{"id":1511,"date":"2022-07-18T00:31:31","date_gmt":"2022-07-18T05:31:31","guid":{"rendered":"https:\/\/charles-oneill.com\/blog\/?p=1511"},"modified":"2022-07-24T23:06:58","modified_gmt":"2022-07-25T04:06:58","slug":"cherokee-235-tip-tanks-and-fatigue","status":"publish","type":"post","link":"https:\/\/charles-oneill.com\/blog\/cherokee-235-tip-tanks-and-fatigue\/","title":{"rendered":"Cherokee 235 Tip Tanks and Fatigue"},"content":{"rendered":"\n<p>A previous analysis indicated that the POH fuel-tank recommendations reduced the wing root bending moment. This note attempts to quantify the lifespan impact of the estimated maximum 15% reduction in bending moment. <\/p>\n\n\n\n<p>This video by Airframe Components provides an excellent visual understanding of the PA-28 and PA-32 spar structures. Please review this video before continuing. <\/p>\n\n\n\n<figure class=\"wp-block-embed is-type-video is-provider-youtube wp-block-embed-youtube wp-embed-aspect-16-9 wp-has-aspect-ratio\"><div class=\"wp-block-embed__wrapper\">\n<iframe loading=\"lazy\" title=\"Airframe Components Piper Wing Spars Review\" width=\"625\" height=\"352\" src=\"https:\/\/www.youtube.com\/embed\/tnbvlXEq5kQ?feature=oembed\" frameborder=\"0\" allow=\"accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture\" allowfullscreen><\/iframe>\n<\/div><\/figure>\n\n\n\n<p>The PA-28 aircraft use the NACA 65(2)-415 airfoil (c.f. <a href=\"https:\/\/charles-oneill.com\/blog\/cherokee-tapered-wing-float\/\" data-type=\"post\" data-id=\"1120\">Piper PA-28 Cherokee Wing Comparison: An Aerospace Engineering Perspective<\/a>) with wing spar attach points as illustrated in Figure 1. With the spar at the maximum 15% thickness of a 63 inch chord, the spar height is about 9.5 inches. The moment of inertia is about 18.7 [in4] resulting in a stress of 0.253 [psi] per moment [in-lb]. However, the presence of holes significantly increases the stresses at the bolt holes by about 3x. <\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><a href=\"https:\/\/charles-oneill.com\/blog\/wp-content\/uploads\/2022\/07\/SparDiagram-1.png\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"563\" src=\"https:\/\/charles-oneill.com\/blog\/wp-content\/uploads\/2022\/07\/SparDiagram-1-1024x563.png\" alt=\"\" class=\"wp-image-1531\" srcset=\"https:\/\/charles-oneill.com\/blog\/wp-content\/uploads\/2022\/07\/SparDiagram-1-1024x563.png 1024w, https:\/\/charles-oneill.com\/blog\/wp-content\/uploads\/2022\/07\/SparDiagram-1-300x165.png 300w, https:\/\/charles-oneill.com\/blog\/wp-content\/uploads\/2022\/07\/SparDiagram-1-768x422.png 768w, https:\/\/charles-oneill.com\/blog\/wp-content\/uploads\/2022\/07\/SparDiagram-1-1536x845.png 1536w, https:\/\/charles-oneill.com\/blog\/wp-content\/uploads\/2022\/07\/SparDiagram-1-2048x1126.png 2048w, https:\/\/charles-oneill.com\/blog\/wp-content\/uploads\/2022\/07\/SparDiagram-1-624x343.png 624w\" sizes=\"(max-width: 1024px) 100vw, 1024px\" \/><\/a><figcaption>Figure 1: PA-28 Wing Spar at the Root<\/figcaption><\/figure>\n\n\n\n<p>Aluminum has the unfortunate mechanical property that all loading -regardless of the stress magnitude- contribute to the metallic lifespan.<\/p>\n\n\n\n<p>To be continued.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>A previous analysis indicated that the POH fuel-tank recommendations reduced the wing root bending moment. This note attempts to quantify the lifespan impact of the estimated maximum 15% reduction in bending moment. This video by Airframe Components provides an excellent visual understanding of the PA-28 and PA-32 spar structures. Please review this video before continuing. [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"_links":{"self":[{"href":"https:\/\/charles-oneill.com\/blog\/wp-json\/wp\/v2\/posts\/1511"}],"collection":[{"href":"https:\/\/charles-oneill.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/charles-oneill.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/charles-oneill.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/charles-oneill.com\/blog\/wp-json\/wp\/v2\/comments?post=1511"}],"version-history":[{"count":5,"href":"https:\/\/charles-oneill.com\/blog\/wp-json\/wp\/v2\/posts\/1511\/revisions"}],"predecessor-version":[{"id":1532,"href":"https:\/\/charles-oneill.com\/blog\/wp-json\/wp\/v2\/posts\/1511\/revisions\/1532"}],"wp:attachment":[{"href":"https:\/\/charles-oneill.com\/blog\/wp-json\/wp\/v2\/media?parent=1511"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/charles-oneill.com\/blog\/wp-json\/wp\/v2\/categories?post=1511"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/charles-oneill.com\/blog\/wp-json\/wp\/v2\/tags?post=1511"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}