Repairing bulkheads and structural reinforcements
Diagnosing and repairing detached or rotten bulkheads and structural reinforcements in a yacht hull.
Bulkheads and reinforcements (stringers, frames, engine beds) form the yacht's structural skeleton — they stiffen the hull, carry the loads from the rig and the keel and divide the interior into zones. Damage to them is a serious safety problem, because it weakens the whole structure and can lead to deformation of the hull and, in extreme cases, failure under load. The commonest problems are a bulkhead detaching from the hull, rot in plywood bulkheads and cracks in the laminate of the reinforcements. Repair requires understanding how the forces are distributed through the structure.
Diagnosis calls for a careful inspection. Look for gelcoat cracks along the line of a bulkhead (a sign of movement and detachment), detached strips of laminate holding the bulkhead to the hull (tabbing), rotten or delaminated ply and signs of water. Characteristic 'spider webs' of cracks in the gelcoat around the mast step or the shroud attachments indicate overload or weakened reinforcement. Tapping and a moisture meter help locate rot. It is also worth assessing whether the hull is deformed.
The commonest repair is rebuilding the joint between the bulkhead and the hull. Detached tabbing is removed back to sound, well-adhering laminate, and the surfaces of hull and bulkhead are cleaned and keyed. New strips of glass cloth (of a weight and number of layers appropriate to the loads) are laminated with epoxy resin, running smoothly from the skin onto the bulkhead and avoiding sharp angles, which concentrate stress. A fillet of epoxy paste is often used in the corner, so that the cloth does not have to bend through a right angle.
When a plywood bulkhead is rotten or delaminated, we replace it whole or in sections. The new bulkhead is made from marine ply (certified, bonded with waterproof resins) or from laminate on a foam core, using the old one as a template. The edges of the ply are sealed with resin against moisture, and the bulkhead itself is laminated to the hull with full tabbing on both sides, if that is how the original was built. Preserving the original geometry and stiffness matters.
Reinforcements such as stringers or engine beds are repaired by restoring their profile and continuity — a damaged core is replaced and the laminate rebuilt in layers. At critical attachments (the mast step, shroud attachments, ballast/keel), the repair must restore the full load capacity, so the choice of laminate and geometry is better based on the yard's documentation or on advice from an engineer. Under-specifying the reinforcement in these places risks a catastrophic failure. This is not an area for improvisation.
After the repair it is worth establishing and removing the cause of the damage: a leak letting water into the ply, overloading of the structure, an impact or a production fault. Check the neighbouring components too, because damage to one bulkhead often means the loads have been transferred to others. When the work is done, watch the structure under load (after the first season under sail, for example), checking whether new cracks appear. A well documented repair also raises the yacht's value and the confidence it inspires.
Safety and responsibility: working with epoxy resins and glass fibre calls for a mask with an organic vapour filter, a coverall, gloves and goggles, and sanding laminate calls for dust extraction and a well-sealed dust mask, because the dust is carcinogenic and irritating. Work with ventilation and a controlled curing temperature. Because these are structural repairs affecting safety, with serious damage (especially around the keel, mast and shrouds) we strongly recommend consulting a yacht designer or having the work done at a professional yard.
Material prices — products and options
Indicative prices in EUR (incl. VAT), as of July 2026. Products widely available in Europe; prices depend on the shop, the pack size and consumption. The links lead to example shops that ship across the EU. Dollar amounts are converted at 1 EUR = 1.1622 USD (ECB, 7 September 2026) and rounded — treat them as a rough guide, not a price in a US shop. Imperial values in brackets are conversions of the metric figure.
Certified marine ply or foam core
- R&G — Okoumé marine ply BS 1088
certified ply for bulkheads, 4–18 mm (0.16 in–0.71 in) thick, price per sheet by thickness (indicative)€45–160 (≈$52–186) - Gerlinger — waterproof Okoumé/Sapele plywood
marine plywood cut to size, sheet depending on thickness (approximately)€40–150 (≈$46–174) - R&G / Airex — structural PVC foam (core)
foam core for laminated bulkheads and reinforcements, sheet by thickness (indicative)€30–120 (≈$35–139)
Epoxy resin with hardener
- West System — 105 + fast hardener 205, 1.2 kg (2.6 lb)
structural epoxy system for laminating and bonding bulkheads€73–90 (≈$85–105) - West System — 105 + slow hardener 206, 0.6 kg (1.3 lb)
slow hardener for larger laminates and higher temperatures, smaller pack€38–46 (≈$44–53) - West System — 105 + 205, 6 kg (13.2 lb) (large repairs)
pack for extensive tabbing and bulkhead replacement€240–290 (≈$279–337) - Yachtcare — 2K epoxy resin (budget)
cheaper laminating and bonding resin for less critical work€56–68 (≈$65–79) - West System — set of metering pumps
accurate resin:hardener dosing, accessory for the 105 system€26–34 (≈$30–40)
Glass cloths and tapes of various weights (for tabbing)
- Seatec — glass cloth 200 g (7 oz)/m²
light cloth for thin layers and finishing the tabbing, per m²€10–16 (≈$12–19) - Seatec — glass mat 300 g (11 oz)/m²
mat for building up the thickness of reinforcement laminate, per m²€7–14 (≈$8–16) - West System — 738 Episize biaxial cloth with mat (17 oz)
strong ±45° biaxial cloth for structural tabbing, price per m² (indicative)€18–30 (≈$21–35) - R&G — woven glass tape (for fillets and corners)
tapes 50–150 mm (1.97 in–5.91 in) wide for bulkhead-to-hull joints, per roll (indicative)€8–25 (≈$9–29)
Fillers (cabosil, microfibres), adhesives for fillets and bonding
- West System — 406 colloidal silica (cabosil)
thickener for bonding and fillets, controls slumping€16–22 (≈$19–26) - West System — 403 microfibres
fibrous filler for strong, flexible structural fillets€15–21 (≈$17–24) - Seatec — CS thickener (budget), 20 g (1 oz)
cheap silica for thickening resin on vertical surfaces and overhead€9–12 (≈$10–14) - Sika — Sikaflex 292i PU structural adhesive
flexible structural bonding of fittings and reinforcements, cartridge€18–24 (≈$21–28) - Sika — Sikaflex 291i PU sealant/adhesive
all-purpose bonding and sealing, 70 ml (2 fl oz) tube / 300 ml (10 fl oz) cartridge€8–20 (≈$9–23)
Tools: angle grinder, jigsaw, rollers
- Bosch Professional — GWS angle grinder 115/125 mm (4.92 in)
for removing old tabbing and keying the laminate (approximately)€55–120 (≈$64–139) - Makita — jigsaw
cutting plywood and bulkheads to a template (approximately)€80–170 (≈$93–198) - West System — epoxy resin roller
roller for wetting out and de-airing the laminate€6–9 (≈$7–10) - R&G — de-airing roller (aluminium)
ribbed metal roller for removing bubbles from laminate (indicative)€10–30 (≈$12–35)
Laminate moisture meter
- Trotec — material moisture meter (BM/T series)
detecting moisture in ply and bulkhead laminate (indicative)€40–150 (≈$46–174) - PCE Instruments — wood moisture meter PCE-WP/WM
moisture meter for marine ply and wooden bulkheads (indicative)€30–120 (≈$35–139)
Degreaser and materials for keying the substrate
- SVB — acetone 1 l (degreasing)
cleaning and degreasing laminate before bonding; the 6 l (1.6 US gal) version is cheaper per litre€5–36 (≈$6–42) - Yachtcare — Boat Cleaner (grease remover)
removes grease and dirt from surfaces before keying€15–19 (≈$17–22) - Mirka — Abranet abrasive mesh (keying)
mesh for keying laminate, pack of discs/strips (indicative)€10–30 (≈$12–35)
Safety gear: mask with an organic filter, coverall, gloves, goggles
- 3M — Comfort 4251+ half mask (A1P2 filter)
protection from epoxy resin fumes and solvents€33–42 (≈$38–49) - 3M — dust mask 9322+ (FFP2)
protection from glass dust when sanding laminate€7–12 (≈$8–14) - R&G — nitrile gloves, goggles, coverall
full protection for working with epoxy and glass fibre (indicative)€10–40 (≈$12–46)