Sagging spreader, is that a symptom of something sinister

[MidLandOne]

Originally Posted by GreatKetch

REMEMBER ALL: Internet based advice is worth exactly what you pay for it! Ignore the rules of physics at your cost!

I'll give the poster the benefit of the doubt, and assume that they are thinking of lower spreaders on multispreader rigs. The angles these spreaders make is more complex and they are frequently horizontal, or close to it. Of course if he had actually read the comments, nobody talked about spreaders "flopping out" of their attachment to the shrouds, what was discussed was spreaders shifteing vertical alignment. Remember, just because that's the way YOUR boat was built, does NOT mean it is the right way!

Spreaders are COMPRESSSION members. If you don't understand what that means, then you aren't qualified to comment. You ARE 100% qualified to ask questions, however. Understand that on a forum like this you are going to get multiple answers, including answers from people who don't understand rigging. So you still have to sort out the right answers. So you might not actually be better off than you started.

Oh dear . Also seems you didn't read my post fully.

If you go and look at some modern well rigged boats you will find that frequently (probably more often than not) all spreaders on the mast are at the same angle from the mast (usually horizontal or very close to it - the dihedral of 5 degrees in the picture GordMay posted is common) and the spreaders shorten as they are higher. The shortening of the higher spreaders may, or may not result in exact bisection of the shroud angles depending on the spreader lengths and the chainplate base. It is not necessarily practiced on many rigs to tip the upper spreaders up to a differing dihedral to the lower spreaders as an adjustment to get an exact bisection of the shroud angle although by nature of the upper spreader being shorter than those below it may be close to it - in fact if the spreader is on solid through bars or other means with similar fixity then one cannot adjust it up.

Of course, if there are intermediates then their angle is never bisected by the spreaders and the rig survives regardless, even though the inners may be highly loaded.

It is not universal practice to need to wire the outer ends of spreaders to prevent vertical movement of the outer end against the shroud, particularly with spreaders with through bars and those are common. In such cases though if the shroud happens to be articulated at the spreader then it may end up locked to the spreader bar but that only because one of the articulation clevis pins happens to go through the spreader.

It can be said though if one spreader on one side of the mast is at a different angle to its mate then there is a problem and that is what the original poster asked about. He also asks if they are all loose to some degree before the rig is tightened - the answer is no they are not neccessarily so but may be, it depends on how they are fixed at the mast. If they are on through bars or are similarly rigidly fixed, for example, they should not be loose before the rig is tightened unless something has come adrift.

Enough from me on this

[Seasick Steve]

On a slightly different tack (as it were) when I restep my mast next month, how do I actually get the spreaders into the right position? It's a Westerly Centaur with a single (cap) shroud to each spreader. As I see it the options are:
1. Stick them in the sockets horizontally with sealant, as they were originally, and put up with the incorrect angle (as has haoppened for the last 42 years)
2. Find out the correct angle (by measuring other boats' rigs or asking you lot and stick them with sealant as above
3. Fill the sockets with sealant immediately before raising the mast and adjusting the spreaders with a long boathook or similar after the shrouds are tightened but before the sealant sets.
None of these seem very satisfactory - anyone got any better ideas?

[skipmac]

Originally Posted by Seasick Steve

On a slightly different tack (as it were) when I restep my mast next month, how do I actually get the spreaders into the right position? It's a Westerly Centaur with a single (cap) shroud to each spreader. As I see it the options are:
1. Stick them in the sockets horizontally with sealant, as they were originally, and put up with the incorrect angle (as has haoppened for the last 42 years)
2. Find out the correct angle (by measuring other boats' rigs or asking you lot and stick them with sealant as above
3. Fill the sockets with sealant immediately before raising the mast and adjusting the spreaders with a long boathook or similar after the shrouds are tightened but before the sealant sets.
None of these seem very satisfactory - anyone got any better ideas?

My technique is to eyeball the angle. I don't think being off a degree or three will destroy the rig or crash the mast. So when you step the mast, get hoisted up, manually raise the spreader until it forms equal angles above and below with the shroud and install a small SS u-bolt under the spreader to keep it from drooping back down. Of course put the legs and nuts of the u-bolt pointing in so they don't' catch on the jib and make a hole.

[s/v Jedi]

Correct, the angle between spreader and shroud must be equal above and below the spreader. Most don't get that right incl. new yachts so I assume they design it for aestatics with stronger spreaders?

[Suijin]

Yes the spreader tip angle should bisect the overall angle above and below, for the spreader to be subject only to compression loads. And yes there are boats where this is not the case and they were not designed for that to be the case. I'm staring out a port light right now at a 100'+ Royal Huisman where the top (of four) spreader pair clearly does not bisect the angle.

In reality, if a spreader does not evenly bisect the angle by say a few degrees either way, the side loads on it are not appreciable, given the work the other stays are doing. But if you're in a position to adjust the the spreaders you might as well have them bisect the angle as closely as possible.

[Seasick Steve]

@ Skipmac

Ta. But that involves going up the mast, which I'd rather avoid. Still, I might be able to get her alongside a wall.

I suppose a lashing with tarred marline or similar would be more authentic and less likely to cause damage. Also less likely to last I suppose

[skipmac]

Originally Posted by Seasick Steve

@ Skipmac

Ta. But that involves going up the mast, which I'd rather avoid. Still, I might be able to get her alongside a wall.

I suppose a lashing with tarred marline or similar would be more authentic and less likely to cause damage. Also less likely to last I suppose

Oh, just noticed you have a 26' boat. How much ballast in your Westerly? How much ballast in you? I might wonder about the stability of a smaller boat with a big guy at the top of the mast.

I may be overly paranoid on this subject but I try to avoid anything on SS that might trap moisture against the metal like wrapping the wire with tarred line. SS if kept wet and in a way that traps the same moisture on the part can promote crevice corrosion.

[UNCIVILIZED]

Often enough, when seizing the spreader tips in place on the shrouds, you first want to wrap the shroud with a couple of wraps of friction tape (or similar) around the shroud where it'll meet the spreader. This is to allow the seizing to get a much better grip on the shroud. As rigging wire is often fairly hard to seize things to otherwise. Just as it's difficult to grasp it firmly enough with your hands in order to resist it slipping in your grip under any significant loads. Such as if you wanted to free climb the rig via going up the shrouds (which, yes, it's possible to do this).

You want to seize things firmly enough so that the tips don't move, period. Even to include if you stand on them with your full weight while up the rig. Which, seizing them this tightly, means that sometime you have to go up the rig to change their position slightly, & redo the seizing. Since the tips don't slide up or down well once seized. This usually is best done after you put a small amount of tension onto the shrouds via the turnbuckles (rigging screws).

It's good practice to go aloft in order to check the rig a couple of times after tuning both the spreaders & stays. Typically once right after the mast has been stepped, & recieved a preliminary tuning. And then again after a couple of times under sail in a stiff breeze. As things will move slightly during such sea trials. To even include small but important details having been missed when the rig was initially stepped, or that part X, or Y is now trying to work it's way loose. And that the only way to see such things is to go up there yourself.

Also, there are a huge number of ways that spreader tips can be configured. Ditto on the plethora of hardware bits that may or may not be incorporated into a spreader's tip. And the same is true of how things are configured at the spreader's root, where it meets the mast. To include the use of spreader bars or not, etc. Along with another slew of options (yet again) for shroud attachment designs & their hardware at or near spreader bases.


Edit: In order to get the angles equal on a spreader's top & bottom sides where it meets the shroud, you can use an adjustable bevel gauge. And it's common sense, but if a spreader on one side of the mast is a lot floppier than it's adjacent twin. Or at a grossly different angle, etc. Then it's worth taking a hard look at all of it's attachment hardware for uneven wear & the like. Doing so on both ends, & it applicable, to the spreader bar, & or socket(s) as well.

[Seasick Steve]

The boat's a bilge keeler displacing about 3.5 tons of which about 40% is the cast iron of the keels. They have a reputation for solidity and stabilty - and If I go up I'd probably do it near LW when she'll be sitting in the mud anyway. I displace about 12 stone. (70-odd kg in new money) so unless I start swinging on the end of the boom I don't think I'll be a problem.

U-bolts look like the way to go, and I'm going have to get used to the idea of going up the mast

[skipmac]

Originally Posted by Seasick Steve

I'm going have to get used to the idea of going up the mast

That does seem to be one of the occasional joys of owning a sailboat. I don't exactly love high places (doubt I could ever be a rock climber) but if I go up a mast with a good line AND a second safety line I feel quite secure.

[Seasick Steve]

I was a rock climber, but packed in when I lost my nerve. That was 20 years ago.

Still, with a reliable pair of hands on the bosun's chair halyard, and another on the harness halyard....
(note to self: get a bosun's chair)

[skipmac]

Originally Posted by Seasick Steve

I was a rock climber, but packed in when I lost my nerve. That was 20 years ago.

Still, with a reliable pair of hands on the bosun's chair halyard, and another on the harness halyard....
(note to self: get a bosun's chair)

A rock climber? One of those crazies, unlike sailors who are all completely sane and normal.

With that background you can just shinny up the mast. No need for a bosun's chair.

[Cheechako]

The wire clamps used for steering cable can be used. I think I've seen similar ones out of SS. There are copper versions for large wiring also.

[Seasick Steve]

I would refer the honourable member for Putnam to the last four words of the first sentence...

[Stumble]

Originally Posted by Seasick Steve

I was a rock climber, but packed in when I lost my nerve. That was 20 years ago.

Still, with a reliable pair of hands on the bosun's chair halyard, and another on the harness halyard....
(note to self: get a bosun's chair)

There is no piece of gear on most boats worse designed for it should job than a bosun's chair. Get a climbing harnes instead. That way if you lean back you don't splatter on the deck.