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El 25 de julio de 2020, al estar al Sur verdadero del faro de Punta Paloma y al Sudoeste (SW) verdadero del faro de la Isla de Tarifa, damos rumbo para pasar a 3 millas del faro de Punta Cires. Navegamos a 6 nudos, con viento del NW que nos abate 15º. Declinación magnética de la carta = 5,5º E 2015 (6' W). Desvío de aguja = +6º (más). Calcular el rumbo de agujaOn 25 July 2020 when due South true of Punta Paloma lighthouse and SW true of Isla de Tarifa lighthouse, you head to pass 3 miles off Punta Cires at 6 knots with a NW wind (15º leeway), chart dm 5.5º E 2015 (6' W) and dev +6º. Find Ra:
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Correct answer: a) 050º
Why it is correct
The intersection of the meridian of Punta Paloma (180º from Paloma) with SW from Tarifa (225º from Tarifa) is 35º 55.3′ N, 005º 43.2′ W. From there the tangent to pass 3 miles north of Punta Cires is Rs = 076º. With a NW wind on the port side (+15º starboard leeway), Rv = 076º − 15º = 061º. In 2020 dm = +5.5º − 0.5º = +5º; with deviation +6º, Ct = +11º and Ra = 061º − 11º = 050º.
Why the others are not
- b) Does not subtract the 15º starboard leeway or fails to subtract total compass error Ct = +11º.
- c) Does not subtract the 15º starboard leeway or fails to subtract total compass error Ct = +11º.
- d) Does not subtract the 15º starboard leeway or fails to subtract total compass error Ct = +11º.
How to work it out in the exam
- Plot the start (S of Paloma, SW of Tarifa) and draw the tangent 3′ off Punta Cires: Rs = 076º.
- Subtract leeway (Rv = 076º − 15º = 061º) and subtract Ct = +5º + 6º = +11º: Ra = 050º.
Where this question comes from
- Junta de Andalucía · 2020 · Convocatoria de e · PY Módulo de navegación · question 13 Official paper · Official answer key
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Pending instructor review. Machine translation, not reviewed.