Why reefing allows you to go faster

High gang. I am the proud owner of a new 09 AI, or will be when I take delivery on or about January 2nd. I tried it out before ordering and it was a blast, a real thrill. After bringing it in I had only two complaints. One, I could not unfurl the sail by pulling on the line, I had to grab it by the base of the mast and twist. “Sand in the mast receiver,â€

Darwinian,

"Sand in the mast receiver," is interesting. Do you know how you got so much sand in the receiver that you could not furl the sail with the furling line?

To me, it does not seem that a 10 knot wind would be sufficient to overpower the sailing rudder (I assume you have the sailing rudder), but there are others on this forum that can speak better to that. What will cause the rudder to be overpowered is if it is not locked down firmly by the up/down lines.

Keith

Keith, I had no problem furling the sail when I was ready to come in. The problem was that I could not unfurl the sail when I first went out. And it did feel a little gritty when I turned it with my hand. I have no idea how much sand was in the mast receiver because I did not look. At any rate I pulled very hard on the line, the mast bent backward but the sail would still not unfurl.

And it was not the wind that overpowered the rudder, it was the fact that with the drive in, the center of lateral resistance is too far forward of the center of the center of effort. That will cause to have to hold a weather helm regardless of the size of the rudder. And a weather helm will always cause a drag.

Interesting point on reefing.

I had been holding the fins straight down to improve lateral resistance. But I have also experienced the hard rudder action you described.

Wonder if you put fins against the hull how much that would improve things without reefing. Going to try next time out.

Those with wind anemometers maybe can do some testing of reefing versus speed under various wind speeds. To be consistent can you provide windspeed in knots and reefing in turns, maybe with quarter fractions if needed.

On other problem. Sand doesn't sound right unless you had an older model.

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I think it was an 08. I have no idea why the sail would not unfurl, that is just what the guy told me when I explained the problem to him. Pulling hard made the mast bend way back and I was afraid to pull harder in fear of breaking something. Anyway it had been sitting out in blowing sand before I took it out so I don't understand why sand in the bearings could not have been the problem. I can think of no other possible explanation.

G'Day Darwinian and welcome,
My understanding of reefing the sail is to prevent the leeward ama from burying and causing more drag.
The drive itself does create resistance even with the fins tucked up under the hull. You can easily prove this by paddling with drive in and then out. I go about 1.5km/h faster with drive out.

Sorry, my mistake on the reefing bit. I do occasionally have a very minor problem unfurling the last foot or so of the sail, but it is just a matter of binding, not sand. I simply reach up to the bottom of the sail and pull it out by hand. ("bottom of the sail" I'm sure there is some jargon for this, but not being a real sailor, I'm at a loss.)

I have my mirage drive in 95+% of the time and have not experienced serious weather helm at 10 knots wind speed unless the rudder was not locked down properly.

Now, just this past weekend, I had the opportunity to experiment with the drive-out/faster speed idea. I was travelling directly before light winds (I have no idea of the wind velocity). I was heading toward a campsite about 11 mi distant--pretty much straight-lining it. With the fins straight down, I made 1.6-1.7 mph. When I pedaled moderately, which I do much of my sailing time, I made 2.4-2.5 mph. When I removed the drive, I made 2.1-2.2 mph. This was running before the wind--NO LATERAL FORCES to speak of.

I repeated the "test" several times with the same result. The speeds are based on my GPS.

By the time I returned, the wind had switched around 270 deg and was coming in broadside. I did not do any speed experimentation, since the winds were rather gusty. I would place the winds at nominally 14-15 mph. Rather ironically, as I was pedaling, a fin mast came out. Remembering my experimentation, and that there was little drop-off in speed of pedaling vs no drive, I simply removed the drive and sailed on in. Because the winds were gusting, and because I could not run as nice a test as previously, I did not worry about a "test." However, I did note that the drop-off in speed seemed to be fairly minor (i.e., pedaling vs drive-out.) I did not think about "weather helm," because it was neither a problem before or after removing the drive.

Returning to the weather helm problem a moment. If I do not keep my hand on the steering handle making minor adjustments, the boat certainly turns into the wind. As mentioned elsewhere on this forum, it helps to slip a 1/4" line under the steering handle to help hold it in place.

Keith

Darwinian, something to check on your binding problem:

My wife's boat had a misadjusted V-brace, and the furling line drum would rub on the top of the bearing housing. The friction was enough to cause difficulty in unfurling, but not much trouble furling.

Check the top of your bearing housing for scratches created by such rubbing. It should not rub at all, so there should be no scratches on the surface.

If it is scratched up, you just need to adjust the V-brace to raise the mast up a bit and make it clear. While I was doing this to our boats, I also put some Boeshield T-9 on them to help prevent corrosion between the unlike metals.

One more tip: some SailKote lube on the ball bearings makes furling and unfurling smoother.

Tom, thanks for the advice but it was not my kayak, it was the demo at Key Sailing in Pensacola Beach. I said I thought it was an 08 but after thinking about it, it could have been a much earlier model for all I know. But I will be sure and watch for that if I have similar problems with mine.

Thanks again for the advice,

Ron Patterson

I wonder what effect, if any, the ama has on CE? Apart from causing more drag if more of the ama is in the water, would depth of the ama change the CE as well?
At times the lee ama is almost totally underwater. Does this change the CE?
Like Keith, I too am new to sailing and only heard of CE when Roadrunner gave me some advice on mods to my Oasis.

None, stringy, but it's time for a new sailing term: CLR. Center of Lateral Resistance.

In a conventional monohull sailboat, the lateral resistance required for upwind sailing is created by the hull, the keel, and the rudder. When the center of effort created by the sail(s) is near the (fore and aft) location of the center of lateral resistance, the boat is said to be balanced, and will sail straight with little rudder input, or can be steered with sails, or by varying depth/angle of a movable keel.

All of the above applies to multihulls, but then there are the amas. An ama isn't going to want to slip sideways very much when it is buried and moving forward with some speed, so it contributes to lateral resistance, at least somewhat. However, it is pulling from one side, tending to pull the bow downwind. More so as it is buried deeper.

If you made a monohull's centerboard deeper and moved it aft, that would more or less be the same as burying an ama. It would increase the lateral resistance of the overall hull form, and it would move the center of lateral resistance aft, increasing lee helm.

Tom, all this is well and good. However it does not matter if you are multihull or or monohull, if you require a significant amount of rudder variance from zero degrees, just to keep the boat on a straight course, then you are not balanced as far as center of lateral resistance verses center of effort is concerned. You can argue how much lateral resistance the amas has until the cows come home, but if you still require a significant amount of rudder just to hold you on a straight course, then you are not balanced.

If you require a hard weather helm, or lee helm, just to keep the boat straight, then you have a serious problem. And that appears to be the case with the Ai, with the drive in and the wind hard off the bow. With the drive in, you must hold a hard weather helm just to hold a straight course, and still you may slip slightly to the windward in many cases. This causes your speed to drop by at least 1.5 knots.

Hey, this is not rocket science, this is only basic sailing principles. It should be pointed out, to people on this list, exactly why removing the mirage drive gives you more speed. It has little to do with the resistance posed by the drive, it is the drag causes by having hold the rudder hard off center to overcome the imbalance caused by moving the center of lateral resistance further forward with the drive in.

Ron Patterson, Pensacola, Florida.

Ron,

I'm sure your comments are generally correct and your link to "Center of Effort" is excellent, but others on this forum have argued that the increase in speed, when you reef the sail in "heavy" winds, is due to better sail shape. It is claimed that under the stress of heavy winds, the full sail is twisted out of shape. Does that have any validity?

While your comments are well taken, you are using some subjective terms, like "hard weather helm" and "wind hard off the bow." Just how "hard" do you mean. This thread got started talking about a 10 knot wind. The weather helm seems minor to me (by "minor" I mean, it does not bother me or my thumb) until winds get above 17-18 mph, maybe higher. Also, being a bonafide sailing novice (especially when it comes to jargon), I don't know what you mean by the statement, "If you require a hard weather helm,...." Do you mean, "If you require a hard rudder action,...."

Also, it definitely does make a difference if the drive is removed. My example ("test"), which I described in an earlier post on this thead indicated that when going down wind (no weather helm?), in light winds, I made 1.6-1.7 mph. When I removed the drive, my speed went up to 2.1-2.2 mph. I repeated the "test" several times. Stringy, on his post above, also claims a speed increase when the drive is removed. In his case, he compares his speed when paddling--presumably there is minimal weather helm. Both of these examples are at relatively low speed.

Your argument regarding center of lateral resistence (clr)/weather helm/speed is interesting, but there may be some truth in all the arguments.

Where is Reconlon (aka kayaking Bob)? He and his buddies sail in serious winds all the time.

Keith

Keith, there is a very simple test by which you can figure out your problem. Is it the shape of your sail that is causing the problem or is it the fact that your center of lateral resistance is too far forward? Well, just look at the angle of your rudder.

I will bet that those who say it is the shape of the sail will find that with full sail they must hold the rudder at a sharp angle, probably at least 25 degrees or greater. Then when they reef, the center of effort is moved further forward, closer to the center of lateral resistance, and they go faster. They conclude that it was the shape of the sail. But if they check, they will find that the angle of the rudder is now much closer to zero, generating much less drag.

So just check the angle of your rudder. If you must hold it at a hard angle just to go straight then you have a problem and it is not the shape of your sail.

Ron Patterson, Pensacola, Florida.