Why reefing allows you to go faster

Ron,

It is not my problem--I don't experience a significant weather helm. I was simply commenting on my experiences and what others have said.

I would love to look at the angle of my rudder for various reasons. I've not been able to contort myself enough to do that. Have you tried to examine the angle of your rudder while sailing an AI? My situation is complicated by the fact that I usually have a cooler and a chair strapped on the back of my boat making it even tougher to see the rudder.

The other day my rudder would not control the boat and winds were low. You can be sure I was trying to look at my rudder, even asked a couple boaters about it as they passed. That problem: rudder was not locked down. Operator error.

I think it is time for me to check out of this discussion--too much wind and no movement.

Keith

Though reluctant to enter the discussion at this point, I agree with Darwinian. There is a distinction between a balanced boat and a balanced rudder -- they're essentially unrelated.

When beating to wind, the Center of Effort (CE) from the sail should be slightly forward of the Center of Lateral Resistance or Center of Lateral Plane (CLR or CLP). This is a matter of design. With the AI, the CE is a little aft of what it ideally should be due to practical constraints on mast placement and sail shape. This causes the boat to want to nose upwind to weather (weather helm) and excessive lee rudder input must be applied to counteract this imbalance. This adds drag, slowing the boat.

With Hobie's old sailing rudder you could really feel this; the newer balanced rudder, however makes this something that is no longer felt with the rudder, but can only be detected by noting the rudder position. This is akin to power steering masking understeer in an automobile.

As the sail is reefed, the CE moves forward, improving the "balance" of the boat and requiring less corrective input from the rudder. When bearing away from the wind, the issue diminishes -- by the time the boat is on a beam reach or more the CE is moved forward as the sail is let out and weather helm becomes a non issue.

The daggerboard is a stronger influence on CLP than the fins (which tend to slipstream because they are not rigid. Chekika is certainly correct that pulling them makes the boat go faster (if you're not pedaling) due to less drag, regardless of heading, but I don't think removing them sufficiently corrects the CLP. Personally, I prefer to pull the daggerboard downwind for a nice boost in speed and keep the fins in play because of their utility.

I also agree with Stringy about the buried ama slowing the boat down for reasons of added drag, but not boat balance. Additionally, Tom makes a good point about the buried ama counteracting weather helm.

IMO, everybody here has some good points. We're just not all on the same page. Boat speed under different circumstances (ie: reefing) is due to a combination of factors. If we had it all nailed we'd have the perfect sailer!

BTW, when reefed, my sail shape deteriorates as the leach opens up and the sail starts to look more like a bag. If anybody here is getting a more efficient sail shape from a reefed sail, please share the details.

I agree that the rudder is always the brake on a sailboat. No getting around it. If it can be straight, it should be.

With the balanced rudder, the AI has virtually no helm feel, so I can only tell if my boat is balanced by turning around and looking at the rudder. I can also usually guess what my boat is doing by looking over at what my wife's boat is doing.

I made this video chasing my wife in a tacking duel up the creek in very strong and gusty winds:

http://www.youtube.com/watch?v=22Wnzv8ACAk

The youtube flash converter fuzzes out the video, but in the original file it is plain that her rudder is usually very straight. She always sails with the mirage drive, and in this video was sailing with the centerboard down and bungeed to hold it forward.

I have found that just the right amount of top batten sticking out works best. If you completely roll the top batten onto the mast, you're right that the sail bags out. If you let out enough top batten that it can start to bend, it does, and again the sail bags out. What works best for me seems to be a "pencil" of top batten sticking out as an initial reef.

Roadrunner, thanks for the explanation. I disagree with you on only one point. I think the fins have more lateral resistance than you expect. True they are not rigid, but the tops of them, by design, are more rigid than the tips. This and their forward location hold the CLR considerably forward creating an imbalance as illustrated in the example given here:
http://www.myrc.org/Library/centeref.htm (Lower left in the bottom diagram.) And if you are imbalanced in this manner then you must compensate with your rudder in order to hold a straight course. It is a law of physics, it cannot possibly be otherwise.

Though I have sailed the AI only once I have sailed for years and have experienced this problem many times before. If you are sailing under jib only you will always have a weather helm, or if you are sailing under main only you will have the opposite problem. That is if the boat was designed for balance with both main and jib. (Again, as given in the example in the URL above.)

I am not criticizing the AI. No boat is perfect. Compromises must always be made. I think the advantages of the AI far, far outweigh the disadvantages. If not I would not have shelled out over $3,600, (includes sales tax), for mine. And I am very glad to be rid of my dinosaur, money pit, sloop I owned for ten years. It was costing me over four grand a year in slip rent and maintenance. It was extremely hard to get in and out of the slip, especially single handed, and I was always worried about running aground. (I did several times. ) The expense, effort and headaches required to keep and sail it was not balanced by the joy I got from sailing.

I take delivery of my AI around January 2nd and I am like a kid waiting on Christmas. I simply cannot wait. I am going sailing that day, or the next, I don't give a damn how cold it is.

Ron Patterson, Pensacola, Florida.

Thank you, Roadrunner.

This finally turned into a useful discussion.

Good luck w/ that new boat, Ron.

Keith

Thanks all for this discussion. My sailing knowledge is increasing all the time thanks to these forums!
I too find it difficult to see the rudder. I am going to mark with a texta (US sharpie??) the position of the tiller when the rudder is straight ahead, hard left and hard right (err- I mean port and starboard! )
Next time out I will experiment with the different drive configurations (up, down, out) and note the tiller position between the three marks which should give me some idea of what angle the rudder is at.

Another thing to consider is the issue of the daggerboard effectiveness, or a stalling condition. The daggerboard works best when water is flowing smoothly and quickly across it. The greater the forward movement across the board, the less the side load, and hence the less stalling. I only sail w/o the drive in, so I can't speak to that condition. But I can say that I sail regularly in heavy winds and have experience times close-hauled when the boat wants to round up and other rimes when it seems to track well. I think the difference seems to be whether the boat is really moving forward without any stalling on the board (this is something that one acquires a feel for). If I try to keep it close hauled after a tack, I have a heck of a time getting the boat moving and balanced. So, now, I over turn quite a bit (often by backing if there is any chop), starting out closer to a reach and slowly bringing it closer to the wind as the speed increases. This works quite well. Also, this prevents you from trying to start out sailing too close to the wind when the sail will be mostly stalling (even though it appears to be moving the boat). This technique goes back to Hobie 14 racing. To "pinch" the boat high into the wind, you have to keep your speed up. You dip down slightly to gain speed, then slowly bring the boat up, trying to maintain the speed. As you detect the speed dropping, you fall off just a bit to get the speed again. The inexperienced racers can't figure out how you are pointing so high and still going fast. As they try to pinch, they may be pointed higher, but they have more leeway, and thus their actual course isn't nearly as high (and they are going slower).

I will also have to agree that the boat is probably a bit out of balance in heavier winds with a full sail, but I think it isn't that much until the winds are so strong that the sail is getting overpowered (blowing out at the top) and the ama is submerging, and certainly not as much as people believe. Test this by sailing without the rudder down (which I have had to do too often). The boat sails somewhat straight up to a close reach, but not close-hauled (it's difficult to sail rudderless close to the wind since a wave can turn you enough to stall the sail which is difficult to recover from). As the wind increases, one has to rake the daggerboard a bit and furl the sail a bit to keep it balanced. This doesn't require much furling though. And with the rudder down (being so far back), the rudder will act to counter that rounding up tendency (many people don't realize that the rudder acts as another daggerboard).

When I am sailing, for the most part, I rarely have to hold the tiller. I can let go for minutes at a time. When I look at the rudder, it appears straight. But, as I said, I don't have the drive in. I also don't sail with the daggerboard straight down. I don't trust it to be all the way in and thus ready to kick up when necessary. Also, the nature of its shape means that more board is actually in the water when it is raked. Too much rake and it has a greater tendency to stall.

One thing I have always wondered is whether the boat would sail even better if the amas were asymmetric, like the old Hobie hulls. I wonder whether Hobie ever tested this (maybe it would be too expensive since they'd have to use different molds for each side). Maybe someone could invent some kind of asymmetric molded "skin" that could be adhered to the ama to change its shape.

K-bay, sweeping your daggerboard back a bit would certainly help balance the boat and sounds like a great idea. Once you select the angle, how do you secure it in position?

I have found that sweeping back the daggerboard seems to help in a lot of different conditions. I usually just put it all the way back, and it stays. I have put it about halfway, and it stayed like that too.

I have put a micro block on the downhaul for a double purchase. This has had the effect of rolling the bottom of the main in first in higher winds which takes the belly out and makes it flatter, depowering it somewhat but keeping sq ft intact.
I have marked the tiller handle angle with a sharpie and find that tiller is always almost on the mark no matter the wind speed. Like some of you I can sail for minutes as a time without touching the tiller.
I have taken to moving the CB back in higher winds as Matt suggested and it seems to stay there on its own. Once in a while coming off a wave will unlock the rudder and I will have to raise and lower it quickly to regain good control. This is usually in winds above 15 and boat speeds above 8 or 9.
Another interesting observation is that I believe the dodger adds to boat speed. While I was the only one of three using a dodger I was the fastest. The other two boats now use them and it seems to be an even race. I think the closeness of the dodger to the bottom of the sail makes it act like an end plate on the sail, decreasing drag. Like having a deck sweeper genoa on a large boat.

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Phil Summers
08 AI

Phil,

Could you post pictures of your micro-block setup?

Kayaking Bob

very interesting observation on the dodger, think I may have to try that, and I also would like to see your micro block setup

Let me get my foot out of my mouth on the micro block! What I actually did was lash a single block to the top lip of the furling drum. That allowed a much easier pull and purchase to go back up the the cleat on the sail. The problem I was having was that the downhaul went through the hole in the drum and than back up the the cleat and the sharp turn and sharp edged hole would not put much holding pressure on the cleat. By using the block I can get much more down haul and not have it come undone from the cleat.
A side benefit was that the bottom of the sail rolled in a twist or so before the top did thus taking the belly out of the sail.
The downside is that it puts a very large amount of torque and lift on the furling drum and wants to break it loose from the mast. I had that happen once already and I would not be surprised if it happened again....but I can fix it
Hope this makes sense.

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Phil Summers
08 AI

I understand the block, but don't understand the increased load to breaking point. What breaks?