{"id":1166,"date":"1999-11-30T00:00:00","date_gmt":"1999-11-30T05:00:00","guid":{"rendered":"https:\/\/setsail.com\/?p=1166"},"modified":"2009-04-14T08:29:27","modified_gmt":"2009-04-14T13:29:27","slug":"water-ballast-systems","status":"publish","type":"post","link":"https:\/\/setsail.com\/water-ballast-systems\/","title":{"rendered":"Water Ballast Systems"},"content":{"rendered":"
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Hi Steve: I have read, with a great deal of interest, several of your publications. Being interested in yacht design, I have learnt much from them. I am interested in the water ballast system you have installed in BEOWULF. It puzzles me that these water ballast systems use only sea water. Why not use the fuel and potable water that is already on board and move that around? BEOWULF would have some 12,000 lbs of combined fuel and water if all tankage was full. Why increase displacement by bringing on board an extra (up to) 7,000 lbs of salt water? The extra displacement will increase absolute stability, but is this necessary particularly when it is at the cost of added hull resistance? There could be separate ballast tanks to carry sea water when potable water and fuel are low. I would imagine there would be a case for the use of already on board fuel and water. Would you agree? Is there a reason you don’t do this? Also, would it make sense to install ballast tanks well aft, say in the stern, so as to adjust the fore and aft trim in heavy downwind\/surfing conditions to keep the bow\/cutwater out off the water to mitigate broaching tendencies? Many Thanks, Henry <\/p>\n<\/div>\n

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Hi Henry: How liquid ballasting systems are treated is very much a function of construction material, and the needs of the boat. In the case of BEOWULF, being of aluminum she has a double bottom which already has fresh water and fuel tankage for about 1,200 US gallons of liquid. This is way more of both than she normally needs or carries. <\/p>\n

The salt water ballast, carried in the hull side tanks, can be dumped when motoring or in lighter winds. If this were fresh water, or fuel, you would be forced to carry the weight.<\/p>\n

However, we have done many fiberglass boats where both fuel and water were carried outboard, along the hull side. In this case, we usually design in about twice the required capacity, so it can all be carried to weather. This is a case of the material dictating the tankage as with fiberglass it is not practical to have thin, hull bottom tanks.<\/p>\n

On the issue of trimming fore and aft with the liquid ballast: This can certainly help. In BEOWULF, for example, we fill the aft tank first, which pushes the stern down, increasing aft prismatic and helping steering control by keeping the rudder from ventilating (breaking the surface at the hull intersection). Hope this helps–Steve Dashew<\/p>\n

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Hi Steve: I have read, with a great deal of interest, several of your publications. Being interested in yacht design, …Read More<\/a><\/p>\n","protected":false},"author":3,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[21],"tags":[],"class_list":["post-1166","post","type-post","status-publish","format-standard","hentry","category-yacht-systems-faqs"],"_links":{"self":[{"href":"https:\/\/setsail.com\/wp-json\/wp\/v2\/posts\/1166"}],"collection":[{"href":"https:\/\/setsail.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/setsail.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/setsail.com\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/setsail.com\/wp-json\/wp\/v2\/comments?post=1166"}],"version-history":[{"count":0,"href":"https:\/\/setsail.com\/wp-json\/wp\/v2\/posts\/1166\/revisions"}],"wp:attachment":[{"href":"https:\/\/setsail.com\/wp-json\/wp\/v2\/media?parent=1166"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/setsail.com\/wp-json\/wp\/v2\/categories?post=1166"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/setsail.com\/wp-json\/wp\/v2\/tags?post=1166"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}