How to interpret ..

[24hacker]

a "Table of Offsets?

[Thorne]

Do you subscribe to WB Magazine? If so, see this month's issue. If not, pick up a copy...

[outofthenorm]

Pretty open question. Assuming you are asking for basic stuff, I'll give it a shot. A Table of Offsets is just a set of co-ordinates. It allows you to draw the shape of the boat and all its main pieces at full size, in 2 dimensions. The idea is to "plot" all the points defined in the table, then connect the dots with straight or curved lines that define the shape as it was intended to be. The plotting - called lofting - is usually done full-size on a big smooth white painted surface.

The co-ordinates are traditionally denoted in "feet, inches and eighths", so an entry of 2-4-3 on the table would be read as 2 ft, 4 and 3/8 inches. That point is one of a series of points spaced along a "station" line, all measured from a designated "base" line. The base line is usually either a horizontal line drawn below the keel, or sometimes it's the LWL (loaded water line). The "station" lines are vertical lines drawn at more or less equal distances to cross the base line, thereby creating a grid to hold all the points.

There are some great references for lofting. I like Vaitses book "Lofting. I'm sure others will chime in with more suggestions. If any of the above actually answers your question, I'll be surprised!

- Norm

[24hacker]

Thanks Norm What I want to do is build a model of a John Hacker boat - I am off to get a copy of this month's Wooden Boat -

[outofthenorm]

24 Hacker, the WoodenBoat section is good, and might be all you need. Drawing it out at the scale you want is pretty easy - just use a scale ruler and mark out the same inches and eighths as you would full size - no conversions!

- Norm

[24hacker]

Well - I finally figured it out - french curves don't work to well, so I ordered a set of ships curves - now the fun begins. Thanks to all