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Old 22-07-2010, 22:53   #1
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Split Backstay Tensioner on a Ketch

I would like a way to adjust my back-stay tension on the main mast of my Ketch .

Is this accomplished the same way as a split back-stay on a sloop?...with some sort of car and block and tackle?

I dont see how this would not be a real mess to contain, as the split in my back-stay is at least 1/3 the way up the leach of my Main sail...it has to be to clear the mizzen shrouds.

Red circle shows split location
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Old 22-07-2010, 23:08   #2
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A split backstay tensioner would be more common on smaller boats, maybe? A boat like yours would tend to have a hydraulic tensioner. But you'd need a proper block at the split.

If you do use a split type tensioner, these are sold as a plate with a pair of sheaves. A tackle is used to pull this toward the deck.

Sounds like a job for a respected rigger.
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Old 23-07-2010, 03:22   #3
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Mine is split and works beautifully - a lot of tension easily!
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Old 23-07-2010, 09:40   #4
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Mine is split and works beautifully - a lot of tension easily!
So you just keep adjusting your turnbuckles all the time?....or just set it and forget it?

My understanding is normal turn buckles do not have the thread design
for constant adjustment all the time....that's not their purpose.
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Old 23-07-2010, 10:33   #5
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There are hydraulic and mechanical backstay adjusters available.

John

Hydraulic and mechanical backstay adjusters with standing rigging accessories from Rigging Only
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Old 23-07-2010, 11:18   #6
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There are hydraulic and mechanical backstay adjusters available.

John

Hydraulic and mechanical backstay adjusters with standing rigging accessories from Rigging Only
yes I know John...was hoping someone has done this here and could tell me the best, cheapest and cleanest way to go about it.

Im going to go with two hydraulic ones if there is no simpler way...one on each chain plate....just trying to find out if there is a better way I haven't though of yet ...apparently not.

I like to sail in the stiff stuff...I dont want one set it and forget it tention...Its to hard on the boat.
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Old 23-07-2010, 12:29   #7
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how about one ram and a block at the triangle plate? I've sailed on a few boats set up this way.
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Old 23-07-2010, 12:40   #8
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I have thought about this but the anchor point for any purchase is the problem...nothing can come down to the center of the deck far enough aft to clear the boom due to the Mizzen mast.. angling off to one side would skew the rake of the mast...

I have tried to engineer a pulley system that would shorten both legs at once in Lu of a car that simply squeezes the legs together but that hasn't penciled out as being particularly simple and clean either with the forces involved...at least with my limited engineering skills.
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Old 23-07-2010, 12:53   #9
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anchor one side to the chainplate, travel up to the single backstay (on the short single wire is hanging a high load wire block), pass the wire through the block, travel down to the opposite chainplate that holds some sort of a backstay tension adjuster (hyd or screw type), and attach the wire. this will pull straight down/back at the apex of the triangle w/o using two rams, even without hydraulics if desired.

see the lower right on this linked page.
Harken Tech Corner: Backstay Adjusters
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Old 23-07-2010, 13:06   #10
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Just what I was looking for!

So simple I could not see it!....Thanks SM that's just what Ill do!... I will upsize the wire one size as well.... to add a margin of safety to the constant wear point and pint loading in the middle of the new wire.

Greatly aprciated...and your advice is worth way more then what I paid...hopefully I can return the favor some day..
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Old 23-07-2010, 17:23   #11
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A block on the split and tension-ing device on one end perhaps?

b.
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Old 23-07-2010, 17:34   #12
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...that's what I tried to say on post #2. Good job making it clear Sailmonkey.

You'll want that wire to be 7x7 or whatever is flexible. Do not cheat on the wire block. Follow what the engineers say about sheave diameter and wire size.
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Old 23-07-2010, 21:06   #13
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...that's what I tried to say on post #2. Good job making it clear Sailmonkey.

You'll want that wire to be 7x7 or whatever is flexible. Do not cheat on the wire block. Follow what the engineers say about sheave diameter and wire size.
Yes sir!

Now teach me something ...why 7x 7 and not standard 6 x 19 or what ever it is...( There I go again showing you all I dont make great effort to remember things I can find out quickly)
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Old 23-07-2010, 21:10   #14
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Yes sir!

Now teach me something ...why 7x 7 and not standard 6 x 19 or what ever it is...( There I go again showing you all I dont make great effort to remember things I can find out quickly)
Lots of folks, both racers and cruisers, are using Dyneema Dux in applications like this. Relatively inexpensive, easy to splice, very flexible for going around the block... might be the answer for you as well.

Cheers,

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Old 23-07-2010, 21:37   #15
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Ya...I thought of that as well...but Im not sold on the stuff yet for applications like this...seems like an errant knife could spell and expensive day in a good blow.

But when I was fiddling with other tension designs integrating a car and blocks to squeeze the back-stays that was exactly going to be my choice.
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