Sideways Bent Mast

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Dimitri-2000X-Tampa
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Sideways Bent Mast

Post by Dimitri-2000X-Tampa »

I decided to fiddle with my rigging today and I swear, I am this close to hiring a professional rigger to just come and "upgrade" my rig.

Ever since I got the boat, I had noticed that slot adjuster for one of the lower shrouds was taken in a lot more than the other side. I always thought that this was odd, but I measured the distance from the mast to each chainplate and it was the same (measured again today) so I just concluded that one of the wires must be shorter than the other and everything is cool.

But today, I sight straight up the mast and I notice a significant (probably 4-6 inches) sideways bend in the middle of the mast (close to the lower shrouds). It pulls to the starboard side which is the same side as the backstay is attached to. Surely the backstay or upper shrouds can't be causing this bend, it must be the uneven lower shrouds, don't you think? But why would the mast to chainplate length be symmetric then?

Those of you who have the split backstay mod, do you find that your mast used to pull more to one side (or cause a kink) before you did the mod?

When I hang my halyard from the top of the mast, it comes down a good 18 inches to the back of the mast base, that sure seems like a hull of a lot of rake/bend. I have my backstay all the way loose and my forestay turnbuckle tightened all the way. Sounds like I should just hire a rigger to do a split adjustable backstay, shorten the forestay by 3 inches, get all the shrouds right and upgrade the outhaul internal to my boom. What do these people list their businesses as in the "yellow pages"?
Billy
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Post by Billy »

Dimitri, the 18" may not all be contributed to rake. Is the boat sitting level with the stripe? If you, rather the boat, is heavy in the aft, then the mast will appear to have more rake than actually exists.
Frank C

Post by Frank C »

Dimitri,
Sounds strange, indeed. Suppose if the mast is tilted toward one side, and has a big whoopee in it below the spreaders .... sounds strange. Guess you've already looked in "Featured Articles" for the piece on tuning the rig, and don't wanna go there?

Search Yellow Pages for a "Rigger" or maybe "sail rigging." I use www.yp.yahoo.com .

BTW, No - I never had the factory backstay cause anything like you've described, but I added split adjustable because it just seemed strange to have it only on starboard.
Last edited by Frank C on Tue Jul 06, 2004 11:23 am, edited 1 time in total.
Tripp Gal
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Post by Tripp Gal »

Hi Dimitri.

So when you sight up your mast from the mainsail luff you are seeing a "C" shape correct?

First part is:

1. Do you keep your mast stepped? If no, there is a good chance that the mast got bent somehow. To check, take the mast off and lay it down and check it.

2. If you have uneven tension on your uppers and lowers you will see all sorts of curves in the mast. Ease off the uppers and lowers and let the rigging ease to fully slack. Then, tension evenly p/s, then uppers/lowers.

If that just has you daunted, then I am sure someone here can help you find a good rigger in your area.
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craiglaforce
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Post by craiglaforce »

I would install turnbuckles to replace the vernier index adjusters, then loosen everthing, make sure the mast is back to normal and start to slowly tighten everything. Uppers first and tightest (maybe around 250 lbs) with the lowers tightened just enough that the downwind shroud doesn't go floppy when on a hard tack. I would certainly give the B. Whitmore article a read. I never measured my rigging tensions, other than feeling the shrouds. When they were pretty durn tight I figured that was enough.

The backstay does not cause any problems for me. I don't tighten it that much anyway, just good and snug to where you can just feel that it bends the mast a tad. The backstay pulley mod is a neat idea in that it lets you tweak the mast bend to adjust mainsail shape while underway. But I opted for simplicity and just adjust the backstay turnbuckle to a medium point and leave it alone.

I think mast rake is correct when the boat is still well behaved at the helm in 20 knot winds. if it is trying to round up and pull the wheel out of your hands, then it has too much rake. If you can let go of the wheel, go below and make a sanwich and the boat stays on course on a tack then Its just about perfect, although a touch of weather helm is supposed to be good in case you fall overboard so the boat will not sail over the horizon wihtout you. (a somewhat moot point if the autopilot is engaged). It is also supposed to help the boat point a tad higher.

The turnbuckles were easy to install. Open body type with toggle jaws fit right into the existing loops and the venier things took just a few seconds each to cut off with good sized bolt cutters. I replaced them one at a time on a calm day and didn't even have to take the mast down. I did tie the jib halyard to the side I was working on to help support the mast while making the changes.

Seems kinda silly to hire a rigger on a little boat like this and somewhat counterproductive. (you may want to keep tweaking the tuning as the season wears on and you want more or less tension or rake or whatever.)
If you think the rigger had some majic touch when he set up the boat then you may be reluctant to make needed changes later. But I guess it depends on what you are comfortable doing.
Good luck
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Dimitri-2000X-Tampa
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Post by Dimitri-2000X-Tampa »

Thanks for all the good advice. I did store the mast leaning in the crutch (but still attached to the step) for about 6-7 weeks recently. Seems to me that this would have bent it foreward or backwards and not sideways though.

I guess I was just figuring that a professional rigger could not only do the swaging required to modify the forestay and backstay, but could also get everything perfectly tuned up so that all I would have to do is maintain it afterwards. Maybe I was just in a bad mood after messing with the furler, forestay, and turnbuckle for a couple hours. :x Guess I should give it one more try.

I'm also concerned about the top of the forestay connection. I've read in some old posts, that the bolt used is inadequate and that perhaps the block for the jib halyard is in the wrong place. When I am using the jib halyard with the mast raiser, it is very difficult to unfurl the headsail because the top of the furler rubs on the block and halyard. I need to look in the manual and see if it shows the right way to rig that.
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Jack O'Brien
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Tuning Rigging

Post by Jack O'Brien »

Assuming one starts with a straight mast, if one follows the Mac Manual instructions, and USES A LOOS TENSION GAUGE, it is a no-brainer. The Mac shroud adjusters are manageable with a couple screwdrivers and temporary small bolts & nuts but easier with the tool Bill has at Boats 4 Sale. Drop a plumb bob on a string from the mast top to measure staightness/backbend, list and rake. Level the boat first. Measure rake versus deck top at the mast step. I have 200 lbs. tension in all 4 of my shrouds. 12' of upper shroud to spreader tip.

Loos & Company, Inc. Tension Gauge Standard Model, Part No. 91 (lbs.) for cable sizes 3/32", 1/8", 5/32". 941-643-LOOS or 800-321-LOOS
Frank C

Post by Frank C »

Dimitri-2000X-Tampa wrote: . . . I guess I was just figuring that a professional rigger could not only do the swaging required to modify the forestay and backstay, but could also get everything perfectly tuned up so that all I would have to do is maintain it afterwards. . . .
I think it's a great idea to just hire a rigger, and watch, and learn.

I had a rigger duplicate my forestay, just 4 inches shorter. That was about $50, but he didn't climb onto the boat, strictly my installation. Eric Lowe shortened my backstay (reswaging 6 or 7 feet shorter) and I added the port-quarter tab and rigged my adjustable split down to each aft-quarter.
Dimitri-2000X-Tampa wrote: . . . I'm also concerned about the top of the forestay connection. I've read in some old posts, that the bolt used is inadequate and that perhaps the block for the jib halyard is in the wrong place. When I am using the jib halyard with the mast raiser, it is very difficult to unfurl the headsail because the top of the furler rubs on the block and halyard. I need to look in the manual and see if it shows the right way to rig that.
I had the same problem ... interference between jib block and furler cap. You can easily fix that one when the mast is down, regardless of changing forestay or tuning. On my 2000, the jib block was at the end of a 4" strap that was carried by the forestay pin (actually, the factory uses a 1/4" bolt, not a clevis pin). Simply remove the strap from that pin and reconnect the strap where a mast thru-bolt attaches the forestay hound. Now the jib block will reside about 1.5" farther outboard from the furler cap, and a few inches higher. You can replace the factory bolt at top of the forestay with a real 1/4" clevis pin at the same time.
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Dimitri-2000X-Tampa
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Post by Dimitri-2000X-Tampa »

So I take it that a 1/4 inch clevis pin has a higher sheer strength than a 1/4 inch bolt?

I did get the kink out of my mast this morning. The starboard lower shroud was just too tight. I left the upper shrouds alone as they seemed good, but now although the mast is straight, the lower shrouds are a bit loose. This does seem to take out a bit of the rake/bend versus when the lowers are tighter. I guess the solution is to get the Loos gauge and special tool. I think I've seen a tool advertised at BWY's site too.

I guess I'm definitely going to get a block for the backstay, and also uprade the outhaul, but I'm still not sure whether the split backstay mod is worth the time. I'm also going back and forth in my mind regarding the forestay. Is it easier/better to get a new shorter forestay, or is it better to use the existing one and drill a new hole in the mast further up?

With the shorter forestay, seems like you have to cut the furler...will the Genoa still fit, seems like it could be kinda tight? With raising the forestay hound, I wonder if it is compromising the design strength of the mast seeing as the countering pull from the upper shrouds will now be lower than the pull from the forestay?
Frank C

Post by Frank C »

Dimitri-2000X-Tampa wrote:So I take it that a 1/4 inch clevis pin has a higher sheer strength than a 1/4 inch bolt?
Yeah, cut threads into a 1/4" clevis pin and it loses a bunch of sheer strength. Your forestay hound is still attached to the mast with just a mast thru-bolt, but I think it's larger, maybe same as the mast pivot bolt (5/16?).
Dimitri-2000X-Tampa wrote:I did get the kink out of my mast this morning. The starboard lower shroud was just too tight. I left the upper shrouds alone as they seemed good, but now although the mast is straight, the lower shrouds are a bit loose. This does seem to take out a bit of the rake/bend versus when the lowers are tighter. I guess the solution is to get the Loos gauge and special tool. I think I've seen a tool advertised at BWY's site too.
I bought a Loos gauge from West Marine (very nice to have), and I'd also recommend the BWY tool but I don't have it. The gauge reads on an index scale for any of three different wire sizes. You need to refer to a separate list to know what tensions you're applying. Remember that the four shrouds are 5/32" and the two stays are 1/8".
Dimitri-2000X-Tampa wrote:I guess I'm definitely going to get a block for the backstay, and also uprade the outhaul, but I'm still not sure whether the split backstay mod is worth the time. I'm also going back and forth in my mind regarding the forestay. Is it easier/better to get a new shorter forestay, or is it better to use the existing one and drill a new hole in the mast further up?
You can shorten the backstay yourself with a hand swaging tool, and you'll never bother with the Loos gauge on it - very light tension on the backstay. If you decide to reduce rake, you'll almost certainly find the backstay too short (no matter if you cut the forestay or raise the hound). You need to get a longer backstay, or add a turnbuckle, a stainless strap, or simply insert an adjusting tackle. You can always decide to split the backstay at a future date - you can just leave the stb attach for starters.
Dimitri-2000X-Tampa wrote:With the shorter forestay, seems like you have to cut the furler...will the Genoa still fit, seems like it could be kinda tight? With raising the forestay hound, I wonder if it is compromising the design strength of the mast seeing as the countering pull from the upper shrouds will now be lower than the pull from the forestay?
I took careful note of the furler before shortening the forestay. There was plenty of surplus wire on my rig, but I did cut the furler foil by about four inches. (But, of course, be certain that your foil is long enough to provide luff tension). Lots of owners have attached the hound just 4 or 5 inches higher. It seems the mast is ample to handle the added stress, but wanted to avoid that issue, and also avoid another hole through the mast.
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Jack O'Brien
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Backstay

Post by Jack O'Brien »

I removed the stay adjuster from my backstay and swaged on a thimble. Swaged a pelican hook like my lifelines have to a short pendant on the backstay chainplate. Gives about 2" of adjustment. Makes it very easy to disconnect the backstay for mast raising, bimini movement, etc. I have the bimini feet on tracks and when fully back and down it is behind the backstay. Makes it easy to board at the stern and/or raise the helm seat.
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Dimitri-2000X-Tampa
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Post by Dimitri-2000X-Tampa »

I finally got around to inspecting the forestay attachment point up on the mast and sure enough, the 1/4 inch bolt that is holding the top of the forestay and the jib halyard block is somewhat bent. I've ordered a 1/4 X 1 & 1/4 clevis pin that I hope is long enough to replace the bolt. Seems like that is the longest 1/4 inch pin that sailnet stocks. I doubt that the mast raiser could have bent it, seems more likely to have been the turnbuckle. Seems like I could have bent a clevis pin just as easy, afterall, its bent in the middle where there are no threads and the thickness should be the same as a clevis pin.

Regarding moving the jib block to the side of the mast, I did look in the manual and it does show it attached at the same point as the forestay. At that point, the load is transferred to both sides of the mast where it is bolted through. If you move the block to one side of the bolt, doesn't it introduce a bit of a twisting moment to the mast when you torque that thing real hard with the mast raiser? I'm a bit hesitant to move it at this point.

Still haven't decided whether to put a new hole in the mast to raise the forestay attachment point, or whether to get a new shorter forestay. And there has been some disagreement lately about whether to up the size to 5/32 which I would have thought was a no brainer previously. Chances are I'll do nothing for now since my forestay is still in good shape with no bad strands, etc. Maybe when the higher wind season hits, I'll get motivated again.
Frank C

Post by Frank C »

Dimitri-2000X-Tampa wrote: .... Regarding moving the jib block to the side of the mast, .... If you move the block to one side of the bolt, doesn't it introduce a bit of a twisting moment to the mast when you torque that thing real hard with the mast raiser?
It never occurred to me since the jib halyard was idle due to the furling system. I completely forgot about the loads when raising the mast. Your point is well-taken, and I don't think it's such a good idea. I've already bought the little brake-winch for the M-style mast raiser. The incentive is that much greater to implement it.
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