3D Printed Boat


3d printed boat teamI tip my hat (were I wearing one) to the University of Washington mechanical engineering students who entered Denny’s 42nd Annual Seafair Milk Carton Derby with a 3-D printed raft. This contest requires participants to fabricate a boat whose buoyancy comes from empty paper or plastic milk cartons. As it was not explicitly prohibited, the students interpreted the rules of the competition to mean the milk cartons could be in any condition or shape, so long as they were the only source of buoyancy force for the craft they… crafted.

3d printed boat printerThe students fabricated a custom large-format 3D printer from what seems to be an old Torchmate sheet-cutting table. The 3rd axis being attached to the X-Y gantry and fitted with an extruder system for the HDPE material. The old plastic milk jugs were shredded and fed into the extruder which built the raft layer-by-layer according to some CAD model or maybe hand-written G-code (eeekk!).

3d printed boat printing

What did this smell like?

The process of building the printer and printing a usable boat, according to the team’s blog, took about 10 weeks. And they still only finished it the day before the race. Having competed in a few similar constructive competitions in my school days, I think D-day-minus-1 is the only time collegiate teams are allowed to finish build projects… it must be in the rules or something.

3d printed boat closeup

HDPE SKEET

Trouble at the Derby

There was some confusion amongst the derby’s organizers about in which class to let the 3D printed boat race. As I read the rules, the raft should have been put into the Adult Racing category as the boat was engineered with a streamlined hull shape for speed. But instead, the University of Washington’s entry was put into the Adult Open category.

The open class is reserved for “entries where design took precedence over speed in the construction”. In other words, the open class is for bedazzled floats manned by half serious seamen body-painted in their favorite team’s colors, while the racing class is for competitive entries. Washington’s entry certainly belongs in the latter.

Atop this confusion, they placed an “unofficial second” in this open class. Unofficial? Were the organizers not watching when the boats crossed the finish line? I’m not sure what this was all about, but their blog does make small mention here:

Finally, Thank You Seafair. We threw you a curveball and we appreciated you working with us and allowing us to go out and play and show the public a new form of recycling.

So it sounds like Seafair thought UW bent the rules (cheated) by melting the cartons down to build a real boat, and wouldn’t let them officially compete in the race class. Chumps. I feel bad for the students; engineering is all about problem solving, and responsible engineers will identify the goals, analyze the rules, and formulate the best solution. Fabbers at UW: you did just that. I applaud your efforts, your methodology, and your execution. I am sorry your engineering problem solving skills were denied the validation they deserved: winning that race.

About Ed

This Engineering Dude is a contract Mechanical Engineer with 12 years experience in comprehensive electro-mechancial product design. His consumer and OEM products have been sold worldwide in the laboratory, medical, clinical, and research markets. He has also designed orthopedic rehabilitation hardware, firearms, pneumatic weapons, mountain bikes, and even furniture.
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