Quite a while ago I came across this document on how to build a boat trailer. I don't know who wrote it but am offering it up for those who are contemplating building their own boat trailer. If you are the owner of this document I am happy to attribute it to you. For some reason the author is not mentioned in the article.
Update: These boat trailer plans are originals created by Ken Hankinson, and the current copyright holder of these plans is Glen-L. We have removed the plans from Fishyfish. If you are looking for plans on how to build a boat trailer please visit Glen-L and purchase a set of their Boat Trailer Plans
How to Build Your Own Boat Trailer & Boat Trailer Plans