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“For most parts we had made, I would estimate we saved a multiple days and hundreds of dollars over other [conventional] options."

Project Challenge: A Motor for Any Board

The project goal was to manufacture an electric motor-propeller assembly that mounts into nearly all small watercraft from SUP’s to kayaks and canoes, using interchangeable attachment mounts.

“We wanted to create a dynamic motor and propeller assembly which can attach to any board of any brand,” explains Mike Radenbaugh, president of Current Drives. “We set out to create lightweight fin and propeller that was easy to attach in very little time.”

The original propeller system, shown below, has been out on the market for a few years. Radenbaugh’s design team relied on 3D printed prototypes to test fit and function of propeller assemblies.

3D Printing Hydrodynamic Propellers

The latest offering, a folding propeller that can be used on all ElectraFin conversion kits, will be available for purchase this spring at www.currentdrives.com. This new propeller provides users with improved run times and top speeds thanks to the optimized hydrodynamic design. This propeller also features a unique folding operation which reduces drag when users are paddling. The blades can also be locked in place whenever increased reverse thrust is desired.

To bring their new propeller and fin assembly to the SUP community, Current Drives relied on 3D printing and machining from Stratasys Direct Manufacturing throughout their iterative design process. They chose Fused Deposition Modeling (FDM), Stereolithography, PolyJet, CNC Machining and glass-filled nylon Laser Sintering (LS) to prototype the new propeller. Current Drives took the 3D printed LS parts on the water to see how well the new design functioned in the real world.

The 3D printed nylon propeller and hub were created with Laser Sintering. Current Drives chose Glass-filled nylon 3D printed prototypes because of the excellent mechanical stiffness and dimensionally stability, properties which aided in repeated water tests at full speed for prolonged periods. You can learn more about how to design for LS in our latest free white paper, “An Insider’s Guide to Laser Sintering”.

“The engineers at Stratasys Direct Manufacturing recommended materials and processes that would work well with our functional testing requirements,” says Radenbaugh. “Our design utilizes threaded inserts in order to lock the folding propeller for enhanced reverse thrust, and they were able to install these components for us in-house before shipping the parts.”

In addition to the functional LS and FDM prototypes, Current Drives 3D printed Stereolithography ID-Light models with a solid outer surface and scaffolding-like internal structure for tighter tolerance fit-checks. The primed surfaces of the Stereolithography parts gave a nice aesthetic reveal as well for design verifications during early concept modeling. The final assemblies use injection molding and an impact tough copolymer polycarbonate.

The idea is that with the ElectraFin® paddle assist™ technology, riders can face stronger head winds and currents and stay out on the water longer. And, of course, it helps the less experienced paddlers keep up with SUP enthusiasts and SUP rental shops to improve the experience for their patrons.  The ElectraFin is also celebrated as an effective tool for SUP and Kayak fisherman, helping sportsman get into prime fishing locations swiftly and silently.

Results: Smooth Sailing

Radenbaugh notes that the main advantages to outsourcing 3D printed prototypes is fast turnaround, quality and solid guidance on materials and post-processing. “For most parts we had made, I would estimate we saved a multiple days and hundreds of dollars over other [conventional] options. For a tech startup with numerous product enhancements coming out each season, saving even a few days on a development project can make all the difference.” states Radenbaugh. But the real savings are in the time and ease of use the final ElectraFin assembly offers to SUP users. “Our conversion kits mount in less than a minute on almost all existing paddleboards and new paddleboards from all major SUP manufacturers. This enables new and experienced paddlers to enjoy the benefits of high performance and silent electric propulsion on their favorite boards” says Radenbaugh.