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1986 Sabre 30 MIII
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Discussion Starter #1
I have a Sabre 30 masthead rig with a hydraulic backstay. I don't use it as much as I would like due to various murmurings cautioning me against over-tensioning with potentially "bad" consequences. How can I determine a reasonable upper limit on how much tension to apply? Thanks - in advance - for any advice.
 

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We have a hydraulic backstay and use just about ever time I go sailing. Although it’s not as instrumental on a masthead rig than a frac it’s still a huge help.
first will put more on it I’m going to roll up the genny at all. Even for a reef. It’s much less work when sag is taken out of the stay.
second will let it off anytime wind is behind the mast. Increased sag means you spill less wind and go faster.
third will adjust it for all those time you are in between reefs in aws.
there’s a guage on it. Use it and over time you figure out how much to use in different settings. Go to your owners group website to get further information on settings and what to not exceed. Lastly you won’t get what the hydraulic backstay can do for you if your rig isn’t well tuned to start.
there’s nothing to be afraid of if used correctly. They put it on your boat to be used.
BTW I always leave the boat with half a pump or less on it. That seems to be good for the seals in it. Just a wee bit of tension. Doesn’t stress the rig or cause stretching of the 1x19. Make sure the turnbuckle controlling backstay tension at rest is correctly set up. We have a mark on the dial of tension not to exceed so newbies can’t screw up.
 

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Our last boat was a masthead rig with a hydraulic backstay and it was very useful. Of course it was good for controlling headstay sag, but it was also very good for de powering the main. When it got breezy I would pump it up to 3-4000psi which would induce a lot of mast bend and flatten the main.

If your rig is well maintained there is no danger to using your hydraulics. The rig can take the loads with no problem. Just remember to ease the pressure at the end of the day.

Sent from my SM-G960W using Tapatalk
 

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Have you tried asking Sabre what they think loading should be? Cranking up on the things has turned boats into "bananas" by trying to drive the mast through the keel, but Sabre layups are supposed to be heftier than the typical lightweight racing hull.
 

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Tartan 37
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I was aboard a Trintella 50 two years ago... Near Key West the fluid leaked due to a bad seal, 83' mast, fairly decent sized seas... Thankfully it had running backstays as well up to the upper spreader. We were able to rig up a temporary fix with Amsteel until we got to Ft. Lauderdale. Was it a little unnerving? Yes
 

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1986 Sabre 30 MIII
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Discussion Starter #6
Have you tried asking Sabre what they think loading should be? Cranking up on the things has turned boats into "bananas" by trying to drive the mast through the keel, but Sabre layups are supposed to be heftier than the typical lightweight racing hull.
I have not asked Sabre. I'll give that a whirl.
 

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The primary purpose of a backstay adjuster on a masthead sloop is to eliminate forestay sag when sailing closehauled and to induce forestay sag in lighter air or when sailing downwind. Forestay sag powers up the jib, but it diminishes pointing ability. If you're not sailing closehauled, a little forestay sag can be helpful. A Look at Forestay Sag - Sail1Design

The question here is, "Is it possible to over-tension a hydraulic backstay adjuster?" Yes. When you tension a backstay adjuster, it increases the loads on the forestay, the backstay and the points where the forestay and backstay attach to the mast and to the boat. Those points aren't designed to withstand any load, however great, you put on them. The cables and each of those attachment points will fail if the load imposed on them exceeds the design limits.

On a masthead rig, the goal is to reduce forestay sag to a minimum when sailing closehauled. Rigging cable stretches a bit, but when it's tensioned, it quickly reaches the limit of it's stretch, in which case it becomes bar-tight. When it reaches that point, there is no significant amount of sag in the forestay. If you put even more tension on it, you're not reducing sag anymore. The boat won't point any higher or sail faster. You're only increasing the load on the cables and their attachment points. If you continue to increase the load, something eventually has to fail. Thus, there's no benefit to be gained by increasing the tension even further, after you have reduced forestay sag to a reasonable minimum.

To determine the maximum amount of forestay tension, you might find the following link from Selden helpful, especially on pg. 32. http://www.riggingandsails.com/pdf/selden-tuning.pdf
 

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1986 Sabre 30 MIII
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Discussion Starter #9
Have you tried asking Sabre what they think loading should be?
I reached out to Sabre, and they had nothing to offer. They replied to my query quite quickly, but only said that most of the boats like mine didn't have a hydraulic backstay which implied that it was an after-market addition, and they had no information on tensioning. Oh well... it was a good idea to ask.

I was looking more carefully at the gauge over the weekend. My stay seems to max out around 5k PSI. I typically don't exceed 1.5k on the dial. Is there a number, say 3k, that is almost assuredly safe for the rig?
 

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The Selden article that I linked said the forestay tension should be about 40% of the breaking load of the wire when you put the “maximum load” on the backstay, in strong winds. Normally, the forestay tension should be less than that, perhaps 20-25%.
 

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Discussion Starter #12
My boat had one when I bought it
It leaked
It was repaired
It leaked again
I got rid of it with new backstay
I'm not racing
I'm not racing either, but I do like to sail well. I think the most important function of the backstay is dumping power when the winds are high(er). It's a nice intermediate option when winds are at the higher end of the range before I resort to adding a reef.
 

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That's correct for a boat with a fractional rig, but not so much with a masthead rig. A backstay adjuster works very differently on fractional and masthead rigged boats.

When you tension a backstay adjuster on a fractional rig, it bends the mast and pulls the sailcloth in the middle of the sail forward, which depowers the sail. ,When you tension a backstay adjuster on a masthead rig, it doesn't significantly bend the mast or change the shape of the mainsail. It hasn't much effect in depowering the mainsail. The principal benefit of it is that, when you sail off the wind or in light air, you can ease the tension on the backstay adjuster, thereby inducing headstay sag and that powers up the jib.

If you're sailing a masthead rig closehauled in about 15 kts, the backstay adjuster should be adjusted pretty close to the maximum recommended tension. There will be negligible forestay sag. If the wind increases to 25 kts, increasing the tension on the backstay adjuster will have a negligible effect in reducing forestay sag. Once the backstay adjuster is at it's maximum recommended tension, increasing the tension even further won't depower either the jib or the mainsail.
 
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