wiggsteve wrote:...would like to know if anyone agrees whether the loose compression post casting caused the mast hinge to buckle.
The picture you shared shows two twisted halves of a tabernacle, loosely connected by a pin on the forward starboard side. The pin is inserted into only the starboard hole on each half, and given the twist of the halves, it doesn't look like the parts could even be maneuvered so that the pin goes through two sets of holes, one on either side.
Taken together with the fact that the parts are twisted as if someone had pulled on each of the holes connected by the pin, it looks like the pin slipped out of one side, so on that side the hinge could open, but only by twisting the other side that still had the pin in it.
The background in the image is a bit confusing, part of the view seems to show beach, but part seems to show a wooden board, where I would have expected to see more deck. On the bottom left, it looks like a view of the mast partners (deck opening), with aft to the left, and the bottom of the mast in its normal position.
That means, that the pin shown is the forward pin, meaning your mast fell backwards. We don't see the aft pin as it is just out of the frame, but because the two halves come together normally towards the edge of the image, I would assume that the aft pin is inserted normally. We cannot see the other pair of holes that the port end of the forward pin should have been inserted in, nor can we see that end of the pin. So we cannot see whether it lacked a cotter pin or what else allowed it pop out of those portside holes.
It is my understanding that the tabernacle is not designed to hold the mast up by itself. There's too much leverage. However, as long as the shrouds and the forestay are holding the mast vertical, the rear pin should have been enough to keep the bottom of the mast in place.
In raising a deck-stepped mast, there's often some other line that temporarily takes the role of the forestay. You did not tell us at what stage your mast came down. In order for it to fall backwards, the line or forestay holding it must have come loose (or missing). At that point, the full leverage of the mast is on the tabernacle and if the forward pin has no cotter pin or split ring on its port side, it could slip free from the port side of the tabernacle.
At that point, the asymmetric load will bend the tabernacle, the mast will start to move and no longer being close to vertical, the bending moment due to gravity will increase. As much as a remote diagnosis can never be perfect, that is what I can read from the picture.
It's my experience that the mast partners are a tight fit for the bottom of the mast. It is not possible to shift the mast foot more than a few inches from its normal position. (I have a keel stepped mast, so I insert the whole mast through the partners, and I know if I don't line it up almost perfectly, I can't get it to go in.)
I'm not sure whether the "wiggle" from a loose mast foot was a contributing factor for the pin to pop out of the port side of the tabernacle. Possibly. But the mast would not have come down unless the forestay was loose or not connected. One of the boats I owned had a desk stepped mast that did not have a hinge, but was set into a slot (about an inch deep) that was simply designed to keep the mast foot from slipping sideways. We used the spinnaker halyard as a makeshift forestay with that boat because it had a furler which took over the function of the forestay, and therefore required the jib to be set.
As long as your mast can't jump off the tabernacle (and for that the rear pin would suffice) the shrouds and forestay should have been enough to keep it up.
Hope that gives you some useful information for your repair decisions and also how to avoid this happening again.
