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Old 14-03-2013, 20:07   #1
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Is it possible to over tension my backstay?

My newly purchased boat came with a hydraulic backstay adjuster. I understand the purpose and theory of its use. Tighten up in heavier air to flatten the sail and point higher, loosen downwind or in light air to create more draft. My question is, can I over tighten it and cause damage? Or, is a properly designed and installed adjuster "idiot proof"? The boat has a masthead rig with a roller furler and the inverted Y backstay with the manual hydraulic pump mounted at the base of one leg of the Y on the transom. The backstay adjuster was installed by the PO, not a factory installation.
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Old 14-03-2013, 20:18   #2
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Re: Is it possible to over tension my backstay?

A backstay adjuster on a mast head rig will take the sag out of the fore stay but will do little in the way of sail shaping. An adjuster on one leg of a split backstay sounds wrong to me in that it would pull the mast out of line.
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Old 14-03-2013, 21:09   #3
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Re: Is it possible to over tension my backstay?

Yes, you can over-tighten the backstay. What will give depends on the boat, but I have seen windows pop out and masts come down. Check to see how far the mast bends out of column as you tighten the adjuster--more than one diameter without a running back is asking for trouble.

In cruising mode, just tighten it up enough to keep the headstay sag down when beating, and release it down to 500-1000 pounds otherwise. Having the adjuster on only one side of a split backstay will not significanly pull things out of line.
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Old 15-03-2013, 02:00   #4
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Without a race crew's attention, the spar makers say the bend should be less that 2% of the height (I). One mast diameter is a good eyeball guide. While racing and perhaps with additional stays, the bend might be much more.

But mast bend may not be changed much by some backstays.

It's not so much head stay sag, as mentioned above, as it is headsail fullness. Headsails are cut to accommodate the inevitable head stay sag. You do what "needs to be done to get the job done". Not very helpful, I know. Going sailing with a rigger or sailmaker can straighten all these sorts of things out.

It is best to have a limiting mark, or better adjust the turnbuckles or whatever so that the backstay cannot be over tensioned. I set up my several hydraulic cylinders so that they bottom out before something bad happens. Pity to have the mast suddenly go out the bottom of the boat.

That all said, backstays are often really tight going to windward.
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Old 15-03-2013, 06:55   #5
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Re: Is it possible to over tension my backstay?

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Originally Posted by Capt.Alex View Post
My newly purchased boat came with a hydraulic backstay adjuster. I understand the purpose and theory of its use. Tighten up in heavier air to flatten the sail and point higher, loosen downwind or in light air to create more draft. My question is, can I over tighten it and cause damage? Or, is a properly designed and installed adjuster "idiot proof"? The boat has a masthead rig with a roller furler and the inverted Y backstay with the manual hydraulic pump mounted at the base of one leg of the Y on the transom. The backstay adjuster was installed by the PO, not a factory installation.
Does the back-stay cable go over a sheave at the (inverted) junction of the Y-or are both legs fixed at the junction? If both are fixed, the adjuster will pull the junction off-center which will create a number of issues.
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Old 15-03-2013, 07:59   #6
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Re: Is it possible to over tension my backstay?

The C&C "smile" is reputed to have developed because of overtensioning the backstay.
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Old 15-03-2013, 08:21   #7
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Re: Is it possible to over tension my backstay?

Does your backstay have a gauge indicating the pressure? I have a C&C 35 and would not go over 1500 pounds. It can change the hull shape!
BTW, love the H46!
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Old 15-03-2013, 10:27   #8
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Re: Is it possible to over tension my backstay?

Years ago I had a C&C 38 Landfill. I wanted to see if my hydraulic back stay could change the shape of my boat. I passed a string from front to back and measured to the deck at its center - and voila, yes it can!

Sailors I know call it "bananna'ing" your boat.

Kevin
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Old 15-03-2013, 10:47   #9
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Re: Is it possible to over tension my backstay?

I found on my 44 footer that I could bend the boat and still had sag in the furler/headstay! (that boat was right on the cusp between two models of hydraulic adjusters, so I went with the one good for up to 55 ft boat!) Without perfect rig adjustment, you could put too much compression on the mast, which is asking for a failure. It's pretty complex. Some racing boats can use it to not only tension the headstay but provide forward mast bend... flattening the mainsail in heavier air....
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Old 15-03-2013, 10:50   #10
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Re: Is it possible to over tension my backstay?

As others have said, yes you can bend the boat with the backstay adjuster. Try this, set the boat up close hauled in about12-15 apparent. Go up to the headstay and eye up the foil, you see a large sag in the sail. Have someone start to tension the backstay as they call it out. Watch carefully and you will see the headstay sag slowly being reduced. You'll get to a point that the sag is no longer changing even with tension on the backstay....stop there and take note of the tension and never go past that mark in normal operations.
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Old 15-03-2013, 10:55   #11
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pirate Re: Is it possible to over tension my backstay?

Bet ya thought 'Banana Boats' only delivered banana's..
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Old 15-03-2013, 10:57   #12
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Re: Is it possible to over tension my backstay?

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Some racing boats can use it to not only tension the headstay but provide forward mast bend... flattening the mainsail in heavier air....
Only on a fractional rig.

The Hylas 46 is a masthead rig.
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Old 15-03-2013, 12:19   #13
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Re: Is it possible to over tension my backstay?

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The C&C "smile" is reputed to have developed because of overtensioning the backstay.
;-)))))))))))))

super funny
b.
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Old 15-03-2013, 12:28   #14
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Re: Is it possible to over tension my backstay?

Generally a backstay adjuster on a cruising rig allows you to furl the headsail much easier when the wind is blowing. Some backstay tension allows the furler to turn much easier, its a nice addition just for that purpose alone.
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Old 15-03-2013, 13:29   #15
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Re: Is it possible to over tension my backstay?

Masthead rigs can use the backstay to bend the mast to flatten the main, but it has to be setup correctly. The Ranger 26 has forward lowers and inline lowers, the connectors for the spreaders are slotted. As you pull the masthead aft the forward lowers keep the middle of the mast from moving back, bending the mast. Since the top of the uppers are moving aft the slotted connectors allow the spreaders to pivot aft without trying to tear them out of the mast.

Straightening the headstay does affect jib shape similarly as mastbend affects mainsail shape. As the headstay is straightened luff curve is taken out and flattens and moves the draft aft on the jib.

Tensioning the backstay bends boats, particularly straight glass boats. Not a big deal within reason. The Cal 34 I sailed on for years you could not get the spin pole out of the deck chocks if you had forgotten to ease off the backstay set for sailing upwind. The owner once experimented with what is too much pressure. The mast has fore and aft lowers so the middle is fixed. He decided too much was sometime before when you could see the mast develop an S-curve side to side.

I've been told by other Cal 40 sailors to not exceed 2000 psi on my boat. I've run it up past that a little to see what happens. A lot more pumps for a lot less pressure gain, basically that's where the forestay isn't getting any straighter, the boat's just bending. A previous poster saying watch headstay and pressure as you tighten I think is a good idea.

Of the few boats I've been on with hydraulic backstays, all have told me a do not exceed pressure. Maybe some boats are failsafe, I haven't been on one yet.
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