How strong does the post have to be?

No commonly available data can tell exactly how many pounds of drag a ski pole must pull. So, it becomes another one one of those challenges in building a boat that requires some thoughtful estimation. For a skier, the drag weight has to be in the range they can actually hang on to, which I will guess to top out at something a bit above their body weight.

Pulling tubes, however, is a different story, which is why most of the ski post retailers say not to pull a tube. My grandkids have never understood that logic, and have been known to jump five riders on two tubes. If they lean back, it can almost prevent the boat from coming up on plane.

A typical ski rope is made with a 1600 pound max of tensile strength, and in combination with a 2-3/4″ Mastercraft aluminum pole, is not likely be the weakest link. So, the mounting frame work, which will be centered between the seat back and the front of the engine well must be “super” strong.

Creating Front to back stiffness

I started by adding inner and outer support plates to the triangle frames which had been dowelled to the bottom boat longitudinal beams.

Making the top plate

The third piece of the vertical leg was added on the inside of the front sandwich. Then three pieces of Baltic Birch plywood were laminated and epoxied into place at the top of the legs.

The ski post is 2-3/4″ wide, and don’t have a drill bit that exact size, so I had to cut it in stages. First, I used a Forstner bit and followed with a bearing guided router bit to enlarge it. Eventually, experimenting created the right sized hole.

After cutting the ledge a bit deeper, I used a flush-cut bearing bit to finish the hole through.

Last, I added a base support to hold the bottom of the pole. When the back seat top piece is epoxied into those front notches, it will add some side to side stiffness, and I am betting on the framework to pull two tubes strong with out complaint.

This is just a single example of many things in a boat building process that need to be researched, and thought fully worked through. When in doubt, overkill engineering tends to help me relax as I go on to the next chapter. But, I am pretty confident that when the first skier hangs on to the rope, it won’t let us down.