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Sailboat
One prolonged blast followed two short blasts, every two minutes, not to exceed two minutes. Rule 35-Sound Signals in restricted visibility.
One prolonged and two short blasts is 'D' in Morse signals. It is a signal to be used in restricted visibility by a vessel not under command[NUC], a vessel restricted in her ability to manoeuvre[RAM], a vessel constrained by her draught, a sailing vessel, a vessel engaged in fishing and a vessel engaged in towing or pushing another vessel.
When visibility is very limited, such as in heavy fog, boaters must give an audible signal to others in the area. For a sailboat the signal is one prolonged blast plus two short blasts every two minutes.
Rules of the Road, Rule 35, Sound Signals in Restricted Visibility. (B) A power driven vessel underway but stopped and making no way through the water shall sound at intervals of not more than two minutes, two prolonged blasts in succession with an interval of about two seconds between them.
One prolonged blast plus two short blasts every two minutes. Explanation: Sound signals let other boaters know where you are located during periods of restricted visibility, such as extreme fog. If you hear the fog signal of a vessel you cannot see, slow to a minimum speed until you are sure there is not a risk of collision. One prolonged blast plus two short blasts at intervals of not more than two minutes is the signal used by sailing vessels.
One prolonged blast plus two short blasts every two minutes. Explanation: Sound signals let other boaters know where you are located during periods of restricted visibility, such as extreme fog. If you hear the fog signal of a vessel you cannot see, slow to a minimum speed until you are sure there is not a risk of collision. One prolonged blast plus two short blasts at intervals of not more than two minutes is the signal used by sailing vessels.
One prolonged blast plus two short blasts every two minutes. Explanation: Sound signals let other boaters know where you are located during periods of restricted visibility, such as extreme fog. If you hear the fog signal of a vessel you cannot see, slow to a minimum speed until you are sure there is not a risk of collision. One prolonged blast plus two short blasts at intervals of not more than two minutes is the signal used by sailing vessels.
One prolonged blast plus two short blasts every two minutes. Explanation: Sound signals let other boaters know where you are located during periods of restricted visibility, such as extreme fog. If you hear the fog signal of a vessel you cannot see, slow to a minimum speed until you are sure there is not a risk of collision. One prolonged blast plus two short blasts at intervals of not more than two minutes is the signal used by sailing vessels.
One prolonged blast plus two short blasts every two minutes. Explanation: Sound signals let other boaters know where you are located during periods of restricted visibility, such as extreme fog. If you hear the fog signal of a vessel you cannot see, slow to a minimum speed until you are sure there is not a risk of collision. One prolonged blast plus two short blasts at intervals of not more than two minutes is the signal used by sailing vessels.
Rules of the RoadRule 35Sound Signals in Restricted Visibility(C) A vessel not under command, a vessel restricted in her ability to maneuver, a vessel constrained by her draft, a sailing vessel, a vessel engaged in fishing, and a vessel engaged in towing or pushing another vessel shall..........sound at intervals of not more than two minutes, three blast in succession, namely one prolonged followed by two short blasts.
Rule 35 part c of the International Regulations for Preventing Collisions at Sea (72 COLREGS) states that when in restricted visibility (i.e. fog) a sailing vessel is required to sound one prolonged blast followed by two short blasts on the vessel's whistle, at intervals of not more than two minutes. Please refer to the link below.