Rigging Size

[ksmith]

Back again.
My standing rigging appears to be 5/32, however when looking at the various types of swageless I noticed I could move up to 3/16 with the same size pins.

Anything wrong with this Idea.

[SkiprJohn]

I don't know what kind of boat you have but unless you are going world cruising and don't care about going fast I wouldn't move up in rigging size unless you think it is way too light.
JohnL

[Weyalan]

The guy who designed your boat will have spec'ed your standing rigging to suit the load calculations around which the rig was designed. If you want to get any benefit from stonger standing rigging you would probably need to replace your chain plates and, possibly, your mast as well. Bear in mind, also, that the larger diameter steel cable will be heavier and that extra weight up high has a big penalty on stability.

That isn't to say that you wouldn't benefit from the upgrade, just that bigger isn't necessarily better.

[Sandero]

I don't think going up one size will mean a heavier mast and it may not even mean larger chain plates. Larger wire means it is operating at a lower end of its safe working load. It doesn't mean that the load is increasing.

Suppose you did a calculation for a steel beam and the computed size was W10x45. You could substiture a larger steel beam. If the loads are not changed in that case you would have less deflection.

Same with rigging. The main concern might be weight aloft which again is rather small difference when compared to the safety factor.

Who says size doesn't matter?

jef
sv shiva

[Weyalan]

I hear what you are saying, Jef. The point I was making was merely that having stronger standing rigging might not make your system stronger if the standing rigging was not the weakest link in the system to begin with...

[Sandero]

The odd thing is that many sailors fair to consider how the force of the wind actually moves the boat when sailing. We know it comes from the wind and we trim sails to optimize sail shape but the forces on the sails are all translated first to the edges of the sail where it connects to the boat - mast, boom and headstay and halyards and sheets, vangs, preventers, poles. All these are loaded up from wind pressure.

But there is all the system that supports the rig... the mast step, and the standing rigging, which includes the chain plates.

It's all a great big vector diagram. The vertical loads are not moving your forward, the weight of the rig, but the components of the vectors point forward are what does it. Although the forces may seem very large because a boat is pretty heavy, it doesn't take all that much to move a slippery shape through the water. The key thing to understand is all the forces to propel a sailboat are operating at the main points of attachment of the rig... mast, standing rigging and sheets... hardware blocks and winches.

One can see why the chainplates must be strong and well anchored because it is through them that most of the forces pass.

jef
sv shiva

[GordMay]

An interesting and informative discussion of rigging loads at:
Sail Loading on Rig, Rig Loading on Vessel - Boat Design Forums

[ksmith]

All great advice.

A little more information. My boat is a Macgregor 25 (sail boat not motor sailor). Thought it would be a great boat to learn on (price was right).

On Saturday the forestay let go. The break occurred at a nicopress the PO had used for the furlling system. So as some indicated the connections are just as important as size of the wire.

My thoughts about wire size were if the pins stay the same and the wire is increased by 1/32, which according to the charts I have seen give a lot more strenght why not. Of course the whole system has to work together so my plan was to change all the rigging including turnbuckles and connection points. I planned on using either norseman or sta-lok fittings. Of course my schedule has moved up some now.

[SkiprJohn]

Aloha ksmith,
You are making a good decision. I always thought the macs were a bit on the light side for rigging. I'm not certain you need new turnbuckles but of course you know what you need. I would go sta-lok instead of norseman. They seem to have fared better in the testing by practical sailor.
JohnL

[SkiprJohn]

Aloha ksmith,
You are making a good decision. I always thought the macs were a bit on the light side for rigging. I'm not certain you need new turnbuckles but of course you know what you need. I would go sta-lok instead of norseman. They seem to have fared better in the testing by practical sailor.
JohnL

[ksmith]

SkipJohn

Thank for the input. Mac's are a very light boat indeed but all the basics are there. My goal is to aquire experience then move on to a move substantial boat. Though it will have to be trailerable.

I will take closer look at the turnbuckles not much can go wrong with them. Though the terminals are bent.