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THE STRIP CONSTRUCTION

Wooden boats in strip construction are light and robust with a high practical value and an elegant appearance. The composite construction of wooden strips and GRP (glass fiber reinforced plastic) does not represent a compromise between aesthetics and weight , but is usually even lighter than other materials in the canoe and kayak market. Depending on the used wood types and fabric grammatures, boats with a weight of well under 20kg can be realized. In terms of craftsmanship, the strip construction method is extremely demanding, as not only precise work is required while planking, but also a clean finish when laminating and varnishing the hull. In addition to the required craft qualities, a great amount of stamina is required for large-scale sanding work. The result, however, justifies all the effort: paddling your own stripcanoe for the first time is truly unforgettable.

 

evening mood in the canoe building workshop. the sun shines through the slipway. some battens are already mounted. screw clamps are ready. backlight and lensflare.

HERE WE GO: THE STRONGBACK

Every construction of a stripplanked boat begins with a strongback. It is the frame on which the strips are forming the shape of the hull. Since the stations are attached to the strongback and the symmetry of the boat depends on it, it should be as straight as possible and also very stable. The hull strips will later be attached and glued over the hulls. The stations are removed after the canoe is built and can be reused in the same way as the strongback.

SAWING LIKE A DUMB

Once the strongback is in place and the hulls are aligned, all that is missing is the appropriate wood strips for planking. The ideal wood for a wooden stripplanked boats is Red Cedar (Thuja plicata), because it is very light, has an insanely beautiful appearance and is also very easy to process. Another advantage of the wood is the aromatic smell it gives off when sawn, planed and sanded. However, when processing this wood, a filter mask should be worn urgently, as the dusts are harmful to health.

Several hundred meters are traveled on the saw and router table in the production of these 6mm thick, approximately 20mm wide, concave and convex milled strips.

 

detailed view of the saw blade of a table saw sawing a board of ash
top view on a not yet finished stripcanoe build. you can see the stations, the strongback, a handplane and a ruler. some strips are held in place with small wooden blocks while gluing

PLANKING

A basic decision should be made before attaching the first strip: "with or without staples?" Stapling the strips to the stations has the advantage that the hull can be completed faster, since strip after strip can be attached without having to wait for the glue to dry. Visually, however, this method has the disadvantage of leaving trails of small staple holes evenly spaced on the hull later.

Better, but also more complicated, is the construction without staples, for which there are countless, more or less laborious approaches. Instead of stapling, I recommend placing screws in pre-drilled holes only where necessary and closing the screw holes later with wooden dowels. Screws because a few screws have to hold more forces than many staples. A few irregularly positioned wooden dowels are almost unnoticeable on the finished hull and also give the hull a kind of traditional look like that of clinker boats.

Glue residue should always be removed immediately with a damp cloth, since dried-on glue will later block the sandpaper and make the sanding process more difficult.

Finally, an oval hole is left towards the keel, which has to be closed with strips, becoming shorter and shorter. The last strip is called the "whiskey plank" and is traditionally celebrated with whiskey.

When building a strip kayak, the hull and deck are made on the same strongback, but the two resulting shells are sanded and laminated separately before later being glued together to form the finished kayak. Gluing the two shells together through the small cockpit opening is very challenging and requires a lot of skill.

SANDING ... SAAAANDING

 

Sanding takes the most time of the entire construction of a stripplanked boat and demands a lot of patience and stamina from the canoebuilder. However, the overall beauty of the finished canoe depends significantly on the quality of the sanding work, so you should take plenty of time here.

The closed hull remains on the strongback. A random orbital sander is well suited for rough pre-sanding on the outside. It is important to work evenly over the entire surface. To remove glue residue, one is tempted to edge the sanding disc, which should be avoided , as this can cause deep dents that are still visible on the finished laminated canoe. The Hull is sanded down to 120 or 180 grit so that the epoxy resin will later find a structure to adhere to. The sandpaper is attached to a large, not too soft sanding pad that follows the contours of the hull. Sand by hand in the direction of the grain of the wood until an even surface is achieved. The best way to check the progress is to examine the hull in glancing light. Finally, the hull is wiped with a damp cloth so that the wood fibers rise. These are removed in a final sanding and the hull is ready for lamination. After laminating the outside, the inside is sanded. Here, the random orbital sander can be used carefully on the bottom of the hull. The inside of the hull is mostly handwork. Depending on the radius, you should look for different pads for the sandpaper here, which produce an even sanding in the radii.

 

top view of a wooden stripcanoe that is being sanded

FROM WOOD TO GLASS...

a boat builder uses a scale to measure the components of the epoxy resin used to build a stripcanoe. he wears nitrile gloves to protect his skin. the componentes are measured in plastic cups

LAMINATING

Laminating a wooden hull with fiberglass-reinforced plastic (GRP) is one of many composite construction methods in boatbuilding and has become very important in modern wooden canoe construction. You can see how delicate and fragile a canoe hull is once you take the raw wooden hull off the strongback: an estimated 20% of the stability comes from the wooden hull, 80% from the GRP. So the wood is the component that gives the canoe its shape and appearance, but not its stability.

A fiberglass fabric is now placed on the cleaned hull and smoothed out with a brush. The fabric should be handled with cotton gloves so that it does not get grease spots to which the resin will not adhere later. Fabrics in twill weave are particularly suitable, as they adapt to contours better than fabrics in plain weave. An epoxy resin with a long pot life is used to saturate the fabric so that there is plenty of processing time. Work is done from one tip to the other. The resin is applied with a large brush and allowed to soak into the wood for some time. For this purpose, the resin should not be applied too thinly, otherwise dry spots may occur if the wood is very thirsty. Once the wood is saturated, carefully wipe off excess resin with a squeegee and dispose it. The correct pressure and angle of the squeegee is critical here. If too little pressure is applied, too little resin is removed and the fabric could float in the resin, creating bumps that you can sand into later. If too much resin is removed, the fabric will be too dry and white spots will appear in the laminate, which will also be visible on the finished boat.

FILLCOATS

The first pass of lamination serves to saturate the fabric and ensures adhesion of the fabric to the wood. After the excess resin has been removed with the squeegee, the fabric structure is visible again, which must now be filled with several "fillcoats". The time to apply the first fillcoat has come when the resin is still tacky, but no longer pulling threads. Do not test this with your bare finger, but with a nitrile glove! Fillcoats can be applied slowly with a solvent resistant foam roller. If you roll too fast, small air bubbles will remain in the resin, which you can remove promptly and carefully with a hot air gun.  Apply as many fill coats as necessary until a sufficient layer of resin has built up to allow subsequent sanding. Do not sand into the fabric, as this will leave white spots. You can find more tips on processing GRP and on health & safety in the blog.

detailed view of the glossy epoxy resin surface of a freshly laminated stripcanoe. a light ash strip is incorporated into the precisely fitting planking of red cedar strips