About Us - SailMentor

What SailMentor is

SailMentor is a small, independent site of free sailing calculators and reference material. It isn’t a club, a chandlery, or a sailing school — just a set of tools built to answer six specific questions sailors ask themselves before or during a passage.

The tools

There are six, and each does one job: the Hull Speed Calculatorestimates a displacement hull’s theoretical top speed from waterline length, the Sail Area Calculator works out mainsail and foretriangle area (and the SA/D ratio) from your rig’s P, E, I, and J dimensions, and the True Wind Calculator converts apparent wind on deck into true wind speed and angle. The Anchor Scope Calculator turns depth, bow-roller height, and tidal rise into a rode length; the Tide Height Calculator estimates water level with the rule of twelfths; and the Sailing Distance Calculator measures a great-circle passage and a rough passage time.

How they work

Nothing here is a black box. The hull speed tool runs the classic 1.34 × √LWL rule; the true wind tool does the vector geometry between boat speed and apparent wind; the tide tool applies the rule of twelfths to your two entered heights. You give the inputs, the page runs the formula in your browser, and you get the number — no account, no data sent anywhere to make the calculation.

Where the numbers come from

The formulas are standard seamanship conventions you’d find in any rigging guide or navigation textbook, not something we invented. That also means they carry the same limits as the paper version: hull speed is a rule of thumb, not a guarantee; tide-by-twelfths assumes a roughly sinusoidal curve; true wind assumes your instruments are reading straight. Real boats and real water are messier than any formula.

The museum

The Ships & Seamanship Museumis a separate section for browsing, not calculating — galleries on sailboats and rigs, the ships of the age of sail, the gear and craft of seamanship, and the winds and races that test a sailor. Every entry, image, and fact there is drawn from Wikipedia and Wikimedia Commons, and it’s built for reading, not citing as an authority.

Straight talk about ads & advice

SailMentor is independent and supported by advertising — that’s how a free site with no logins stays free. We aren’t affiliated with any boat builder, class association, or standards body our pages happen to mention. And none of this is professional navigation, weather, or safety-of-life advice: every result is a general estimate from the numbers you typed in, so verify depths, tides, and conditions against official charts, tide tables, and calibrated instruments before you rely on them out on the water.

About SailMentor