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From: Mike O'Dell (no email)
Date: Tue May 17 2005 - 10:38:32 EDT
aka "Tripping o'er the forefoot" as my NavArch puts it.
curiously... (or at least it seems to me)
there's an interesting symmetry:
in airplanes, if the LCG isn't spot-on, one wants
a "nose-down" trim as that situation is more correctable
(within reason) than "nose up" trim which puts the plane
closer to a stall.
in boats, a minor error in LCG is less problematic if
toward the stern, or "bow-up" trim. trim tabs can lower the bow
but few things can raise it other than adjusting load.
as was mentioned, tripping over the forefoot in a seaway can
lead to very unpleasant movie endings.
when we tank-tested the hull of my project, it actually ran
too flat - only a degree or so bow-up. we moved the
LCG aft to get a bit more bow-up natural running trim which can
then be tuned with the ride control tabs.
btw - the good folks at Dalhousie University built the model
with their 5-axis CNC machine (foam), ran a week of tests,
and delivered a nice report with all the video for about $5K US.
that was several years ago, but at twice the price it's still
a huge bargain. true, it's not as nice a rig as the big
facility in Newfoundland, but it's a 10th the price and
perfectly adequate for hulls up to circa 60 feet (mine
at 57' is pushing the scaling limits). and wonderful people
to work with.
cheers,
-mo
Bob Austin wrote:
> If you are in a following sea, be very careful of running with tabs down. You
> could depress the bow, causing "bow steering" or a broach!
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