Rocker and Stability

Boat design is all about compromise. Ideally, the canoeist needs a dynamic boat which changes to suit the water conditions and the paddler’s skill and experience.

This is no better illustrated than on the Devizes to Westminster canoe race where the requirement is:

  1. A fast, narrow (and comfortable) boat for the first 14 miles.
  2. A lightweight boat which is easy to get in and out for all the portages to Reading.
  3. A more stable boat for the long stretches on the Thames.
  4. A rock-solid stable boat for the tideway.

There are too many design ideas which are in conflict and mutually exclusive. It’s the responsibility of the designer to decide where the compromises should be. It is up to the user (purchaser) to select the design which best suits their purposes, but no boat will be perfect.

Personally, I’m looking for a C2 which will be fast, light, comfortable, ICF compliant, stable, affordable and looks great.

So, onward with testing.

In order to improve the stability, I forced open the sides of the boat to increase the width

Sides splayed out

Sides splayed out

This inevitably caused the ends to rise slightly and increase the rocker. However, the changes I’d made to the hull kept this to a minimum.

Increased rocker

Increased rocker

Top view

Top view

What it also meant was that the amount of freeboard between the surface of the water and the top of the gunwales was only about 8 cms (3 inches in “old money”). However, it turned out that this didn’t matter because the stability was massively increased.

C2 - forth trial

C2 – forth trial

With the increase in stability came more assertive and confident paddle strokes. It was easier to keep the boat straight, although John’s left stroke is far more powerful than paddling on the right. This meant I had to work hard to avoid the bank, but the further we paddled, the better I was at anticipating this behaviour rather than reacting to it.

I was somewhat surprised with the vast improvement in performance simply by splaying out the sides, and our speed increased significantly. This can be seen on the YouTube video:

This boat has served its purpose and it will be chopped up and discarded. I am clear about the amount of rocker and the seat positions. I need to make the boat narrow to be fast, but wide enough to be stable. It would also be better to raise the height of the seats for comfort and more efficient paddling (so, more stability then!).

These criteria will be input to the CAD design and the Naval Architect who translates my ideas into data and one day, into a boat.

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