Actually that's not the case. Because the track is curved at the same radius as the jib travels through the leech tension does NOT change - outside of some very minor tolerance things, it practically sees no change in sail sheeting tension throughout the full travel of the track. We hardly ever adjust the jib traveler position for racing around the cans. When adjusting for downwind, we only ease the sheet slightly to crack off for the spin run. My fingers are going numb.

You're welcome to inspect the geometry on mine this weekend while I hold your beer.

Ok, and then we'll report back to the group.

Hopefully Bill and Wouter can make it too.

Actually,

I would love to meet you and Bill also once in my life. But it is not going to be this year I'm afraid. Besides weren't you there at spring fever 2002. I did meet Jake and the other boys like W.F. and Sam Evans. So who says I'm afraid to meet my protagonists ?

Eric, good luck at Tradewinds.

Wouter

Seems alot of the same issues occur with the straight vs curved traveller tracks on the main. A cats and a few others run curved tracks while the rest of us use straights. Perhaps Bill & Wouter can fill us in on all the advantages/disadvantages of curved vs straight for the main.

Mike.

Mike,

What are you doing!?

I pass. Got to complete other work now.

Last week was fun but I'm not planning on being another week ill.

Wouter

Oh, just throwing a little gas on the flame...

That's not EVEN funny.....

How about if the jib track had a smaller radius than the sweep of the jib?
Then it would open the leech when you travelled out and close it when you travelled in.

It is very easy to rig the traveller sheet to work from both hulls.

First the use of the describtion of SWEEP of the jib. This is always smaller than the foot of the jib sail !

Secondly, this would do something you want. Open up the leech with increasing winds or when going on a LONG reach. On short reaches you just slack the jib sheet a bit and forget about that 1 or 2 seconds low of speed.

Wouter

Hi Sam,
I have experimented with that also. The drawback that I ran into is that the jib does not self tack very well because as the jib tries to come across it gets sheeted in tighter. It is like there is a hump or a hard spot in the track that the jib car has to pass over. Uncleating the jib and letting the sheet out a little solves this problem but then the jib is not self tacking.
Bill

That was the perfect troll post

What a moronic response from weezy, the dutch doofus.
I was trying to be sarcastic, like Mike, but naturally, weezy
had to give us HIS definition of the use of an english term when he can barely speak english.

And of course Bill has already tried it and found flaws, but used flawed logic.
The jib is still self tacking even though you have to release the jib a little.
Beside, the track would not have to have a constant radius.

Pity we have to read through all the bickering to find some useful info.

I have a question for the guys who have tried and experimented with these setups, based on the idea that, if I`m gonna ever put a self-tacking jib on my boat, I`d like to use the straight track for a few reasons. Some of these being lower cost, simplicity, and the fact that, if there`s anything on a boat that sticks out the way a curved track does on the Tiger and Tornado`s I`ve seen, it`s sure to kill my crewmember in a big capsize.
I never even considered all the finer points discussed on some of the posts above, just thought "bolt it on & go !"

So, I now understand (some of) the drawbacks of a straight track. From what I can gather the biggest hurdle is that as the wind pushes the jib out, the distance between the clew & the sheeting position grows, and the sheeting angle changes, so the leech closes. I`m not sure I understand why the sail wants to centre back in to the middle, surely the pressure in the sail will keep it out to the point where it is set ? I would have thought that having a stopper on the track would prevent the leech closing off, the traveller car hits the stopper, and the amount of sheet tension would then determine the leech tension. Maybe you`d need two control lines to acchieve this, but it would still function as a self-tacker, both upwind and downwind, the only downside is that you might need to move the stoppers out a bit for downwind sailing. With a spinnaker this might not even be a big issue.
Bill`s solution goes over my head, so if anyone can explain why the 4:1 purchase and batten are necessary, I`d appreciate it. The Mattia F18 & F16 don`t appear to have any of these items and are fitted with a straight track, has anyone seen this system or sailed with it ? (Attached pic.)

Steve,

I think the low down of it goes something like this :

Straight rail selftacker

-1- Easy to fit
-2- Not that much cheaper than curved track
-3- With properly jib sail design can be made just as good as a curved selftacker for ONE trim point ONLY !
-4- For all other trim points the behaviour of the straight track deteriorates relative to curved track.
-5- Design must be first time right or you have increasing difficulty to get it just right
-6- Increasing purchase btween car and clew will solve the centering problem of car when jib sheet is lead forwward to tack of jib. (mattia does not suffer from this)


Curved track

-1- Not much harder to fit
-2- Only a little more expensive than curved track; when you add all up it may be less than 10% more expensive on total amount invested. Note that getting a curved selftacking set up is not cheaper than getting two ratcheting block with cleats and beckets. We are not talking huge sums of money here.
-3- With proper alignment of track with jib the sheeting along multiple trim points can be further optimized. Especially handy when you STILL need to find the optimal angles and positions.
-4- Design must be in the ball park and the curved traveller allows you to find optimal points easily by just trying.
-5- Purchase between car and clew can be reduced or eliminated and all purchase can be had in a cascading system between jib tack and car. This works better and is saves money on blocks.


Think of a straight selftacking rail as a jib setup that is sheeted of a single point of the mainbeam. This single point may be on a adjustment rail. If you have experience with that kin of system you will know how the straight rail acts.

By moving the sheeting point outward your change the sheeting angle of the jib and thus put more pressure on the foot and less on the leech. That is the reason why old jib systems had long distances between block and clew. This minimizes the negative effects of running a block outwards (or inwards) passed its design point. With selftackers however, the distance between car and clew is very small and therefor the straight rail selftackers show serious changes in sheeting angle when moveing the car past its optimal design point.

Now the old mainbeam sheeting point system could be designed to work (very) well with regard to one sheeting point, but less with others. What sailor did was optimize this system for upwind sailing in medium conditions and forget about the negative effects on other courses and other conditions where the optimal sheeting is really somewhere else. Of course with a spi you have the spi downwind and can largely forget about the jib also you don't sail many reaches then. With respect to windconditions, this is less important negative effect. In both strong winds and light winds you want the slot to open and sheeting out will do that with respect to the leech, even when the sheeting point is fixed. Running the sheeting point out does that even more. Furthermore in heavy air control is way more important can optimal trim and in light airs strategy (finding the wind and currents) is more important than optimal trim. So this allowed for a decent compromise to work.

That is why I said of Bills straight track that is will work well enough for most sailing despite the fact that I passionately disagree with his claims that it is better than curved tracks. Curved tracks simply are better especially when looking at multiple sheeting angles. I think the choice between the two falls out between recreational sailing occasional racing and more serious racing.

This this help

Wouter

Actually, I wasn't really being sarcastic...I really DO want to hear about curved vs straight main travellers...



Mike.

On Spinnaker boats:

Get a straight traveller rail. It is less in the way and the curved rail doesn't offer any serious advantages. Mainsail is different to jib because it has a boom and so you can angle the mainsheet back a bit without stuffing up you sheeting angle that the sail experiences. With the spinnaker the boom never goes out more than a foot or so and the offset caused by a straight rail is still neglectable small and will be taken up by the angle-back of the mainsheet that just will point a little bit more straight up.

On sloop boats without spi, you can go either way. Often you sail with twist in the mainsail because of the jib or you're upwinding and centre everything.

Curved tracks are really helpful on cat rigged boats that don't have a spinnaker. Here it is almost critical in getting the right sail shape on deep downwind legs. HOWEVER there is a trick to make a straight track work more or less well enough.

This trick is used on (sorry) F16's. Mostly because no curved main tracks will ever be found on these boats as they are normally sailed with a spinnaker or doublehanded and than the curved track is seriously in the way of the skipper without offering any benefit. But some of the F16 sailor like to just pop the main and go sailing on a later afternoon or evening, just like an A-cat. In this setup they have to correct for the disadvantages of the straight rail. On F16's (and other modern (spi) boats like A-cats and F18's) the mainsheet is directly fitted to a loop that runs past the boom and straight to the clew of the mainsail. This is the cheapest, low weight AND low friction option for spi boats and works very well. When going for A-cat mode (only mainsail) they just loop the clew loop over the boom and hook the mainsheet to SECOND loop and loop that over the boom after the clew loop.

When going upwind the two loops will meet and be pulled against eachother. The force is then transmitted from loop to loop via the wall of the boom, with no bending of the boom. So it will work exactly the same the single loop option only adjusting it will take more force. When sailing deep downwind the clew loop will move forward and the mainsheet loop will move back, they need to be helped sometimes, but often move quite well on their own for same strange reason. The two loops will move apart where the clew loop will follow the curve of the sail and the mainsheet loop will follow the straight traveller when the car is ran out. By now sheeting in you have optimal sailshape and the boom will bend a little but not too much as the mainsheet tension is significantly less on the downwind legs.

Even boomed mainsails that don't use loops can use this modification. Just fit your mainsheet to a loop (webbing) or a loop in some high tension line instead on its normal saddle.

Personally I'm gooing to try to add an extra control line (with cleat) to the mainsheet loop (when I use it) to pull it backward on A-cat setup downwind legs. This way I can get maximum mast rotation as well. But again this is sub optimal to a curved track but in this particular mode of sailing but as I'm doing this in recreational sailing and club races only I don't mind much.

In real racing and serious spi sailing I much prefer the straight rail. Both from a performance point of few as a construction point of view.

Wouter

For anyone who wants to experiment with a 6.0, I have a rear crossbeam with track (it has a dent) and a split front crossbeam minus the threaded rod. Put these togather and you have an integrated track front crossbeam. Free, come get it.

You have to promise to build something within a year or buy me a case of beer

Carl,

Isn't the front crossbeam on the 6.0 double walled? Mine was - the rear beam was only single walled.

Thanks Wouter,
Unfortunately in SA we sometimes have to take what we can get, which is expensive enough. The straight Ronstan tracks & cars are stocked by boat shops as they are also used on keelboats for deck-mounted genoa traveller systems, if we want a curved track it becomes a "special" import (special means twice the price.) Some of the Hobie Tigers here are fittted with curved tracks, but one of the guys made up a few by going to an engineering firm and having them bent to the required radius, and made all the mounting fittings himself. I don`t like the look of them, or any of those I`ve seen in pics on the Tornado web-site either. The fact that they stand out on stalks means they are just another thing to break your shins on in a trip around the forestay.

Luckily for me I`m so out of cash right now that I won`t be doing any modifications to the boat in a while - I`ve bought new rudders, but can`t afford the pintles & crossbar etc to fit them to the boat ! Such are the joys of building a house, it`s like someone is holding my wallet upside-down, and won`t stop shaking it.

Cheers
Steve

Mine are single wall.

Time is running out. I am getting these things out of my yard! I am thinking about a dolly for my 14.