Spreaders: Rigid or Movable?

[langstonelayabout]

For many years I raced dinghies where (once standing rigging tension was released) you could move the spreaders fore and aft, but not up or down the shrouds. Does 'good rigging practice' for sailing cruisers dictate that:

1 - Swept back spreaders should be fixed (up/down and fore and aft) or can they move fore and aft when the standing rigging tension is not applied?
2 - In-line spreaders should be fixed up/down and fore and aft, irrespective of rig tension. Is there an acceptable movement of the spreader tip? (resulting from movement/tolerance of pins or bolts securing the base of the spreader to the mast)

And is there a ISO or trade standard that specifies this type of information please?

Many thanks in advance

 

[NormanS]

Mine are fixed in both planes. I have never considered the idea of having them moveable. What possible advantage could there be?

 

[Quandary]

I have had half a dozen boats, masthead and fractional, none of them had provision for spreaders to move fore and aft. However nearly all of them allowed vertical movement and it was normal to make up a template for the perscribed angle and when setting the rig up to go up and set the angle of the spreaders accurately. Particularly important on our Sigmas which were raced hard and on the Finngulf which had discontinuous rigging. The latter was was one of the reasons we sold it setting up the rig became an arduous task every spring as you enter your ninth decade. With our current Moody, with an old fashioned masthead rig with no less tha 4 shrouds each side, I just mark the wires with tape when the rig comes down and clamp the spreaders at the same point before stepping it, then a visual check after she is in the water.

 

[Bobc]

Always fixed.

 

[langstonelayabout]

What possible advantage could there be?

None that I'm aware of. I guess I'm trying to understand if spreaders of either type have a permissible amount of 'slop' fore and aft, resulting from the bolts/pins retaining them to the mast fitting.

 

[Refueler]

All boats I've been involved with ... Hilyard, Snapdragon 21 .. 23 and 27, Alacrity, Vivacity, Debutante, Sunrider, Colvics of various, Pageant, Centaur, odd Moodys, Dolphin 31 etc ... have all had fixed socket spreaders. The main stays free to set up via U brackets at spreader ends. Spreaders set their own angle based on the socket.

Never had to measure or set position ...

My way was to get mast up .. fore and backstays reasonably taught to hold mast ... set babystays and then give a good 'shake' to the main side stays to make sure they were sitting correct in the spreader guides and then tighten up swapping side to side to make sure I tighten up evenly ... once set .. tighten up all others ..

 

[lw395]

Pivoting spreaders are (or were) used with some bending rigs.
Particularly, some dinghies and yachts with fractional rig and jumper struts. Kind of post-war?
Not common on new rigs these days AFAIK.
Swept spreaders are frequently used to control mast bend, both promoting pre-bend and limiting bend under way.
Some spreaders pivot one-way only, they can swing back to allow more bend, but have an adjustment to force them forwards, to give pre-bend. Often a wing bolt behind the spreader on dinghies of 'a certain age'.

 

[Rappey]

Spreaders on most small boats always appear to be set up wrong as they either slope down or are parallel to the water.. The tips should be higher than the point where they attatch to the mast as the angle between the spreader and cable should be equal above and below the spreader to support the mast with maximum strength.
Badly set up ones can end up with the spreader mounting points getting ripped off the mast.
Its so easy to set up, you connect the cap shroud to the mast at the top, lay it along the mast and mark the cable at the point where the spreader connects to the mast, then move it to the spreader tip and clamp. this gives the correct angle and the maximum support for the mast.
Swept back spreaders seem to be on masts that can be given mast bend on the fly, and eliminate the need for fore and aft lower shrouds by having just one lower shroud.
single spreader masthead rigs are fairly straight forward but twin swept back spreaders and bendy masts brings a whole load of complications to set up correctly.

 

[Refueler]

Spreaders on most small boats always appear to be set up wrong as they either slope down or are parallel to the water.. The tips should be higher than the point where they attatch to the mast as the angle between the spreader and cable should be equal above and below the spreader to support the mast with maximum strength.
Badly set up ones can end up with the spreader mounting points getting ripped off the mast.
Its so easy to set up, you connect the cap shroud to the mast at the top, lay it along the mast and mark the cable at the point where the spreader connects to the mast, then move it to the spreader tip and clamp. this gives the correct angle and the maximum support for the mast.
Swept back spreaders seem to be on masts that can be given mast bend on the fly, and eliminate the need for fore and aft lower shrouds by having just one lower shroud.
single spreader masthead rigs are fairly straight forward but twin swept back spreaders and bendy masts brings a whole load of complications to set up correctly.

So how are you going to secure the stay at your measured point when many spreaders only have a U bracxket at end for stay to pass through - it does not clamp it in place.

Second - your description makes no allowance that a mast 'works' when sailing ... and is another reason why many spreaders do not lock the stay to a set point.

 

[srm]

and is another reason why many spreaders do not lock the stay to a set point.

Simple geometry, the spreader must bisect the angle between the lead of the shrouds to avoid bending forces on the spreader and keep it in compression. The Kemp mast on my boat has warning notes to this effect on the spreaders and clamps on the ends to keep the spreader at the correct angle.

 

[reeac]

Spreaders on most small boats always appear to be set up wrong as they either slope down or are parallel to the water.. The tips should be higher than the point where they attatch to the mast as the angle between the spreader and cable should be equal above and below the spreader to support the mast with maximum strength.
Badly set up ones can end up with the spreader mounting points getting ripped off the mast.
Its so easy to set up, you connect the cap shroud to the mast at the top, lay it along the mast and mark the cable at the point where the spreader connects to the mast, then move it to the spreader tip and clamp. this gives the correct angle and the maximum support for the mast.

I had to think about that that assertion .....I think that it's true as long as the spreader is equal in length to half the spacing between the port and starboard chainplates but I don't know whether that's always the case.
I actually made some replacement timber spreaders for a prewar dayboat once so just copied their length. At each outer end I drilled a vertical hole and then cut a slot to it, giving a rounded end. I then inserted a horizontal M3 bolt and s/l nut positioned in the timber so that the shroud just touched the bolt. This gave the shroud something hard to bear on and also introduced a compressive stress into the timber at that critical point in order to discourage splitting. Seemed to work OK.

 

[Daverw]

We’ve just had to replace spreaders on our Z spars mast, the original had sockets which each located in with two pins on each, the replacement kit which Zspars supplied used a spar through the mast, this is how all theirs are fitted now. Makes it fully fixed in all directions, no movement at all. The spar is swept back 25 degrees and quite substantial and tight fit onto spreaders So no possibility of tip being moved up to equal angle to stays. Obviously ZSpars don’t seem to see the need

 

[William_H]

Spreader angle is vital in those which are swept back typically in a fractional rig. I lost the first mast on my little boat when the spreader lost its proper attachment at the base and moved forward. Hence losing push forward of the middle of the mast (normally against the aft pull of the intermediate side stays.) so mast crumpled middle backwards. Not so critical in inline as often seen on mast head rigs. Regarding the angle of intersection of the spreader to the shroud. This correctly should be equal angled for the shroud upwards and down wards from the tip. However geometry will show that this is not so critical as a few degrees off will not add much sideways end pressure to the spreader. In my boat the shroud is free running in the spreader tip. (but is captive) ol'will

 

[langstonelayabout]

So, in summary, does anyone know how much 'slop' fore and aft, resulting from the bolts/pins retaining them to the mast fitting?

Aside from the strength of the fittings and brand of the mast, is an inch or so of slop in in-line spreaders considereed a problem?

I ask as having reviewed the ISO specifications for bolts and pins in holes, as using tolerances in line with ISO specifications enable s the spreader tips to move an inch or so fore and aft. Is this a problem?

 

[Daydream believer]

Aside from the strength of the fittings and brand of the mast, is an inch or so of slop in in-line spreaders considereed a problem?

In practical terms, ask yourself what % of yachts in normal cruising, non racing situations, loose their masts. Then ask what % of that loose them due to slop or lack of it in the spreaders ( other than due to poor maintenance etc)
Then ask yourself- have designers got it fairly well nailed? if so --Why worry?

If you are really saying " I have a knackered worn out set of spreaders & fittings & wonder if they need replacing", then come clean & admit it to the forum & go from there

 

[Refueler]

In practical terms, ask yourself what % of yachts loose their masts. Then ask what % loose them due to slop or lack of it in the spreaders ( other than slop due to poor maintenance etc
Then ask yourself- Why worry?

I have to agree with this.

There's theory and there's practical. Spreaders sit there year after year - often literally forgotten ... only when occasionally mast is dropped and an eye is cast over the setup may they even get a whiff of attention. I wonder how many have actually taken the trouble to pull the pins and remove spreaders to check the mountings ?
Lets also cast our thoughts to fractional rigs and the boys who 'bend' their masts depending on wind angle etc. - imagine those poor old spreaders ... one minute mast is near straight and stay is nicely vertical through spreader to deck ... then Jo decides to tweak the back stays and mast bends aft ... now that stay is not so nicely vertical for the spreader ...
Next - over the years - the spreader socket and pin will work ... so that nice technical amount of movement when new will slowly become 'sloppy' .... does it stop spreader doing its job ?
Many spreaders I have worked on or observed over years have had split pins or just plain machine nut and bolt ... I must admit that my mast does have a slight upward angle to the spreader socket so they may look horizontal from the deck - but in fact do have a few degrees.

As DB - says - how many masts lost because of spreaders ?

Bembridge Hbr ... exiting on my Snap 23 .... forestay ripped out of deck and furling gear etc on its way took stbd spreader with it ... weather was fast increasing to near gale and I was bouncing onto Bembridge sands out near the Fort. Lifeboat came out and towed me in ... they used rocket line as they couldn't get near in the shallows ...
The point here is that even though one spreader mount was broken letting spreader fall away hanging on the stay - the mast never bent / made any signs of damage / stress even though it had full genny and furling gear literally flying horizontal from mast head ...
it took Harry - my SBS pal and his strength along with me - to get that gear back down again ... using the sheets and furling line ... we used spinnaker halyard as a temporary forestay

 

[lw395]

So, in summary, does anyone know how much 'slop' fore and aft, resulting from the bolts/pins retaining them to the mast fitting?

Aside from the strength of the fittings and brand of the mast, is an inch or so of slop in in-line spreaders considereed a problem?

I ask as having reviewed the ISO specifications for bolts and pins in holes, as using tolerances in line with ISO specifications enable s the spreader tips to move an inch or so fore and aft. Is this a problem?

How much slack is acceptable will vary from rig to rig.
On most yacht rigs the primary function of the spreader is to hold the mast in column side to side, which is all about length more than angle.
But these things stack up. Allowing the base to twist on the base has a similar effect. Wrong tension doesn't help.
Apart from collisions, dynamic effects are often important in losing masts, does it move the spreaders in chop or is that all controlled by e.g. a baby stay?
If you see the mast 'pumping' in weather, will you understand and be able to do something to control it?

 

[Daydream believer]

On most yacht rigs the primary function of the spreader is to hold the mast in column side to side, which is all about length more than angle.

Add "and to prevent inversion of the rig" (on many types)

 

[lw395]

Add "and to prevent inversion of the rig" (on many types)

Youre right but that's the secondary function. Which is often shared with lower shrouds or baby stay.
On a fractional rig, the backstay enforces bend in the correct direction.
On a keel stepped mast, chocking at the partners (deck level) has an influence.
The mast is generally much narrower side to side than its fore/aft dimension, so it's needing more support to keep it in column side to side.
Rigs vary a lot. Even those which have superficially the same components.

In several classes, swinging spreaders have a performance advantage but are banned because they increase the risk of mast failure. Other classes have been sailing with spreaders with no fore-aft strength for decades.
First question should perhaps be 'is this what the designer intended?'

 

[Rappey]

I have seen a mast T base on a fore and aft thread so the base can be moved to increase or decrease the mast rake. Who would have thought just a degree or two could make such a huge difference to the handling of a sailing boat !
My spreaders (very heavy mast) have two large clevis pins attaching it to the spreader mount so fore and aft movement should be zero and the base they slot inot points slighty up..