Balance of oars

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Balance of oars

Post by topherdawson on Thu Dec 01, 2016 10:35 pm

1 When an oar is lying without the rower holding it, the blade floats in the water. To lift the blades from the water the rower has to push the handle down. I am calling this force the Unbalanced Handle Force (UHF).

2 If the weight of the rower's hands and forearms when resting relaxed on the oar handle is exactly balanced by the UHF the oar is said to be well balanced. My measurements of the weight of rowers' hands and arms is between 1.5kg and 3kg.

3 If the UHF is much greater than the rower's hand weight, the oar needs a lot of muscular effort to lift the blade and is said to be "heavy" or "unbalanced". This effort is tiring and unpleasant for the rower. Many St Ayles oars have this fault and the new design must not.(opinion)

4 We are collecting figures for UHF from existing oars. The measurement is made with a spring balance 200mm in from the end of the oar, in the highest gear if there are more than one.

5 In long oars it is hard to keep the UHF within bounds. Despite making the outboard as light as possible, the inboard still needs to be heavier than it needs for strength or stiffness in order to counterbalance the outboard.(opinion)

6 Reducing the gearing makes the inboard longer and the outboard shorter, so it eases both the clash problem and the UHF problem. For this reason I think many skiffs have the gearing much lower than may be optimal.

7 Adding weight as ballast to the handle end of an oar does reduce UHF. Although metal is not allowed, wood is, and can be added as much as needed. If the outboard is as light as can be managed, it may make sense to ballast the inboard to reduce the UHF and make the oar more pleasant to row with.

8 If an oar has different gears, a weaker crew will use a lower gear and thus reduce the UHF, but a stronger crew will race at a higher gear and be strong enough and have heavier arms to accept the higher UHF

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