Lower spreader angles

[Travelling Westerly]

Just noticed that my lower port spreader is very slightly higher than the starboard one which is horizontal. I only noticed as I was looking at some other boats thinking that some had very different angles IE port positively up and starboard down.
Is a slight variation an issue?

Is it easy to move back into the horizontal? If I slacken the spreader end clamp can I just put my foot on it to move it down or is it going to cause damage or be unsafe whilst I'm up the mast?
Thanks

 

[sailorman]

i was told by a rigger, use a halliard make it off with end at the spreader base, swing the halliard out to the tip, & that is the angle of dangle

 

[PlankWalker]

Its your starboard spreader that's at fault.
The spreader should bisect the angle of the shroud, and therefore be above the horizontal.

 

[VicS]

[

Its your starboard spreader that's at fault.
The spreader should bisect the angle of the shroud, and therefore be above the horizontal.

Maybe a little more complex than that The cap shrouds will make very little in the way of an angle over the lower spreaders but if there are intermediate shrouds these will make an angle.

Do you set the spreaders to bisect what little ( if any) angle the caps make or to bisect the angle which the intermediates make ... or something in between?

 

[Rappey]

Lower spreaders? So are there two sets of spreaders?
Would imagine lowers are at a different angle to masts with single spreaders.

 

[srm]

According to stickers on my Kemp mast spreaders must be above the horizontal. This is to take the compression loads of the shrouds. A drooping spreader is a potential mast failure.
Some simple rigs on smaller boats (If I remember correctly on a Sparlight mast I owned) had tubular mast fittings that held the spreaders horizontal. This is probably acceptable with smaller boats but is poor engineering/geometry.

The spreader question has come up in a number of threads over the years, and I have attracted some negative comments for making the above points. Should anyone wish to argue I suggest that you read the Selden Masts rigging hints on their website's tech section:

Assembly and operation : Seldén Mast AB.

While these downloads are specific to Selden the engineering principles apply to any rig with standing rigging.

 

[William_H]

The actual attachment of the wires to the spreader tip varies with boats. On smaller boats where loads are not so critical the wire might run freely through a cage on the end of the spreader to keep it in a slot at the tip. Cage might be wire. This then relies on the robustness of the spreader to maintain the correct angle to the horizontal and to the wire. This arrangement makes it easy to adjust the tension of the stay.
On more sophisticated (larger) rigs the wire will be clamped to the spreader tip. This then maintains the spreader at the correct angle but can only be clamped after tension is set.
The angle as said is set to bisect the angle of the stay. This ensures that the column load on the spreader is true. This means angled up a bit.
So I suggest OP closely examine the spreader base for damage or wear and try to move it upwards. If it is clamped you will need to release the clamp move the spreader up then tighten. Ideally the spreader base should be so robust that it holds the correct angle (upwards) and wires do not dictate the angle but certainly must work together to set the angle.
No don't stand on the one that is not level. That may be what happend to the one that is horizontal. ol'will

 

[Laminar Flow]

Having designed and built a few rigs, incorrect spreader angles are a pet peeve of mine.
As Plank Walker said: the spreader should bi-sect the angle of the shroud. In the case of multiple spreaders where lower and upper shrouds run over the same spreader, you split the difference. Spreaders are designed for compressive loads only. When they are not bisecting the shroud angle, they are subjected to bending and compression and may well fail with obvious consequences.

 

[Boathook]

i was told by a rigger, use a halliard make it off with end at the spreader base, swing the halliard out to the tip, & that is the angle of dangle

I think that this is is what the rigger did when my rigging was renewed a few years ago, but he used the stay and then clamped it in position on the spreader. All made sense back then ....

 

[reeac]

I agree - bisect the angle in order to keep the spreader in pure compression.

 

[sailorman]

I think that this is is what the rigger did when my rigging was renewed a few years ago, but he used the stay and then clamped it in position on the spreader. All made sense back then ....

that makes more sense & on a double spreader rig you have 2 stays using the same lower spreader

 

[Travelling Westerly]

The actual attachment of the wires to the spreader tip varies with boats. On smaller boats where loads are not so critical the wire might run freely through a cage on the end of the spreader to keep it in a slot at the tip. Cage might be wire. This then relies on the robustness of the spreader to maintain the correct angle to the horizontal and to the wire. This arrangement makes it easy to adjust the tension of the stay.
On more sophisticated (larger) rigs the wire will be clamped to the spreader tip. This then maintains the spreader at the correct angle but can only be clamped after tension is set.
The angle as said is set to bisect the angle of the stay. This ensures that the column load on the spreader is true. This means angled up a bit.
So I suggest OP closely examine the spreader base for damage or wear and try to move it upwards. If it is clamped you will need to release the clamp move the spreader up then tighten. Ideally the spreader base should be so robust that it holds the correct angle (upwards) and wires do not dictate the angle but certainly must work together to set the angle.
No don't stand on the one that is not level. That may be what happend to the one that is horizontal. ol'will

Thanks for the advice ol'will

I'll nip up later and slacken the horizontal lower spreader end clamp. Is it as simple as knocking it upwards with my hand until the angle looks the same as the other? Is there any danger of cocking this up and the rig falling down?

 

[sailorman]

yes & no

 

[srm]

I'll nip up later and slacken the horizontal lower spreader end clamp. Is it as simple as knocking it upwards with my hand until the angle looks the same as the other? Is there any danger of cocking this up and the rig falling down?

That's what I would do (and have done in the past) Though it may need a bit of persuasion. Also look at the root of the spreader, some designs have stops to keep the correct angle. If you follow the guidance on getting close to bisecting the angle of the intermediate shroud you should be OK. Just don't over do it as that could endanger the rig. Also, try to see why the spreader got a case of the droops. Flag halyards are often the culprit.

If its any encouragement I re-rigged my current boat with the mast up. When it came to the shrouds I had to disconnect and drop both intermediate and upper on one side at the same time while I was up the mast. Ten years and quite a few thousand miles later the mast is still standing.

 

[William_H]

Thanks for the advice ol'will

I'll nip up later and slacken the horizontal lower spreader end clamp. Is it as simple as knocking it upwards with my hand until the angle looks the same as the other? Is there any danger of cocking this up and the rig falling down?

Yes if as you say the wire is clamped at the end of the spreader. (it may just slide through captured but not clamped) Yes knock it up with your hand to equal to the other one. However I emphasise do examine the spreader base to see if it is designed to have free movement or if it is worn or damaged in some way. ol'will

 

[Travelling Westerly]

Thanks for all the very helpful replies.

I would imagine the horizontal lower spreader is at that angle because 2 sets of riggers and myself (?) have trood on it when going up the mast. I watched the riggers do it so I followed in their footsteps (literally).

The spreader bases have a small amount of play in them to allow adjustment up or down.

Thanks again all

 

[JumbleDuck]

The spreader should bisect the angle of the shroud, and therefore be above the horizontal.

That's a theory. In practice, almost all the spreaders I see are horizontal. This means a little bit of bending stress in them (an angle-bisecting one would be in pure compression) but not really enough to worry about.

 

[Buck Turgidson]

don't forget that when judging the angle you should be looking from behind the shroud such that it is centred on the mast. Sweep will change the perceived angle.

 

[srm]

In practice, almost all the spreaders I see are horizontal.

I have owned boats with single spreader rigs where the mast fitting was such that the spreader could only be horizontal. A simple and cheap fitting that is acceptable on smaller rigs with low loads. The last boat like that was a smaller Prout catamaran.
However, my current boat has Kemp spars and the spreader fittings are such that they can not be forced into the horizontal plane together with stickers showing the correct angle. Selden bought up Kemp, and if you loook at the docs I referenced earlier in this thread all their diagrams show spreaders with outboard ends above the horizontal.
If you feel horizontal spreaders are OK for your type of sailing that is your choice.
Some may think I am being pedantic, but I prefer to be careful with my rig as it's not unknown for me to be well beyond motoring range to a safe harbour and outside the excelent cover provided by the RNLI. Having seen the work of some 'professional riggers' I prefer to set up my own rigging.

 

[JumbleDuck]

If you feel horizontal spreaders are OK for your type of sailing that is your choice.

Mine are as Proctor made them. It really doesn't make a great deal of difference.