Association Forum - Offset backstay pulls top of mast to port

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Catalina/Capri 25/250 Sailor's Forums

Catalina 25 Specific Forum

Offset backstay pulls top of mast to port

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JoeRobertJr
1st Mate

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25 Posts

Initially Posted - 10/18/2019 : 13:56:13

Greetings! Just purchased a 1984 Catalina 25 swing keel / short rig. Tuned the rig for the first time today following the instructions in the owners manual and the better instructions in this site's tech tips. (Thanks for that!)

I am wrestling with understanding what to do with the backstay. The backstay chainplate is offset to port. So, this naturally pulls the top of the mast a little to port. The owners manual shows a picture of a split backstay with tension adjuster. It does not look like my boat ever had a matching chainplate on the starboard side.

The backstay has a two-foot length of wire crimped on about 6 feet up with a snapshackle at the end. I am tempted to use this to center the bulk of the backstay by pulling to starboard, but I am not sure where I would connect that. It will have a lot of tension, and I don't know that the stbd quarter horn cleat can take that kind of vertical strain.

Or should I forget about trying to center the backstay, and instead adjust the lower shrouds to pull the middle of the mast farther to port to compensate?

Joe Robert
C-25 SK/SR #4287
Orefield, PA

Steve Milby
Past Commodore

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USA
5851 Posts

Response Posted - 10/18/2019 : 17:07:34

Fuggedaboudit!

Lawyers have a Latin expression that applies to this question. "De Minimis" means "too trivial or minor to merit consideration." What is really important is that the mast be erect, in column and that it have an adequate rake. Notwithstanding the offset backstay, the C25 mast can be adjusted to meet all those standards as perfectly as if it had a split backstay. If the backstay wasn't offset, it would interfere with the swinging of the tiller.

Just follow the online instructions. They are based on the assumption that the backstay is offset. If you adjust the lowers to one side, it will pull the mast's mid-section out of column.

The offset backstay has absolutely nothing to do with the boat's performance, including it's speed or pointing ability.

Steve Milby J/24 "Captiva Wind"
previously C&C 35, Cal 25, C25 TR/FK, C22
Past Commodore

Edited by - Steve Milby on 10/18/2019 17:20:26

Lee Panza
Captain

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USA
465 Posts

Response Posted - 10/19/2019 : 00:04:41

From your description, Joe, I think the short length of cable you mentioned is the pigtail for holding up the boom if you don't have a topping lift. It's not designed to carry the magnitude of load required to center the backstay above it (it would have to accept half of the total tension in the backstay, which becomes substantial while you're sailing). It would also cause the backstay to bend sharply at that point, which would weaken it significantly.

Then there's the matter of anchoring it. You can see how substantial a chainplate you already have; you'd need to add something similarly robust to anchor the other leg of a split backstay.

Granted, a split backstay might be slightly superior, if it's properly implemented. Arguably the greatest benefit is that it allows for a simple backstay tensioning mechanism, although on a masthead rig that's a control that isn't terribly important to most of us (it's actually used for adjusting forestay tension). But what you're contemplating would not be worth the risk.

As for using the lower shrouds to compensate, they only pull the mast at its mid-height. A slight imbalance in the uppers would, in theory, compensate for the offset backstay, but this happens automatically when you adjust them to set the mast plumb.

To perhaps ease your concern, think about how small an angle you would be shifting the force by: the backstay is over 32' long and you're talking about shifting the projection of the bottom end by about a foot and a half. That's about 2 and a half degrees - not enough to worry about.

A lot of high-tech race boats do just fine with single backstays (or with running backstays that have to be switched each time the boom changes sides). So, as Steve said, don't worry about it.

The trouble with a destination - any destination, really - is that it interrupts The Journey.

Lee Panza
SR/SK #2134
San Francisco Bay
(Brisbane, CA)

JoeRobertJr
1st Mate

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25 Posts

Response Posted - 10/19/2019 : 03:15:52

Thank you both, Steve and Lee, for the very helpful responses. That all makes sense to me. I will no longer worry about that slight offset in the backstay.