The Optimist has a pram hull, originally formed primarily from five pieces of plywood. It was the biggest hull Clark Mills could make from two 4 ft by 8 ft sheets. Just in front of a bulkhead, which partitions the boat nearly in half, is the daggerboard case. Right behind it on the centerline of the hull floor are attached a pulley and ratchet block. These anchor the sheet and its pulley on the boom directly above. At the bow resides a thwart to support the mast which passes through a hole in its centre to the mast step mounted on the centre line of the boat.
The single sail of the Optimist is sprit-rigged. Two battens stiffen the leech. It is secured evenly with ties along the luff to the mast and along the foot to the boom, pulled down tightly by a vang. The light, slim third spar, the sprit, extends through a loop at the peak of the sail; the bottom rests in the eye of a short cable or string which hangs along the front edge of the mast. Raising and lowering the sprit and adjusting the boom vang allow for adaptation of sail trim to a range of wind conditions. It is usually correct to tighten the vang and sprit in heavy winds and loosen them in light winds. As well as this, huge adjustments can be made to sail shape, due to all of the ties running along the mast and boom.
The painter, a rope used for securing a boat like a mooring line, is usually tied around the mast step.
Buoyancy bags are installed inboard along each side in the front half of the boat and at the stern to add buoyancy in the event of capsizing.
Originally designed in 1947, the Optimist Dinghy has become the world standard as both the introductory junior trainer and a premier one design racing class. It is the only sailboat designed specifically for children allowing them to learn the essentials of sailing without danger or fear. It is also the biggest and fastest growing racing class in the world with over 300,000 hulls built worldwide.