Monday, February 17, 2014

The Design and Development of the Native Watercraft Slayer Propel Fishing Kayak

Initial Drawings of the Slayer Propel 13
The Development of the Slayer Propel 13 really started when Native Watercraft first developed the pedal drive Propel system in 2008.  I had just joined the Native Watercraft design team so I hadn't had any input on the beginnings of this concept and design.  In the few times that I pedaled the Mariner Propel I could feel the potential and I got really excited about designing the newest addition to the Slayer line of fishing kayaks in 2013.  As we began to work on the Propel, we started to really understand that the advantages of using your legs were not limited to the power of larger muscle groups to do the work: pedaling also leaves your hands free to fish, and the more you fish the more you catch (well sometimes). Beyond that, we also found two more advantages of having a bike-like motion to drive the propeller. The motion itself is familiar and easy to maintain, as most of us have pedaled bikes.  By simply pedaling in reverse you can drive the boat backwards which plays a huge role in fishing. Pedaling facilitates actions that every angler needs to do, like approaching a structure, stopping, and pulling large fish out of tight areas and from under obstructions.

Native Watercraft Pro Staffer Philip Ruckart Slayin'em.

We started initial conversations about the new Propel design with Native Watercraft guides and pro staff. It was agreed across the board that the traditional paddled Slayer kayak would be a good place to start. We even had folks on the Native Watercraft Facebook page asking for a propel driven Slayer before we were even really sure we were gonna do it! Everyone thought that the open floor plan, 360 degree accessory track coverage, superior stability, and efficient paddling hull of the Slayer would make for an ideal platform to install our Propel System. What we came to realize over time was that it wasn't just a fishing kayak we now understand that it's a great boat for cruising out on the water for any reason at all.

Another view of the Slayer Propel 13 and the seat slider attachment.

We focused first on hull design because the hull does have to be adjusted quite a bit to accept the propel drive unit. We spent a lot of time looking at how the water flowed across the hull and into and around the propeller. One of the challenges was getting the prop to engage completely and more efficiently with the water while keeping it tucked up against the hull to minimize the depth of water needed for the prop to run. After our first prototype, we had a bit of aeration during hard pedaling, so we did some old school plastic welding to form different curves to change the flow of water into the propel cavity. Not only did the changes create more power and speed, they also decreased water noise.

Welding in new hull curves.

The rest of the hull design balances traits of efficiency and stability. Too wide and you start to really hinder speed and make more noise by having to push a wider hull through the water. Too narrow and the boat will become unstable when it loses buoyancy on either side of the paddler. So it is important to prioritize the desired performance characteristics. In the Slayer Propel, we wanted to create a boat stable enough to stand in easily, but that would still move through the water as smoothly and quietly as possible to take advantage of the speed of the Propel System and maintain the ability to paddle the boat as well. The Slayer Propel is 33" wide, so by no means a sea kayak (which are sub 24 inches), but it is much more stealthy than other fishing-specific pedal-driven boats. We started at the bow with as sharp an entry as we could while still maintaining the large front storage tank. Smoothly curved, large pontoons drop down into the water through the mid section of the boat to provide a ton of stability and a quieter ride. Without the pedal-drive system, we have found that this hull paddles well with a kayak paddle. We feel as though we have come up with a confidence-inspiring hull design that complements the Propel system.

Testing the stability of the very first Slayer Propel prototype.
Hips slightly above the crank spindle.
 Ergonomics provided a key focus in this design as well. We knew we had to integrate our First Class seat. Not only did we want people to be more comfortable while pedaling, we wanted them to be able to pedal for longer durations and be more efficient while doing it. We tested many different people's leg lengths, weights, heights, and pedaling styles, and found that sitting up higher in the Slayer with the head of the femur at the same height or higher than the crank spindle (the axle that goes through the top of the unit) allowed pedalers to relax and sit more upright. We created a sliding rail system that adjusts by simply loosening two thumbscrews and sliding down the rails to the desired position to adjust to different leg lengths and pedaling postures. 

Testing different crank arms, pedals, and seat heights.
Another aspect of the pedaling ergonomics that we tested extensively was the length of the crank arm (what the pedals attach to). Normal upright bikes use something around 175mm crank arms. In our older propel models we had used 165mm crank arms but in our testing were getting an uneven pressure during the rotation of the pedals. We found that the 155mm cranks evened out the rotation pressure, eliminated the feeling that our knees were in our chest, and still gave us plenty of leverage to drive the prop. During tests, I did several long pedals ranging from 2 to 10 miles. Once we switched to the shorter cranks I found that I could maintain 3 - 3.5 miles an hour for extended periods and still have plenty of energy to get the boat up to 4.5 or even 5 miles an hour and hold it for 5 to 10 minute durations.

Propel Testing Tank
Last but not least the Propel drive unit has gone through extensive testing and transformation over the past couple years.  We brought in house a former bicycle industry designer and engineer to focus on the continued improvement of the Propel drive.  We have put the unit through long hours of submersion testing at our facility and the resident gear heads put together a motor and linkage to drive the unit constantly for days of wear testing.  It has been a fun project to not only design the boat but to also make improvements to the drive unit itself.

5 mile pedal in the first Slayer Propel proto
Stats from the 5 mile pedal.
The longer the testing went on the more excited we all got. The Native pro staff and endorsed guides did a great job advising us on features they wanted to see. What I found during the time I was on the water experimenting with this boat was that I wanted it not only for fishing but to just get out and enjoy the water. During my longer pedals the feeling I was getting was that of going on a bike ride, or a cruise in one of our touring kayaks. Everyone who takes it out for a test pedal falls in love with the way the speed and ease of pedaling lets you explore a huge territory and maybe get a little exercise.

Out for a sunset cruise with Betsy.

Here is a link to a bunch of photos from the Development of the Slayer Propel.
Here is the Slayer Propel Webpage.  Check it out!
See you on the water.

p.s. Here is a little video I did of the first day pedaling the production Slayer Propel.

The First Pedal of the Slayer Propel from Shaneslogic on Vimeo.

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