{"id":1566,"date":"2024-08-06T21:55:14","date_gmt":"2024-08-06T21:55:14","guid":{"rendered":"https:\/\/artchery.org\/wordpress\/?page_id=1566"},"modified":"2024-09-28T19:04:10","modified_gmt":"2024-09-28T19:04:10","slug":"ya-selection-in-kyudo","status":"publish","type":"page","link":"https:\/\/artchery.org\/wordpress\/index.php\/ya-selection-in-kyudo\/","title":{"rendered":"Ya Selection in Kyudo"},"content":{"rendered":"\t\t<div data-elementor-type=\"wp-page\" data-elementor-id=\"1566\" class=\"elementor elementor-1566\">\n\t\t\t\t\t\t\t<div class=\"elementor-element elementor-element-ec73c9d e-flex e-con-boxed e-con e-parent\" data-id=\"ec73c9d\" data-element_type=\"container\" data-settings=\"{&quot;background_background&quot;:&quot;classic&quot;,&quot;content_width&quot;:&quot;boxed&quot;}\" data-core-v316-plus=\"true\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-2f14cdd elementor-widget elementor-widget-heading\" data-id=\"2f14cdd\" data-element_type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t<style>\/*! elementor - v3.18.0 - 08-12-2023 *\/\n.elementor-heading-title{padding:0;margin:0;line-height:1}.elementor-widget-heading .elementor-heading-title[class*=elementor-size-]>a{color:inherit;font-size:inherit;line-height:inherit}.elementor-widget-heading .elementor-heading-title.elementor-size-small{font-size:15px}.elementor-widget-heading .elementor-heading-title.elementor-size-medium{font-size:19px}.elementor-widget-heading .elementor-heading-title.elementor-size-large{font-size:29px}.elementor-widget-heading .elementor-heading-title.elementor-size-xl{font-size:39px}.elementor-widget-heading .elementor-heading-title.elementor-size-xxl{font-size:59px}<\/style><h2 class=\"elementor-heading-title elementor-size-default\">Ya Selection in Kyudo<\/h2>\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-3544b88 e-flex e-con-boxed e-con e-parent\" data-id=\"3544b88\" data-element_type=\"container\" data-settings=\"{&quot;content_width&quot;:&quot;boxed&quot;}\" data-core-v316-plus=\"true\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-0d943a4 elementor-widget elementor-widget-text-editor\" data-id=\"0d943a4\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t<style>\/*! elementor - v3.18.0 - 08-12-2023 *\/\n.elementor-widget-text-editor.elementor-drop-cap-view-stacked .elementor-drop-cap{background-color:#69727d;color:#fff}.elementor-widget-text-editor.elementor-drop-cap-view-framed .elementor-drop-cap{color:#69727d;border:3px solid;background-color:transparent}.elementor-widget-text-editor:not(.elementor-drop-cap-view-default) .elementor-drop-cap{margin-top:8px}.elementor-widget-text-editor:not(.elementor-drop-cap-view-default) .elementor-drop-cap-letter{width:1em;height:1em}.elementor-widget-text-editor .elementor-drop-cap{float:left;text-align:center;line-height:1;font-size:50px}.elementor-widget-text-editor .elementor-drop-cap-letter{display:inline-block}<\/style>\t\t\t\t<p>\u00a0<\/p><p><strong>In Western archery, the choice of appropriate arrows is informed by selection charts.\u00a0 These are two dimensional arrays in which each row represents a range of bow strengths and the columns, arrow lengths.\u00a0 For instance, the first row of the Easton selection chart represents bow strengths 21-27 lbs (9.5-12.2 kg) in the first row, 27-32 lbs (12.2-14.5 kg) in the second, and so on.\u00a0 The columns correspond to arrow lengths, starting with 23&#8243; (0.584 m) for the first column, 24&#8243; (0.610 m) for the second column, up to 32&#8243; (0.813 m) for the last column.\u00a0 Each combination of bow strength range and arrow length is assigned its appropriate group of arrows. There is a list of arrow groups: arrows in a given group are close to each other in stiffness.\u00a0 <br \/><\/strong><\/p><p><strong>The arrow lengths covered by the Easton chart, 58.4 to 81.3 cm, are too short for Kyudoka, who require lengths between 80 and 110 cm.\u00a0 Japanese dealers such as Sambu Kyuguten provide rough guidelines for arrow selection based on yumi strength alone with no mention of ya length.\u00a0 What is the physically meaningful extrapolation of\u00a0 the Easton selection chart to the range of ya lengths for Kyudo?<\/strong><\/p>\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-1cbeb79b e-flex e-con-boxed e-con e-parent\" data-id=\"1cbeb79b\" data-element_type=\"container\" data-settings=\"{&quot;content_width&quot;:&quot;boxed&quot;}\" data-core-v316-plus=\"true\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-31378bf1 elementor-widget elementor-widget-text-editor\" data-id=\"31378bf1\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<h4>Why stiffness of ya matters<\/h4>\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-e70c6fa e-flex e-con-boxed e-con e-parent\" data-id=\"e70c6fa\" data-element_type=\"container\" data-settings=\"{&quot;content_width&quot;:&quot;boxed&quot;}\" data-core-v316-plus=\"true\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-51c4d13 elementor-widget elementor-widget-text-editor\" data-id=\"51c4d13\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<p>On page 71 of the Kyohan it says:\u00a0 &#8220;In the full draw (Kai) the arrow must be directed along a line exactly to the center of the target.&#8221;\u00a0 Due to the downward arc of the ya trajectory induced by gravity, this should be amended to say:\u00a0 &#8220;The ya at Kai should lie in a vertical plane which bisects the target.&#8221;\u00a0 The implicit assumption is that the arc of the ya traced after Hanare remains in this plane.\u00a0 A simple shooting test shows that this is not necessarily so.\u00a0<\/p><p>A first preparatory step is to determine a &#8220;sight picture&#8221; consistent with correct ya alignment.\u00a0 For the &#8220;half moon&#8221; sight picture illustrated on page 71 of the Kyohan, the right eye sees half of the mato projecting beyond the left edge of the rattan above the grip. The ya is not part of the sight picture.\u00a0 For our shooting\u00a0 test, we borrow a &#8220;point on&#8221; sight picture from western Bare Bow archery.\u00a0 The point of the ya appears directly below the center dot of the target, and the sight picture includes some length of the ya behind the point, so alignment of the ya can be sensed directly.\u00a0 To test this process of alignment, a laser pointer is attached to the underside of a long ya, as depicted in Fig. 1.\u00a0 Perform the Hassetsu up to and including Kai.\u00a0 At Kai, the front section of the ya with the laser pointer is in front of the yumi grip.\u00a0 After aligning the ya, search for the laser dot on the plane of the target at a range of about 10 m.\u00a0\u00a0 The laser dot typically appears above the target&#8217;s center at twelve o&#8217;clock, indicating that the ya is in the correct vertical plane.<\/p>\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-3ea1f78 e-flex e-con-boxed e-con e-parent\" data-id=\"3ea1f78\" data-element_type=\"container\" data-settings=\"{&quot;content_width&quot;:&quot;boxed&quot;}\" data-core-v316-plus=\"true\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-01b8fcb elementor-widget elementor-widget-image\" data-id=\"01b8fcb\" data-element_type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t<style>\/*! elementor - v3.18.0 - 08-12-2023 *\/\n.elementor-widget-image{text-align:center}.elementor-widget-image a{display:inline-block}.elementor-widget-image a img[src$=\".svg\"]{width:48px}.elementor-widget-image img{vertical-align:middle;display:inline-block}<\/style>\t\t\t\t\t\t\t\t\t<figure class=\"wp-caption\">\n\t\t\t\t\t\t\t\t\t\t<img fetchpriority=\"high\" decoding=\"async\" width=\"462\" height=\"149\" src=\"https:\/\/artchery.org\/wordpress\/wp-content\/uploads\/2024\/08\/laser_pointer.jpg\" class=\"attachment-large size-large wp-image-1572\" alt=\"\" srcset=\"https:\/\/artchery.org\/wordpress\/wp-content\/uploads\/2024\/08\/laser_pointer.jpg 462w, https:\/\/artchery.org\/wordpress\/wp-content\/uploads\/2024\/08\/laser_pointer-300x97.jpg 300w\" sizes=\"(max-width: 462px) 100vw, 462px\" \/>\t\t\t\t\t\t\t\t\t\t\t<figcaption class=\"widget-image-caption wp-caption-text\">Fig. 1:  Laser pointer attached to a long ya.<\/figcaption>\n\t\t\t\t\t\t\t\t\t\t<\/figure>\n\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-9c88367 elementor-widget elementor-widget-text-editor\" data-id=\"9c88367\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-72660b2 e-flex e-con-boxed e-con e-parent\" data-id=\"72660b2\" data-element_type=\"container\" data-settings=\"{&quot;content_width&quot;:&quot;boxed&quot;}\" data-core-v316-plus=\"true\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-b4f83fa elementor-widget elementor-widget-text-editor\" data-id=\"b4f83fa\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<p>The shooting test begins with a 14.5 kg Rokusun yumi.\u00a0 There are four pairs of test ya, all 102 cm long.\u00a0 Pairs one and two are 1913 and 2015 aluminum shafts and the remaining pairs three and four are bamboo wrapped carbon.\u00a0 The table below lists their stiffnesses relative to the 2015 aluminum ya.\u00a0 <\/p>\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-f28106c e-flex e-con-boxed e-con e-parent\" data-id=\"f28106c\" data-element_type=\"container\" data-settings=\"{&quot;content_width&quot;:&quot;boxed&quot;}\" data-core-v316-plus=\"true\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-4d0aaa4 elementor-widget elementor-widget-image\" data-id=\"4d0aaa4\" data-element_type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<img decoding=\"async\" width=\"300\" height=\"271\" src=\"https:\/\/artchery.org\/wordpress\/wp-content\/uploads\/2024\/08\/stiffness-300x271.png\" class=\"attachment-medium size-medium wp-image-1580\" alt=\"\" srcset=\"https:\/\/artchery.org\/wordpress\/wp-content\/uploads\/2024\/08\/stiffness-300x271.png 300w, https:\/\/artchery.org\/wordpress\/wp-content\/uploads\/2024\/08\/stiffness.png 370w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/>\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-22df770 e-flex e-con-boxed e-con e-parent\" data-id=\"22df770\" data-element_type=\"container\" data-settings=\"{&quot;content_width&quot;:&quot;boxed&quot;}\" data-core-v316-plus=\"true\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-9034aa8 elementor-widget elementor-widget-text-editor\" data-id=\"9034aa8\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<p>Each pair is shot three times at a range of 21 m, employing the &#8220;point on&#8221; sight picture described before.\u00a0\u00a0 Figure 2 is a photograph of a pair of 1913&#8217;s in the target.\u00a0 The mato is 27 cm in diameter, so its angular diameter seen at 21 m is the same as for the standard 36 cm mato as seen at 28 m.<\/p>\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-3d12942 e-flex e-con-boxed e-con e-parent\" data-id=\"3d12942\" data-element_type=\"container\" data-settings=\"{&quot;content_width&quot;:&quot;boxed&quot;}\" data-core-v316-plus=\"true\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-8d82f18 elementor-widget elementor-widget-image\" data-id=\"8d82f18\" data-element_type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t\t\t\t<figure class=\"wp-caption\">\n\t\t\t\t\t\t\t\t\t\t<img decoding=\"async\" width=\"175\" height=\"150\" src=\"https:\/\/artchery.org\/wordpress\/wp-content\/uploads\/2024\/08\/test_1.jpg\" class=\"attachment-large size-large wp-image-1581\" alt=\"\" \/>\t\t\t\t\t\t\t\t\t\t\t<figcaption class=\"widget-image-caption wp-caption-text\">Fig. 2:  A pair of 1913's in the target.<\/figcaption>\n\t\t\t\t\t\t\t\t\t\t<\/figure>\n\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-482dc90 e-flex e-con-boxed e-con e-parent\" data-id=\"482dc90\" data-element_type=\"container\" data-settings=\"{&quot;content_width&quot;:&quot;boxed&quot;}\" data-core-v316-plus=\"true\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-9228ff0 elementor-widget elementor-widget-text-editor\" data-id=\"9228ff0\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<p>We are not concerned with the elevations of the shots, rather with their left\/right drift from the vertical line bisecting the target.\u00a0 The photograph is imported into a graphics package.\u00a0 The center dot of the mato is painted over by a black disk of the same size.\u00a0 Impact points are marked by smaller disks.\u00a0 This done, the photograph is deleted from the figure file.\u00a0 The photograph of the next ya pair is imported and the process repeats.\u00a0\u00a0 In Fig. 3, the blue dots represent impact points of 1913&#8217;s, green dots, 2015&#8217;s,\u00a0 yellow dots,\u00a0 the softer bamboo wrapped carbon, and red dots, the stiffer bamboo wrapped carbon.<\/p>\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-cfe1b15 e-flex e-con-boxed e-con e-parent\" data-id=\"cfe1b15\" data-element_type=\"container\" data-settings=\"{&quot;content_width&quot;:&quot;boxed&quot;}\" data-core-v316-plus=\"true\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-c9a256d e-flex e-con-boxed e-con e-parent\" data-id=\"c9a256d\" data-element_type=\"container\" data-settings=\"{&quot;content_width&quot;:&quot;boxed&quot;}\" data-core-v316-plus=\"true\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-ebc200a elementor-widget elementor-widget-image\" data-id=\"ebc200a\" data-element_type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t\t\t\t<figure class=\"wp-caption\">\n\t\t\t\t\t\t\t\t\t\t<img loading=\"lazy\" decoding=\"async\" width=\"274\" height=\"300\" src=\"https:\/\/artchery.org\/wordpress\/wp-content\/uploads\/2024\/08\/select_test-274x300.jpg\" class=\"attachment-medium size-medium wp-image-1590\" alt=\"\" srcset=\"https:\/\/artchery.org\/wordpress\/wp-content\/uploads\/2024\/08\/select_test-274x300.jpg 274w, https:\/\/artchery.org\/wordpress\/wp-content\/uploads\/2024\/08\/select_test.jpg 489w\" sizes=\"(max-width: 274px) 100vw, 274px\" \/>\t\t\t\t\t\t\t\t\t\t\t<figcaption class=\"widget-image-caption wp-caption-text\">Fig. 3:  Groupings of ya shot from 14.5 kg yumi.  Blue dots-1913, green dots-2015, yellow dots-softer bamboo wrapped carbon, red dots-stiffer bamboo wrapped carbon.<\/figcaption>\n\t\t\t\t\t\t\t\t\t\t<\/figure>\n\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-453de8a e-flex e-con-boxed e-con e-parent\" data-id=\"453de8a\" data-element_type=\"container\" data-settings=\"{&quot;content_width&quot;:&quot;boxed&quot;}\" data-core-v316-plus=\"true\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-c074b3a elementor-widget elementor-widget-text-editor\" data-id=\"c074b3a\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<p>The softest ya, 1913, has the largest leftward drift.\u00a0 In Kyudo parlance, 1913&#8217;s &#8220;land behind the mato.&#8221;\u00a0 So do 2015&#8217;s, but with less leftward drift.\u00a0 The softer bamboo wrapped carbon which is 22% stiffer than 2015 has very little drift.\u00a0 The stiffer bamboo wrapped carbon is 229% stiffer than 2015, but it too has very little drift.\u00a0 Apparently, there is a &#8220;threshold&#8221; stiffness that must be exceeded for the ya to stay in the correct vertical plane after it is launched.<\/p><p>Intuitively, the threshold stiffness should be larger for stronger yumi.\u00a0 Figure 4 shows the impact points of the bamboo wrapped carbon ya shot out of a 19 kg Rokusun.\u00a0 The softer grade of bamboo wrapped carbon lands behind the mato, and the stiffer grade still has very little left\/right drift.<\/p>\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-fbc8d04 e-flex e-con-boxed e-con e-parent\" data-id=\"fbc8d04\" data-element_type=\"container\" data-settings=\"{&quot;content_width&quot;:&quot;boxed&quot;}\" data-core-v316-plus=\"true\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-2183023 elementor-widget elementor-widget-image\" data-id=\"2183023\" data-element_type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t\t\t\t<figure class=\"wp-caption\">\n\t\t\t\t\t\t\t\t\t\t<img loading=\"lazy\" decoding=\"async\" width=\"224\" height=\"300\" src=\"https:\/\/artchery.org\/wordpress\/wp-content\/uploads\/2024\/08\/20kg-224x300.jpg\" class=\"attachment-medium size-medium wp-image-1597\" alt=\"\" srcset=\"https:\/\/artchery.org\/wordpress\/wp-content\/uploads\/2024\/08\/20kg-224x300.jpg 224w, https:\/\/artchery.org\/wordpress\/wp-content\/uploads\/2024\/08\/20kg.jpg 431w\" sizes=\"(max-width: 224px) 100vw, 224px\" \/>\t\t\t\t\t\t\t\t\t\t\t<figcaption class=\"widget-image-caption wp-caption-text\">Fig. 4:  Groupings of bamboo wrapped carbon ya shot from 19 kg yumi.  Yellow dots-softer, red dots-stiffer.<\/figcaption>\n\t\t\t\t\t\t\t\t\t\t<\/figure>\n\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-5f7d659 e-flex e-con-boxed e-con e-parent\" data-id=\"5f7d659\" data-element_type=\"container\" data-settings=\"{&quot;content_width&quot;:&quot;boxed&quot;}\" data-core-v316-plus=\"true\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-ed57335 elementor-widget elementor-widget-heading\" data-id=\"ed57335\" data-element_type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t<h4 class=\"elementor-heading-title elementor-size-default\">Stiffness selection formula<\/h4>\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-f4e56eb elementor-widget elementor-widget-text-editor\" data-id=\"f4e56eb\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<p>There is an implicit assumption behind the selection charts mentioned at the beginning of this page:\u00a0 The &#8220;appropriate&#8221; arrow stiffness \u00b5 depends only on the arrow length l and bow strength f.\u00a0\u00a0 If so, we have the simple &#8220;stiffness selection formula&#8221;<\/p>\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-524b950 elementor-widget elementor-widget-text-editor\" data-id=\"524b950\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\u00b5 = c f l<sup>2<\/sup>.\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-9b2cb46 elementor-widget elementor-widget-text-editor\" data-id=\"9b2cb46\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<p>Here, c is a multiplicative constant, the same for all entries in the selection chart.\u00a0 The stiffness selection\u00a0 formula follows from the operational definition of stiffness.\u00a0 In Fig. 5, a uniform rod (aka-the arrow shaft) is clamped horizontally at one end o and a vertical load is applied to the free end p.\u00a0 The rod bends under the load and it has some curvature \u03ba at the clamped end. Recall that the curvature is the inverse radius of the circle which best approximates the bend of the rod near o. The load at p exerts a torque \u03c4 on the clamped end, which is the length l of the line segment op times the component f&#8217; of the load perpendicular to op. <\/p>\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-df071d8 elementor-widget elementor-widget-image\" data-id=\"df071d8\" data-element_type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t\t\t\t<figure class=\"wp-caption\">\n\t\t\t\t\t\t\t\t\t\t<img loading=\"lazy\" decoding=\"async\" width=\"300\" height=\"262\" src=\"https:\/\/artchery.org\/wordpress\/wp-content\/uploads\/2024\/08\/torque_ID-300x262.png\" class=\"attachment-medium size-medium wp-image-1647\" alt=\"\" srcset=\"https:\/\/artchery.org\/wordpress\/wp-content\/uploads\/2024\/08\/torque_ID-300x262.png 300w, https:\/\/artchery.org\/wordpress\/wp-content\/uploads\/2024\/08\/torque_ID-768x671.png 768w, https:\/\/artchery.org\/wordpress\/wp-content\/uploads\/2024\/08\/torque_ID.png 938w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/>\t\t\t\t\t\t\t\t\t\t\t<figcaption class=\"widget-image-caption wp-caption-text\">Fig. 5:  The torque identity.<\/figcaption>\n\t\t\t\t\t\t\t\t\t\t<\/figure>\n\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-508e5d8 elementor-widget elementor-widget-text-editor\" data-id=\"508e5d8\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<p>Expressed mathematically, the formula for torque is<\/p>\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-176f93e elementor-widget elementor-widget-text-editor\" data-id=\"176f93e\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t&#964; = l f&#8217;.\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-beba160 elementor-widget elementor-widget-text-editor\" data-id=\"beba160\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\tIt is observed that the curvature &#954; is directly proportional to the torque which induces it.\u00a0 There is a proportionality constant &#181; so that\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-2dac01f elementor-widget elementor-widget-text-editor\" data-id=\"2dac01f\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\u03c4 = \u00b5 &#954;.\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-70581a7 elementor-widget elementor-widget-text-editor\" data-id=\"70581a7\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<p>The constant of proportionality \u00b5 is the quantifier of stiffness. The proportionality between torque and curvature is called the torque identity. We see it in other contexts, such as the relationship between braced and Urazori shapes of the yumi in the page <a href=\"https:\/\/artchery.org\/wordpress\/index.php\/shape-of-the-yumi\/\">&#8220;Designing the Urazori Shape of the Yumi.&#8221;<\/a><\/p>\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-be50c3a e-flex e-con-boxed e-con e-parent\" data-id=\"be50c3a\" data-element_type=\"container\" data-settings=\"{&quot;content_width&quot;:&quot;boxed&quot;}\" data-core-v316-plus=\"true\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-f326e9a elementor-widget elementor-widget-text-editor\" data-id=\"f326e9a\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<p>Since torque is force times length and curvature is an inverse length, we see that the stiffness \u00b5 is a force times length squared. In conventional language, we say that &#8220;the units of stiffness are force times length squared.&#8221;<\/p><p>The proportionality of recommended stiffness to bow strength times arrow length squared is consistent with balance of physical units, but why this relation and no other?\u00a0 If we change the unit of length by a scaling factor L and the unit of force by scaling factor F, the unit of stiffness changes by the factor F L<sup>2<\/sup>. Now take a proposed dependence of \u00b5 upon l and f. If we replace l by Ll, and f by Ff, the formula should produce the correct stiffness in units of F L<sup>2<\/sup>. The consistency of physical relationships under scaling of state variables is called scale covariance. In particular, scale covariance implies the proportionality of stiffness to bow strength times arrow length squared.<\/p><p>A not implausible refinement of the selection formula replaces the length of the arrow by the actual depth (Yazuka) y of the draw.\u00a0 Given the length l of the arrow and the brace height h of the bow, we have roughly<\/p>\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-731a824 elementor-widget elementor-widget-text-editor\" data-id=\"731a824\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<p>y = l &#8211; h,<\/p>\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-32ad43f elementor-widget elementor-widget-text-editor\" data-id=\"32ad43f\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<p>and the modified selection formula is<\/p>\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-d994ef9 elementor-widget elementor-widget-text-editor\" data-id=\"d994ef9\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t&#181; = c f y<sup>2<\/sup> .\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-a814f85 elementor-widget elementor-widget-text-editor\" data-id=\"a814f85\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<p>This formula gives good approximations to the actual recommended stiffness in the Easton selection chart with the choices of c and h,<\/p>\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-95dd085 elementor-widget elementor-widget-text-editor\" data-id=\"95dd085\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<p>c = 0.1674,\u00a0 h = 17.2 cm = 6.73&#8243;.<\/p>\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-f83b86c elementor-widget elementor-widget-text-editor\" data-id=\"f83b86c\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<p>These values of c and h are obtained from a least squares fit of the selection formula to the actual entries in the Easton chart.\u00a0 The brace height\u00a0 h = 6.73&#8243; is reassuring since brace heights of western bows range between 6&#8243; and 9&#8243;.\u00a0 <\/p>\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-49fe6b6 e-flex e-con-boxed e-con e-parent\" data-id=\"49fe6b6\" data-element_type=\"container\" data-settings=\"{&quot;content_width&quot;:&quot;boxed&quot;}\" data-core-v316-plus=\"true\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-b276e12 elementor-widget elementor-widget-text-editor\" data-id=\"b276e12\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<p>We can visualize the stiffness selection formula by plotting contours of constant stiffness in the plane whose axes are arrow length on the horizontal and bow strength on the vertical. In Fig. 6, the green rectangle labeled &#8220;E&#8221; represents the ranges of arrow length and bow strength covered by the Easton chart.\u00a0\u00a0 The longest arrow length covered by the Easton chart, close to 82 cm, is scarcely longer than the shortest ya length, near 80 cm.\u00a0\u00a0 The yellow rectangle labeled &#8220;K&#8221; represents the ranges of ya length and yumi strength that includes most Kyudoka.\u00a0 The four\u00a0 curves represent stiffness contours for four common aluminum ya, 1913, 2014, 2015, 2117.\u00a0 For instance, the contour labeled &#8220;1913&#8221; represents all the combinations of ya length and yumi strength which are appropriate for 1913 aluminum ya.\u00a0 The four grades of aluminum shafts are common in Western archery as well as Kyudo, and indeed the stiffness contours cover the &#8220;middle&#8221; of the Easton rectangle.\u00a0 The same contours cover only the upper left corner of the Kyudo rectangle, corresponding to short ya shot from light yumi.\u00a0 In summary, one might say that the common aluminum ya cover the needs of Western archers better than the needs of Kyudoka.<\/p>\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-733ecbd e-flex e-con-boxed e-con e-parent\" data-id=\"733ecbd\" data-element_type=\"container\" data-settings=\"{&quot;content_width&quot;:&quot;boxed&quot;}\" data-core-v316-plus=\"true\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-a83ed5b elementor-widget elementor-widget-image\" data-id=\"a83ed5b\" data-element_type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t\t\t\t<figure class=\"wp-caption\">\n\t\t\t\t\t\t\t\t\t\t<img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"716\" src=\"https:\/\/artchery.org\/wordpress\/wp-content\/uploads\/2024\/08\/Easton_chart-1024x716.jpg\" class=\"attachment-large size-large wp-image-1674\" alt=\"\" srcset=\"https:\/\/artchery.org\/wordpress\/wp-content\/uploads\/2024\/08\/Easton_chart-1024x716.jpg 1024w, https:\/\/artchery.org\/wordpress\/wp-content\/uploads\/2024\/08\/Easton_chart-300x210.jpg 300w, https:\/\/artchery.org\/wordpress\/wp-content\/uploads\/2024\/08\/Easton_chart-768x537.jpg 768w, https:\/\/artchery.org\/wordpress\/wp-content\/uploads\/2024\/08\/Easton_chart.jpg 1335w\" sizes=\"(max-width: 1024px) 100vw, 1024px\" \/>\t\t\t\t\t\t\t\t\t\t\t<figcaption class=\"widget-image-caption wp-caption-text\">Fig. 6: Stiffness contours of aluminum ya used in Kyudo.<\/figcaption>\n\t\t\t\t\t\t\t\t\t\t<\/figure>\n\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-37f281f elementor-widget elementor-widget-text-editor\" data-id=\"37f281f\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<p>The red and blue dots represent the ya length-yumi strength combinations of sensei Aaron and Reiko Blackwell, respectively.\u00a0 The blue dot lies on the 2015 contour, suggesting that 2015 is a correct ya for her.\u00a0 In fact, her aluminum ya are all 1913, the conventional option for short ya length and light yumi strength.\u00a0\u00a0 The red dot is far below all four contours, suggesting that none of the common aluminum ya are really appropriate for the long ya length and strong yumi strength that Aaron sensei uses.<\/p>\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-7595517 e-flex e-con-boxed e-con e-parent\" data-id=\"7595517\" data-element_type=\"container\" data-settings=\"{&quot;content_width&quot;:&quot;boxed&quot;}\" data-core-v316-plus=\"true\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-5d917ad e-flex e-con-boxed e-con e-parent\" data-id=\"5d917ad\" data-element_type=\"container\" data-settings=\"{&quot;content_width&quot;:&quot;boxed&quot;}\" data-core-v316-plus=\"true\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-0f84025 elementor-widget elementor-widget-heading\" data-id=\"0f84025\" data-element_type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t<h4 class=\"elementor-heading-title elementor-size-default\">Preferences for ya inherited from tradition<\/h4>\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-d3cc040 elementor-widget elementor-widget-text-editor\" data-id=\"d3cc040\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-2851741 elementor-widget elementor-widget-text-editor\" data-id=\"2851741\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<p>What are characteristics of high-end take-ya informed by long standing Kyudo tradition?\u00a0\u00a0 Four sets of take-ya are examined:\u00a0 Longer and stiffer Shinsa ya of (1) Aaron Blackwell sensei, (2) Ed Symes sensei,\u00a0 (3) Bill Holtz sensei, and shorter, softer ya of (4) Reiko Blackwell\u00a0 sensei. \u00a0 The table below lists their measured physical specifications. The weights of take-ya sets 1-3 are very close 2015&#8217;s of the same lengths, and the take-ya of set 4 are only slightly heavier than Reiko sensei&#8217;s 1913&#8217;s.\u00a0 The stiffnesses of sets 1 and 2 are very close to 2015, and set 3 has a stiffness very close to 2117.\u00a0 Set 4 is slightly softer than 1913.\u00a0\u00a0 Mechanically,\u00a0 the standard aluminum ya commonly used in Kyudo are close to take-ya counterparts.\u00a0<\/p>\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-99fd66b elementor-widget elementor-widget-image\" data-id=\"99fd66b\" data-element_type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<img loading=\"lazy\" decoding=\"async\" width=\"768\" height=\"203\" src=\"https:\/\/artchery.org\/wordpress\/wp-content\/uploads\/2024\/09\/Screenshot-2024-09-25-at-2.37.29\u202fPM-768x203.png\" class=\"attachment-medium_large size-medium_large wp-image-2347\" alt=\"\" srcset=\"https:\/\/artchery.org\/wordpress\/wp-content\/uploads\/2024\/09\/Screenshot-2024-09-25-at-2.37.29\u202fPM-768x203.png 768w, https:\/\/artchery.org\/wordpress\/wp-content\/uploads\/2024\/09\/Screenshot-2024-09-25-at-2.37.29\u202fPM-300x79.png 300w, https:\/\/artchery.org\/wordpress\/wp-content\/uploads\/2024\/09\/Screenshot-2024-09-25-at-2.37.29\u202fPM-1024x271.png 1024w, https:\/\/artchery.org\/wordpress\/wp-content\/uploads\/2024\/09\/Screenshot-2024-09-25-at-2.37.29\u202fPM.png 1234w\" sizes=\"(max-width: 768px) 100vw, 768px\" \/>\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-e2542a8 elementor-widget elementor-widget-text-editor\" data-id=\"e2542a8\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<p>Given lengths and stiffnesses of the take-ya, we can compute the appropriate bow strengths according to the stiffness selection formula.\u00a0 In this way we locate points in the plane of arrow length and bow strength corresponding to the take-ya sets 1-4.\u00a0 These are the green dots in Fig. 6.\u00a0\u00a0 We see that the &#8220;appropriate&#8221; bow strengths for the longer take-ya 1-3 are in the 7-10 kg range, much weaker than the yumi that Aaron sensei, Ed sensei and Holtz sensei actually use.\u00a0 The recommended bow strength for take-ya 4, close to 7 kg, is still considerably less than the 12 kg strength of Reiko sensei&#8217;s yumi.<\/p>\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-5f6e409 elementor-widget elementor-widget-heading\" data-id=\"5f6e409\" data-element_type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t<h4 class=\"elementor-heading-title elementor-size-default\">Ya selection that enables \"correct hitting\"<\/h4>\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-78be429 elementor-widget elementor-widget-text-editor\" data-id=\"78be429\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<p>The recommended stiffnesses based on the selection formula with the Easton values of the constants c and h may be higher than what actually works for Kyudoka.\u00a0\u00a0 Here, we readjust the values of c and h.\u00a0\u00a0 The value of h is the standard brace height (Ha) of 15 cm.\u00a0\u00a0 In the shooting test, we found that the bamboo wrapped carbon ya 22% stiffer than 2015 shot from a 14.5 kg yumi in fact flies in the vertical plane for &#8220;correct&#8221; hitting.\u00a0 With the yumi strength (14.5 kg) and ya length (102 cm) given, and h = 15 cm, we can compute the readjusted value of c, c = 0.107, about 2\/3 of the Easton value, h = 0.1674.\u00a0 Figure 7 is the redo of Fig. 6, based upon the readjusted values of c and h.\u00a0<\/p>\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-efb9bef elementor-widget elementor-widget-image\" data-id=\"efb9bef\" data-element_type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t\t\t\t<figure class=\"wp-caption\">\n\t\t\t\t\t\t\t\t\t\t<img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"691\" src=\"https:\/\/artchery.org\/wordpress\/wp-content\/uploads\/2024\/08\/kyudo_chart-1024x691.jpg\" class=\"attachment-large size-large wp-image-1675\" alt=\"\" srcset=\"https:\/\/artchery.org\/wordpress\/wp-content\/uploads\/2024\/08\/kyudo_chart-1024x691.jpg 1024w, https:\/\/artchery.org\/wordpress\/wp-content\/uploads\/2024\/08\/kyudo_chart-300x202.jpg 300w, https:\/\/artchery.org\/wordpress\/wp-content\/uploads\/2024\/08\/kyudo_chart-768x518.jpg 768w, https:\/\/artchery.org\/wordpress\/wp-content\/uploads\/2024\/08\/kyudo_chart.jpg 1385w\" sizes=\"(max-width: 1024px) 100vw, 1024px\" \/>\t\t\t\t\t\t\t\t\t\t\t<figcaption class=\"widget-image-caption wp-caption-text\">Fig. 7:   Redo of Fig. 6, based on readjusted values of c and h.<\/figcaption>\n\t\t\t\t\t\t\t\t\t\t<\/figure>\n\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-7809a84 elementor-widget elementor-widget-text-editor\" data-id=\"7809a84\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<p>The stiffness contours cover a region closer to a diagonal of the Kyudo rectangle &#8220;K.&#8221;\u00a0 Reiko sensei&#8217;s take-ya appear to be a tad soft for her, but close.\u00a0 The sets 1-3 of take-ya are apparently too soft for Aaron sensei.\u00a0 According the the selection formula with the readjusted coefficients, his combination of ya length, yumi strength is accommodated by a ya 2.24 times as stiff as 2015.\u00a0 Recall that the stiffer grade of bamboo wrapped carbon is 2.29 times as stiff as 2015, so this ya should be a good match for Aaron sensei.\u00a0 He seems to think so, as he has told me.<\/p>\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-0c93d6e e-flex e-con-boxed e-con e-parent\" data-id=\"0c93d6e\" data-element_type=\"container\" data-settings=\"{&quot;content_width&quot;:&quot;boxed&quot;}\" data-core-v316-plus=\"true\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-8532f70 elementor-widget elementor-widget-image\" data-id=\"8532f70\" data-element_type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<img loading=\"lazy\" decoding=\"async\" width=\"547\" height=\"32\" src=\"https:\/\/artchery.org\/wordpress\/wp-content\/uploads\/2023\/12\/watakuri.jpg\" class=\"attachment-large size-large wp-image-80\" alt=\"\" srcset=\"https:\/\/artchery.org\/wordpress\/wp-content\/uploads\/2023\/12\/watakuri.jpg 547w, https:\/\/artchery.org\/wordpress\/wp-content\/uploads\/2023\/12\/watakuri-300x18.jpg 300w\" sizes=\"(max-width: 547px) 100vw, 547px\" \/>\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t\t<\/div>\n\t\t","protected":false},"excerpt":{"rendered":"<p>Ya Selection in Kyudo \u00a0 In Western archery, the choice of appropriate arrows is informed by selection charts.\u00a0 These are two dimensional arrays in which each row represents a range of bow strengths and the columns, arrow lengths.\u00a0 For instance, the first row of the Easton selection chart represents bow strengths 21-27 lbs (9.5-12.2 kg) &hellip;<\/p>\n<p class=\"read-more\"> <a class=\"\" href=\"https:\/\/artchery.org\/wordpress\/index.php\/ya-selection-in-kyudo\/\"> <span class=\"screen-reader-text\">Ya Selection in Kyudo<\/span> Read More &raquo;<\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center 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center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""}},"footnotes":""},"class_list":["post-1566","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/artchery.org\/wordpress\/index.php\/wp-json\/wp\/v2\/pages\/1566","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/artchery.org\/wordpress\/index.php\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/artchery.org\/wordpress\/index.php\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/artchery.org\/wordpress\/index.php\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/artchery.org\/wordpress\/index.php\/wp-json\/wp\/v2\/comments?post=1566"}],"version-history":[{"count":226,"href":"https:\/\/artchery.org\/wordpress\/index.php\/wp-json\/wp\/v2\/pages\/1566\/revisions"}],"predecessor-version":[{"id":2668,"href":"https:\/\/artchery.org\/wordpress\/index.php\/wp-json\/wp\/v2\/pages\/1566\/revisions\/2668"}],"wp:attachment":[{"href":"https:\/\/artchery.org\/wordpress\/index.php\/wp-json\/wp\/v2\/media?parent=1566"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}