Keel | Hull Structure, Shipbuilding & Design

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Let us know if you have suggestions to improve this article (requires login). </div> <div class="type-menu"> <label for="feedback-type" class="label mb-10">Feedback Type</label> <select id="feedback-type" class="form-select mb-30" name="feedbackTypeId" required> <option value="" selected="selected">Select a type (Required)</option> <option value="1">Factual Correction</option> <option value="2">Spelling/Grammar Correction</option> <option value="3">Link Correction</option> <option value="4">Additional Information</option> <option value="5">Other</option> </select> </div> <label for="feedback" class="label mb-10">Your Feedback</label> <textarea id="feedback" class="form-control mb-30" name="feedback" maxlength="3000" rows="7" required></textarea> <button class="btn btn-blue" type="submit">Submit Feedback</button> </form> <div class="success-messaging d-none mt-30"> <div class="title">Thank you for your feedback</div> <p>Our editors will review what you’ve submitted and determine whether to revise the article.</p> </div> </div> </div> <div class="md-websites-modal size-lg d-none"> <div class="md-modal-body"> <div class="h2 font-serif pb-15 border-bottom font-weight-bold"> External Websites </div> <div class="pb-20"> <ul class="list-unstyled mt-20 lh-lg"> <li><a class="external" href="http://adventure.howstuffworks.com/outdoor-activities/water-sports/sailboat5.htm" target="_blank" rel="noopener nofollow">How Stuff Works - Adventure - Sailboat Keel</a></li> </ul> </div> </div> </div> </div> </div> <div class="toc-header-marker"></div> <button class="ai-ask-button btn border-2 js-header-ai-ask-button d-none btn-sm btn-outline-red-400 border-red-400 mr-0 mr-lg-10 ml-5 ml-sm-10 ml-lg-0 p-10"> Ask the Chatbot a Question </button> <div class="md-byline module-spacing "> <div class="font-serif font-12"> <span class="written-by text-gray-700"> Written and fact-checked by </span> <div class="editor-popover popover p-0"> <a class="d-block p-20 gtm-byline font-12 byline-contributor" href="/editor/The-Editors-of-Encyclopaedia-Britannica/4419" > <div class="editor-title font-16 font-weight-bold">The Editors of Encyclopaedia Britannica</div> <div class="editor-description font-12 font-serif mt-5 text-black">Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree. They write new content and verify and edit content received from contributors.</div> </a> <div data-popper-arrow></div> </div> <span class="btn btn-link editor-link p-0 qa-byline-link gtm-byline font-12 byline-contributor text-decoration-underline"> The Editors of Encyclopaedia Britannica</span></div> <div class="last-updated font-12 font-serif"> <a class="byline-edit-history" href="https://www.britannica.com/technology/keel-ship-part/additional-info#history" rel="nofollow">Article History</a> </div></div> </div> <button class="d-flex d-lg-none btn btn-outline-blue border rounded-sm shadow-sm mobile-toc-button gtm-mobile-toc-inline-button d-none d-sm-block js-sections-inline-button module-spacing btn d-lg-none"> <em class="material-icons mr-5 ml-n10 my-n5 md-icon" data-icon="toc"></em> Table of Contents </button> <div class="d-flex d-sm-none flex-row"> <button class="d-flex d-lg-none btn btn-outline-blue border rounded-sm shadow-sm mobile-toc-button gtm-mobile-toc-inline-button js-sections-inline-button module-spacing"> <em class="material-icons mr-5 ml-n10 my-n5 md-icon" data-icon="toc"></em> Table of Contents </button> <button class="ai-ask-button btn border-2 ai-ask-button btn border-2 module-spacing btn-sm js-inline-ai-ask-button btn-outline-red-400 border-red-400 p-10 ml-5"> Ask the Chatbot a Question </button> </div> <div class="js-qf-module qf-module px-40 px-sm-20 py-15 mx-auto module-spacing font-14 bg-gray-50 rounded"> <div class="facts-list mt-10"> <div class=""> <div class="js-fact mb-10 line-clamp clamp-3"> <dl> <dt>Related Topics: </dt> <dd><a href="/technology/skeg" topicid="547351">skeg</a></dd> <dd><a href="/technology/bilge-keel" topicid="65294">bilge keel</a></dd> <dd><a href="/technology/centreboard" topicid="102822">centreboard</a></dd> <dd><a href="/technology/fin-keel" topicid="207103">fin keel</a></dd> <dd><a href="/technology/full-keel" topicid="221837">full keel</a></dd> </dl> <button class="js-more-btn d-none btn btn-unstyled font-12 bg-gray-50" aria-label="Toggle more/less fact data"> <em class="js-content link-blue">(Show more)</em> </button> </div> <div class="text-center"> <a class="btn btn-sm btn-link p-0" href="/facts/keel-ship-part"> See all related content </a> </div> </div> </div> </div><span class="marker before-article"></span><section data-level="1" id="ref1"><span class="marker PREMOD1 mod-inline"></span><p class="topic-paragraph"><strong><span id="ref151827"></span>keel</strong>, in <a href="https://www.britannica.com/technology/ship-construction" class="md-crosslink autoxref " data-show-preview="true">shipbuilding</a>, the main structural member and backbone of a <a href="https://www.britannica.com/technology/ship" class="md-crosslink autoxref " data-show-preview="true">ship</a> or <a href="https://www.britannica.com/technology/boat" class="md-crosslink autoxref " data-show-preview="true">boat</a>, running longitudinally along the centre of the bottom of the hull from stem to stern. It may be made of timber, metal, or other strong, stiff material. Traditionally it <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="constituted" href="https://www.merriam-webster.com/dictionary/constituted" data-type="MW">constituted</a> the principal member to which the ribs were attached on each side and to which the stem and sternpost were also attached. Another type of main keel—properly, the “<span id="ref151828"></span><a href="https://www.britannica.com/technology/full-keel" class="md-crosslink ">full keel</a>,” or “ballast keel”—is a vertical downward extension of the boat’s hull, narrowly V-shaped; it is usually ballasted or weighted for stability and lateral resistance.</p><div class="one-good-fact-module"> </div><span class="marker MOD1 mod-inline"></span><span class="marker PREMOD2 mod-inline"></span><p class="topic-paragraph">The backbone keel may be supplemented by other keels (<em>see</em> <span class="link-blue media-overlay-link asmref" data-href="/media/1/314095/6224">Figure</span>). A “centreboard”—also called a <span id="ref151829"></span><a href="https://www.britannica.com/technology/centreboard" class="md-crosslink ">drop keel</a>, or sliding keel—is a retractable keel midships that may be lowered to increase lateral resistance and prevent sideslip. A “<span id="ref151830"></span><a href="https://www.britannica.com/technology/skeg" class="md-crosslink ">skeg</a>” is an aftward <a class="md-dictionary-link md-dictionary-tt-off eb" data-term="extension" href="https://www.britannica.com/dictionary/extension" data-type="EB">extension</a> of the keel intended to keep the boat moving straight and to protect the propeller and <a href="https://www.britannica.com/technology/rudder" class="md-crosslink autoxref " data-show-preview="true">rudder</a> from underwater obstructions. A “<span id="ref151831"></span><a href="https://www.britannica.com/technology/fin-keel" class="md-crosslink ">fin keel</a>” is a narrow plate (of wood, metal, or other material) fixed midships to the keel of a shallow boat (such as a racing yacht) and projecting downward to provide lateral resistance. It is intended both to steady the boat and to make it handy to steer. A “<span id="ref151832"></span><a href="https://www.britannica.com/technology/bilge-keel" class="md-crosslink ">bilge keel</a>” is one of a pair of longitudinal plates that, like fins, project from the sides of a ship or boat and run parallel to the centre keel. They are intended to check rolling. On large ships the outward <a class="md-dictionary-link md-dictionary-tt-off eb" data-term="projections" href="https://www.britannica.com/dictionary/projections" data-type="EB">projections</a> of the bilge keels may be slight; on small yachts they may be comparatively deep.</p><span class="marker MOD2 mod-inline"></span></section> <span class="marker end-of-content"></span><span class="marker after-article"></span></div> <div id="chatbot-root"></div> </div> </div> </div> <div class="ai-dialog-placeholder"></div> </div> </div> <aside class="col-md-da-320"></aside> </div> </div> </div> </div> </article></div> </div></div> </div> </main> <div id="md-footer"></div> <noscript><iframe src="//www.googletagmanager.com/ns.html?id=GTM-5W6NC8" height="0" width="0" style="display:none;visibility:hidden"></iframe></noscript> <script type="text/javascript" id="_informizely_script_tag"> var IzWidget = IzWidget || {}; (function (d) { var scriptElement = d.createElement('script'); scriptElement.type = 'text/javascript'; scriptElement.async = true; scriptElement.src = "https://insitez.blob.core.windows.net/site/f780f33e-a610-4ac2-af81-3eb184037547.js"; var node = d.getElementById('_informizely_script_tag'); node.parentNode.insertBefore(scriptElement, node); } )(document); </script>  <script> window.ap3c = window.ap3c || {}; var ap3c = window.ap3c; ap3c.cmd = ap3c.cmd || []; ap3c.cmd.push(function() { ap3c.init('ZO4siT4cLwnykPnzZWJtd3Byb2Q', 'https://engage.email.britannica.com/'); ap3c.track({v: 0}); }); ap3c.activity = function(act) { ap3c.act = (ap3c.act || []); ap3c.act.push(act); }; var s, t; s = document.createElement('script'); s.type = 'text/javascript'; s.src = "https://engage.email.britannica.com/app.js"; t = document.getElementsByTagName('script')[0]; t.parentNode.insertBefore(s, t); </script> <script class="marketing-page-info" type="application/json"> {"pageType":"Topic","templateName":"DESKTOP","pageNumber":1,"pagesTotal":1,"pageId":314095,"pageLength":265,"initialLoad":true,"lastPageOfScroll":false} </script> <script class="marketing-content-info" type="application/json"> [] </script> <script src="https://cdn.britannica.com/mendel-resources/3-130/js/libs/jquery-3.5.0.min.js?v=3.130.14"></script> <script type="text/javascript" data-type="Init Mendel Code Splitting"> (function() { $.ajax({ dataType: 'script', cache: true, url: 'https://cdn.britannica.com/mendel-resources/3-130/dist/topic-page.js?v=3.130.14' }); })(); </script> <script class="analytics-metadata" type="application/json"> {"leg":"A","adLeg":"A","userType":"ANONYMOUS","pageType":"Topic","pageSubtype":null,"articleTemplateType":"MEDIUM","gisted":false,"pageNumber":1,"hasSummarizeButton":false,"hasAskButton":false} </script> <script type="text/javascript"> EBStat={accountId:-1,hostnameOverride:'webstats.eb.com',domain:'www.britannica.com', json:''}; </script> <script type="text/javascript"> ( function() { $.ajax( { dataType: 'script', cache: true, url: '//www.britannica.com/webstats/mendelstats.js?v=1' } ) .done( function() { try {writeStat(null,EBStat);} catch(err){} } ); })(); </script> <div id="bc-fixed-dialogue"></div> </body> </html>

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