Saturday, June 30, 2012

The Ultimate Off-road Kayak Trailer

Last fall, with the help of some friends, I completed the third phase of my quest to build the ultimate off-road kayak trailer.

It all started while I was attending college in Klamath Falls, Oregon.  I started hunting public land at the north end of Agency Lake because I didn't have a boat. The lake is ringed by miles and miles of levees built to drain the once lush wetlands and make pastures for grazing cattle. While the levees decimated the local ecology, they did make for relativity quick and easy access by foot or bicycle for hunters without a power boat. The only trouble was crossing the deep and potentially deadly canals that paralleled the dikes. The mud along these canals was soft and deep and could potentially swallow a duck hunter whole.

I decided I wanted to access these canals for hunting purposes, but I had to figure out how to get my kayak down the miles of dike roads. My first prototype kayak trailer was built from a salvaged golf caddy cart and some PVC pipe. It worked quite well at low speeds behind my mountain bike. At high speeds the trailer tongue would start to flex and it would develop an oscillation that looked like the "tail wagging the dog." I had intended to proceed directly to an aluminum version, but the trailer was so cheap and work well enough that I didn't bother. 

Phase 1 - Golf caddy and PVC cart

Phase 1 - Golf caddy and PVC cart

Phase 1 served me very well until it failed one dark morning in my senior year of college. The coupler connecting it to the bike broke and my kayak and trailer when careening off the levee into a batch of stinging nettles. I managed to limp it along to reach my hunting spot, but the trailer needed major repairs. At that point the season was almost over and I was busy getting ready to graduate so building phase 2 was put on the back burner.

When I moved up to Juneau, I found that levee road access was still very important to my boat-less duck hunting options. A portion of the Mendenhall State Game Refuge is bordered by the Juneau Airports "EVAR" trail (Emergency Vehicle Access Road). This hardened trail is only open to pedestrians and bikes, just like the Agency Lake trails, so I set out to build phase 2. This took a couple years of sporadic designing, but finally this new trailer came into being, constructed out of 1-1/4" aluminum square tubing.

4 link suspension
Phase 2 - Frame under construction

Phase 2 - Triangulated 4 link suspension

Phase 2 - Triangulated 4 link suspension

I decided I really wanted an off road suspension so I hit my favorite off-roading forums and read up on suspension design principle. On I ran across an excel program that computed all the necessary parameters to design a triangulated 4 link suspension. This type of suspension uses 4 links that connect at different points of the trailer frame and axle to control the movement and placement of the axle. 

The design was sound, but my execution was lacking. I had to find a way to make my own links and mounting points. I found some small rod ends that allowed the articulation I wanted, but the threaded rods  were the weak link and they failed catastrophically as I was walking back to the trail head.

Phase 2 - Pre-triangulated 4 link suspension

Phase 2 - Cart in action 
 When it became clear my triangulated 4 link suspension had some issues, I started to look at a design for off-road trailers for desert expeditions and learned a fair amount about these new off-road trailers towed behind Jeeps and other 4x4 vehicles. This off-roading crowd was building trailers that use the same wheels and tires as their vehicles with the same track width, allowing them extreme maneuverability so they could go farther than ever before.

I decided phase 3 would be an independent trailing arm design using inexpensive coil over shocks found on Wal-Mart special mountain bikes.

Another year of day dreaming and design led me to modifying the suspension on my current trailer, since the frame was still in good condition. I had a friend help me weld on some tabs to the frame and the trailing arms to create pivot points and mounts for the shocks.

Phase 3 - Independent Trailing Arms with Coil-over shocks

Phase 3 - Independent Trailing Arms with Coil-over shocks

All in all the trailer works, but phase 4 will address several issues. First, the trailing arms need additional lateral support. Any side load and there is significant deflection at the pivot points and the track width of the tires makes it pretty tippy. Secondly, the trailing arms are too far forward, so the rear half of the frame is mostly unsupported and there is visible deflection from the weight of the boat. It also makes the trailer back heavy so I have to apply downward pressure on the tongue because of the imbalance.

Phase 4 will have new trailing arms, probably in the shape of an "A" with two connection points, to resist the lateral loading and they will be set further back for better frame support and balance. I will probably reduce the overall height, either by moving the shock or using smaller wheels.

Feel free to contact me if you have any questions or comments about this project.


  1. Independent Suspension..... Genius!

    1. Glad you like it and thanks for commenting!

  2. What a sweet setup. very cool. Just found your blog and can't wait and look forward to reading up on your adventures. Good luck with the new setup!

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