This section assumes that you have decided to build upright. However, most of what will be covered applies to general construction methods.
Set up the wood framework, with the rafter spacing the same as the boat rib spacing. Weld up a length of light weight 3"channel iron, a few feet longer than the boat. Lay out the rib spacing down the center of the channel and drill a 1/2" hole for attaching each rib hanger. Also drill a small nail hole next to each 1/2" hole to attach the channel to the rafter. Place the channel on top of the rafters centered in the frame and nail it down. This is now the centerline of your boat. Next, center and level 4 or 5 railroad ties, equally spaced under what will become the keel location. Set the keel plate on the ties and your ready to hang the ribs.
Rib construction is the next step. You will need to build a large setup table of some type. A plywood table covered with light gauge galvanized tin, with legs about two foot high works well. Draw out each rib with a felt marker using the centerline and headstock line as your reference points / lines. If patterns were supplied with your plans, take care in alignment when transferring the pattern to the table. When building the ribs, tack-weld the complete rib together including the headstock brace, rib hanger, and angle bracing before a full weld is made. This will reduce movement caused by the welding process. Be sure that all the rib hanger lengths are the same from the headstock line to top of the hanger. A piece of threaded rod welded at the top of the hanger is used to make the final adjustment. As you complete each rib, hang it up and watch your boat take shape.
After all the ribs have been hung, you will need to add some bracing. This is where the extra angle iron comes into play. Pick a spot about 2/3 out on either side of the centerline at the headstock line. Run an angle iron brace the length of the boat to help maintain rib spacing and headstock alignment and tack-weld the brace. Run an angle iron brace the length of the boat about 18" below the headstock line and tack-weld it to the centerline rib hangers, checking the rib spacing as you weld.
Now lay two parallel lengths of 2"x 1/4" x 20' flat strip a foot or so apart on the inside at the bottom of the ribs and check the boat bottom curve for fairness. The strip should contact each rib evenly and display a smooth curve. Do this on both sides of the centerline. If any of the ribs need to be moved or cut apart and realigned, now is the time. However, if all the ribs line-up well, you are now ready for the boat stem and keel sides to be installed.
The type of keel that you're building, determines how the stem and keel fit together. Follow the plans and install the boat stem, keel sides, mast support, prop log, and etc.
The next step will be to install the stringers and hull skin (sheeting). Stringer setup: Using the 2" x 1/4" x 20' strip as an alignment tool, lay it inside the ribs. The natural curve of the stringer can be plotted along the ribs. With a hand square, mark each rib and cut out the notch for the stringer. When splicing stringers, use a diagonal splice along at least 6" of stringer length. This allows a spliced / welded stringer to bend smoothly. Weld only across the narrow top edge of the stringer when installing. A weld down the sides of the stringer will cause the rib to bend as the weld cools. You will finish weld the stringer during the sheeting process.