When designing a sailboat trailer, like everone said, you need to figure the wieght of the boat with the specific gear on board. You will need to figure for safety a minimum of additional 10% weight. For example a 4000 lb boat figure 4400. Depending on the keel, you will need to have high supports. You can elect to get screw pads or bunk board style. I prefer the bunk boards with four support stands each side for the bunk boards. Make sure the keel tray is big and stout. You will need brakes on both tandem axles which in many states are required. I prefer disc surge brakes as salt water in particular is not good on electric.
On the bunk board style, you can get the plastic runners to move the boat easier onto the trailer but make sure that you strap the boat down in the back so the strap is foward. If there is no bow stand on the trailer, then strap the bow down with the strap backwards. With the straps put a few twists in them to keep them from slapping and when you go 20 miles, pull over and resecure everything.
but above all, do not convert an old power boat trailer over. Most generally were not built for sailboats and I have seen many fail.
If you are thinking of buying a new trailer for a sailboat, then the most experienced and knowledgable person is Ron frisosky who has designed many for many manufactured sialboats to include hunter, macgregor, catalina, precision, seaward, etc. for Road King Trailers Under Sailors trailers. Cell phone is 941-914-3890. Normnally I do not do that but so many claim to know sailboat trailers and they do not.
Good luck
dave condon
