Introduction
Getting started
Sides 
  Skarfing
Frame
Transom 
Stem
Bending
Chines
Bottom
Gunwales
Quarter knees
Seat
Mast Partner
Keel & Skeg
Mast & Spars
Leeboard
Rudder
Sail 
Floatation 
Painting 
Resources 

The Bottom:

Mark a center line lengthwise on the ply sheet at 24”. Also a center line width wise at 48”. (This is where the center frame falls.)

Draw the 12” x 32” triangles on the corners of the ply sheet, then cut, and set aside.

Draw and cut out the frame gussets and breast hook from the other corners as shown in the drawing. (Making full sized cardboard patterns can be helpful.)

Rip a 3” strip off both sides - one will make the lengthwise butt block for glueing the bow section of the back. The other will be laminated into a backup plate for the leeboard.

Now glue the triangles to the end of the ply per the drawing and instructions below.  

Dry fit the bottom: (I assume the sides are bent but not yet glued.)

          Set the bottom on align the bow triangle and the center line of the stern with the center of the transom. Weight it in place, and tack it to the stem, frame and transom with finishing nails. How’s the fit? If it’s good congratulations! If not, aren’t you glad the transom is only dry  screwed on…;-) If necessary the position of the transom can be adjusted slightly.  

If the fit looks good it's time to disassemble the sides and glue them. Install the chine logs before the final trace of the bottom. External chines obiously make it bigger, while internal chines effect the curve of the sides.

The sides and chines are glued:

Put the bottom back in place, and trace where the sides touch the bottom. Remove the bottom and cut outside the line with your circular saw set shallow. How close you saw to the line will depend on how you intend to remove the overhang. If you flush trim with a router it doesn't much matter. If you intend to hand plane and sand, you might want to angle your saw blade 18 degrees and stay pretty close to your line. This will give less material to remove later.

          With the bottom removed, disassemble and reassemble the sides, frame stem and transom – this time with glue. Pull the string and check alignment before the glue sets up. Correct if necessary.  

I use the Japanese pull saw again for cutting off the triangles.

 Next I'll position these on the bow and mark them for gluing the butt blocks.

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After dry fitting the bow sections, get under the boat and mark the inside perimeter. This will show how much to back set the butt blocks during gluing.

  The butt blocks are made from one of  the trim pieces from the sides &  a  strip ripped off the bottom

The gluing steps are identical to those of gluing the sides. Put down plastic - dry fit & mark - spread glue with notched trowel - staple with 1/2" staples.

I once again stapled over twine which works well. I did pre-bevel the butt blocks this time using my band saw and belt sander, which seems easier than sanding the taper after they're glued.

After the back is glued up, it is dry fit and marked at chines. Make sure the boat is aligned before you mark the back. A string pulled tight from stem to stern should cross the center line of your frame. If it doesn't nudge the hull around until  it does.

The back is trimmed a little outside the line with circular saw. How close you cut it depends on your confidence and what tool you will  do your final trim with. If you flush route like I do, it's not too critical. If you'll take the overhang off with a hand plane and sanding block, accuracy cutting this line can save work. Some folks even tilt their saw blade for this.

This is a good time to fill any blemishes in the back. It's easier to sand at bench level then after it is the inside of the boat. Yes, that's Elmer's exterior filler I'm using. 

The back is now dry clamped in place. 

I made this little marker that makes it easy to mark where the nails will go in the chine log. It also has a 5" piece of wood that determines the spacing. 

Here it is in use. Mark with a pencil or an awl.

Here are some  illustrations.  Shape will vary depending on whether you have chosen to do inner chine logs or outer.

Apply glue to the chine logs, stem and transom and tack the bottom back in place, using the same finishing nail holes. Mark, drill and nail the bottom on moving from bow to stern, with a nail every 4 inches. (If you prefer SS or bronze screws can be used instead of nails. They hold about the same as nails, but they are removable. Getting the heads flush is slightly trickier.)

I pre drill for the nails and tap them all in their holes. The nails are spaced 3" apart along the transom, 4" along the sides.  These are the #14 by 7/8" bronze ring nails.

Here's a trick to insure you maintain your precious bottom alignment. Half of the boat is unclamped and propped open. Glue is applied and spread. The bottom  is then closed and clamps and nails are applied from the middle out.

I use a nail set to very slightly countersink the nails then filled them.