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Thank you David !
When you write "expoxy-timber", you mean "epoxy impregnated plywood without fiberglass" ? ----- Mail original ----- De: "David Mancebo via groups.io" <mancebodesigns@...> ?: [email protected] Envoy¨¦: Jeudi 26 Novembre 2020 16:45:20 Objet: Re: [K-Designs-Multihull-Sailboats] DUO 900 Question Thanks for the answer to my question Bernd. It has been my experience that limber holes are needed for bilge water to drain to the lowest point in each compartment so it can be easily removed. I worked as a Shipwright building timber monohulls from 1973 to 1981 and have seen the condition of many of them after all these years. The epoxy/timber boats with good ventilation have had the longest life. Some of them look almost new on the inside after 45-years. One common problem I have seen on the boats with poor ventilation is mildew on the inside surfaces. The boats with good ventilation did not generally have this problem. The main way we installed adequate ventilation was to ensure each compartment had at least two openings (ventilators or hatches) to the outside of the hull. Lockers and cabinets also need at least 2 openings for adequate airflow to the inside of the hull to stop condensation and mildew. When faced with watertight bulkheads, we installed a low inspection port and a deck ventilator or hatch to induce air flow through the compartment. Both the inspection port and the ventilator would normally be closed when underway to provide watertight integrity. Over the long life of these boats, epoxy slowly absorbed water. I know this because of the slight discoloration of the timber under the epoxy where bilge water was left. By inducing good ventilation, bilge water evaporates and there is minimal absorbtion of water into the epoxy. Dry wood is stronger and less likely to rot. Here is a real-life example of the situation. One boat I built in 1977 of cold molded Western Redcedar, okoume plywood and Sitka spruce was sweet smelling with zero rot or mildew until it suddenly began having problems after 27-years. Mildew damaged the inside paint and there were a few small areas of rot in 2 deck beams and a small area of plywood decking. All of these problems were in the forward 1/3 of the hull. The problem developed because the owner closed off the forward cowl ventilator and kept the forward hatch closed tight when moored. The two aft ventilators and companionway vent kept the after portion of the boat in good condition. Closing off all ventilation forward caused the problem. After repairs, the owner keeps the ventilation open forward when moored. 16-years later, he has not had any more problems. |
