Thread: GIS Yawl

Nothing wrong with your sheeting angle or the twist in your sail Paulie! The laced foot makes no difference to the discussion. Your sail looks to be set correctly for the wind direction.

Interesting that you have a 6:1 downhaul. Looks to me like you also had more of it on than the others, which reduced the twist. I'm surprised that you were all going the same speed. You should have blasted past them

But yes, get those telltales on asap.

It was an interesting "race". Far too many differences in important factors to expect us all to be going the same speed, yet we were.

My boat was carrying 200lbs more than IAZP (me, essentially, since my wife weighs a bit less than Christophe does). I'm guessing, based on the size of Clint's crew, that BLEAT was carrying a bit less than KM, maybe 150lbs more than IAZP.

BLEAT is obviously carrying more canvas than the other two, with the mainsail set in a different spot.

Christophe has both tremendous general sailing skill and tons of experience on the Goat. Clint is clearly a better sailor than me but it was only his 3rd day in the Goat. I've had a bit more GIS experience than Clint but my basic skills are only adequate.

Due to different GIS sailing time, Christophe has had more time to tune his rig. My rig is better than it was last year but not yet what I want. Clint had not done any tuning at all.

I'm sure there are other differences.

And yet, we were all in the pack together. At least, we were on that point of sail in that amount of wind.

I'd be interested to see how we'd all do in a larger variety of wind conditions and points of sail. I'm guessing that BLEAT could out-point the other two boats and that C & C's better basic sailing skills mean they'd crush me in a race.

I am not so sure that the yawl will outpoint the other two goats. The mizzen is working in the backwash of the main and causing some drag. It is more a riding sail intended for control and probably contributes nothing to the boats power while sailing close hauled. It will add minimally to the drive on a reach and run. It seems to me that a well tuned cat rigged boat will out point a two masted cat-ketch or cat-yawl sail rig.

Hi Dennis,

I think you are pretty right. Extra area is extra area though so even though it loses efficiency (as you say) .. some extra less efficient sail area does make a difference.

I guess the classic example of that was the overlap in Genoas. Everyone could prove that it was a silly place to put sail, but it was free area under the racing rules at the time. Now most go for bigger mains and tall and skinny jibs.

The interesting thing of course is how cruising boats and non racing production boats used the same expensive and inefficient rig.

The Mizzen also is in the the downwash of the main but in terms of the overall circulation is going to increase the circulation of the system of two sails so will increase upwash in front of the main, theoretically allowing a higher pointing angle.

However at the same time it introduces drag. So I don't know where that particular equation will work out. Because it is a bit away from the main compared to a normal jib the circulation effect will be less too.

hehe ... what a complex way of sailing ... I am not sure.

In general a single sail is more efficient for its area than a two sail rig of the same area. particularly when there is no limit on span. Look at A-class cats or Moths.

But as span becomes limited even highly developed rigs - NS14 - the sloop rig starts to make sense. That class has an 18ft (about 5.5m) above deck position for the mainsail black band and no restriction on sail distribution between main and jib (and no spinnaker)

I'm interested to know, though I think it is true that if you had an extremely restricted span (oops ... height of rig) whether suddenly the most efficient rig for the area becomes a yawl or ketch or some other divided rig. Hmmm .. maybe and example of that was the square riggers and last era of sailing cargo ships.

MIK

Originally Posted by paulie

None of us have telltales. They are on my to-do list. So is a proper shackle for my throat (I can see mine slide >1" when I apply downhaul).

Here is some additional info on the 3 rigs (going from memory -- C & C, please correct my errors):

IAZP: shackled throat; loose foot; stiffened, but solid, boom; 4:1 downhaul; Duckworks sail

BLEAT: sliding throat; loose foot; hollow box boom; 4:1 downhaul; custom sail

KM: sliding throat; laced foot; solid, bendy boom; 6:1 downhaul; slightly modified Duckworks sail

Bleat's throat is sliding currently (about to fix, somehow) but the boom is solid and bendy currently. Downhaul is only 3:1 at this time, at best. Sail is custom soon to be refined. I have roach and 3 leech battens. I do have telltales and they are helpful, though I find they fly in a wide window of sail trim.

I wish to stay with my spectra/dyneema lashings for the sail at the throat but feel a hole through the yard there is a little risky. I may simply fasten a small pad eye around the lashings so they do not slide. Thoughts?

Just get it so it doesn't move. At all. Immobilize it. NO transfer into the head. Bruce (woodeneye) had to tell me this about 8million times and for two years I didn't listen and he was right. I thought I could get it tight enough with lashings. Not going to happen. Imagine the strength in a 4:1 downhaul, and that's not even on the top end around here. Lots of force. How about eyes around the boom with a cable going through them? Steel and no holes.

Nice clarification Christophe!

MIK

In my experience of lots of sailing of BETH I couldn't really get reliable readings from the telltales. Even though the mast on one side doesn't change real performance much it does introduce roughness to the airflow. But if the sail trim is correct the flow reattaches ... much as it does at a jib luff when there is much of either a positive or negative angle of attack.



Image from Arvelgentry.com - a great resource for really understanding the flow around sails.

As you can see there is a bubble where the wind can't make the corner ... so it creates a softer radius in the first and fourth images with a separation bubble with the flow reattaching. This is not bad ... it correlates ... for the jib with a much higher absolute lift in that area when the bubble is on the leeward side.

But as you bear away further the bubble enlarges along the sail ... but when it tries connect so far back that there is no sail you have a complete sail stall.

A tuft will fly above the mast in the peak of the main ... so that is a useful place.

My practical response was to rely more on leach ribbons. Particularly ones 25% and 50% down the leach from the peak.

So steering or sheeting is from a balance between luffing and leach ribbon behaviour.

When you want power ...
Upwind the leach ribbon should flick behind the sail maybe 3 percent of the time ... very roughly.
Reaching ... maybe 10% of the time .. just flicking back and out again.
Running ... it won't fly at all of course.

The reason is because there usually is a little bit of separation at the leech on the lee side itself particularly when there is a lot of depth in the sail. This also is not bad.

MIK

Originally Posted by CCBB

Bleat's throat is sliding currently (about to fix, somehow) but the boom is solid and bendy currently. Downhaul is only 3:1 at this time, at best. Sail is custom soon to be refined. I have roach and 3 leech battens. I do have telltales and they are helpful, though I find they fly in a wide window of sail trim.

I wish to stay with my spectra/dyneema lashings for the sail at the throat but feel a hole through the yard there is a little risky. I may simply fasten a small pad eye around the lashings so they do not slide. Thoughts?

I have a system that I think works with no hole through the spar at the throat. I'll try and get a picture or two up soon. Won't be tomorrow, might be by the end of the week.
Ian

Congrats Clint! Bleat looks awesome. And to have 3 Goats sailing together must have been an absolute blast.

I don't have much to add to the sail crease discussion as I've been blessed with a sail that sets well in spite of anything I do to screw it up. It's loose footed and a stiffer boom was needed to get good luff tension and reduce twist. I use 6:1 downhaul.

Originally Posted by SimonLew

Congrats Clint! Bleat looks awesome. And to have 3 Goats sailing together must have been an absolute blast.

I don't have much to add to the sail crease discussion as I've been blessed with a sail that sets well in spite of anything I do to screw it up. It's loose footed and a stiffer boom was needed to get good luff tension and reduce twist. I use 6:1 downhaul.

Simon what weight do you use? Who was the sailmaker?

The sail is from a local sail loft, Doyle Plough in St Pete, FL. These guys build serious big boat race sails but they also do small boat sails. They got interested in the Goat when I inquired about what they could do for a high performance balanced lug sail. The result is a radial cut 5oz dacron beauty. It sets amazingly well, like it came off a mold. Everyone who has seen the sail set, including some world class sailors, are impressed with the shape. Since building the Goat sail they have built a few other small boat radials. Their radial sails for a Sea Pearl are awesome.

Hi Simon, that is a seriously nice sail. Also, your yard looks fairly stiff. What is it made from?

If I may ask, how much was your sail? I wouldn't mind putting in an order for one!

Florida is just down the road from Maine hehehe

MIK