group:I plotted the full size CAD drawing that I downloaded from Richards web page and added a couple of scales to confirm if the paper was stable (and my plotter was calibrated). We use high quality bond paper and also have vellum and mylar, but I was more concerned with the validity of the curve fitting to the points provided on the plans. Each CAD program interprets where to place the curve based on the "type" of curve fitting chosen. In this case, the generated line for the rib "fit" the first 5 points on the top and bottom, but then strayed dramatically as the distance between the points became greater.I assume that Mr. Pietenpol used a French Curve to generate the airfoil and picked some convenient points to get his measurements. To make a "true" Pietenpol, I guess you need to use the full scale rib layout that is included with the plans. What I can't confirm is if the CAD drawing will alter the flight characteristics. In reality, the only reason I can see to use the CAD is if you have a CNC router that you want to program to make a high-tech rib fixture.(I saw one, and it was neat)I guess the old adage is right, "If it ain't broke, don't fix it!"Doug ________________________________________________________________________________
Group:I plotted the full size CAD drawing that I downloaded from Richards web page and added a couple of scales to confirm if the paper was stable (and my plotter was calibrated). We use high quality bond paper and also have vellum and mylar, but I was more concerned with the validity of the curve fitting to the points provided on the plans. Each CAD program interprets where to place the curve based on the "type" of curve fitting chosen. In this case, the generated line for the rib "fit" the first 5 points on the top and bottom, but then strayed dramatically as the distance between the points became greater.I assume that Mr. Pietenpol used a French Curve to generate the airfoil and picked some convenient points to get his measurements. To make a "true" Pietenpol, I guess you need to use the full scale rib layout that is included with the plans. What I can't confirm is if the CAD drawing will alter the flight characteristics. In reality, the only reason I can see to use the CAD is if you have a CNC router that you want to program to make a high-tech rib fixture.(I saw one, and it was neat)I guess the old adage is right, "If it ain't broke, don't fix it!"Doug ________________________________________________________________________________