Boat Trailer Plans can be located at -
Boat Designs - offers a choices of 11 trailer plans to suit the 11 to 33 footer (any type of boat), twin hull or pontoon boats, and single or multiple kayaks. Load Capacity ranges from 750 lbs to 6000 lbs, with single, dual or triple axles.
Official site: www.boatdesigns.com
Northern Tool - offers a complete step-by-step guide to construct a 16' x 6' boat trailer, with a capacity to hold 3500 lbs.
Official site: www.northerntool.com
Trailer Plans - offers a variable width and length trailer model - 16' x 6' (variable up to 21'), a rugged design that's suited to a variety of boats, and with a load capacity at 2000 lbs.
Official site: www.trailerplans.com
Assembly Skills - In order to assembly a trailer its crucial to have welding skills to some degree or know someone that can take on that part of the project on your behalf.
Materials - All parts and materials that are to be used in the production of the trailers are often standard pieces of kit, so the axles, tires, suspension system, steel frame, hubs, wheels, lights & wiring, winches, brakes etc. ought to be easily picked-up at the local hardware store.
All in all, a comprehensive set of boat trailer plans is going to offer the latest, and most up-to-date trailer technology that you would expect to see in a local boat dealers showroom.