Hi Don, >I have >found values in the literature for Cd anywhere from 0.06 to 1.9. Sounds right - see Cd values tabulated below for our wind drag estimates. These are same as used in the VPP I mentioned in last post. >For example, do sailboats calculate the area of the rigging? Must be included - rigging is a significant drag. Roller furling headsails are especially high drag. >On the other hand it is not to difficult to measure these values in the >field. Neat - do you use a strain gauge on your rode termination? >As for Gerr equations, and the tables in 201 What is "201". I'm familiar with Gerr's prop book. What is the book you are referring to? >By the way all of this assumes no dynamic (wave) loads, and no current load. Current load is fairly easy to get, since it is straight hydrodynamics. The NA did all that when he designed the hull, so hcan give you a table of force vs. velocity for your design. >defense of the AYBC tables... When I talk to NAs about ground tackle, they usually end up saying "go with the empirical stuff". E.g., Lloyds, ABYC, DNV. I think this is because the dynamics haven't been studied to a useful degree. Do you know how the ABYC table is derived? Cheers, Steve ------------------------------------------------ Stephen C. Darden Email: darden@xtra.co.nz Adagio Marine Ltd. Fax: 649/4037-213 P.O. Box 161 Voice: 649/4037-801 Russell NEW ZEALAND