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  #31  
Old 08-31-2013
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Re: Cat 25

So does that mean more speed or just more heel
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  #32  
Old 08-31-2013
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Re: Cat 25

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Originally Posted by LakeMi View Post
So does that mean more speed or just more heel
Displacement hulls have a theoretical maximum speed. More sail power means more speed only until the boat hits its "hull speed." Once at hull speed, any additional power (from more sail area, or greater lift of the existing sail area) will just be wasted. There are a few ways a boat will waste energy - its stern could "dig in" and its bow rise, causing it to dissipate the energy through viscous friction; it could dissipate the power through turbulence around the rudder and hull; or it could dissipate by heeling over into a less efficient hull form in the water. Heeling also depowers the sail by reducing the sail area exposed to the weather by a factor of cosine of the heel angle. In other words, your boat is telling you, "if you won't depower your sails yourself, I'll do it for you."

There are several ways to depower, and you should practice all of them together. You can reduce sail area by reefing the main and partially furling the genoa (or putting on a smaller jib if you don't have furling), you can flatten the main sail with a vang and/or dropping the traveler and increasing tension of the main sheet and/or tensioning the outhaul, and you can "spill air" by letting out the boom. There are other ways to that more expert sailors can share.

In the example cited here, a blown out sail can't be sufficiently flattened (depowered) because there's too much curvature from the fabric stretching, no matter how much tension you apply to the sail.
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Last edited by TakeFive; 08-31-2013 at 10:04 PM.
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  #33  
Old 08-31-2013
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Re: Cat 25

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Originally Posted by TakeFive View Post
Displacement hulls have a theoretical maximum speed. More sail power means more speed only until the boat hits its "hull speed." Once at hull speed, any additional power (from more sail area, or greater lift of the existing sail area) will just be wasted. ...
Not exactly. Most modern sailboats, even those considered to be rather "heavy" cruisers, can exceed their hull speed under the right conditions. It is true that as a boat approached its hull speed more and more power is required to accelerate, but the relationship is not vertical. In other words, even at or beyond hull speed a larger power input (be it from you sails or from the motor) will result in an increased speed. The relationship just becomes steeper. I have had my Cal 2-27 going faster than hull speed on many occasions, and even cruisers can sometimes sail for days averaging speeds greater than hull speed.
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  #34  
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Re: Cat 25

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Originally Posted by SlowButSteady View Post
Not exactly. Most modern sailboats, even those considered to be rather "heavy" cruisers, can exceed their hull speed under the right conditions. It is true that as a boat approached its hull speed more and more power is required to accelerate, but the relationship is not vertical. In other words, even at or beyond hull speed a larger power input (be it from you sails or from the motor) will result in an increased speed. The relationship just becomes steeper. I have had my Cal 2-27 going faster than hull speed on many occasions, and even cruisers can sometimes sail for days averaging speeds greater than hull speed.
OK, let's pick nits.

I don't disagree, but my answer was targeted at the OP's level of knowledge. He was asking if a blown out sail would go faster than a new sail, and the correct answer to that question is much more "no" than "yes."

I am aware that it is possible (and fairly easy) to motor beyond hull speed, though you'll burn a lot more fuel in doing so.

It is also possible to have the sails drive you beyond hull speed, but it is generally not comfortable, especially with blown out sails.
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  #35  
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Re: Cat 25

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Originally Posted by TakeFive View Post
...
I am aware that it is possible (and fairly easy) to motor beyond hull speed, though you'll burn a lot more fuel in doing so.

It is also possible to have the sails drive you beyond hull speed, but it is generally not comfortable, especially with blown out sails.

So, don't post nonsense to the contrary. I assume that we're all adults here, and that we can all handle the truth. AND, I never consider the truth to be picking nits.
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  #36  
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Re: Cat 25

I think nonsense is a little harsh. The guy wanted to know if blown out sails would be faster than new sails, and the answer to that is basically no, and I gave some simple reasons why. This is especially true since the guy said his wife doesn't like to heel.
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  #37  
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Re: Cat 25

The blown out sails overpowering the boat mostly comes when going to weather, and it's a rare displacement boat that is going to go much above hull speed to weather anyway. I think TakeFive's comments were spot on.

Good sails also make a massive difference in pointing ability. I was really disappointing with how my Catalina 25 went to weather until I got a new main and a good condition jib.
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  #38  
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Re: Cat 25

At the risk of kicking the hornet's nest again, I'll offer one other suggestion. Feel free to disagree if you like.

If you end up with a boat with older sails, you might consider refurbishing your old sails as a lower cost alternative to new sails. It will not do miracles, but in my experience it can make a positive difference.

My old genoa was hopeless, and tore in a 32 kt squall at the end of my first season with the boat. When I inspected the fabric that tore, it was clear that the UV had degraded it pretty severely, and there was basically no fabric left on the outer edges where the sun penetrates into the furled sail. I decided to replace the genoa with a new one.

My mainsail is also fairly old (OEM sail on a 1998 boat), but generally in better shape than the jib was. I was concerned that the fabric was getting flimsy, so I thought re-resining could enhance its strength. I sent it to Sailcare for cleaning and chemical treatment (basically re-resining). I also knew that the sail had a little more draft than optimal, and the location of maximum draft was a little further aft than it would be on a newer sail. I considered this acceptable for the casual sailing that we do, and did not expect the Sailcare treatment to help with that problem. But I was pleasantly surprised that the refurbished sail was not just crisper, but did have much better shape, and I could move the point of maximum draft further forward when I needed to. I had not paid to have the sail re-cut, so I'm not sure how/why they made this improvement. I did have some bolt rope repairs done, so maybe that helped. Also, the boom now rides much higher, so maybe the sail shrunk a bit (but in a good way).

Anyway, my point is that a nice refurbish job on an older sail can yield unexpected benefits, and might therefore be worth considering if you find a Catalina 25 with an older sail that's worth refurbishing.
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Last edited by TakeFive; 09-01-2013 at 12:03 AM.
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  #39  
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Re: Cat 25

Blown out sail are just inefficient at translating wind power to forward motion, particularly when sailing close-hauled. In such a case, hull speed has little to do with it, because the sort of boat we're talking about here has a hard time getting all that close to hull speed on that point of sail unless the water is particularly flat. Usually, when sailing close-hauled, a small displacement boat is slowed by the oncoming waves so much that it can't really accelerate to hull speed before the next wave. It isn't their hull speed that slows them down so much as their lack of forward momentum relative the the waves. When a wave slows the boat the wind tends to cause excessive heel because that's the only thing it can do when the forward motion of the hull is impeded by having to climb a wave face. Good sails simply give the boat the extra power needed to keep moving.

Downwind, or better yet on a broad reach, is a very different story. In that case you can accelerate down the face of the waves in a following sea and stay above hull speed for much of the time.

The bottom line is that to say, "Once at hull speed, any additional power (from more sail area, or greater lift of the existing sail area) will just be wasted..." is just plain wrong. Even at hull speed, added power will result in added speed. Granted, not as much added speed per unit power as one can expect at velocities less than hull speed, but added speed nonetheless.
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  #40  
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Re: Cat 25

The big thing I have taken from the old vs. new sail discussion is that an older sail will not alow the boat to point as well. Plus to controle heel I will have to dump air and sacrifice speed. But as they say happy wife happy life.
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