Good boatbuilding wood - and how to find it

When you set out to build a wooden boat, one of the big questions you will be facing is what wood to use - and where to get it.

One of the wonderful things about wood is that each species has different properties, and even within the same species the properties can vary quite a bit depending on the place and the climate in which the tree has grown. But this also makes finding suitable lumber for your boat quite an intimidating task, especially if you've never done it before.

So my goal for this article is to give you the knowledge you need to find the wood you need for your boatbuilding project.
 

What if I can't get the specified wood?

If you are familiar with boat plans, you know that they usually include a specification on the species of wood you should use for the various parts of your boat. If these species are available where you live, you're in luck. But there's a good chance that this is not the case. Or: Perhaps the specified species are available, but not in a suitable quality, or at a reasonable price.

That's when you begin looking for your substitutes. This canoe, for example, is the Fiddlehead, designed by Harry Bryan. The plans call for northern white cedar planking and decking, pine for the mid-frame and the deck supports and white oak for the coaming, the stems, and the guards. Harry chose these species because they are great boatbuilding woods and because they are locally available on the Atlantic coast of Canada where he lives.

In Denmark, where I live, we have a good supply of pine and white oak, but northern white cedar is not very common. I might be lucky to find it in the "exotics" department of some lumberyards, but the price will be equally exotic. Plus, it has probably been kiln-dried, which is not ideal for boat wood. So for my Fiddlehead canoe, I wanted to find a substitute wood with properties that were similar to Northern White Cedar.

Northern white cedar is very lightweight, has a good strength to weight ratio, and has good rot resistance. These properties make it a good choice for planking small, lightweight boats. The traditional choice for small boat planking in Denmark is larch. It's a bit harder, a bit stiffer, and a bit heavier than cedar. Because of the higher stiffness of larch, I reduced the planking thickness from 8mm to 6,5mm, which partly, but not quite, makes up for the extra density of the larch.

What's the best boatbuilding wood for you?

But what are the best boatbuilding woods available in your area? Well, it can vary so much depending on where you are in the world. What I would recommend you to do is to start out by visiting a local boatbuilder or maritime museum and ask them what wood they would use for your project. If you bring along your plans, the folks at your local boat shop can probably point you to a few locally available species of wood that would work for your project. Perhaps they even have some suitable lumber in stock that they are willing to sell. Or: They can point you to the sawmills that they would recommend you buy from.

Technical properties of wood

When you research your substitution candidates, you should compare the technical properties of your substitute wood with the technical properties of the wood specified in the plans. 

You will want the key properties to be similar, and if they are different you will want to make sure that it is okay for the intended use of your boat. For example: If your boat will live in a freshwater lake all season, you'll want to use a rot-resistant species of wood. Or: If your boat will be dragged across rocky beaches every day, you will want wood with good hardness and abrasion resistance. On the other hand, if your boat will be stored under a roof and it will only see light, occasional use, you can probably get by using wood that is softer and less rot resistant.

But it is also important to know the technical properties of your wood because you may need to make modifications in the dimensioning of your boat parts. The dimensions of boat parts are called "scantlings" in boatbuilding terminology.  If, for example, your substitute planking wood is heavier and stiffer than the wood specified, you may want to reduce the plank thickness to keep the weight of the boat down. That's what I did with my Fiddlehead Canoe. Or if the wood you have available has greater shrinkage than the specified wood, you may want to consider using narrower planks for the boat to avoid problems with plank seams opening up or the wood splitting.

In my experience, small boat designers are very passionate people who are usually very helpful about these topics. If you can find the email address or phone number of your designer, try and get in touch to get some advice on which changes should be made using the wood species you have available. If you are building a historic boat type, the designer most likely won't be available for email consultation. In that case, a solution might be to talk to your local, friendly boatbuilder for a bit of advice.

Six technical properties of wood you should know about

When you are researching which wood species to use for your boat, it's a good idea to dive a bit into the technical properties of the wood you have available, comparing it to the wood specified in your plans.

Here's a brief overview of six different technical properties of wood that it's good to be familiar with as a boatbuilder:

1: Weight

The first one is weight, also known as gravity. This is usually measured in weight per cubic foot or cubic meter. Weight is of course important because - in general - you will want your boat to be as light as possible.

2: Stiffness

The second property of wood that you should know about is stiffness or modulus of elasticity. This is measured by how much the wood bends when pressure is applied to it. In general, stiffness is good, because with stiff wood you can reduce the dimensions without making your boat too soft or flexible.

3: Breaking strength

The third property that you should know about is breaking strength or modulus of rupture. This is measured by how much force must be applied to the wood before it breaks. Under normal conditions, your boat parts should never be anywhere near their breaking strength. But high breaking strength can be an advantage in the case of an impact.

4: Hardness

The fourth property that you should know about is hardness. Hardness is measured on the so-called Janka scale. The Janka number indicates how much pressure is needed to press a steel ball halfway into the surface of the wood. In other words, how much pressure it takes to make a dent in the wood. Hardness is good if your boat takes a lot of abuse.

The stiffness, the breaking strength, and the hardness of the wood is usually closely related to the weight of the wood. A light species of wood is usually less stiff, has lower breaking strength and lower hardness than a heavy species. But the relationship between these properties may vary a lot.

5: Shrinkage

The fifth property of wood that you should know about is shrinkage. Wood that shrinks and swells a lot will tend to have plank seams opening up more when the boat dries out after spending time in the water.  Shrinkage is measured in percent from when the wood is green to when it is oven dry. There are two shrinkage figures: Tangential shrinkage, which is the shrinkage in circumference of the tree, and radial shrinkage, which is the shrinkage from the pith to the bark of the tree. Longitudinal shrinkage, that is shrinkage along the wood fibers, is so little, that you won't need to take it into account.

6: Decay resistance

The sixth property of wood you should know about is decay resistance. Decay resistance indicates how well the wood resists rot when it is in a humid environment. This is usually graded at a scale from Very Durable to Perishable. Boats - obviously - often spend time in humid environments, so generally, you will want the wood for your boat to be as durable as possible. However, if you can keep the wood dry, either by storing your boat on land or by coating your wood with epoxy, varnish, or paint, rot is not a problem. Wood that is dry cannot rot.

Steam bending properties

One last property of wood, that I would like to mention very briefly, is how well it steam bends. Some species of wood can be bent to astonishing degrees if it's heated up. So if your boat design includes steam-bent planks or steam bent frames, you should choose a species of wood that lends itself well to steam bending, such as oak or ash.

There are great books and online resources available where you can look up the various technical properties of the species of wood that you are interested in. I have put a few references in the description of this video.

Real-life properties of wood

It's important to keep in mind that the technical properties of each species of wood is based on an average. The actual properties of a piece of wood can vary a lot, depending on where the tree has grown but also how it is cut and what defects there might be in the wood.

Planks with a lot of knots and cracks are, of course, not as strong as straight, clear planks. Just like planks with the grain running diagonally are not as strong as planks with perfectly straight grain.

What you should look for at the sawmill

These are the factors you should look for when you are at the sawmill to get the best possible wood for your boat:

1: Species

First of all, make sure that the species is suitable for your project, considering the technical properties we have just discussed.

2: Dryness

Next, you will want to know if your wood is air-dried or kiln-dried. For furniture, kiln-dried wood is usually preferred,  because it is so dry that it will shrink or expand very little in an indoor environment. But for boats, air-dried wood is generally best. This is mainly because you want the moisture content of your wood to be as close to what it will be when the boat is in use so that shrinkage and swelling is kept at a minimum. Kiln-dried wood is too dry for a boat, so it will swell up when the boat's in use. Also, if you will need to steam bend parts for your boat, green or air-dried wood works best.

If it is air-dried, you will want to know how long it has dried. A 1-inch board can take up to 6 months to reach equilibrium with the ambient air. For small boats, the planking is often quite thin, perhaps around 6-8 mm. This thin planking has a larger surface, so it will dry a lot faster - perhaps in a month or less. The sawmill probably has a moisture meter you can use to check the moisture content of your wood. If the moisture content is around 20%, you are in good shape.  If it is higher, it's okay, too, but you will probably want to dry it a bit longer before you put it into your boat. A simple way of checking when your wood is at equilibrium with the environment is by weighing a sample of it. As soon as your wood stops losing weight, it is fully air-dried.

3: Dimensions

Then, look at the dimensions of the wood. Are the planks long and wide enough to provide the parts you will need for your boat? If you can get planks the full length of your boat, it's great, But if they are shorter, it's OK, too, because you can scarph your full-length plank together out of two pieces of wood. For boats, live-edge wood is generally preferred, because an odd-shaped plank is often just what you need to get your boat part out. Remember that you should always cut away the pith and the sapwood when you make your boat parts.

4: Knots and cracks

Then, look for knots and cracks in the wood. A few healthy knots can be okay if the plank otherwise looks good. If the plank has one or two loose knots, it's okay too, because these knots can be plugged or they can be filled with thickened epoxy. Quite often, planks have some drying cracks towards the ends. You don't want these cracks in your finished boat parts, so make sure that they can be cut away.

5: Crook, cup, twist, bow

Then you should check if your board is crooked, cupped, twisted or bowed. A crook is a board that is bent along its length. This is usually okay, as a lot of boat parts have a curve, too. A cupped board can be okay, too, but you will need a bit of extra thickness when you plane the board to get it flat and smooth on both sides. If your board is twisted or bowed, you should discard it. A twisted or a bowed board will be harder to work with, and it may introduce asymmetry into the boat.

6: Orientation of annual rings

The orientation of the annual rings can make a difference in the dimensional stability of the plank. A flat sawn plank is generally a bit less stable than a quarter sawn plank. This is due to the fact that most trees shrink and swell more tangentially than they do radially. So if you can get quarter sawn wood, it's great, but for most boat parts, flat sawn boards will very well, too.

7: Crooks

Some sawmills, especially the ones that specialize in boat lumber, can supply sharply curved crooks for stems, frames, knees, breasthook etc. Grown crooks are wonderful because they will give you the best possible strength for your part. If you go shopping for crooks it is great if you can bring templates to find the best possible crook for your boat parts. You can make your templates by referring to the plans and the table of offsets, or you can make them directly on the boat as you are building it.

Get extra wood

A few final words on going to the sawmill: First of all, get some extra wood. You will want enough wood so that if you make a mistake, or if you find an unexpected defect in the wood, you can take a new plank and start over again. If you should end up with some wood to spare after your project, you will surely find something else to use it for - perhaps even your next boat?
 

Be good to the sawmill staff

Secondly, be good to the sawmill staff. As a builder of a small boat, you are most likely not the ideal customer. You are picky and you don't buy large quantities of wood. So if you want their blessing in your hours of picking through the piles,  bringing your friendliest manners (and perhaps cake) is not a bad idea.

Buying sight unseen

It is always best if you see the wood with your own eyes before buying it. But sometimes, the wood you need is not available locally, so you will need to buy it sight unseen. In this case, I would recommend that you use a specialized boat lumber supplier. You will probably pay a bit more for your wood, but if you give a good specification, they should be able to provide you with quality wood.

I hope this video has given you the information you need to begin your search for lumber for your boatbuilding project. Being a natural material, there are a lot of variables in wood. But if you go about the process methodically by first researching your species and then examining the wood at the sawmill, the hunt is fun, and you should be able to find good quality wood.

- Mikkel Pagh