Harold Hahn

[DAWarden-(Jaager)]

a set of ship curves may be hard to find but if you Google ship curves and you get an image of a set could you use that image and make a setcut out of plastic or wood?

When you are using a computer program to loft and it is the computer version of freehand connect the dots:
and your curves are not constrained by a computer program equation - spline, Boolean(?), that thing with two external control points.
Straight up mouse or pen freehand curve gets sloppy with me. (I use a raster based drawing program, so any curve is a series of facets - which I can live with because a plane. rasp, file, mechanical and then hand sanding, scraper invariably turns it smooth)
Import a photo of each curve into your drawing program.
Use the magic wand to remove the background. Just have the black line of the curve on its layer.
The proper curve to connect the three points - rotate, scale, move the curve layer.
Select the segment of the curve that you want and save to its own layer.
Then merge that layer with the frame layer.

 

[DAWarden-(Jaager)]

This gives you a guide for drawing the frame between the two red frame lines.

The curve between the two guide frames is not an arc. It is a curve that drops off ever more rapidly. But the good part with doing this is that the curve that is drawn is fatter than it would be if it was plotted points. Fatter is good. When the hull is worked into a continuous smooth surface, the extra fat part will go away.

 

[-Waldemar-]

Half Models: Half models were the principal and often the only design tool used by many shipbuilders during the Nineteenth century in the USA and in parts of Great Britain. This excludes vessels designed for naval service by government bureaucracies where lines drawings were made. Offsets were measured from the models and sent to the mould loft floor where the design was refined. This practice was still used here on the American Great Lakes into the first quarter of the twentieth century. As Bob mentions Nathaniel Herreshoff refined this process with the invention of a specially designed machine using dial indicators to measure offsets. Many lines drawings available to ship model builders have been drawn from existing half models and sometimes tables of offsets. They (the drawings) were not used to build the ship.

Yes, the middle decades of the 19th century mark a clear separation between two quite different eras with different characteristics and practices, one might say. As a curiosity, I would like to add that in 18th-century France, for example, naval shipyards were also often sent only tables of offsets (based on an officially approved design), with the difference that these tables were based on paper plans, as opposed to measurements of half-models.

.​

 

[Bob Cleek]

QUESTION

a set of ship curves may be hard to find but if you Google ship curves and you get an image of a set could you use that image and make a setcut out of plastic or wood?

In theory, yes. In practice, no.

The irregular curve shapes of various types are high tolerance drawing templates. They work in conjunction with one another to produce fair irregular curves.



The reduced size drawings of irregular curve sets copied from drafting instrument supply company catalogs are probably not sufficiently accurate to use as patterns if enlarged to full size.

A few years ago, a fellow created a "go fund me" site to produce the full set of ship's curves in acrylic, cutting them out with a laser cutting machine. His project had to be abandoned because he discovered that the cost of laser cutting production was too expensive. Mass production was not sufficient to create economies of scale which would put the project into the black. There wasn't enough of a market for the them anymore.

 

[Roger Pellett]

Waldemar, The model that I am currently building is probably an example where the shipyard that built the ship never saw a complete lines drawing.

The Great Lakes Steamship Benjamin Noble was designed by the Cleveland, Ohio design office of the American Shipbuilding Company in 1908. She was built by their Wyandotte, Michigan shipyard located 150 or so miles away. No complete lines drawing is known to exist. Instead there is a table of offsets and a lines drawing of just her fantail stern. To build the model it was necessary for me to make a lines drawing using the table of offsets.

The original lines drawing or half model was probably destroyed by the design office. The drawing package including the table of offsets and fantail stern drawing sent to the shipyard to build the ship was saved and ultimately donated to a museum.

Roger