Monday, 10 October 2022

Shorter days

Apologies for the lack of blog posts about Bonita recently. There are two reasons for this - firstly that we havn't been very adventurous recently - just day sails from the Swale. A greater worry however is some IT difficulties with the blog. Unlike on the boat, the application of common sense and traditional skills dont seem to sort out the problems. Skilled IT help may be needed..... There are still some good sailing days after the equinox, but inevitably as the season comes to an end thoughts go to planning the work for the winter. This summer I began to worry about the keelbolts. Bonitas lead keel is held on with six bolts, each 7/8 inch diameter (22mm) and 20 inches long. Originally these bolts were of wrought iron. This is a marvellous material, not as strong as steel, but much more resistant to corrosion - the SS Great Britain was built of wrought iron in 1845 and much of the original structure still survives today despite decades of neglect before she was rescued. The wrought iron fastenings - probably of bog iron- are the only bits of the seventh century Sutton Hoo ship that have survived. Unfortunately wrought iron is almost impossible to obtain now, and people who claim to be able to supply wrought iron may well turn out to be selling something different. We think that Bonitas original keel bolts lasted until my father got them replaced in 1968. By then the 7/8 inch bolts had decayed to less than pencil thickness in their mid sections, so the job did need doing. The 1968 bolts I then replaced in 2003 with material that was sold to me as wrought iron. Over the summer however there has been a leak and ominous rust stain from around one of the bolts.
The picture shows the bilge with a floorboard lifted. The black patch is pitch that was poured over the nut and threaded end of a keel bolt. The rust stain has only appeared in the last few months and there is a slow trickle of water. The leak is only about a bucket-full a week, but its more than there used to be and clearly all is not well. The plan is to have the boat lifted out this winter, remove the bolt and have a look at it. They may all need to be renewed. And with what? Real wrought iron is even harder to get now than it was in 2003. Stainless steel might seem the obvious choice, but it is prone to unpredictable corrosion in the absence of oxygen. I suspect the best answer will be to use galvanised mild steel, and accept that the days when keel bolts could last 80 years without giving any trouble are probably gone for good.


  1. Wrought iron appears to still be available re-rolled from mooring chain: -

    The price per foot seems reasonable: -

  2. Thanks Kevin, they do sound genuine. It maybe that I only have one duff bolt and all the rest are fine. We shall see.. I suppose the logical thing to do would be to get wrought iron bolts galvanised for the maximum life. I do try to replace like with like whenever its realistic to do so.
    Best wishes