Winter is here, I have 5 coats of varnish on the inside of the GIS, will try to get two more on then paint on the outside if we get a warmer week in the next while. Too cold for sailing now, so I'm concentrating on getting set up for rowing for some of the clear, crisp days we should get a little later in the winter. -5 celcius in the air and +9 in the water and the water will have smoke on it on a calm day.

So onto the oars, I've had a go at making them as lightweight as possible. Hollow shafts from radiata pine and paulownia, blades from slightly tortured 4 mm ply. Weight at the moment is 1.4kg each, but I will get some glass on the shafts through the rowlock area and possibly on the blades.

This is my shaft glue-up. I think if I was doing it again, I'd have a go at hollow birdsmouth, it should need less shaping and be easier to get consistent wall thickness and taper.
Attachment 171534
Shaping the blanks:
Attachment 171536
I like old tools.
Attachment 171535
The plane is from my Grandfather, the adze started its life in Hiroshima in 1920, so has seen quite a bit of history.

I made the blades from 4 mm gaboon, to Mik's pattern, but cut a slit from the tip down to halfway. The slit was 7mm wide at the tip tapering to the half a mm saw kerf width at the other end. I then wired the tip end together, which established a curve and some spoon shape, then glued this together with a paulownia batten down the middle and thin battens across the tip either side of the plywood. Next set, I'd make this batten from Vic Ash (hardwood) so the blade is stiffer.
The final slit went further than this picture shows:
Attachment 171541
Blade glue-up:
The pieces that go across the blade tips are wooden venetian blind battens. A great source of thin bits for laminating, easy to pick up some up from the Salvatian Army store, I found some made out of close grained hardwood and also some from WRC.
Attachment 171537
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Blades and shafts ready to go together:
Attachment 171539Attachment 171540


Shafts and blades glued together:
Attachment 171548
Oars cleaned up and ready for some glass on the shafts and possibly the blades:
Attachment 171549
Attachment 171550
The handles are Jarrah to provide a bit of counterweight.
Attachment 171551
Attachment 171552
Attachment 171553
The shafts seem reasonably stiff.
(These bend 16 mm with 20 kg on a 2 m span, which is a stiffness about 2 kNm^2, which is the same as one of Mik's spars which bend 50 mm on a 3.5 m span with 10 kg).

I'd be keen to know what are reasonable ballpark figures for oar stiffness, I'm new to 'real' rowing, so don't have a good feeling for what is stiff enough.

The blades are a bit too flexible, I think I'll shave that paulownia batten on the inside down a bit and add a thin strip of hardwood to stiffen it up. A layer of 2 oz glass either side is also a possibility.

Final all up weight is looking like 1.5 kg each.

I'm thinking about another set with shafts from fibreglass tube, I'll make the blades the same, but the shafts will come apart in the middle so I can fit them right up the front of the boat. Does anyone have any specs on fibreglass or carbon oar shafts, what is a typical outside diameter and wall thickness for glass or carbon shafts?

I'm keen to eventually set the GIS up for two person rowing, so it will be good to have two sets.

Ian