Pic

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A Gear Shift for Oars, Courtesy of Chris Cunningham, Small Boats Monthly

Sunday, August 14, 2016

Making Spoon Blade Oars

Oars are the ‘drive train’ for an oar cruiser. Just like the engine, transmission and differential in a car, we need them to be sized correctly and strong enough. This post is a rewrite (because I’ve made changes to the oars) of a 2014 article in Duckworks called “New Oars for Raven”.

I searched for oar plans and found these. They are for 7.5' (2286 mm) oars. I expanded the spoon and loom length proportionally to create 8' (2438 mm) oars. I ripped two clear, straight 8' x 4" x 3/4" (2438 x 102 x 19 mm) Radiata pine planks to 1.5" (38 mm) width, swapped two of them end-for-end so the grain would be opposing each other, stacked them (with wax  paper between the two stacks), slathered Titebond 3 on the facing surfaces and clamped tight overnight. Result was two 1.5" x 1.5" x 8' (38 x 38 x 2438 mm) straight oar loom blanks.

Layup of four 8' x 1.5" x 3/4" (2438 x 38 x 19mm) for the two oars

On the table saw, tapered the oar blanks according to the plans. Result was a 1.5" (38 mm) square cross section that ran from the handle end to the lock location and tapered from lock (1.5" (38 mm) wide) to 3/4" (19 mm) wide at the spoon end. I kept the glue joint parallel to the blade face.

Used a band saw to cut the curve into the loom for the spoon blade. The end of the loom was now 3/4" by 1/8" (19 x 3.2 mm).

The band to be glued on the face of the blade came from 1" by 1/4" (25 x 6 mm) Western Red Cedar, tapered down to 1/8" (3.2 mm) at each end.

The blades were cut from 1/4" (6 mm) Okume, after checking that it would make the bend in the blade. I penciled in the edges of both the loom and the ‘band’ on the blade to act as index lines for masking (the blue stuff) to minimize glue spreading.

A trial layup (see below) showed that the loom was not tight up against the blade about 6" (152 mm) from the end of the loom. Using a pair of wedges, I was able to force the loom up against the blade… then glued and let dry for two days. A sigh of relief when I undid the clamps and it retained the required curve.

Layup for gluing the blade to the loom

Using a draw knife, thumb plane, 1.5" (38 mm) plywood template and sandpaper, I rounded the loom starting at the lock, out to the start of the blade.

Tools used to shape the looms

With a chisel, rasp, file and sandpaper, shaped the 5.5" (140 mm) handles. Pictured below is the handle shape (1" to 1.25" [23 x 25 mm] diameter).

Tapered handles

Sanded everything and then applied two coats of Watco Teak Oil to everything except the handles. Added two coats of urethane varnish on the blades. The picture below shows the shape and curve of the blades.

Finished blades

To protect the oar at the lock, I wrapped the loom with mason’s string.

Using Duckworks 5/32" (4 mm) Solid Braid Polyester Line and Nylon Micro Clamcleat with Fairlead, created adjustable stops for the oars which enable quick adjustment for changing the 'gear' on the oars. This works really well.

The picture below shows how the clamcleat is mounted on the bottom side of the oar with the line looping around the lock and hitched to blade side of the loom. The toggle hanging below the lock is a 7/16" (11 mm) cylinder, bored down the center to take a short piece of the polyester line. A slot is cut half the length of the toggle to enable it to pivot (for removing the lock), yet prevent losing the lock during normal use.

Adjustable stop and toggle to hold the lock

The oars have been in use for three seasons. Only maintenance has been a light sanding and another coat of varnish on the blades. There has been no delamination or opening of any glue joints as the result of using only Titebond 3. I’m very happy with the design/build and would do the same for the next pair of oars I build.


2 comments:

  1. Nice oars! Since John DeLapp is a member of our local TSCA I've seen many DeLapp oars - they are very light yet strong enough for normal use. A few have been broken, either at blade or loom, due to hitting rocks or pulling very hard.

    With advice from experts on the wooden boat forum I recently made a set of 9' 6" spoon blade oars for slide seat rowing, trying to copy a friend's Pocock wooden racing sculls but with a softer loom for row cruising. It turned into a long thread:

    http://forum.woodenboat.com/showthread.php?201253-Laminated-spoon-blade-wooden-oars

    The oars have blades laminated from okoume ply in a mold form, and looms laminated from Douglas Fir and redwood. The DF/RW looms are a success, giving a soft flex yet able to take 200 lb on the oarlock location for a 3.6 lb finished oar weight. Flickr album here:

    https://www.flickr.com/photos/ricks_boats/albums/72157660721311014/with/25071585804/

    ReplyDelete
  2. Rick... beautiful sets of oars... you do REALLY nice work!

    ReplyDelete