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Loose aft stay.

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BCain
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USA
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Initially Posted - 04/08/2002 : 10:38:56

OK, having read all the thread on mast tensioning, I now have a problem. No matter how I tension my shrouds and stays, with the mast in line and plumb, my aft stay is very loose. Am I doing something wrong or is the stay stretched? It dosen't appear to make much difference because it tightens when I am going downwind, but, on any other tack it resembles a topping lift.

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Bill Holcomb
Admiral

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Response Posted - 04/09/2002 : 09:52:58

If the mast is plumb, then it sounds like your backstay has stretched. When you go downwind, the backstay gets tight because the top half of your mast probably is bending forward......loosening the forestay. The two upper shrouds and the combination of the forestay and backstay all need to have tension to keep the top of the mast from wobbling around. You probably need a new backstay.........or shorten the backstay you have and install an adjustable backstay system.

Bill Holcomb - C25 Snickerdoodle #4839

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Steve Milby
Past Commodore

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Response Posted - 04/09/2002 : 11:00:21

Over the internet it is hard to be sure what is the exact cause, but someone who can walk around your boat and look at it should be able to figure it out fairly quickly. The likelihood is that it can be corrected by making adjustments. If you have another C-25 sailor in your marina, ask him/her to take a look at it and help you adjust it. If not, then ask any other experienced sailor.

In your query, you mention that your mast is "plumb." Your mast does not have to be plumb. If you used a plumb bob or a bubble level to determine whether your mast is plumb, then that might be the problem. You don't want your mast to lean more to one side than the other, but it is o.k. if it tilts fore or aft. If the boat is leaning to port because your golf clubs are stowed in the portside locker, a plumb bob hanging alongside the mast will indicate that the mast is leaning, even though the mast might be in perfect adjustment. A plumb bob measures the orientation of something in relation to the earth, which is fixed. A boat that is afloat is not fixed in relation to the earth. It rocks and rolls.

Begin by loosening all your lower stays just enough to take the tension off them. 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 a point on the starboard side of your boat is the same as the distance from the top of your mast to the same point 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.

Next, attach a line to your jib halliard, and tie it securely to your bow pulpit, taking out any slack in the line. Then tie another line to your main halliard, and tie it securely to your stern pulpit, taking out any slack in the line. Those lines will temporarily hold your mast up while you adjust your headstay and backstay. If you have a backstay adjuster, release any tension on it.

At this point, it will help if you have an extra pair of hands to help you. Now, completely remove your headstay turnbuckle barrel, being careful not to lose any parts. Start threading the turnbuckle barrel back on to the screws at both ends, by equal amounts. Stop when you have it threaded on at both ends by two or three threads. Next, do the same thing with the backstay turnbuckle. Now, start alternately tightening your headstay turnbuckle by 10 turns, and then tightening your backstay turnbuckle an equal number of turns, until both the headstay and backstay feel fairly firm, with very little sag. By making that adjustment, you ensure that there is room in the turnbuckles to adjust the fore-aft tilt of the mast, as necessary.

Now, adjust your forward lower stays, 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. Following the recommendations in the previous thread on mast tensioning, you can adjust the fore-aft tilt of the mast further, to minimize weather helm or eliminate lee helm.

If you follow the above suggestions, and if the headstay and backstay are standard lengths, then there should be enough adjustment in the headstay turnbuckle and in the backstay turnbuckle to take the slack out of the headstay and backstay. If the above suggestions don't solve your problem, then either your headstay or your backstay might have been replaced with one that is too long. In that case, you should consider replacing one or both of them. It is very unlikely that your stays have stretched enough to cause your problem.

From your description, it sounds like you have a large amount of movement in your mast. I hate to say this, but you probably shouldn’t sail it, particularly in strong spring winds, until the problem is corrected. The good news is that you can probably correct it, except for fine tuning, in an hour or two.

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

Edited by - on

Derek Crawford
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Response Posted - 04/09/2002 : 11:52:12

Steve - now I'm even more convinced that you should write a book <img src=icon_smile_approve.gif border=0 align=middle>
Derek

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dlucier
Master Marine Consultant

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Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 04/09/2002 : 13:51:00

Steve,

I, too, defer to your knowledge of rig tuning and I intend to refer to this guide you have written when I tune my rig. I do have a question though concerning mast rake. In a previous thread, we talked a little about this and I was still uncertain as to if and/or how much mast rake I should have, so I called Catalina Yachts. I talked to a technical support person(couldn't get Frank) about mast rake. He told me that Catalina Yachts, "does not recommend any mast rake on the 25, only prebend".In your post, you state,

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote> "Your mast does not have to be plumb. If you used a plumb bob or a bubble level to determine whether your mast is plumb, then that might be the problem....it is o.k. if it tilts fore or aft."<hr height=1 noshade id=quote></BLOCKQUOTE id=quote>

Now, I agree with your assessment that a plumb bob or level will not be accurate if the boat itself is listing, pooped,..etc.,but from all of the reading I've been doing lately, I believe that you should bring the mast into plumb, in relation to the water surface, as part rig tuning. In most tuning guides, it appears that before you begin dockside tuning of the rig, you need very calm flat water, little to no wind, and a properly balanced boat. On naval ships, there is a device called a "Master Reference Plane" that is located down in the bilges of all modern vessels. This MRP is an extremely flat and precise round slab of metal, a couple of feet in diameter, from which all radars, gyroscopes, and anything else that must be "in column" are calibrated. On our boats, that master reference plane is the "waterline stripe" (We will go on the assumption that this stripe is accurate and wasn't painted by BillyBob after a night at the tavern). If the boat is balanced correctly, the waterline stripe should be even as you look around the hull(redistribute weight in the boat if necessary). If the boat is balanced correctly and sitting in calm water with no wind, you can now use a plumb line, or even better a post level, to plumb the mast before you start tuning the rig.

Don Lucier, Northstar
C25 SR/FK

Edited by - on

Derek Crawford
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Response Posted - 04/09/2002 : 15:22:00

Also, a C22 is tuned much differently than a C25. If the C22 does NOT have a split backstay, then 8" of masthead rake is correct, with some pre-bend built in. If it DOES have a split backstay (with adjuster) then, like the C25, it doesn't need more than 2" rake. (This comes from a C22 Natl.Champion...)
Derek

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dlucier
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Response Posted - 04/09/2002 : 15:30:53

What boat are we talking about here, C22 or C25? I thought we were talking C25.<img src=icon_smile_question.gif border=0 align=middle>

Don Lucier, Northstar
C25 SR/FK

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Derek Crawford
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Response Posted - 04/09/2002 : 19:03:17

Sorry Don <img src=icon_smile_sad.gif border=0 align=middle> It was on another post where someone mentioned the 8" of mast rake on a C22 - I guess I screwed up again...but the point is that the amount of mast rake DOES depend on whether you have a single backstay or a split w/adjuster, either on a C22 or a C25.
Derek

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Mark Maxwell
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Response Posted - 04/09/2002 : 19:57:52

I'm curious, how does the boat know if the masthead is raked back 8" by a split stay or a single stay? Isn't the rake fore or aft used simply to balance the helm or aid some in pointing to weather? Basically just a tool to shape the sail and move the CE?

Mark-
<img src="http://personal.jax.bellsouth.net/jax/l/c/lchaplin/unkarock/usflagwav.gif" border=0>
'Impulse'
C25 #533 DINN/FIN ~_/)~

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Bruce Baker
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Response Posted - 04/09/2002 : 20:06:42

I guess my question is somewhat related to this thread. I just bought my boat ('83 Catalina 25, swing keel) from a broker who can't answer my questions. The backstay arrangement in your online users' manual shows dual backstay chainplates with a yoke-type tensioner arrangement. However, my boat has only one backstay chainplate on the port side. It's very clear that there was never a similar chainplate on the starboard side. What's the deal here? It looks like when I put the mast up, it will be drawn a few degrees to port.

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dlucier
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Response Posted - 04/09/2002 : 20:14:16

Bruce,

Apparently the adjustable backstay(split) was an option. The Catalina Direct handbook does have a retrofit kit to convert to a split adjustable backstay with an 8:1 purchase($299.00). See page 4.34 of the handbook.

Don Lucier, Northstar
C25 SR/FK

Edited by - dlucier on 04/09/2002 20:26:01

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John Mason
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Response Posted - 04/09/2002 : 21:01:32

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>I'm curious, how does the boat know if the masthead is raked back 8" by a split stay or a single stay? Isn't the rake fore or aft used simply to balance the helm or aid some in pointing to weather? Basically just a tool to shape the sail and move the CE? <hr height=1 noshade id=quote></BLOCKQUOTE id=quote>

I think you're right, the difference (8" vs. 2") is about moving; the split stay can and the single can't. Set up the split (adjustable) at 2" and you can tension it to 8" when you need to, but if you can only set it once (when you tune it - on the single non-adjustable), maybe Catalina figures 8" is the best fixed position.

John Mason - Ali Paroosa
1982 - FK/SR #3290

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Steve Milby
Past Commodore

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Response Posted - 04/09/2002 : 21:10:08

Don,

Words are an imperfect way of communicating, because the same word can mean something different to each of us. I suspect that when the Catalina Rep said the company "does not recommend any mast rake on the C-25," he probably meant that the mast should not be tilted forward of vertical. When I said "it is o.k. if (the mast) tilts forward or aft," I did not mean to suggest that it should be tilted forward of vertical. What I meant is that there is a certain amount of latitude within which you can adjust the mast fore and aft. By adjusting the mast within that range, you can vary the amount of weather helm. The range of adjustment is really just a few degrees.

The problem I have with using a plumb bob is that, on a sailboat there are too many variables that can invalidate its readings. If a little wavelet rolls under the boat, or the wind blows, or if you simply shift your weight from one foot to the other, the plumb bob can start to oscillate. What you are really trying to determine is whether the top of the mast is equidistant from the same point on opposite sides of the boat. If it is, then you know that the sails will set and balance the same, regardless of whether you are on port or starboard tack. A plumb bob isn't the most accurate way of determining that, because it allows for too many variables.

If you measure the distance by using the jib halliard, there are not many variables that can cause an inaccurate result. The size and shape of the boat doesn't change, the height of the mast doesn't change, and halliards are expressly manufactured to be low-stretch.

I have two problems with using the waterline stripe as a reference, to determine whether the boat is floating correctly on her lines, so that you can use a plumb bob to determine whether the mast is erect. Again, there are too many variables that don't exist if you measure the distance using the jib halliard. Secondly, when you check your waterline stripe, to be sure it is level all around, and then you get back on the boat to check your plumb bob or to use your post level, the boat will start rocking, and the measurements will be inaccurate. In addition, depending on how you distribute your weight, the boat might not be floating on her lines after you step aboard her.

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

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dlucier
Master Marine Consultant

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Response Posted - 04/09/2002 : 21:32:55

Steve,

I don't exactly get a warm and fuzzy feeling when an attorney says,<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>Words are an imperfect way of communicating, because the same word can mean something different to each of us.<hr height=1 noshade id=quote></BLOCKQUOTE id=quote>
But on second thought it makes sense.<img src=icon_smile_big.gif border=0 align=middle>
Anyway, I agree that using a jib halyard is a more accurate way of determining if the mast in straight up and down in relation to port and starboard, but the port and starboard sides of the boat are symetrical and can be measure this way. The fore and aft parts of the boat are not symetrical so the jib halyard method of determining verticallity(is that a word?) fore and aft is not so cut and dry. What do you think?

Don Lucier, Northstar
C25 SR/FK

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Bristle
Admiral

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Response Posted - 04/09/2002 : 21:54:28

It all depends on what the meaning of "is" is. <img src=icon_smile_big.gif border=0 align=middle>

Dave Bristle, 1985 C-25 SR-FK #5032 "Passage" in CT

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dlucier
Master Marine Consultant

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Response Posted - 04/09/2002 : 21:58:46

Dave,

You "is" a funny man!<img src=icon_smile_big.gif border=0 align=middle>

Don Lucier, Northstar
C25 SR/FK

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dlucier
Master Marine Consultant

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Response Posted - 04/09/2002 : 23:52:32

Bruce,

Check out this item from the tech tips section on "installing a split backstay tang".http://c25c250.best.vwh.net/restricted/tt002.html

Don Lucier, Northstar
C25 SR/FK

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n/a
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Response Posted - 04/10/2002 : 10:24:47

You see considerable mention of using a halyard to test for plumb on a mast but I doubt this really works any better than plain old eyesight. The reason is that an error of say 3/8" in the distance to a chainplate (i.e. less than one halyard width) produces an error at the masthead of almost 3 inches. My guess is that a thick, old, stretchy, kinked, knotted, shackled halyard doesn't have much use as a yardstick. I've even tried attaching a real yardstick to the end of the shackle but I doubt it helps much. The simpler trick I use now is to stand back a good ways from the boat and line the mast up with the edge of a bulding in the background.

Andy P.
#5708

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Steve Milby
Past Commodore

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Response Posted - 04/10/2002 : 11:37:34

Don,

When a sailboat is designed, the designer determines approximately how the mast should be rigged. He decides where, along the centerline of the boat, the mast tabernacle should be placed, he specifies that the headstay should be a certain length and that the backstay should be a certain length. By making these specifications, the designer has generally pre-determined whether the mast should be perfectly erect, or whether it should be raked forward or aft.

By adding turnbuckles to the headstay and backstay, he has made it possible for the owner to adjust the length of the headstay and backstay by a few inches either way, to tilt the rig a little more forward or aft. Because sails are built differently and boats are sold with different optional equipment (e.g. adjustable backstays), the designer has to make allowances in the rigging to enable owners to adjust their rigs so that they perform their best with their particular sails and equipment.

I don't know whether the C-25 mast was designed to stand perfectly erect or to be raked a few degrees forward or aft of that, but I don't think it matters. I trust that, somewhere within the adjustable range of the headstay and backstay, as predetermined by the designer, there will be a point at which the boat is well-balanced, and at which it performs at its best. If I set up the mast somewhere in the middle of the adjustable range, then all I have to do is sail the boat and feel the amount of tiller pressure, and make further adjustments of the mast to reduce the tiller pressure to an acceptable amount. When the boat performs at its best, I will know that the mast is raked at its proper angle.

In short, you can't assume that, if you set up the mast so that it is perfectly vertical in every direction, the boat will perform at its best, because that might not be the way the designer intended for it to be set up. But you can assume that the designer intended that the mast be set up somewhere within the adjustable range of the headstay and backstay, and from there you can fine tune it until you find the exact adjustment that works the best for your sails and equipment.

Don't get me started on lawyers. I fought those rascals all my life!

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

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Bristle
Admiral

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Response Posted - 04/10/2002 : 23:17:28

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>
The simpler trick I use now is to stand back a good ways from the boat and line the mast up with the edge of a bulding in the background.
<hr height=1 noshade id=quote></BLOCKQUOTE id=quote>

Actually, if your boat happens to be listing a little (due to unbalanced loads--water, motor, etc.), the mast should be perpendicular (side-to-side) to the deck and waterline--not to the water. Thus, it shouldn't line up (viewed from the bow or stern) with the building in the background. If it does, then it'll perform somewhat differently on one tack than on the other. Sorta like the Tennessee Ridge Runner.......

Dave Bristle, 1985 C-25 SR-FK #5032 "Passage" in CT

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Champipple
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Response Posted - 04/11/2002 : 08:50:25

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>
You see considerable mention of using a halyard to test for plumb on a mast but I doubt this really works any better than plain old eyesight. The reason is that an error of say 3/8" in the distance to a chainplate (i.e. less than one halyard width) produces an error at the masthead of almost 3 inches. My guess is that a thick, old, stretchy, kinked, knotted, shackled halyard doesn't have much use as a yardstick. I've even tried attaching a real yardstick to the end of the shackle but I doubt it helps much. The simpler trick I use now is to stand back a good ways from the boat and line the mast up with the edge of a bulding in the background.

Andy P.
#5708
<hr height=1 noshade id=quote></BLOCKQUOTE id=quote>

I disagree Andy, I have seen many a professional rigger and many a sailmaker use this method to check the alignment of the mast. Some even attach a tape measure and run the halyard all the way up the mast to have some sort of a measuring guide.

Don't forget to sight up the mast while under load. Set your sails and go close hauled into the wind. While under load, stand at the mast and look straight up. The tip of your mast may break away to leeward. Adjust your turnbuckle on the upper until it runs straight. Tack over and begin again.

Also, to the newbies, when the Sails are set, your leeward shrouds will be loose. Nothing to be alarmed about, just the laws of physics.

Duane Wolff
"The Flying Wasp"
C-25, #401 std,sk
Chief Measurer C-25/250 national Org.
<img src="http://im1.shutterfly.com/procserv/47b2dc20b3127cce9cd2f45b211a0000004010" border=0>

Edited by - Duane Wolff on 04/11/2002 08:53:20

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n/a
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Response Posted - 04/11/2002 : 17:09:21

While you can't argue with the math, I do agree that 30' of light steel measuring tape could work well enough - only that's different than a rope halyard with an odd shaped shackle at the end. What I think probably happens is that people convince themselves that the halyard lengths are equal based on how the mast looks and not the other way around.

Andy P.
#5708

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