Structural memory

[ScottUK]

I was wondering if a boat without a mast and standing rigging for an extended period would suffer from loss of structural memory. I realise some boats on the hard do have their masts removed for safety during winter storage but am thinking more long term. Thanks

[celenoglu]

If you are planning to keep the boat on the hard for a long period, it is a good idea to remove the mast and standing rigging. The tension on standing rigging might increase and elongate the rigging, which means you have to adjust when you are back in water. The oscilations on the rigging due to wind will not be absorbed as they were in water. This might further damage the rigging. It is best to remove the mast for long term storage. If you cannot do this you can decrease the tensions on the wires. This way the load on rigging will be much less.

[ScottUK]

I guess I am looking at it from the opposite end. If the standing rigging is elongated by the pressure would that not imply the gravitational force is working on both the bow and stern? If this is so would the form of the hull begin to have a reverse banana shape? Would not the same force have the same effect on the beam?

[celenoglu]

The rigging is intended to hold the mast, not the boat. Although it will have an affect on the boat on the dry, removing them should not affect boat integrity, but keeping the boat on the level with enough support should be considered.

[JohnRPollard]

Originally Posted by celenoglu

The rigging is intended to hold the mast, not the boat. Although it will have an affect on the boat on the dry, removing them should not affect boat integrity, but keeping the boat on the level with enough support should be considered.

That's right. If you're counting on the rigging to maintain the proper shape of the hull -- then you probably have a questionable design. If the hull were that flimsy, it would twist and distort in a seaway, even with the rigging in place.

It is possible for a hull to get some distortion when stored on the hard. A small amount is actually not unusual. You'll notice it sometimes when you try to close a cabin door and it doesn't quite align properly. This is also why procedures like engine/shaft alignment are done in the water, when the boat will resume its proper form.

You can also get too much hull distortion when the boat is hauled out and stored. But this is not caused by the rigging and mast being unstepped, it's generally from the hull being improperly supported. Many boats are designed to support most of the hull weight via the keel, with jackstands in place largely for balance. Others need to be supported by the stands, which then need to be placed under bulkheads or other reinforced areas to avoid distorting or deflecting the hull panels.

[ScottUK]

I was not implying the rigging was meant for structural support but that when on the hard it would help maintain the hull form whereas if a boat is left on the hard w/o the rigging the hull form would 'distort' over time and I would imagine over a certain period this could cause problems.

[JohnRPollard]

Originally Posted by ScottUK

I was not implying the rigging was meant for structural support but that when on the hard it would help maintain the hull form whereas if a boat is left on the hard w/o the rigging the hull form would 'distort' over time and I would imagine over a certain period this could cause problems.

Not really. I think you are conjuring a problem that doesn't exist.

It's widely accepted that for long term storage -- all things considered -- it's best to take the rig down. Issues relating to hull distortion do not even make the list of pros/cons when considering whether to drop the mast or not.

There are plenty of boats in long-term storage. Search around and see if you can find a rash of reports about hull distortion problems that are attributed to unstepping the rig.

The only significant issues I've ever heard of were caused by improper blocking of the keel or improper placement of jackstands/cradles/trailer bunks. These can occur with or without the rig in place.

[mitiempo]

If you took the string off a bow (as in bow and arrow) the bow would straighten out a bit. In other words the bow depends on the string for it's designed shape. A boat does not depend on its rigging to keep the bow and stern in the proper place. The boat is designed and built to be stiff enough with the rig in place that it doesn't distort very much with normal rig tension. Removing the rig is not a problem and for long term dry storage the rig should be removed.
Brian