Tiller turbulence downwind light air

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pirouette

Member
When sailing downwind in light air, I am more or less wrapped around the leeward side of the raised centerboard with my leeward knee and leg folded under me on the deck and my windward leg in the cockpit with the boom at least at 90 degrees to windward (sailing by the lee) and the boat heeled to leeward like everyone around me. This year I have been using a carbon fiber tiller and homemade aluminum tubing tiller extension wrapped with hockey stick tape for the grip.

With the carbon fiber tiller I have noticed a lot more "feedback" and on this point of sail, there's a very slight turbulence felt through the tiller extension. This seems like it's got to slow things down since turbulence is a bad thing and I am sure everyone is going to say "sail differently stupid" but moving the tiller not only changes the direction that the boat is heading (duh..) but also increases the turbulence felt. To flatten the boat would seem to get the majority of the sail area closer to the water's surface where I assume there is less air velocity because of laminar flow, plus no one else is sailing their boat flat either

SO... is this turbulence that I am feeling normal? Any suggestions?
 
I'm not sure if I'm right on this one, if not please correct me: usually, when rudders vibrate, at least in keelboats, it's because it is not aligned with the keel (or daggerboard), maybe yours is bent or something. On the other hand, that turbulence is very normal in fast catamarans, so maybe there's nothing wrong...
 
Or the rudder may have some shape issues. Perhaps you can borrow and try a different rudder
 
Try heeling to windward first of all. This will raise the center of effort of the sail above the boat. This will help to make the boat more balanced. If you let your sail out just slightly past 90degrees then gravity will pull it forward and keep it from comming back in.

Also, in very light air you should try to hold the tiller extension down to the deck, both upwind and downwind. This keeps the blade from moving and slowing you down. You should be able to do most steering with your weight.
 
bobbyh said:
Try heeling to windward first of all. This will raise the center of effort of the sail above the boat. This will help to make the boat more balanced. If you let your sail out just slightly past 90degrees then gravity will pull it forward and keep it from comming back in.
Also, in very light air you should try to hold the tiller extension down to the deck, both upwind and downwind. This keeps the blade from moving and slowing you down. You should be able to do most steering with your weight.
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SK>> So to make sure that I understand you correctly, I would no longer sail by the lee? thus when I heel the boat to windward, the boom is now on the leeward side "up high and forward past 90 degrees" and I assume that I still want my weight as far forward in the cockpit as possible to get the transom out of the water without putting myself in the water :) ?

SK>> by keeping the tiller extension down to the deck I won't be moving it inadvertently and by shifting my weight slowly to one position or another I'll see how the boat steers merely by the attitude of the hull in the water as affected by my position on the boat?

Does it sound as though I have understood you correctly?
 
Check to see if your rudder and centreboard are in perfect alignment. Put them in, tip the boat upside down and sight down the centre line. It may be you just need to tighten the rugger gudgeons or re-align the rudder stocks.
 
pirouette said:
SK>> So to make sure that I understand you correctly, I would no longer sail by the lee? thus when I heel the boat to windward, the boom is now on the leeward side "up high and forward past 90 degrees" and I assume that I still want my weight as far forward in the cockpit as possible to get the transom out of the water without putting myself in the water :) ?

SK>> by keeping the tiller extension down to the deck I won't be moving it inadvertently and by shifting my weight slowly to one position or another I'll see how the boat steers merely by the attitude of the hull in the water as affected by my position on the boat?

Does it sound as though I have understood you correctly?
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Do you know what sailing by the lee is? All that means is that the air flow is going from leech to luff. It has nothing to do with heel angle or which direction you are heeling. It is much faster in small boats like lasers to sail heeled to windward downwind when sailing by the lee. The boat is more balanced, easier to steer, and there is less pull on the helm.

Yes, you should still be far forward in the boat. I usually have my forward leg on the deck about half way up the center board with my back leg around the hiking strap to help keep me locked in to the boat.

Also, don't let the boom too far past 90. Only let it go an inch or two past, just enough so that it doesnt fall back onto you when you heel the boat to windward.
 
Thanks for the clarification of the term sailing by the lee. I'll try out your suggestions to see how I can eliminate the turbulence I have been feeling.

Other replies raised the issues of rudder shape and trying a different rudder. The rudder appears to be in excellent condition ( i had it Awl Gripped so the finish is superb) but I can check it against a straight edge to see if it looks OK.

It's a 1976 boat and I replaced the old S/S gudgeons with the newer blue plastic ones but used the old screws holes so I don't think it's misaligned with the dagger board, plus when going downwind in light air, the dagger board has minimal amount in the water (I haven't actually measured how much is still below the hull)
 
pirouette said:
Thanks for the clarification of the term sailing by the lee. I'll try out your suggestions to see how I can eliminate the turbulence I have been feeling.

Other replies raised the issues of rudder shape and trying a different rudder. The rudder appears to be in excellent condition ( i had it Awl Gripped so the finish is superb) but I can check it against a straight edge to see if it looks OK.

It's a 1976 boat and I replaced the old S/S gudgeons with the newer blue plastic ones but used the old screws holes so I don't think it's misaligned with the dagger board, plus when going downwind in light air, the dagger board has minimal amount in the water (I haven't actually measured how much is still below the hull)
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Awl-Gripping the rudder won't necessarily fix it, it might just be that someone went crazy with a sander [assuming its wooden] or just came out of the mold as an imperfect shape. That humming that fast catamarans are famous for when they really get going? the humming is because almost all the stock rudders came out of the mold in bad shape. If your boards aren't exactly symmetrical, then they will hum, and create turbulence if it's bad enough, because the hydrodynamic forces are acting differently on each side and thus creating the turbulence and vibrations. It's for the same reason that you can steer with the hull, because you're changing the symetry of the surfaces in the water.
 
bobbyh said:
Do you know what sailing by the lee is? [...]It is much faster in small boats like lasers to sail heeled to windward downwind when sailing by the lee. The boat is more balanced, easier to steer, and there is less pull on the helm.
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I think you guys are in agreement but you are talking past each other because of the confusion that arises around "windward" and "leeward" when you're by-the-lee. By normal common sense, "windward" means the side the wind is coming from. By the racing rules, "windward" means the side away from the boom. So, when you're sailing by the lee, the wind is coming at you from the "leeward" side of your boat. How 'bout them apples?

Heel the boat away from the side the boom is on, whichever you call it.
 
Ok dumb question, but when you Heel the boat away from the side the boom is on is that side higher in the water or lower? so your going downwind the boom in on your port side your starboard side should be higher in the water? :)
 
Murphs said:
no, the boom should be pointing in the air
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Right. There are a number of reasons for doing this, but one of the easiest to see is to look at a boat from behind while it is sailing dead downwind with the boom way out. With the boat flat, the center of effort of the sail is way off to one side -- force of wind on the sail is going to constantly want to turn the boat, so you're constantly correcting with the rudder, which is slow. When you do as Murphs says, you are putting the center of the sail over the center of the boat, bringing things back into balance.

Also, the wind is blowing harder 8 feet off the water than it is 3 feet off the water, and you're sticking more of your sail up into that faster wind.
 
Thanks for the replies which seems to bring others into the discussion. Chris123's most recent posting clarifies to me the purpose and accuracy of how I am sailing and I guess I am sailing more downwind than by the lee. As earlier stated I am forward in the boat to raise the transom out to result in less wetted surface, AND it is how the boats ahead of me are sailing. These are very light air conditions. As the wind speed picks up, if not careful to adjust I go VERY slow because a good gust flips the boat....

Nonetheless I am still getting turbulence and when I ask other sailors in the group, they aren't. I checked both of my blades with a straight edge and by eyeballing them and they seem perfect. As I wrote earlier I used the old gudgeon holes.

btw, even though this is a '76 boat, I do have newer blades that were reconditioned by Gybetech in Middletown RI and last year I had them awlgriped.

Rocksteady suggested checking the blade alignment by turning the boat upside down to determine if it is an alignment issue. I have access to an automotive lift and can raise the boat with the blades hanging but I really can't tell because there is so much slop of the centerboard in the trunk that I can easily deflect the centerboard to one side or another.

I have gone over to other boats at regattas and by sticking my hand into the top and bottom sides of the C/B trunk they all "seem" to be about the same size, and in checking the thickness of my CB it was within specs (31.5mm as I recall). I had measured that because I also have issues in chop and stronge winds with water coming up through the center board trunk when sailing upwind (see an older thread from about 2 years ago)

Given other issues with my poor sailing performance, this turbulence question may be spending more time than it's worth but I do appreciate the time and effort you have all spent trying to help me.
 
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