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Catalina/Capri 25/250 Sailor's Forums

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mast tuning help

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clayC
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USA
207 Posts

Initially Posted - 04/04/2008 : 09:32:14

So, we got a new main this year (yes!!) and now it really matters what our mast looks like. I went step by step using the mast tuning tips in the tech forum but I still have a mast that is pretty crooked. first thing I found is that I have a rake about 8 inches aft, that I cant get out. I have ended up with 1/2 of threads on my rear stay and the front tightened all the way. when I look up the kerf I have a bow in the middle (forward) and a bend it the top have to port. I hate to just crank on my lowers, I am afraid of getting the whole thing to tight.

Any advice?
Thanks,
Clay C

Kamalla 1980 C25 SK/TR

Edited by - on

Steve Milby
Past Commodore

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USA
5902 Posts

Response Posted - 04/04/2008 : 12:29:05

These instructions are for a boat without a backstay adjuster.

The first thing you need to do is raise the mast with all stays and shrouds adjusted loosely, but secure enough so that the mast won't fall.

The first adjustment should be made to the upper shrouds. Adjust them so that the mast is erect laterally (i.e., not leaning either to port or to starboard.) When it's erect, snug the uppers down until they start to become taut, but not bar tight. For the moment. all adjustments made to the turnbuckles should be made by hand. Don't use a tool, such as vise grips or a screwdriver. When you're snugging them down, alternately tighten the turnbuckle on each side by an equal number of turns. At this point, the uppers should not be snugged down so tightly that they cause the mast to bow in any direction. The mast should be in column.

Next, adjust the headstay and backstay so that the mast rakes aft about 2". You can use the main halliard to measure the approximate amount of rake. When the mast has the correct amount of rake, start tensioning the headstay and backstay by alternately tightening the turnbuckle on each by an equal number of turns, until they are both snugged down, but not bar tight. The mast should still be in column, without any appreciable bow in any direction.

Now, alternately adjust all four lower shrouds by hand until you have taken all the slack out of them. Except for the slight 2" rake aft, the mast should still be erect and in column.

If the middle section of the mast bows forward too much, then ease each of the forward lowers by a turn or two, and tighten the aft lowers the same numbers of turns, until the mast is erect and in column. If the middle of the mast bows aft too much, then ease the aft lowers and tighten the forward lowers. If the mast bows to port, then ease the port lowers and tighten the starboard lowers by an equal number of turns, and visa versa if the mast bows to starboard.

When all adjustments have been made, use an appropriate tool to tighten the headstay, backstay and uppers by about 2 turns each, and use a tool to alternately tighten each of the lowers by about 1 1/2 turns each.

Lock all the turnbuckles in place with lock nuts or rings, or whatever you use for that purpose, and take the boat out to sail. When you're beating to windward in 10-12 knots of wind, check the tension on the leeward uppers and lowers. They should not be slack. If they're slack, then alternately tighten each shroud by an equal number of turns just enough to eliminate the slack, but no more. Also, when the mast is under load, it should remain in column and erect, except for the 2" rake. If it isn't, make the appropriate adjustments to the lower shrouds to correct it.

The object is to adjust the rig so that the mast is secure, and so that it doesn't move fore and aft or to one side or the other as it tacks from one side to the other, but the stays should be no tighter than is necessary to achieve that. They should never be bar tight.

If the boat has too much weather helm, you can reduce it by reducing the amount of rake in the mast, but remember that you only have a couple of inches to play with, and you don't want it perfectly erect. You always want <u>some</u> rake.

These directions should get the rig fairly close. Ask an experienced local sailor to look at it for you. In time, you'll develop a sense for the correct amount of tension.

One other thing. If you can't adjust the headstay and backstay enough to establish the correct amount of rake, check back with me. There might be a way to correct that without replacing the headstay and backstay.

Edited by - on

Frank Hopper
Past Commodore

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Pitcairn Island
6776 Posts

Response Posted - 04/04/2008 : 12:29:29

Which pin at the mast head are you using? You should be using the one close to the mast, the outer pin is for a spinnaker block. Your forestay may simply have stretched over the years, new ones are surprisingly cheap. Is your forestay in the forward hole of the bow stem fitting? If you are bowed forward then your forward lowers are too tight. A little forward bow is actually a good thing. It takes the pocket out of a stretched out main and helps the backstay bend the mast properly. Do you have a split backstay? If so the bow helps. A masthead rig with dual lowers does not respond to backstay adjustment very well. An adjustable backstay can shape a mainsail by causing the mast to bow, taking the pocket out of the main and flattening it, an adjustable backstay can also "harden" the forestay to help reduce forestay sag in high wind, (which helps flatten the sail). All that said, with a new main you are not dealing with stretched cloth so this year forward bow would only help the backstay bend the mast.
I set my rig up tight and only use my backstay adjuster to harden the forestay in high wind. This is because I sail in a lot of high wind and am uncomfortable with slack leeward stays and shrouds. Loos, the gauge people, make the argument that a tight balanced rig spreads the loads under all conditions and is the proper way to tune a rig. A hard rig is a flat rig so it is a slow rig, I accept that trade off.
Do you have a gauge? I think my uppers are at 28 and my lowers at 23 on which ever Loos I have.

Edited by - on

clayC
Navigator

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USA
207 Posts

Response Posted - 04/05/2008 : 11:47:32

Thanks guys.

I have a split back stay and double head stays. We are headed down to the lake now and give your suggestions a go. I will let you know how it goes.

Thanks again
Clay C

Edited by - on

Steve Milby
Past Commodore

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USA
5902 Posts

Response Posted - 04/05/2008 : 15:52:52

It's too late to help now, because you're undoubtedly on the way to the lake, but the fact that the headstay turnbuckle is tightened all the way, and the backstay turnbuckle is not, can be fixed.

Tie pieces of line to your jib halliard and your main halliard to extend them. Then tie the jib halliard to a bow cleat and tie the main halliard to a stern cleat, to support the mast.

Now, completely unscrew the turnbuckle from both the headstay and the headstay tang. Then re-start the turnbuckle onto both the headstay and the headstay tang simultaneously.

Next, do the same thing with the backstay. That should give you plenty of room to adjust them both enough to tune the rig.

It's possible that the stays could have stretched so much that the rig can't be tuned correctly anymore, but I stressed my rig hard and never replaced the headstay or backstay in 23 years, and still had plenty of room for adjustment. I've never seen any indication that they can stretch that much from use. If they can't be adjusted, I think it's more likely that the headstay and/or backstay were replaced with improperly sized stays.

Sorry I didn't think of this before you left for the lake.

Edited by - on

clayC
Navigator

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USA
207 Posts

Response Posted - 04/15/2008 : 17:49:26

Its been snowing most every day since I asked this question, so I have yet to do any work.I have an interesting rig in that i have twin head stays. I don't know why, racing I suppose. I have tightened those as as much as I can and still have quite a bit of rake. I came back to this post to print off these instructions and give it another try. Our slip neighbor that just launched I think has a loos gauge. maybe its time for a rigging update.

either way I will let you all know,

Thanks again,
Clay C

Edited by - on

clayC
Navigator

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USA
207 Posts

Response Posted - 04/15/2008 : 18:00:14

my head stays

Edited by - on

Steve Milby
Past Commodore

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USA
5902 Posts

Response Posted - 04/15/2008 : 18:31:36

I can't tell for sure from the photo, but your uppers might be too taut. Your lowers are definitely out of adjustment. It looks like you need to ease the starboard lowers a tad and tighten the port lowers. The middle of your mast is bowed out to starboard.

From the photo it looks like your best bet would be to loosen everything and start over. As I described in my earlier post, adjust the rig from the top down. Do the uppers first, then the headstay and backstay, and finally the lowers.

I wouldn't sail it in strong winds until it's tuned correctly. The mast is far enough out of column that it could break in strong winds.

Edited by - on

Frank Hopper
Past Commodore

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Pitcairn Island
6776 Posts

Response Posted - 04/16/2008 : 09:44:28

Clay, you have the old bowstem fitting which I think should be upgraded. I would toss the dual headstay dealio. The new bowstem fitting will make the rig stronger and get you an anchor roller to boot.

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Nautiduck
Master Marine Consultant

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USA
3704 Posts

Response Posted - 04/16/2008 : 10:38:56

Frank is right. If you are not going to use those dual headstays you'd be better off going with the conventional setup.

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