Dyneema Loops/Blocks as an Alternative to a Jib Car

[model 10]

Do you have enough time on this system to know if the rings are wearing out the sheets?

[Dockhead]

Originally Posted by transmitterdan

Dockhead,

In this arrangement how do you route the sheet so it arrives fairly at the turning block? Are you running the sheet through the car on the jib track with it just positioned all the way aft?

Yes - the sheet goes to the normal car, which is put into the full forward position.

One small problem I had is that the sheet was chafing on an untaped cotter pin in a shroud. I will need to replace the sheets this winter as a result.

If I use the inboard twing, the sheets will be routed inside the shrouds. I am still experimenting, but so far have not felt the need for sheeting further inboard. With the new main now up, I am sailing at 28 and 29 degrees AWA with both sails still giving a lot of drive. The first sign of pinching is a bit of backwinding of the main, which I think would be worse if I sheeted further inboard. But I am now headed SW into prevailing SW winds, so will have 1500 miles of upwind sailing to experiment with .

The control line is routed to the turning block along the lifelines through stanchion blocks. This works great. I might have already mentioned it, but with triple purchase the action is so light and smooth that I can adjust it without a winch (!) in light wind.

[Dockhead]

Originally Posted by Guy

Do you have enough time on this system to know if the rings are wearing out the sheets?

1500 miles and no trace of wear from the low friction rings. The sheets go through extremely smoothly -- I don't think any worse than a block in any way.

These low friction rings are the bee's knees -- block v2.0 as far as I'm concerned, making blocks simply obsolete for most purposes. Add to the fact that they are at least 5x (if not 10x) cheaper, plus 2x or 3x stronger, more compact, no moving parts -- there's just no comparison. I'm still kicking myself I didn't discover these earlier.

[Dockhead]

Originally Posted by monte

Very neat! Nice to see a plan come together. Are you going to replace the green line with dynema and splice further back as planned? It looks like one pad eye will be sufficient for both attachments. I'd guess there's a lot of load on that point as well.

Problem is the strop has a minimum length for a good splice, which is too long.

It's not really necessary to splice the ring into an eye -- however cool that looks. That's because there's plenty of room for the sheet plus the strop in the hole of the eye. It doesn't look as elegant, but I think I'm going to just make a loop through the hole. Since Dyneema doesn't make very good knots -- slippery -- I'll probably use regular dacron.

If anyone has any suggestions for a more elegant way to do it, I'm all ears.

[Matt Johnson]

Originally Posted by Dockhead

Problem is the strop has a minimum length for a good splice, which is too long.

It's not really necessary to splice the ring into an eye -- however cool that looks. That's because there's plenty of room for the sheet plus the strop in the hole of the eye. It doesn't look as elegant, but I think I'm going to just make a loop through the hole. Since Dyneema doesn't make very good knots -- slippery -- I'll probably use regular dacron.

If anyone has any suggestions for a more elegant way to do it, I'm all ears.

Just FYI.... if looped through the hole, the SWL is a little less than half that of properly spliced to the outside of the ring. Here's a link to Ronstan showing the difference for their rings:

Ronstan Low Friction Rings | Mauri Pro Sailing


Matt

[Dockhead]

Originally Posted by funjohnson

Just FYI.... if looped through the hole, the SWL is a little less than half that of properly spliced to the outside of the ring. Here's a link to Ronstan showing the difference for their rings:

Ronstan Low Friction Rings | Mauri Pro Sailing


Matt

Thanks -- that's very useful information.

I think still several times stronger than needed for my application, however.

[transmitterdan]

Originally Posted by Dockhead

Yes - the sheet goes to the normal car, which is put into the full forward position.

I'm dense and thus don't understand. If the normal car is all the way forward then the twing has to be forward of that and cannot move the sheeting point aft. I would have guessed the car would be fully aft and the twing ring near the front of the track and so pulling the ring down would move the sheeting point forward. Releasing the twing would put the sheeting point aft again.

I am interested in this idea as a way to easily adjust sheeting angle (fore, aft, vertical and horizontal) without moving the sliding car.

[Dockhead]

Originally Posted by transmitterdan

I'm dense and thus don't understand. If the normal car is all the way forward then the twing has to be forward of that and cannot move the sheeting point aft. I would have guessed the car would be fully aft and the twing ring near the front of the track and so pulling the ring down would move the sheeting point forward. Releasing the twing would put the sheeting point aft again.

I am interested in this idea as a way to easily adjust sheeting angle (fore, aft, vertical and horizontal) without moving the sliding car.

No,you're right about the principles. The twing is forward of the forward end of the track. The necessity of it arose with the acquisition of a new blade jib with much shorter foot than the standard 120% yankee.

Sent from my SGP521 using Cruisers Sailing Forum mobile app

[foxy]

Originally Posted by Dockhead

Here are the snaps of my outboard twings:

Attachment 102772

Attachment 102773


This is v2.0.

V1.0 had a ring holding both jib sheets and shackled to my staysail sheet to use as the inboard twing.

I found out from experience that the inboard twing is not needed except hard on the wind, so simplified the rig like this. The other advantage is that I can now use the staysail together with the blade. When I need to twing inboard, I go forward, disconnect the shackle from the staysail and reattach it to the ring. Using one of Seaworthy Lass' special soft shackles, this is a cinch.

Really interested in this as just removed my genoa tracks (mounted with woodscrews into the sheer plank) could i do away with a track completely? for me it would get around the issues of resecuring the genoa track.
Cant quite work it out though, any photos or diagrams much appreciated.

Pat

[Stumble]

Foxy,

Yes you can use this to eliminate the jib track. The one issue is if you change the size of the jib you may have to add more eye bolts though to work with the new foot leingth.

[seandepagnier]

Originally Posted by poiu

That's a neat arrangement. I have a regular track and the forces are pretty huge on the sheave. Two people can't push the sheet down a tiny bit even to unload it (hundreds of kg load). Did you work out the load? If so, how? Are the pad eyes bolted through?

Even when the boat is heeled 30 degrees on a genoa in 20 knots of wind I can just stand on the jib sheet and it's slack enough to easily adjust the track.... but i still hate the track because it is sharp to step on.

Normally you don't need to adjust the angle under load unless you made a mistake, so this system described allows for this, but is it really useful?

I don't like the idea of having extra stuff to flog around, but so long as it's lightweight plastic maybe it doesn't matter... but even just a jib sheet alone can hurt you.

For some sails my track is not going far enough forward, so I use a carbiner to connect the jib sheet to a ubolt farther forward. I can see a problem with the dyneema system without tracks if you have widely varying jibs as it would be several attachment points and everything would have to move around, compared to just having a long track.

I sure do like the idea of tweaking it inboard and outboard. I think some racing boats have parallel tracks for this with some sort of arrangement?

Originally Posted by Dockhead

Problem is the strop has a minimum length for a good splice, which is too long.

It's not really necessary to splice the ring into an eye -- however cool that looks. That's because there's plenty of room for the sheet plus the strop in the hole of the eye. It doesn't look as elegant, but I think I'm going to just make a loop through the hole. Since Dyneema doesn't make very good knots -- slippery -- I'll probably use regular dacron.

If anyone has any suggestions for a more elegant way to do it, I'm all ears.

Elegant.. maybe not, but I do tie knots in dyneema all the time. Just don't use a bowline or square knot. There are double bowline variations and surgeon's knots, but to tie a loop with reasonable breaking strength, use a figure 8. Maybe in theory it can slip out, but typically it won't until you start to approach high loads. You can add another full turn (overhand is half, figure 8 is full) so 2 full turns will give a knot that doesn't slip out and is stronger, but uses more line and is bulkier. If you need ultimate strength, use a splice, but it is probably not required here.

[UNCIVILIZED]

Following

[DateKnight]

I use low friction rings rather than jib tracks as my shrouds are on the rail, so a track was not very feasible. Plus I hated moving forwards to relocate the snap shackle w/ block every time the winds shifted. Use two rings with a double loop for 4:1 purchase.

https://imgur.com/uOj3CXi

Control line (dyneema) passes forwards to a block on the deck under the shrouds, and then runs along the toe rail. A floating block is shackled to the toerail by the cockpit to give me another 2:1 purchase. At the floating block I switch from dyneema to poly (less slippery, can easily knot it, grasp it, etc.)

https://imgur.com/Yk6yS9M

I want to place a permanent jam cleat attachment near the cockpit. I keep delaying as I am unsure of the best place to put it: side of coaming (probably not), top of coaming behind the winch, deck at front edge of coaming, other? For those who have tried different placements of rope clutch/jam cleat for control lines, what worked best for you?



Thank you.

[jroberts]

Can you adjust the sheet angle with only one low friction ring/shackle setup if you use a furler and want to furl the jib/genoa in heavy winds? Or do you need multiple attachment points for the shackles and have to move them? That would defeat the purpose of removing the jib car track (which I would love to do) would it not?

Anyone have any pics/diagrams of an inboard & outboard set up?

[fxykty]

Originally Posted by jroberts

Can you adjust the sheet angle with only one low friction ring/shackle setup if you use a furler and want to furl the jib/genoa in heavy winds? Or do you need multiple attachment points for the shackles and have to move them? That would defeat the purpose of removing the jib car track (which I would love to do) would it not?

Anyone have any pics/diagrams of an inboard & outboard set up?

I’m not sure why the sheet lead needs to be changed when a sail is partially furled. The clew position of our self tacking jib is such that as the sail is furled the sheet angle remains the same. Isn’t that usual with furling sails?

Regarding the LFR setup, you have three controlling lines: one to pull towards the centreline, one to pull out towards the rail, and one to control height. The height control is the one that determines sheet angle. You only need one such setup per side to replace lengthwise jib tracks. You would position the LFR setup near the forward end of the track, so that the lowest position of the LFR corresponds with the furthest forward car position. As you raise the LFR that has the same effect as moving the car aft.