Hull Shell Building

Problem49.3dm (256.5 KB)

I took the table of offsets and loaded the points into Rhino. The table precision is 1/16". Variations of that amount are noticeably visible. In the table, sloped straight lines end up having the the same Y value for different X values due to rounding.

The control points of the curves from from the table. I am told here that there should be consistency in the number of control points on the curves.

Rebuild? The problem I found with Rebuild is that for the sections that are straight lines at the top and curves at the bottom it takes a huge number of control points to get the deviation below 0.01 feet (where the 0.005’ deviations are noticeably visible).

The other issue is how to generate the shell at all. NetworkSrf cannot handle the the shaft outlet on the twin keel under the stern.

Patch, will get that area but the curve matching is poor, and at the stern its horrible.

The stern does very well as a NetworkSrf but I cannot get past the knuckle where the twin keel joins.

Do you build in segments and join together (or others have said I should not do)?

Trying to learn here.



 Way too much input there for trying to do a hull surface. What sort of point count per section is typical? It looks like these sections you are trying to use are GHS output. That skeg will give you problems modeled integral with the the hull, best to do a hull separately or better yet do a topsides above the chine fwd and then a surface for the bottom that might be able to incorporate the keel/skeg. Lots of different approaches but I would cull about 75% of those sections and you are on the right track about trying to keep consistent point counts for the curves you do use. 

Good luck!


 Where are your bow section? I opened your file and it looks like the front fell off!

 I didn't understand what you meant by twin keels until opening the model. Is the bottom flat?


I should have mentioned frame reduction in the above. However, I found that I needed all the frames, waterlines, and buttocks to get the correct shape when fairing so I just left all the frames in with the post.

I tried fairing the curves initially with a reduced number of frames and waterlines. I got everything perfect then found there were huge bumps in resulting surfaces in the gaps. I started over.

I found that using fewer frames/buttocks and waterlines resulted in serious distortions. In fact, I learned why the designers had selected the points that they did.

The bow is not finished yet. I have not faired the lines yet.

I started at the easy part where the hull is constant width. Then I expanded to the sections with straight lines. Then I moved to the hardest part, the stern.

There is a tunnel that separates the twin keels.

Half siding spans the other areas where halves do not meet.