Nick gives two methods for doing this, and they vary in how you distribute the change among the station-to-station intervals. One is to simply distribute it equally; if you're shortening the boat 16 inches and there are 17 stations (producing 16 station-to-station intervals), simply shorten the spacing one inch. The other is more complex, and I had trouble reading the formula also, but grasped the concept intuitively. Distribute the change progressively, so that the spacing at the ends changes very little and there's progressively more change toward the middle of the boat. Working with the total change and the number of spaces involved, you can arrive at a fraction with a denominator N that alllows you to distribute the change in an arithmetic progression from the end to the center, so the first space changes by 1/Nth, the next by 2/Nths, etc.
The difference between the two is how you want to change volume distribution for the boat; a simple scaling changes volume more than the proportional method he describes. If preserving volume while shortening length is important to you, then scale the distribution; if one of your goals is also to change volume as much as you can, then simple scaling is the way to go.

At least that's what I got from your book, Nick; did I get it right?

: I an going to build a Great Auk which I plan to shorten to 16' 3". The
: reason is simple, that's the biggest boat I can build in my shop and get
: it out of the basement.
: In Nick Schades book he gives a couple of formulas to change a design. I have
: spent a couple of hours trying to figure the first one out. I can not get
: the results that he gets for changing the Auk from 17' to 14'. Is there
: someone out there who can post an example or e mail how it's supposed to
: work. There is no example for the first formula and the example for the
: second formula is wrong(typo, what should be an equal sign is a minus
: sign). Is there a typo in the first formula as well, other then the fact
: that the SIGN function in the formula will not work in Excel with [] you
: need to use().
: Other then the formulas the book is great and can't wait to get started. The
: strong back is built, the plans glued to plywood and the cedar is ready to
: be cut. I have couple of days work before I'm ready to start installing
: the form so any help will be welcome.
: Many thanks in advance.
: Best regards
: Chris Hughes
: Newport RI