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Catalina/Capri 25/250 Sailor's Forums

Catalina 25 Specific Forum

Assistance needed: Tuning rigging

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James Simmons
1st Mate

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USA
41 Posts

Initially Posted - 04/28/2009 : 15:18:13

I have a 1981 C-25 FK and am trying to tune the standing rigging. I have researched and found excellent information on the forum but still have questions.

I can't figure out how to tune the forestay/adjustable backstay. Once I determine what rake I want in the mast using the halyard as a plumb bob what position should the adjustable backstay be in before I adjust the turnbuckle? Does it make any difference anyway as I can always crank down on the backstay to increase tension on the forestay?

My shrouds are tuned as follows: (The mast appears to be straight from a side to side perspective. The kerf is straight as well).

The upper shrouds are the tightest of any. Very little movement when depressed inward, maybe an inch)

Both the forward lowers and aft lowers are equally firm with less tension than the upper shrouds but still fairly tight (both will depress inward 1 to 2 inches when pressed inward).

In heavy weather the leeward shrouds will loosen somewhat and I will pay more attention the next time out now that I am becoming more familiar with tuning issues.

I would appreciate any comments, especially if you may have tips on how to deal with the forestay/adjustable backstay issue. Any other comments will be appreciated as well.

Edited by - on

jerlim
Master Marine Consultant

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USA
1484 Posts

Response Posted - 04/28/2009 : 15:21:04

Sounds like you've done a fine job of tuning...as far as the backstay, I tighten that turnbuckle w/ the adjusting rig set high.

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islander
Master Marine Consultant

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USA
4018 Posts

Response Posted - 04/28/2009 : 16:00:39

Go easy on the tightening. I read somewhere that you should never exceed 15% of the breaking point of the wire.

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Derek Crawford
Master Marine Consultant

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USA
3321 Posts

Response Posted - 04/28/2009 : 17:12:09

James - I also have an '81 TRFK and probably carry the loosest rig anywhere! I tune with the backstay and the vang off. My uppers are at 32 on the Loos guage (depress about 1" at shoulder height). The aft lowers are at 20 and depress a full 3-4". The forward lowers are at 24 and depress about 2".
All of my leeward shrouds wave in the breeze when sailing and under normal conditions I keep the backstay untensioned. The forestay has an 8-10" sag in it when the backstay is off.
These settings may not suit you if all you do is cruise (and in 12 knots they may scare you!) but they are the fastest setting I have found (and to a hard-core racer like me that's most important)

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Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 04/28/2009 : 18:38:12

Just one observation on Derek's setup... I believe he keeps his boat on a lift. If your boat is on a mooring or otherwise is affected by any chop on a long-term basis, a somewhat "snugger" (and perhaps slightly slower) rig will reduce shock-loads on all of the attachment points, including swages, chainplates, brackets, and even spreaders, while at rest. I suspect what makes Derek's rig fastest for him is that he can get the greatest range of sail shapes (main and jib) between a releasing and fully cranking down the backstay adjuster.

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Renzo
Admiral

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USA
621 Posts

Response Posted - 04/29/2009 : 07:14:35

You're on the right track James, but I would suggest that you purchase a Loos Gauge and a 75ft or 100ft tape measure so that your mast placement will be more exact and repeatable. Also the rig should be tuned with the the backstay tension adjuster in the "off" position so that when you crank down on the backstay it not only tightens the forestay but it also bows the center of the mast forward and thereby flattens the mainsail.

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Stu Jackson C34
Admiral

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844 Posts

Response Posted - 04/29/2009 : 07:50:11

Even without a gauge, the Catalina instruction manual that came with the boat is one of the best summary explanations of how to do it that I've ever read. Static tuning followed by dynamic tuning. Just don't move your turnbuckles when under load. Works for 99% of the time, unless you're a diehard racer...and for many of them (us?), too.

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Dave5041
Former Mainsheet Editor

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USA
3758 Posts

Response Posted - 04/29/2009 : 08:38:34

A Loos gauge (2 since both sizes are required) is a pretty expensive package for casual sailors. I agree with Stu, the basic guidelines in the manual are fine.

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Steve Milby
Past Commodore

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USA
5895 Posts

Response Posted - 04/29/2009 : 09:15:18

We recently talked about rig tuning without a backstay adjuster. If you have a backstay adjuster, you start by tuning the rig in that manner. The difference is that you have to readjust the rig to allow the backstay adjuster to work. If all the stays and shrouds are approximately equally taut, then, when you apply tension to the backstay adjuster, the stays and shrouds will hold the mast rigid, and won't allow the mast to bend.

If you want the tip of the mast to bend aft when tension is applied to the backstay adjuster, then there has to be some amount of slack in the headstay. If there's no slack in the headstay, the tip of the mast can't move aft. The forward lowers have to be fairly taut, because they will prevent the part of the mast below the spreaders from tilting aft when backstay tension is applied. (You don't want the whole mast to tilt back. You only want the upper half to bend back.) Also, the aft lowers have to be loosened because, when the mast bends, the whole mast will bow forward slightly. If the aft lowers are too taut, they will prevent the mast from bowing forward. The aft lowers should be adjusted, however, so that they become taut when the mast is bending as far as you want it to bend. They will prevent it from bending too much.

In use, the headdstay should be very slack when the adjuster is fully eased. That will allow the sails to take a full shape when sailing downwind. When you sail to windward and the backstay adjuster is tensioned, the headstay should be taut.

I tuned my rig about like Derek, and saw no reason why it wouldn't be a good setup for cruisers as well as racers. Cruisers like to go fast too, and they like the boat to point. A loose rig is not a good thing in choppy seas, because it permits the rig to swing and even jump around, but, with an adjustable backstay, if the seas become choppy, you should tension the backstay, and the whole rig becomes taut, and there's no risk of it swinging or jumping around. That's the whole purpose of the adjustable backstay. You can adjust the tension very quickly and easily, on the fly, so that it is ideal for whatever conditions you're sailing in. If you want it either taut or loose, you can make it so.

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James Simmons
1st Mate

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USA
41 Posts

Response Posted - 04/29/2009 : 16:57:30

Thanks, everyone. Great information!

After reading all the responses I think the next logical step is for me to loosen the aft lower stays a bit so they have less tension than the forward lowers. The question is, how much should I loosen? A couple of turns on the turnbuckle? (While on that subject which way does the turnbuckle turn to loosen? Does 'righty tighty, lefty loosey' work for turnbuckles? I have the older, enclosed type with locknuts if that makes any difference).

Once I accomplish this I will observe the bend in the mast when I put the backstay on. I have plenty of slack in the forestay (roller furling), in fact, I have wondered if I have too much.

I would appreciate any comments/suggestions concerning this plan.

Thanks, again.

Edited by - on

HeelinPatrick
Navigator

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USA
102 Posts

Response Posted - 04/30/2009 : 10:49:51

I'm a little confused, when do you want to measure the rake, with or without the backstay on. I'm thinking you would want it on, however, if the backstay is off, would you have forward (undesirable rake), or is it ok, since that means you are in lighter winds.

I have a two-position backstay, so it's either tight, or real loose.

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Steve Milby
Past Commodore

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USA
5895 Posts

Response Posted - 04/30/2009 : 11:43:33

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by HeelinPatrick
 I'm a little confused, when do you want to measure the rake, with or without the backstay on. I'm thinking you would want it on, however, if the backstay is off, would you have forward (undesirable rake), or is it ok, since that means you are in lighter winds.

I have a two-position backstay, so it's either tight, or real loose.
<hr height="1" noshade id="quote"></blockquote id="quote">That's a good question. I never thought about it. I always establish the rake of the mast in the early stages of the tuning process, when there's no tension on the rigging generally, or on the backstay adjuster in particular, and no bend in the mast. After the mast rake is established, then you can adjust the lowers to maintain that rake, at least in the lower section of the mast.

The general idea is that, when the backstay tension is applied, the top of the mast bends aft, but the center and lower sections bow forward. If the center and lower sections don't bow forward, then you'd be increasing weather helm when you apply the backstay adjuster, which is exactly what you don't want to do. In order for it all to work right, the center and lower sections of the mast have to bow forward at the same time that the top is bending aft. That keeps the whole thing in balance and reduces weather helm.

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Stu Jackson C34
Admiral

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844 Posts

Response Posted - 05/01/2009 : 09:05:22

Theoretically, that's true. But consider that our masts are essentially "telephone poles" that simply don't bend too much. This "bending the mast" concept is usually applied to "bendy rigs" like J boats and other fractional rigs and smaller dinghy racers. The purpose of the backstay tensioner on our boats is to simply and to "comparatively" (to non-tensioned backstays) tighten the forestay a bit to eliminate "some" sag when going upwind. Appropriate adjustments to the forward and aft lowers is not to be dismissed and may help a small bit, but it certainly won't make that much difference in the mast "operation" because the middle of the mast simply doesn't "bend" as much as is theoretically proposed. What you're actually doing by putting some tension on the backstay is tightening the forestay from the spreaders on up at the top 2/5-ths of the mast. Only the top of the mast is pulled slightly aft.

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