David, Larson & Elliason share some data on hull resistance and speed, and offer an empirical formula linking them. I can't remember if the surface area component is linear. It may be exponential.
For displacement hulls crewed by club racers, my intuition is that the effect of burnishing the bottom paint is weak compared to the noise of all the other variables effecting speed. However, two alternative hypotheses: 1) the orange peel texture creates resistance and is exponentially amplified by surface area. 2) the orange peel texture reduces resistance. Think about a golf ball, or Zipp's wheels. However, I doubt the fluid dynamics are the same here. Ask someone in the physics dept! On Thu, Apr 3, 2025, 5:31 PM David Knecht via CnC-List < cnc-list@cnc-list.com> wrote: > I am considering whether it is worth sanding/smoothing or burnishing the > Black Widow bottom paint that was rolled on last year. It has a typical > short nap roller orange skin like texture currently. I have read numerous > times that a smooth bottom is a fast bottom. But I have yet to see any > data and as a scientist, that troubles me. I am reminded of the bike > racing tire pressure story. For years, bike racers used small > diameter/high pressure tires because it was assumed that less contact > between the tire and the road would be faster. Obvious, right? When > someone actually did the experiment it turned out it was not faster. Now > everyone uses wide tires with less pressure. Fast plus a softer ride with > better traction. So has anyone seen data that tests hull resistance at > various stages of smoothness for non-planing hulls? I have been unable to > find anything except a reference to Bethwaite's book. Seems like an easy > experiment for a tank test. Dave > > > S/V Aries > 1990 C&C 34+ > New London, CT > > [image: pastedGraphic.tiff] > > Your contributions help pay the fees associated with this list and help to > keep it active. Please help by making a small contribution using PayPal > at: https://www.paypal.com/paypalme/stumurray All contributions are > greatly appreciated.
Your contributions help pay the fees associated with this list and help to keep it active. Please help by making a small contribution using PayPal at: https://www.paypal.com/paypalme/stumurray All contributions are greatly appreciated.
