Hullform has always been able to accept the offsets of an existing design into its own offsets table. The program can now read these values from a file, in many text layouts (e.g., as a table of lateral and vertical offsets for each hull section, or as a set of waterlines).
You can also import a Hullform design from a DXF file holding a 3-dimensional representation of the hull. For this to work, the file (naturally) has to bear some relationship to the internal model used by Hullform - this currently means that the imported design needs to be characterised by lines along the hull, preferably with transverse sections showing its shape. POLYLINE, LWPOLYLINE and some MESH entities are acceptable - feedback from users could see this list expanded.
Normally, a hull moving at close to its limiting speed carries a large
wave, high at stem and stern and low at midships. This can markedly
affect stability.
While Hullform does not calculate the disturbance of the water level, you can input an expected wave form, and find what effect it has on the hydrostatic characteristics of the hull.
The end view here shows waterlines calculated for a common form of dynamic waterline. The waterline beam near midships is significantly reduced.
Programs like AutoCAD, Generic CAD, CADkey and many others use the DXF file format to allow import and export of drawings. Using Hullform, you can generate both two- and three-dimensional representations, for import by these programs.
The output views include thickness corrections and stringer notches (See "Builder's Output", below, for more detail).
To see what Hullform can do, you can check out a sample DXF output file. It is a simple, three-line planing hull. The outputs work well for most CAD applications, and have been tested using Autosketch and GLview before being posted here - so if you have any problems, its at your end. Click to download PKZIP compressed files -
2-D orthogonal views
3-D wireframe
P.S. GLview is the best Windows 95/NT freeware DXF viewer - any search engine (Altavista, Yahoo ...) will locate you a copy, but ours came from www.snafu.de/~hg. Make sure you use its GL form, though - the DirectX version is not very stable.
You can write waterlines at a fixed vertical interval. This is needed for some drag estimation schemes, which use the information to determine wave generation and flow disturbance from first principles.
The view here shows waterlines calculated and plotted. The same lines are written directly to a file.
Using Hullform, you can calculate the exact locations of stringers on the hull surface. You can write out these locations using this menu item (You can also plot them, and roll them out into flat form - see Plate Development and Stringer Calculations.
In its most basic application, this item allows you to write the external outline of the hull (as co-ordinate pairs for each transverse hull section) at uniform intervals.
You can also define a finite skin thickness, and the program will deduct this amount, so that the outline exactly represents the outline of a hull frame. If you have created a set of stringers for any hull surface (See Stringer Calculations), the outline will include notches for these in the outline, of the correct width and thickness.
The view here is of the outlines which are written to the builder's output file.
The VRML ("Virtual Reality Modelling Language") file format is a common one for presentation of three-dimensional images in environments such as the Worldwide Web.
All version of Hullform now can write out a representation of the design in this format. With suitable software you can now inspect your design in unprecedented realism. (The views on the first page you saw were generated this way)
This output facility writes the hull and all tanks to the GHS file. You need to add some details to the file for a comparative analysis, but only a few.
The program provides for export of designs to files compatible with the Offshore Racing Congress's VPP analysis and rating program "ORC Manager". You can check out the performance potential of a racing yacht more easily than ever.