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Old 19-10-2018, 02:17   #1
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Double back stay tensioner

Hi all, I replaced my rigging approx 18mths ago and have done approx 10k nm since.

The short backstay up top that connects the twin back stays to the mast was a little long for my liking, it didn't provide enough adjustment for if/when the ringing stretched. At the time of replacement I suggested to the rigger that it was a little long but he assured me it was fine.

I've just crossed the Mozambique channel and are hiding from weather at Bazaruto Mozambique. The crossing was easy but one day I had to beat 40į off the wind and I noticed the the top of the mast flexing forward, considerably more than I would like. Earlier in the year it was tough beat from the Seychelles and the rigging has stretched. I have no backstay adjustment left.

I can easily remedy the problem when I reach south Africa, but that's 500nm away.

Now, I think it will be ok BUT I don't want to risk it. My options are rake the mast forward abit, lossen the aft lowers and tighten the forestay which in turn will tighten the backstays, this involves dismantling the furler which I'd prefer not to do in our current winds. It's easy to do but if I lose something I then have a problem and getting the sail down isn't so easy at the moment.

My other option is to use a couple of blocks as a tensioner, feed a stay through each block (up high) run some dyneema down through a third block then through several Frictionless rings in a cascading arrangement providing purchase. By pulling the dyneema line and then cleating of I should be able to tension the back stays and adjust as nessacary. Something similar to the below.
https://c320.org/article.php/20120828164453754

I have all I need onboard to do this.

I'm interested in any thoughts/opinions regarding these options. Any downside to implementing the tensioner idea?

Thanks in advance.
Cheers Dale
Sukha.
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Old 19-10-2018, 02:35   #2
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Re: Double back stay tensioner

I think so long as your blocks and the hard points for the cascade/cleat are robust enough you should fine. Assuming a very rough max backstay tension of 1500lbs. I canít see those being a problem. The only other potential issue I can think of is bending the wire at too acute an angle when itís tensioned but again I doubt youíll get anywhere close to that if you mount the blocks up as high as possible.
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Old 19-10-2018, 02:55   #3
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Re: Double back stay tensioner

This was a pretty standard setup back in the day. The only point of caution, you want as large a diameter sheave on the wire as you can get - it limits the bending radius of the dual-backstay wire. Smaller sheaves, with a fair amount of tension on the system can put a pretty good kink in the wire. What actual diameter depends on size of wire and angle of bend when tensioned.
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Old 19-10-2018, 04:06   #4
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Re: Double back stay tensioner

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Originally Posted by Dsanduril View Post
This was a pretty standard setup back in the day. The only point of caution, you want as large a diameter sheave on the wire as you can get - it limits the bending radius of the dual-backstay wire. Smaller sheaves, with a fair amount of tension on the system can put a pretty good kink in the wire. What actual diameter depends on size of wire and angle of bend when tensioned.
The blocks I'll use on the stays are Garhauer blocks that can hold 5/8 rope, the sheave diameter is approximately 3 3/4 inch , quite large blocks. Ill have to check load rating of a couple of the smaller frictionless rings, these will be supported by being eye sliced into dynemma line of more than adequate strength.
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Old 19-10-2018, 10:11   #5
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Re: Double back stay tensioner

Raking the mast forward depends on current rake. You dont want to have the mast straight or raked forward.
If it is raked back much, you can take the mast a little forward but you need the rake especially when beating and in bad weather. So it seems that the tensioner is a better idea as it will give you also the option of freeing the mast for downwind work.
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Old 19-10-2018, 10:21   #6
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Re: Double back stay tensioner

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Originally Posted by meirriba View Post
Raking the mast forward depends on current rake. You dont want to have the mast straight or raked forward.
If it is raked back much, you can take the mast a little forward but you need the rake especially when beating and in bad weather. So it seems that the tensioner is a better idea as it will give you also the option of freeing the mast for downwind work.
Hi, this mast isn't meant to have any rake forward or back. Catalina & sparcraft specify it to have no prebend.

Raking it forward would only be a temporary measure to get a little more tension on the back stays until I make the appropriate stay replacement.

I don't believe it would hurt the mast in anyway but it would hurt windward performance, which isn't a concern presently.
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Old 19-10-2018, 10:25   #7
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Re: Double back stay tensioner

Dale,

I just had the thought that we are currently in Richards Bay. I could look around here for a Norseman/Sta-Lok field installable fitting if you like. No idea how reliable post is between here and there, but it's not too far. It's coming on Saturday, but could check the local shops in the morning. If interested, wire size and pin size?
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Old 19-10-2018, 10:39   #8
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Re: Double back stay tensioner

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Originally Posted by Dsanduril View Post
Dale,

I just had the thought that we are currently in Richards Bay. I could look around here for a Norseman/Sta-Lok field installable fitting if you like. No idea how reliable post is between here and there, but it's not too far. It's coming on Saturday, but could check the local shops in the morning. If interested, wire size and pin size?
Hi, thanks for the offer it's appreciated. I think I'll be right, I'm fairly confident my fix will do the job. It's not super bad, it's just I don't want to risk it, particularly if we hit some bad weather.

On another note, we've been here for a week and I can't see a weather window coming anytime soon, it looks like your getting weather coming through regularly at Richards Bay at the moment.
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Old 19-10-2018, 10:40   #9
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Re: Double back stay tensioner

Quote:
Originally Posted by daletournier View Post
Hi, this mast isn't meant to have any rake forward or back. Catalina & sparcraft specify it to have no prebend.

Raking it forward would only be a temporary measure to get a little more tension on the back stays until I make the appropriate stay replacement.

I don't believe it would hurt the mast in anyway but it would hurt windward performance, which isn't a concern presently.
In the end it will be your decision and you are the best positioned to judge all parameters.
Just one extra comment - prebend is not identical with rake!
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Old 19-10-2018, 10:43   #10
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Re: Double back stay tensioner

We've been here about a week and a half. The first three days we had a nice, warm northerly. After that the SW filled in and it's been rainy and windy. A one day break last Monday, and another one today, but quickly followed by more rain and S wind.

Right now looking like we'll have 3 days or so a the beginning of next week, which will get us down to Durban, but so far only seeing 2-3 day breaks.
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Old 19-10-2018, 13:13   #11
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Re: Double back stay tensioner

Go with your own suggestion and use two snatch blocks to set up a tensioner like this:
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Old 24-10-2018, 20:11   #12
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Re: Double back stay tensioner

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Originally Posted by jt11791 View Post
Go with your own suggestion and use two snatch blocks to set up a tensioner like this:
That's essentially the setup we have on our J/36. The tackle we have pulling down is 4:1 too. As suggested above, large diameter sheaves might help avoid kinking the backstay wires. It's worked for us for more than 20 years. K.I.S.S. The other ideas you suggest are a lot more work and perhaps not as effective. Doing this should enable you to keep your mast where you want it and also tighten your forestay for upwind work.
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