O'Day 25 lost mast - SailNet Community

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Old 04-05-2010
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O'Day 25 lost mast

I'm helping a young man with his new boat a 1972 O'Day 25 that was dis-masted. Remarkably the only visible damage so far is:
1. Bent furling foil
2. Slight bend in mast step
3. Starboard chain plate pulled out.
4. Standing rigging has some kinks I don't like in it.

I'm pretty sure I'm telling him the right things but just to check.
The chain plate is a very small piece of stainless about 3/16 by 1.25 by 14" bolted to a 1/2" bulkhead tabbed to the hull and screwed to the headliner.

The plywood rotted of course and the chain plate pulled out dropping the rig.
Replacing the whole 1/2 bulkhead is probably more than he is willing to do what with the tabbing and such. I suspect that if his dad, with access to a machine shop, just made a much larger chain plate that would to down another foot to get into solid bulkhead we could just fit in a new piece of word for cosmetic purposes. I'm pretty sure it would be stronger that original.

I was thinking about sistering the bulkhead but then just a big enough piece of steel should be even stronger. Yes?
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Old 04-05-2010
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The problem with that idea is that the bulkhead is important in supporting the hull and cabin in resisting torsional loads as well as supporting the cabintop against both compressive and tension forces. If the bulkhead is rotted to that degree, then the entire integrity of the hull and cabintop is compromised IMHO.

The mast step pushes down on the cabintop in the center—the bulkhead may well be the part that transfers the loads from the cabintop down to the hull and keelson. If it is rotted, the addition of a larger chainplate does nothing to solve this problem.

The chainplates pull up and in on the bulkhead and if the bulkhead is rotted, the way the inward and upward forces are transferred to the hull will cause point loads that would be lessened were the bulkhead intact to spread the loads over a greater area of the cabintop.

Sistering the bulkhead is almost as much work as replacing it properly, and changes the alignment of the loads and where they are transferred.

Finally, as the loads generated by sailing cause the boat to twist, the bulkhead connects the cabintop to the hull and prevents any real movement of one in relation to the other. If the bulkhead is rotted, then there is nothing to help tie the two parts together and the cabintop may shift or warp under higher loads.
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Last edited by sailingdog; 04-05-2010 at 11:02 PM.
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