Shallow or Deep?


Shallow or

We must admit that we really enjoy this Ask
series and encourage y’all to get your questions in – boat
design, sailmaking, rigging, navigation, weather, tactics, boat building.
You want it – we got it. Designer Merfyn Owen from Owen
Clarke Design
handles this mini question.

Q: This question has to do
with the Open 5.70 having 2 keel positions, 1 regular and 1 for shallow
draft. In Big Winds @30, could it actually be faster to have the keel
in the shallow draft position? This might sound counter intuitive, but
follow this logic for a sec. The M20, Viper etc draw less than 5′. The
open in the full down is 5′ 9" which is a lot of blade in the water.
The shallow draft is 4′ 8" which is more like the other 20s. Less
blade = less drag at speed. It also means a little more side slip which
can be good and easier to hike the boat down and less heeling force.
So with a bit more meat on the rail in a big breeze I could see this
actually helping control and being faster especially downwind and not
hurting upwind as long as the wind is up high. This paired with the
first reef in over 30 might be interesting to try. Part of the super
deep draft is to have the righting moment to have the boat right itself
after a capsize since the beam is fairly extreme. More beam = deeper
blade to get to the correct righting moment.