Wizardprang,
I am building a model of the Japanese Val dive bomber which has an eliptical wing. The documentation drawings I have show a straight taper of the wing thickness and I designed my wing to reproduce that. I have built other models with eliptical planforms (Skyshark Val and Direct Connection Sea Fury) and they did have the curved spars. I have completely sheeted the left outer panel and the right one has the top sheeting on. The panels are 28" long and sheeted with 3/32 balsa. I did not have any problem with the compound curve. I did all my rib calculations as follows: I used actual numbers rather than percentages. There are 11 ribs. First I came up with the equation for the depth of each rib. Then from the plan view of the wing I measured the length of each rib in front of the spar and behind the spar. ( the proportions vary) I used a NACA 2315 airfoil becasue the high and low points are both at 30%-this makes it easy to build the spar system. I had the root airfoil in the CAD system I use at work-Vectorworks. For each front and back half of the rib I did a "scale object" with the height (y value) and length (x value) based on the proportions of calculated from the lengths(they were not the same). Seems to have worked out very well. Full-scale Val has either a 15.5% or 16% root airfoil (references vary) I used !5% becasue I had the coordinates. Turns out the tip is also very close to 15% thick. The ribs in between will be somewhat thinner as a percentage.
Chuck