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Old 04-12-2008, 11:42   #1
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Backstay tension adjuster

I'm looking to add one. My boat is 38' LOA with 43' / 14' mainsail luff & foot. It has a split backstay and a baby stay and I want to improve her pointing abilities.

Would anyone know:
- What stroke / maximum tension should I spec for it?
- By how much would my boom aft end go down? (have a bimini to consider)

There are 2 designs that I have seen: wheel and pneumatic. A wheel is cheaper and presumably fail proof (?) but don't know if it is feasible for a boat this size.
Anyone has experiecne with a similarly sized boat? Which make / brand of adjuster?

Thanks -

Eldad
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Old 04-12-2008, 13:14   #2
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Eldad:
Get a Harken catalog.
Go to page 100, Stay tensioners.
You will need to run your backstay over a sheave.
These are simple and very effective worm gear type that can be adjusted with a winch handle. The B503 is probably right for your boat but I would certainly check with the Harken rep. Call Don Whelan at 619-475-0712. Don will tell you what size to use.

Your outboard end of the boom should not drop appreciably as you will not get much movement in your mast at the gooseneck.
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Old 04-12-2008, 17:36   #3
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Harken Backstay Adjusters

* * *

Bob, I've got a nice hydraulic backstay adjuster with a dial and numbers than mean nothing to me. How much do I tighten the backstay? Dumb question I know but I just go by feel and looks. I probably undertension out of fear of over doing it.

Navtec brand; don't know which model. Looks like this. http://mauriprosailing.com/Merchant2...ory_Code=NAVBA
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Old 04-12-2008, 18:28   #4
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Hi: this is a questuion that goes back to the early '70's and the advent of hydraulic backstay adjusters. All of a sudden we had all the tension we could ever dream of having. How much is enough.

The key to understand this is to know that your dial reads in PSI and not actual pounds of tension. I suspect you have to multiply your dial by a factor based upon the dimensions of your cylinder to get the actual tension, 2.79 is a number that remains in my memory. But 3.14, 38D, 1.69 and 789-6400 are other numbers that remain in my memory.

So, here's what you do. You cover the dial with duct tape and pump up the backstay till things look right and you call it good. Figure on most 40'ers the backstay will be at least a 5/16" dia wide so that's good for 12,500 lbs. and you are not going to get there.
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Old 04-12-2008, 19:55   #5
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Good to know I finally got somthing right.

P.S. I like your numbers.
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Old 05-12-2008, 04:24   #6
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Hey John,

The number for my hydraulic backstay adjuster is 1.1, so I can get away with reading the gauge directly. All of my rigging is -10 rod, meaning it has a tensile breaking strength of 10,000 pounds. So I don't pump my cylinder up to higher than about half-way between the 2 and the 3 on the gauge, even though the gauge goes up to 5.

You know what comes after too tight?















too loose!

(this applies to torquing nuts, bolts, and screws as well)

Tim
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Old 05-12-2008, 06:07   #7
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Mine goes to 11.
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Old 05-12-2008, 09:15   #8
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Pneumatic or Mechanical still undecided

I have a navtec pneumatic vang and back stay adjuster that a friend gave me. Had the vang reconditioned. I have been going back and forth about installing the pneumatic back stay adjuster, seems like more to go wrong with leaking seals and such. As I am a mast head rig and do not need the instant performance that a pneumatic back stay provides. Crunch time is coming as I am nearing a time to make a decision, getting closer to finishing the refit. Would be interested in opinions, the thing I like about the mechanical is it will be allot harder to overload the rig due to the fact that one has to go back to the back stay and crank a handle verses someone pumping a handle in the cockpit thinking they are adjusting the vang etc.
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Old 05-12-2008, 09:53   #9
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I'd go with the hydraulic. They seldom leak and can be let off quickly. I think the manual Harken units may not be big enough for your boat.
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Old 06-12-2008, 08:25   #10
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Thanks for that Bob. I sailed on Stealth Chicken a while back nice boat.
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Old 06-12-2008, 13:36   #11
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Hiracer -

It's really simple to determine how much to pump it up: Pump until the stemhead fitting pulls off the deck, and then back off a little bit!
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