Optional Notes Alternate Hull Modeling Approaches

Another method for creating the hull, favored by Mikko Oksanen, which definitely has some advantages for this hull in particular, is to take the first bow curve and instead of curving it back, is to just keep it straight as shown below. There is a file on the CD-ROM in the boat directory called Opt_1.3dm to use for reference.

Then proceed as before with the Loft and RebuildSrf and afterward trim the rounded corner off the surface shown below. See the 'trimmed surface' layer for reference.


The advantage to this method is that it doesn't create what's known as a degenerate surface. A degenerate surface is when the U and V edges share the same side of a surface. To see the effects of a degenerate surface check out the hull done the first way and use the Dir command on it and drag the UV indicator to the area where the bottom meets the bow shown below.

Notice how the green and red pointer flatten out and also the way the isoparms curve down around this area.
As far as the hull design goes this is okay but the way it effects the materials applied to the surface it leaves something to be desired, shown below. The trimmed hull is on the right.

NOTE: The disadvantage with this method is that the trimmed part of the hull edge needs to match up with the edge of the bow stem and this must be done manually and it's kind of difficult to visualize. Fortunately though for this particular boat it's not really a problem and it can easily be trimmed off and the hull edges match up with the hull nicely. But if you have a boat that has a design similar to the one below, the trim method would not work because there is no clear place to end the bow stem and start the bottom of the keel.

 

NOTE: Another disadvantage using a degenerate surface is that a CNC machine will have problems with carving out the surface.


Yet another great tip I picked up from Mikko Oksanen for visualizing how the hull lines up with the curves from the blueprints is to temporarily trim out some sections of the surface.

Open opt_2.3dm. Let's say you make the hull using only using the bow curve, curve #5, and the transom curve which is the way you would normally design a hull. If you use as few curves as possible then the hull will be much more fair. Now you have a very fair hull, but it is far from the original design. Result shown below.

To better visualize how far it is from the original lines, you can temporarily Split out sections of the hull. The original hull curves are in green as shown below. The curve used to split out the sections is on layer 'trim curve.'

What would be a good approach for fairing in the hull now would be to add and remove knots on the surface so that you had just enough CV's to edit the surface in general terms but not so many as to compromise the fairness of the hull. Another faster method would be to RebuildSrf the hull with a point count of U8 and V8 and then split the resulting surface with the 'trim curve.' Select the hull after retrimming and hit Properties and uncheck 'show surface isoparms' and now you have a surface that you can edit to the original curves. Below is hull in the process of being edited with the first two sections already roughed in.