Thread: Building Shesha, a Hunter Valley GIS, Australia

Will try to get out on Saturday. Darryl Eggins will be bringing along a pretty decent camera and long lens, so hopefully we can get some shots of the wings in action.

Today was a write off. No wind in the morning and then gusting 40 kts in the afternoon causing trees to be toppled, so glad I didn't venture onto the water today. We also had 30degC temps, so we're having very unseasonal weather at the moment.

Originally Posted by IanHowick

Hi Mik, from the mast back to the traveller position woodeneye (and I) use is 3.2 m. 10 degrees either side of the centreline is 55 cm either side of the centreline at this distance, which is almost exactly the distance centreline to gunwale at this point. So if 10 degrees boom angle when close hauled is correct, you get exactly that with the boom end directly over the gunwale/transom corner and there's no need to limit the traveller.

On the other hand others (callsign, I think), have felt that restricting the traveller movement either side of the centreline improves their pointing ability.

What think ye all? Am I right woodeneye that you have no restriction on traveler travel and when you're on the wind the traveller block is pretty close to the gunwale, you don't feel the need to bring the boom in closer than that?

Ian

GREAT feedback chaps!

If someone rigs that way and gets a nice shot of the boat set up on the beach with mainsheet and traveller clearly visible in the shot I will put it on the GIS rigging page with comments.

Such co-incidences certainly make a designer's life easier.

Super interested in how the vanghaul arrangement goes allied with the rope to prevent the boom moving forward! It is way nicer than the square lashing in terms of nice thinking. I will put that system on the GIS rigging page when a few have tried it in different wind strengths.

Michael

Howdy ... about the angle of the boom for different classes.

I know boats with higher apparent wind - skiffs and multihulls do bring the front sail in closer than 10 degrees. But not by much ... I've seen mention of 8. That would probably be true for hydrofoil moths too.

I think the big thing that confuses people is we get used to looking at mainsails on sloops - which we have mostly spent more time sailing than cat rigged boats.

This gives us the feeling that the boom should be near the middle of the boat.

My understanding is that it is very safe to say 10degrees off the centreline for the front sail on any rig. Each sail further back has to operate in the downwash of any sail in front so has to be progressively brought into a tighter angle.

A very fat boat that is affected by waves badly might have to move to having the sail wider than 10 degrees to keep speed up in relatively light winds. But something relatively fine lined won't have to start doing that until the wind starts whipping up a big chop.

Looking for pics of boats that seem to be going upwind from the wave direction ...





Ben Ainslie at the start


And as the wind (and sea) goes up the jib goes out a couple more degrees, but the main is flattened, feathered by sheeting it out near the 10 degree mark too.



The foot gets flattened unlike our single sail boats where the foot is kept fairly deep and the top of the sail only flattened when the waves pick up.

MIK

Is the boom staying in place regardless of the very aft traveller? From the pictures, it looks like the traveller would pull the boom aft.

I love a good Photo essay! Good one MIK.

The best advice for anyone new to a class is watch what the top guys are doing. Years of experience and development are usually the result of what they are doing to make them fast.

Occasionally, someone comes along and does something different and still goes fast. I saw this at the recent Paper Tiger International where a guy went really fast at the top of the fleet using an almost new but discarded "terrible" sail that was "slow" and basically a "failed" experiment by the original sailor. The new sail just had to be set up differently and as well, the boat had to be sailed a little differently.

In our sport, there are some basic rights and wrongs, but after that shades of grey become the benchmarks so always keep an open mind and keep trying different things. A year is a long time in any class and subtle changes happen during a season. I've been reading some old MSWBP posts lately, and the changes in thinking are quite remarkable!

Ian is correct that I have limited my traveler to approx 10 deg and it has improved my pointing ability. That being said, I would theorize that a very tight traveler that doesn't let the block lift up and out of the boat would probably do thing same thing--- for instance my loose traveller with no limit would have the traveler block at a position that would not let the boom come in to where it would be optimal, if it was tight as a drum, probably not an issue.

2 different methods, same result, I think.

Christophe, by limiting your traveler to 10 deg, what do you estimate is the final boom angle of your boat? If the boom is over the transom corner or a little more inboard than this, that is an effective sheeting angle of approx 20-22 degrees. My thoughts from sailing the Goat in a Laser fleet was that upwind performance declined if the sheeting angle was much less than this.

(10 degrees is approx the end of the transom cutout for the tiller)

Originally Posted by woodeneye

Christophe, by limiting your traveler to 10 deg, what do you estimate is the final boom angle of your boat? If the boom is over the transom corner or a little more inboard than this, that is an effective sheeting angle of approx 20-22 degrees. My thoughts from sailing the Goat in a Laser fleet was that upwind performance declined if the sheeting angle was much less than this.

(10 degrees is approx the end of the transom cutout for the tiller)

Bruce, you've got me all confused now. Can you tell me what you mean by boom angle and sheeting angle. Are these the same thing, and are you measuring them from the centreline of the boat? What do you mean by a sheeting angle of 20 - 22 degrees?

Ian

When I measure/calculate from the boat centreline, a 10 degree angle brings the boom almost exactly over the transom corner:

Attachment 220920 (Original picture Clint Chase, stolen and butchered by me)

From this picture, it would seem that you get almost exactly this 10 degree angle if you have a tight traveller just in front of the transom knees. If the traveller goes across at the frame 4 (front of rear buoyancy tank) position, it might need a bit of restriction on travel so the boom angle is 10 degrees, and you are pulling down on the leech to control the angle of the upper leech so all the leech telltails are flying.


Mik - nice pictures of all the single sail boats racing on the wind with their booms over the transom corner in all cases.

Callsign: Yes, I think with you traveller across at frame 4 position, you need a bit of restriction on its travel to get the same 10 degree boom angle.

Ian

This is what 10 degrees looks like.

Note that the angles are from the approximate downhaul position.

The corners of the transom are a good guideline... (the following is a clarification) for the 10 degrees line. It might be a bit in or a bit out depending on sail twist, water smoothness and wind strength.

MIK

I try very hard to not bring the boom in over the transom knees, I keep it right outside. Sometimes I bring it in some more depending on what I'm trying to do (pinch around a can or something/pumping) but other than that, just outside the gunwale seems to work best for me.

Bruce,

Just clarified my comment above.

MIK

OK, transom corner is fine if you measure from the mast. Sorry for the confusion, I was just concerned that by 10deg, people were thinking closer than the transom corner.

Howdy ...

It will vary by a little depending on sail camber too.

Deeper sail will have higher angle of attack at the same sheeting angle.

MIK

Yesterday's sailing was a bit of a disaster, so other than reporting that the lashing holding the hiking frame works well, I have nothing else to come out of it. Darryl E came down with the lergy, so he was unable to come along with his camera. Just as well, because I did a lot of swimming and he'd only have produced a comedic photo essay of the bottom of the GIS and it's skipper bailing it out twice!

Wind was only 10 kts but gusting bullets at 14 or so, coming from the West, directly over the mountain behind the beach where I launched. From this direction the breeze can come from all 4 points on the compass, sometimes at the same time, and from above as well. Quite often the wind indicator would just spin like a crazy thing. I should have pulled the pin before taking the boat off the trailer, but I was somewhat eager to try out the wings!

Straight after jumping into the boat a gust hit and we went screaming off on a broad reach like a banshee. It lasted 10 seconds before I was gybed by the wind off the opposite quarter, then it went still, and another big gust decended right on top of me. This time it hit from above and we went off screaming in the same direction but on the opposite tack, but very wobbly, for another 10secs! This would continue for another couple of minutes and I was already thinking "this is a very bad idea".

All of a sudden, I was by the lee, heeling the wrong way and trying to save it, but it was hopeless as the gunwale went in and it was all over. Because I was hanging onto the hiking frame, I was able to clamber up without getting wet. Oh, the hiking frame does have another excellent use. It gives you much more leverage to right the boat as you can stand on the side of the hull while hauling on the top of the frame. (Ahem, awesome, but that's not what the frame is for!) I was able to step back in still holding the hiking frame as it came back up. Mmm, another, ahem, "benefit"!

With the boat full of water it was hard to keep it upright and I went over again. This time I went for a swim in the nice cold water (13degC). After righting the boat again, and by myself I knew from past experience that the best way of re-boarding the boat is over the rear quarter, and quickly. Only now I have the frame to step over, twice, to get to the front and drop the sail.

Having bailed the boat and with just 1" of water left I raised the sail and headed for the shore. I was about 500m out and it was a beat back in those wildly swinging conditions, not nice. About 100m from shore I got smacked by a wrong'un and was over again. OK, I'll spare the details, but I was up again quickly and bailed out half the water this time. Coming into shore, I had an out of control moment with a moored Etchells that would not give way and let's say that Hakuna Matata came off second best. The Etchells has a reverse sloping transom and a nice sharp edge about 20cm above the waterline which bit a piece out of HM's bow. It'll need a piece of Hoop pine spliced in to fix it. Oh well, just another battle scar to add to the others.

So, not a very good day to assess the new hiking frame or the new vanghaul and "boom snotter". However, I can report that the frame was very helpful in righting the boat, and I have perfected the art of scrambling over the rear quarter of the GIS to re-board.

Umm, where have all these bruises on my shins come from?