Hydraulic Backstay Adjuster

Kings Gambit

Kings Gambit

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Jul 27, 2011
5,180
Bavaria 38E Alamitos Bay
My rigger just installed an integral hydraulic backstay adjuster (split backstay), replacing the block (purchase) system originally on the boat. Now I can adjust the backstay tension with one arm/hand while steering and while facing forward!! Previously, I had to face aft to tension the backstay using the block (2 x triple-sheeve block) system with both arms engaged pulling up from the transom.

But, it looks mighty powerful. The rigger even upgraded the wire rope forming the split. The Bavaria 38E is a 7/8 fractional rig. We're testing it this afternoon, if lucky. Any suggestions on how many lbs of tension might/should be applied; or how to adjust to the proper tension while under sail, etc. It has a tension gauge. I can chat with the rigger, but on Monday/Tuesday, not today!!
 
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dlochner

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Jan 11, 2014
13,993
Sabre 362 113 Fair Haven, NY
Back in the day I had a hydraulic backstay adjuster on my Sabre 30 and crewed on a J-35. On both boats we looked at the sail and sail trim and pretty much ignored the gauge. The gauge on my boat eventually failed.

Some sailors tape a batten to the hydraulic cylinder with markings for various settings. The batten extended up to the end of the rod and measured how far down the rod pulled the backstay. It was much easier to do this than try to read a little gauge.

While there is tremendous power in the adjuster, you can feel the tension. Over time you will get a sense of how much pressure to put on the backstay, just as you have with the original backstay adjuster.

Don't be alarmed if when releasing the tension it sounds like the mating call of a humpback whale. If it sounds like a herd of whales you put too much tension on the backstay. Likewise if the mast comes down. :biggrin:
 
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jssailem

jssailem

SBO Weather and Forecasting Forum Jim & John
Oct 22, 2014
24,516
CAL 35 Cruiser #21 moored EVERETT WA
How much tension?
Less than will crack the mast in to pieces, or compress the mast base through the bottom of the boat.
You don’t want to rip the chain plates up, so less tension than that. If after tension is applied you find the doors inside sticking or not closing you have too much tension.
One last sign you have too much tension, the bow starts to come out of the water.:)
 
Kings Gambit

Kings Gambit

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Jul 27, 2011
5,180
Bavaria 38E Alamitos Bay
So, the gauge reads "PSI"-- of inside the cylinder, I'm supposing. Goes pretty high--to 5,000 psi. Cannot imagine getting anywhere near that figure--but?? I assume cylinder psi goes up as the cylinder rod is retracted to tension the backstay. So, would that be the actual forcing on the rigging?
 
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dlochner

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Jan 11, 2014
13,993
Sabre 362 113 Fair Haven, NY
Kings Gambit said:
So, the gauge reads "PSI"-- of inside the cylinder, I'm supposing. Goes pretty high--to 5,000 psi. Cannot imagine getting anywhere near that figure--but?? I assume cylinder psi goes up as the cylinder rod is retracted to tension the backstay. So, would that be the actual forcing on the rigging?
Click to expand
Yes. Gauges are usually most accurate in the middle of the range. Look at the backstay and the wire size. From there you can get the breaking strength. Appropriate tension will be somewhere around 10-15% of breaking strength. Less tension for downwind and light air, more tension for upwind and heavier air.
 
J

JohnShannon

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Jan 4, 2010
1,037
Farr 30 San Francisco
I guess the answer is what is the safe load of your rigging system, and how does the PSI gauge correlate to that.
I often wondered about that as I pumped away on my hydraulic backstay adjuster. I never found out. I had thought that the PSI in the cylinder related to the PSI in the wire, which is true, but there are many other things in the systems like little tangs and fittings and so forth so a complicated question. How far could your old system pull the mast? That could be thought of as at least one known safe level of tension.
 
jssailem

jssailem

SBO Weather and Forecasting Forum Jim & John
Oct 22, 2014
24,516
CAL 35 Cruiser #21 moored EVERETT WA
I like @dlochner ’s suggestion. I’d start at the lower end 7-10% measured with a loos gauge while monitoring the psi of the tensioner, and start a chart while observing the effect on the mast and rigging.
My manual Winchard has numbers and a red slider that goes up or down as I add tension and release it. We used the loos gauge on the back stay, compared it with the tension being placed on the forestay. Having a deck stepped mast I checked the door to the head to see how much compression was placed on the deck. It was amazing how much deformation was possible. I was cautioned to release the tension when I leave the boat. Not good to keep the compression on the mast while at rest.
 
shemandr

shemandr

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Jan 1, 2006
7,980
Slickcraft 26 Sailfish
jssailem said:
How much tension?
... If after tension is applied you find the doors inside sticking or not closing you have too much tension.
Click to expand
This is funny because a Tartan 37 of a story the owner of a Tartan 37 in our fleet tells. He put an hydraulic backstay adjuster on the boat. He was racing and at the helm when he got a call on his cell phone. It was a female crew member who was stuck in the head unable to open the door because the hydraulic backstay adjuster was bending the boat. They released the backstay and she got out to join the crew again.
Those things are powerful. I've posted before it's not that hard to bend the boat.
 
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dlochner

.
Jan 11, 2014
13,993
Sabre 362 113 Fair Haven, NY
shemandr said:
This is funny because a Tartan 37 of a story the owner of a Tartan 37 in our fleet tells. He put an hydraulic backstay adjuster on the boat. He was racing and at the helm when he got a call on his cell phone. It was a female crew member who was stuck in the head unable to open the door because the hydraulic backstay adjuster was bending the boat. They released the backstay and she got out to join the crew again.
Those things are powerful. I've posted before it's not that hard to bend the boat.
Click to expand

ROTFLMAO! :D:D
 
Kings Gambit

Kings Gambit

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Jul 27, 2011
5,180
Bavaria 38E Alamitos Bay
shemandr said:
This is funny because a Tartan 37 of a story the owner of a Tartan 37 in our fleet tells. He put an hydraulic backstay adjuster on the boat. He was racing and at the helm when he got a call on his cell phone. It was a female crew member who was stuck in the head unable to open the door because the hydraulic backstay adjuster was bending the boat. They released the backstay and she got out to join the crew again.
Those things are powerful. I've posted before it's not that hard to bend the boat.
Click to expand
I love i!!:laugh:
I remember several instances sailing my P-30 close-hauled, hard on the wind, in a good breeze. The boat would "twist" some so that the hatch boards could not be taken out or put in.
 
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Kings Gambit

Kings Gambit

.
Jul 27, 2011
5,180
Bavaria 38E Alamitos Bay
I chatted w/ me rigger today. He reminded me that b/c w/a split backstay there's a sheave (block) between the two stays running to the transom and the single stay running to the masthead above the block, the force at the masthead is 2x what you read on the gauge in-line on one of the splits to the transom padeye. Whatever force is indicated on the gauge, twice that amount is "felt" at the mast head.:yikes:
 
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FastOlson

FastOlson

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Apr 8, 2010
2,237
Ericson Yachts Olson 34 28400 Portland OR
Agree that some caution is good. Our boat came with a hydraulic BS and we leave the stay unloaded at the dock and use about 800 to 1000# hard on the wind. This is a masthead rig. YMMV, as they say.
 
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