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Old 09-20-2012
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Re: Moment curves

Originally Posted by bobperry View Post
Sometimes I have puzzled over things like these curves and in time come to realize that the guy who drew them up had no clue either. It was just a math construct that had little or nothing to do with boat performance. Can't say I've ever heard of that guy's designs. Maybe that says more than the abstruse curves.

I use moments all the time. I even use "second moments" and "moments of inertia". I actually understand them.
I often have moments to remember.
But I never have these moments.
Bob, first off, thank you for your insight on this. If there's any info you need that you think might help just ask!

About the designer: David Philp was an Australian civil architect who trained himself to design both launches and yachts in the immediate post-war whilst Alan Payne was still in tech school. He wasn't a MRINA, but was a member of the RORC and thus became the measurer for the first few real Sydney-Hobart races (the first one wasn't a race). When this was drawn up, Laurent Giles was everyone's idol out here in the Colonies (blame Hiscock!) so we think this design is based around the Vertue.

About the curves: The engineer in me has always suspected that this had something to do with hull balance - perhaps drawn to show by the shaded areas that the finished product should steer straight at various angles of heel without any significant tendency to round up and show where those "forces" are placed along the hull... back in the days before autopilots when this was important. Again, that's just a WAG and I have no idea what the actual technical term for that is.

I'm sure the "c", "b" and "q" numbers must mean something... anyone seen Jeff lately?!?
"Honestly, I don't know why seamen persist in getting wrecked in some of the outlandish places they do, when they can do it in a nice place like Fiji." -- John Caldwell, "Desperate Voyage"

Last edited by Classic30; 09-20-2012 at 08:39 PM.
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