I started building a Saturn V model kit (1:144 scale) from Revell, and found the thruster assembly for the S-II booster to be a big disappointment. I also recently acquired and built a Prusa i3 MK3 3-d printer, so the timing was perfect. I decided to design a better replacement part. This is the first object I designed from scratch for 3-D printing. It was modelled in Tinkercad and printed in PLA at 0.15 mm.
In the photo below, the 3-d printed part is attached to the S-II assembly, and for comparison the original Revell part is also shown. Both have been painted. There is minimal surface prep of the 3-d print (i.e. no sanding, etc.), but it did get a coat of primer before painting.
Thanks to Tested videos, I learned a bit about weathering, which I applied to the thrusters. Weathering of the rest of the piece will have to wait until the whole rocket is assembled.
There are a few things I would change if I were to do it again. I made the pipes and some of the other features a little too small, and the instrument packages should be more wedge-shaped rather than rectangular. However, given the overall quality of the Revell model, I am more than satisfied with it.