They don't always have a positive effect, in fact many times just the opposite. There is actually quite extensive witting on the subject. You might google it. I do like Kevin's approach for anyone willing to do a little experimenting: "If you dont like the result cut it off-or change its shape (pointy on the bottom/flatter on top). Make it thicker or longer by slipping/bonding the next larger diameter, copy some other boats design. Have a blast with fiberglass. All for less than the cost of a single sail, about two days work, $1000ish dollars" Remember these things are really best at a particular speed, and usually near the hull speed of the vessel. And they can be quite noisy in a pitching situation as they 'slap' the water upon re-entry. Here are a few discussions: <http://www.boatdesign.net/forums/search.php?searchid=1178255> <http://www.yachtforums.com/forums/technical-discussion/5876-bulbous-bow.html > Brian______________________________________________________ ------ Original Message ------ Received: Tue, 04 Mar 2008 09:05:44 AM EST From: Kevin Kearney <lotusman1951@yahoo.com> To: Passagemaking Under Power List <passagemaking-under-power@lists.samurai.com> Subject: [PUP] NOSE JOBS/Bulb bows/fuel use So the real issue here is to be more effective with the platform we have or intend to own-to go back and forth on the sail issue is like,get a sail boat don't compromise a power boat--what can I say? Get a nose job--a David Taylor Bulb Bow. Why do those 1890 Spanish boats with raming thingies up front do better than our Great White Fleet? Admiral Taylor asked-and endevored to find out by buiding Model Basins to check out how and why. I live next door to the Model basin in Maryland. What does a bulb bow do? It increases waterline lenght-and thats good. It reduces pitching, Slower up, Slower down. It predisposes bow wave. Makes people ask-whats that thing up front. How do I get one--Buy a Nordhaven Hire a NA and a test tank Glue one on the front of your boat. Its not that hard, You can buy nice/strong fiberglass tanks in various diameters/lenghts say 18 inches by 4 feet, cut it to match your bow, fill it with foam, bond and fair it in. Done. If you dont like the result cut it off-or change its shape (pointy on the bottom/flatter on top) Make it thicker or longer by slipping/bonding the next larger diameter, copy some other boats design. Have a blast with fiberglass. On a Boat like mine with a traditional 40ft. waterline and 43 deck lenght, 2.5ft more on the waterline forward from the bulb and .5Ft extension on the rudder gives me a 43ft waterline--a 5-10% effeciency increase, less pitch,lots to talk about at the docks. You can paint it like shark teeth, spirials, things with eyes. All for less than the cost of a single sail, about two days work, $1000ish dollars. Don't you all get your nose out of joint, with 200,000 miles with this approach, it works. Food for thought,Kevin