Generating parametric Bulbous bow for ship

[Mr. Md Shahriar Nizam 0]

Hello,

I am trying to generate a parametric bulbous bow for a ship.

To know the procedure i am going through the tutorials. I am using the following procedure to make a bulb-

Documentation Browser>samples>KCS-bulb Retrofit.

 

On this sample they made a bulb based on:

 

1. LowProfile

2. Low Tan

3. maxbeam

4. uppFullness

4. uppProfile

5. upp Tan

 

I can understant the lowprofile, maxbeam, upptan. But i am not getting a idea how to make lowtan, upptan and uppfullness lines a particular ship. Again the concept of these three lines are not clear to me.

Can anyone help me out to solve this problem?

 

Sincerely,

Md Shahriar Nizam

[Willy Maschen 1]

Hey Shahriar,

 

so what happens to create the bow you sweep an fspline along the profile lines.

The upper and tan discribes the angle the bow will have at top and the lower tan will do the same for the bottom part of the bow.

The fullness is influencing the volume the bow will have at the top part.

I tried to put all this into the picture attached.

 

 

 

Hope this helps you

Greetings

Willy

[Matthias Maasch 21]

Hey Nizam,

 

in addition to Williys post please see the attached figure.

 

As I understood, the basic concept of modelling a parametric bulbous bow is clear to you but you don't understand how to connect it to an existing (and probably non-parametric) hull. I admit, in the sample file some pretty advanced methods were used to provide a smooth connection.

 

 

First of all, if you remove all the colored surfaces in the figure (except of the grey hull surface) - this is how the initial hull surface can look like, in order to start with the retrofit. So, in your case you should start with cutting out such a part of your hull.

 

The golden surface represents the fully-parametric bulbous bow. The red surface is a custom fillet suface (CAESES comes with a fillet surface type, but in this case a different surface was created by a section feature definition in order to allow for more control) which connects the hull surface (1) with the bulbous bow (2). By modelling it this way you can make sure, that the connection to the hull is smooth and free of gaps.

 

After doing that there is still a gap which is filled up by the blue surface (standard fillet surface). It connects the red custom fillet surface (3) with the upper hull surface (4). I marked the left edge of the blue surface (5) as this is the only critical point in this sample. At this surface edge the hull is not watertight. However, the length of the edge is really short and when converting the geometry representation to STL or offsets or... it won't really matter (as long as the length of the edge stays short!).

 

The only part left is the small black triangle at the stem. This can be modelled in different ways - in the sample it is again a meta surface definition which creates a section between a surface (red fillet) and a boundary curve (upper profile of the bulbous bow connected to the stem).

 

I hope the method is a bit clearer now.

 

Cheers

 

Matthias