Lackenby Generalized Shifts - Parallel mid body

[Carlos Almeida 0]

Hello,

I'm trying to use the Generalized Lackenby feature on my model, but I'm experiencing some problems:

My model has a long middle parallel body, so I'm not sure where the delta curves should end (Aftbody) or begin (Forebody):

• LPP/2 or in the middle of the parallel body? I've tried it, but free edges suddenly appear on the aft body.
• Aft body delta curve end = end of the aft body and Forebody delta curve begin =  begin of the forebody: same problem.
• No input: same problem as before and I can't figure out how the point is defined automatically.

Please take a look at the attached screenshot, which shows the free edge that appears, between the FOB surface and one of my aft body meta-surfaces, after I apply Lackenby letting CAESES decide the Aftbody delta curve end and the forebody delta curve begin. Maybe I have errors on the original model, even if the original hull is closed?

 

Best regards,

Carlos

 

 

[Carlos Almeida 0]

I've figured it out. I had to swap the domain of the FOB surface.

[Carlos Almeida 0]

Actually, I got the same errors when I tried to use different deltaXCB values. Does anyone know what might be causing that?

 

Best regards,

Carlos

[Mr. Claus Abt 14]

Please insert a reasonable knotspacing value in the BRep and datareduction afterthe transformation. The transformation might otherwise rip the geometry apart, since it moves the control points of the vessels representation. In the flat of bottom area there might be only a few and that needs to be refined.

Cheers

Claus

[Carlos Almeida 0]

Hello,

What would be reasonable values for the knot spacing and the data reduction? I can't find that info.

 

Best regards,

Carlos

[Carlos Almeida 0]

I've tried a knot spacing as small as 0.01m (my model has a length of 300m), but it doesn't work in some LCB choices.

It doesn't break the geometry for some specific values, it seems random. I can't use a smaller knot spacing.

 

Best regards,

Carlos

[Carlos Almeida 0]

Anyone?

[Mr. Heinrich von Zadow 9]

Hi Carlos,

without being able to look at the geometry its hard to tell. One option you might want to try is the knot spacing of the BRep you are transforming:

Try and increase the density of the control polygon of your hull. A value of around 1 or 0.5 might be enough (assuming the hull is around 100-250 m or something in that...). What this will do is, insert additional control points to ensure a maximum distance of 1 or 0.5 between adjacent CPs. You can verify your choice by looking at them in the display options of your BRep:

You will need enough points on both adjacent patches so that they have a chance to be within tolerances even after you have applied the transformation. In short: you need enough points to get things to work, but not too many so it doesn't get too "expensive".

Hope this helps. Cheers,
Heinrich

[Carlos Almeida 0]

Hello Heinrich,

Thanks for your response. I've tried using a knot spacing as small as 0.001 (my model has a LOA of 300m), and it doesn't work.

So there's probably something wrong with the initial meta-surfaces, but I can't figure out what, because the original model is closed.

Would you please take a look at the project?

 

Best regards,

Carlos

[Mr. Heinrich von Zadow 9]

Hi Carlos,

sorry, I totally overlooked that Claus had already suggested the exact same thing. Sure, I can take a closer look. Can you upload your project?

Cheers,
Heinrich