How to balance a boat trailer
Things You'll Need
Cut three 4-foot long identical pieces of 2-by-2-inch square tubing to use as cross members on the trailer’s main frame.
Cut three additional 5-feet long pieces of square tubing with the hacksaw. These will be used as the sides of the trailer’s main frame. Set one pipe aside for later use.
Drill holes into each end of the 4-foot tubes and two of the 5-feet square tubing. Drill an additional hole in the center of each 5-foot long tube.
Join the ends of the 4-foot long pieces to the ends of the 5-foot long pieces to form a rectangle. Secure the tubes to each other with the lag bolts.
Place the remaining 4-foot long tube in the center so the holes at the center of the 5-foot long pieces are
aligned with those of the 4-foot tube. Secure the crosspiece tube with lag bolts.
Affix the light trailer axle to the center cross member of the trailer’s main frame with U-bolts.
Use the remaining 5-foot long tube to serve as the trailer’s tongue. Attach the tube to the front of the trailer with lag bolts.
Mount the bolt-on hitch to the trailer’s tongue by using the included hardware.
Weld the two wheel hubs with the wheels attached on each side of the trailer. Make sure that the crosspiece is situated behind each hub to balance the trailer.
Cut the treated lumber into several 5-feet pieces in order to form the trailer bed. Place the pieces on the trailer’s main frame and bolt the pieces to the top of the trailer frame using the lag bolts.Source: ehow.com