Making Oars

What follows is a description of the 7-1/2' oars I made for my eleven foot dinghy. I blended features from John Murray's and John DeLapp's oar designs to create a set of oars I'm quite pleased with. Included in this Instructable are the design descriptions I used from the original authors. You can find the links to their PDFs at the bottom of my "Supplies" list.

An oar is a simple object, but building a pair of oars requires a fair amount of planning and material selection along with some woodworking and epoxy skills. I'm hoping this Instructable inspires you to plan an oar-building project because it’s very rewarding to row with a pair of oars you built.

Materials

Oarlocks (I used Gaco oarlocks and sockets)

Clear western red cedar fence boards

3mm Lauan plywood

Epoxy (I used West System 105 + 205)

Epoxy thickener (I used West System 406)

Wood flour epoxy thickener

6 oz fiberglass

Dynel cloth

2” packing tape

Masking tape

Hot glue

Contact cement

5mm thick vegetable tanned leather (eBay)

0.5mm thick elastic exercise band material

12" Velcro cinch straps

2-1/2" hose clamps

Heat shrink tubing

2x2

2x4

2x12

4x4

Tools

Circular saw

Table saw (optional)

Thickness planer (optional)

Band saw (optional)

Dremel tool with 5/8” drum

Fine Japanese pull saw

Hand plane

Coarse file

Clamps

Polyethelene drop cloth

Foam rollers

Chisel stick (sharpened tongue depressor)

Acid brushes (Harbor Freight)

Small screws

Sandpaper

Emery cloth

Utility cutter

The perfect wood for making oar shafts is strong, knot-free, straight-grained and lightweight. The oar shaft design I followed requires one piece of lumber measuring a full 8' x 4" x 2". To get this, you will most likely have to laminate two or more boards together. I chose to laminate western red cedar boards because they are lightweight, easy to shape and affordable. In my region, six inch wide cedar fence boards are commonly available at home improvement centers where it is easy to sort through a pile of boards to find ones well-suited for this project. You can use whatever wood is popular in your area, but I recommend only using reasonably-priced lumber when building your first set of oars.

My 8' x 4" x 2" piece of wood was made from five 8' x 6" x 3/4" rough sawn western cedar fence boards. I selectively ripped them to 4-1/4" wide, making an effort to retain the best part of each board. The rough sawn boards were planed to 0.4" thick and laminated together with epoxy, one board at a time. This slow process enabled me to control the lamination much better than simply gluing five boards together at one time.

My stack of five boards was formed on top of a very straight 2x4 covered with a polyethylene drop cloth to prevent any epoxy from sticking to it. I rolled epoxy on the face of the boards I wanted to glue together, followed by a coat of thickened epoxy (consistency of ketchup) to help fill air voids. Enough thickened epoxy was applied so some would squeeze out when the clamps and heavy blocks forced the boards together. Seeing the squeeze-out was visual confirmation the boards had a uniform layer of epoxy adhering them together. Any epoxy that squeezed-out was removed with a chisel stick and paper towels. After all five boards were laminated together, I ripped the 8' x 4-1/4" x 2" stack wood to its final 8' x 4" x 2" dimension. Ripping the laminated board trimmed away any slight board misalignments and leftover epoxy. To get the straightest cut possible on my first rip, I screwed a very straight 8' long board to my laminated stack to act as a fence guide. The screws were placed near the ends of the stack because those parts get cut off.

Cutting the 8' x 4" x 2" board three times at 10 degree angles, produced two tapered, trapezoidally-shaped oar shafts ready for hand planing.

I calculated the finished length of each oar to be 1.9 times the distance between the center of the oarlocks. This measurement included the oar blade too. I cut both tapered shafts to the calculated oar length, knowing some of the thin end of the shaft would be cut off when I fit the blade to the shaft.

The drawing showing how to make the three cuts and the oar length formula are John Murray’s.

Each of my oar blades was made by laminating two 21-1/2" x 6-1/2" sheets of 3mm Lauan plywood. The spoon shape was formed by holding the sheets in a jig while the epoxy hardened. The jig gave me good control of the blade-forming process and enabled me to completely finish the blades before attaching them to the oar shafts.

To build the jig, I started with a 28" piece of 4x4 lumber and laid a full-scale, cardboard template of John DeLapp’s blade profile on its side. I hammered several small nails through the template along the blade's profile and clamped two narrow strips of Lauan plywood to them. I traced around the clamped strips of plywood to mark what part of the 4x4 had to be cut out with a bandsaw. Removing this wood made room for the Lauan sheets that would be held in the jig until the epoxy hardened. It was important to remove enough wood and smooth the curved surface so the jig made uniform contact with the curved Lauan sheets.

To support the corners of the 6-1/2" wide Lauan plywood in a 3-1/2" wide jig, I attached four 2x2 “ears” to the corners of the jig (shown in the next section). The curved jig surfaces were covered with multiple strips of 2" wide clear packing tape to prevent any epoxy from sticking to it.

I lightly penciled the final oar blade outline in the center of the top sheet of Lauan plywood. I drilled a small reference hole 1/2" above the blade's finished point for a screw to hold both sheets to the jig. This would maintain the plywood’s alignnent in the jig during the clamping process. I did a dry-fit test of all the pieces and then placed some polyethylene plastic sheeting under the jig to catch any epoxy that squeezed out from the blades.

I wet the two plywood surfaces that faced each other with epoxy and then generously coated them again with thicken epoxy (consistency of ketchup). I pushed the screw through the reference holes in both pieces of plywood and screwed them to the bottom half of the jig. I centered the square end of the blade in the jig and set the top half of the jig on top of the plywood. Clamps were added to jig being careful that the Lauan did not shift out of place. Seeing some thickened epoxy squeeze out convinced me I had a close fit with no air voids. The epoxy that squeezed-out was cleaned up with a chisel stick and paper towels. Whatever you use to thicken the epoxy, it will impart a "ghost" color to the unfinished plywood. So, you'll want to avoid any stray drips of thickened epoxy on the blades. To minimize any blade springback, I let the epoxy fully harden before releasing it from the jig. I left the blades in their rectangular shape until after I transfered the blade's curved profile to the side of the oar shaft as described in a later section.

John Murray points out that an oar has two planes: the passive plane that supports the weight of the oar and the active plane that resists the force of propelling the boat. The active plane needs to be stronger than the passive plane. This is an important concept to understand when deciding what wood to leave on the shaft and what wood to remove. This is critical where the oar shaft is cradled by the oarlock. There, the oar needs to be strong, but must easily rotate in the oarlock for proper feathering. Exactly where the oar shaft is cradled by the oarlock varies from boat to boat and by the people who row them. Factors include, the width of the boat, does the person like to row with the oar buttons against the oarlocks, what hand positions do they plan to use while rowing. Some rowers like to row with overlapping hands, some like to row with their thumbs on the ends of the oar handles, etc.

I started shaping the trapezoidal oar shafts by rounding the corners with a hand plane. I formed 3/4" radii on the widest side of the oar shaft and 1/2" radii on the narrowest. A good wood removal strategy throughout the shaping process for me was to remove small amounts of material from both shafts and compare them. This helped keep the final shafts identical in both shape and weight.

Some rowers like to have their oars heavy above the oarlock. This extra weight can improve the hand balance weight or how much downward force is required to hold the oar above the water during the return stroke.

My hand grips are 5" long with a squarish 1-3/8" by 1-1/8" oval cross-section, this shape helps index the oars in my hands. I rough-cut the handle almost 5" deep with bandsaw cuts. Notice the "leg" hot glued to the shaft to properly square the trapezoidal shape while I made two of the cuts. The unneed sections of wood were carefully removed with a fine Japanese pull saw. I made sure to leave some wood where the handgrip met the oar shaft body so I could radius it with a 5/8" diameter Dremel sanding drum. The grip was smoothed with a coarse file and emory cloth to the desired shape. To strengthen where the handgrip met the body of the oar shaft, I laid a 3/4" radius fillet of wood flour thickened epoxy (mayonaise consistency). The wood flour gave me the best color match with the shaft.

I traced the side profile of the curved oar blade on to the side of the oar shaft using one of the rectangular, untrimmed oar blades. After that, I cut one of the oar blades to its final shape because it’s needed in the step below.

My finished oar blades are 21" long, 13" of the blade is supported by the shaft and 8" is unsupported. My shaft is 1-7/16" thick where it meets the top of the blade. The shaft is 1/4" thick where it stops supporting the blade. This blade placement was determined with a bit of "eye balling" so there was a natural straight line when looking down the shaft from the handgrip. I removed wood from the shafts with a band saw so they matched the blade profile.

Now that the blade profile had been transferred to the shaft, I was free to trim the plywood blades to their final shape. I coated the top and bottom of the blade with epoxy, leaving the edges uncoated so the reinforcements could bond directly to the plywood. After the epoxy cured, I applied a double-thick layer of masking tape (double thickness is extra stiff) around the blade tip and sides forming a dam to hold thickened epoxy to reinforce the edges of the oars. For good adhesion to the wood, I wet the plywood inside the dam with epoxy. Then, loaded a disposable plastic pastry bag (any thick plastic bag works) with thickened epoxy (mayonaise consistency) and snipped-off the corner of the bag. Squeezing the bag enabled me to force epoxy into the space between the dams, about 1/4" high. I was careful not to form any air pockets while doing this. After the epoxy hardened, I removed the masking tape dams and filled any air pockets. When satisfied, I filed the reinforcement epoxy to the desired shape. To further reinforce the flat end of the oar, I applied a layer of fiberglass to the top and bottom of the and trimmed the excess away after the epoxy cured.

When epoxying the blades to the shafts, proper alignment is very important. To simplify that step, I drilled two holes in each blade for small screws to hold the blade to the shaft while they were epoxied together. One hole was 1/2" below the blade point of the blade and the other hole was 12-1/2" below the point of the blade. These screws enabled me to establish exactly where to attach the blades before applying the epoxy. With the screw points slightly protruding from their holes it was easy to re-find the blade's position on the shaft, even after the epoxy had been applied to both surfaces.

After doing a dry fit of all the parts including the clamps, I applied masking tape on the blade next to the shaft. This made it easy to clean up any thickened epoxy that squeezed out after tightening the screws. Before applying the epoxy, I lightly sanded the epoxy on the part of the blade to be joined to the shaft. Then, the blade and shaft surfaces were wetted with epoxy, followed by a coat of thickened epoxy (ketchup consistency). Using the protruding screw tips as a guide, I aligned the blades with their shafts and tightened the screws.

Notice in the photo how the oar shafts rested on a 2x12 base so I could reference the blades and shafts with each other using small boards and clamps. This assured that all the parts would be in close alignment after the epoxy hardened. The next day I removed the two screws and all the clamps. The two screw holes were filled with wood flour thickened epoxy, being sure to push the epoxy deep in the screw hole with a toothpick.

After the shafts had been trimmed and sanded to their final shape, I firmly burnished the entire oar shaft with a smooth, round metal rod, something like a round screwdriver shaft. This compressed the outer layer of wood so it was denser and less likely to dent during use. To protect the shaft from repeated forces from the oarlock, that area was covered with a protective layer of epoxy-soaked Dynel fabric. The wide side of the oar shaft that has the forceful contact with the oarlock was covered with two layers.

Wetting Dynel with epoxy is different than wetting fiberglass. Fiberglass tends to drink up epoxy while Dynel tends float on top of epoxy. Experts recommend loading the Dynel with epoxy and then transferring the cloth to the object to be covered. Watch these Jamestown Distributors videos to get a preview of how it works: part 1 and part 2.

I applied masking tape on the shafts as guides where to place the epoxy-soaked Dynel. I made marks on the tape to remind me which direction I wanted to wrap the cloth. After the cloth was applied to the shaft, I laid a strip of masking tape under the end flap of Dynel. The edge of the masking tape was the guide I used to cut the Dynel with a utility knife before the epoxy had reached full hardness. After making the cut, the tape offered me a way to lift up the excess fabric.

After the epoxy had fully hardened, the Dynel edges were tapered with a sanding block, the oar blades were lightly sanded and then, the whole whole oar was given a coat of epoxy. To simplify the epoxy process, the blades were coated with epoxy and then a day later the shafts were coated.

An oar buttton stops the oar shaft from sliding completely through the oarlock. Since I like to row with the button against the oarlock, the button placement had to be determined through trial and error. Someday, I may permanently attach my buttons to the shafts with contact cement, but until then I have devised a way to secure them on the shaft so they can be moved whenever I wish. I can even move them when I’m out on the water.

The buttons were made with two 8" x 1-1/2" x 5mm pieces of vegetable tanned leather. To increase the tackiness of the leather, I backed them with a layer of 0.5mm thick elastic exercise band material. Using an acid brush, I painted several layers of contact cement on the rough side of the leather, letting each coat dry before adding a new coat. Then, stretching the elastic material a bit, I taped it to the table top so it did not buckle after painting it with contact cement. When the cement on both surfaces was dry, but still tacky, I firmly pressed them together and trimmed most of the excess elastic material off with scissors. Then, I transfered the leather pieces to a 2" ABS pipe and clamped them in place until the cement fully set.

Later, while the leather was still wrapped around the 2" pipe, I closely trimmed away the excess elastic material with a sharp knife. The length of each leather strap was trimmed so there was a 1/4" gap between the ends when wrapped around the oar shaft at the estimated oarlock position on the shaft.

I've found that the force from 12” velcro straps is powerful enough to hold the buttons in place on the shafts. If a more secure attachment is desired, a pair of #32, 2-1/2" stainless steel hose clamps can be used instead. A segment of heat shrink tubing around the screw mechanism can protect any edges that might scratch the boat.