Taking Lines Off a Model

When Herreshoff built boats, he had a local instrument maker build a tool that let him take a table of offsets off a model. I need a tool like that. I can't find one. I have a model about 4' long that I want the lines off. I do not want to destroy the model. It can be mounted upside down to take the lines. Any ideas ?

John

 

Use a caliper and a calculator.

http://en.wikipedia.org/wiki/Caliper

 

I've wanted a "simple" system using existing digital camera whereby

you could take 2 or more pics from different angles with a few Datum Points to get the ball rolling and a computer program would be able to figure out the surface and provide a 3D image(maybe after a couple tries and some human input to coax the program to recognize the correct shadings of the different pics as the same surface) that could then be fed into CAD.

Laying thin strips of distinctly colored tape across the object might help, or rows of laser beams.

To me, this would be the #1 add on app for any CAD program. The ability to quickly and accurately load a random objects size and shape into the CAD so you can design around it.

 

Low tech-photo scale up and print on graph paper top side and front profiles.

 

There are 3-D laser scanners out there. Here is one I googled up using "3-D laser scanner seattle"

http://www.laserdesign.com/project_news/118/

I have no affliation with the company...and all the other fine print...DBEYR...NRFAL...YMMV.

 

one of the simplest is a coachbuilders forming comb, a row of spikes that take a shape, which can then be transferred to paper, great care must be taken to keep the comb square to, & a measured distance from the centreline, & at a measured height from the baseline, the deck height & the waterline must be measured also

 

.....actually the model is cut up into sections, they are traced and the lines drawn from them......destructive but practical, we did a 65 footer like that.

 

Perhaps someone local to you has a coordinate measuring machine (CMM). They are widely used in many industries to take very precise measurements of parts and tooling.

If it was a full sized craft you could have a measurer take the offsets using one of the IMS "Wand" machines. This device can be used on any boat in the boatyard to record the exact shape of the hull.

 

Have a look at "photo modeller scanner" it might work for a model. It's a cheap pc software based equivalent of a laser scanner. Just uses digital photo's from angles.


There's some arm for Rhino as well that does the job, Faro digitizing arm or something similar.

 

It's realtively easy to make a Herreshoff instrument. It is basically a pantograph. You take the lines with it by following waterlines, buttocks, etc. Then make a table of offsets, loft and fair the lines.

 

http://www.rcgroups.com/forums/showthread.php?t=276140

 

There is a fairly simple alternative that can be made by most practically inclined people.If the intended file has loaded correctly,the description follows.You need a pair of T-shaped legs to support a central board-the brown parts.The green part is free to move across the board and should have as little opportunity to move out of vertical as you can make.The blue T-section pointer is retained by the rebated edges and is free to move vertically.At a convenient location in the pointer,a hole is drilled,just large enough to admit a pencil lead.
To use the device you need to decide which locations to use for sections and mark them on the table or whatever you use for a base and you need to temporarily fix a straight edge parallel to the waterline.With the model securely in place,place the board above the model station and with either mylar or paper taped to the face of the board,run the pointer across the model while pressing a pencil against the paper.Move to all the sections required and repeat.

 

what is the beam and deck to keel dimensions of the model?