Bending Wood for a Wood-Canvas Canoe

by Mike Elliott, Kettle River Canoes

One aspect of canoe restoration that seems to confound many people is the process of bending wood.  It is puzzling, and sometimes terrifying, until you know what is happening in the wood itself.

Wood fibres are made up of countless cells that have a tough exterior wall made of cellulose which cannot be bent or stretched.  Therefore, when a piece of wood bends, it is the space between the cells that is either compressed or lengthened.  A compound called lignin holds the wood fibres together.  When it becomes hot (close to the boiling point of water – about 200°F or about 93°C), it is liquefied thus allowing the cells in the wood fibres to move.  The cells on the inside of a curve are forced closer together while the cells along the outside of the curve are pulled further apart.  When the wood cools, the lignin solidifies again to hold the new shape.

To bring the internal temperature of the wood to 93°C, two things are required: Water and heat.  Heat is used to heat water molecules in the wood.  They heat the lignin which then liquefies and allows the wood to bend.

Normally, there is not enough water in the wood to heat the lignin effectively.  So, the first step in the wood-bending process is to raise the moisture content of the wood.  This is achieved by soaking the wood long enough to saturate the wood.  The time required depends on the wood species and the thickness of the piece.  I don’t bother measuring the moisture content.  Instead, I just go on experience.  For example, a piece of Red Cedar rib stock 3/8” thick requires about 2 to 3 days of soaking time while a piece of White Ash stem stock 7/8” thick requires about 6 to 7 days.  A piece of Red Cedar planking stock 5/32” thick requires less than one hour of soaking time.

Once the wood has been soaked, the wood is heated with steam or near-boiling water.  The amount of heat required depends on the thickness of the wood.  The Red Cedar rib stock is steamed for about 45 minutes while the White Ash stem stock is steamed for about 65 minutes.  Meanwhile, the Red Cedar planking stock requires about15 minutes of steam.  Too little heat and the wood will break, too much and the fibres are cooked and start to break down.  The over-cooked wood then crumples on the inside curve when bent.

A key element in this process is the steam generation itself.  It takes a lot of steam to create the heat required to liquefy the lignin.  I use a 2 gallon (8 litre) pot over a propane stove. 

My steam box (inside dimensions – 12” high by 12” wide by 7’ long) sits directly above it (balanced horizontally) with a firm seal made of plywood rings. 

Each piece of wood in the box must have lots of air around it to allow the steam to heat each piece evenly.  A series dowels creates a number of shelves in the box.

In the “old days” many of the canoe factories were heated with large boiler systems.  These boilers were also set up to deliver steam into large steam chambers for wood bending.  In many cases, the steam could be held under about 5 psi pressure in these chambers.  These “pressure cookers” could reduce the amount of time required to soak as well as heat the wood quite considerably – about 6 hours soaking instead of 48 and about 15 minutes steaming instead of 45.

With the heated wood pliable and ready to bend, it is removed from the steam box and bent into shape immediately.  The “working time” is about one minute.  If the bending can be achieved in the first 30 seconds, that is ideal.

When I am bending a thicker piece of wood (more than ½ inch thick), I use a thin strip of hardwood – usually ash – as a backing strip for the work.  It helps keep the integrity of the piece while it is bending.  Make sure your wood is as close to perfectly straight grain as possible.  If the grain slants, the outer edge of the wood grain will “run out” and it is more likely that the wood will split or break when bent.

Once the wood is bent into the desired shape, it is important to keep it in the form for at least 3 days.  This allows the wood to dry and thereby retain its new shape.  When I am bending stems, I let the stock dry for at least a week to reduce the amount of “spring-back” in the piece.

Sometimes, you must construct and use custom forms for the specific bend required.  One example are the gunwales of the Chestnut or Peterborough Pleasure canoes.  A quick look at the sheer line reveals a sharp curve about 18” from the stem-end at each end of the canoe.  This bend is too sharp to be done when the new wood is dry.  It must be bent prior to installation.  To do this, you need custom forms for the job.  I’m sure there are as many types of steam-bending forms as there are canoe builders.  Here is the system I use.

I take the shape of the form directly from the original outwale and transfer it on to a piece of ¾” plywood that is 8”x24”.  For four bending forms, I use eight pieces of 8”x24” plywood.  Although the outwale is ¾” wide, the form is 1½” wide.  The extra width makes it easier to work quickly when bending the hot wood.  The curve in the form must be greater than the final curve desired.  Compensate for a certain amount of “spring-back” in the new wood once it has been bent and dried.  By adding about 2” more curve over the 18” of outwale than in the final curve required.  Cut the first piece of plywood and use it as a template for the other seven pieces.

Cut strips of ¾” plywood 2½” wide.  These will be the braces for the holding points along the length of the form.  For the outwale forms, I use three holding points.  In this series of photos, I numbered the stations starting with the first is at the end of the form that is 8” wide.  The third is at the end of the curve in the form while the second is placed 18” from the third holding point.  The second point is where most of the curve in the outwale occurs.

Each holding point will consist of a dowel and wedge system held in the braces.  A ¾” hardwood dowel is placed in a 7/8” hole in each set of braces.  The dowel is located so that the outwale (1-1/8” high) can fit between the top of the form and the dowel.  There must also be enough room to allow a hardwood wedge to fit between the outwale and the dowel.  Each brace piece extends at least 3¼” beyond the top edge of the form.  The centre point for a 7/8” hole is placed about 1-7/8” above the top of the form.  Attach each of the braces on one side of the bending form at their intended locations using 2” deck screws.

Now, flip the form over and place the braces in their intended positions.  Insert the dowel into the holes and make sure that the dowel fits properly.  It should fit easily into the holes on each side of the form and be located with enough space to accommodate the outwale and the wedge.

Cut the new outwales as exact copies of the originals.  You will need four pieces to create two outwales.  Determine which pieces will fit together to form each outwale and then mark the ends to identify them for bending.  Soak all four ends for about 72 hours.  I use a piece of 4” ABS pipe 7’ long as my soaking tube.

When ready to bend, remove one of the outwale pieces and lock it into the form at location #3 with the dowel and wedge.  Pour boiling water over the outwale between the braces #2 and #3.  Immediately, bend the outwale on to the form until you can lock it into place at brace #2 with a dowel and wedge.  Repeat the heating and bending process between braces #2 and #1.  The entire process is very quick.  The dowel and wedge system allows this to happen with a minimum of delay. 

Once all four outwale pieces are bent, set them aside to dry.  The results vary with each piece of wood.  Some hold the bend with very little “spring-back” while other pieces straighten out a fair bit.  In any case, the wood can be adjusted easily to fit the canoe.

For new stems, I bend the stock (7/8″ thick by 2″ wide) first and then slice it on the table saw to make two stems that are then shaped to fit the canoe.  It is all a bit complicated with lots of trial and error along the way.

At times like this, I think back to my years training to become a Fencing Master.  My mentor was Zbigniew Skrudlik, who had trained the Polish Olympic Men’s Foil Team to 2 gold medals at the 1972 Games in Munich.  As I was struggling for months to learn a particularly subtle and elegant action, I complained about my troubles in mastering something so difficult.  He replied, “If it was easy, then everybody would be doing it.  And if you can only do what everyone else can do, where is the advantage in that?”

Does My Wood-Canvas Canoe Need a Keel?

by Mike Elliott, Kettle River Canoes

If there is an area of controversy in the world of wood-canvas canoes, the question of the keel would be it.

Historically, canoes (and kayaks for that matter) never had keels.  Edwin Tappen Adney documented hundreds of indigenous water craft throughout North America in the early part of the 1900’s.  His meticulous notes, drawings and scale models are presented in the book “Bark Canoes and Skin Boats of North America”.  It was compiled and edited by Howard Chappelle after Adney’s death.  The canoes and skin boats range from small hunting boats around 11’ (3.35 meters) in length to large cargo vessels over 36’ (11 meters) long.  None of these vessels had a keel.

As people of European ancestry came in contact with canoes through the 1800’s and tried to build them, they tended to approach the task of boat building from a European perspective.  For them, building a boat begins with a keel.  The rest of the vessel is built around it.  As canoes became a commodity for the general public, canoe builders also had to appeal to a market that didn’t trust a boat unless it had a keel.  Many people unfamiliar with canoes feel unstable in them and have trouble travelling in a straight line.  As a result, most canoes sold in the better part of the 20^th century were equipped with a keel.  However, it is interesting to note that true working canoes built at the same time (such as the Chestnut Prospector, Cruiser and Ogilvy) were usually keel-free.

The Chestnut Ogilvy was designed to be stable. The wide, flat bottom allows a person to stand up in it all day long. A true working river boat, it never had a keel.

To look at it from a design perspective, the stability of a canoe is determined by the hull shape.  Wider canoes – 36” (90 cm) or more – with flat bottoms tend to have greater “initial stability” than narrow canoes – 34” (85 cm) or less – with arched bottoms.  What is gained in stability with a wide, flat bottom is lost in hull speed and vice versa (what is gained in hull speed with a narrow, arched bottom is lost in stability).  Attaching a strip of wood an inch high to the bottom of a canoe does little to affect stability one way or the other.

The Chestnut Prospector was designed to dance around rocks in rapid rivers.  Although it has a more rounded bottom than the Ogilvy, the tumblehome and high sides in the centre of the canoe gives it very good “secondary” stability.  This means when it is tipped over on one side, it becomes stable in that position.  Also, the waterline width increases as more weight is loaded into the canoe.  Greater width at the water-line equals more stability.

Tracking – the tendency of a canoe to travel in a straight line – is determined by its length.  The longer the waterline length, the better the canoe tracks in the water.  Note here that I refer specifically to the waterline length rather than the canoe’s length overall.  The hull of a Chestnut Prospector lifts dramatically at the ends.  As a result, an unloaded 16’ (4.9 meters) canoe will only be about 14’ (4.2 meters) long at the waterline.  What is gained in maneuverability in a shorter waterline length is lost in tracking and vice versa (what is lost in maneuverability in a longer waterline length is gained in tracking).    If you are simply looking for a canoe that will travel in a straight line, get a long canoe – 17’ (5.2 meters) or more – with no rocker.

Functionally speaking, most canoes are designed to navigate rivers.  The rivers of northern Canada present the traveler with many challenges – chief among them; rapids filled with large rocks.  The Chestnut Pal was equipped with a “shoe” keel. At 3/8″ (9 mm) high and 2¼” (57 mm) wide, it provided protection to the bottom without interfering with the canoe’s ability to sideslip past rocks in rapid rivers.

In lakes, many people complain that a canoe without a keel will be blown around by the wind.  Again, it comes back to learning how to handle the canoe.  When travelling on a large lake with the wind in your face, the canoe must be loaded with a majority of the weight in the forward half of the canoe.  It will always tend to “weather-vein” – that is, it will orient itself with the lighter end downwind.  As long as the weight of the canoe is upwind, the canoe will track easily into the wind.

Speaking as a canoe restorer, I wince slightly whenever I finish preparing a beautifully watertight canvas cover and then proceed to drill a dozen or more holes straight down the centerline of the canoe.  I solve the watertight issue by using a top quality marine bedding compound to set the keel.  Eventually, the bedding compound dries out and/or the keel is jarred by one too many encounters with rocks in rivers.  When the seal is broken, the canoe begins to leak.  It is difficult, if not impossible, to remove the keel without damaging the canvas.  Therefore, when the canoe starts to leak, it is usually time to for a new canvas.

If the question of keels in canoes were strictly one of form and function, there would not be a discussion – a canoe is better off without a keel.  You only have to look at any modern Royalex or Kevlar canoe on the market.  None of the canoes built today have keels – and rightly so.  However, in the world of wood-canvas canoes, there is more to consider.  Many people have grown up with their canoe.  It is part of their life and part of their family.  Their canoe has had a keel for fifty years, so it seems only natural that it stays that way.  In this context I say, “Fair enough.”  It turns out that wood-canvas canoes are more than form and function.  They must be seen in the context of family history and tradition.  For this reason, I have no problem re-installing a keel in a wood-canvas canoe.

How to Photograph a Wood-Canvas Canoe

by Mike Elliott, Kettle River Canoes

People e-mail regularly asking me to identify their canoe and/or give them an estimate on a restoration.  When I ask them to send me some pictures, I often see a big difference between what people regard as a helpful image and what I require, so here is a little tutorial on the art of photographing a wood-canvas canoe.

1.       A General Picture (3/4 Profile)

The first picture I ask for is a general picture in a three-quarter profile.  It is a view taken from an angle to show both the inside and outside of the canoe.  You are standing off to one side near one end.  The picture shows the decks, seats and thwarts as well as giving a good view of the hull shape.  Many people send me a series of pictures of the bottom of the canoe from every conceivable angle.  Other than the presence or absence of a keel, these pictures do little to help identify it or determine the condition of the canoe.  For identification purposes, along with a picture like the one presented above, it is useful to note the overall length from tip to tip as well as the maximum width and depth in the centre of the canoe.  This canoe is 16’ long, 33” wide and 13¼” deep.  I can see two caned seats, a centre thwart, a stern-quarter thwart and two hand thwarts (one at each end near the deck).  From this single picture and the accompanying dimensions, I can identify this canoe as a Chestnut Cruiser (called the Kruger).

2.       Both Decks (Top View)

Take a picture of each deck from directly above.  Be sure to show the entire area from the tip of the canoe to the base of the deck.  If a hand thwart is present (as illustrated above) include it too.  These pictures help me see the condition of the various components at the ends.  There is almost always some degree of rot in this area.  The decal on this canoe shows it to be a Chestnut Canoe built in Oromocto, NB.  The Chestnut Canoe Company was located in Fredericton, NB from 1897 to 1975.  They moved to Oromocto in 1976 and stayed there until they went out of business in 1978.  Therefore, this canoe was built in the period between 1976 and 1978.

3.       Stem-Ends (3/4 Profile)

It helps to have close-ups of the ends taken at an angle off to one side, near the end and slightly above.  In some cases, as in the bow deck above, the damage is obvious.  However, in most cases, it is helpful to remove a few screws from the outwales (and perhaps the stem-band) to reveal the ends more fully.  In this canoe, rot in the stern-end is seen only once the interior surfaces are exposed.

4.       Seats (Above 3/4 Profile)

Take a picture of each seat from above at an angle from one side towards the centre of the canoe.  This view shows the bolts and spacers as well as the seat.  In this canoe, the original 3/16” carriage bolts have been replaced with 1/4″ threaded rod and nuts.  The original cane is in good condition.  Although it is weathered, it could be revitalized with a mixture of boiled linseed oil and turpentine followed by the usual finish of shellac to seal it followed by a number of coats of spar varnish.

 

5.       Obvious Damage (Above 3/4 Profile)

Any obvious damage should be photographed.  As with most photos of the canoe, take these at an angle (to one side and slightly above).  Having the canoe well lit also helps.  Taking the photos from an angle emphasizes areas of light and shadow.  In this canoe, the broken rib and cracked planking are brought into clear view by the angled light.

 All of the pictures are best in a fairly large format but it is not necessary to attach 2MB photos in an email.  As long as the photos are large enough to examine in detail, they will work well.