Last winter while I was building the 18′ Faering and the 8′ Punt I was also slowing repairing a beautiful 30′ Swedish Launch from the 1930s. When the owner contacted me he said that the boat had suffered some damage from a grounding.
Well there was certainly damage from a grounding the rudder and its attendant gear were bent over to port. More interesting was the vertical crack in the transom. It is very unusual way for the wood to break and I was worried that it could mean rot in the transom area.
After opening up the boat it became fairly quickly apparent that the culprit for the weakening of the wood wasn’t rot. This was a good thing as it meant the problem could be easily contained. The reason for the loss of strength was electrolysis caused by the locating of galvanised bolts close to the bronze rudder tube. Over time water had gotten in the joints in this area and created an electrical circuit between the two different metals. This produces chemicals which break down the lignin (the glue that holds wood together) and leaves just the unconnected fibres. You can see above the characteristic black in centre of the horn timber above.
The easiest way to repair this was to remove the entire horn timber and make a new one. The old galvanised bolts were replaced with silicon bronze so hopefully there won’t be repeat of the problem. In the upper left of the photo above is a vertical pipe that I’m not sure of its function. It connects the red tube in the photo that has a strainer at the end and the vertical pipe ends outside the hull with a T section. I ‘d be delighted if some reader could enlighten me. I’m guessing it could be a self bailer of some kind but stand to be corrected.
Roeboats, Ballydehob, Co. Cork, t:+353 (0)28 38973 m: +353 (0)86 158 69 37 e:firstname.lastname@example.org