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New Oars for Hatseflats Part 1

Why new oars?

After 7 years of hard use my trusty Lahnakoski oars squeaked alarmingly with every stroke. My friend Joost said that the oarlocks were crying for lubrication. But it was too late. There was so much play between the oarlocks and their sockets that I had to replace them. I went to the Bootbouwer for a new set of bronze oarlocks and sockets but the bronze oar locks for the Lahnakoski oars were not available anymore. What to do?

Joost had a spare set of sockets and square oar locks that I could use. The sockets were identical to the old ones so fitting them to the gunwales was a piece of cake. The old oarlocks still fitted the new oarlocks but with some play. So I had to use them carefully and lubricate them every time with leather grease.
However, it looked I could no longer use the old Lahnakoski oars with the new square oarlocks. So I needed new oars. That sounded like a lot of work. And that it was!

Experimental oars!

The easiest solution would have been to repurpose some carbon racing oars for Hatseflats. Racing oars already have collars for square oar locks. However, I am not a great fan of carbon fibre on small boats. You have to treat them really carefully and when they get damaged you end up with the worst possible splinters in your flesh.

Joost likes carbon, but indicated that carbon is not so suitable for small and slow boats (sorry Hatseflats). Our small cruising dinghies don't plane and need to have some volume to stow all that gear, so the extra pull from carbon oars simply goes to waste. In order to row comfortably (at a slightly lower pace) you even want the oars to be a little more flexible than my Lahnakoski oars.

The starting point for my new oars were the plans that Joost had created in 2018 for the Goat Island Skiff. The benefits of these oars were: slightly more flexible looms for more comfort and spoon blades for rowing with less effort. These plans had been used for years and been proved in practice. Job done, you would say.

However, Joost suggested a little experimentation to greatly simplify the building process. The original plans required laminating the oar blades from two or three layers of 3mm veneer. So apart from getting your hands on suitable okoume veneer there was the challenge of laminating the veneers into the required shape for the spoon blade and carve out the corresponding hollow in the looms to a close fit.
The experimental approach suggested by Joost was to make brutally simple blades from 4mm plywood, reinforced with 200g glass cloth on the hollow side and a simple rib on the backside. Since the spoon blades had a very tight curve halfway the length of the blade, there would be no need for elaborately carved looms to receive the spoon blades, like in the plans. Instead, a simple straight taper on the last foot of the loom would suffice to fit the blades on the looms.

More experiments

I started by creating new blades using an earlier experiment by Joost as a reference. With a length of 60cm and a width of 13cm my blades were going to be only slightly wider than my existing Lahnakoski oars. I did not need extra power but more comfort: I hoped that the spoon shape would mean less strokes and that the narrow blades would be comfortable in waves.

Joost and I discussed the shaping of the looms, the end of which was that I would use the online drawings of the oars that Joost had made for the Goat Island Skiff. I used the building notes created by Joost to understand the building process and consulted the drawing for the correct dimensions. Only a couple of changes were required:

keep the section of the looms square until after the collars.
add a straight taper to the last 30cm of the loom to accept the experimental blades.

However, I inadvertently used the drawing from Duckworks made by Michael Storer. Stupid I know. Because the dimensions in the drawing were slightly different, I used my common sense to work out the dimensions myself. Only today I downloaded the proper drawings by Justin Wimpey. It looks like the dimension in the drawing are not so different from the ones I chose. Lets keep our fingers crossed!

Dimensions

Unaware that I was not using the correct drawing, I came up with the following dimensions:

blade: 610x132mm - see photo for more measurements
loom dimensions: 44x44mm
handles: 34mm x 180mm
untapered length: 950mm including 180mm handles
tapered length: 1460mm
vertical taper: straight taper top and bottom from 44mm to 30mm
horizontal taper on outside of loom: none
horizontal taper on inside of loom (to which the blades are attached): straight taper from 44mm to 30mm

Building the blades

Created a 600mmx132mm blank out of 8mm plywood
Created 4mm blade using the blank
Cut 2 27x4mm ribs from solid pine with 100mm extra length
Created a jig to bend the blade and ribs with a sharp bend at 280mm from the pointed tip
Glued ribs together with blade into the jig and fixated the blade with screws etc.
Sanded the backsides of the blades
Added 280g glass cloth and epoxy on the hollow side of the blades
Coated the hollow side of the blades for a second time to ensure that total permeation of the glass cloth

Building the looms

I laminated two 2700x44x44mm oregon pine looms from two staves of 44x22mm each.
I used a router to locally reduce the looms to 34x34mm for the handles. With the router I cut 5mm notches across the last 180mm of the looms. After cuttting out the notches on all four sides of the loom, I chiseled out the remaining ridges.
I then used a surform to convert the square handles into octagonal handles. And rounded them with 60grit sanding paper.
After shaping the handles, I cut the looms to 2410mm.
I marked the vertical tapers starting from 950mm from the tip (including handle).
Planed vertical tapers by hand (No 3 plane).
Marked horizontal taper on the inside of the loom and planed by hand.
Created straight taper for the last 280mm of the inside of the loom to accept the blade.
Rounded the corners with the router and a 15mm bit.