Suncat and Mouse

N 33° 38' W 117° 55'

Dagger Board Conundrum

December 27, 2011

Happy Holidays! Over the next few months I’ll be posting about various design and build choices and progress on the cat, and I’ll start posting some pictures as well. So to get started, here is the current design conundrum.

The hulls on the hull we want to use are on the narrow side, that’s a good thing for speed and comfort, she will have some claws… but the dagger board casings take up a HUGE amount of space in the very center of the hull. I’m considering moving them to the outside somewhat to gain more space. 

I recently talked this over on a boat design forum with various people, and there was a lot of pressure to keep things standard. It seems that my idea to locate the casings to the very far outer portion of the hull, which would bring the board exit holes about a foot above waterline, is being met with a lot of negative criticism. 

The deal is, they claim this will cause the boards to ventilate, which I gather means bubbles that mess up the flow of water over the foil, slowing you down, and make noise to boot. There was some discussion about raking them forward, which supposedly will alleviate this problem, though most of the posters thought I was crazy to even think about moving the exits above waterline.

The thing is, if the ventilation problem can be overcome, I gain a lot of other positive advantages by doing this. First: I don’t have to worry about marine growth up inside the casings. Second: I have less drag as there are no long holes below my waterline (especially over on the side where the board is up). Third: the casing is out of the middle of my hull, which allows me to use that space for another cabin. Three positives against the one negative.

My next order of business is to meet with the builder and designer and discuss the possibilities, and see if they think the ventilation issue can be mitigated with a forward rake of the boards. At worst, I want to move them over toward the outside hull, and tilt them slightly in at the bottom, out at the top, though with the exit under water. But, if possible, I want to rake them forward, and have the exit above waterline. I’ll let you know which way they recommend after we discuss the possibilities.

The picture shows the dagger board casing in its current position, you can see how much space it is consuming.

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