Inspired by similar design I made this in 3D studio max using a shape and the loft modifier as it allows detailed control over scaling, rotating etc.

I made this to test printing with larger nozzles and have successfully printed it in 100 and 120% with a 0,60 nozzle and and 0,3 mm layer height and 70% with 0,40mm

Print with 4-6 bottom layers, 2-3 outline, no infill, no top layers.

complete water tightness is a bit hit n miss so to be sure I painted the planters on the inside.

2018 July 17 - made some variations with more and finer fins optimized for 0.40 mm nozzle https://www.thingiverse.com/thing:3009293 https://www.thingiverse.com/thing:3009294 https://www.thingiverse.com/thing:3009295 https://www.thingiverse.com/thing:3009296 https://www.thingiverse.com/thing:3009297

2018 July 24 Made some more designs fluted vase 40 cm high https://www.thingiverse.com/thing:3018290

fluted planters https://www.thingiverse.com/thing:3018316 https://www.thingiverse.com/thing:3018321

2018 August 7 Prototype concrete mold for fluted planter https://www.thingiverse.com/thing:3039055