The Cart

Kayak Cart

Kayak Cart

The Hobie Pro Angler 14 is over 100 lbs empty. That’s heavy by any standard. It makes moving it around and throwing it on top of a Nissan Xterra something of a challenge. The first accessory I made therefore, was a nearly indestructable cart.

Good engineering starts with a problem statement. Then onto requirements, analysis/research, design, implementation, test, and possibly rework. This project was a classic example. The problem – How do I get my boat from the car to the launch and back? The basic requirements:

  • Need to move the boat by myself.
  • Must be able to carry 100lb boat plus 50lb of gear, up to say 300lbs max.
  • I want to be able to bring the device with me on the boat; especially if it is a long way between boat and launch.
  • It would be nice to use the same method as the Hobie carrier to stow on the boat – by utilizing the scupper holes for the uprights

Version one of my cart was made from 1/2″ electrical conduit. I formed the conduit into a cart shape, put an axle and some wheels on it and called it done. Then I put the boat on it. The failure was astounding. I really thought conduit was stronger than that. After all of the articles I read about carts made out of PVC, I thought for sure I was onto something. After all, the extremely expensive Hobie cart is made out of aluminum, and can’t be much stronger. Let’s call that one a straw man or prototype and forget that I even mentioned it.
So onto version two. The good folks at Home Depot now know better than to ask me if I need help when they see me wandering aimlessly, muttering to myself “will this work…?” as I scope out the various materials to be used for other than their intended purpose. They know I am pondering material strengths, dimensions and ease of assembly. OK, well, so they don’t – I usually just smile and tell them to go away. Invariably I end up in the plumbing section, looking for pipe that fits into the scupper holes of the boat. It turns out 3/4″ galvanized pipe fits perfectly with a little slop. A lighter boat could probably use 1/2″ and save a few dollars (just be careful of the dimensions – they will be a little different than what I call out here). This pipe I found back in the section with sprinkler parts and brass fittings and such. There are actually two kinds of pipe – the galvanized iron pipe which is gray, and the black pipe. Both are just as strong, but the black pipe is a little more expensive. I don’t know the technical differences beyond that; what I do know is this stuff is pretty darn strong.

The final version uses the following bill of materials:

  • 6 of 3/4″ x 10″ nipple
  • 2 of 3/4″ x 4″ nipple
  • 2 of 3/4″ x 4 1/2″ nipple (note, these aren’t as critical for sizes; 4″ – 6″ can be used depending on how much threaded axle rod you want exposed
  • 5 of 3/4″ Tee
  • 2 of 3/4″ x 1/2″ reducer
  • 2 of 1/2″ x 1/4″ reducer
  • 1 of 1/2″ x 3′ threaded rod
  • 1 of 1/2″ x 22″ steel electrical conduit (optional, but recommended)
  • 2 of 7″ wheels
  • 6 of 1/2″ hex nuts
  • 4 of 1/2″ flat washers
  • 2 of 1/2″ lock washers
  • 2 of 1/2″ threaded rod coupler
  • 2′ pipe insulation
  • (optional) 2 of 1/2″ wooden dowel, about 1″ long
  • (optional)Auto/marine silicone sealant

Tools needed:

  • 10″ – 12″ pipe wrench or adjustable wrench
  • tape measure or ruler

Cart parts
Now, as far as piping terminology, this becomes kind of important when you are mixing and matching threaded components. First off, the short lengths of threaded pipes are called “nipples”. These come in lengths from “close fit” which is just one 2″ pipe with nothing but threads, up to several foot long pieces in 1/2″ intervals with threads only at the very ends. That makes a pretty good variety to pick from in order to get the dimensions correct. Pipe threads are typically “tapered” so that they screw in so far and become very tight in order to seal them air/fluid tight. While this project doesn’t aim for preventing leakage, it is important to realize this when you are measuring individual pieces, because they don’t screw in all the way; if the threaded section is 1″, usually only about half that screws into the mating end before it becomes impossible to turn. Plan appropriately!

In order to join the various sections together by combining two or three pieces of pipe, you use “Tee”s, “Y”s or “Wye”s and “couplers”. Don’t forget to measure and account for these; couplers are usually shorter than tees. To go from one size pipe to another, e.g. to join 3/4″ pipe with 1/2″ pipe, use a “reducer”.

Another one of those funny details is pipe sizing. When you say “3/4 inch pipe”, you generally mean the inside diameter of the pipe. The pipe walls have thickness, so the pipe diameter out to the edges might be a full one inch. Think about this when you are buying pipe for the purpose of inserting something into it; for example, a 1/4″ pipe may actually be 1/2″ in overall diameter due to the wall thickness. If you have a 1/2″ rod, you can run it through fittings sized for 1/4″ pipe because the threaded ends of the fittings are 1/2″ in diameter. Clear as mud? I know, it still confuses me. I usually try to fit things together at the store whenever possible just to make sure it all works before I pay for it. Otherwise, you can waste hours driving around to exchange parts.

In order to make a cart, you need an axle, two uprights that will go up through the scupper holes, and two horizontal arms that will support the boat above the wheels. The Hobie Pro Angler 14 has scupper holes in the baggage area behind the seat that are on approximately 11″ centers. In the initial revision of my design, I decided to make the axle with a coupler in the center, and two tees to join the uprights. My rationale was that this would allow for some extra adjustment by tightening or loosening the various parts in the assembly in order to line up the uprights with the scuppers. This turned out to be a really good idea, however I will throw out a spoiler here and say you want to use a Tee, not a coupler in the center of the axle. The reasons will become evident soon enough!

Since the measurements are all a bit nebulous due to the variations in how tightly things are screwed together and how many items are coupled together, I bought a bunch of different sized nipples (and ended up returning some that I didn’t need) to experiment with. The following steps are what I came up with to fit this boat.

First, make two axle halves by starting with a Tee, and screwing in a 10″ nipple, a 4″ and a 4 1/2″ nipple as shown in the picture. Add the two reducers to the end to reduce the axle opening. The 4″ nipples will screw into the center Tee. The outer nipples can be sized differently depending on how much threaded rod you want exposed. This will depend somewhat on the type of wheel you use. A lawnmower type wheel is fairly skinny, while a balloon type tire is wider. I used 4 1/2″ because I didn’t know what size to use at the time, but that seemed OK in case I wanted to upgrade to a fatter tire someday.

Axle ends
I ended up buying a couple of plastic lawnmower style wheels from Harbor Freight that claim to support 150lbs. The hub takes a 1/2″ axle, so I bought a 3′ length of 1/2″ threaded rod. To add some support for the threaded rod, it turns out that 1/2″ conduit fits perfectly through the 3/4″ iron pipe, and 1/2″ threaded rod fits perfectly inside 1/2″ conduit, so I cut a length of conduit to provide support for the rod. Attach the center Tee (point the open end downward) and insert the conduit.

Axle 2
Screw on the other axle half to complete the axle assembly.

Axle 3
By the way, your big 12″ (wrench, that is) will help torque down the fittings.

My big 12 inch

The uprights consist of four 10″ nipples, two on each side. Another Tee is used to join the two nipples, plus the third nipple used as the boat support. The third nipple can be as long as necessary, but making it 8″ – 10″ is ideal. You already attached the bottom nipple to the axle assembly, so add a Tee and another nipple to make the full length upright. Note if your supports are longer than about 8″, you won’t be able to tighten down the uprights as the spacing between them is shorter than that!

Support arms
By the way, since the two “top” ends of the cart will actually be in the water when the cart is stowed on the boat, I elected to plug the pipe ends of the lower upright nipples to prevent water from getting all the way to the axle assembly. Not that it won’t happen anyway, but it seemed like a worthwhile touch. I cut two pieces of 1/2″ wooden dowel and sealed them into the ends with auto/marine silicone RTV sealant. This step is of course, optional.

Sealed ends
In the same aisle that I got the threaded rod was a plastic box of hardware containing some large flat washers, lock washers and nuts specifically for the threaded rod size. How convenient is that! Note that the 3′ threaded rod is just a little long; it will actually overhang the edge of the boat a slight amount. I decided not to cut mine in the event I want to put fatter wheels on someday. If you haul your boat across sandy beaches, some big fatty balloon tires may be a better bet for you. Instead, I bought a couple of threaded rod couplers and screwed them onto the ends just to eliminate the “ragged” thread ends.

Insert the threaded rod through the axle assembly so that an equal amount of thread is hanging out of each end. Put a nut on each end to keep the axle in place. Then, add a flat washer, wheel, another flat washer, and a nut. Tighten the nut down just enough so that the wheel just spins freely without wobbling. Add a lock washer and another nut and tighten it down. This will keep everything secure. Optionally, add the threaded rod couplers to the ends, or you can use a hacksaw to cut the rest of the threaded rod off.

Assembled frame

As a finishing detail, I added some pipe insulation to the boat supports just to prevent the pipe from scratching up the boat. Unfortunately you can’t cap the ends as the caps will not fit through the scupper holes. An alternative would be some large diameter heat shrink tubing. I would not recomment tape, as the ends of these will eventually get wet, and the tape will not likely hold very long.

Padded arms
If you are unable to tighten everything down to the point where it doesn’t “flop around”, you could put some JB Weld on the threads just before final assembly. Just PLEASE be sure to dry fit everything first to make sure everything is sized correctly, then check it again before the glue dries! Otherwise, you might not be able to separate the parts afterwards to adjust them.

Here is a picture of the cart stowed on the boat. Now, remember the Tee in the center of the axle? Sure looks like I can screw something into that, doesn’t it? Maybe a light on a pole? An umbrella holder? A fishing rod holder? A camera mount? Yes. Yes we can!

Padded arms
Pro’s of this implementation:

  • Strong as hell.
  • Easy to get parts
  • Can assemble in an hour or so
  • Designed to take it with you on the boat
  • “Accessory port”! Bonus for when your cart is stowed on the boat – you can use it as a mount for other stuff.

Con’s:

  • It is HEAVY. You can have strong. Or you can have light. Sometimes you can have both, but not today.
  • Plastic lawnmower wheels – I bet these will break soon enough. Wheels with metal hubs might be better.
  • It plugs into the rear scupper holes. The boat is 14′ long. You now have a long lever. Pick up the front of the boat. It is really, really heavy. First upgrade may be a “nose” wheel! Advice – put the ice chest with the beer in the back of the boat until you get to the water!
  • You have to roll the boat onto its side in order to plug the cart into the scupper holes. I’m contemplating some kind of “kick stand” to allow me to pick the back of the boat up and lower it onto the upright cart.

Update – 06/17/2015

My favorite store, Harbor Freight, had a sale on wheels recently.  So I decided to upgrade the cart.  I think these wheels will do slightly better in the sand, and the hubs are metal.

wm_DSC01610

The new look – including the now rusty connectors…

wm_DSC01609