How important is binding shrouds to spreaders, so spreaders don't slide up and down?

[rpeskett]

Hi,

I have a 33-foot Dwyer mast, only five years old, in excellent condition, with five-year-old Dwyer spreaders, as pictured. I read that most people bind the shrouds to the spreaders to stop vertical movement. However, when I inspected mine, recently, they were not bound. The shrouds could slide up and down, through the holes in the ends of the spreaders. The only binding of the shrouds to stop vertical movement was squeezing the spreader boots around the shrouds, where they passed through the boots, with zip ties and wire. Even with this, I could easily slide the shroud through the spreader boots. So, I don’t think this was significant in stopping vertical movement. I assume they were like this for years, with no failure.

I have included a drawing that lists the spreader part numbers: Airfoil spreader part D2503.

Considering that ...
With moderate force (an extremely rough estimate of one pound), I can move the ends of the spreaders up and down about a total of less than two inches at the tips,
the spreaders didn't fail, for years,
one of the previous owners pushed the boat quite hard, and
the rig survived "twenty-foot waves," during a storm,
The shrouds have all been replaced in 2015,...

how important do you think it is to bind the shrouds to the spreaders, so they don't move up and down through the spreaders? I intend to do day sailing, with very little racing. I'll be sailing in winds with gusts up to about 30 knots. I have an adjustable backstay, but I won't be doing any extreme raking of the mast.

I'm about to step my mast, this weekend, and I've been worrying about whether or not to try to stop vertical movement of the shrouds.

All of my questions, here, are only relevant to this vertical movement. I’m assuming that the horizontal movement of the spreaders is prevented by the passing of the shroud through the plate at the end of the spreaders, as shown in the attached image.

Would you please tell me a little about the following questions?

If you have experience with your own spreaders or recommending that people not bind the shrouds to stop vertical movement relative to the spreaders, how much experience do you have?

If you recommend not binding the shrouds to stop vertical movement, hat are the advantages of letting the shrouds slide up and down through the ends of the spreaders?

What might make the airfoil spreaders, part D2503, and the brackets in the attached image, different than the spreaders and brackets that so many people use and recommend binding to stop vertical movement?

Do you have any statistics related to how many spreaders you’ve used or delivered or installed without binding the shrouds to stop vertical movement?

Do you have any experience with or statistics related to the number of spreaders that failed after not being bound to the shrouds to stop vertical movement?

If airfoil spreaders fail, is it usually because they rotate or collapse, horizontally, or vertically?

I’m leaning with going with the Dwyer staff member's statement and let the shrouds slip up and down, and I'm also leaning toward not using spreader boots (he also said they weren't necessary, for my spreaders). I prefer to be able to see the tips of the spreaders, from below, without boots, and I prefer to minimize water and corrosion. Aside from preventing damage to sails, I don't think the spreader boots do much to stop vertical movement.

Thank you for your time,

Rick

[JPA Cate]

AFAIK, the spreader should bisect the angle it meets at the shroud. If you need bulldog clamps to make it happen, okay.

I'm not sure what was going on where that spreader was ripped out, so will not comment. Did not respond to poll because my option was not listed therein.

Ann

[CassidyNZ]

Originally Posted by JPA Cate

AFAIK, the spreader should bisect the angle it meets at the shroud. If you need bulldog clamps to make it happen, okay.

I'm not sure what was going on where that spreader was ripped out, so will not comment. Did not respond to poll because my option was not listed therein.

Ann

I think the “ripped out” part is a leather or rubber boot/cover removed for inspection.

Having a spreader bisect the angle at the shroud would imply that it needs to be in a considerable upwards attitude mast-to-shroud (at least on a top spreader) which I believe is uncommon. My understanding of spreader location is that it should be horizontal. In fact, one of the spreaders on my boat somehow got moved up at the end and a rigger passing by commented that if I really wanted to risk my mast in heavy weather, I should leave it that way.

I adjusted it the same day.

And, getting back to the OP’s question, whilst I can’t cite any bullet-proof qualification I may have, I cannot recall ever having spreaders with free-floating ends on any one of several boats I’ve owned over the last 35-odd years. Hope that is satisfactory experience.

[RaymondR]

If the spreader is rigged as Ann suggests there are no forces generated upon the spreader other than compressive towards the mast.

However if the spreader is rigged horizontal to the mast the resultant of the two force vectors created by the shrouds passing over the spreader ends to the mast cap and vertically to the chain plates generate a both a horizontal compressive force on the spreader as well as a downward force on the end of the spreader and if the shroud is free to slide over the end of the spreader a bending failure of the spreader is bound to occur.

Consequently the shroud should be restrained from sliding over the end of a horizontal spreader.

And, although the resultant forces may not demand it, it is probably a prudent measure to capture it at the end of the spreader on a rig where the equal bisection of the shrouds angle of diversion.

[DefinitelyMe]

Originally Posted by CassidyNZ

Having a spreader bisect the angle at the shroud would imply that it needs to be in a considerable upwards attitude mast-to-shroud (at least on a top spreader) which I believe is uncommon. My understanding of spreader location is that it should be horizontal.

Absolutely not. As others have said, the spreader should bisect the angle made by the shrouds so that it is only in compression. That may mean that it is indeed at a 'considerable upwards attitude'. Binding may or may not be necessary to acheive this. For me it is.

There are many professional sources to support this. This book is one of them. Covers all the basics, including spreader angles and rig setup.

https://www.amazon.com/Sailpower-Tri.../dp/1574091778

[Benz]

Ann is correct that as far as loads go, the spreader should bisect the angle of the shroud, unless the spreader is designed for a bending load. Brion Toss' "Riggers Apprentice" has a good discussion on this.
When placed at the proper angle, with the shroud tensioned, there will be no tendency to move. If it worries you, you can wrap a little seizing wire to the shroud above and below the tip to hold it in place if the lee shroud goes slack, but ideally the lee shroud will never be that slack.
If you replace the boot, make sure there's plenty of Tef-Gel in there--one of the evils of boots is that they trap moisture inside so that the shroud can crevice-corrode while eating away at the aluminum tip. I prefer no boot at all.

[sanibel sailor]

There was just an article on this in Good Old Boat magazine.

Should bisect. Mine are horizontal, my spreader mount determines this. I am going to get a couple of two piece shaft collars and tweak the spreaders up as high as the mounts will allow and put the shaft collar on below the spreader. My shrouds are 9/32", no matching collar available, so I will get 1/4" aluminum ones and drill them out to size.

https://www.mcmaster.com/#6436K131

[hpeer]

I’m surprised you can slide the spreader so easily. My gut reaction is that your shrouds have far too little tension. Because the spreader is to bisect the angle, which can be slight, it should be in compression, which would put some considerable force on the spreader.

This summer I had occasion to assist a very experienced sailor adjust his shroud tension. He was prepping for a trans-Atlantic sail and had just completed a long passage and had sailed the boat long distances in the preceding decade+. He had never checked his shroud tension other than by feel, didn’t know about a Loos gage.

His shrouds were way out of wack and nowhere near balanced, some with 5% tension, some with 17%. We got them all back around 12% checking for plumb. I got him started and then left him alone. I think he spent several hours at it.

Anyway, just my gut reaction.

[rpeskett]

Originally Posted by JPA Cate

AFAIK, the spreader should bisect the angle it meets at the shroud. If you need bulldog clamps to make it happen, okay.

I'm not sure what was going on where that spreader was ripped out, so will not comment. Did not respond to poll because my option was not listed therein.

Ann

Hi Ann,
Thank you. The boot was ripped off the spreader for inspection. The spreader was not ripped out.
Rick

[rpeskett]

Originally Posted by CassidyNZ

I think the “ripped out” part is a leather or rubber boot/cover removed for inspection.

Having a spreader bisect the angle at the shroud would imply that it needs to be in a considerable upwards attitude mast-to-shroud (at least on a top spreader) which I believe is uncommon. My understanding of spreader location is that it should be horizontal. In fact, one of the spreaders on my boat somehow got moved up at the end and a rigger passing by commented that if I really wanted to risk my mast in heavy weather, I should leave it that way.

I adjusted it the same day.

And, getting back to the OP’s question, whilst I can’t cite any bullet-proof qualification I may have, I cannot recall ever having spreaders with free-floating ends on any one of several boats I’ve owned over the last 35-odd years. Hope that is satisfactory experience.

Hi,
Thank you very much. You were correct about what was ripped out: just the spreader boot. My spreaders do bisect the angle they meet at the shroud. Thank you for sharing your experience.
Rick

[MartinR]

Horizontal spreaders must be fixed at the end. And the fixation needs to be substantial as there are pretty heavy downward forces here. If the spreaders are not locked, they will be experiencing bending moments, which they are not designed for.

The more common bisection spreaders should be fixed at the end, unless the mast fitting is very substantial and there is no risk of the spreader sliding. There are no bending moments on these spreaders until they go out of alignment, so the fixation can be less stringent.

Many spreaders have locking screws integrated into the ends.

Basic answer: Yes, they need to be fixated at the end.

[rpeskett]

I would like to ad that I have recently inspected the male tabs that protrude from the spreader brackets into the spreaders. They are very solid, with no evidence of weakness.

[roverhi]

The spreader doesn't need to be seized to the wire to keep it in place. It's not a bad idea to do it anyway. Especially if you stand on the spreaders to navigate through coral or regularly stand or sit on the spreaders. Your weight can cause the spreader to slide down the wire.

Do check how the wire is kept in place on the spreader. Had the cap shroud come free on a delivery. The shrouds were secured to the spreader by a piece of thin plastic and the plastic broke. We were reaching off and had a couple of crash jibes. Not much fun to look up at the mast when your 50 miles at sea to sea the mast head wobbling and the cap shroud swinging free.

[rpeskett]

Originally Posted by DefinitelyMe

Absolutely not. As others have said, the spreader should bisect the angle made by the shrouds so that it is only in compression. That may mean that it is indeed at a 'considerable upwards attitude'. Binding may or may not be necessary to acheive this. For me it is.

There are many professional sources to support this. This book is one of them. Covers all the basics, including spreader angles and rig setup.

https://www.amazon.com/Sailpower-Tri.../dp/1574091778

I agree. Mine bisect the angle, thanks to the angle of the spreader brackets. That reminds me that the force should be mainly compression. I'll look into that book.

Thank you, very much!

[rpeskett]

Originally Posted by hpeer

I’m surprised you can slide the spreader so easily. My gut reaction is that your shrouds have far too little tension. Because the spreader is to bisect the angle, which can be slight, it should be in compression, which would put some considerable force on the spreader.

This summer I had occasion to assist a very experienced sailor adjust his shroud tension. He was prepping for a trans-Atlantic sail and had just completed a long passage and had sailed the boat long distances in the preceding decade+. He had never checked his shroud tension other than by feel, didn’t know about a Loos gage.

His shrouds were way out of wack and nowhere near balanced, some with 5% tension, some with 17%. We got them all back around 12% checking for plumb. I got him started and then left him alone. I think he spent several hours at it.

Anyway, just my gut reaction.

Hi,
Thank you. There is no tension because the mast is down. I'll look into getting a Loos gauge.
Rick