Picking arbitrary points along that curve to interpolate (as I did) really isn't kosher. While I'm at it, I should also do a better job creating that bottom bulb profile curve that I revolved to get the initial bulb surface. I see the error now (it's not even horizontal!) oops, really should redo that.

For the center axis of the bulb, I started a horizontal line from the tail and it's VERY CLOSE to the 42' line - so close, in fact, that it was a mistake for me not to use the 42' line. They are where I located the scaled NACA cross sections for lofting. 3dm file I linked to has all these horizontal lines from the PDF, at six inch intervals except for the first one at three inches. Or did you mean the bottom of the fin? Probably the center of the bulb but I didn't count on that.ĭo you have Rhino? The. ) Updated Rhino file, same link as before: beiley_f235_keel_bulb_64-012A.3dmĬlearly NOT the bottom of the keel/bulb. This change took more time in Photoshop than Grasshopper. As to decreased density, give me a number? Easily fixed by scaling the bulb slightly wider, eh?Ĭompared to 707.9 for pure lead? ~98.2% - so for this shape, we need 18 lbs. Yeah, Bens, Grasshopper is WAY COOL! Love it. ' COV' is 'Center Of Volume', AKA 'Center Of Gravity (COG)', located ~24' below the hull while the bulb draws 44.2'.Ĭuriously, the combined fin+bulb uses 'only' 1.27 cubic feet of lead. In this diagram, ' COA' is 'Center Of Area' of the cross-section, not the surface. So I scaled the bulb horizontally (only in the Y direction, width not length) until the weight was correct. Looked pretty good but, after subtracting the intersected fin, the volume/weight was less than the specified 265 lbs. beiley_f235_lead_keel_64-012A.3dmįor the bulb, I decided to try a 'surface of revolution' using the profile as drawn. Using a NACA 0012 section and not including the bulb, I get 1,617.66 cubic inches = 662.76 lbs. Part 1: Shaping the Keel/Bulb (this page). Images posted to SA threads were lost on the forum when DropBox dropped support for that sort of hosting, so I'm posting my original images here in the context of that thread. More Marine Design Keel/bulb Replacement on Beneteau First 235 NACA Foils using Rhino Grasshopper, from an SA forum discussion, December, 2016 (ProaSailor)

Clark y airfoil