Backstay Tension

[Ianburtoncamera]

I've a Bav 40. 2001. I only use the running backstay to tighten the rig in stronger conditions to flatten the main (which I think is right), but I am unsure how tight is right and how slack to let it off when finished with it.

This feels rooky to me, and I almost feel embarrassed to ask this stuff but I've drawn a blank on searches online.

there is a piece of tape (marked with the arrow on the attached image) on the opposite side of the middle block, should this be inline with the block when slack or tight (seems logical) or is this just a red herring?


Cheers

Ian

[tiger79]

The Selden Tuning Guide is a useful reference, and it has detailed instructions on how to set up your rigging, including tensions and how to measure tension.  You can download the guide here - http://www.seldenmast.com/files/1456145028/595-540-E.pdf

Bear in mind that with the split tensioning on your backstay, the two "legs" share the load, so if you need say 20% tension, you'd look to have 10% in each leg of the adjuster.  As there's a block, you only need to measure it on one side.

[Ianburtoncamera]

Ah fantastic Thank you Tiger79

That's the sort of thing I have been searching for.

Its says use tape to mark the normal and tensioned positions, whic h I obviously have one of them, but how to you know when it's tensioned right, I wouldnt know how to measure 10 or 20%? Ive read the tention pages of the attachment you attached, It may tell me somewhere but I haven't read all the way through.

[Ricd]

I have a B34 and the rig is basically the same.  I run the rig under tension pretty much for everything except down wind when I let the tension off a touch.  Under tension for me means pull it on pretty much fully and a bit more in a blow. I don't think the rig that sophisticated to worry about exactly how much tension to have on it and there are probably many more other influences on how well your boat performs than worrying too much about rig tension. 

[tiger79]

but how to you know when it's tensioned right, I wouldnt know how to measure 10 or 20%? Ive read the tention pages of the attachment you attached, It may tell me somewhere but I haven't read all the way through.

Page 32, simple method, works every time, or you could buy/borrow a tension gauge.

Your bit of tape up in the sky is useless as a tension indicator.  What you should consider doing is marking the rope on the backstay adjuster.

[Ianburtoncamera]

but how to you know when it's tensioned right, I wouldnt know how to measure 10 or 20%? Ive read the tention pages of the attachment you attached, It may tell me somewhere but I haven't read all the way through.

Your bit of tape up in the sky is useless as a tension indicator.  What you should consider doing is marking the rope on the backstay adjuster.

Yeah I was thinking the same thing, i will have a look this weekend, Thanks.

[Symphony]

The backstay does little to tension the rig as that is done by the main and lowers. The only real reason to change the tension is to flatten the main by bending the mast. So it is infinitely adjustable rather than having a fixed tension. The asme backstay is used on the in mast which cannot be be bent so tension is fixed and quite low. The backstay on my old 37 was never adjusted in the time I had the boat (13 years) except when the mast was restepped after road transport. The rigger just put it back exactly as it was.

[Neil]

I have the same rig on my B39 2006. I have two bits of tape on the rope at the jammer noting the off and fully on extremes. They are about 25cm apart (I'm guessing here). I leave it eased off when in port - at least when I remember!
It is useful to have it on a bit just before hoisting the main in a position that allows the sliders to slide easily in the track. This is easy to play with to see what works best.
Also keep an eye on the genoa halyard when tensioning to ensure that it is the forestay taking on the opposing tension at the front of the rig and not the halyard. It is good practice to ease it and then re-tension after putting some backstay tension on until the effect is fully understood.