The LEGO Saturn V is a fantastic kit. However, one thing I noticed right away was that the fins were wrong. THe fins with thkit look more like what was on the early Saturn IB rather than the Saturn V. THis build attempts to better replicate the original Saturn V fins.
One of the photos I have included shows the original LEGO fin (right) and my redesigned fin (left).
After printing, the first thing to do is remove the built in support for the fin. You can see in my photos where the edge of the fin should be. The support is thinner than the fin so use a set of small wire cutters and snip along the edge. Mine came of very clean.
I wanted my fins to be smooth like the LEGO fins so I sanded them down a bit then used some green hobby putty as filler then sanded again. I finished up with white home appliance paint and the finish ended up very close to the finish of the LEGO bricks.
Measurements taken from original photos and diagrams. Designed in Sketchup.