If I tie a knot in my halyard...

Kelpie

Kelpie

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Dinghy-related question: I need to replace the jib halyard, which has a wire part connected to a rope tail. It's currently set up so that you pull the wire down the mast, tightening up the sail, and an eye on the wire attaches to a ahook; this hook is part of a pulley system that applies a 12:1 force to get better luff tension.
For a number of reasons, I'm tempted to replace the wire with 5mm dyneema. However, in order to attach it to the hook, I'd have to make a bight in it every time I used it.
Apart from being potentially a bit of a pain, and one that I'd live with, will constantly tying a knot in the same place weaken the rope? Any other considerations?
 
Tying a knot in dyneema, spectra or kevlar will weaken it significantly. I don't have the figures to hand but if I recall it's between 50% and 90%. The correct way is to splice it, which I don't think helps you very much. Could you try pre-stretched polyester?
 
Stay with the wire halyard, its the only way you are going to get enough tension on the halyard, to be able to point up on a tack, if you use a rope halyard you won't get enough tension, so having to tack more to get up wind, and maybe not getting there at all...
 
I don't understand. If the bight in the dyneema replaces the eye in the wire why would you have to retie it each time - the eye is permanent so why isn't the bight?
 
Is this a modern dinghy where the jib luff holds the mast up?
If so I would stick with wire.
If you must go to dyneema, invest in a 'hollow splicing needle', use braided core such as Marlow Excel racing or better and it's not too hard to splice.
By the way, if the ends of the wire are simple talurits not roll swages, you can get the tool to make your own wires very effectively for under £30.
Look at websites like Rooster sailing and Northampton Sailboats.
 
[ QUOTE ]
I don't understand. If the bight in the dyneema replaces the eye in the wire why would you have to retie it each time - the eye is permanent so why isn't the bight?

[/ QUOTE ]I suspect that's because a permanent eye in 5mm line would be too bulky to pull through the sheaves.

Our Wayfarer used a 3mm wire halyard, with a soft eye to put onto the tensioner (highfield on our boat). There was a tail of 4mm line spliced onto that soft eye and used to pull the wire through. The wire soft eye and the joint onto the tail all need to able to pass round the sheave at the mast foot.
 
What is the dinghy?

I replaced the wire one on my racing Enterprise with dyneema and use a knot in the right place to make a loop for the Highfield lever. No problem but it depends on the size of rope which depends on the type of dinghy and the loads you are going to apply....... /forums/images/graemlins/smirk.gif
 
Dyneema and Spectra wich are the same thing don't get significantly weakened by knots.It's Kevlar that does.The right size in Dineema will be as strong as wire and much more user friendly.
 
In my case yes the luff was used to apply the rig tension using a highfield lever. My experience was it was just as effective as wire, more pleasant to handle, easier to inspect though I never had a spectra halyard fail whilst it was not uncommon with wire.

The best education is wandering around the dinghy park as people are rigging their boats and talking to them
 
Thanks for all the replies. FYI it's a Wayfarer, and yes the luff tension overtakes the forestay when you haul it tight. I've read that dyneema is 'almost as low stretch as wire' so thought it would be up to the task?
As others have explained above, the current system involves a soft eye with attached rope tail having to go through a sheave; this is only possible because the wire is so much thinner than the dyneema would be.

I actually don't want to replicate the current system for another reason: it's really hard to get the foresail down at sea. Firstly you have to unhook the wire eye, which is surprisingly tricky, and then often as not the eye/tail joint jams as it enters the mast- leaving you with a big baggy sail flapping like crazy. I just think it's unsafe not be able to drop the headsail when I want to, because the dinghy would broach easily if allowed.

Having thought about this all some more, I'm considering a new system: the (dyneema) halyard exits the mast, goes around the tensioning hook, and is then cleated off on a cleat mounted on the mast. This avoids the knot, and makes dropping the sail even quicker. It even gives me an extra 2:1 purchase on the tensioning system. Win win situation?
 
A standard dinghy highfield lever will do the job for you and allow you both greater tension and fast release with ease. As an alternative to the highfield lever there are also muscle boxes which have an internal 10-1 system, these allow easy alteration of tension whilst sailing, where as with the highfield lever tension can be altered but only by completely releasing the tension.
 
Highfield levers and mussel boxes are a bit old hat nowadays.
Most dinghies just use a cascade purchase with a hook to the wire or other halyard.
Your highfield lever if I understand what you are proposing will be working at a mechanical DIS advantage of 2:1.
If you have a separate standing forestay there is no harm in trying a rope halyard, worst case your jib falls down, not the mast!
For all the claims about the low stretch of dyneema, wire is still favoured when there is nothing else holding the mast up!
Maybe you could make your current system a little better by taking some slack out of the standing forestay, so that the jib luff still does all the work, but you have more slack in the halyard when unhooking the highfield. Leading the halyard tail beyond the highfield to a turning block (maybe even a cleat?) makes it easier to hold the jib up while hooking/unhooking the lever.
 
Why don't you consider roller furling instead - the Laser2000, Buzz, Stratos have these and it is available on the 505 as well - means you keep the forestay tension, but can get rid of the jib when you don't want it - which we used prior to racing or in-between when doing back2back racing.
 
Dyneema has a higher breaking strain and less stretch than wire. However, a permanent loop tied with a bowline will reduce it's breaking strain by just over 50%, which is quite a drop in performance. The strongest way is to splice it, with the correct fid it's the easiest stuff in the world to do. Literally a five minute job.
 
The tensioning system is a muscle box. My question isn't about how to put tension on the jib. The current system does that just great. It's about finding something more user-friendly that I can drop in an instant.
Oh my idea about adding a cleat and hooking the halyard round the tensioning hook does, of course, lose me some purchase- silly me. Back to the drawing board?
 
you can just cleat on the halyard if you wish - or swap the hook for a cleat...

alternatively - I'll repeat my suggestion of roller furler ....
 
As people have pointed out, you will lose some breaking strain with a knot, perhaps up to 50%.
This does not matter as the rope will be oversize for the load on it.
You may find that knot that have been highly loaded are not instantly easy to undo with wet fingers etc.
A good system which we use on keel boats is halyard with loop and tail. Tail gets cleated, (we use a strong harken cam cleat, but a horn cleat would do).
A separate 6:1 tackle with a hook on the end is then slipped into the loop to apply tension.
To drop in a hurry, make sure tail is cleated, release tackle, remove hook, lower from cleat. We can get the jib up and down during a race like this if the system is well laid out. We sometimes drop jib with the kite up, and want it back up and tensioned at the leeward mark.

On my dinghy we just have a long soft eye in the wire, a hook on a cascade tackle is easy to use becasue the tackle has much more travel than a muscle box or highfield. We never drop the jib afloat though, as it holds the mast up.

Used to have an old 505 with a roller furler, that really was a good option. I would seriously consider it for an 'all purpose boat'.
 
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