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Old 25-05-2015, 04:54   #1
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Dyneema Loops/Blocks as an Alternative to a Jib Car

This thread is inspired by Dockhead's thread here:
Splicing Advice -- Dyneema

As this thread is above thread about splicing I thought it was better to start a new topic on this application.

Dyneema is revolutionising sailboat fittings. The advantage is mainly in reducing weight for the keen racing crowd, but there are lots of applications for cruising boats.

One of the big advantages is the sheet lead can easily be moved inboard or outboard, for example to the toe rail, without re threading the jib sheet line (as well as the normal forward and back). Thus it is far more adjustable than a traditional jib car.

The jib and staysail track require a lot of stainless steel bolts. The dissimilar metal is not ideal for an aluminium boat. In addition, I have seen problems if the tracks or cars need replacement. A new version often does not fit the bolt spacing of the old track or a new track car is no longer available to fit the track profile.

There are a number of Dyneema blocks or even simple loops that I think could replace the traditional car and track systems, especially on an aluminium boat. These can be attached to deck loops that are welded on. Fibreglass boats could still take advantage of the system with stainless loops.

Simple, cheap (at least much cheaper than a conventional track), easily replaced, and low maintenance (especially the loops). It seems to fulfil most of the criteria important to a cruising boat. The more adjustable sail shape and light weight are bonuses.

Thumbs up or down?

Here is an example from one manufacturer. It is not obvious from the photo, but even the block can be unclipped and moved, say to the toe rail if a wider sheeting angle is desired. This can be done while the jib sheet remains threaded through the loop or block.






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Old 25-05-2015, 05:34   #2
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Re: Dyneema Loops/Blocks as an Alternative to a Jib Car

Save weight. Improve performance. Seems like a no brainer.

Thing that gets me is when this set-up is referred to as being a "new thing" since twing lines have been around for years. Granted, mostly on spinnaker sheets, but that is basically all these are. Twings.

Have used snatch blocks to adjust jib leads when reaching as well.
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Old 25-05-2015, 05:40   #3
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Re: Dyneema Loops/Blocks as an Alternative to a Jib Car

Here's another.
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Old 25-05-2015, 06:15   #4
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Re: Dyneema Loops/Blocks as an Alternative to a Jib Car

I like the idea so please don't take this as a negative post. I like to ask questions as a way of getting a better picture in my head of an idea.

So is the idea to install a row of say 8 loops welded to the deck in place of the conventional jib track? Or is the idea to use the toe rail as the fore/aft locator and use a twing to move the lead inboard as desired?

It may be difficult to get the lead down close to the deck like a conventional jib car. The shackle loop needs enough length for proper tails. Sometimes you can double the loop as in the first picture but even so it will generally result in the jib lead being higher above the deck. As long as the lead to the cheek block aft of the winch is fair then there is only a slight performance hit for the higher lead. Position can most likely address that.

If you have multiple loops in the deck what prevents attaching a conventional block at these locations? Aside from weight what advantage is in the spectra shackles?

UV is a concern with single braid as is salt crystals. The loops need to be replaced periodically.

Have you tried the jib lead cars that are infinitely adjustable from the cockpit? For cruising this is a real advantage IMO. If I were going to make any change to the jib lead system I would want the lead to be adjustable fore and aft without crawling out there and fighting with a bar tight sheet. I like rolling hitches as much as the next person but the plain fact is that we don't optimize jib leads as often as we should because of the hassle in moving the car. How is this idea going to make it easier (and safer) to fine tune the jib lead?
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Old 25-05-2015, 06:37   #5
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Re: Dyneema Loops/Blocks as an Alternative to a Jib Car

I can confirm, after sailing 1000 miles with my new sheet leads, that they work great, much better than any cars.

What I have (to anyone who missed my sheet lead thread) is a triple-purchase arrangement on the rails which grabs the sheet with an Antal low friction ring, with the control lines led aft through stanchion blocks to a turning blocks at the quarters. There are clutches on the rail near the cockpit. Those are the outboard control things, which tweak the jib sheet down and outboard.

Inboard, I use my staysail sheet which tweaks the jib sheet down and inboard.

You can use these controls together in order to position the sheet somewhere between the far inboard and outboard positions. We have been sailing mostly off the wind, however, so the outboard controls have been used almost exclusively.

They work as smooth as butter, with lovely light action due to all the purchase. Completely different from the brutal, high load action of the regular jib cars. The low friction rings seem to have less friction than blocks.

Jib cars work in only one direction -- tweaking the sheet lead angle up and down. But this system works in three dimensions, letting you tweak it inboard and outboard as well.

This ability opens up whole new worlds in sail trim, giving great control over the leech. Now I never want to go back to cars. It's so good that I have not been able to force myself to put up my new yankee, because I have so much enjoyed using the blade jib with these new leads.

The only negative so far is chafe of the sheets on the shrouds, which has basically destroyed two new sheets . I am trying to figure out a solution to that.

I will post photos when I can.
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Old 25-05-2015, 06:40   #6
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Re: Dyneema Loops/Blocks as an Alternative to a Jib Car

Quote:
Originally Posted by transmitterdan View Post
I like the idea so please don't take this as a negative post. I like to ask questions as a way of getting a better picture in my head of an idea.

So is the idea to install a row of say 8 loops welded to the deck in place of the conventional jib track? Or is the idea to use the toe rail as the fore/aft locator and use a twing to move the lead inboard as desired?

It may be difficult to get the lead down close to the deck like a conventional jib car. The shackle loop needs enough length for proper tails. Sometimes you can double the loop as in the first picture but even so it will generally result in the jib lead being higher above the deck. As long as the lead to the cheek block aft of the winch is fair then there is only a slight performance hit for the higher lead. Position can most likely address that.

If you have multiple loops in the deck what prevents attaching a conventional block at these locations? Aside from weight what advantage is in the spectra shackles?

UV is a concern with single braid as is salt crystals. The loops need to be replaced periodically.

Have you tried the jib lead cars that are infinitely adjustable from the cockpit? For cruising this is a real advantage IMO. If I were going to make any change to the jib lead system I would want the lead to be adjustable fore and aft without crawling out there and fighting with a bar tight sheet. I like rolling hitches as much as the next person but the plain fact is that we don't optimize jib leads as often as we should because of the hassle in moving the car. How is this idea going to make it easier (and safer) to fine tune the jib lead?
One wants to use not the devices shown in Noelex's photos, but a purchase arrangement, with control line led to the cockpit, which allows you to remotely adjust the sheet lead. I'll post photos when I can.

So you can adjust the sheet lead angle not just up and down, but inboard and outboard, all from the cockpit.
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Old 25-05-2015, 06:52   #7
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Re: Dyneema Loops/Blocks as an Alternative to a Jib Car

In the second photo I posted you can see a pretty typical arrangement I have seen on class mini's and class 40's though the one pictures is a pogo. That is, inboard (blue) and outboard (red) twings with a two-to-one purchase that return to rope clutches mounted in the cockpit.

Same thing in the first photo, but that one includes a bit of shock cord on top to stop the works from knocking on the deck.
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Old 25-05-2015, 07:01   #8
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Re: Dyneema Loops/Blocks as an Alternative to a Jib Car

Quote:
Originally Posted by Dockhead View Post
So you can adjust the sheet lead angle not just up and down, but inboard and outboard, all from the cockpit.
That sounds like what I would really like to have.
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Old 25-05-2015, 07:26   #9
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Re: Dyneema Loops/Blocks as an Alternative to a Jib Car

Just variations on a barber hauler. Of course it will work... even with, gasp, polyester. My first boat (a souped-up beach cat) was controlled entirely by this sort of rigging, including a reacher and chute. Very flexible.

My next 2 boats had tracks. I suppose they look neater to the eye, but I never found them to be "better," just easier to explain, and to some, cooler looking.

I used small blocks. Low friction rings aren't, not really.
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Old 25-05-2015, 20:18   #10
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Re: Dyneema Loops/Blocks as an Alternative to a Jib Car

Hi all,

I'm quite interested in this discussion, as I've always been a little frustrated at the lack of sail trim control with my current setup (rail + cars). However, while I totally understand the great advantage of having inboard and outboard controls, has anyone found a magical solution regarding jacklines in this situation ? It seems to me I would lose a fair amount of possibilities regarding movement aboard, and trying to think of a smart way to do all of this !
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Old 26-05-2015, 02:48   #11
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Re: Dyneema Loops/Blocks as an Alternative to a Jib Car

Quote:
Originally Posted by belle-isle View Post
Hi all,

I'm quite interested in this discussion, as I've always been a little frustrated at the lack of sail trim control with my current setup (rail + cars). However, while I totally understand the great advantage of having inboard and outboard controls, has anyone found a magical solution regarding jacklines in this situation ? It seems to me I would lose a fair amount of possibilities regarding movement aboard, and trying to think of a smart way to do all of this !
Run the jacklines under and step over the lines and unclip and reclip if the sheet is lying inboard so that the control lines are in your way. It's not really anything different from any other lines you might have running around the deck.

It's true that any rigging on the rail will create obstacles on the side decks. Also adding controls, adds complexity to the running rigging, which increases tangles, confusion, need for winches, etc., etc. This sheet lead system needs two different control lines for each side, rather than one for a towable car for a conventional track.

On my boat, it's a particularly acute issue because as a cutter, I already had rigging for two headsails. This adds rigging for a third one. If I had added two (!) more control lines on each side, it would have been spaghetti junction on the decks and total complexity meltdown. I avoided that by using the existing staysail sheet for the inboard twing system, which works really well. The outboard twing system is also good in that the control line is lead along the rails by stanchion blocks which is out of the way except where the lines cross the deck, and they do that only if the sheet is lying inboard. When in active use with the sheet lead outboard, it's not in the way.


Thread drift, but I started using my staysail together with the blade jib, something I didn't expect to ever do. It works amazingly well. The air flow over the new sail is very different, which makes the staysail work better, not to mention the main. On a reach, the staysail adds area and drive and extends the wind range of the blade even lower than it was. So I really wonder whether I wasted my money on the new yankee, which I have never even hoisted yet. It is just pure magic to watch the wind gust up to 25 knots, as it does all the time at these latitudes, and not to even think about reefing. And yet we still have reasonable speed down to 10 knots apparent and even less, especially on a reach with the staysail deployed.
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Old 26-05-2015, 02:50   #12
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Re: Dyneema Loops/Blocks as an Alternative to a Jib Car

Quote:
Originally Posted by transmitterdan View Post
I like the idea so please don't take this as a negative post.
No problem. I welcome negative comments. The whole idea of asking a question like this on the forum is to expose the potential weaknesses.

I had not considered this sort of system before Dockhead's thread and only envisaged these sort of loops/blocks for a barber hauling system, not for a primary jib sheet.

Quote:
Originally Posted by transmitterdan View Post
So is the idea to install a row of say 8 loops welded to the deck in place of the conventional jib track?
Yes that is the idea, although it could perhaps be done a bit easier and neater with a rounded solid aluminium bar with a series of holes, a little like the chainplate attachments, but longer.

Quote:
Originally Posted by transmitterdan View Post
It may be difficult to get the lead down close to the deck like a conventional jib car.
Yes, I agree the lead will be a couple of inches higher than a conventional jib car. The proposed yacht is cutter rigged so this this would not be an issue with the yankee and even the staysail is relatively high cut. It may be an issue for a deck sweeping genoa.

Quote:
Originally Posted by transmitterdan View Post
If you have multiple loops in the deck what prevents attaching a conventional block at these locations? Aside from weight what advantage is in the spectra shackles?
Yes, you could use a conventional block. The stainless steel shakle would be a bit fiddly and slow to undo and remove probably requiring a shakle key and some risk of coming undone without mousing. The stainless connection is not ideal on an aluminium boat. There is no was to easily attach the aluminium low friction loops, unless you use a Dyneema connection.

I am not sure the simple loops will have low enough friction, but if so they are very a very simple system.

Quote:
Originally Posted by transmitterdan View Post
I would want the lead to be adjustable fore and aft without crawling out there and fighting with a bar tight sheet. I like rolling hitches as much as the next person but the plain fact is that we don't optimize jib leads as often as we should because of the hassle in moving the car. How is this idea going to make it easier (and safer) to fine tune the jib lead?
Yes, if you want to adjust jib position fore and aft while under tension you need a jib car system with blocks and a line leading back to the cockpit. A pin stop jib car, or with just the proposed system the sheet lead position can only be adjusted while not under load. However, with the Dyneema solution and the addition of a barber haul system the lead can be adjusted forward and can also be moved in and out. This gives great versatility with no more bits of string than a jib car that is adjustable under load with a block and tackle system.
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Old 26-05-2015, 03:11   #13
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Re: Dyneema Loops/Blocks as an Alternative to a Jib Car

Quote:
Originally Posted by Dockhead View Post
I can confirm, after sailing 1000 miles with my new sheet leads, that they work great, much better than any cars.
Thanks Dockhead. I did not realise that you had actually implemented this system, let alone had so much experience with it.

Before I take the unusual step of having the boat designer replace the jib and staysail tracks with a series of attachment points it would be good to have some confidence that these Dyneema attachments, especially with the simple low friction loops, would be a good primary replacement. They would be used for a 49 m2 Yankee a 24 m2 staysail and possibly a 64 m2 gennaker on a 50 foot boat. The sail selection is not yet finalised and I may reconsider given your experience.
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Old 26-05-2015, 03:13   #14
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Re: Dyneema Loops/Blocks as an Alternative to a Jib Car

Quote:
Originally Posted by noelex 77 View Post
Yes, if you want to adjust jib position fore and aft while under tension you need a jib car system with blocks and a line leading back to the cockpit. A pin stop jib car, or with just the proposed system the sheet lead position can only be adjusted while not under load. However, with the Dyneema solution and the addition of a barber haul system the lead can be adjusted forward and can also be moved in and out. This gives great versatility with no more bits of string than a jib car that is adjustable under load with a block and tackle system.
For anyone who finds this confusing -- moving a car fixed at deck level forward and aft has the same effect as moving a block or eye which stands above deck level, up and down. It changes the sheet angle in the vertical plane. This has the effect of changing the balance of tension of tension between leech and foot of the sail, at least, when the clew is somewhat aligned with the track (works less and less well as the clew goes out when you're off the wind).


The other control -- sheet lead inboard and outboard -- changes the position of the clew and so the orientation of the sail to the wind -- somewhat like the mainsheet traveller. It is something I have desperately longed for for my headsails. The horrible compromise has always been to compensate for the wrong clew position by slacking or hardening the sheet so that at least part of the sail is working. For example, the sheet lead for my staysail is far too far inboard, for sailing off the wind, so the clew is hooked inboard. So forget the bottom part of the sail working at all; you just fiddle with the sheet until at least the top part works. I started barber hauling the staysail because of this. But that's just one example of a more global problem, which this new sheet lead system solves.
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Old 26-05-2015, 13:17   #15
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Re: Dyneema Loops/Blocks as an Alternative to a Jib Car

Quote:
Originally Posted by noelex 77 View Post
Thanks Dockhead. I did not realise that you had actually implemented this system, let alone had so much experience with it.

Before I take the unusual step of having the boat designer replace the jib and staysail tracks with a series of attachment points it would be good to have some confidence that these Dyneema attachments, especially with the simple low friction loops, would be a good primary replacement. They would be used for a 49 m2 Yankee a 24 m2 staysail and possibly a 64 m2 gennaker on a 50 foot boat. The sail selection is not yet finalised and I may reconsider given your experience.
Why do you need a series of attachment points? At most, you would need two, and that is only if you want to do the inboard/outboard thing.

I'm planning to do this as well. I sheet to the rail due to shrouds that go right to gunwhale, so for me, there's no inboard/outboard adjustment possible.

I plan to put a single hard point at the midships point on my rail. The twinger will lead through a block at this point and up to a low friction ring. The sheet will go through the ring and back to my regular sheet block at the aftmost position, then in to my sheet winch.

If I want to move the sheet lead forward, I would normally have to slide the sheet block along my rail. Instead, I would simply tension the twinger by a few inches. this will pull down on the sheet and have the same angular effect as moving the sheet lead forward.

If It was possible (for example with a small blade jib), I'd have two twingers like Dockhead. One would be inboard and one outboard. I'd then adjust the tension of the two of them to move the sheet lead in two dimensions instead of just one.
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