Inflection points

[Mr. Tonci Pirovic 3]

Hi All,

 

  it's nice to be part of  FFW / CAESES forum!

 

  I'd appreciate your advice on some ideas I've been playing with for some time now...

 

  For the all curved transverse section I'd like bottom to be part of an ellipse, connecting to upper curve with G2 continuity. Furthermore, I'd like to control the position of the inflection point of the upper curve ( with  some basic curves for example, for construction of the hull metasurface...)

  Still not sure about bilge area up to waterline, but I should be able to control immersed sectional area of the wet curves combination...

 

 

Thanks in advance!

Tonci

 

 

[Mr. Claus Abt 14]

HI Tonci,

If you use an fspline to extend the ellipse, you can set the curvature myfspline.startcurvature(myellipse.getcurvature(1,0)). Sorry, this is hidden functionality beacuse curvature is not always easy to control and the fspline might not find a solution. But I use it quite often and it usually works. For the inflection point you have a good chance if you do not restrict the end condition of the fspline, except the location.

 

Cheers

Claus

[Mr. Claus Abt 14]

Here you find a small example setup. There are two points, one at the inflection the other one at the deck. Please select them and move them around. The zero curvature should stay more or less at the inflection point.

 

Claus

 

 

sectionExample.fdb

[Mr. Tonci Pirovic 3]

Hi Claus, thank you very much on swift answers! This is very fine example of the powerful fspline features. Combining techniques you suggested, it is possible to obtain very nice and usefull sectional shapes...

[Mr. Mattia Brenner 6]

Hi Tonci,

 

here is some more input about curve definitions that will hopefully give you some additional ideas.

 

I am often using combinations of FSplines. For longitudinal curves, I often use a feature that I created called "Multi-segmented Smooth Curve" (you can find it in the features menu under "Hull Design").

Based on the basic procedure used in that feature, one can think of several possible improvements. E.g. I have added the option of setting C2 continuity at the joint between the segments (see feature "CurveAdvancedGenericBasic" in the attached ZIP file).

Another thing I tried, is to automatically determine a reasonable tangent at the middle point of a two-segmented curve by using the mean tangent of two FSplines coming from both sides (see the feature in the attached project file "smartSectionDefinition", btw: not only useful for sections).

 

Cheers,

Mattia

smartSectionDefinition.fdb

CurveAdvancedGenericBasic.zip