Stealth 2000 Wheel Solution
Overview
The Beavertail 2000 is a great boat for duck hunting and fishing on quiet water. The hull is made from High Density PolyEthylene (HDPE) and weighs nearly 150lbs. HDPE is a relatively soft material, and will grind away rapidly when dragging the boat on concrete, asphalt and rocky paths. Also, the 150lb weight is borderline for the average person to drag any distance, i.e. you aren't going to drag this boat, loaded with your duck gear, 1/2 mile to your favorite mudhole. This is a boat that needs a wheel solution.
Disclaimer
I hate having to put this in here, but the world today requires it. The following is a discussion of solving the problem of transporting a 150lb or greater weight. The weight is enough to cause injury if you have a boo-boo. The weight is also enough that you can damage the hull of the boat if the load is not distributed correctly. So be careful. And don't whine at me if you drop the boat on your foot, or trim your finger with a saw, put out your eye because you didn't wear eye protection, or get run over by the boat trying to lead it down a hill. I'm not selling anything, nor do I make any claim to credentials that validate my approaches - I may be wrong. So you are responsible to use your own head and think this through.
Performance Criteria
Must haves:
Must support the boat at its keels
Must handle 300lbs (150lb boat plus full load of duck gear)
Must handle dirt trails, moderate side-hills, and slopes.
Nice to haves:
Nice to be boat-stowable
Nice to be under $100
Nice to be flat-free and sand-capable
Nice to have brakes
Nice to have a kickstand
The Problem
Side view sitting on the pickup
Cockpit view
Loaded for duck hunting
The 2000 is 12' long, 44" wide and ~14" high(not including seat). The manufacturer claims the weight is 120lbs, but I believe it is closer to 150lbs.
The hull has many molded-in features which are not explained, and remain a bit of a mystery. Most all of the super-structure is foam-reinforced and quite rigid, with only the floor of the hull remaining flexible.
The bottom of the hull is catamaran-style, with two rigid keels supporting a flexible bottom. The keels are designed to be weight-supporting according to the manufacturer.
Approaches Considered
I looked at the following:
Commercial kayak cart - +Available, +stowable, +lightweight, +compact, -expensive, -doesn't support at the keels : : Least amount of fabrication work
Yard debris Cart/Wagon - +Available, +reasonable, +high lateral stability, -high center of gravity, -not stowable, -heavy/bulky : Moderate amount of fabrication work
Aircraft-style retractable wheels - +stowable, +lightweight, +compact, -low lateral stability : Greatest amount of fabrication work
Custom built Cart - +stowable, +lightweight, +high lateral stability, -bulky : A fair amount of fabrication work
The biggest problem with commercially available kayak carts is that they are designed for (drum roll) kayaks. And your typical kayak weighs maybe 80lbs loaded. Also, they are not for the faint of heart budget-wise, pushing $300 for the nicer ones. I haven't found any that would work for the Stealth 2000 without modification to the supports to lift at the keels.
The yard cart/wagon is basically an over-sized children's wagon with fat tires. I've seen the Chinese versions on Craigslist for $60. These will handle the weight, but they need some tweaking to support at the keels and the tongue lengthened to enable pulling. Because they are steerable, you have to have control of the tongue while pulling/pushing the boat. The carts I've seen are much narrower than the Stealth 2000 and a bit high, leading me to wonder about stability with such a high CG.
The aircraft wheel idea is one of those ideas that could look pretty slick when finished. But it takes the most work to fabricate and would likely offer mediocre performance unless a fellow could solve the lateral stability problem.
A custom built cart has potential with the right approach. If you stick to common materials and avoid fancy construction techniques (like tig welded aluminum), a fellow could knock out a cheap, adequate cart that meets the criteria.
OK, So I'm Building a Custom Cart
This is about the cheapest cart design I could come up with. It is cheap, stowable, supports at the keels, handles 300lbs and works on hard-dirt trails with the cheap Harbor Freight (redundant) wheels.
Hopefully you get the idea from the high-quality drawing I did on my Note4. The "V" is maintained by a strap between the two supports. This makes it easy to "fold and stow" and there are no parts to lose.
To save on words, here are a bunch of pictures.
1/2" 4 ply pressure-treated plywood.
1.75" x 10" Solid wheels, 150lbs rating each. $7.50 at Harbor Freight. #1 garage door hinges ~$5ea, 7/16" x 6" bolts for axles.
The hinge holds the axle. Hinge ID is 7/16". Wheel ID is 1/2". So I'll need to shim the wheel with roof flashing around the axle to reduce wobble.
Cut and drill both pieces at the same time. Use wood screws to hold them together.
Here are a couple of views of the almost assembled cart (missing the strap solution):
And a little more detail on the axle - hinge mounting
Observations On Construction
I'll make a list of what I discovered that ought to help the next guy:
Don't cut two sheet bolted together, instead do all marking and cutting on a single piece. Why? Mainly because trying to handle the two pieces while drilling and mounting the hinges is difficult. So do all marking and drilling for the hinges on the single sheet, then as a final step cut the sheet into the two halves. All jig saw work can be done easier working on one sheet.
I chose to make the length of each side 18". So This project requires less than a half sheet of plywood. It may still be too tall at 18".
I chose 1/2" 4 ply pressure treated because it was available and I was concerned about weight. But had I gone to 3/4" 5 ply I would've felt comfortable skipping the backing plates sandwiching the plywood at the hinge. Basically the thicker, stronger plywood eliminates the hassle of drilling/bolting the hinge and backing plates.
I can tell right now that the 10" diameter by 1.75" wide Harbor Freight wheel is going to sink in the soft and may be unusable. But I can double/tripple them up by using a longer bolt (7/16" x 10). I would love Wheelz balloon tires, but they're $70ea. So I'm looking at $20 to increase the width 1.75" on both sides (2 wheels and two longer bolts).
I haven't thought through how to strap the boat to the cart. Nor have I thought through how to strap the cart to the bow of the boat. Or how to make it float. Or a kickstand solution. Etc., etc., etc.
Testing the 1st Generation Cart
This is where my favorite Yogi Berra quote applies - "In theory, there's no difference between theory and practice. In practice there is".
First, some details:
I used a bungee cord pull backward across the axle to hold the cart open.
My "strap" is some 600lb test Spectra line. The stuff doesn't stretch much.
I added some conduit clamps to hook tie downs to. To keep the cart from slippling, one of the tie down straps goes into the grooves by the rear seat.
I don't need a kick stand.
The completed cart
So I drug this around and it worked fine. Next I thought I would add a load and test it.
My 240lb load
So I drug this load around a bit and the wheels pretty much collapsed.
So looking at the garage door hinges that I used as axle mounts showed me that this design wasn't going to cut it for that kind of load.
This axle mount is bent mostly because of a fabrication boo-boo
On the other side, which was fabbed correctly, the axle held up better
Testing Summary
Sigh, I'm not a mechanical engineer. But some things worked, so it's not all bad. And I did overload it pretty good (240lbs of labs for a total weight of nearly 400lbs), but the 3 labs looked cute.
Here's what worked:
Didn't need a kickstand since the bungee held it open. Just drag the boat up on the cart, wiggle a little to position it and strap it down.
The 1/2" plywood was plenty strong.
The design stowed on the front of the boat and it was lightweight enough to not be noticeable.
The Harbor Freight wheels are plenty strong.
Strapping down the cart so that one strap goes through the grooves in front of the rear seat prevented the cart from sliding on the hull. Which is good because that HDPE hulll is slippery.
The lateral stability is excellent.
Here what didn't:
The strap solution allowed more give that I would like. Also I'm a little concerned that the Spectra line would slowly cut through the plywood.
The axle mount made from a single #1 garage door hinge cannot handle the torque.
I never figured out a brake solution.
2nd Generation Design Changes
So I think I can make a single change that will solve two issues at once:
A single axle mount cannot handle the torque
A single 10"x1.75" wheel sinks into soft stuff pretty deep. I'm just trying to make this work on a gravel path - not across the beach.
And there are a couple observations that I think I can improve:
Higher sidewalls will make it easier to load the boat onto the cart - hopefully it will self-center.
Extra strapping and strapping support - I want to reduce the stretch and movement.
I would like something a little less redneck than a bungee for the hold-open feature.
An 18" height feels about right for me - so that's my loaded target height.
The following is another high quality drawing done on my Note 4.
Basically the change involves doubling up the #1 garage door hinges on each side, adding a second wheel and using a really long 7/16" bolt for the new axle. The strengthening comes from the second hinge and the two wheels on a common axle.
Here's an example of adding a second pair of wheels to the original design
Testing Dual-Wheels on the Original Design
I put an honest 250lb load in the boat and drug it around. The wheels held fine but the plywood cracked.
The plywood cracked because of the flexing against the "strap" - makes sense.
So I retrofitted the original design with some reinforcement, and more "straps".
And then I tested it with a more reasonable 130lb load and it worked perfect.
Summary (what have I learned from this exercise)
Overloading and/or testing to failure showed me the weakness in the design. Better to find it in my driveway.
Those Harbor Freight wheels are the heaviest parts to this design. The weight is 20lbs now - much more than I had hoped. But they work when pulling the 130lb loaded boat across soft gravel.
1/2" Plywood is marginal. I think 5/8" should be the minimum and 3/4" optimum. And I don't think Pressure Treated matters - not sure why I ever thought it did. I would camo paint this anyways.
The garage door hinges restrict you to a 7/16" axle, whereas the common hub diameter is 1/2". I went with a 7/16" x 8" bolt and captive nut. In hindsight I think I would've been better off with 7/16" rod drilled for clevis pin clips. Flexing on the axle increases rolling resistance when loaded. I will shim this axle arrangement later using roof flashing.
Don't need a kickstand when I have a hold-open solution (bungee over the axle).
The only way to secure this to the slippery hull is to strap to the rear super-structure groove. Turns out my recent keel reinforcements helped a lot.
This won't float as is. I've got to figure out if adding foam to the edges is enough to float it and aids in reducing the sliding against the hull.
A 14" - 18" loaded height is about right for me when dragging it around by the front handle. I'm 3' 37" tall.
The position of just forward of the rear seat works for me. I know I could stack my decoys in the back of the boat, and there's really nothing stopping me from moving the cart towards the center of the boat to manage tongue weight.
I know enough now to build another cart much better. But I think I've gone about as far as practical with this general design.
I am using the dual-wheels-on-the-original-design cart right now (fishing season). And it works fine, although I don't have much load (anchor, poles, seat, life jackets, worms etc.) and I stick to hard paths, moderate hills(definitely need a brake solution). I'm not sure I'd want to drag this 1/2 mile though - the rolling resistance is high with those little 10" wheels.