Adjustable backstay modification

[harstonwood]

On our Dufour 405Gl the twin back stays terminate in two turnbuckles with split pins
I would like to be able to change the tension easily without removing split pins etc, can anyone suggest an easy modification?
I will try an post pics next week
Rig is fractional
Thanks

 

[PeteCooper]

You can rig a cross piece between the two backstays, each end has a pulley on the backstay, and then a vertical tackle pulls the cross piece downwards pulling the two backstays together therefore increasing the tension.

 

[harstonwood]

Ok will tray and devise such a system this winter
Thks

 

[PeteCooper]

This link shows a few options:

http://www.harken.co.uk/content.aspx?id=3896

 

[Plevier]

Barton Marine part no 91-040, bottom right of the page below.

 

[lw395]

Do you need a flexible wire rope for the backstays with that kind of system?

 

[DFL1010]

I can't see that option working here. The boat is forty feet long, and the two ends of the backstay terminate right at the corners. Therefore the distance between the backstays will be quite large - too large for that Barton bit. You could make something up using decent kit (i.e. not Barton...), but it'll need to be long.

The other problem is that there'll be a lot of load on the downhaul, and it doesn't look like there's many options for attaching the bottom bit. Taking it to one corner or the other will mess up the loads, and put asymmetry in the two backstay tensions. You could rig up a bridle between the corners and then rig a purchase from that, but it's ugly engineering and it'll get in the way of the swimming platform area.

I think your best bet is doing something like what Bavaria do/did: one backstay that terminates in a block, then another piece of wire from one corner, through the block to the other corner. Then either a big purchase or hydraulic (take advice - 40ft is a lot of load). Up to you whether you want adjustment on both sides or only one. Only one is cheaper, but both sides make tweaking easier - how tweaky do you want?

 

[VicS]

I can't see that option working here. The boat is forty feet long, and the two ends of the backstay terminate right at the corners. Therefore the distance between the backstays will be quite large - too large for that Barton bit. You could make something up using decent kit (i.e. not Barton...), but it'll need to be long.

The other problem is that there'll be a lot of load on the downhaul, and it doesn't look like there's many options for attaching the bottom bit. Taking it to one corner or the other will mess up the loads, and put asymmetry in the two backstay tensions. You could rig up a bridle between the corners and then rig a purchase from that, but it's ugly engineering and it'll get in the way of the swimming platform area.

Pretty much what I was thinking, esp regarding the attachment point at the bottom. Perhaps it could be clipped to one side when not in use but moved to a central attachment point when the loading bay ramp is raised.

 

[harstonwood]

That's my thought
Just clip it onto a central point when racing

 

[Debenair]

I had this discussion with Nigel Theadom of Rig Magic when I wanted to upgrade the twin back stays on my SO 36i, and we determined upon a single back stay with a flexible wire span through a Selden block terminating in a Selden screw adjuster.
Lots of power and relatively low tech. No complaints- all works well.

 

[Lon nan Gruagach]

On our Dufour 405Gl the twin back stays terminate in two turnbuckles with split pins
I would like to be able to change the tension easily without removing split pins etc, can anyone suggest an easy modification?
I will try an post pics next week
Rig is fractional
Thanks

replace split pins with

link: http://wfzy.en.alibaba.com/product/497694880-212549614/Metal_Cotter_Pins.html

Note: these are totally safe except they really like snapping your thumb when closing.

 

[Plevier]

Oops do your twin backstays go all the way up? Sorry I assumed they joined above head height. If they go all the way up this is not the right answer.

However, answering comments about the Barton item:

I used it on a 32ft boat (Sun Odyssey). It worked very well. The downhaul load is not great - the mechanical advantage of squeezing the wires together is huge - and it worked perfectly OK taken to one side, not to the centre. I had assumed it needed to be central, Barton said no it didn't, they were right. AFAIR I put a 3:1 haul on it because I had the bits kicking around, that was enough. I had quite a long strop between the upper block and the Barton fitting to minimise rope length.
No you don't need the flexible wire rope, you can use ordinary 1 x 19.( Again, that's the advice from Barton.)
It is a short spacing so you start with it right up at the top of the fork. That's the way to get most advantage and minimise the bend angle in the wires. Not a good idea to make a long one and bring it lower (you might also catch your hair in it). Look at the Harken suggestion - 2 blocks coupled directly together, no spacer in between (plus a 3rd downhaul block).
The larger of the two models is for wire rope up to 10mm dia. I doubt if a 40ft boat has a bigger backstay than that!
You could ask Barton, they are very helpful by phone or email.

You can see it in the background here

 

[Daydream believer]

Use 2 blocks that can be opened up & placed around the wires
Couple them with a dynema loop. On the dynema loop have a central fixing point to which a block & tackle is fitted to draw the blocks down thus pulling down on the 2 pullies thus pulling the stays together
Experiment with length of loop between the 2 blocks

 

[Judders]

I was out on the mooring yesterday as a procession of shiny new generic cruisers went past on their way to the boatshow. Not many caught my eye but funnily enough the Grand Large 385 did. It had the twin backstage as you describe with a simple pinch system about half way up. The control line then lead down the port backstay. It looked terribly simple, if perhaps a little under engineered.

 

[Woodlouse]

replace split pins with

link: http://wfzy.en.alibaba.com/product/497694880-212549614/Metal_Cotter_Pins.html

Note: these are totally safe except they really like snapping your thumb when closing.

These are an alternative and will save your thumbs some grief.
http://www.csjohnson.com/store/index.php?main_page=index&cPath=9_14

 

[harstonwood]

Thanks all
Will have a go at this project this winter

 

[30boat]

I made a simple 16:1 tackle that bends my mast with very little effort.My boomjack is the same. Very effective.

 

[harstonwood]

Would the above be suitable to attach to the back stays and then fit a block to each with dyneema across the stays a block in the middle and then a 16/1 block arrangement down to the deck? I could stow this at the side when not in use?
Alternatively it's a change to a single backstay splitting to two 3m above the deck but am not sure how to go about this without examining the masthead
Any thoughts?