New Daggerboard for Owl – Part 1

Owl needs a new daggerboard. The current one is plywood and might be getting weak. Given I might need to stand on it to right Owl after a capsize this needs sorting.

Owl’s daggerboard – a big slab of plywood

Plywood is generally a bad idea for centreboards, daggerboards and rudders on dinghies as half the wood grain is running in the wrong direction. Once the thin outer skin buckles there isn’t much strength left to hold it all together. In any case it looks like Owl’s daggerboard has the outer skin of the plywood running across the board rather than down it – unconventional although this might be deliberate to put the load into the thicker underlying plys.

The board is 16.6mm thick, 410mm wide and overall 912mm long including the handle on the top. The part within the boat (dagger board casing) is 345mm.

Design considerations

The daggerboard is currently too far aft. I don’t think this hull was ever really designed as such – the fact that the original rudder only just touched the water is a hint – and the daggerboard case is too far back. If I taper the back edge of the daggerboard somewhat this will help a bit. Making the daggerboard longer will help the aspect ratio but also making the board harder to handle. Still a bit longer should be ok.

Given how thin the board needs to be, the profile is going to have to be Neil Pollack’s design for a parallel sided foil. I’ve put this into a spreadsheet for ease of use.

Other Owl Jobs

I need to re-finish the woodwork – this was done in Woodskin so that shouldn’t be too hard once the weather warms up.

I would like to get more buoyancy into her – I don’t have a huge amount of confidence in the built-in buoyancy given the design standards of the rest of the boat – so a couple of buoyancy bags under the seats wouldn’t be a bad idea. I will need to mend one of the seat supports and make sure everything is strong enough to take the load.

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