Association Forum - Tuning the standing rigging

Assn Members Area · Join

Home.

Association Forum

Ships Store

Cruising

Racing

Technical Tips

Photo Gallery - New

Boat Search - Updated

Manuals & Brochures

Swap Meet

Links

Officer Flag Line & Staff

Bylaws & Constitution

Members Area

Join the Association

Notice:
The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.

Association Forum

Username:	Password:
Save Password
Forgot your Password?

All Forums

Catalina/Capri 25/250 Sailor's Forums

Catalina 25 Specific Forum

Tuning the standing rigging

New Topic

Topic Locked

Printer Friendly

Author

Topic

deastburn
Captain

Member Avatar

USA
334 Posts

Initially Posted - 07/14/2003 : 22:53:10

This is a rigging tuning question.

On my C25, I have always had the upper shrouds fairly taut, and the lower shrouds less so. I was on a friend's J30 over the weekend and I noticed his boat was tuned exactly opposite of mine--taut lower shrouds and slack upper ones.

Am I tuning correctly? One thing to consider is that the C25 has (of course) a masthead rig, while the J30 has a fractional rig.

Just wondering...

Edited by - on

Bill Holcomb
Admiral

Members Avatar

USA
769 Posts

Response Posted - 07/15/2003 : 10:17:50

You're doing it correctly for the C25. Other boats may have different needs - Your J30 friend may want more mast bend and maybe even to have the top of the mast flex to leeward in gusts.

Bill Holcomb - C25 Snickerdoodle #4839

Edited by - on

timpky
1st Mate

Members Avatar

USA
41 Posts

Response Posted - 07/15/2003 : 10:36:20

How do you know how tight is tight and loose is loose ? I find no prescribed settings in the owners manual and most posts that I have read on this forum use terms like tight and loose to describe the tension on the standing rigging. I purchased my boat with the mast already in place and I keep it in a slip, so I have not had to step the mast. At this point I have made no adjustments to the rigging. Should I have a Loos gauge ? If so are there prescribed settings for different shrouds ? Any advice from my saltier friends on this forum would be appreciated.

Tim Peoples
Sarasota, FL
78 Catalina 25 SK Hull #875

Edited by - on

OJ
Master Marine Consultant

Members Avatar

USA
4382 Posts

Response Posted - 07/15/2003 : 11:52:11

I use the Loos gauges and have had very good results. There are two different models though - standard and professional. Depending on which set you buy, the tension numbers are different.
Additionally, because of the two different size cables on the C-25 you are forced to buy both sizes of the Loos gauges <img src=icon_smile_sad.gif border=0 align=middle> .
There's also a procedure to follow when tensioning mast rigging. I do the lowers first followed by the uppers. The first time I adjusted mine I had the mast shaped like an "S." "Yes, 'S' for Steve I told the first mate."
Good luck.

Edited by - on

Steve Milby
Past Commodore

Members Avatar

USA
5909 Posts

Response Posted - 07/15/2003 : 13:06:41

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>On my C25, I have always had the upper shrouds fairly taut, and the lower shrouds less so. I was on a friend's J30 over the weekend and I noticed his boat was tuned exactly opposite of mine--taut lower shrouds and slack upper ones.

Am I tuning correctly?<hr height=1 noshade id=quote></BLOCKQUOTE id=quote>

The stainless steel cables that support our masts stretch. The longer the cable, the more it is able to stretch. Because the uppers are much longer than the lowers, I put a little more tension on the uppers, to take the extra stretch out of the uppers, and to make sure that the top of the mast doesn’t sag to leeward under load. The goal is to keep the mast in column and erect when under load. That doesn’t mean that the shrouds should be “bar-tight.” If you put too much tension on the shrouds, you can damage the hull structure.

The following is a procedure that I wrote when this subject came up earlier.

Mast Tuning

Before we discuss the processes that should be used in tuning your rig, let’s think about how each stay functions. Each stay has a specific purpose, to provide support from a specific direction, and to prevent the mast from bending in an improper direction or to an excessive extent. If your rig is properly tuned, the tightened backstay will pull the top of the mast aft. The headstay will limit the distance that the top of the mast can tilt or bend aft. The forward lowers will resist the pull of the backstay and prevent the lower part of the mast from moving aft. At the same time, the forward lowers will provide lateral support to the lower portion of the mast, to keep the lower part of the mast from sagging to leeward. The uppers will provide lateral support to the top of the mast, to keep it from sagging off to leeward. As the tension on the backstay adjuster increases, it will exert a downward force on the mast. The mast step and keel will resist the downward force on the mast. Since the mast can't move downward, to release the pressure, the mast will bow in the middle. Because the forward lowers are adjusted snugly, and the aft lowers are adjusted loosely, the lower part of the mast can only bend one way, i.e. forward. As the lower part of the mast bows forward, the aft lowers will become taut, and prevent the mast from bending so far out of column as to damage the mast. In order for the backstay adjuster to work properly, the stays have to be adjusted with differing tensions, so that they allow the mast to bend in the proper direction. If all the stays are snugged down to more or less the same tension in all directions, when you pull on the backstay adjuster, it won’t bend, because the stays will prevent any part of the mast from moving in any direction.

Begin tuning your rig by tightening the headstay turnbuckle until the headstay and backstay have little or no sag, but so that they are not bar-tight.

Next, loosen all your lower stays just enough to take the tension off them. Then, tighten the upper stays snugly by an equal number of turns on each side. Next, take your jib halliard, and use it as a measuring device (you might need to tie a piece of line onto it, to lengthen it), to make sure that the distance from the top of your mast to the chainplate for the upper stay on the starboard side of your boat is the same as the distance from the top of your mast to the chainplate for the upper stay on the port side of your boat. If the distance is not equal, adjust your upper stays until the distance is equal on both sides. That will ensure that your mast does not lean more to one side than the other.

Now, adjust your forward lower stays until the slack is just taken out of them. Then continue tightening them, alternately by an equal number of turns, until they are as tight as you can comfortably get them by hand. Then do the same with your aft lowers. Lie down on the foredeck, and sight up the mast, to see if it is straight. If so, then use tools to tighten each lower stay a little more, alternately by an equal number of turns, until the tension of the lower stays is snug, and equal all around. Sight up the mast again to be sure it is still straight. If it is not, then make such adjustments to the lower stays as are necessary to make it so.
Tighten the locknuts on all your turnbuckles, including the uppers, lowers, headstay and backstay. With these adjustments, your mast will not be perfectly adjusted, but it should be "in the neighborhood." Sail the boat, and observe whether it has excessive weather helm or lee helm. It will probably have excessive weather helm. If the boat has excessive weather helm, readjust all the stays so that the entire mast is tilted further forward. If the boat has excessive lee helm, readjust all the stays so that the entire mast is tilted further aft.

If you do not have an adjustable backstay, you are done. If you have an adjustable backstay, you have a little more adjustment to do. Make sure that the tension on the backstay adjuster is completely released. Then loosen the turnbuckle on the headstay until the headstay is slack. Next, adjust the aft lowers until they are slack. Then apply strong tension to the backstay adjuster. Adjust the aft lowers so that they just become snug when the backstay is tensioned. When you release the tension on the backstay adjuster, the aft lowers will become slack. When you re-apply the tension, the aft lowers will become snug again. When tension is applied to the backstay adjuster, the headstay should be taut. When backstay adjuster tension is released, the headstay should be very slack.
To increase the amount of mast bend, loosen the headstay and the aft lowers, but do not allow your eagerness for speed to cloud your judgment. Too much mast bend can result in a broken mast in strong, gusting winds.

Sail the boat again, and observe whether it has excessive weather helm when the backstay adjuster is fully tensioned. If the boat has excessive weather helm, then readjust all the stays so that the entire mast is tilted further forward.

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>How do you know how tight is tight and loose is loose ?<hr height=1 noshade id=quote></BLOCKQUOTE id=quote>

After you have tuned your mast, you should take her out for a test sail in strong winds, carrying as much sail as you can carry in that amount of wind. When you are beating to windward, the leeward shrouds should remain just taut enough so that they are not swaying freely. If the leeward shrouds are swaying freely, then you should tighten them all a turn or two. To avoid overtightening them and taking a chance on doing structural damage to the boat, I would rather have them a tiny bit loose. In other words, your shrouds are too loose if the leeward shrouds sway freely when the rig is under stress.

The only shrouds that can be loose are the headstay, the backstay and the aft lowers, if you have a backstay adjuster, as previously discussed. It is okay if they sway freely when there is no tension on the backstay adjuster, so long as they become taut when full tension is applied to the backstay adjuster.

Some sailors on this forum and elsewhere advocate having the leeward shrouds so loose that they sway freely. I have seen some very knowledgeable sailors do that, but don't think the majority would agree, especially in strong winds. If the rig is too loose, it can move around too much in strong winds, creating a risk of failure.

You can tune your rig using a loos gauge, but as you have seen, there are no generally accepted loos gauge standards for shroud tension on C-25's, so, if you accept someone else's recommendations, that is only that person's opinion, and that person might be tuning the rig for racing, and not for general sailing purposes.

My method relies on a performance standard, and personally, I think that standard is good for racing as well as for general sailing purposes. You test-sail the boat and watch how the shrouds are actually performing. You watch how taut the shrouds are when the rig is sailing under stress, and then adjust the rig so that you eliminate excess slack. The whole purpose of rig tuning is to ensure that the mast is erect, in column, securely attached to the boat, and adjustable within reasonable limits. By test-sailing the boat, you can see whether that is the case, and you can adjust it further until it accomplishes all those purposes.

Steve Milby "Captiva Wind" C-25 T/FK #2554

Edited by - Steve Milby on 07/15/2003 18:03:35

Edited by - on

Topic

New Topic

Topic Locked

Printer Friendly

Jump To:

Association Forum

Notice: The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.