I discovered that the corrosion in the under-deck backing plate for the stern chainplate on Avy-J was far more advanced than I thought, and it became obvious it would be necessary to build a new chainplate. The raked transom (raked at about 45 degrees) means that this is not as easy as it might be on a flat transom.
The existing arrangement (shown below) has the transom plate embedded in the hull, connected to the top (deck) backing plate with the transom plate and the deck plate triangulated by two struts of metal. You can get the general idea from the diagram below (not to scale)
- Dig out the existing structure and replace it with like for like. Incredibly difficult job working in the confined space of the lazarette.
- Dig out the existing structure and make a standard chainplate on the transom with backing plate – the owner of this site has this type of chainplate (see right). The alternative would be to bolt through the embedded plate in the transom, but of course I had no way of knowing how sound this was.
- Design another solution that would allow me to leave the existing structure in place and not have to bolt through it.
In the end I put my head together with a friend and we came up with this design – a wide rectangular plate tapering to couple of inches wide at the top, bent to the appropriate angle (to line up with the masthead) where the dotted line is. Material is 6mm stainless. This way it can be bolted through either side of the embedded metal with two separate backing plates, no need to cut anything out.
The tricky bit was getting the slight curve of the transom in the plate, and the even trickier bit was curving the top (at the dotted line) in a different plane to the transom curve. I took the project to a very capable local stainless steel fabricator, who said the only way to marry the two curves together was to make it in two separate pieces and weld them.
(This guy is brilliant, but I can’t give you his name as he would have to kill me – he has far too much work, for better paying customers than impoverished yachties)
The plate came back beautifully finished. The only difficulty was getting the top bolts in as they were very close to the hull/deck join. I had to remove a couple of the rubrail bolts to get the backing plates, in, and these had to be cut down so the top hole was right at the top.
Have a look at the end result – strong and handsome . . . .