The Ship Model Forum

Look for official plans cover sheets that list the various dimensions. I prefer basing scale off of "length between perpendiculars". Both inboard and outboard profiles will show the perpendiculars in question.

Thanks everyone, this is good feedback on this topic.

As Pieter noted, the primary shipbuilders' figure is the length between perpendiculars. The real problem is that almost all published data, both from official sources and others, rarely includes that figure.

The second problem is that the length between perpendiculars is not always a fixed number. As an example, there are two different lengths for the carrier Victorious, one as built and the other as reconstructed. The latter is greater because Victorious had a deeper draught after reconstruction. Since the bow was not vertical but raking, the length between perpendiculars increased, but the ship's hull itself was not changed. An additional element is that, because the stern also raked, the new design waterline length also increased but again without any structural changes to the hull.

A third problem with figures, even official numbers, is determining what the numbers published actually signify. One example is the large light cruiser (converted into an aircraft carrier) Furious. All published data correctly indicates that Furious had a greater beam than its semi-sisters Glorious and Courageous. What is not apparent from this fact is that the greater beam was solely a result of deeper bulges below the water on Furious and the three ships were dimensionally identical above the waterline. Thus, the dimensions of a waterline model of Furious as built would be the same as those for the other two ships.

Maurice

Maurice that is interesting information, thanks

Yes: as Pieter and Maurice have said, the length between perpendiculars (LPP) is valid in determining the scale length of a model though the latter has indicated that there are problems, apart from the matter that the parameters for the LPP have changed over time. In a nut shell this is that one needs to known where the fore and aft perpendiculars on a given model are. That will be difficult for a waterline hull where it is likely to be impossible to establish the position of rudder post aft and where the scale waterline is on the model for the forward perpendicular. A model-builder is unlikely to want to get so involved with the problem.

That still leaves lpp as the scale factor. If you want to know if a waterline model scales accurately, get the profile plan of said ship, scale it to the scale you want using the lpp in the drawing and measure the loa and and lwl in the same scaled profile drawing. If Aoshima can do it you can do it -:)