I have rogers book, and i want to use his plans, but I dont realy understand the measurement system he is using. My question is what do the numbers represent when they are writen out like this. 2-8-2
A plus or minus at the last number means to add or subtract a 16th of an inch. This is the standard way of writing offset tables, etc in boatbuilding plans for whatever reason.
Karl's reply is correct for standard measurments used in boating (feet-inches-eights) but sometimes the last notation is for sixteenths. If this happens the plans will indicate the exception in the Table of Offsets for that particular drawing. If using the plans in Roger's book just check to make sure which may mean you will have to contact him.
All the best in your venture.