Working model of William Froude's hull-model shaping machine

While searching for information on skin friction drag, I stumbled upon a picture of a working model of William Froude's hull-model shaping machine. I thought some people here might find it as interesting as I did.

 

As fascinating as the model is, I would have liked it even more had there been a description of the means by which the design was turned into information the machine could follow.

 

Pantograph model shaping machines use the lines plan. The waterlines are traced with the stylus and the heads cut both sides symmetrically. There was still one in the UofM model workshop when I was there, as all towing tanks used to have them for making wax models. A quick google turns up the Scottish Maritime museum site with a lot of picture of wax models and a machine being used.
A wax hull in the cutting and shaping machine - Picture of Scottish Maritime Museum, Dumbarton - Tripadvisor https://www.tripadvisor.com/LocationPhotoDirectLink-g186588-d5789112-i244288526-Scottish_Maritime_Museum_Dumbarton-Dumbarton_West_Dunbartonshire_Loch_Lo.html

 

Cool stuff. No 'like' button.

 

So essentially it was a nineteenth century analogue version of a 3 axis CNC machine.Does the pantograph reference mean that it worked from drawings or templates that were not at a 1:1 scale? I've known people use a similar principle to shape foil section rudders and centreboards with a hand held router.

 

Pretty much. While I'm sure there are those machines that require 1:1 drawings, even in the days of paper roll drafting tables, a 20 foot long set of lines for a model would have been excessive. (That said, when I helped bring the USS IOWA back into commission in 1984/85 her spaces and arrangement drawing was on one continuous 100+ foot long drawing.)

 

That must have sucked when you needed to look at a note written in a text box fifty feet away. (That, and having to turn all the fans off, and leaving your coffee mug on the wrong side of the drawing.) My weird drawing encounter was with a book of cut-sheet electronic schematics for Minuteman. They unfolded forever, but the problem was the equipment space was a circular catwalk around the missile tube. Why did nobody think to make a pie-shaped book so the pages would unfold around the annular space?

Regarding the machine: You should be able to set the scale differently on the different axes too. So you can stretch a hull or change the beam. Handy for making model series.

 

I don't know how the machine was most commonly used, but Froude invented it for making test models, so they wouldn't have been full size, anyway, in most cases.