2/23/13 - Floors
Lumber got delivered this week... about 200 linear feet of 1" x 8" Vertical Grain Douglas Fur. Nice stuff. With that I began cutting out the "floors" (or floor timbers). In boating terms the "floors" aren't what you may think of such as floors in a building, but rather they are more like the floor joists that support the floors in a building. The "floor boards" would be secured to the top of the floors and it's the "floor boards" that you actually would stand on. For the Simmons Sea Skiff, the floors are a very important part of the structure of the boat. The bottom, chine logs, frames, keelson, and floor boards are all fastened to the floors. The floors also establish the overall shape of the boat. If the boat is to be built structurally sound with fair lines, then it is critical that the floors be laid out and shaped accurately, as well as assembled with care in the backbone of the building jig.
The plan set includes full-size dimensions of each floor. The floors are shaped with multiple compound angels so it is important to study the plans to gain a clear understanding of the angles and direction of the various bevels that need to be cut to shape each individual floor. Dave Carnell, whom drew the plan set, uses a nomenclature of of "forward" and "aft" for describing the bevel direction. In boat school we were taught to use a nomenclature of "standing bevels" and "under bevels". A "standing bevel" would be a bevel with a positive angle from the point of reference. And an "under bevel" would be a negative angle from the point of reference. In the plan set, all the floors are drawn showing the aft faces (as opposed to the forward faces). So the aft faces are the point of reference and all the bevels marked as "forward" would be considered under bevels and the bevels marked as "aft" would be considered standing bevels.
There are 11 floors to be cut. I made each in the following fashion:
First I carefully laid out the lines of the floor from the aft face as shown in Dave's plan set.
Next I ripped cut the floor to its widest width (allowing for the thickness of the keelson), beveled to the appropriate angle. I beveled it specifically so that in my next step I could maintain the bevel when cutting the notch for the keelson.
Next I cut the keelson notch using a stacked dado blade set. I found I had a lot of tear out with the vertical grain nature of the Douglas Fir and resorted to using a backing board to eliminate it.
Next I cleaned up the keelson notch with a paring chisel and checked for an accurate bevel.
Next I drilled the limber holes. These are important for dealing with bilge water.
Next I cut the ends to the appropriate length and bevel. I did this in multiple cuts slowly sneaking up on the cut line until I knew I had both the correct angle and correct bevel.
Next I cut the tapered and beveled bottom shape by using a plywood jig with hold down clamps.
I finished by cutting the notches for stringers and stiffeners using a stacked dado blade set, then cleaned them up with a paring chisel. Then I hand cut the limber holes on each side of the keelson and scribed the center line.
Throughout the process of cutting the floors I found these two tools quite helpful. The Wixey "Digital Angle Gauge" made quick work of accurately adjusting the saw blade angle, and the Incra Miter Guage was also quick to set and quite accurate.