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My spreaders are drooping. Help

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bill bosworth
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USA
172 Posts

Response Posted - 04/21/2011 : 17:48:11

Michael;
I have looked at my spreaders on several occasions and wondered if they were at different angles. What I concluded is that due to the swept back design, and rake of the mast, it is very difficult to stand on a dock and make a determination. If you are not in a direct line with the boat, the spreadrs appear to be at different angles. We launched, and put our mast up today. I looked at the hardware for mounting the spreaders, and compared the spreader angles with the mast laying horizontal on the deck. I found that they do angle upward to form a proper angle with the upper shrouds. I would be very careful about forcing the spreaders into a new angle. Additonally, It would seem that the spreaders are very well attached to the mast, I can't imagine why any cable clamps etc. would be needed to keep them in their proper position. I would be concerned that with the length of the spreader, and the strength of their mounting, that to much force on the end of the spreader could distort or crush the mast section.
best of luck, good sailing.

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mikesuej
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119 Posts

Response Posted - 04/22/2011 : 04:30:39

Those all good tips - - - thank you. I considered the swept back design as part of the optical illusion and that was my initial conclusion - that they looked droopy because of the sweep. But when looking from the side a distance out, it does appear they are drooping quite a bit. I'll loosen stays a bit and gently push up with long pole. If there's no movement, I'll go up on the mast climber and get an eye-spreader look before I try anything else.

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TakeFive
Master Marine Consultant

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2272 Posts

Response Posted - 04/22/2011 : 07:46:24

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by RhythmDoctor
 ...I really want to get the spreader height locked in prior to raising the mast. That's why I want to do the calculations first and seize the spreaders in place while I am at deck level. I'll post my trigonometric calculations as soon as I get time to sketch them out. The results surprised me a bit (lower angle than I expected), so I'd like to get your feedback.
<hr height="1" noshade id="quote"></blockquote id="quote">
Since I have never raised my mast before, I do not know for sure how well it's going to work out trying to fix the spreader height with the mast down. When I go to actually do it (this weekend) I may find that the distortions caused by moving my mast around make it impractical, and I will need to nudge the spreaders around with an extension pole once they are up. But last year when I did that it ended up breaking the seizing wire, so I still hope to seize the spreaders at the right level before I raise the mast.

I had promised to share my trigonometry. I am posting this for your comments and comparisons with your own measurements. USE THESE CALCULATIONS AT YOUR OWN RISK. I WILL NOT BE REPONSIBLE FOR ANY DAMAGES TO YOUR BOAT

Much of the trigonometry is too complicated to put up here, but there are some very simple approximations that get basically the same answer. Let's imagine first that we tighten the upper shroud into a straight line without the spreader. Then, like inserting an arrow into its bow, let's orient the spreader perpendicular to the shroud. The below graphic is not to scale. The beam W from the mast to the bail is shown much wider than it actually is, so that the angle is actually much smaller than drawn:

<center>

</center>

Using this as a first approximation, I did some additional trigonometry to demonstrate that the spreader angle of 5.2° estimated by this method (for my own standard rig) is within a half-degree of the what is calculated by the full method, depicted here graphically:

<center>

</center>

The surprising thing for me is that an angle of 5-6° is much less than typical. In order to achieve this angle I need to pull the spreaders down to the very low end of the available play in the brackets. Unless I sieze them at this low angle prior to raising the mast, they are likely to wander up as as the mast is raised.

Does anyone have any measurements of actual spreader angles on the mast that show that a higher angle gives proper bisection of the shrouds?

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Arlyn Stewart
Master Marine Consultant

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USA
2980 Posts

Response Posted - 04/27/2011 : 04:06:58

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by RhythmDoctor
 Yes, in my case the boot would cover the cable tie. I like the idea of a cable tie because I can tighten it as tight as I want without damaging the cable. I think they even make tensioning tools for the plastic ties to get it as tight as possible.

AFAIK, the corrosion problem with rigging tape is due to moisture entrapment. When you wrap it around the cable it has a high aspect ratio (the width of the tape is much more than the diameter of the cable that it's wrapped around), and that high aspect ratio is an impediment to drying under the cable (restricts water going out and, more importantly, air coming in). The cable tie is narrow enough that it would not trap water or impede the flow of air.

Part of the reason for this is that I DO NOT want to go aloft to adjust the spreaders (or anything else). I really want to get the spreader height locked in prior to raising the mast. That's why I want to do the calculations first and seize the spreaders in place while I am at deck level. I'll post my trigonometric calculations as soon as I get time to sketch them out. The results surprised me a bit (lower angle than I expected), so I'd like to get your feedback.
<hr height="1" noshade id="quote"></blockquote id="quote">

Do you rig wrap your fore life line terminations?

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