This plan walks you through the steps for building then enclosing a 5'3" X 8' single axle trailer using readily available materials and includes a drop-down ramp door and rounded roof. This is ready to glass the top & corners and paint to match this customer's motorhome. The plan is adaptable for larger or smaller single axle trailers.
Step 4. Cut 2 pieces of 3" channel, each 64" long and clamp to an "A"-Frame coupler for the tongue. Set upside down on the frame supported with another block. Mark a line on the channel ends that butt up to the first stringer so they can be cut off at an angle parallel to the stringer. Center the tongue so that the coupler ball socket is exactly in the middle of the trailer. Insure the tongue rails are approx. the same distance from the frame sides. Also you can place a chalk mark on the stringer centers and eye-ball the straightness looking towards the rear from the coupler ball socket. Before you weld check your accuracy by running a tape measurement from the corner of each front spring hanger to a center point on the coupler nose. Once the tongue is in the correct centered position, weld into place