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I tested the new Fast Monohull tutorial and is very useful. Now I have an actual idea of a typical approach to hull modelling. I think I can get back to the previous CAESES samples (too much hard without a cookbook) and try to create a more complex hull form.
Anyway I've a couple of questions, some steps are not fully clear.

1. In the First FWD Surface feature definition (tutorial p. 11) the end tangents of the spline are defined as

.setStartTan(tanwl)

and

.setEndTan(tanwl)

I can't understand why the .setStartTan and .setEndTan arguments are read from the Z-coordinate of the curve tanwl points. The F-Spline lies on the plane Y - (Z,X) and maybe the X-coordinate of the points represents a kind of rail for the engine, so the Z-coordinate is automatically read as an output. Am I correct?

2. In the CAESES console I read the warning:

*** INFO |engines|fwd_eng1 => |f1 => |c3 : smooth curve generation from the current input data is not possible

but I can't find the problem in the code. I attach the project because I tried to model the hull without help and some names might be different.

3. I added the GetDisplacementFromSurfaceGroup feature but the output is not complete, so I tried to set a different hydrostatic calculation (see Hydrostatic Calculation tutorial). The Section Group command doesn't work properly: is the FSubSurface definition the problem? How can I walk around that?

 

Thanks for your kind attention and your help.

 

Maurizio

fastMonohull.fdbc

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Hi Maurizio,

 

 

1. In the First FWD Surface feature definition (tutorial p. 11) the end tangents of the spline are defined as .setStartTan(tanwl)

and

.setEndTan(tanwl) I can't understand why the .setStartTan and .setEndTan arguments are read from the Z-coordinate of the curve tanwl points. The F-Spline lies on the plane Y - (Z,X) and maybe the X-coordinate of the points represents a kind of rail for the engine, so the Z-coordinate is automatically read as an output. Am I correct?

 

It is exactly what you guessed! In your curve engines you set a coordinate system "Y-(X,Z)" defining that the curve engine reads the functions in the y-plane. The engine finds for every x-position a z-value as a respective function value (for e.g. WL_tan). The x-position is defined by the function Xpos.

 

You could change the coordinate system in the engine to let's say X-(Y,Z). Using this system all functions have to be in the x-plane. The engine would find for every y-position a z-value as a respective function value.

 

 

2. In the CAESES console I read the warning:

*** INFO |engines|fwd_eng1 => |f1 => |c3 : smooth curve generation from the current input data is not possible but I can't find the problem in the code. I attach the project because I tried to model the hull without help and some names might be different.

 

Your ship looks fine. The console warning just tells you that within the meta surface generation the curve c3 from your feature definition fwdsection1 is not generated properly at at least at one x-position. This is most the time no problem as the surface is still generated properly.

 

As long as your surfaces have no triangulation warnings I would ignore the console warning.

 

 

3. I added the GetDisplacementFromSurfaceGroup feature but the output is not complete, so I tried to set a different hydrostatic calculation (see Hydrostatic Calculation tutorial). The Section Group command doesn't work properly: is the FSubSurface definition the problem? How can I walk around that?

 

Yes. Unfortunately the selected sub surfaces are not read properly by the feature. Please do the following: Open your surface group "hull" and remove both subsurfaces. Then do not add the feature "aft_sub1" and "aft_sub2" to the surface group but open both features (clicking the small plus will show you all output objects) and chose the respective "subSurf" object and add those to your surface group. Re-run the feature.

 

Best regards

 

Matthias

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Hi Mattia,
 
          thanks for your help and your quick reply.

I opened the subsurfaces nodes and found the actual surfaces. I see my error, the previous surfaces group included two features.

Now I obtain a correct section group and hydrostatics output, but I realized that the alternative GetDisplacementFromSurfaceGroup feature seems to evaluate the wetted surface correctly and a wrong volume (and XCB). The Mirror flag is active, why a half volume is obtained?

 

fastMonohull.fdbc

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Hey Maurizio,

 

the problem is actually the orientation of your surfaces (see the attached picture. To visualize normals just expand the display options of the surface and set the flag for normals/(scale).

 

This problem can be fixed by creating imagesurfaces and swapping the domain. I did this in the attached project.

 

 

fastMonohull.fdbc

post-327-0-51259500-1437134351_thumb.png

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