Trailer sailer is a term used to describe a sailing boat that has been designed to be easily transported using a road trailer.
It is neither a Day sailer or a Pocket cruiser but may be used for either purpose depending upon design suitability.
One feature that distinguishes trailer sailers from other small yachts is the need to launch from, recover with and transport on a road registered trailer. This places constraints on dimensions and weights. Trailer sailers mostly range in length from 5 to 10 metres (15-30 ft), and their beam must be sufficiently small to transport easily, around 2m (7 ft). Above these dimensions transport become difficult, length-width ratios become non-ideal and weights make transport without specialist equipment and skills difficult. In addition the mast and rigging must be suitable for ease of raising and lowering. The keel is most often not fixed but may be retracting, removable or swing, hydraulic, winch or electric operated and the ballast may be water that is drained to reduce weight for trailing. For simplicity and weight saving they are more likely to have a removable outboard engine.
Inherent in the design of yachts with lifting keels is the ability to approach a beach or landing close enough that the occupants may wade ashore. Such craft can sit on the bottom comfortably when the tide recedes (often referred to as "drying out"). Shallower cruising grounds can also be more readily, and safely, accessed. Lifting keels also permit the boat to be stored on the trailer at home or onshore at a marina or boat club rather than on a mooring, thus making them cheaper than larger boats. Another advantage is the quick movement between different cruising grounds: it may take weeks to sail a yacht to a new destination, whereas it may take only days to transport it by road.
There are two styles. The large dinghy style relies principally on correct crew weight for balance rather than fixed ballast, much like a dinghy and is suitable for use only on protected water. The other style is a Trailer yacht, which has a proper yacht ballast ratio of at least 30% excluding crew weight. This latter style is suited to yacht racing or cruising on inshore waters and along coastlines; a good example may pass self-righting tests and be suitable for Junior Offshore Group (JOG) or English Channel events or similar.