Roundovers on leading and trailing edges of rudder.

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Re: Roundovers on leading and trailing edges of rudder.

Postby JonLee on Thu Oct 30, 2014 5:37 pm

Yes...no...well.....

More complicated geometry=more complicated construction. But, while making PocketShip's rudder's trailing edge sharp instead of blunt might technically reduce drag a little, you'll never see it in the performance of the boat.

In terms of shaping the rudder, there would be a benefit to a NACA0012-shaped foil for a spade rudder, or for a rudder that extended below the keel. For Pocketship's geometry, the rudder is essentially part of the airfoil shape of the keel, similar to how a rudder on an airplane is part of the airfoil shape of the vertical tail. In this case, the single best thing you could do to increase rudder effectiveness is to minimize the gap between the trailing edge of the keel and the leading edge of the rudder. I've imagined even a few schemes to add a wiper seal between the two. But, PocketShip's rudder is totally capable, so It have never seen a need to implement the idea, other than geekiness.
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Re: Roundovers on leading and trailing edges of rudder.

Postby DanaDCole on Thu Oct 30, 2014 6:01 pm

I totally agree. I went ahead and rounded things some, mostly because I don't like sharp corners on wood.
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Re: Roundovers on leading and trailing edges of rudder.

Postby craig on Thu Oct 30, 2014 7:06 pm

Thanks for the detailed explanation, Jon. It's really interesting learning these engineering principles, even if the gains in real world performance is marginal. One of the reasons I built a boat instead of bought one is that I was so interested in the "why" of the design, and building pocketship and conversing with everyone on this forum (and others) has certainly not disappointed!
Titania, launched January 2015
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