Shroud tension relaxed in cold weather?

[smokey73]

Just went to the boat today to move it to a slip for some winter work. Here in Beaufort SC we seldom get below freezing but the last few nights have been below 32.

While moving around on the deck I noticed that all my shrouds seem to have "loosed up" considerably since I last set the tension in accordance with the Selden Mast Tuning guidance.
They are not "flopping" around but are noticeably under less tension than when I last sailed. It has been down to sub freezing and will continue to be that way at night for the next few days.

Can the cold weather explain why all the shrouds would be looser? The only thing I can think if is a difference in thermal coefficient of expansion between the Aluminum mast (it "shriking" a few mm) and the 1X19 Stainless Steel shrouds not shrinking as much as the Aluminum mast? Any similar experiences or thoughts? I've never noticed this before? All you Minn and other cold weather sailors please let me know if your shrouds need adjustment for the cold weather? Thanks in advani

 

[smokey73]

Thinking about some other possibilities. I have swept back spreaders and if my fore stay has loosed, it would let the mast back a little and could loosen the shrouds? I'll check my mast step in case there is some problem there that would be letting the mast "sink" but I haven't noticed anything like that. Your ideas and experiences are welcome. I don't want to tighten them back up and then have them under too much tension.

 

[The Shadow Knows]

Smokey,
When it comes to metal, cold temps can change how your rigging feels.
Stainless 304 steel vs. stainless 316 (what I use) can feel different based on metallurgy & differing temps.
Being at a slip, I wouldn't worry too much about this however, if ever changing out your rigging especially using swage fitting & turnbuckles, I have found to never again use 304 vs. 316 S.S.

304 s.s. has much more carbon steel in the mix so, if you see a rust look in your swages, you have 303 s.s. fittings.
I myself over the years use only 316 s.s. for shrouds & also for my lifelines being coated or KNOT.

These are just my thoughts pal.....

 

[SG]

It is difficult to say because

i) The "base line" of your rig in the Summer isn't known. (It might on the lighter end, but work fine of tension for the way you sail.)
ii) The temperatures you're experiencing from, let's say 95° F to 32° F is a lot less than our friends in the Midwest US where the same "high temps" would exist, but the temp difference might by -30° F -- not quite double the difference. Of course, they would tend not to fixate on that in the upper Midwest during those times of the year, if they're roaming around their hulls. Further, they more often pull-their rigs in the winter.
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You have a stainless steel compression post on the Hunter 40.5, as I recall vaguely? As you suggest, I'd see if you note some sign at the deck, main cabin headliner/deck underside, and where it meets the hull/keel stringer system. It's a good idea to eyeball that anyway. If your have deal with it, better now than later.

I'm assuming that the feel or impression is a general one (i.e., all rigging)?

If you really torque your jib halyard down (NOT A GOOD IDEA), you can sometimes affect the trim of the back stay/fore stay. I doubt that's an issue, or your sail will be feeling sorry (and your sailing will be detrimentally affected by excess halyard tension, and your roller furling bearings and fittings will suffer, etc., etc.)

If the problems are bi lateral, the rig is "in column", etc. -- after you check the general support of the mast, then I'd not fixate on it. If now, unlike the Summer, your rig is not vertical. Then report back with some pictures looking up the mast.

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[Rick D]

I'd check with a rigger if you have one in the area who would be willing to give a professional, experienced opinion. Seems more a curiosity than an issue.

 

[smokey73]

Rick, it is a curiosity. I'll be at the boat Tuesday afternoon and working on it the rest of the week so I'll have a chance to really check things out. I don't think I have ever noticed it before so I'm thinking it may have something to do with the fore stay. I'll post more info after I get to the boat.

 

[chris mac]

Different aspect to your issue, but I install aluminum and steel soffit and fascia in Edmonton Alberta. Temp swing of roughly 70 degrees c over a calendar year.
There is a significant difference between the two on expansion or in this case contraction due to temp.
As I doubt you are sailing in the near freezing temps, I wouldn't stress about it. Keep an eye on it come spring.
It might be interesting to put a loos guage on now and in spring just to document the changes.

 

[markwbird]

The mast would get a little shorter in cold weather. More specifically, an aluminum mast that is 40ft tall would shrink about 7/16" going from 70 deg to 0 deg. That would cause the wires to loosen up some.. They were probably a bit loose to begin with to be that noticeable now.

 

[thinwater]

The difference (both would change similarly) would be on the order of 1/15th inch, depending on the assumptions made.

So yes, there would be a very small difference. But not enough to be obvious.

 

[Hayden Watson]

The difference in the coefficient of thermal expansion is 30% to 40% greater for aluminum than it is for SS. The stays will get a bit looser in very cold weather but the tension will return with warm weather. nothing to worry about.