# Methodology in fairing

DELFTship forum Hull modeling Methodology in fairing

• Author
Posts
• #39135
Kristian Odland
Participant

Dear all

I’ve just created a hull and want to start the fairing of it. In this regard, I wonder what approach/methodology to take.
I know that You can add a control curve and use the fairing function, but in my experience the point on my surface are then going in all directions, while i may want to keep the same z-position as before (i.e. waterline). is there for instance a way to lock point from moving in z-position during fairing?

Also, I know that You can convert control curves into marker curves. Is this used only for reference or am I missing something?

Lastly, there is a “fairing” button in the window-menu for points. When do I use this?

All help I can get is much aprreciated!

Kristian

• #39146
Peter Edmonds
Participant

To hold 1 or 2 of x y z while editing see the manual > The DELFTship Interface >Manually Modify Points, Control Point window
To hold X use Y Z Plane,
To hold Y Z use x-Axis.

Sometimes (eg working from pre-existing offsets) it is useful to enter numeric values for the point, rather than a drag. This is also useful at fine fairing, where you may want to increase or decrease an ordinate b a fixed amount, say 0.005, 0.001.

Once you are getting near the desired shape you can switch on the curvature combs (which are 3D) for longitudinal lines, and adjust ordinates to smooth down the curvature comb, and get the curvatures concentrated and oriented where you want them. This is very useful where a line, or its projection, is straight. Example – a sheer line straight in elevation.

Peter Edmonds
Naval Architect
Perth, Western Australia

• #39148
Kristian Odland
Participant

Regarding your answer, does this mean that You don’t necessarily use the functions for automatic fairing of points and controll curves that are available in delftship?

• #39154
Peter Edmonds
Participant

Automatic fairing is fairly new into DS. I don’t put new hull shapes through DS very often, and I just haven’t tried the auto fairing to see how its function matches my specific intents at the time.

I’d welcome comments from any readers who have become familiar with this automatic fairing, and how to use its strengths.

2 recent DS hull shapes I have done were of existing GRP power catamarans. One was from offsets lifted from an existing hull; the other from the offsets lifted from a 12 m mould, then extended to 15 m. In neither case did we need to actually generate hull structure at shape from the DS model

The smaller vessel lines essentially generated KNs and hydros; the larger n IGES hull shape, moved into Solidworks, th. My concern was to reproduce the existing shape as well as possible, including its fairness, in generating arrangement and structural drawings.

It has taken me a long time to get to the position of being able to generate a hull shape in DS, transfer to Solidworks by an IGES file, and then build the SW model, for drawings etc. I have yet to tackle using SW parts of individual hull shell plate/sheet entities, flattening with SW sheet metal, and generating cutting templates.

Peter Edmonds
Naval Architect
Perth, Western Australia