John, I recently built a Shearwater.
I recieved the kit in February, my first launch in April.
Time is tough to calculate in advance. There are many factors that make time hard to figure. There is your available time of course, what you can put into it. But there are times when you can only do an hour or so worth of work and wait for another day to proceed further after epoxy dries and your next day off, etc. The 'book' is just general guidelines, estimates. Some time frames you will match the book and other times you will be blown away by how long a step took for you to be happy with it. The weather will also effect drying times and how much you can work on the boat, depending on where you are doing the building. For me, building in the winter, if it was too cold, it took too long to heat the garage to make it worth working on the boat on some days, some days and some tasks requiring ventilation also. If it is too wet, rainy or humid, you may have to postpone doing varnish work, etc.
Also, first launch for me was 3 coats of varnish. I went back and did another 3 coats and finished just 2 days ago, second week of May. How you finish the boat will greatly effect what you refer to as a 'finished boat'. Painting will of course be faster than varnishing. Most people want to at least varnish the deck, it looks so great finished bright, even your first build will turn out great if you do your homework and take care.
My advice is to build the boat you really want to build, enjoy doing it and do not spoil it by imposing a time schedule on yourself that may or may not be realistic. Working full time and having all the other things in life going on, I would guess a range of 2 to 4 months being a practical build time frame for most people. It is difficult for me to account for my work in 'hours'. I built in 2 months, working on the boat regularly.
Here is the link to the blog of my Shearwater build if you care to take a look. The blogs are posted in reverse chronological order.....
http://shearwaterkayak.blogspot.com/
One other thing to mention you may not be aware of, you may have to wait a month (or longer?) to get your kit (I did). You can use that time you are waiting after placing your order to gather all the other things you need and prepare your shop for the build. A well lit, well ventilated and clean, organized shop will make your build so much more enjoyable.
I hope there is something of value for you here.
- Joe.