{"id":2561,"date":"2020-06-28T13:29:23","date_gmt":"2020-06-28T20:29:23","guid":{"rendered":"http:\/\/tradewindssailing.com\/wordpress\/?p=2561"},"modified":"2020-06-28T13:29:27","modified_gmt":"2020-06-28T20:29:27","slug":"nautical-terminator-suns-over-the-yardarm-part-2","status":"publish","type":"post","link":"https:\/\/www.tradewindssailing.com\/wordpress\/general\/nautical-terminator-suns-over-the-yardarm-part-2\/","title":{"rendered":"Nautical Terminator \u2013 Sun\u2019s Over the Yardarm (Part 2)"},"content":{"rendered":"\n

                A \u201cyardarm\u201d is not the entire yard, but just its tip outboard of the leeches of the sails. Some authorities commenting on our phrase suggest instead that we use the \u201cupper yards,\u201d while others recommend the \u201cforeyard,\u201d which is the lowest yard on the foremast, for our observations. But both require looking forward, through the sails. Sails are, um….opaque<\/em>–not to put too fine a point on it. Hard to look through. To complicate matters, yards are raised, lowered, and rotated both vertically and horizontally. And where do we make our observations from? It\u2019s quite a muddle.<\/p>\n\n\n\n

                Because it\u2019s the word used in the phrase, I favor \u201cyardarm\u201d as opposed to \u201cyard.\u201d Otherwise, we\u2019re going to have to change our course towards the sun, a non-trivial matter for a square rigger. The lower main yardarm would give an angle of, roughly, 50 degrees above the horizon viewed from the base of the mast. Adjustment of our heading will not be necessary, there being a wide view to either port or starboard as we draw an imaginary horizontal line at the height of the tip of the yard.<\/p>\n\n\n\n

\"\"<\/figure><\/div>\n\n\n\n

                Yard or yardarm, however, few things would be of less use in gauging the altitude of a celestial body than the rigging. Mariners have long sought to isolate their observations of the sun, moon, and stars from the motion of the boat through use of the cross staff, astrolabe, backstaff, octant, and sextant. Yet the masts and yards actually amplify<\/em> the roll and pitch of the ship, just what you don\u2019t want. <\/p>\n\n\n\n

\"\"
Cross staff
<\/figcaption><\/figure><\/div>\n\n\n\n

                And why use the altitude of the sun to tell time? By the period our phrase appeared in 1899, Harrison’s onboard chronometer had been in use for well over 100 years. Before that, time was kept by 30-minute sand glasses. In Columbus\u2019 day noon was established by means of a gnomon, or vertical spike, in the center of the compass card. When the gnomon\u2019s shadow fell on the card\u2019s north, it was noon, and the glass would be set for a new day. Even though the difference between magnetic and true north was not yet understood, this demonstrates that Columbus knew that it wasn\u2019t the sun\u2019s altitude (which the yardarms could supposedly measure) that was at issue, but the time of meridian passage.<\/p>\n\n\n\n

                Shiver me timbers, this is all sounding very shaky. But IF<\/u><\/em> we wanted to tell time using the yardarms, how would we do it? Tune in next time.<\/p>\n","protected":false},"excerpt":{"rendered":"

                A \u201cyardarm\u201d is not the entire yard, but just its tip outboard of the leeches of the sails. Some authorities commenting on our phrase suggest instead that we use the \u201cupper yards,\u201d while others recommend the \u201cforeyard,\u201d which is … Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":13,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[4],"tags":[],"class_list":["post-2561","post","type-post","status-publish","format-standard","hentry","category-general"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_likes_enabled":true,"jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/www.tradewindssailing.com\/wordpress\/wp-json\/wp\/v2\/posts\/2561","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.tradewindssailing.com\/wordpress\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.tradewindssailing.com\/wordpress\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.tradewindssailing.com\/wordpress\/wp-json\/wp\/v2\/users\/13"}],"replies":[{"embeddable":true,"href":"https:\/\/www.tradewindssailing.com\/wordpress\/wp-json\/wp\/v2\/comments?post=2561"}],"version-history":[{"count":10,"href":"https:\/\/www.tradewindssailing.com\/wordpress\/wp-json\/wp\/v2\/posts\/2561\/revisions"}],"predecessor-version":[{"id":2600,"href":"https:\/\/www.tradewindssailing.com\/wordpress\/wp-json\/wp\/v2\/posts\/2561\/revisions\/2600"}],"wp:attachment":[{"href":"https:\/\/www.tradewindssailing.com\/wordpress\/wp-json\/wp\/v2\/media?parent=2561"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.tradewindssailing.com\/wordpress\/wp-json\/wp\/v2\/categories?post=2561"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.tradewindssailing.com\/wordpress\/wp-json\/wp\/v2\/tags?post=2561"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}