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GaryB
Master Marine Consultant

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USA
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Response Posted - 06/16/2008 : 22:20:28

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Even Chance
 <blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by GaryB
 

If you don't mind I have some more questions. It was almost dead calm today for literally the first time in about 4 or 5 months but the boat was still moving a fair amount due to wave action. How do you ever figure out when the mast is plumb with the boat when the boat is in the water and moving around?
<hr height="1" noshade id="quote"></blockquote id="quote">

Gary, another method is to attach a long tape measure to your main halyard shackle, and run it to the head of the mast. Measure the distance to common points on either side -- I use the top of the upper shroud chainplate (where the toggle from the upper shroud attaches to the metal plate that runs down through the deck). When the distance on both sides is equal, your mast is plumb.
<hr height="1" noshade id="quote"></blockquote id="quote">

Well, my mast was plumb when I measured using the method above.

Edited by - GaryB on 06/16/2008 22:32:33

GaryB
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Response Posted - 06/16/2008 : 22:31:27

For some reason I cannot get the slight bend out of my mast. The fore-stay and back-stay are very loose. I bought a #90 Loos Gauge today and set the uppers to 28 and the lowers to a guesstimated 22 or 23. All are equally tensioned.

The Loos Gauge really makes it easy to adjust the shrouds.

I don't remember seeing this before I lowered the mast. Not sure if the aft lowers were tighter than the forward lowers before or not. Would it hurt to set the aft lowers slightly tighter than the forward lowers? If I do that the bend goes away.

I also cannot get the mast to rake back. It appears to be straight up when compared to a couple of other C25's down the dock. I've loosened the fore-stay as far as it will go.

Should I just sail it a while like it is to let everything take a set and then re-adjust everything or should I be able to get it set where it needs to be without sailing it?

Edited by - on

Frank Hopper
Past Commodore

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Pitcairn Island
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Response Posted - 06/16/2008 : 23:22:07

In my limited experience, I would say the type of sailors who post on this forum are the type people who have the gauges on the dock; and share them. I am glad I have one, its in my tool bag.

Edited by - on

Dave Bristle
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Djibouti
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Response Posted - 06/17/2008 : 09:30:14

Gary, the measure of whether your mast should be raked back or not is your helm. Take her out in some moderate winds and see if you have a little weather helm. If you have enough to have to constantly pull the tiller to windward, the mast is too far back. If you have lee or totally neutral helm, it's too far forward. The condition of your main can be a factor--a blown-out main adds to weather helm.

If you need to tip it further back, a toggle can be fitted to the forestay to lengthen the stay a few inches. The problem I had was lee helm, and my original backstay was too long. I had to have a rigger shorten it. (Nope--didn't do my own sages.

)

Edited by - on

dmpilc
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Response Posted - 06/17/2008 : 10:05:26

Yesterday, I was re-tuning my rig using a Model A Loos gauge, same one I use with our C-22. I was getting readings of 40-45 on the uppers, and very loose lowers were reading at 25. Seemed odd. Also, the upper wire would not fit into the slot at the bottom of the gauge but the lowers do fit, so do I need to be using a larger model gauge? Also, up to the spreaders, the mast seems to be in column, but the masthead still tips about an inch to starboard with both uppers set at the same reading. After adding the stainless mast step plate, I also have very little wiggle room with the upper turnbuckles. Both are virtually fully extended, i.e. I have just barely enough room to put the locking rings through the holes in the turnbuckle screw posts. Any suggestions?

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GaryB
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Response Posted - 06/17/2008 : 10:24:47

David,

As you can tell from all of my posts I am still learning how to do this as well. One thing I learned yesterday is the Loos Gauges come in different sizes based on the wire size in your rigging. To do it absolutely correctly you need two different Loos Gauges to set the tension on a C25. Several on this forum have mentioned they use one and extrapolate which is waht I plan to do.

Sounds like you may need to get another gauge to get the correct readings. The fact that the uppers would not fit sounds like either the gauge is too small or the uppers are way to tight.

Then again I could be totally wrong on all of this! I'm sure others will chime in to set us straight.

My biggest concern is the bend in my mast.

Edited by - on

GaryB
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Response Posted - 06/17/2008 : 10:30:16

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Dave Bristle
 Gary, the measure of whether your mast should be raked back or not is your helm. Take her out in some moderate winds and see if you have a little weather helm. If you have enough to have to constantly pull the tiller to windward, the mast is too far back. If you have lee or totally neutral helm, it's too far forward. The condition of your main can be a factor--a blown-out main adds to weather helm.

If you need to tip it further back, a toggle can be fitted to the fore-stay to lengthen the stay a few inches. The problem I had was lee helm, and my original back-stay was too long. I had to have a rigger shorten it. (Nope--didn't do my own sages.

)
<hr height="1" noshade id="quote"></blockquote id="quote">
Before I lowered the mast a had just a small amount of weather helm. The only time it got bad was if it blowing above 12 -15 knots. I didn't notice a lot of rake before and the boat seemed reasonably fast to me compared to other C25's so i guess I'll just sail it and see what happens.

Any idea why I cannot get the bend out of my mast unless I tighten the aft lowers just slightly tighter than the forward lowers? Will having the aft lowers tighter than the forwards cause any serious problems with the mast or rigging?

Edited by - GaryB on 06/19/2008 09:40:45

Stardog
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Response Posted - 06/19/2008 : 10:02:52

Gary, I had a similar problem with my boat when I first bought it; if you layed on the deck and looked up it, it had an S curve. The lower section was curved one way and the upper was curved the opposite way. I tried to fix it by changing the tension on the shrouds and could never get it right. My sailmaker recommended I drop it and straighten it. His contention was that the mast had to be straight before adjusting the shrouds and stays or the loads on the rig would be uneven and could possibly damage or break the mast. We got some friends together, dropped the mast and laid it on some sawhorses. Then we alternately sat on it and bounced in the proper places to straighten it out. There is a good possibility you will be able to get good results in doing this. Once it is straight, your shrouds and stays can be tuned properly to hold it in column.

One last note: Catalinas are notorious for having weather helm, pulling your mast as far forward as your stays will allow will help. Don't worry, you won't be able to get it far enough forward that it is noticeable to the untrained eye.

Edited by - on

Dave Bristle
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Djibouti
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Response Posted - 06/19/2008 : 10:24:25

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by GaryB
 Any idea why I cannot get the bend out of my mast unless I tighten the aft lowers just slightly tighter than the forward lowers? Will having the aft lowers tighter than the forwards cause any serious problems with the mast or rigging?
<hr height="1" noshade id="quote"></blockquote id="quote">If you're straightening it by tightening the aft lowers, that suggests the bend is (IMHO) the "good" kind--midsection forward and top back, which helps to flatten the main. If it's just a few inches and an even curve (not at a point), I wouldn't worry about it. Otherwise, Stardog's approach might help.

Edited by - on

GaryB
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Response Posted - 06/19/2008 : 11:31:56

Mine is a nice smooth arc as Dave described. The midsection is slightly forward and the top is back at the most maybe 2". To me it looks like the top of the mast is about even with the foot it just has a slight bow forward in the middle. If I put a little bit more pressure on the aft lowers it will straighten out.

Would it hurt to have slightly more tension on the aft lowers than the forward lowers?

Edited by - on

Dave Bristle
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Djibouti
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Response Posted - 06/19/2008 : 17:48:28

I don't see why... More common is more tension on the forward lowers to put in the bend you already have. Also, more tension either forward or aft might help to prevent "pumping" where the mast flips from foward bend to aft bend and back, rapidly, in high winds at the dock.

Edited by - Dave Bristle on 06/19/2008 17:50:56

stampeder
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Response Posted - 06/19/2008 : 20:30:44

I printed off the instructions posted earlier in this thread and they now reside in a sailing binder on my boat.

I have a collection of wisdom gleaned here that I refer to as, 'the best of the Forum'

Edited by - on

cat1951
Admiral

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USA
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Response Posted - 06/20/2008 : 08:29:04

I have to say that after reading all of the posts here, you can tune your mast in numerous ways. Some use a gauge, some don't, some are loose, some aren't, some rake, some don't, etc. My shrouds are all hand tightened from when we lowered the mast 2 years ago and the mast is straight and vertical.

From a non-expert it seems that as long as you don't have your mast slamming back and forth on the shrouds, and you don't drive it through the cabin top by tightening the shrouds too much, and your mast is straight and centered, you are OK.

Now if you want to race, then you need to be more of an expert in tuning.

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ClamBeach
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Response Posted - 06/20/2008 : 09:00:22

>"Mine is a nice smooth arc as Dave described. The midsection is slightly forward "

Sounds pretty good to me. In an ideal setup, you want the mast to go nearly straight when the backstay is fully slacked. This 'powers up' the main for light air. As you tighten the backstay you want a nice smooth bend to be introduced which depowers the main. Usually the aft lowers are run with a little more slack than the forwards to allow the mast to react smoothly to the backstay tension.

Having different tensions in the forward/aft lowers usually puts a little 'pre-bend' in the mast (bend before the backstay is tightened... that's not really a bad thing unless it's excessive.

I set up and tune my rig up by 'feel & eye' and adjust so the mast responds to the backstay the way I want it to. I'll adjust overall tension of the rig so that beating in 15 kts or so, the leeward shrouds will go slighly loose... some movement evident but not flopping around. What that tension is on a gauge... I dunno.

Bottom line is that all the stays have to tensioned to 'work together'.

Edited by - on

GaryB
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Response Posted - 06/20/2008 : 10:24:35

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by ClamBeach
 >"Mine is a nice smooth arc as Dave described. The midsection is slightly forward "

Sounds pretty good to me. In an ideal setup, you want the mast to go nearly straight when the backstay is fully slacked. This 'powers up' the main for light air. As you tighten the backstay you want a nice smooth bend to be introduced which depowers the main. Usually the aft lowers are run with a little more slack than the forwards to allow the mast to react smoothly to the backstay tension.

Having different tensions in the forward/aft lowers usually puts a little 'pre-bend' in the mast (bend before the backstay is tightened... that's not really a bad thing unless it's excessive.

<hr height="1" noshade id="quote"></blockquote id="quote">

As soon as I put any tension on my uppers the mast starts getting a little bit of an arc in it. That's with the fore-stay, back-stay, and lowers relaxed completely. When I tighten the lowers as recommended by several people here on this forum and in the owners manual the arc gets more pronounced but I don't think excessive Maybe 2 or 3 inches at the most. I just never saw this arc in the mast before I lowered it.

It sounds like most of you think this is OK seriously wrong with the way it's set so I'm going to give it a try tomorrow and see what happens.

Of course now that I've got the boat ready to go again the 10-20 knot winds we've had for the past four months have disappeared and I'm looking at3-8 knots for the weekend.

Edited by - on

Stardog
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Response Posted - 06/20/2008 : 11:01:10

Something to think about in tuning: This is a masthead rig and to quote my local sailmaker - "it's a telephone pole". The stays meet at the top and if you tune it with an arc in it, you can't change that arc under sail. Simply put, if you induce an arc into a masthead rig, you lose light air performance. On the other hand, the forestay of a fractional rig is attached at a point some fraction of the mast length from the masthead. The mechanics are such that pulling on the backstay induces an arc into the the mast which cause the mainsail to flatten. With a fractional rig you can change the arc of the mast with the backstay adjuster. You can do this easily, even while sailing. You can't make adjustments like that to a masthead rig. It requires tuning the rig to make the change. If you tune it the way the designer intended you'll get better performance overall.

Edited by - on

GaryB
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Response Posted - 06/20/2008 : 11:13:39

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Stardog
 Simply put, if you induce an arc into a masthead rig, you lose light air performance.
<hr height="1" noshade id="quote"></blockquote id="quote">

Of course in my case, the main is so baggy that a light arc in the mast won't make much difference!

Edited by - on

GaryB
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Response Posted - 06/21/2008 : 22:03:12

Well I figured out why the mast had an arc in it. I used the #90 Loos Guage to set the uppers and then just guessed at what numbers to use for the lowers. I set the at 15. Today I decided to buy a #91 Loos gauge to make sure I set the lowers properly. They were at 40!!! Once I backed them down to 26 the mast straightened out for the most part. There's just barely an arc in it now.

Now my question is are the lowers supposed to be just barely tight? They seem really loose now. They are almost flapping in the breeze. They were never that loose before. This is with the back-stay backed off. I would expect the forward's to tighten when I pull on the backstay and the afts to get even looser?

Please advise!

Edited by - GaryB on 06/22/2008 08:34:40

ClamBeach
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Response Posted - 06/22/2008 : 09:50:13

>"They are almost flapping in the breeze"...

They shouldn't be 'twanging' tight, but they should't really be flopping around either. Don't know how to convey it in words other than 'snug'... forward lowers a little tighter (nice and snug) than aft lowers (just plain snug) :>). Note: I set my mast with a little prebend.

All your shroud tensions need to work together. If you're in a marina, walk around and wiggle similar sized boats shrouds to get a sense for the 'feel' of things. (Pick boats that are sailed!)

>"expect the forward's to tighten when I pull on the backstay and the afts to get even looser?"

No. As the mast bends in a nice 'centered' arc (hopefully), the aft lowers will get tighter and the forward lowers a bit looser. That's why you run the aft lowers at a lower tension... to allow the mast to bend in that smooth arc. If you set the aft lowers too tight the mast can only bend above the point where the lowers attach. Putting extra tension in the forward lowers gives the mast 'pre-bend'.

Do a little thought expermient and think how the mast would bend if both sets of lowers were perfectly rigid... the attachment point for the lowers would be just like the deck (it's not going to move).

When you are beating or reaching in a nice breeze (10-15kts or so) you should see the leeward shrouds just slacken a bit... but not flop around in the breeze. They should also 'slacken' together. If the lowers are still tight and the upper is flopping (or vice versa) try to bring them into 'harmony'. Sounds 'zen-like'.

>"it's a telephone pole".

You would be surprised at what you can do with that telephone pole... :>)

Edited by - on

Dave Bristle
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Djibouti
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Response Posted - 06/22/2008 : 11:53:49

Stardog: Your sailmaker is sorta right, but just sorta... Indeed you have more bending power with a fractional rig, but as described in several posts here, some bend can be achieved by the backstay pulling against the forward lowers--a key reason for having two pairs of lowers. Since the fore- and backstays will have equal tension as you tighten or loosen the adjustor, the direction of the bend is determined by the relative tensions on the fore and aft lowers.

Another component of bending on some rigs is swept-back spreaders. They allow the upper shrouds to push forward on the midsection of the mast. But the C-25 doesn't have them. Hunter uses radically swept spreaders in place of having any backstay at all--the "B&R Rig", which can induce considerable bend in their masts.

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GaryB
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Response Posted - 06/23/2008 : 09:45:23

Well I went sailing yesterday and I figured the lowers were too loose so as soon as I got the sails up I started watching the leewards and sure enough the lowers really started flapping in the breeze (6-8 knots) so I tied off the tiller and jumped up and hand tightened them until they were snug. As soon as I finished one side I did a 180 and did the same thing for the other side. I didn't see any movement in the uppers on either side.

Everything seemed to work just fine after that. Boat sailed like it did before with just a tad of weather helm.

I would have measured the tension on the rig when I got back to the dock to see where it ended up but I had to get to the airport to pickup the admiral.

One question that did pop into my mind is how far up the shroud should you measure the tension? Seems like that could make a difference in the actual tension you get on the shrouds. I measured mine at chest height while standing on the cabin top (approx. middle of the shroud). If you measured at chest height standing on the side deck (below mid shroud) it seems like you could get a different actual tension on the shroud even though the gauge is reading the same number.

Edited by - GaryB on 06/23/2008 12:23:07

Steve Milby
Past Commodore

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Response Posted - 06/23/2008 : 10:29:07

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Stardog
 Something to think about in tuning: This is a masthead rig and to quote my local sailmaker - "it's a telephone pole". The stays meet at the top and if you tune it with an arc in it, you can't change that arc under sail. Simply put, if you induce an arc into a masthead rig, you lose light air performance. On the other hand, the forestay of a fractional rig is attached at a point some fraction of the mast length from the masthead. The mechanics are such that pulling on the backstay induces an arc into the the mast which cause the mainsail to flatten. With a fractional rig you can change the arc of the mast with the backstay adjuster. You can do this easily, even while sailing. You can't make adjustments like that to a masthead rig. It requires tuning the rig to make the change. If you tune it the way the designer intended you'll get better performance overall.
<hr height="1" noshade id="quote"></blockquote id="quote"> I used to think that way, too, for many years, until Derek Crawford showed me the light.

If you have a backstay adjuster, tune your rig the way you normally would tune a rig without a backstay adjuster. Then make the following re-adjustments:

"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 headstay so that the mast tip bends aft about 8-9 inches when the backstay adjuster is tensioned. When the backstay adjuster is eased, the headstay should be quite slack (so slack that it has a catenary curve). Adjust the aft lowers so that they become tight when the backstay is tensioned. The way to do that is to apply the maximum tension on the backstay adjuster. Then adjust the aft lowers until they just become taut. When you release the tension on the backstay adjuster, the aft lowers will become slack. When you re-apply the backstay tension, the aft lowers will become taut again. 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."

When the backstay adjuster is eased, the headstay develops a lot of sag, which you can adjust to any extent to make the jib full and powerful off the wind. The mast becomes straight, which increases the power of the mainsail.

When the backstay adjuster is tensioned, the center section of the mast is thrust forward, while the upper section is bent aft. This pulls the fabric in the middle of the mainsail forward, depowering it. The headstay becomes taut, which enables the boat to point well.

The idea of the backstay adjuster is to allow you to re-tune the rig on the fly. By tensioning or releasing the backstay adjuster, you can go from a very highly tensioned rig for sailing to windward, to a very slack rig for sailing off the wind. In puffy winds, you can play the backstay adjuster, easing the tension slightly in the lulls, and hardening it up in the puffs, when the boat begins to become overpowered.

IMHO, the idea that the mast on a masthead rigged boat is a telephone pole, is a popular myth. The slender mast of a fractionally rigged boat bends farther and more readily than the thicker mast on a masthead rigged boat, but the latter is still flexible aluminum tubing and can nevertheless be bent, if the rig is tuned to permit it.

Edited by - on

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