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I haven't yet found the perfect adjustable boom band, so of course decided to 3D print my own. The general design is illustrated below, well chamfered and rounded to avoid snagging lines or sheets. The key features are a brass heat set threaded insert and a counterbore for the screw head. The filament is white ASA to provide some degree of defence against outdoor conditions, ie UV degradation. I use a 0.4 mm nozzle on my Prusa Mk4S and a 0.1 mm, 0.15 mm, or 0.2 mm layer height. Slice the band on its side with the boom bore vertical, this layers the filament on the major load path. Use 100% infill. It prints easily on a prepared build plate (ie some PVA glue like Pritt or Elmers, or Magigoo) and no need for a brim. A little tedious, but I print one at a time. (Prusa slicer has a setting which prints a collection of bands one at a time, but I've not tested it yet.) The opening and counterbore for the screw may need a little cleaning up after printing. I've found no need to clean up the heat set insert opening, it'll do that job itself while being inserted.
The band comes in two types, one for an attachment relatively further away from the boom such as the sail clew (on the left), and one for an attachment relatively close to the boom such as the sail tack or sheeting eye (on the right). If used as a sheeting eye (or any other use, really), it is a good idea to waist the screw -- smooth off the screw threads in the centre part of the screw -- to reduce fraying. The "clew" band carries the screw 7 mm off the boom and is a little thinner in its upper part to allow the clew of the sail to rotate some to port or starboard. The "tack" band carries the screw 4 mm off the boom and is a little thicker in its upper part. The band comes in three "weights". The light band is 6 mm wide, 1.6 mm thick around the boom (4 layers with 0.4 mm nozzle), and uses an M1.6 x 12 screw (and associated M1.6 heat set insert). The medium band is 8 mm wide, 2 mm thick (5 layers), and uses an M2 x 12 screw. The heavy band is 10 mm wide, 2.4 mm thick (6 layers), and uses an M2.5 x 12 screw. Finally, the band is sized for 10 mm or 12 mm diameter booms. The STL files are downloadable:
"Tack" M1.6 10
mm Ø
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©2025 Lester Gilbert |
