Blocking Problems on Older Cruiser

10 Oct

Interesting case a little while ago of a late 70’s 34 foot cruiser which was up on stands for a season or two. The hull was supported at three points: The aft corners on the chines and forward just aft of the stem. As can be seen in the photo, the surface of the block supporting the front was too small and eventually the blocks passed right through the hull. 

I think there are a couple of interesting things here. 1- The yard assumed that the structure was designed to handle a point load as is the case on most modern cruisers, but this vessel only has the hull shell to support the load. No keel or back bone and no local reinforcement. 2- The hull is made with a balsa core which delaminated long ago. So the already weakened structure did not stand a chance.

Although there are two 6×6 timbers below the keel, there was in fact only one at the time of the collapse. Note to owners of older cruisers: make sure the hull is supported on a sufficient number of blocks so the pressure on the shell is minimized.

 

Image

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