Used Trimaran Inspection Checklist for Folding Trimarans

How to use this checklist

Plan about three hours for a first visit on a boat of 8 to 10 metres, and ask the seller to have the boat ready to fold and unfold. Go in daylight, bring a torch, a notepad and a phone to photograph anything doubtful, and do not let a seller hurry you through the structure. A tick means you saw it and it was fine. A question mark means you want an answer from the seller or a surveyor. A cross means the problem has a price or a reason to walk away.

This list is general. Models differ, so check the specifics of the boat in front of you against its manual and the details on our model pages, for example the folded and sailing beam figures on the Dragonfly 28.

Which documents should you check first?

Paperwork costs nothing to inspect and tells you a lot about how the boat was kept. Do it before you spend time on the boat itself.

• Proof of ownership and registration: the seller’s name matches the paperwork, and the registration or bill of sale chain is complete. Check the hull number against the plate on the boat.
• VAT and customs status: evidence that VAT was paid, or the import status if the boat came from outside your country. Check current rules with the tax or customs authority.
• Service history: invoices for rigging, engine, sails and any structural repair, plus the owner’s manual. The Dragonfly 800 manual says the rigging and the Swing Wing system should be checked before every outing, so a boat with no records of either deserves questions.
• Equipment list and what is included: sails, covers, tender, trailer and electronics. Get the list in writing.
• Previous incidents: ask directly about groundings, collisions, lightning, capsize or fold-mechanism failures, and note how the seller answers.
• Trailer papers: registration, weight rating and the last inspection date, if a trailer is included.

What should you look for in the beams and hinges?

On a folding trimaran the beams, hinges and fold mechanism are the structure that holds the boat together, and they carry high bending loads. Folding structures are heavier than simple demountable ones and their joints deserve close attention. Check this area before anything cosmetic.

• Fold and unfold both amas yourself, or watch the owner do it. The movement should be smooth and even, with no jamming, grinding or sudden jerks.
• Time and effort: the builder says Swing Wing folds in under a minute per side from the cockpit, without tools. A system that takes much longer or needs force may have wear, misalignment or lack of lubrication.
• Alignment: on folding designs the parts of the beam must line up precisely for the ama to fold smoothly. Look for visible misalignment, gaps that differ port and starboard, or an ama that sits at a different angle to its twin.
• Pins, bolts, bearings and cables: look for corrosion, elongated holes, cracked fittings, rust staining and worn or frayed cables or lashings. Ask when each was last replaced.
• Locking in the open position: the ama must lock firmly. Push and pull on it, and look for movement at the joint.
• Laminate around the fittings: cracks, crazing or fine lines in the gelcoat near the beam attachments can indicate overloading. Photograph them and ask a surveyor.
• Ask how it has been used: the Dragonfly manual says folding should only be done in protected harbour areas. Ask whether it was ever folded with sails up or in exposed water.

How do you inspect the hulls and amas?

Inspect the main hull and the amas inside and out, in good light. Tap the laminate with a plastic mallet or a knuckle and listen: a dull sound against a sharper one nearby can mean delamination or water in the core, which a surveyor can confirm with a moisture meter.

• Gelcoat and laminate: star cracks, repairs that do not match, blisters, soft spots and fresh paint in one small area.
• Underside of the amas: impact damage from grounding or from taking the ground on a trailer. Amas are slim, so check the bow, the keel line and the join between deck and hull.
• Inside the amas: open inspection hatches and look for water, mould or a musty smell. Check the bulkheads and the places where the beams attach.
• Stringers and bulkheads in the main hull: look for cracks at the bonding to the hull skin, especially near the mast step and beam attachments.
• Deck hardware: fittings that have moved, cracked backing plates and wet core around bolts.
• Drain holes and bilges: a clean, dry bilge is a good sign; staining or standing water prompts questions about leaks.

Foils, rudder and steering

Daggerboard and rudder cassettes take most of the grounding loads on a shallow-draft boat, so check them with care.

• Daggerboard: look for leading-edge damage, cracks and delamination, and check that it slides in its case without binding.
• Rudder and downhaul: check the blade, the stock, the bearings and the lifting system. Look for play when you move the blade side to side.
• Steering system: tiller, cables or linkages, and the autopilot mounting if fitted. There should be no slack and no stiff spots through full travel.

Rig, sails and running gear

Rigging is a safety item, and age matters more than appearance. Ask for the date of the last full replacement of the standing rigging and the last inspection by a rigger.

• Mast and boom: corrosion at the base and at fittings, dents, cracks near spreaders and any signs of repair. Carbon masts should be checked for impact damage, which can be hard to see.
• Standing rigging and terminals: broken strands, cracked swages, corroded turnbuckles and unusually loose or tight shrouds.
• Running rigging: worn halyards and sheets, chafe points and condition of blocks and clutches.
• Sails: UV damage on the leech and foot, stretched cloth, tired stitching and shape. A tired sail wardrobe is a legitimate point to negotiate on.
• Reefing system: lines run freely and the reef points are in good condition, because early reefing matters on a light, fast boat.

Engine, electrics and trailer

Start the engine from cold, since a warm engine hides starting problems, and then run it under load if you can. Ask for the hours and service history, and note any smoke, vibration or overheating.

• Outboard or saildrive: compare the engine hours with the age and condition. Check the mount, the control cables, the fuel system and the propeller for damage. On a saildrive, ask when the seals and anodes were last changed.
• Batteries and charging: the age of the batteries, how the boat is charged and whether solar or lithium has been fitted properly with the right protection.
• Wiring and electronics: neat, labelled wiring is a good sign. Test navigation lights, instruments, VHF, bilge pumps and the autopilot.
• Plumbing and gas: look for leaks, check the seacocks open and close, and check any gas installation is in date and installed properly.
• Trailer, if included: frame rust, tyre age and condition, brakes, lights, bearings, and whether the trailer is rated for the boat’s weight. Ask about the road registration. Our model pages list the displacement of each boat, for example 950 kg for the Dragonfly 25.

What comes after your own inspection?

If the boat passes your first look, commission an independent survey. A surveyor with multihull experience is worth the extra effort to find, because folding structures are specialised. Our guide to the cost and scope of a boat survey explains what to expect and what it covers.

Use what you found to adjust your offer, not as a reason for an aggressive argument. A list of documented issues, with quotes for the repairs, is far more persuasive than a general complaint. To see whether the asking price is reasonable, compare it with similar boats in the Dragonfly price guide, and when you are ready to look at what is on the market, browse the listings on 3Hulls.