Boat Design Forums  |  Boat Design Directory  |  Boat Design Gallery  |  Boat Design Book Store  |  Thanks to Our Site Sponsors

Go Back   Boat Design Forums > Employment and Education > Education

Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 04-12-2016, 01:40 AM
xichyu xichyu is offline
Junior Member
 
Join Date: Apr 2016
Rep: 10 Posts: 91
Location: Dalian,Liaoning,China
How to obtain the maximum righting arm of a righting arm curves?

Areas under righting arm curves are carried out using 2nd order integration. Likewise, the
maximum righting arm is determined by a series of predictions and trials based on 2nd order
interpolation.
But I do not know the concrete details
How to obtain the maximum righting arm of a righting arm curves?
Reply With Quote
  #2  
Old 04-12-2016, 02:47 AM
TANSL TANSL is offline
Senior Member
 
Join Date: Sep 2011
Rep: 300 Posts: 3,946
Location: Spain
For the point of maximum abscissa of a GZ curve [y = f (x)] you need to determine the point to which the first derivative is zero: dy / dx = 0.
This you could get two points. Choose the one that has a positive orderly.
There are other not so simple methods.
Reply With Quote
  #3  
Old 04-12-2016, 07:29 PM
xichyu xichyu is offline
Junior Member
 
Join Date: Apr 2016
Rep: 10 Posts: 91
Location: Dalian,Liaoning,China
Quote:
Originally Posted by TANSL View Post
For the point of maximum abscissa of a GZ curve [y = f (x)] you need to determine the point to which the first derivative is zero: dy / dx = 0.
This you could get two points. Choose the one that has a positive orderly.
There are other not so simple methods.
Thanks
Reply With Quote
  #4  
Old 04-12-2016, 08:07 PM
gonzo's Avatar
gonzo gonzo is offline
Senior Member
 
Join Date: Aug 2002
Rep: 2031 Posts: 11,897
Location: Milwaukee, WI
On a cartesian coordinate system, it is the highest point on the curve. Depending of the degree of precision you need, a simple visual inspection may be enough. Even though the maxima of a curve can be calculated easily by integration, most stability curves do not have a precise equation to describe them. Often they are approximated during the design process and later corrected by inclination tests.
__________________
Gonzo
Reply With Quote
  #5  
Old 04-12-2016, 09:02 PM
xichyu xichyu is offline
Junior Member
 
Join Date: Apr 2016
Rep: 10 Posts: 91
Location: Dalian,Liaoning,China
Quote:
Originally Posted by gonzo View Post
On a cartesian coordinate system, it is the highest point on the curve. Depending of the degree of precision you need, a simple visual inspection may be enough. Even though the maxima of a curve can be calculated easily by integration, most stability curves do not have a precise equation to describe them. Often they are approximated during the design process and later corrected by inclination tests.
In some cases the top is not obvious, may be flat or double humped
Reply With Quote
  #6  
Old 04-13-2016, 03:00 AM
TANSL TANSL is offline
Senior Member
 
Join Date: Sep 2011
Rep: 300 Posts: 3,946
Location: Spain
Quote:
Originally Posted by gonzo View Post
On a cartesian coordinate system, it is the highest point on the curve.
As stated by the OP, there may be relative maximums that are not so easy to find. It seems that the OP knows better than you what he is talking about.
Quote:
Originally Posted by gonzo View Post
Depending of the degree of precision you need, a simple visual inspection may be enough.
That's something no responsible designer would dare to do.
Quote:
Originally Posted by gonzo View Post
Even though the maxima of a curve can be calculated easily by integration, most stability curves do not have a precise equation to describe them.
The maximum of a curve can not be found by integration. That is nonsense.
All curves, including stability (GZ or DN values) can be defined by a precise mathematical equation, or set of equations.
Quote:
Originally Posted by gonzo View Post
Often they are approximated during the design process and later corrected by inclination tests.
In the design process you calculate several values, which can not be changed with the data obtained from the inclining experiment. When you do experiment long months have passed since you made the project and the boat, of course, is already built.
The project data and curves are not corrected. The stability booklet based on the data of experience is made. But this is a completely different thing and sometimes it is not even the designer who does the experience.
Reply With Quote
  #7  
Old 04-13-2016, 07:35 AM
gonzo's Avatar
gonzo gonzo is offline
Senior Member
 
Join Date: Aug 2002
Rep: 2031 Posts: 11,897
Location: Milwaukee, WI
Designing and calculating graphically has been done for centuries and still is used with success.
__________________
Gonzo
Reply With Quote
  #8  
Old 04-13-2016, 08:01 AM
TANSL TANSL is offline
Senior Member
 
Join Date: Sep 2011
Rep: 300 Posts: 3,946
Location: Spain
Of course, but that has nothing to do with what you say in your post # 4, which are nothing but totally incorrect statements.
Reply With Quote
  #9  
Old 04-13-2016, 10:53 AM
gonzo's Avatar
gonzo gonzo is offline
Senior Member
 
Join Date: Aug 2002
Rep: 2031 Posts: 11,897
Location: Milwaukee, WI
So you say that the highest point on a curve on a Cartesian coordinate graph is not the maxima?
__________________
Gonzo
Reply With Quote
  #10  
Old 04-13-2016, 11:27 AM
TANSL TANSL is offline
Senior Member
 
Join Date: Sep 2011
Rep: 300 Posts: 3,946
Location: Spain
No, I did not say that at any time. Do not try to divert attention to another site. Reread what you have written in your post # 4, which are nothing but nonsense, and what I answer in post # 6.
Reply With Quote
  #11  
Old 04-13-2016, 01:20 PM
gonzo's Avatar
gonzo gonzo is offline
Senior Member
 
Join Date: Aug 2002
Rep: 2031 Posts: 11,897
Location: Milwaukee, WI
It says:"On a cartesian coordinate system, it is the highest point on the curve'
How about you stop you bad attitude and insults, stop hi-jacking threads and stick to the subject. Many posters have stopped asking questions because of you.
__________________
Gonzo
Reply With Quote
  #12  
Old 04-13-2016, 01:30 PM
TANSL TANSL is offline
Senior Member
 
Join Date: Sep 2011
Rep: 300 Posts: 3,946
Location: Spain
That's your opinion and certainly respect it. However, as everything is written, everyone can see that I at any time have insulted you or have sabotaged a thread. I just correct certain things you say that are not right and that show a complete misunderstanding of the issues being addressed. And I think I do it politely.
Reply With Quote
  #13  
Old 04-13-2016, 10:52 PM
PAR's Avatar
PAR PAR is offline
Yacht Designer/Builder
 
Join Date: Nov 2003
Rep: 3967 Posts: 17,963
Location: Eustis, FL
I agree TANSL, it seems or at least it appears many of your posts, are to directly attack or correct some minor level of semantics by Gonzo. In fact, it seems or at least appears this is your only contribution to many threads. Additionally, once I see both of your screen names, bounce back and fro in a thread, I stop participating, knowing it will simply descend into a pissing fight over some usually minor mis-statement or observation.

This thread is a classic example. Only 12 posts, 5 by you, 4 by Gonzo and 3 by the OP. All of the OP's posts where in the very first portion of the thread, the rest, your attempts to make observations to Gonzo's posts. I've seen this many times previously and this thread will dissolve into this pissing contest thing and a tit for tat spiral into uselessness, in terms of contributing to this thread.

We all mis-speak from time to time, it happens, but to intentionally seek out or hunt for these, just so you can point out your position or what you feel an appropriate response, particularly against a single forum member, just isn't acceptable behavior. You have a choice which threads to participate in.
Reply With Quote
  #14  
Old 04-14-2016, 01:13 AM
xichyu xichyu is offline
Junior Member
 
Join Date: Apr 2016
Rep: 10 Posts: 91
Location: Dalian,Liaoning,China
Thanks for all of you! Sincerely!
Reply With Quote


  #15  
Old 04-14-2016, 07:20 AM
gonzo's Avatar
gonzo gonzo is offline
Senior Member
 
Join Date: Aug 2002
Rep: 2031 Posts: 11,897
Location: Milwaukee, WI
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.
__________________
Gonzo
Reply With Quote
Reply



Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes


Similar Threads
Thread Thread Starter Forum Replies Last Post
Rudder arm? Dirteater Sailboats 2 07-27-2011
07:27 PM 
Rotating Arm Simulation dtoshni Stability 1 07-16-2009
01:43 AM 
Righting arm curve Mirko Stability 5 08-07-2007
04:46 AM 
rhino/righting arm data 3dig Software 7 05-03-2007
03:09 PM 
Heeling Arm sorenfdk Sailboats 0 04-15-2005
05:00 PM 

Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.

All times are GMT -5. The time now is 08:52 AM.


Powered by: vBulletin Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Web Site Design and Content Copyright ©1999 - 2017 Boat Design Net