4.3m 75x54 hollow cedar/ply outboard oar

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4.3m 75x54 hollow cedar/ply outboard oar

Post by topherdawson on Sat Mar 04, 2017 1:58 pm

This oar was made by Topher Dawson in Ullapool. It has been rowed with for about two weeks.

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Re: 4.3m 75x54 hollow cedar/ply outboard oar

Post by topherdawson on Sun Mar 05, 2017 1:19 pm

4.3m oars suit the bow position and also positions 2 and 3 if the pins are fitted to blocks on the inside of the gunwale.

This oar has a rectangular section 75x54 solid ash inboard and a hollow outboard with Western Red Cedar flanges (front and rear strips) and 4mm okoume plywood (Robbins Elite like the skiff kit) webs on the top and bottom. Adaptations of this design are available for Spruce and Douglas fir.

The WRC strips are 12mm thick at the pin, tapering to 3mm at the tip which is alarmingly thin, but it works. This oar was actually made with strips about 1mm thinner than this because of a manufacturing fault, and thus has a deflection of 100mm which does make it softer than most rowers like.

The total weight is 4.24kg and the UHF at gears of 3.0, 2.8, 2,6 are 1.87kg, 1.5kg and 1.2kg.

Smaller rowers like it because of the light UHF, but have commented on the soft feel. A big rower using the oar at 2.8 gear in a heavy headwind complained that it was too light and he found it awkward to row with. I usually row with this oar and have adapted my technique to its lightness which I now like. I have heavy 3kg hands and forearms.

The shaft is bulkier than the solid oar and so has more windage, and may be entraining more water at the neck of the blade.

The build needs a jig of 10 stations accurately cut out of plywood and mounted on a straight base. Adding this to the build time means I'd estimate 50 hours to build 4 oars.

The material cost comes to £75 per oar, compared to the £100 for solid oars, reflecting the reduced amount of wood.

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Re: 4.3m 75x54 hollow cedar/ply outboard oar

Post by topherdawson on Sun Mar 26, 2017 9:39 pm

Design 4 4.3m 75x54 Hollow outboard ash/cedar/4mm plywood oar
This oar has a hollow outboard with tapering cedar strips fore and aft, and 4mm plywood webs top and bottom. It takes longer to make than a solid oar but uses less timber.

The Unbalanced Handle Force (UHF) @ gearing of 3.0 = 1.87kg. @ 2.8 = 1.5kg @ 2.6 = 1.21kg.

Total weight = 6.23kg and deflection at 10kg at 2.5m = 100mm which is a bit too soft.

Build time 25 skilled hours. Cost of timber about £60.

This oar, the first hollow one to be made, is popular among rowers though softer than optimal. It is very light to row with.

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Re: 4.3m 75x54 hollow cedar/ply outboard oar

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