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Old 29-12-2013, 15:35   #91
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Re: Legitimate Bluewater Question

Related to what I think is the OP's question: how not to end up like boat B . . .

#1 Sailing in heavy weather - should be a whole thread of its own . . there have been many in the past
#2 Engine maintenance and system design - should be a whole thread of its own . . . there have been some isolated ones but I don't remember a comprehensive thread . . . re system design, I personally really like day tanks (gravity fed absolutely clean fuel is hard to beat)
#3 Navigation and approaches in difficult conditions - should be a whole thread of its own . . . I don't remember very many in the past
#4 Preparing the boat for offshore and heavy weather - should be a thread of its own . . . there have been many in the past . . . but it depends where you sail and what compromises you are willing to make. A "Puerto Williams" boat looks totally different than a "Caribbean or Med" boat and is prepped totally differently
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Old 29-12-2013, 16:57   #92
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Re: Legitimate Bluewater Question

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Originally Posted by estarzinger View Post
By the way, wave heights are NOT a normal distribution . . .they follow an approximation called the Rayleigh distribution. And the "sigma" used in this context is often/usually the significant wave height, rather than the statistical standard deviation of the normal distribution. (and that can be a bit confusing because the Rayleigh also obviously has a standard deviation).
No problem - my background is in spectroscopy (light waves) which uses Rayleigh scattering and distributions. I should have caught on from the start that water waves would follow those statistics also.

It doesn't matter in practice for me however, because when caught out on the far side of statistical waves, I'm never too thorough in determining whether those waves were 1.86x or 2.1x the significant wave height!

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Old 29-12-2013, 17:00   #93
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Re: Legitimate Bluewater Question

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Old 29-12-2013, 17:24   #94
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Re: Legitimate Bluewater Question

Krogensailor, if you have something to say, jump in and say it.

Evans, thanks for clarifying the "sigma" issue. I should have guessed it, but it sounded so specific, and related to harbors.

In the Low Speed Chase incident, did wave reflections add to the worst-case wave height? Or was the shoaling gradual enough that any reflections off the rocks were attenuated sufficiently to not matter? There are all sorts of non-statistical wave interactions when we get close to steep shorelines. And when the incoming seas meet the "hydraulic jump" standing wave at a river bar on a strong ebb...
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Old 29-12-2013, 17:47   #95
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Great now I got to go get a degree to take part in all these discussions. The other thred is converting math to hull speed. Never thought it was all so complicated. 1 take boat out. 2 raise sails. 3 find point that fills sails. If no wind drink beer.
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Old 29-12-2013, 17:54   #96
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Re: Legitimate Bluewater Question

That's OK. I'll wait till you guys are done befuddling the rest of us.
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Old 29-12-2013, 17:58   #97
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Re: Legitimate Bluewater Question

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In the Low Speed Chase incident, did wave reflections add to the worst-case wave height?
We don't really know, but believe it was mainly the shoaling effect.

The bar they got slammed on is exposed and somewhat isolated and does not appear to have major wave reflections on it.

Waves around land are way more complex than presented in that report. Reflection is just one of (perhaps a half dozen) several possible effects (current is I think perhaps often the biggest) that could contribute. But we did not want to make the report too technical and out of reach of the typical offshore skipper. The team wanted to (and did) come up with a simple formula that we hoped all offshore sailors could understand and use, and which has enough fudge factor in it to include other possible effects.

And I was just guessing what Ann meant . . .perhaps she meant something else.
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Old 29-12-2013, 18:22   #98
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Re: Legitimate Bluewater Question

There now Ken, do you see what you have done. You have started a whole serious thread with sigma's and 2 - sigma's and 1.86 x significant waves and hydraulic jumps and we all thought you were just blowing your oyster.
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Old 29-12-2013, 18:22   #99
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Re: Legitimate Bluewater Question

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Originally Posted by scuba0_1 View Post
Great now I got to go get a degree to take part in all these discussions. The other thred is converting math to hull speed. Never thought it was all so complicated. 1 take boat out. 2 raise sails. 3 find point that fills sails. If no wind drink beer.
amen to that except for my step 2 is drink beer then raise sails.
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Old 29-12-2013, 18:38   #100
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Re: Legitimate Bluewater Question

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Great now I got to go get a degree to take part in all these discussions. The other thred is converting math to hull speed. Never thought it was all so complicated. 1 take boat out. 2 raise sails. 3 find point that fills sails. If no wind drink beer.
You forgot:
4a - hit land if you want to be like video B
4b - don't hit land if you want to be like video A

The required choice at this stage does complicate your simple formula somewhat…

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Old 29-12-2013, 18:51   #101
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Re: Legitimate Bluewater Question

How do you folks feel about motorsailing during the heavy winds and blowing swell? We've heard from the motor and not sail group, and the sail and not motor crowd. We spend so much time successfully motorsailing around the Med. due to lack of wind. Would motorsailing under storm sails be the answer? Seems like it might help with steering. Your opinions?

'Just a shot in the dark to get the thread back on topic.
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Old 29-12-2013, 18:56   #102
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Re: Legitimate Bluewater Question

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Originally Posted by estarzinger View Post
We don't really know, but believe it was mainly the shoaling effect.

The bar they got slammed on is exposed and somewhat isolated and does not appear to have major wave reflections on it.

Waves around land are way more complex than presented in that report. Reflection is just one of (perhaps a half dozen) several possible effects (current is I think perhaps often the biggest) that could contribute. But we did not want to make the report too technical and out of reach of the typical offshore skipper. The team wanted to (and did) come up with a simple formula that we hoped all offshore sailors could understand and use, and which has enough fudge factor in it to include other possible effects.

And I was just guessing what Ann meant . . .perhaps she meant something else.
People wanting to stay off the rocks (or beach) should read that Low Speed Chase incident report. While there's plenty of good insight about crew preparedness and safety equipment and emergency communications / response, for me the biggest take-away was this: Just because you don't see breaking waves as you are approaching the shore, there can often be a significantly bigger wave that's going to be steeper, faster, and breaking further out than you expect.

Sure, I knew this before reading the report. But seeing the tracks of all the boats that were sailing around those rocks (the Farallon Islands), and having sailed there many times myself (usually further off), it really hit home in a way that made it personal.

This isn't just for racers, or just about the Farallon Islands. Many times cruisers have anchored off a beach, thinking that they were comfortably beyond the breakers, only to find themselves fighting for their boat and their lives. I know of several boats that were sailing into San Francisco Bay, seemingly a comfortable distance from the shore, and were caught by these 2-Sigma waves. Many of these crews have died.

So that's an important lesson, and what this thread is about.
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Old 29-12-2013, 19:00   #103
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Re: Legitimate Bluewater Question

Below is the answer from Mack Boring (us yanmar distributor) on max heel angle. . . .

This is a common question and there are several answers. All information is only accurate if the oil is at the full mark on the engine and transmission dipstick and the coolant is full.
1. If the prop shaft angle is 8 degrees or less on a parallel drive engine. Constant heel would be 30 degrees or less with peak heel being 40 degrees. NOTE! Peak heel means, The boat is running at up to 30 degrees and hits a wake and heels over to 40 degrees for 10 seconds or less.
2. On a parallel drive, if the prop shaft angle is 8 to 15 degrees, constant heel would be 20 degrees and peak would be 35.
3. If there is an angle drive transmission and the engine angle is O, constant heel would be 30 degrees and 40 degrees.
4. If the engine with the angle drive transmission is installed at an 8 degree angel. The constant heel would be 15 degrees and peak would be 20.

Remember that if you are sailing beyond constant heel recommendations, there is a chance that the through hull sea cock will come out of the water. This could cause serious engine overheating. I hope this is helpful. Larry
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Old 29-12-2013, 19:50   #104
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Re: Legitimate Bluewater Question

Fully agree with the experienced observations made by Estarzinger, and Ann T Cate on the 50Knt video

Also as Boatman said, “Its all down to forethought and planning”

There is only “ONE” legitimate question that every sailor needs to continually ask.
Am I proactively prepared to minimize risk if (this??) fails/happens now in (these??) conditions with my crew?

When you stop asking that question, you are putting yourself and others in danger, whether blue or brown water sailing
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Old 30-12-2013, 07:00   #105
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Re: Legitimate Bluewater Question

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Originally Posted by Ann T. Cate View Post
Go Boating Now, and everybody else,

First off, I have to say that I think you and the other guys who have said that one should keep flexible in one's approach to the weather one encounters are absolutely correct. However, I'd have to add that the people who think something like "I've got a big engine; it'll get me out of trouble," are also being naive--it may, but it also may not. Too many less than perfect decisions get made by too many of the "links" in the chain. And it's how life is. Some maintenance just doesn't come out as expected, and you don't know it till it has failed. In a motor yacht, if the engine fails, she doesn't have backup; the sailboat has her auxiliary.
I think you misunderstand what I was trying to say. Jogging under reduced sail ( note the word sail) using the engine at low revs is a very good technique in modern yachts with reliable and strong engines. Most yachts these days are far closer to motorsailers in the size of their engines.

I was not alluding to using your engine "solely" to get out of danger, though sometimes its all you have.

Quote:
I've got a big engine; it'll get me out of trouble," are also being naive
Quote:
the sailboat has her auxiliary
The concept of an Auxiallary engine is out of the past, a 75hp engine typical on many 38-40 footers is not an "auxiliary "



Any hubris, of that nature, but also including "I can raise my main in a flash etc: can cause trouble , relying on any part of a boats systems, can cause issues, especially if they are unreliable through maintenance issues. But its not specific to engines.
Quote:
I really think sails are the sailboat's primary method of propulsion: IME boats usually can sail faster than they motor. IMO, in winds over say, 45, the sailboat will be far more comfortable with some sail area up, she will be more stable, more comfortable for the crew, less tiring.
I dont believe I or anyone ever mention solely motoring in a storm, Ive seen it done , Ive been in a boat like that , like everyone, I always have "some" sail up.

Do people actually read posts.!

Note that most modern boats with comparatively large engines,can reach hull speeds with their engines, Its no longer the truism that you mention.

Quote:
With the shorthanded sailing most cruisers do, less tiring is very important, because over 45, it's noisy, the motion is more vigorous so sleep is harder to come by, at the very same time one needs more rest to function effectively. It is in these conditions if you are going into it at all, that waves sweep the decks, and lines are liable to be swept into the water.
This is true to a point. the alternative, running off, however has many serious side effects, often a boat can forreach, with a little sail and the engine in slow ahead, on AP, in quite high seas. The boat is stable, ( because of heel) , is presenting the strongest point to the sea, and with the wave on the forward quarter bow, is often a very good ride.

In reality fore reaching is a form of heaving too, I like it because I have found it to be more stable that unattended heaving too in modern boats, particularly theses with lightly immersed fore foots.


Quote:
Now, for the idea of approaching harbor in a storm.

As a general comment, mostly its a bad idea, some harbours, say like Cherbourg of course, but in general a bad idea.


dave
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