Points from 18 years' experience
I launched and recovered my Sun 27 for 18 years using a trailer. You need keel guides that flare out at the back of the trailer. You need a STRONG wheel attached to the tongue that puts it as close to the ramp as possible. You need two tall markers (we used bicycle flags) that won't damage your boat if you hit them at the rear of the trailer so that the markers and your bow upright make the center front and outside rear points visible with the trailer submerged. We welded an old trailer wheel to a channel iron with a hitch ball to attach to the trailer. We then looped 100 feet of 3/4 inch nylon line with thimbles on each end around the wheel and pinned it to the tow vehicle hitch (Trailer wheels chocked on the ramp of course). You need a long ramp in good condition as you will get about 25 to 40 feet of the (50 foot doubled) rope wet. The boat will want to rock back on the trailer when you pull it out. It helps to attach two lines to the trailer somewhere near the hitch and, after you power the boat onto the trailer, lead them to your primary winches and tighten the lines as tight as possible. This not only pulls the boat forward but tends to lower the stern some. Set your bow support so that it will not be submerged and mark a point on the bow that is just above it. Use this mark to know when you have moved the boat far enough forward with the primaries. Also mark your side markers to let you know how deep to submerge the trailer for recovery. Pull the boat out SLOWLY as the inertia will tend to stretch the lines holding it forward. We tried several approaches over the years and found this to be the best. We came up with some interesting inventions along the way but wound up with the preceding approach. Sorry for the length of this response, I didn't realize it would take a book to describe what had become automatic to us. Incidentally, if there is any cross wind, wait it DIES. This whole procedure is for recovery. To launch just let the rig into the water until you have the cooling water intake submerged, start the engine, engage reverse and have someone back the tow vehicle until you back off. Hope this helps, fair winds.
