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Catalina/Capri 25/250 Sailor's Forums

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Rig tuning redux

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Prospector
Master Marine Consultant

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Canada
3159 Posts

Initially Posted - 06/12/2009 : 11:36:21

I know its been discussed before, but I have the world's most basic question with rig tuning. Ok its more complicated than how do I tighten a turnbuckle, but I digress...

A C-25's rig, when properly tuned, is supposed to be loose on the leward side, but taught on the windward side beam reaching in 10 kts (+/-) IIRC.

Thats fine. How do you check if the mast is in column? I mean back in the slip, when you go to sight up the mast, won't it be leaning slightly to one side or the other since neither side will be tight?

How can you know if the looseness on port is equal to the looseness on starboard? A loos gauge would be worthless if the rig isn't tight, wouldn't it be?

Same deal fore and aft. The forestay should be loose with backstay off, but the tip of the mast should move aft with the backstay tensioned. You can see that in the slip, but how do you know that the aft starboard shroud isn't tighter than the forward port shroud, which will cause the mast to move off centre, and bend at the spreaders. (A dozen different scenarios could play out here)

Am I over thinking this, or missing something? In my quest to tack to 100º I need to explore every avenue, and rig tuning is definately one of them.

"Iris"
1984 FK/SR #4040
http://frosthaus.blogspot.com/

Take a minute to register your boat with the association!!
http://www.catalina-capri-25s.org/owner_questionnaire.htm

Edited by - Prospector on 06/12/2009 11:37:15

Dave5041
Former Mainsheet Editor

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USA
3758 Posts

Response Posted - 06/12/2009 : 11:58:00

Loose on the leeward shrouds while sailing is still moderately firm in the slip. I'm not racing or in a quest, so I mostly follow the directions in the manual but with the forward lowers slightly tighter (not enough to induce bend with the back stay off). I'm sure that the more serious people will chime in.

Edited by - on

HeelinPatrick
Navigator

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USA
102 Posts

Response Posted - 06/12/2009 : 12:57:58

I understood wires to be snug at dock too. But, if you want them loose or somewhat loose, maybe tighen them as needed, align the mast, then loosen them the same number of turns on each side.

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jerlim
Master Marine Consultant

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USA
1484 Posts

Response Posted - 06/12/2009 : 12:59:56

While theories abound on how much tension is correct, it's important to have tension in all the lines and equal (balanced) tension between pairs (l&r). The loos gauge is handy to measure the tension, but developing a feel and visual inspection work well too.

Edited by - on

redviking
Master Marine Consultant

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USA
1771 Posts

Response Posted - 06/14/2009 : 06:55:44

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Prospector
 How do you check if the mast is in column? I mean back in the slip, when you go to sight up the mast, won't it be leaning slightly to one side or the other since neither side will be tight?<hr height="1" noshade id="quote"></blockquote id="quote">

At the dock, climb the mast with a very long tape measure, (the soft kind on a spooling device with a hand crank or use line and mark it) and measure the distance to the terminal end on deck from the top of the mast. There may be some difference in length which would indicate if the mast was centered properly.

Note: Just because the mast is centered on the deck plate does not mean the mast is centered. On my C25, I discovered that the PO had in fact had problems with the original deck plate screws, and that there were two sets of holes beneath the deck plate, indicating that the deckplate had moved from its stock configuration. And only two of the screws tightened up anyway! The screws were shallow, I suspect to give way in the event of a dismasting. But the deck plate may not be centered, who knows if Bob the C25 assembler screwed the plate centered to begin with! The only real way to know is to measure.

Easier said than done on a 25 - the taller the mast, the greater the variance, which makes the job easier. This made me wonder and perhaps I missed this thread, but has anyone else climbed the mast? I was leery of climbing my C25 and only did it once, but now I routinely go up 58 feet on my C&C 39. And while I don't like heights, I trust the rigging and winches below a lot more which creates a better trust to risk ratio...

And Jerry has it right, just inspect - watch the standing rigging and run with it. Oil up each turnbuckle frequently. They must move easily, otherwise corrision can cause the threads to fail.

sten

Edited by - redviking on 06/14/2009 07:00:37

Nautiduck
Master Marine Consultant

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USA
3704 Posts

Response Posted - 06/14/2009 : 08:46:19

Using a long tape measure from the mast top is a great way to check the mast for being in column. It can be done without climbing the mast. I fasten the loose end of a 50' tape measure to the main halyard. Raise the halyard and do your side-to-side measuring that way. I use a chainplate as the point to measure to on each side. With this approach you can measure throughout the rig setting process, shroud adjustments, etc.

Edited by - Nautiduck on 06/14/2009 09:14:16

Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 06/14/2009 : 10:00:51

Why even a tape measure? The halyard alone does it--shackle it to a stanchion base, cleat it off, and see if it can attach to the opposite base the same way. Halyard too short? Tie a short line to the shackle.

Chris: Loose at the dock is too loose, IMHO. It allows too many shock-loads against all of the fittings when not under sail--from the slightest wave action. The rig can be firm at the dock and still go slack on the leeward side under load. I kept mine just tight enough so only the aft lower barely went slack on a beat, but I wasn't racing and didn't have an adjustable backstay.

Edited by - Dave Bristle on 06/14/2009 10:02:38

Stu Jackson C34
Admiral

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844 Posts

Response Posted - 06/14/2009 : 10:53:36

Why not do it the simple way? Read the Instruction Manual that came with the boat. Catalina's rigging tuning guide is one of the best and simplest ever published.

The shrouds (none of them) should be loose at the dock. Dave's right, shock loading is bad, bad, bad.

If you can't find it in your manual, here's ours (same rig, same stuff): http://www.c34.org/manuals/1988/1988-C34-Owners.pdf see PDF pages 19 & 20

Edited by - on

Prospector
Master Marine Consultant

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Canada
3159 Posts

Response Posted - 06/15/2009 : 07:18:12

So I went to the boat on Friday night and started with the basics. Looked up the mast and said "Holy Carp!"

Slip neighbour came over and took a look. "Is that the stick Paul Henderson used to score the winning goal in the summit series?" I pointed out that the series was in '72 and my boat wasn't built until 1984.

"Wow, they saved his stick that long?"

In any case, I adjusted until the msat was straight, and then tensioned the shrouds and stays to hand tight all around.

Sight up the mast again, everything looked straight.

Went for a sail and recorded the tracklog. I'm not sure if its a fair comparison since the wind was different, and we were flying our 155% instead of the 110% but we gained about 10deg so things are looking a little better.

I hope to get out again this week and see what other adjustments I can make.

An interesting note is that when we apply backstay, there is no fore-and-aft change in the mast position. I hope this means that the mast is bowing fore-and-aft, but that never occurred to me until I spoke to another experienced sailor who replied that "of course the top of the mast would stay in column". Silly me.

I'll have to apply backstay and sight up the mast again to see what is happening. As long as it doesn't look like a hockey stick...

Edited by - Prospector on 06/15/2009 10:58:52

Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 06/15/2009 : 07:56:45

If, with the adjuster "off", your forward lowers are tighter than the aft lowers, when you crank the backstay, your mast should bend back a little (bowing forward in the middle), which will help flatten the main. Mast-head rigs with perpendicular spreaders don't do this as well as fractional rigs with swept-back spreaders and tapered masts, but you can get some bend.

Edited by - on

Prospector
Master Marine Consultant

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Canada
3159 Posts

Response Posted - 06/15/2009 : 08:29:00

Oh Dave, I used your technique for measuring left/right position on the mast. Thanks for the tip. I think I will re-measure with a surveyor's tape (easy for me to get from the office) though since the stretch in the halyard left some question marks for me.

Edited by - on

Prospector
Master Marine Consultant

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Canada
3159 Posts

Response Posted - 06/15/2009 : 08:36:28

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by redviking

This made me wonder and perhaps I missed this thread, but has anyone else climbed the mast? <hr height="1" noshade id="quote"></blockquote id="quote">

Hey Sten, I climbed it about 2 weeks ago to install a spinaker block. I actually have a dangerous affinity for heights. No trouble climbing the mast, no movement of the mast or rigging, no swaying or movement of the boat. We were in our slip with a decent wind, and my safety man was concerned with me going aloft in the conditions.

SWMBO stood nearby taking pictures "For the insurance company."

Presently I am having a hard time deciding between dropping the mast or climbing it to mount a new anchor light.

Edited by - on

Steve Milby
Past Commodore

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USA
5902 Posts

Response Posted - 06/15/2009 : 08:45:16

With regard to your initial questions, think about the way the rig is designed. The tension provided by the starboard upper should be equalized by the tension provided by the port upper. The same is true of each pair of stays; the forward lowers and the aft lowers. If you are adjusting the forward lowers, for example, you should start by tightening the turnbuckles of each until you have just taken the slack out of the stays. When there is no slack in them, and there is a very light, equal amount of tension in each, then start turning each of the turnbuckles tighter, alternately and by an equal number of turns (3-5 turns at a time) until they begin to feel approximately equally firm (i.e., they deflect about the same amount when you pull on each). While doing this, you should periodically lie on your back and sight up the mast to be sure the mast isn't bowing one way or the other. If it is bowing one way, then you should carefully ease the tension on one side and increase the tension on the other side until the mast is pulled into proper alignment.

This sounds like it's a "seat-of-the-pants" method of tuning a rig, but it really isn't. What matters is that the mast have the desired shape, and that it behave in the desired way, and, if it has that shape and behaves in that way, then you'll know that the tensions are very close to optimal, because that's the only way you can make it look right and behave right.

There is a difference between the way rigs with and without backstay adjusters should be tuned. If you follow the directions for tuning a rig without a backstay adjuster, then your backstay adjuster won't work. I have never seen a tuning guide for a rig with backstay adjuster, provided by Catalina. The purpose of the backstay adjuster is to enable you to immediately change the tuning of your rig from light air tuning to heavy air tuning, without turning a wrench. The C25 mast has enough flexibility in it that you can bend it a little bit, if the uppers and lowers are adjusted to permit it. Also, the amount of headstay sag can be increased to provide more power in light air and off the wind, and decreased to depower the sails and aid the boat in pointing when sailing to windward and in stronger wind.

I tuned my C25 rig with backstay adjuster in a manner described to me by Derek, and believe it works very well. I described the method in the last page or two of an article titled "Racing to Win," which is posted in the Racing Tips section of this website.

Edited by - on

Prospector
Master Marine Consultant

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Canada
3159 Posts

Response Posted - 06/15/2009 : 09:05:48

Thanks Steve i printed the tuning manual on this site and took it with me, and found it to be a great help. Not sure if we are talking about the same document...

http://www.catalina-capri-25s.org/tech/tech25/snkmast.asp

Edited by - on

Steve Milby
Past Commodore

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USA
5902 Posts

Response Posted - 06/15/2009 : 09:21:30

Everything Bill has written about the C25 is excellent, but I believe his tuning guide only deals with boats that don't have an adjustable backstay. My tuning guide is in an article that is posted in the "Racing Tips" section of the website, and it also includes a guide for tuning a rig with a backstay adjuster. The following hyperlink should take you to it: http://www.catalina-capri-25s.org/racing/racing_tips7.asp

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DaveR
Master Marine Consultant

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USA
2015 Posts

Response Posted - 06/15/2009 : 12:11:47

Very interesting stuff. I think we guys with wing keels need all the help we can get for our boats to point well at all so thanks for the ideas!

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