Re: Getting a 18' trihull off the trailer?
Unstrap it, go backward really really fast and hit the brakes.
Okay, for putting it on, you can get nice foam blocks for free from any place that sells utility trailers. They ship them on them. Being that your boat is an 18 footer, and probably more than 2000 pounds, (just a guess, I am only around smaller aluminum boats) it is gonna be to hard to just push off. So, you will probably wanna tie the stern to a tree, or something that is big/ heavy, and won't move (MIL maybe

).
Then, pull the trailer forward to where about two feet are hanging off the stern. Put a block under the stern with enough shims to make it within a couple inches of the hull. Keep pulling forward and adding blocks. You will probably want someone to keep on the winch, and back it off by hand, so it doesn't want to quickly exit off the back. When you get up to the front, put the last block under, and keep backing off with the winch until the trailer is completely free. Trust me, that is when it will want to leap free. Now, you are free from the trailer. To put back on, just work the opposite, and you don't need a vehicle attached to the trailer, as if it is attached to tree you can pull the trailer under the boat using the winch. Just take out blocks as the crossbar gets near them.