If you haven’t noticed the influx of young and hip stand up paddle boarders gliding across oceans and lakes, bedecked in fashionable swimwear and trendy sunglasses, you clearly haven’t been near any substantial body of water for a good decade. Stand up paddle boarding, or SUP, has seen an increase in popularity, with an estimated 3 million outdoor enthusiasts partaking in the water activity yearly. It attracts both young and older crowds looking for a more leisurely way to get around in the water. SUP doesn’t demand the kind of high level of athleticism associated with surfing or kayaking, although don’t let that lull you into a false sense of superiority; unless you’re naturally gifted with perfect balance and decent quad muscles, expect to fall off frequently while you’re learning the ropes.
The sport might look relaxing, but think of it more as bridging the divide between those who want to burn some serious calories and folks looking to get a little exercise while enjoying a lake or sunny beach. Closing that divide further is Current Drives, a company that manufactures electric motors for stand up paddle boards, kayaks and canoes. The Current Drives ElectraFin® can maintain a cool speed of 5 mph for two hours or much longer at reduced speeds. It allows those of us with less experience to keep up with our veteran SUP friends, and aids the more serious SUP boarders and fisherman who are more likely to be out battling stronger winds and currents, thanks to a little extra push from the ElectraFin propeller.
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.
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, and glass-filled nylon Selective Laser Sintering (SLS) to prototype the new propeller. Current Drives took the 3D printed SLS 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 Selective 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 SLS in our latest free white paper, “An Insider’s Guide to Selective 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 SLS 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.
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.
