Well we finally got to a place suitable to be able to remove the masts and carry out the repairs so I thought I should do an update.
Main Mast Compression Post - The main mast defiantly had rot, and that had also caused some rot to the bulkhead. A previous owner had done a pretty good job of trying to replace the bulkhead from the saloon side, but without access to the area under the floor from the head side he could only do so much.
Tried removing the floor pan in the head but ended up having to cut the floor out. Upon cutting out the floor pan we also discovered that the glassed in copper pipe had corroded.
The post was then replaced with new hardwood.
I did consider going for a stainless post, but as good hardwood was available decided to stick with that. We then re-glassed the post in at the bottom and top. Floor was repaired and new gelcoat put on. The head is not quite back together yet but will post a finished photo when it is.
Why did this happen? Well I guess it is a 30+ year old boat so somethings like this are bound to occur, however I think the main reason is that freshwater had got in-between the wall lining and the shower floor. The glass did not come up this high. I will be sealing this joint and ensuring that the mast drain has a tube in it so that any water from there also runs straight into the floor drain. I also found that the
Mizzen Mast - Under the mizzen mast base plate we found that there was a wooden block encapsulated in the fibreglass. This was rotten, causing the area to sink and pushing the top of the seat up in the middle. The rope box had come away from the bulkhead the same way as yours had Peter.
When this was cut out it was also discovered that the balsa core to the seat was rotten. The rope box was cut out and saved for reuse. The seat gap was filled as best as possible with resin and chopshred. The base under the mizzen was then built up from the bottom layer with epoxy and high quality glass.
Why did this happen? I am not sure, but I think that the issue occurred because additional holes where put into the box area for running solar panel cables. These would have been sealed at the time, but I guess over the years it leaked and led to rot. Once the rot to the block started to collapse it it meant that the water could also get in next to the conduit that takes the mizzen mast cables.
Will post photos soon.