Leech flutter, Pointing...some observations

[Indysailor]

Hi folks,
I'm hoping to get some feedback on a couple observations I had recently with my boat.

First, I should say our headsail was repaired recently and we added telltales to it. Prior to the repair, I had always noticed a tendency for the leech to flutter quite a bit while heading upwind. What I have noticed since being able to observe the telltales is kind of interesting, mainly that the the windward telltale and the leech often seem to agree, even if the luff seems to contradict them. For instance, with the boat headed to windward (130% genoa, cars are forward btw), the luff looks nice and full, but the windward telltale and the leech are fluttering. The boat is pointing right on the masthead wind indicator tab, which is at about 60 degrees.

Previously, I have always tried to stay right on that tab, hoping to point as high as possible (and also trying to keep the boat a little flatter). Yet, when I do this, the telltales are saying I need to fall off and the leech is fluttering (keep in mind that the luff looks good, nice and rounded, no fluttering at all). So, I fall off and the boat heels to about 20 degrees and this is when things get interesting. The telltales all start streaming back, the leech stops fluttering and the boat is then able to point higher, back up to the tab, right at about 60 degrees. Originally, I thought the boat would return to the place where the telltales and the leech start fluttering again, but this did not happen; as I pointed higher, heeling at about 20 degrees, the telltales and the leech continued to stay happy. So, I started trying to reason out what was going on and I hope some of you more knowledgeable folks might offer your opinions.

To me, it seems like as the boat falls off the heeling angle changes the relationship of the headsail to the wind direction in a different way than simply pointing up or falling off when the boat is flatter. I am having trouble understanding how this third dimension, caused by the heeling, would do that, but it certainly seemed consistent. The boat falls off, the headsail becomes more efficient, the boat points a little higher. Of course, the shape of the boat at the water line and below changes as well, and the boat certainly felt like it was sailing better and whatever the reason, I'm inclined to keep doing this. I'm just curious about what may have been going on.

A couple other things to mention are that the mainsail was sheeted all the way in. I also wondered how the slot may have been causing the leech flutter, and I had experimented with moving the cars back and forth to see how it might change this. What I've found is that the cars all the way up, even to the inboard fixed leads, tends to make this sail flutter less. Downward pressure on the clew, I suppose. As far as the slot goes, letting the genoa out stops the fluttering, so I have wondered about the relationship of the main to the genoa in this scenario as well.

 

[Don Guillette]

A quick note about "pointing". Everyone seems to want to point as high as they can. The problem with that is a mate has to be careful because you can go from "pointing' to "pinching" very easily and when you "pinch" you'll stall the sails.

I need RichH and Joe from San Diego to confirm this but I think that when you're pointing as high as you can you're sailing closer to your destination but SLOWER than if you fell off a bit where you'd be sailing farther from you're destination but FASTER (slower and faster are relative terms). I don't know where I heard or read that but it claimed that 2 identically matched boats, one pointing as high as he could and the other falling off a bit, that the boat that fell off would beat the other boat to it's destination.

Richh, and Joe from San Diego -- what do you guys think?

 

[kappykaplan]

You didn't say that you were close-hauled, but 60 degrees off the wind is a close reach. I get better performance out of my genoa (proabably a 150) by rigging a barber haul to move the clue forward and outboard. This lets me get more work out of the leech and reduces the fluttering.

 

[Indysailor]

That's close hauled on an Oday 23
Either way, you are correct, I don't know how close to the wind I was, but I was close hauled. Thank you.

Don- Roger Long wrote a wonderful post about that point some time ago- same concept, though- fall off, go faster. I was actually thinking of this post when I sailed that day.

 

[Stu Jackson]

S curves & VMG

Sounds like you were doing S curves that day.

The trick is VMG. Pinching slows the boat, falling off a bit gets up speed. The additional speed you make by falling off a tad usually more than makes up for the additional distance you sail. It's really that simple.

If you have a GPS, try it one day, I think you'll be amazed.

 

[Indysailor]

Stu-thank you, I did feel at times as though I was doing S curves, but for the most part the boat felt like it hunkered down and surged forward without pinching up. There was weather helm, of course, but the tiller was pretty light. In carving an S, I assumed the pattern would be different, i.e, pinch up, fall off, pinch up, fall off, and so on.

What really had me perplexed was this- once I was heeled over to 20 degrees, the direction of the boat relative to the apparent wind (i.e., determined by looking up at the wind indicator) was the same as when I was pinching the boat up and causing the telltales and the leech to flutter. So, the boat heels when I fall off, yet in the end it appears to return to the original point of sail. Am I describing this well enough? Is this a confusion, due to apparent wind?
So, I'm wondering what was going on there to create that impression. I don't have an on board GPS, but I could use my phone sometime to see how it reads.

 

[Scott T-Bird]

When you say wind indicator tabs ... what do you mean by 60 degrees? Are you saying that the tabs are 60 degrees apart (30 degrees off centerline) or are you saying they are 60 degrees off centerline? I have a wind instrument so I'm not familiar with the tabs of an indicator. I mention it because I think there is a highlighted mark at 30 degrees off centerline on my instrument.

I think you are describing that you have to ease the boat into the best sailing performance, you can't just jump right to the correct sail trim positions from a standstill. As the speed builds, the air flow is changing as well. You can't take a plane off the runway with the same trim positions that you utilize when a plane is at altitude and cruising.

Also, somebody once posted the polars for boat speed that included heeling degrees (with peak performance at greater than 20 degrees). It indicated that heeling does impact speed (and, presumably, air flow across the sails). It kind of blew the theory that boat speed is higher when heeling is flatter than 15 degrees away, even though many claim they win races by making sure heeling never exceeds 15 degrees.

 

[Indysailor]

Scott- When I set up my windex, I used the template to set up the tabs. See the instructions here. If I read the directions correctly, the tabs are set to be 60 degrees off the centerline of the boat. Could be mistaken- my 11 year old son routinely corrects me on positioning when we are orienteering for Scouts.

As to your second point, that's exactly what I was wondering. I've assumed my boat would sail better if it were flatter, but it sure didn't seem like it. The boat was practically yelling at me, "See, that's what I'm talking about, ya lubberly grass combing bugger!"

 

[Stu Jackson]

Indy, what's happening is that as you fall off your boat speed increases. Increase in boat speed always moves the apparent wind forward. That's what's happening.

 

[Indysailor]

Stu- that makes perfect sense.
Thanks!

 

[Scott T-Bird]

Those instuctions sure look to me like you have a total angle of 60 degrees. If you are sailing with the vane aligning with the tabs, that's 30 degrees apparent wind angle. That seems pretty good to me. I'm not achieving that unless apparent wind is over 10 knots approximately. Definitely not below that.

Stu is exactly right about apparent wind moving forward and I think you are right ... your boat WANTS to be sailed at a higher degree of heel. I think it is nonsense when people say they limit heel to 15 degrees or less (when beating windward). That is just plain SLOW on my boat.

Remember, if apparent wind is at 30 degrees, you are not sailing that high ... your best might be 45 degrees. Have you noticed that in a gust, the vane veers aft? That's because the apparent wind is moving aft and you can steer upwind to move the apparent wind forward again. That's how you get a lift in a gust even if the wind isn't veering.

 

[RichH]

A good possibility for the leech flutter is incorrect /initial fore/aft fairlead car adjustment.

Normally when setting up the fairlead adjustment for the day is to go onto a tight closehauled course, and slowly tighten up the course while watching the jib luff tell tales to 'break' or flutter when doing trial 'heading up', adjusting the fairlead car fore/aft until ALL the luff tales 'break'/luff *simultaneously*.

However, when you drop down or bear off from a closehauled course (AWA @ 35-40°), .... the fairlead car 'should' go forward, usually by the same amount that the clew goes forward when you 'ease' for a more open course (your 60 degree apparent course). If you dont readjust the fairlead slightly forward when less than closehauled, the car will be too far aft and the foot of the sail will be overtrimmed .... the head of the sail will start to flog/flutter at the upper panels of the leach because of the now incorrect fairlead car position relative to the more open course; you'll also now notice that the luff telltales are no longer 'breaking' simultaneously.

This condition happen especially in well cut jibs with a flat or racing cut 'luff entry', a sail that requires fairly precise helmanship to keep the sail in its narrow range of attack angle. The luff section on a recreational or 'cruisers cut' sail will be quite 'rounded' with lots of curve to the luff section that allows inattentive helmsmanship - and why 'cruisers' dont see this flogging/fluttering when they (usually) DONT adjust the fairlead car forward when they 'ease' the jib sheets to sail more open courses than closehauled.

Rx: Set proper fairlead car angle when sailing tightly closehauled, making sure that the luff tell tales 'break' simultaneously when you slightly head up beyond closehauled .... THEN fall off to 60° AWA and then see if that fairlead car is too far aft ----slowly 'head up' when @ 60° AWA and see if those luff tell tales are breaking 'simultaneously' and if not move the fairlead car more forward until they do. A jib that is 'overtwisted' will have its topmost panels fluttering at the leeches and the lower panels will be trimmed too close to the centerline ..... and some sails are 'more forgiving' than others for exactly where that fairlead car is set. If the leech tell tales at the top of the sail are fluttering, move that fairlead care more FORWARD.

On a 'racing cut' jib, when the clew goes forward, so does the fairlead car.

 

[Don Guillette]

Here's the problem with too much heel, which I learned from Buddy Melges. The boat is powered by LIFT and it comes from 3 sources -- obviously the SAILS and the others are the KEEL and the RUDDER. Boats that are excessively heeled over where you can see 2/3 of the keel and mates hanging on the rail may look trick but they're loosing efficiency they could gain because a large part of the keel and rudder are out of the water. I can't explain lift (I leave that up to RichH and Joe from San Diego) but I know how to make it work for me. Additionally, I don't know how heeling effects the speed of all boats but I do know the Catalina 30 and the Catalina 25 and those boats sails the fastest (for me) at about 20 to 25 degrees of heel.

Many sailors like to sail with a neutral rudder. They are loosing one of the three aspect of lift. To pick up the "lift effect" they need to induce as little as 10% of rudder.

As an aside -- during the America Cup races in San Diego, which seems like 100 years ago, my wife and I were sitting in a bar on Shelter Island chatting with the NZ crew, who were the biggest guys I've ever seen in my life and plus their girl friends were great looking, and who walks in but Dennis Conner and Buddy Melges. The NZ mates, who wouldn't let us buy them a round of drinks -- they insisted we join them and drink their beer (I love the NZ and AZ people), introduced us to Conner and Melges. I was speechless sitting there among two greats icons of sailing.

Incidently, the American crew hardly said anything to anyone.

So, back to heeling, two equally matched boats sailing head to head with one heeled over about 20 degrees and the other excessivly heeled over -- the 20 degree boat will beat the other boat every time.

 

[justsomeguy]

snip-

Many sailors like to sail with a neutral rudder. They are loosing one of the three aspect of lift. To pick up the "lift effect" they need to induce as little as 10% of rudder.
snip.

??? Correct me if I'm wrong, but it would seem you're just keeping your "foot" (rudder) on the brakes.

 

[Don Guillette]

Around 10% is nothing. You're slightly off neutral. It's a bit hard to do with a wheel but the way I did it on a Catalina 30 was look down at the emergancy tiller stub. With the wheel, I was feeling for the first hint of resistence. With a tiller it's a piece of cake.

Next time you're on the water try my method and see if it works for you. If it doesn't go back to the neutral rudder. If you go to far it won't act as a brake as the boat will start to turn.

Another thing is the mainsail, which acts as a "barn door of a rudder" will react against the slight rudder deflection. Ever see this happen -- a closehauled boat is approaching a turning mark and the mainsheet/traveler trimmer doesn't adjust the traveler. The driver has a hard time turning the boat because the "mainsail barn door of a rudder" want to keep the boat going straight ahead.

 

[RichH]

JSG - The most commonly used sailboat keel shape is an aerodynamic design: NACA 64A010-xxxx which is an airfoil shape designed by NACA the predecessor of NASA.

This keel shape is normally chosen because it gives the most 'lift' (to weather) with the least amount of drag ..... and to make this keel 'lift' the rudder typically has to be held at 3° from the centerline. With rudder at 0° degrees = no 'lift'; with the rudder at much greater than 3-4°, (as you stated) the 'brakes will be ON'.

This keel 'lift' is active even with flat plate surfaces such as centerboards ... and the rudder cocked to that ~3-4° will cause the keel/centerboard, etc. to 'lift' to weather.

There are some boats that have their 'foils' (twin bilgeboards as are found on the ultra fast ILYA scows) that are already canted to about 8° (and at ~18° from the vertical) from the boats centerline .... and these boats are sailed with 0° rudder angle to make them point (like a banshee), and their normal heeled over angle is ~20-25°.

 

[Stu Jackson]

It's a bit hard to do with a wheel but the way I did it on a Catalina 30 was look down at the emergancy tiller stub. With the wheel, I was feeling for the first hint of resistence. With a tiller it's a piece of cake.

No so hard. We have that emergency tiller stub, too, but I only use it to center the wheel at the end of the day.

What I suggest is "think spoke to spoke" and use the spokes of the wheel just as you would a tiller (only in reverse of course).

Find the "sweet spot" going upwind by getting your hand off the rim and use a spoke, and find the "resistance" that Don mentioned. 5 degrees of weather helm is a good thing. The 5 degrees is NOT how many degrees your wheel has turned.

Once you balance/trim the sails for your point of sail, the boat should find a balance point. Mine sails itself for long periods.

 

[justsomeguy]

Thanks, all. I do prefer a little weather helm, but try to trim to as little rudder resistance as possible.
Perhaps the Sonoran desert will cool down enough in another couple of months to make floating my boat a bit less hellish.

 

[Don Guillette]

justsomeguy: Where do you sail your boat and do you belong to the Tucson Sailing Club or any of the clubs in Phoenix?

 

[justsomeguy]

justsomeguy: Where do you sail your boat and do you belong to the Tucson Sailing Club or any of the clubs in Phoenix?

You can call me Tom. Either Lake Pleasant or Roosevelt, depending on the season. I don't belong to any clubs.