ArticlesCanoesTechnique

Building Light – Can You Know What Your Boat Will Weigh?

portaging a light wood canoe

It’s a perennial question. How much is my boat going to weigh? It’s asked by every builder and, for the most part there, is no simple answer. Materials and design choices can make as much as a 25 pound difference in a strip built canoe or kayak. A 15′ Solo Canoe from Ashes will weigh more than 45 pounds if traditional materials and techniques are used. On the other hand, by reducing strip thickness, using lighter cloth and replacing the gunnels and seat materials with lighter woods, we regularly build canoes in the 30 pound range.

portaging a cedar strip canoe on railroadThis kind of weight reduction requires taking a close look at every element; it requires a sharp pencil, patience, and specific knowledge of the woods, fabrics, and finishes in question. For those who enjoy puzzles and building spreadsheets, the process can be almost as engaging as building a boat. For others it seems like a dark art and it’s easier to default to a designer’s suggested weight.

This fall (2017) to help our customers and bring greater clarity to our in-house design and building decisions we invested in making an online weight calculator that automates the process of estimating final weights. Its results are based on  an array of simple inputs; boat model, length, wood choices, layers and type of glass, etc …

It lets its users know anticipated results within a pound or two and with a full understanding of why each boat weighs what it does and what the implications are for  making different choices. Our hope was, that it would allow ourselves and others to make decisions in an accessible and transparent way. In other words, no more guessing! Based on the users inputs, the calculator individually determines the weight of:

  • bare hull
  • gunnels
  • fittings
  • finishes and fasteners
  • final boat weight

Having this information in advance means builders are better able to make materials choices, choose construction techniques based on their final weight goals, and make meaningful comparisons when choosing which boat might meet their needs.

Canoe Weight Calculator

The only challenge a user might find will be in knowing  the surface area of a particular boat. Some plan sellers will publish this number. Some won’t. To help those without access to this number I’ve included some generic numbers as starting points. It should be noted too, that the calculator is limited to the most commonly used boat building woods and materials and as such won’t be useful to those using exotic fabrics or hardwoods.

How Accurate is the Calculator?

In ou

portaging a cedar strip wood canoe that is lightweight

r shop, using best practices to the best of our ability, we generally get with one pound of our target weights. That said, to hit the numbers an amateur builder needs to pay attention every step along the way.

  • Choose properly dried wood. Anybody who’s randomly selected planks of building materials will know how much variation there can be between one plank and another. If weight matters, don’t be lazy about wood choice.
  • Pay attention to your gunnels and fittings. It’s easy to overbuild. The calculator provides options based on the type of use you’ll be putting your canoe or kayak to.
  • Use the manufacturer’s recommended amount of epoxy for the cloth you’re using. This is an area where it’s easy to get carried away. Use enough to fill the cloth weave and no more; you’ll just be adding plastic where you don’t need it.
  • Consider your use of mechanical fasteners. The greatest stresses on a boat are at the stems and centre thwart. Do you really need screws every four inches along the gunnels?
  • Be a minimalist. Do you really need fancy decks? Complex marquetry? Inlays? Flotation tanks? Brass cleats? Sliding seats? It’s all your call; it all comes with a weight consequence. You choose.

 

The Calculator is free to use. Find it at Ashes Still Water Boats – Weight Calculator.

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Trevor Paetkau is the proprietor of Ashes Still Water Boats, a purveyor of Custom Canoes and Plans for Cedar Strip Construction.

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