A Single Daggerboard

If you own a cat and are not happy with its windward performance, you have come to the right place.

Whether you own a boat or you’re building one, what you choose for daggerboards could be the most important decision you make, it dramatically affects how well your cat will go to wind.

A single large daggerboard with 150-200% more area than the typical 2 boards combined means your cat will point high like a monohull, and it will go upwind faster!

These single boards use a NACA 63-012 profile which has good lift-drag characteristics, suited to both cruising and racing.

The large side area keeps the operating range of the board’s angle of attack inside the drag bucket, meaning less drag, more speed and low loads on steering.

A single large daggerboard

outperforms two smaller ones. Go as hard to wind as a keel yacht—but faster.

Add performance and space

racing catamaran

One large board – is better than two 

Vortex losses around the daggerboard tip make up a considerable percentage of the total drag. One board cuts that in half. Combining two boards into one increases chord, giving a higher Reynolds number and lower induced drag. The larger surface area means the board operates at much lower angles of attack resulting in a higher Lift/Drag ratio, less side slip and much better steering.

Unhappy with my original windward performance I went back my boat shed and built a solution.

When I relaunched my cat it was a different boat—completely. I could go upwind like a tractor at angles I’d never before seen—and fast.

More importantly, I could go upwind slowly. When the weather turns foul this ability is so important. 

The steering remained light even in the heaviest of conditions and the boat tracked like it was on rails.

Asymmetric drag is undetectable, it makes no difference on what tack, to the speed or helm.

Building one daggerboard and case is quicker than making and installing two. And as a bonus, you have full use of the other hull—usually where the galley is.

22 years sailing – still looks like new

My original board has been in use for the last 22 years and still looks like the day it was built, despite hitting the bottom (coming to a dead stop from 5kts on sand). I encountered plenty of stormy weather sailing over the years, operating under high load. Living proof of the excellent outright strength and fatigue strength, of wood, epoxy and e-glass as a system. Simple, inexpensive, readily available materials do the job just fine.

Shave days off windward passages

With its large chord, deep draught and glass-smooth white surface, this board cuts through the water like a knife.

Raising and lowering the board when running downwind – makes no measurable difference to speed.


TE30 – a smaller version to suit 30ft catamarans

A smaller version of the TE40 board is now available for purchase. If you are keen to get started, planning and building your board now, you can. Click the buttons above or below to learn more.

Build at home

with simple materials

  • Plywood
  • E-glass
  • Epoxy
  • Paint

There is nothing low-tech about building in plywood, in fact, the opposite is true. Wood/glass/epoxy are the perfect materials for this job. Flexing continuously for years requires high fatigue strength— exactly where wood and epoxy excel.

Engineered for your boat

Buy plans – and make your own board. The price of the plans includes engineering, with uni-glass layup of board and case installation, tailored specifically for your hull.

Every boat is unique with different size hulls, rig and weight. Plans for each board and case are adjusted individually, to suit your boat.

Get Started

Transform your cat