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 Boat Design Forums How to obtain the maximum righting arm of a righting arm curves？

#16
04-14-2016, 08:10 AM
 TANSL Senior Member Join Date: Sep 2011 Rep: 300 Posts: 3,946 Location: Spain
It is unlikely, quite improbable that GZ curve has a flat area values. Unless you understand as "stability curve" anything else.
A double humped curve stability can exist but is not "very common". It occurs mainly in ships with a forecastle deck that encloses much volume.
#17
04-15-2016, 01:08 AM
 xichyu Junior Member Join Date: Apr 2016 Rep: 10 Posts: 91 Location: Dalian，Liaoning，China
Quote:
 Originally Posted by gonzo A double humped stability curve is very common. When it has a flat area where the maxima is, the usual graphical solution is to go a fixed distance to the right and left from either side of the flat. Then you pick the center point.
Oh，I forget the “ double humped stability curve” . Thanks
#18
04-15-2016, 07:35 AM
 gonzo Senior Member Join Date: Aug 2002 Rep: 2031 Posts: 11,897 Location: Milwaukee, WI
I meant to say "not very common"
__________________
Gonzo
#19
04-15-2016, 11:13 AM
 PAR Yacht Designer/Builder Join Date: Nov 2003 Rep: 3967 Posts: 17,963 Location: Eustis, FL
Actually, when you accurately plot a stability curve, it can have a number of "bumps" in it. Typically when the side deck submerge, a flattening on the curve occurs, then when the cabin or deck structures start to submerge, the curve spikes up again. Depending on how you calculate the curve (many don't include deck structures) and the configuration of the deck, you can have a number of bumps.

In small craft design, the curve is typically hull only, through 180 degrees. This is how I do small craft, knowing the actual AVS may be a bit higher, than the calculations show, but an error toward the higher side isn't a bad thing. On larger craft ,the deck structures have to be included, but not so much on a 22' sloop (as an example) with a small cabin on it's foredeck.
#20
04-15-2016, 07:30 PM
 xichyu Junior Member Join Date: Apr 2016 Rep: 10 Posts: 91 Location: Dalian，Liaoning，China
Quote:
 Originally Posted by gonzo I meant to say "not very common"
ha ha
#21
04-16-2016, 02:39 AM
 xichyu Junior Member Join Date: Apr 2016 Rep: 10 Posts: 91 Location: Dalian，Liaoning，China
Quote:
 Originally Posted by PAR Actually, when you accurately plot a stability curve, it can have a number of "bumps" in it. Typically when the side deck submerge, a flattening on the curve occurs, then when the cabin or deck structures start to submerge, the curve spikes up again. Depending on how you calculate the curve (many don't include deck structures) and the configuration of the deck, you can have a number of bumps. In small craft design, the curve is typically hull only, through 180 degrees. This is how I do small craft, knowing the actual AVS may be a bit higher, than the calculations show, but an error toward the higher side isn't a bad thing. On larger craft ,the deck structures have to be included, but not so much on a 22' sloop (as an example) with a small cabin on it's foredeck.
Thanks！
It is useful for me

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