Tight Rig

[delevi]

I know this was discussed before, but I would like to get some opinions. I just bought a Loos gauge at WM to make sure my shroud tension was equal on both sides. To my surprise, the uppers were identical and the lowers were close. Just had to adjust one increment on the starboard side. Now my rig is super tight, which I think is a good thing, but I'm wondering if I’ve gone a bit overboard, particularly on the upper shrouds. The reason I did this is to get the forestay tight. My new jib has been experience much flutter, even with the cars all the way aft. I end up having to sheet it much harder than needed to get rid of the flutter. Having talked to the sailmaker, the advice I got was to tighten the furler halyard, take up some leech and foot line and tighten up the forestay. I did all this, but the only way to get the forestay tighter would be to tighten the upper shrouds, since my turnbuckle was already cranked down to the max to remove mast rake.

When I used the loose gauge, I saw 800 lbs of tension on the upper shrouds and 300 lbs on the lowers. Breaking loads on the 5/32 cable is around 3300 lbs, so I'm told. The question is, are the uppers so tight that they can either
1. damage the mast and/or spreaders
2. damage the hull
3. adversely affect sailing performance.

Look forward to your replies. Thanks.

Leon

[beene]

Hi Leon

I wonder if your "at rest" load being 800lbs is too high. Is there a way to calc the load increase at 30kts, since I know that is the wind you are looking for.

hmmmm.. guess we need an engineer

[Highlander]

I beleive your upper shroulds should be set at 15 percent of your shrould wire breakage point & the lower shroulds should just be set with just alittle less tension . I was at a sailing loft seminar this fri evening & thats what they told me
I think if I put 800# on my three sets of shroulds I'd have a banana mast
John

[Richard O'Brien]

I was hoping someone else would reply to your inquiry Leon. I can say that the first year ,2004, that I had my boat, I had my rig so tight that I had to use a come-a-long to fasten the forestay. I just assumed this would be better . I discovered a few too many spider cracks around the chain plates that fall, and since then over-corrected the opposite direction. You can't sail in stiff winds with a sloppy rig, and point very well. Now I'm hoping someone has found the right tension, or perhaps the only answer is a running backstay with two lines?

[Catigale]

800 is too high....working at 25% of rated sounds like it could be exciting..

[Frank C]

Early 26X owner, Bruce Whitmore, read Brion Toss' Rig Tuning Apprentice (book or video) and then wrote a digest for tuning the Mac rigs, which Heath published as a Featured Article (button left). After sailing his X for a few years, Bruce sold it and bought a heavier C&C for use on the Gt. Lakes. There's lots to read in the Featured Article, and lots more in Toss's book (guessing about one-tenth of Bruce's article excerpted below).

... Keep in mind, as Brion Toss says, tuning a rig is about "relationships". Each time you tension one shroud, you change the tensions on the other shrouds.

... First, overtensioning is bad (here's a case where more is NOT better). If your rigging is too tight, you will wear out your rig faster, and cause some nasty mast compression forces to build up. On deck-stepped masts, you can even do damage to your deck, especially if there is no compression post inside the cabin to support the mast compression forces. But on the other hand, ... your rigging is too loose, the mast will slop side-to-side from waves, sudden bursts of wind, etc., causing tensions to suddenly rise in the rig. This is called "shock loading". These shock loads can end up being higher than the designed loads, either weakening the rig or breaking it outright.

... Once you have the mast rake set for the desired angle, tighten the upper shrouds EQUALLY ON EACH SIDE (in SMALL increments) and tighten the backstay to induce mast bend to the desired amount. As you tighten the shrouds and backstay, sight up the mast to make sure it is straight laterally (side-to-side) and doesn't tip off one way or the other. Do this often (after each set of adjustments, i.e. adjust port upper shroud, then starboard upper shroud, & sight up the mast).

... Ideally, you will keep adjusting first the upper shrouds, then the lower shrouds. You will keep going until you have tension on your upper stays of about 15% of the breaking strength of the shrouds (check a West Marine or other catalog for specs on wire) and about 10% of the breaking strength of the shrouds on the lowers ....

[delevi]

Sounds like 15% uppers, 10% lowers is ideal, which translates to
500 lbs/ 300 lbs. Will give that a shot. Hopefully this rig with enough running backstay tension and having tightened up the furling halayard on the jib as well as the leech & foot lines will eliminate the flutter. Sailing Monterey Bay this weekend, so I'll report back on the progress. Forecast is light winds so I'm not sure how much of a test it will be for the jib, but I may just get to fly the kite instead

Thanks Frank.

Leon

[Night Sailor]

I guess I should borrow a loos gauge. I had tuned the rig loose like the owner's manual suggests, but found trouble in balancing the boat, or sailing with main alone. After replacing the linear toggles with turnbuckles, I got a nice tension on the furler, and a nice aft bend in the mast with about a 4 degree rake, and all shtrods are tighter than they have ever been. How tight? I don't know. I do know the boat now sails easily and well under all combinations of sail. Loose didn't work for me, tighter does. As a rough estimate, I can stand on the deck and at chest level pull the upper shroud in about 1.5 inches. the lower shrouds about 2 inches.

[Highlander]

I'd go with 15 percent on the uppers & 12 percent on the lowers first & try that 10 percent on lowers seems a little to low

John

[Moe]

I couldn't find it last night, but Bruce wrote in a later post that he found 15% and 10% too high for his MacGregor. Don T wrote that at some point not far over 300 pounds he saw the hull beginning to distort in the chainplate area.

I can't recall the exact numbers, but after taking all the adjustment out of the forestay to minimize the mast rake, we were down near the ends of the shroud adjusters, where the jumps from one pair of holes to the next resulted in a pretty large jump in tension. We wound up with the uppers at 300-330 pounds and at that point the mast had about 1.5"-2" of curvature. I can't remember the lower numbers, but 270 seems to stick in my mind.

I don't know of anyone else here running more than 330 pounds on the uppers. At least on the X, this would result in some serious mast curvature. This also puts considerable force on the spreaders.

Taking all the adjustment out of the forestay also resulted in our backstay being 1.5-2.0" too short to reconnect the adjuster halves. That's why we wound up with a 4:1 adjuster on it.

In the end, it isn't the tension pounds that matter, but how the boat sails and what the shrouds do when underway. 15 knots, or whatever wind speed you go to before reefing, is a good speed to judge this.

[delevi]

My problem is a bouncy forestay, even with it shortned to the end of the turnbuckle adjustment. I read some interesting things in the Loos Gauge manual:
paraphrasing

On a fractional rig with swept back spreaders, 20% of breaking strength is desirable on the upper shrouds. It is also imperative to have the rig tight enough so that the leeward shrouds never go slack. Otherwise, there will be shock loads as the boat pitches or rolls with the waves or sudden changes in wind velocity.

They also recommend approx 500 lbs of tension for the forestay. The 15%/10% rule applies on most masthead rigs, but upper shroud tension should be increased on fractional rigs to reduce forestay sag, even more so with swept back spreaders. They do say never to exceed 25%

I think I will test it at 650-700 lbs uppers and 330 lbs lowers... or as close as I can get.

[beene]

Leon

Do you use something like Bill's RAT to do your fine tuning?

G

[delevi]

Do you use something like Bill's RAT to do your fine tuning?

Exactly that. However, I have really stripped the tension adjustment on the RAT, so it's hard to get much power above 500 lbs. I use a vice grip, clamping to the end of the tension rod of the RAT. I plan to adjust the rig before breaking eveything down this Friday to go for a Monterey Bay sailing trip. I think I'll just use the mast raising kit to slack off the shrouds and adjust from there. This is what I ususally do when I can't budge the RAT and before I got the RAT. Unfortunately, it's time consuming. I may get turnbuckles at some point to replace the chain plates.

[beene]

Hi Leon

I have turnbuckles on my OTHER SAILBOAT and I have bent and replaced them more times then I care to mention. Every time I raise the mast they have the potential to get bent again. That is one thing I really like about the Mac, no turnbuckles to get bent.

G

[Frank C]

Suggested reading re shroud adjusters, an alternative to turnbuckles:
Stay Adjuster Alignment
Indexed Shroud Adjusters
Mast Rake?

FWIW, Sta-Master adjusters are even less prone to bending than Roger's gear ... $120, all four.
I have no relationship or interest in this product, except as a satisfied customer.

... I feel the Sta-Masters are one of the best mods I've done. They are clearly a vast improvement over verniers. IMO they're a significant improvement over conventional turnbuckles for several reasons:

• - they're indexed;
  - they're easy to adjust;
  - they are much less suceptible to bending damage;
  - even if accidently bent, seems they'll lose little strength;
  - seems to me that they're much more substantial than turnbuckles.

Here's a link to the original thread about the Sta-Masters,
Indexed Shroud Adjusters

Sta-Master Adjusters as Installed

Sta-Master Shroud Adjuster vs. Verniers


( Alt search terms stamaster, sta/master, Sta Master, footloop, foot loop, forestay sag)