Tony Castro


The designer of the SB20 boat

Tony Castro, is not only a renowned world-class yacht designer and a long-time sailor himself, but also “the father” of the SB20 boat. Having previously designed the 1720 boat, Tony faced a challenging task to design a fast, modern One Design Keelboat.

In 2001 the successor of the 1720 boat, the SB20, was conceived with the following priorities:

✔︎ Three person crew

✔︎ Easy to sail by anyone

✔︎ Modern Design

✔︎ Fast and Fun to sail

✔︎ Very Stiff and Stable

✔︎ Strict One-Design rules

✔︎ Simple and affordable

✔︎ High-Tech image

The overall size of 6m coupled with a beam of approx 2.5 m gives a generous small yacht/large dinghy, comfortable to sail with 3 people, economic to buy and maintain, and easily trailable behind a car. The keel was ultimately to be heavy with a 50% ballast ratio minimum. Stability is important because it makes the boat fast and easy to sail. The deck layout is open and clean and as simple as possible. It was important to make the deck design “sexy” and much more elegant than the 1720.

The Sail Area-Displacement ratio is about the same as the 1720. The basic idea of having smaller sails for heavy weather in the 1720 worked very well because it makes the boat sailable in heavy weather without scaring the users. A non-overlapping jib was chosen for its simplicity and it also allows the chainplates to be set wide and support a simple sturdy mast section.

“My philosophy to build SB20 was from the lessons learned with the 1720. The SB20 boat is a success! It provides people with fun and pleasure of sailing a proper one-design Keelboat, with strict rules, where your ability to sail is what matters and at a price you can afford”

As with the 1720, this boat should be unsinkable with the hatch closed. The cockpit and bow sprit shelf is self draining, there are no ropes underdecks, the mast is deck stepped, and there is no way for water to get in when the hatch is closed.


The performance of the boat, especially on a beam reach is electric, but because of the stability it is effortless. The hull prismatic coefficient is quite low and combined with a large sail area it is fast enough in light airs also. The balance of weight, sail area, draught and stability is a happy one and not unlike the 1720 this feeling comes across quite clearly as you will sail her.