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Catalina/Capri 25/250 Sailor's Forums

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adjustable back stay follow-up q

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dalelargent
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USA
198 Posts

Initially Posted - 07/04/2016 : 17:19:21

I had 6 days of sailing in the San Juans to play with my brsnd-new adjustable back stay rigging. And now I have a question...

FYI, I have an 8:1 rigged on my split back stay. When I released the line to sail downwind, the carriage would barely move even though I could easily push it all the way up by hand. The back stay seemed "loose" after sliding the carriage up, too. And pulling it back down on an upwind was incredibly easy. It makes me think the mast isn't tilting/bending forward as I expected on the downwind.

However, I can say that if I forgot to tighten down during a turn to wind, and remembered minutes later, I would then notice a slight improvement in boat handling after the adjustment. That makes me think there was SOME amount of bend going on. Maybe.

SO, what parts of this are normal and which aren't? I have never used one before, so am completely without reference. Are my aft lower shrouds too tight and preventing the mast from moving forward? Other advice? Does all sound normal?

1 more specific question: when the mast moves forward properly, is it flexing from above the lower shrouds or more like tilting from the base?

I deeply value this forum!

1989 c25 WK/TR #5838
1998 Catalina 36 mkii
1983 Vagabond 14

Steve Milby
Past Commodore

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USA
5851 Posts

Response Posted - 07/04/2016 : 18:21:32

On a masthead rig, like a C25, the backstay adjuster mostly tilts the mast fore and aft. If the rig is adjusted correctly, it can also bend the mast slightly. The effect of tilting the rig fore and aft is that, when tilted forward, it increases forestay sag. That powers up the jib when sailing downwind. When tilted aft, it reduces forestay sag, which flattens the jib and makes it point higher to windward. The effect of bending the mast is to pull the fabric in the mid-section of the mainsail forward, depowering the sail. To bend the mast when the backstay adjuster is tensioned, you have to adjust the forward lowers taut, and leave the aft lowers a little looser, but not too loose. When the adjuster is tensioned, the lower section of the mast is restrained from tilting aft by the forward lowers. The looser aft lowers permit the lower section of the mast to bow forward slightly. The backstay tension causes the upper part of the mast to bend aft.

Don't over-tighten the backstay adjuster. Some people think the tighter they pull it, the higher the boat will point and the faster the boat will go. They're wrong. Once the forestay is bar-tight, the boat won't point higher or foot faster, no matter how hard you pull on the backstay adjuster. All you will accomplish is to damage the boat structurally.

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

Edited by - Steve Milby on 07/04/2016 19:27:45

Steve Milby
Past Commodore

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USA
5851 Posts

Response Posted - 07/05/2016 : 07:07:56

When you tune a masthead rig with a backstay adjuster, the mast should be nearly plumb with the adjuster fully eased, and the forestay should be very slack. If there isn't some slackness in the forestay, then the top of the mast won't be able to bend back when you tension the backstay adjuster. Don't be tempted to bend the mast a lot. A little bend is enough on a masthead rig.

In tuning the rig, your goal should be to retain some weather helm, but to minimize it when sailing closehauled with the backstay tensioned.

Calling the device a "backstay adjuster" is really a misnomer. The backstay is really the means by which you are increasing or decreasing the tension on the forestay. I have always thought it would be more appropriate to call it a "forestay adjuster."

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

dalelargent
Navigator

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USA
198 Posts

Response Posted - 07/06/2016 : 12:48:05

Thanks for the very helpful replies. I will head to the boat this weekend and do some adjusting. I am excited to get it right.

Dale