Should Spreaders Clamp In Upper Shrouds Tightly?

justsomeguy · May 23, 2015

I would say "firmly enough to not move".

When setting my spreaders' positions, I loosely clamped down the tips so I could move them (with a long stick) until I was happy that the angles, both above and below the spreader, were as equal as possible.

Then, I gently lowered the mast and tightened the tips just enough to inhibit any further movement.

HTH.

Chief RA · May 24, 2015

My spreaders are not tight. They adjust to the correct position as I set and adjust the tension on the shroud lines. Chief

Jackdaw · May 24, 2015

Spreader tips should be TIGHT.

The shroud cannot be allowed to slip from its optimal position where it bisects the angle of the shroud turning from mast to deck. On almost all boats this will result in a slightly upward angle to the spreader.

Its strongest here. If loose it CAN slip down, often on the lee side in heavy air. Tighten them.

justsomeguy · May 24, 2015

DinoKanuck said:
THT,

If you mast got craned into position and you had no retightening option, what would you do?

Dino

I would do my best to find that optimal spreader position while on the sawhorses, I suppose. The shrouds won't stretch so much that it couldn't be done "close enough" to specs while horizontal.

Have a buddy keep good tension on the base of the shroud, set one spreader, measure the length of shroud above the spreader, and set the other accordingly.

Scott T-Bird · May 24, 2015

Hmmm ... my spreader tips have an open slot to accept the shroud. The shroud is held in place with monel wire criss-crossed over the shroud and secured. The angle of the spreader is fixed by the ears and doesn't move when the spreader is fixed by thru bolts.

It seems to me that there is no reason to fix the shroud to the end cap so that it can't slide through the slot (but the monel wire does tend to create friction that generally holds the shroud in place). When the mast is in place, tensioning the shroud fixes the spreader in line with the angle of the ears. If the shroud was fixed, tensioning the shroud at the deck would pull the spreader down, wouldn't it? I want neither upward or downward pressure at the end of the shroud. I want only inward pressure as the shroud is tensioned.

Chief RA · May 24, 2015

Mine do not slip. The spreader mounts protruding from the mast coupled with the tension of the shrouds hold them in perfect position. I also do not use the plastic covers on the ends of spreaders. Just be sure all is smooth out there! Chief

Chief RA · May 24, 2015

You explained it better than I did Scott, but we do it the same way! Chief

woodster · May 24, 2015

i am with Jack on this one....... as for setting them up just make sure the distance is equal on the spreader tips from the center of the tip to the mast tang pin on the mast on both sides ...mine slip in to a slot on the tip and then i safety wire them by making a double x crossing the tip with round turns on each side of the shroud

BigEasy · May 24, 2015

The rigging instructions that I received from US Spars indicated that the shrouds should be clamped tightly at the spreader tips. They didn't say why the shroud clamps should be tight.
I would imagine there could be a lot of movement in high wind & sea conditions that could cause excess movement & friction, resulting in premature failure of the shroud. Apparently the clamps should be snug with some movement possible and level when the rig is hoisted into position, then tighten securely after the rig tuning is completed.

Chief RA · May 24, 2015

I am not disagreeing with anyone. I am merely stating the concept and procedures utilized by me for around 30 years and in the case of the Clipper Marine 26', I raised her mast often through the years. Mast not raised often with the Catalina 250 and her heavy mast. Realize that my boats have always been large trailerable craft so what works for me may not work for other sailboats. As Stu says, "your boat, your decision"!
Chief

justsomeguy · May 24, 2015

What, can't make 'em both 15' 9 and 7/8ths?

Scott T-Bird · May 25, 2015

Are you saying ....

BigEasy said:
The rigging instructions that I received from US Spars indicated that the shrouds should be clamped tightly at the spreader tips. They didn't say why the shroud clamps should be tight.
I would imagine there could be a lot of movement in high wind & sea conditions that could cause excess movement & friction, resulting in premature failure of the shroud. Apparently the clamps should be snug with some movement possible and level when the rig is hoisted into position, then tighten securely after the rig tuning is completed.

After all is positioned, you climb the mast to do the final tightening of the spreader tips? That doesn't make sense to me. Are you saying that you climb the mast again after making final adjustments after sailing for awhile?

I also don't understand how you can measure anything accurately when the mast is down and in a horizontal position. There is no feasible way to tension the shrouds by hand to get an accurate position.

I'm guessing that spreader tips that hold the wire captive and are secured by a fastener don't actually clamp down on the wire shroud. The fastener simply secures the end of the tip so it can't come loose. The slot still has to allow movement of the wire shroud. Clamping an unprotected wire at that location would surely cause a wire failure, not by the miniscule amount of friction, but by constantly crimping and working the wire as you sail. I can't think of a worse thing to do than clamping the wire at this location. The strength of the wire would be severely compromised by any restriction between the terminations of the wire at the top of the mast and the chainplates at the deck.

Chief RA · May 25, 2015

Scott: another problem with this tight concept is while mast is down as you indicate the shroud length would be difficult to measure, plus our shrouds have been coiled up for transport and now not straight until we raise them back up! I don't get it! Chief

justsomeguy · May 25, 2015

If my post #14 wasn't clear, it's a boat. It doesn't need to be perfect (!), it just needs to be "good enough".

BigEasy · May 25, 2015

Re: Are you saying ....

Scott,
I honestly can't give you the rationale for US Spars specs for the spreader end clamps---maybe there is some provision in the design to allow for some vertical movement.
However, the US Spars mast installation operation / installation instructions specifically state, " During inititial setup, screw the shroud clamp on making sure that the cables are not locked. It will be necessary to lock the shrouds when final rig tuning is completed." I take that to mean that the shrouds should be tight inside the spreader end clamp when tuning is completed.

Scott T-Bird · May 25, 2015

I guess there must be a variety of ways the rigs are designed. And, in your example, the spreader end is actually called a shroud "clamp". If the shrouds on your rig are intended to be locked when final rig tuning is completed, I guess that means that you must climb the mast to lock the clamp as the final step. What if you want to make adjustments? I guess that means the first step is to climb up there and unlock the shroud clamps. Is that right? I can't see where final tuning can be accomplished when the mast is down.

In my case, the shroud is simply fitted into an open slot at the spreader tip. It's designed to be captured by monel wire. There is no way that the monel wire is going to clamp the shroud. I'm with Chief on this one. I don't even bother with an end cap. The tag ends of the wire are simply folded back on the spreader and taped with rigging tape to prevent snags.

If I were Dino, I wouldn't rely on random answers. Instead, he should look for the specifications for HIS rig.

Should Spreaders Clamp In Upper Shrouds Tightly?

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