Rigging a Two Spreader Mast

[Ron Bowman]

I'm looking for rigging advice. I have a two spreader rig with the top shrouds running all the way to the deck. The problem is that when I added the second set of spreaders at the top, I set them at the same angle as the lower spreaders. So the shrouds running from the deck to the top spreaders rub/chafe against the back side lower spreaders. The only way I can avoid that is to rake the mast aft and then bend the mast by tensioning the uppers. The result is about five inches of prebend in the mast and a fair bit of rake. Unfortunately, my main was cut for less prebend so it doesn't set right once I get the mast bent enough to get the shrouds away from the spreaders.

So, what I want to do is rig the uppers differently and am looking for suggestions how to best do that. I've thought about making the uppers diamonds and also somehow joining the two top shrouds together above the lower spreaders so they are both adjusted with one turnbuckle at the deck. But I'm struggling to figure out the best way to do either of those options.

Anybody have suggestions about how to solve this problem – so the uppers do not rub against the lower spreaders so I can tune my mast slightly straighter to match the luff curve of the main?

Ron Bowman
Lunatic Fringe #108

[Chad]

If they're wire, then take the masthead wires over the lower spreader tip. Or drill through the trailing edge of the lower spreaders and insert a nylon fairlead. From there, you can lead the wire straight to the chainplate, or inward to the mast base. The location along the spreader (or, the amount the upper is deflected as it passes the lower spreader) is a tuning decision- do you want to add a smidge of lower mast bend as you tension the uppers, or not?

Or use some 1/8" spectra instead of wire (won't chafe the aft side of the spreaders), lead the uppers through the deck at the mast base, attach both sides to a purchase or lever, and have the ability to tune the tip tension on the fly.

[jray]

Some of the information I got from C-Tech on this was to split the side stays at the lower spreader and join the top stays in there. They suggested ending the V1 with a toggle and putting two eye ends on the top of the two stays. An I bolt threaded into the end of the spreader can join the three parts. I can e-mail you the rough drawing if you would like. I like the fairlead idea Chad came up with myself. much easyer to tune.

[Kevin]

Death by snoo snoo has the uppers joined together above the lower spreader and then 1 wire down to the chain plate. Basically, you have to set your upper tension when you go to step the rig. I would think you want the wires to go through the spreader tip to allow the tension to base through the spreader. If you bolt to the spreader than it will have to flex with the changes in tension. I'm thinking you don't want that.

K.

[Chad]

That works if the intention is just to use the masthead wires as a sort of tip insurance, to keep the tip from going forward and inverting the mast downwind. If you want to tune the tip some, to adjust the point at which the tip begins to deflect and open the leech while sailing upwind, then the line needs to be adjustable. I'm also morally opposed to lines that can't be adjusted, but that may just be a character flaw.

[admin]

Does the wire chafe the spreader continuously or just when there is a bit of mast pumping (once the rig is raked a little less, to match your sailmaker's setting for prebend)?

If it's just occasionally and lightly then teflon tape might be a low-cost, K.I.S.S. solution.

seems like if you go to the fairlead solution, that is going to change the angle of deflection as you tune the uppers. Why not just wrap some teflon tape around the section of spreader where it chafes against the wire? Not sure of the longevity of the teflon tape against wire, but I've seen this stuff go thru an entire season of Asym gybes scraping across it on a luff foil with barely a mark on it. It ain't cheap but it's slippery as hell and may prevent the wire sawing thru your lower spreads this season. Then, over the winter build another set of spreaders for the D1's that are less swept.

I share your opposition Chad...having seen a guy have to go aloft after every race to tune non-continuous rod, what a PITA that is.

link to APS blog about "millionaire's tape" http://blog.apsltd.com/2009/06/wrap-it-up.html

[jray]

This is the simple drawing I got from C-Tech, I was told that Death by Snoo Snoo was rigged this way. They may have changed things now? I don't plan on using this system myself, likely hard to tune.

20100121102038302.pdf

[Chad]

If it's hard to adjust, it's unlikely to get adjusted. I'm pretty sure ya can't go up the rig on an i550, so you'd need to pull the boat down near the dock, where it would be pretty easy to tune. But if you're wrong on the set up, the only way to change it is to pull the boat over while on the water, and swim out to the spreader. Yeah, sounds fun!

Depending on the mast stiffness versus main sail head width, the masthead shroud may not need to be adjusted, in which case the DBSS system would be ideal.

My current layout which is still just on paper is to run the masthead shroud from the upper spreader, through a fairlead in the lower spreader at about the same distance as the length of the upper spreader, then to the mast base. Sort of like a diamond with a parallel bit in the middle. I'll also try bringing the shroud in to the root of the first spreader, as well as the tip to see what effect each set up has on mast ben as the tune changes.

I don't think the solution would be to increase the sweep of the spreaders, since that further restricts the ability to twist off the head.

[Chad]

Just ran across these pics at http://www.riggingnews.blogspot.com/

IMG_5189-1.JPG

IMG_5200.jpg

This is on a mini, and it looks he is doing the discontinuous-style adjusting at the upper end of the 2nd diagonal, which has its bottom end spliced into the vertical. This is a fairly shallow spreader angle rig with adjustable checkstays and runners though, so not much need to change the differential tension between D3 and D2. If it works out that the masthead shrouds CAN be set-and-forget, this is a very clean solution. I love seeing the stuff the mini guys do with their boat setups.

[Ron Bowman]

Thanks for all the help, guys. Great information.

Tim, your suggestion for just putting tape on the spreader as a chafe guard was my first thought and is what I did last season. Here is a link to one of Jeff's photos from the Epoxy Cup in Madison last year that shows white tape on the spreader and on the shroud where it rubbed on the spreader. https://picasaweb.google.com/jldalsin/2010I550NAChamp?feat=email#5521577934390815282 You can also see in that picture the overbend wrinkles in the sail. The wind was light enough for that event that I probably should have just removed the top shrouds and tuned the rig to have less prebend. Not an overall solution but would have worked for that event. I would prefer not having to make new spreaders. They are bonded in place and it would take a lot of work to rebuild them at a different angle. And Chad is right about how the swept back spreaders do poke the main when you ease the main or when the top twists off.

Keeping the solution simple is one goal on this, so long as simple works. I just want to support the tip of the mast when flying the kite. So Chad's suggestion to run the uppers through the tip of the lower spreaders seems like a good solution. Should I be concerned about how putting tension on the uppers will bend the mast in the middle since they would now run through the lower spreaders? Maybe the uppers don't have to be set so tight? The other suggestion you made, Chad, to put a nylon fairlead in the spreader, makes me wonder about how that might impair the strength of the spreader. My lower spreaders were made by C-Tech and are very light weight.

Jon, I like the suggested C-Tech solution but wonder about how you can tune a rig set up like that? Tensioning the shrouds will pull the spreaders down. This solution reduces the amount of cable used but if I'm reading the diagram correctly, requires four turnbuckles above the lower spreaders.

So after thinking about all of this, I'm inclined to just run the uppers through the tip of the lower spreaders and down to the deck to be adjusted at the deck with a turnbuckle.

Am I making a mistake? Why didn't others who went with two spreader rigs run the upper shrouds through the lower spreader?

Ron
Lunatic Fringe #108

[Chad]

356.JPG

Not sure which pic you linked to, but this one shows the geometry and the taped spreaders.

Pushing that shroud a couple inches out to the tip of the lower spreader should have negligible effect on your lower mast tune since it is such a small deflection. Your D1's have 10x as much leverage to counter this effect. You'll tune the effect out with your base D1 setting, and the only effect then will be from changes in the masthead shroud tension, which should be a positive anyway- as you add tension to the topmast, you'll probably want to increase lower mast bend at the same time. Indeed, increasing this synergistic effect is the reason to use a fairlead and then bend the shroud to the mast base.

I have the same spreader, and I wouldn't worry about drilling a +/- .5" hole in the trailing edge of the foil shape. The weak axis is up and down, so the top and bottom surfaces do the heavy lifting. If it made you feel better, wrap the TE with a 3" wide by 5" long piece of 6oz. cloth on the bias, before drilling the hole.

The only reason to stop the upper shroud at the lower spreader is to save the weight and windage of the lower 10-odd feet of wire. That's a worthwhile saving, if the consequences can be dealt with. If you're adjusting the topmast tension frequently, it's a bad idea. It takes very careful setup to get the discontinuous lengths just right to use the method in the C-Tech sketch. Yes. the spreader will deflect up and down a bit with rig tune, but if the lengths are setup right so that your base setting is with the spreader at its neutral height, the +/- .5" of adjustment won't be noticed by the spreader. (Go grab your spreader tip when the mast is down and pull up and down on it to get a feel for its comfortable adjustment range).