At anchor

[twoblocktom]

Sitting at the marina the other night I noticed the boat we were on was laying at ease while some of the other boats around us were rocking and rolling to the wake of other boats and to rollers we barley felt. Enough that i would not enjoy relaxing on them. And some were much larger boats. I believe this was due to our full keel. So my question. If a cruising boat is at anchor for the majority of the time, what determines how comfortable we are at anchor? What would you most look for in a boat you were going to live at anchor in for an extended time?

[Ocean Girl]

I've been studying this ever since we went cruising :-). Location is a big deal, even just a few hundred feet can mean a nice comfy spot while others further out are rolling.

[Lizzy Belle]

Originally Posted by twoblocktom

I believe this was due to our full keel.

I think it's more due to the shape of the waves, and exactly where on the hull they hit the moored boat(s), then full keel or not.

What boat were you on? (The Santana in your profile is a fin keeler?)

[twoblocktom]

Yes, my santana, sadly is parked in my yard in Colorado. We were in Langkawi Malaysia. on leave from work there enjoying a week we may never get the chance to again. I'm sorry I cannot report the type vessel we were on but It/she was just laying so comfortable in the marina, while the other boats on ether side of us were thrashing about. RIGHT NEXT TO US!

[boatman61]

Originally Posted by twoblocktom

Yes, my santana, sadly is parked in my yard in Colorado. We were in Langkawi Malaysia. on leave from work there enjoying a week we may never get the chance to again. I'm sorry I cannot report the type vessel we were on but It/she was just laying so comfortable in the marina, while the other boats on ether side of us were thrashing about. RIGHT NEXT TO US!

You had a longer keel and sat on the bottom..

[TeddyDiver]

Width if the waterplane area, damping characteristics, the metacentric height and the wave frequency

BR Teddy

[twoblocktom]

Maybe someone knows what type of boat I was on. I was at the Langkawi sailing school on the s/v Kay Sarah. She took good care of us! Laying in the marina on night, we noticed the boats around us were thrashing back and forth to the point it would not be comfortable. She was calm one slip over. What was the difference?

[Wind River]

My Force 50, full keel boat usually sits very well at anchor and on its mooring. I notice other boats rocking quite a bit also and thought my comfort was simply because of the 52,000 lbs of weight.

Then I pulled both wood masts out for refinishing and put it back on it's mooring. It is almost unbearable now. Without the weight of the masts to counteract the keel it rocks beam to beam horribly with the wake of a passing boat. I began to wonder if I were if I were to replace the wood masts with lighter aluminum ones if I would create a boat I couldn't stand to be on at anchor.

Maybe this effect has something to do with what you were noticing.

[Cheechako]

It's a good question and probably unanswered. Short Fin keel boats do seem to hunt and veer a lot, but not sure that they roll more. as mentioned a short distance can make a big difference. I've seen boats in a marina rolling terribly alongside boats that are hardly moving. Go figure.
This one, a short fin keel: http://sailboatdata.com/viewrecord.asp?class_id=3031

[Lizzy Belle]

Originally Posted by twoblocktom

Maybe someone knows what type of boat I was on. // She was calm one slip over. What was the difference?

It's hard to compare "unknown boat X" to "unknown boats around boat X".

(And if you don't know what boat you were on, how do you know what type of keel she has?)

Also, behavior at anchor isn't the same as tied up in a slip.

The one boat I always notice heeling a lot with a strong wind from the side is the one docked behind me, a Hood 38. Most other sailboats, mine included, heel much less then she does. She's docked keel thingy up (I think the English term is "centreboard "?), but still a 4.50' draft.

A friend of mine was also having fun heeling - he has a Pearson 365. Both the Hood and the Pearson were heeling a lot more then I was (with a deep fin keel ).

[twoblocktom]

Fair enough Lizzy Belle! As I quizzed the instructor he could not tell me why some of the other boats around us behaved as they did and our boat behaved as she did. In a slip or at anchor, as you say, is not the same. So let me re phrase. Do different boats have different motion at anchor? What determines if a particular boat lays well?

[twoblocktom]

It was a 42' ketch and we had to dive on the bottom after running aground. It was a full keel. Sorry I can't be more exact.

[MYTraveler]

For a while, my boat was in a marina that had a lot of surge. To avoid any hurt feelings, I will comment only that there were two highly regarded blue-water, ocean crossing passage makers docked near me. In fairness, they were both a little smaller than mine (though they may have displaced more). Anyway, I couldn't help but notice how those two rocked as much as any of their size, and noticeably more than most. Having considered having one built before I ultimately decided that my needs were more in line with what I ended up with, one of the characteristics that attracted me to the brand was the reputation for stability (even though they look top-heavy).

So, I wondered whether purchasing that particular brand with an expectation of stability would have been a colossal misjudgement, and had a few interesting conversations about that concern. Apparently, I am not the first to notice the rolliness of these boats in a surgey slip. The factory has an explanation, that makes a certain amount of sense. Their theory is that every object has a resonant frequency. As a matter of physics, I believe that is right. The theory continues that their boats are tuned to have the resonant frequency at relatively small period, small energy waves/current/whatever. That is where I get lost. From my understanding/recollection of physics, if something resonates at a particular frequency, it will also resonate at integral multiples of that frequency. But, who knows.

Bottom line, I am firmly convinced that some boats rock more than others based purely on boat geometry -- in particular the shape of the bottom and how high the center of gravity (someone will know the nautical term for this) is.

[Lunita]

Perhaps a second hull might reduce rolling........

[Benz]

If I were going spend most of my time anchored or at a marina, I'd choose a nice, wide catamaran. Ditto if I were going to mostly motor around the Bahamas, and wanted a stable diving platform to park outside the reef where the diving is better. As for what makes monos more comfy, while it seems intuitive that lots of displacement is better, sometimes my full-keel, 10-ton 31-foot cutter rolls terribly in a wake. I suspect that a deep fin keel with a heavy bulb would be stiffer at anchor, but again that's only good for a marina queen.
Sometimes the bathygraphy of an anchorage or marina makes a difference too. In Cartagena you can anchor close inshore in about six feet, but as violent powerboat wakes come in from the deep channel, they pile up in the shallow part and become worse. Better to anchor further out in six or seven fathoms and not get Tsunami'd by every unruly wake.
Ben
zartmancruising dot com