Creating your own homemade boat trailer is no simple task. There are numerous safety and engineering considerations to take into account when designing a trailer. A trailer is remarkably similar to a small vehicle. It requires suspension, brakes, and an electrical system. Fabricate all the components using professional quality equipment or purchase them from suppliers. Plan and design the trailer in accordance with local motor vehicle laws and regulations.
Step 1 – Obtain Plans
Obtain design instructions for a boat trailer and research local motor vehicle codes. Depending on your state, you may face restrictions on gross vehicle weight or trailer length and width. You may have to pay a registration fee and obtain a license plate for your trailer. Local law might require the use of a brake system, stop and reverse lights, license plate lights, safety chains, and emergency breakaway systems that engage the brakes if the trailer becomes unhitched.
Step 2 – Determine Trailer Specifications
Measure out the length and width of the trailer you will need. Determine the total towed weight. This will affect your choices for frame design, axle placement, brake system, hitch system, and number of tires.
Step 3 – Plan Axle Layout
Determine the dimension, capacity, and configuration of the trailer axles. You can choose round or square axles, and heavy solid or lightweight tubular axles. Axles can be mounted straight so the boat will sit high on the trailer, or with a drop between the spindles to permit a lower chassis. The number of axles you choose is a factor of trailer load and length. You need enough wheels and trailer tires to carry the load. The total load capacity is the number of tires times the load capacity of each individual tire. Use only trailer tires, not passenger tires or light truck tires. You can use bias ply, belted bias, or belted radial tires, but choose one type and use it for all the trailer tires. The axles should be fitted with mounting flanges if you are going to install brakes.
Step 4 – Assemble Frame and Install Suspension
Weld the frame together before installing the suspension kit. You can connect the suspension to the axles using leaf springs. Mount the springs to the axles with U-bolts and to the suspension with hangers. If you want the boat to ride above the fender you can place a spring on top of the axle. Use sub carriers to balance the load. Install a winch system and add vertical guides to the rear of the trailer to assist in hauling the boat out of the water.
Step 5 – Install Brake System and Electrical Wiring
Install the brake pads and the 12-volt wiring that controls the lighting system. Because the trailer will frequently be submerged in water, electric brake controls are prone to failure.