Thread: GIS sail tweaking

Back once more the the original question. This past weekend we had very light winds when I wanted to go sailing. So I tried MIK's suggestion of restricting the amount the traveler could move. My method was simple: I tied a piece of cheap line around the shackle on the traveler block and then ran each end to an inwale, tying them so that the block could only move about one foot either way. Quick and easy.

Did it work? I'm not sure. I had a lot of trouble pointing up on port tack (sail on windward side of the mast, for my rig), more than I thought I should be having. But the current was running pretty strong -- maybe 1.5 to 2 knots -- and that may have been the problem. Winds were REALLY light for most of the time. My speed over land may have been nil in spots.

But it was easy enough to set up and didn't seem to harm anything. So I'm willing to give it another shot when the current is running differently. I'm interested in hearing if anyone else tries it and if it helps.

I have put together this video of Mik and I sailing during the Texas 200. It shows the variety of wind and wave conditions we sailed in one day. It shows when we reefed, which reef we used and body positions. We were real lucky in being able to combine video and still snap shots to illustrate the sailing because of some of the other boats we were sailing with. If you plan to go adventuring in open water, be safe, reef early and often. Mik and I got real good at reefing.

[ame=http://www.youtube.com/watch?v=II0TisotCGs&feature=channel_video_title]GIR at speed v1.wmv - YouTube[/ame]

Enjoy!

Thanks! That is incredibly helpful, especially the info about body positions. It also convinces me I need another set of reef points. Thanks for putting that together.

Note the location of the #3 reef points. I lowered mine 12" from their original location to get a little more sail area and prevent the boom and yard tips from touching. With this set up the sail has a luff length of 16" from the #3 reef grommet to the yard grommet.

I have found that the #3 reef has a lower wind speed range for sailing to windward. In winds ranging from 5-15 mph the boat can sail 90-80 degrees to the wind. Once over 15mph the angle of attack improves to about 60 degrees, while around 20mph it's about the same as the full sail in the mid range wind speeds. When over 20mph it's just a fun wild ride no matter which direction you sail. I have even gybed with #3 reef in 25mph winds/flat water with no trouble.

Just wading in here rather late as I haven’t been a regular visitor of late. There are a few things to consider if you want to improve the pointing ability of a balanced lug sail. The two most important things to look at are the luff and the leach. MIK has kept the basic setup pretty simple and it works well for all kinds of cruising sailing and it gives surprising performance, but this is largely due to a very generous sail area and a light hull with a relatively low wetted area.
If people really want to up the ante on performance upwind in a fresh breeze as Warmbeer was after, there are a number of tweaks. These have been well documented, but to summarise a few, these are:
· A tight luff
· A tight leach
· An immoveable throat fixing and good control over the throat-peak tension
· Well adjusted helm
· Boat trim (centred crew weight, or even further forward, and sailed as flat as possible)
· Speed to keep the foils working to provide maximum lift
For a tight luff, you really do need considerable tension on that downhaul, so consider a minimum of 6:1. More would be better, because the downhaul is doing the job of the kicker as well. You will need a loose tether to the mast to keep the boom against the mast when the boom is on the lee side of the mast.
It is impossible to get enough tension on the leach from the basic downhaul, as the position next to the mast is simply too far forward along the boom. If you are really chasing upwind performance, then I’m afraid you will need a kicker or vang as we call it is Oz in order to flatten the head and tighten the leach. This will also need to be something fairly hefty, like 6:1 as a minimum, but preferable up to 15:1. It’s a big sail we are tweaking. This does mean a really stiff boom is required, as moving this sort of power along the boom is going to bend it severely, or break it like I did. I won’t go into the pros and cons of loose footed vs lashed, but in my mind, it’s chalk and cheese. Loose footed is the way to go for ultimate control of the foot. Pulling on the outhaul also opens the leach more when you need it.
It’s possible to get the GIS sail set like a blade for excellent upwind performance. You won’t be tacking through 80degrees, but you can definitely achieve less than 90 degrees with the right setup.
There is not much difference in performance or height between either tack. In fact it’s hardly noticeable. If your tell tales are too close to the mast you will get false readings from them due to the turbulence from the mast. For upwind, you will need some telltales ahead of the mast. Another set about 600mm behind the mast and about 400mm up from the boom should be enough. Two leach telltales are also beneficial if you run by the lee. For maximum performance of height vs speed, you need to keep the windward telltale flicking about half the time. The leeward telltale should not be stalled unless you are driving hard over or into a big wave.
I found pointing ability also improved by moving the traveller back to the transom. The sheeting angle is therefore tighter and closer to the centreline than the “normal” position. The traveller line needs to be low stretch dyneema or spectra line (abt 4mm), bar tight and left that way. If it is loose, the boom will be too close to the centreline and speed will suffer.
If you have a vang/kicker, and sailing in 15kts or above, it needs to be tight enough that the boom does not rise when you sheet out in a gust. If the boom rises when you sheet out, the sail gets fuller and powers up. Not what you want.
If you reef at all, which I don’t, upwind performance goes down the toilet and none of this is really relevant. However, by getting control of your sail with these tweaks, you can depower more efficiently and sail in a stronger wind before having to reef.
Do these basic things and you’re flying upwind

Now THAT is news we can use. Thanks!

Two questions:

1) Why is it so necessary to fix the throat?

2) Can you show us a pic of your vang setup?

Originally Posted by paulie

Now THAT is news we can use. Thanks!

Two questions:

1) Why is it so necessary to fix the throat?

2) Can you show us a pic of your vang setup?

1. Actually, it was Keyhavenpotter who was the first to mention this, I think while I was still building. I didn't do this at first, but then read some of his tweaks and tried it. It's easily one of the best tweaks you can make to the lug rig. What it does is stop the tension from the downhaul dead at the throat, otherwise some of that tension gets transmitted along the throat through to the peak, nullifying any attempts at adjusting the sail along the yard. With the throat fixed, you can adjust the yard tension accurately by installing a cleat at the peak.

2. Having looked for the pics, I realise that I don't have any pics of the latest set-up. Here are some pics of what I started with.

https://www.woodworkforums.com/f169/b...ml#post1232655

Even so, my current setup needs some tweaking so that I can put some of my learnings of the past year into improvements.

Currently, the downhaul attachment isn't as far forward as shown in these pics. This setup shown in the linked post is a bit extreme, but it works well to move the boom backwards and forwards. I can haul the boom back for upwind and haul it forward for reaching and even further forward for downwind. Having it forward for downwind is more stable in strong winds as the rig is centered more and the boom not so high in the air.

The traveler is shown very loose, but this is wrong. It must be very tight.

The boom is also my old one which was not up to the task as it was too bendy. It broke. The new one is also hollow but much stiffer.

I've also realised how poor my knot tying skills were back when those pics were taken. I can actually tie a very good bowline these days. How I got by without being able to tie a bowline is beyond me!

We're taking the GIS out onto Salamander Bay over Christmas/New Year, so the Laser will be getting a chance to dry off. It will be a good opportunity to get a few more improvements sorted out and to get some updated pics posted.

The pics are awesome. Thanks! Just what I wanted.

And it's the final nail. I've been wavering on actually building a stiffer boom this winter. I had planned on doing it but the calendar is conspiring against me. And so my resolve had been softening. Seeing your pics has given me another push. I'll just have to carve out the time somehow.

Did you move the downhaul around to the front of the mast? Did it make a big difference? I'm not happy about drilling more holes in my boat, but I'll move the downhaul if it really helps.

Interesting how much difference moving the boom makes in where the sheet comes down. As you may have read earlier in this thread, I am planning on moving the traveler aft, as you did (mostly to get it to stop interfering with the tiller, which bugs me), and I'm also struggling with the placement of the last block. I can see that, with a vang setup like you have, I'm definitely going to have to keep that block above the top of the middle seat or the sheet will just grind off the seat's edge.

Finally -- and I'm not trying to be a PITA here, I'm just a little slow -- I'm still not sure I understand why it is so important to fix the throat. I mean, I understand the theory. It prevents the throat from sliding down the yard. But I kind of thought that was a benefit. Tightening the luff, via the downhaul, also tightens the head from peak to throat. You don't have to wrench the sail tight along the yard before hoisting it -- tightening the downhaul takes care of it later.

I guess the key question is this: When, in practice, do you want to loosen the luff without loosening the head? Or, conversely, when do you want to be able to tighten the luff without tightening the head? Is this something that matters more in theory than in practice, or are there points of sail where it makes a noticeable difference?

Okay, one more question.

(They say that no good deed goes unpunished. I guess that goes for posting helpful information in forums as well. Show that you know what you are talking about and you'll never scrape off the buffoons who seek to suck that knowledge out of you. Feel free to tell me to buzz off when you are tired of answering questions.)

I am also struggling with getting my weight far enough forward when sailing alone. By the time I'm far enough forward, the tiller extension is at an unhelpful angle. I could put on a longer extension, but the one I have already gets hung up on things.

What would you think of a Coquina-type rope steering mechanism which would allow steering from anywhere in the boat? Crazy idea? It might not be "twitchy" enough for a boat as light as the Goat. But it would allow me to sit much further forward.

As you know, I speak only from vicarious experience, observation, and osmosis here, but...

Originally Posted by paulie

I'm still not sure I understand why it is so important to fix the throat. I mean, I understand the theory. It prevents the throat from sliding down the yard. But I kind of thought that was a benefit. Tightening the luff, via the downhaul, also tightens the head from peak to throat. You don't have to wrench the sail tight along the yard before hoisting it -- tightening the downhaul takes care of it later.

I think the point that's most relevant is that the head + luff length (and to some extent the change of direction at the throat) will conspire against your ability to increase downhaul tension. The tension that suits the lug best (as described by MIK, but also by Todd Bradshaw on WBF) is "brutal." You won't get there until the yard is straight vertical and the peak lash and downhaul anchor are opposing each other. When you isolate the tension at the throat, you make it possible to get the tension you need.

I guess the key question is this: When, in practice, do you want to loosen the luff without loosening the head? Or, conversely, when do you want to be able to tighten the luff without tightening the head? Is this something that matters more in theory than in practice, or are there points of sail where it makes a noticeable difference?

I think the first question's answer is probably: never. The second question--tight luff/looser head--is the standard, no? Remember, part of the yard's flex is to modulate the head's shape under different conditions as a function of downhaul tension. In moderate winds, one applies less-than-brutal downhaul and therefore less yard flex. The straighter yard allows the curvature in the sail's head to fill out as draft. Stronger winds call for de-powering up high by cranking on the downhaul which bends the yard, eats up the excess cloth, and makes a flatter sail. So the head tension should probably be set at some level that enables that behavior and then it should remain static.

I think. At least that's what makes the most sense to me. Sorry that this is still a theoretical discussion.

Originally Posted by woodeneye

I realise that I don't have any pics of the latest set-up.

Well that's no excuse! Grab a camera and get us up to date!

Originally Posted by paulie

Okay, one more question.

I am also struggling with getting my weight far enough forward when sailing alone. By the time I'm far enough forward, the tiller extension is at an unhelpful angle. I could put on a longer extension, but the one I have already gets hung up on things.

What would you think of a Coquina-type rope steering mechanism which would allow steering from anywhere in the boat? Crazy idea? It might not be "twitchy" enough for a boat as light as the Goat. But it would allow me to sit much further forward.

You just need a long tiller extension. It needs to reach to the front of the CB case. You'll soon get used to it.

Rope steering mechanisms are for Coquinas, not proper sailing boats like the GIS. Bite your tongue, how can you rope steer from a hiking position with the middle of your thighs on the rail, the mainsheet cleated and one arm extended to get more weight outboard?

Just joking, you don't need a cleat for the mainsheet.

Originally Posted by paulie

Did you move the downhaul around to the front of the mast? Did it make a big difference? I'm not happy about drilling more holes in my boat, but I'll move the downhaul if it really helps.

No Paulie, I left it where it is. It's fine, just creaks a lot. You have to take off some vang when gybing onto starboard that's all. In any case, you don't have much vang on when running. Just enough to stop the boom rising and if the wind is strong, stop the yard from going too far forward.

Originally Posted by paulie

I'm still not sure I understand why it is so important to fix the throat. I mean, I understand the theory. It prevents the throat from sliding down the yard. But I kind of thought that was a benefit. Tightening the luff, via the downhaul, also tightens the head from peak to throat. You don't have to wrench the sail tight along the yard before hoisting it -- tightening the downhaul takes care of it later.

I guess the key question is this: When, in practice, do you want to loosen the luff without loosening the head? Or, conversely, when do you want to be able to tighten the luff without tightening the head? Is this something that matters more in theory than in practice, or are there points of sail where it makes a noticeable difference?

You need to be able to adjust the tension along the yard to have the sail right for the conditions. I'm not sure if you read about my dramas with the yard, but I eventually went with a very stiff aluminium yard. I'd really like a stiff carbon one as it would be much lighter than the alu, but the alu works well enough. My sailmaker made the sail for a stiff yard as this gives ultimate control over the fullness up top. With the bendy yard, my sail was horrible and it flattened too early and I lost power in light to medium winds. I guess every sailmaker makes them slightly differently, but in practice, for a light wind, I set about 6cm of slack along the yard when the sail is down. A little less for medium wind and tight when the white horses appear. At 20kts, I stretch the sail along the yard as tight as I can using a purchase for leverage. The yard will be bending quite a lot in that wind so the sail will be board flat at that point. My sail has some broad seaming so the effect of tightening the throat-peak is similar to a Cunningham. It pulls the fullness forward and opens the leach.

The thing is also that in a medium wind you have quite a bit of vang on, so if you didn't have that tight fixing at the throat, the tension along the yard would be much more than I'd want and the sail would be too flat and lack power.

Originally Posted by woodeneye

Rope steering mechanisms are for Coquinas, not proper sailing boats like the GIS. Bite your tongue, how can you rope steer from a hiking position with the middle of your thighs on the rail, the mainsheet cleated and one arm extended to get more weight outboard?

Okay, I'll drop the idea!