Stay covers & Stay <-> Spreader connections

[GreenLake]

The spreader should bisect the shroud into two equal angles, so that there are equal forces pressing on the mast (i.e. pure compression/no side forces) with the base of the triangle equal to a straight line between the chain plate and the shroud tang. That's 97 degrees from the lower mast to the plane of the spreader.

There are some spreader designs where the hinges at the mast make it substantially impossible to tilt the spreaders up and down. In those cases you are stuck with 90 degrees instead of 97, and need to hope that it's "close enough" so that whatever remaining non-compression loads the spreader receives will be manageable (I've sailed often enough with the spreaders slightly misaligned and it's never caused spreader failure. I found that failure came from incidents during mast raising or lowering (or happened while the mast was down. New spreaders proved no more resistant in those cases than old).

... I'd think you'd want the stay to be able to slide freely in the slot so that when the rig is tensioned, it will "find" it's correct place on the spreader end, or more precisely, vice versa, the spreader end will find it's place on the stay? Make any sense?

I think this does make sense. With wires too tight, spreaders can't be adjusted at all, but the distance between top of the shroud and spreader is smaller when there's no tension on the shroud. With wires very loose, the spreaders will slide down and "sag". However, it's easy to push them into position with a paddle before tightening the shrouds. Only problem is in forgetting this step. Whether locked or sliding seems to make no difference in durability - at least in my case where I can trace failure to inadvertent loads on the spreader when the mast was not fully rigged.

[jdoorly]

Hi Salty Dog, or should I say WOOF!

On the home page of this website (http://forum.daysailer.org) and under menu item "Day Sailer Association" click on "Handbook" then click on part 3 and scroll to drawing 7.1 to see a graphic representation of the mast particulars, including upswept spreaders.

I suggest you surf through the other menus, there's a lot of good info. woof woof.

[GreenLake]

Where do you get a DS Hand book?

The direct link to the section that was cited is:
http://daysailer.org/pdf/dsbylaw3.pdf

And, yes, jdoorly makes a good suggestion to explore the other menu item. Bob tells me he plans to link the top of the forum pages back to the same menus, but that means customizing some to the PHP pages and he'll need to find the time for that.

[jeadstx]

My spreaders are perpendicular to the mast. I have the heavy duty spreaders with the square ends from D&R Marine, my spreader mounts are original to the mast. The spreader that broke before the start of the Texas 200 seems to have been caused by a "bird strike" while trailering to the coast. My repair was done while the boat was in the water while the mast was up. We had a dock space with a wall that came up to the height of the spreader.

John

[Salty Dog]

Thanks guys

I will check it out. I have looked at the ones labled Manuals, I will go find the one labled hand book

SD

[Breakin Wind]

The spreader should bisect the shroud into two equal angles, so that there are equal forces pressing on the mast (i.e. pure compression/no side forces) with the base of the triangle equal to a straight line between the chain plate and the shroud tang. That's 97 degrees from the lower mast to the plane of the spreader.

I hadn't considered this before but it makes perfect sense. The stay without the spreader would be pulling down (and out) on the tang, and by putting the spreader in at a 90 deg angle out rather than the slight angle up, the working pressure on the end of the stay would be trying to bend it down (and in). If the spreader cannot be adjusted up to split the difference in the angle, then the best I can do is to push up on the spreader end (to consume any available slop in the spreader joint, and then tightly bind the stay to the spreader at that point. Any slippage in the stay/spreader joint will result in the spreader trying to work it's way down the stay where the "down and in" pressure will become more prevalent.

Interesting that the spec would call for the spreader to be angled up, but the hardware doesn't allow for it.

Thanks - Scott

[jdoorly]

WARNING! Will Robinson, WARNING!

Been digging into this spreader stuff and find in all references that the spreader tip should be hard fastened to the shroud, that is No wire movement in the slot! Skenes (Kinney) actually warns of potential dismasting.

Didn't find any explanation of why we might want a hinged spreader, but many descriptions about using a fixed (laterally) spreader to help bend mast and shape main.

All references found confirm upswept spreader, i.e. 7 degrees up from horizontal (bisect the shroud in 2 equal angles). However couldn't find anyone adding a tolerencing statement to above.

I checked my spreader bases and found them so bent up that one side was upswept and the other downswept! I noticed that the base was secured by 3 rivets and that when originally fastened they could have been rotated slightly thus gaining the required 7 degree slant, However, I measured from mast slot to the 2 closest rivets and found they were equal, so no one tried to slant them that way on my boat.

I would like to remedy this situation this spring but I haven't figured out how yet. Bending the tube would be counterproductive. Pressing downward on the base could bend to pivot pin up to 7 degrees (this has already happened to one side on my boat) but it will focus forces on the pivot rather than the base rivets. If I remove the base and reposition slightly higher and rotate to get 7 degrees at the tip; when I tightly secure the wire to the tip I don't think the spreader will still pivot but I don't know why it was designed to pivot. I think I may have to replace the spreader and base with a fixed one to get it right!

[Alan]

viewtopic.php?t=3684

The above is a link to another thread on spreader angles, with about halfway through, a link from K.C.Walker to a set of Selden spreaders that can be adjusted vertically.

(edit) Oops, never mind. The Selden spreader link went away, apparently because Selden now makes spreaders with the up-or-down angle (dihedral angle) built in. The Selden dinghy catalog, here:

http://www.seldenmast.com/frameset.cfm? ... =480681769

shows the spreaders with a slight upward angle, not horizontal.

[GreenLake]

All references found confirm upswept spreader, i.e. 7 degrees up from horizontal (bisect the shroud in 2 equal angles). However couldn't find anyone adding a tolerencing statement to above.

If my estimate is correct, being 7° off from true position puts 12% of the load into downward (rather than compression) load. That would be if the the joints at both ends were fixed. If they act like hinges, then these downward loads are not actually transmitted along the spreader. (I think that may well be the case as neither connection is perfectly rigid).

[Breakin Wind]

Since the topic here has expanded from my orginal question to one that is more broad and important, I edited the subject line to be more inclusive. - Scott

[TIM WEBB]

Does all this info apply to our backswept spreaders only, or to all spreader designs?

I always figured our spreaders were hinged to make trailering easier on them ... ?

I see the rig on our boats as a "pyramid", so to speak. With no backstay, and all three stays attached to the mast at the same point, what happens above the hounds stays above the hounds. All mast rake and bend happens at the partners/step, no?

[jdoorly]

Hi Tim,

Yeah, this stuff is not DS specific.

I think there are times when having hinged spreaders keeps them from breaking and times when it causes breakage, guessing I'd say it's 50-50.

The top of the mast, above the hounds, is greatly affected by the main leech tightness (mainsheet) and that leverage also affects the middle third of the mast. The for 'n aft angle of the spreader divides the spreader body compression vector into holding the mast straight (major, x-plane) and bending the mast forward (minor, y-plane). Of course setting the mast step aft and the partners forward would add to and compliment the mast bend. You could reverse the step and partner settings and create an "S" curve if you want.

I've often thought about removing the spreaders because I've broken so many. The DS is considered a low aspect rig, and I understand the minimum angle for a shroud is only 9 degrees from vertical. Since I'll be replacing my wire shrouds this spring with dyneema I hope I get a chance to try.

[GreenLake]

A standard hinge acts only in rotation around the pin. However, unlike a door hinge, many of the spreader designs for the DS (and there are more than one configuration even before after-market upgrades) allow the spreader to move a few degrees up and down as well. Because of that flexibility, the connection acts like a hinge in transferring loads. If you push down on the spreader end, but the spreader is able to "give" then you can't transfer a turning moment to the mast. If you have one of the beefier setups, they may lack that flexibility and would transmit such loads. They are presumably strong enough to handle them.

The hinge action in the horizontal plane seems indeed needed primarily for trailering, but it has the secondary effect that any loads on the spreaders are purely in compression, as the spreader is free to align with any changes in direction of the load, however small.

With a bit of elementary trigonometry it's easy to work out what the effect of spreaders should be on the DS rig. I you do that exercise, you will find that having spreaders has two effects. It increases the sideways (and backward) force at the hounds for the same amount of overall shroud tension (and same amount of mast compression). At the same time they add a forward push to the mast at the spreader location, which should support any mast bend.

I'd definitely try to work out those numbers and understand their consequence before contemplating any drastic alteration in rig geometry.

[TIM WEBB]

Jay, that's funny you should mention sailing w/o spreaders, because I did exactly that with the 'Witch wayyyy before she got me. The co-worker of mine who's yard she was living in at the time (not even the real owner) asked me to take her out for a spin, and we had no spreaders, old blown out sails, and a bunch of other stuff missing/wrong. Even had a rat crawl out of the cuddy and jump overboard! It's a wonder we didn't put her on her side, but we didn't. I wish I could remember how the mast/shrouds were acting, but that was a lotta years/lotta beers ago, and I just remember thinking that I wish I could take this old boat home, which thankfully I eventually did. One of the 1st things I did was put on spreaders ...

Those Dyneema shrouds sound interesting. I've often though about Spectra shrouds. At work we use everything from 425 - 1500 lb Spectra ... ?

[jdoorly]

I just read some stuff on...

http://www.classicmarine.co.uk/Articles/Reference%20start.htm

that was both informative and fun to read about stays and spreaders and more. In the last article he rates dyneema for various applications like shrouds and halyards, but draws some different conclusions than these people (the marketers)...

http://www.dyneema.com/emea/applications/ropes-and-lines/sailing/dyneema-max-technology.aspx

Who to believe? There are many other sources confirming Dyneema's abrasion and UV resistance, such as...

http://en.wikipedia.org/wiki/Ultra-high-molecular-weight_polyethylene

I used a Dyneema forestay (with 2 eye splices and one long splice to make it longer) for the last year and a half with no problems. So, it seems there are NO drawbacks to Dyneema!

I have 1/8" Amsteel Blue which I will splice eyes to on the ends, and use a stay adjuster on the chainplates. I think I will lead some SS wire through the 12 strand and with some firm wraps in way of the spreader tip to secure it.

I suppose GL is scatching his head wondering how many tacks we can take this thread on!