Detailing catamarans

What makes a catamaran different to detail

A catamaran has two narrow hulls joined by a bridgedeck, and the space between them, called the tunnel, shapes how the boat behaves and how it gets dirty. The cabin sits on the bridgedeck, often with a large saloon, big windows and a wide cockpit. Most cats are wide, so they take up a lot of room in a slip, and the sides of the hulls facing each other are hard to reach.

The structure has a lot of vertical and horizontal surfaces, many of them flat. The underside of the bridgedeck, the inner hull sides and the beams between hulls are all exposed to spray and sun and collect their own stains. Trampolines, which are nets or mesh between the hulls, add a surface that most monohulls lack. The decks are often wide and open, with seating, tables and lounging areas.

Catamarans appear as sailing cats, power cats and charter boats. Each type has its own demands, but all share the same basics: a wide beam, two hulls, a tunnel and many surfaces that are hard to reach from the dock. A good detailer plans the job around those features. Our guide on detailing terms explained covers terminology that may help on the phone.

Hull sides: outer, inner and the waterline

The outer hull sides are comparatively easy to reach from a dock or dinghy. The inner sides, facing the tunnel, are tougher. They are in shade much of the time and collect algae, salt and stains, and reaching them can involve working from a tender or from the trampoline. Some cats are docked stern-in or in a slip too narrow to allow access along the inside at all.

Common problems include oxidation on the sunny outer sides, rust streaks from hardware, tannin and algae along the waterline, rub marks from fenders and dock lines, and black streaks below the cabin top. Gelcoat is the common finish, with painted hulls less usual. Cleaning and polishing follow the same principles as other boats, with extra attention to safe access and stable footing. See gelcoat oxidation removal and waterline stain removal.

A detailer works above the waterline. Hull bottom, keels or daggerboards and propellers are below the waterline and belong to a diver or yard. Cats sit on two hulls, so there is more waterline to clean, and growth can be heavy in warm water. See hull cleaning above the waterline for the scope.

The tunnel and the underside of the bridgedeck

The tunnel is the least visible and most overlooked area of a catamaran. The underside of the bridgedeck is hit by waves and spray, and it stays damp and shaded. Algae, mildew, salt crust and dirt collect on it, and so does a black or brown film from stagnant water and marine residue. It can look dirty even on a boat that is otherwise clean.

Cleaning the underside means reaching up and working overhead, which is awkward and wet. A detailer uses soft brushes on extension poles, appropriate cleaners and a lot of fresh water, working from the trampoline, a dinghy or a stable platform. The aim is to remove growth and film without scrubbing the gelcoat or loosening fittings. Safety is a key issue because the footing on trampolines and tenders is unstable, and no one should lean over a drop to reach a stain.

It helps to know what is up there. Some tunnels have hatches, sensors, transducers, cables and bridge-deck fittings. Cleaning should avoid forcing water into hatches or electrical areas. Report anything that looks damaged, such as cracks, loose fittings or delamination signs, and leave repair to a boat repair professional.

• Underside surfaces: soft brushes on poles, fresh water, mild cleaner.
• Stay off unstable footing and avoid leaning over drops.
• Keep water out of hatches, sensors and electrical areas.
• Report cracks, loose fittings and signs of delamination.
• Leave repairs to qualified boat repair professionals.

Trampolines and netting

The trampoline, the mesh or net stretched between the hulls at the bow, is one of a catamaran's most distinctive features and one of its trickiest cleaning jobs. It is made of woven synthetic fiber or open mesh, and it takes sun, salt, sunscreen, sand, bird droppings and mildew. Over time it fades, stiffens and loses strength.

Cleaning is gentle: a fresh water rinse, a soft brush and a mild boat-safe soap, followed by a thorough rinse. Strong chemicals and harsh scrubbing can weaken the fibers and the stitching. Bleach should not be used on trampoline material. Let it dry fully in the sun. Pressure washers are not recommended, because they can force dirt deeper into the weave and damage the lacing.

A trampoline is a structural item, and its condition matters for safety. Frayed edges, damaged stitching, loose lacing, soft spots and stiff, brittle fabric are signs it may need repair or replacement, which is a task for a canvas or rigging professional. A detailer can clean it and point out weak spots, but should not stand on a trampoline that looks unsafe or ask anyone to walk on it for a photo.

Wide decks, saloon and the cockpit

Catamaran decks are wide, open and used for living. The cockpit at the rear often holds a large table, seating and a galley area, with the saloon opening onto it. Sunpads sit on the cabin top or forward. Teak, non-skid, vinyl and canvas combine here, and each takes a different approach.

Non-skid on wide decks collects dirt, sunscreen and algae and needs scrubbing with a stiff brush and a proper cleaner. It should never be polished. Teak, where present, is cleaned along the grain and brightened if gray. Vinyl sunpads and cockpit cushions suffer from sunscreen stains, mildew and fading. See non-skid deck cleaning, teak deck care and vinyl upholstery cleaning.

Because the beam is wide, the deck is large, and a detail takes methodical coverage: forward to aft or port to starboard, with the work sequenced so that wet areas are finished before dry ones are polished. Cats are popular for charter and for families, so the boat often carries more guests and more mess than a monohull of similar length.

Large glass, hatches and the saloon

Many catamarans have big saloon windows, panoramic glass and sliding doors, with plenty of hatches in the hulls and cabin top. These show spots and streaks easily. Salt and hard water leave mineral deposits that etch glass if neglected, and the glass is often at a height that catches sun and dirt.

A careful glass routine starts with a fresh water rinse to remove grit, then a gentle cleaner, a squeegee or microfiber cloth and a final check from inside and outside at different angles. Plastic hatch lenses and clear panels are softer than glass and scratch easily, so soft cloths and plastic-safe cleaners are the rule. See marine window glass cleaning and water spots on windows.

Seals around windows and hatches matter on a catamaran, because water that gets into the saloon causes mildew and odor. A detailer notes failing seals and stains near them, but resealing is a repair task.

Ladders, stern steps and swim platforms

Catamarans are boarded from the stern steps or from a swim platform on each hull, and these are heavily used. They collect salt, sunscreen, marine growth and wet footprints. Stainless ladders and handrails develop tea staining, and teak or composite steps wear and gray.

Steps and platforms should be cleaned with care because they are safety surfaces. Non-skid is scrubbed, not polished. Algae and slime near the waterline make steps slippery, and removing them improves safety. Stainless is cleaned and polished and protected. See swim platform cleaning and stainless hardware cleaning.

Dinghy davits, tender cradles and outboard mounts at the stern collect the same dirt plus fuel and oil. See oil stains on swim platforms for how these are cleaned. A tender stored on davits should be rinsed before it is hoisted so it does not mark the transom and platform.

Canvas, bimini and enclosures

Many cats have large biminis, hardtops, enclosures and sail covers. A big canvas area means more mildew risk and more fading. Clear vinyl enclosures scratch and cloud, and stitching degrades in sun. These pieces take real effort to replace, so gentle care pays off.

Clean canvas with products made for it, using soft brushes and a lot of fresh water. Let it dry fully before it is folded or put back. Treat mildew early. Use plastic-safe products on clear panels and soft cloths. See canvas and isinglass cleaning, protecting canvas and enclosures and cloudy isinglass.

Work above on a hardtop or bimini frame involves height and unstable footing. A detailer should not stand on canvas or frames, and should reach safely from a ladder or a stable platform. If something cannot be reached safely, it is left.

Interior, hulls below and moisture control

The interior of a catamaran is spread across two hulls and the saloon. Each hull has cabins, heads and lockers. The saloon has seating, a galley and a nav area. That is a lot of space to ventilate, and moisture builds up in closed hulls in the same way it does on any boat.

A detailer cleans interior surfaces, treats mildew where reachable, sanitizes heads and galleys and notes damp spots, odors and any water in the bilges. They do not repair leaks or plumbing. See interior detail, head and galley sanitizing and odor removal.

Ventilation is the best prevention. Air conditioning in each hull, dehumidifiers and open hatches on dry days help. Cats often have many hatches, and keeping them closed in the rain and open in dry weather is a habit worth building. Our guide on interior humidity control describes what works.

Slips, docks and working around the beam

The wide beam of a catamaran affects how it sits in a marina. Many cats berth at end-ties, face docks or dedicated multihull slips, because standard slips are too narrow. In a tight slip, access to the inside of each hull may be limited, so a detailer may need a tender or paddle craft to reach those surfaces.

Marina rules apply here as elsewhere, and multihull docks can be busier and shared. Check what is allowed for contractors, water use and products. Our guide on dockside detailing marina rules describes what is common. Always protect neighboring boats from overspray and drips.

Charter cats and rental fleets need fast, consistent turnover between guests. See charter yacht detailing and charter turnover cleaning. Private owners can choose recurring service to keep the boat ready. See recurring maintenance plans.

Getting your catamaran detailed

When you call, describe the boat: sailing or power, length and beam, hull finish, trampoline type, how much teak and canvas, the marina and the slip, and how it is used. Mention any access problems, such as tight slips or a boat on an end-tie. Photographs of the tunnel, trampoline and hull sides help.

Quotes are given by phone only. If the job is complicated, an on-site visit comes first, and a service call charge applies. That charge is explained on the phone before anyone is dispatched. Work at height, rigging, trampoline repair, canvas repair and bottom cleaning are referred to the right trades.

A catamaran that is cleaned in a methodical way, from the high decks to the tunnel, looks better and lasts longer. When you are ready, call the number on this page and talk through what the boat needs.

Questions people ask

Related pages

Reaching the tall, wide places that a monohull never has

A catamaran's size and shape create access problems you do not meet on a single hull. The topsides are high, the cabin top is broad, and the beam can put the outer hulls out of reach from a normal slip. Cleaning crews often need a dinghy, a long pole or a combination of methods to cover every area safely. The work is planned section by section so that each area is reachable, with stable footing and tools that do not require leaning over the water. That small habit tends to pay off across the whole season.

The cabin top and the flybridge area, if there is one, can hold a lot of grime because they sit above the waterline and catch bird droppings, salt and dust. Cleaning them means working carefully at height, so the crew uses non-slip footwear, keeps tools secured and avoids working in strong wind. Solar panels, antennas and other fittings are cleaned gently, with attention to the edges where water and dirt collect and where a hard spray could cause trouble. It is a modest step, but it prevents a surprising amount of rework.

Owners can help by telling us about any areas that are unusually hard to reach or any equipment, such as a davit, a hardtop or a radar arch, that gets in the way. If the boat can be repositioned in the slip, that sometimes opens up access to a hull side that is otherwise blocked. A little planning in advance helps ensure that every part of the catamaran gets proper attention, not just the areas that are easy to reach from the dock. Ask questions at any point, and we will explain what we are seeing.

Twin engines, twin bilges and the details that double

Almost everything on a catamaran comes in pairs, and that includes the maintenance. Two engine bays, two sets of hull storage, two bilges and often two heads mean twice the surfaces and twice the places for moisture and smells to settle. A thorough detail checks both hulls equally, as it is easy to focus on the side with the better access and to leave the other with less attention. The crew works through each hull methodically to keep the standard even. Nothing here needs to be rushed, and good planning keeps the work calm.

Moisture is the most common concern. Cabins in the hulls are lower and often less ventilated, which can lead to mildew on cushions, lockers and hull liners. Opening hatches, using fans and checking behind panels are all part of the process. Airflow matters more than any product, and we may suggest changes in how you ventilate the boat when it is not in use. These simple steps can prevent a good deal of trouble over a humid South Florida summer. South Florida heat and humidity make this detail matter more than people expect.

Because so much of a catamaran's usable space is inside the hulls, storage areas often hold gear, spares and supplies that can be in the way. Clear access before the visit helps everything go smoothly. If there are items that cannot be moved or areas that should not be opened, tell us in advance. We would rather work around your instructions than guess. The scope and any quote are explained before work begins, so you will know what is included. If anything looks different once the work starts, we stop and talk it through first.