Repairing Leaks On A Vintage Plywood Boat

Repairing leaks on a 1957 Trogen plywood boat can be a challenging task, but with the right approach, it is certainly achievable. The first step is to identify the source of the leak, which may be due to damage caused by a collision or gradual deterioration over time. Once the leak is located, the affected area must be dried and cleaned. This includes removing any old sealant, grease, or oil that could interfere with the repair process. The next step is to cut out the damaged plywood, ensuring that the cut follows straight lines to make it easier to create a replacement patch. It is also crucial to avoid damaging any frames, stringers, or bulkheads during this process. After cutting out the rot, the edges of the hole should be sanded, and the surrounding wood may need to be treated to prevent further rot. The final step is to create a patch of the same thickness as the original plywood, following the template of the cut-out area. This patch can then be glued and clamped into place, or fastened with screws if clamping is not feasible.

Identify the source of the leak

Identifying the source of a leak in a 1957 Trojan plywood boat is crucial to performing effective repairs. Here are some detailed, direct, and instructive guidelines to help you in this process:

Initial Checks:

• Taste Test: Start by tasting the water leaking into the boat. If it's salty, it's likely a leak from below the waterline. If it's fresh water, the source is probably above the waterline.
• Sailing Conditions: Consider the weather conditions and how you've been using the boat. Rainwater leaks are distinct from leaks that occur when the boat is submerged in heavy weather.

Above the Waterline:

• Water Tanks: Check for leaks in the freshwater tank, as issues with hoses, taps, or seacocks can lead to water in the bilges.
• Windows: Older boats often have leaks around windows. Test these with a hose or bucket of water. Tighten fixings or consider resealing with products like Captain Tolley's Creeping Crack Cure.
• Wire Pass-Throughs: Check for leaks where wires pass through the deck. Common issues include worn-out rubber gaskets or wires that are too small for the gland.
• Hull-Deck Joint: Inspect the area where the hull meets the deck, especially if the boat has sustained damage. Use a hose to check for leaks, but be prepared to move built-in furniture or lockers.
• Chain Plates: Remove and check chain plates, especially if they're bolted to wooden bulkheads, as these can rot and weaken. Look for water ingress and blackened timber.
• Deck Fittings: If you've been sailing in heavy weather, suspect all deck fittings. Stanchion bases, jib tracks, winch bases, and toerails can all be potential sources of leaks.
• Steering Pedestal: On wheel-steered boats, the steering pedestal is subject to large loads and can leak. Test with a hose and apply pressure to the top to check for movement at the base.
• Engine Control Cables: Don't forget to inspect engine control cables where they pass through the deck.
• Hatches and Vents: Check deck hatches for warping or damaged seals. Test with a hose, paying attention to hinges and handles. For vents, strip the stainless ring and inspect the internals for damage.
• Keel-Stepped Mast: If water is running down the mast and into the bilge, check the mast boot, drain holes, and the mast track. The plug inside the mast may be leaking, requiring further investigation.

Below the Waterline:

• Engine Water Pumps: Seals and metal components in engine water pumps can wear over time, causing leaks. Place a bucket under the pump or observe it with the engine running to isolate the issue.
• Stern Gland: Traditional stuffing-box glands should drip about once per minute. If there's a larger influx of water, the compression nut may need tightening or the gland may need repacking.
• Rudder Posts: Similar to stuffing boxes, rudder posts can leak, especially if they haven't been repacked recently. Check for leaks and damage, especially when moving the helm.
• Cockpit Drain Hoses: If a significant amount of water has entered the boat, check cockpit drain hoses for holes or detachment.
• Hull Integrity: In rare cases, there may be a hole or crack in the hull. Trace the water to its source and keep a record of when the leak occurs (e.g., after sailing on a particular tack).

General Tips:

• Hose Test: Use a hose to squirt water over deck fittings and other suspected areas. This can help identify the source of the leak.
• Colored Water: Use different colored waters at various locations. If blue water ends up in the bilge, for example, you've found the leaky fitting.
• Isolation: Isolate individual fittings with plasticine or Blu-Tack to pinpoint the source of the leak.
• Pressurisation: Pressurise the inside of the boat by taping up gaps and using a leaf blower. Then, go around suspect fittings with soapy water to detect air escaping.
• Powder and Tissue Paper: Dust talcum powder or use tissue paper underneath fittings to track the path of slow leaks.

Cut out the rot

Before you cut out the rot, you need to identify the type of rot and the extent of the damage. There are two main types of rot: wet rot, which grows when unprotected timber is in constant contact with moisture, and dry rot, which occurs when the unprotected timber has been repeatedly wetted and dried out.

Once you've identified the type of rot, you can begin the repair process. The first step is to cut away all the damaged plywood. It is easier to cut from the outside of the hull, so you will need to mark the positions of any frames, stringers, and bulkheads on the surface. From the inside, drill a few fine holes along the framing so that they can be seen from the outside, then draw a line to join them up. This will ensure that you don't cut through or damage any of the boat's structures.

Use a skilsaw or router with the depth set to the hull thickness to cut out the rot. If the boat has been fiberglassed, you will need to use a carbide bit in the router. Cut along straight lines, as this will make it easier to cut a replacement patch. A square or rectangular patch is also easier to cut and replace.

Once the damaged plywood has been removed, you will need to treat the surrounding wood to kill off any stray rot spores. This can be done using a fungicide or a borate solution.

After the area has been treated, you can begin preparing the wood for the patch. Use a saw blade turned on its side to scrape gashes into the wood, creating a good mechanical bond. Sand the wood to ensure that everything is smooth and true. If any of the wood has been contaminated with oil or grease, it will need to be thoroughly degreased. Warming the wood may help bring the oil to the surface, and fine sawdust can help to absorb it.

The next step is to create a patch. The patch should be the same thickness as the original plywood and should fit the hole in the hull perfectly, lying flush with the surface. If you are replacing a large area, you may need to laminate the patch using several layers of thinner ply to build up the desired thickness.

Before installing the patch, seal both the patch and the surrounding wood with epoxy. Use masking tape to make clean-up easier. If you are unable to access the area from the inside, you will need to use through-fasteners to hold the patch in place while the epoxy cures.

Once the epoxy has set, you can begin fairing, finishing, and glassing. If the area you are repairing is curved, you may need to use temporary battens/frames to shape the patch.

Prepare the wood

Before gluing in a patch, the wood will require proper preparation. If the wood has been contaminated with oil or grease, it will need to be thoroughly degreased. If the oil has soaked in, it will require repeated washing with a degreaser and solvent over a long period to allow the oil to come to the surface. Warming the wood may help bring the oil to the surface, and fine sawdust will help to absorb it. It will take time for all the oil to come out before the wood can be successfully glued.

If the damage was caused by rot, you might want to consider treating the surrounding wood to kill off any stray rot spores. A belt sander will get rid of most of the glue on the exposed frames and tidy up any edges. A saw blade turned on its side can be used to scrape gashes into the wood to help create a good mechanical bond. It may be time to get out your right-angle sander/grinder with some 24 grit and take everything back to bare wood. Then reseal all the wood with epoxy.

If you are replacing large areas on a small boat, the boat will need checking for any twist before gluing up. This can be done by using a straight edge and eyeballing to make sure everything is true.

The repair plywood patch should be the same thickness as the original plywood. Make a template of the cut-out as a pattern for the patch. Cut out the patch so that it fits the hole in the hull perfectly and lies flush with the surface of the hull.

Before assembly, the patch and backing blocks should be given several sealing coats of epoxy. In the case of a small patch, this could be a backing plate larger than the patch with a good overlap.

Insert a repair patch

Repairing a plywood boat is a fairly easy process. The first step is to identify and cut away all the damaged plywood. Mark and cut the damaged area along straight lines, as this will make it easier to cut a replacement patch. The shape of the cutout doesn't matter, but a square or rectangle will be easier to work with.

Once the damaged area has been cut out, you will need to prepare the wood for gluing. Use a saw blade turned on its side to scrape gashes into the wood, creating a good mechanical bond. You may also need to use a sander to ensure that the surface is smooth and ready for gluing. If any of the wood has been contaminated with oil or grease, it will need to be thoroughly degreased. This process may take some time, as you will need to remove all traces of oil before gluing.

The repair patch should be made from the same type of plywood as the original and should be the same thickness. Cut the patch to fit the hole in the hull perfectly, and bevel the edges of the patch to match the bevel on the opening. Dry fit the patch to ensure that it sits just slightly below the existing surface.

Before bonding the patch, wet out the bonding area with a resin/hardener mixture, recoating the end grain as necessary. The plywood will absorb a lot of epoxy, so be sure to use enough to create a strong bond. Apply a mixture of epoxy and thickener to the bonding area, then clamp the patch into place with temporary staples or screws. Clean up any excess epoxy before it cures.

Once the epoxy has cured, remove the clamps and add a final layer of epoxy/filler. Sand the surface carefully, then use a spreader to fill low areas with an epoxy/low-density filler mixture. Allow the mixture to cure before fairing and finishing.

Seal and finish

Once you have cut out and replaced the plywood on your 1957 Trojan boat, it is time to seal and finish the wood.

Sealant Options

There are several options for sealing marine plywood. One option is to use clear, penetrating epoxy. This type of sealant works its way deep into the wood, dries transparent, and requires less maintenance than other types of sealants. Another option is to use a marine-grade sealer, but this will require more coats and must be reapplied every 3 to 4 years. A third option is to use a two-part marine-grade epoxy resin.

Sealing Process

Before sealing, wipe down the surface of the wood with acetone to remove any grease or stains. Allow the acetone to dry completely before moving on to the next step.

Next, sand both sides of the wood, including the edges, with 80-grit sandpaper. Wipe away all dust and particles with a soft cloth.

When you are ready to apply the sealant, start with the top and side edges of the wood, moving to the front face. Allow the sealant to dry completely before flipping it over and applying it to the bottom edge and back.

If you are using marine plywood, it is thicker than typical plywood, so you will need to apply more coats to maximize its lifespan. A good rule of thumb is to add as many coats of sealant as there are layers of plywood. For example, if your plywood has 7 layers of wood, you should add 7 layers of sealant. Gently scuff up the wood with sandpaper between each coat for maximum adhesion, and be sure to wipe off any dust before adding the next layer.

Finishing

Once the sealing process is complete, you can finish the wood as desired. This may include painting, varnishing, or carpeting, depending on the specific needs and preferences of your boat.

Frequently asked questions