Help needed on alden design

I am looking for my second design to build and am interested in, and have a question on, Alden's "Charles River OD" fixed keel that you can see on their web site, if someone would be kind enough to help. There is a discontinuity in the elevation view, at the floor level, which corresponds to a change in the floor board layout that you can see in the plan view. Can someone tell me in terms that I can understand (My first project was a lapstrake skiff, nine feet, so I've got little 'real' boat design interpretation skills when it comes to serious architectural drawings. I'm learning.) what this 'step' might indicate and the implications? Also please write me if you can not find the feature that i am refering to.
Thanks in advance,
Ed

 

I have in the past found lots of co-operative Alden voices concerning getting 60 years old lofting plans.

They recommend you identify what it is you are looking for then contact Mystic Seaport Museum. Send a donation and they will dig up the thousands of pages Alden Inc. donated decades ago.

Ray T