Dennis
Javafoil is easy to use and useful for sails as well as anything in the water. I find it simpler and more intuitive than Xfoil. It also handles multi-elements, which Xfoil will not do. The options page allows you to set for water or air and you can set the AR of the rig or rudder. So it does the analysis for 2D but uses a 3D correction for the AR. When I use the data for prop design I make my own 3D correction but the in-built one looks good.
Determining cavitation requires looking at the pressure plot for the foil and calculating the Cp that results in negative pressure exceeding atmospheric pressure. At 30kts the maximum Cp is 0.82. A foil with a small radius entry does not get the leading edge pressure spike of a rounded nose foil. Hence the pointier nose is better where cavitation is a consideration. This is the reason most marine propellers have pointy leading edges.
Rick
On 02/08/2010, at 8:34 AM, Dennis Cox wrote:
Hi Rick,Serious is a relative thing. Academically, messing with the Michlet and now I'm looking into some CFD... is really because I'm interesting in those things anyway. I like trying to apply them to a real world project. So, I'm going to shoot for 30, but I'm not really expecting it and if it never happens, I'll not be disappointed. If someone ribbs me for it, it won't hurt. My expectations are closer to 20... but if you design for a Ferrari, you're more likely to get it than if you design for a Jeep.BTW, what are you using... to get those numbers? (NACA0010, cavitate at 3 degrees at 30 kts). Its probably pretty obvious, that I haven't done a complete analysis top to bottom on every component. Frankly, the decoupled nature of the beast has made me lazy (if not cocky). The lee hull is "in production" so its about the only thing fixed in the design. Its pretty much relying on length and minimum wetted surface with a slightly flatter bottom... with the hope (not analyzed or expected) of getting it planing. Anything after that... most of the rest of the boat's decisions are based on carrying the 10,000 pounds in comfort and trailerable with speed third. Just having fun.Dennis
Rick Willoughby
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0419 104 821
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