Fixed or swing keel, which is better? - Page 2 - SailNet Community

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  #11  
Old 03-20-2008
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I'm not a big fan of water-ballasted boats because water is a relatively lousy ballast medium.

First of all, it isn't particularly dense, especially when compared to the same mass of lead. Second, most water-ballasted designs have the water ballast tanks relatively high up, making the ballast even less effective than it would be otherwise. This leads to the boat having a higher center of gravity than it would if it were properly designed with a lead or cast iron keel.

Third, some smaller boats that are water-ballasted, are exceptionally unstable if you forget to fill the water ballast tanks, and that can lead to disaster if you've forgotten to fill the tanks. There are a couple of cases of water ballasted MacGregors capsizing because the tanks weren't filled or weren't filled completely, and in at least one case led to some deaths.

Yes, I know water-ballast is used on a lot of high-end racing boats... but that is for a very different reason. It is used to allow the captain to shift ballast from one side of the boat to the other, essentially a replacement for human rail meat. These boats also have a rather large keel that provides the bulk of the stability for the boat, where the smaller, trailerable, water-ballast designs do not.

If shoal draft and high stability are important, get a trimaran or catamaran or a stub-keel with centerboard, rather than a water-ballasted design.

I also think it is a bit foolish to invite the ocean on-board when a better design would not require it.
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  #12  
Old 03-20-2008
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Thanks, Very informative. I was looking around at large trailer sailors and saw a couple that were water ballasted. Wanted to know the skinny b/c, of course, every company that incorperates it into thier ships is gonna swear by it.
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Old 03-20-2008
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A water ballasted keel, weighs 64 lbs per cf, the same as the medium it's suspended in. Lead on the other hand, weighs 708 lbs per cf. Which do you think is more effective at stabilizing the boat?
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Old 03-20-2008
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There's a good thread on water ballasted boats here:
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Boats that are water-ballasted often lose a lot of interior stowage space or cabin space to the water ballast tanks. A cubic foot of water only weighs 60-64 lbs. A cubic foot of lead weighs about 705 lbs. That means for a boat to have 1000 lbs. of ballast, you'd need about 16 cubic feet of water or 1.5 cubic feet of lead—big difference.
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Old 03-20-2008
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Quote:
Originally Posted by TrueBlue View Post
A water ballasted keel, weighs 64 lbs per cf, the same as the medium it's suspended in. Lead on the other hand, weighs 708 lbs per cf. Which do you think is more effective at stabilizing the boat?
But some could be worried about lead poisoning?...

Seriously though...trailer sailing is something that is actually considered more of day sailing - in which case, does it matter if it gets you out there and you can drag it home and it uses water ballast? For all the slack that M's get - if properly used according to instructions, it is no different than any of the 'normal' boats. Practically almost all boats can capsize, roll over etc if operator doesn't handle their boat properly.

Interestingly enough - historically speaking, boats of 100+ years ago - used water ballast and cargo weight as ballast. They managed for several hundred years criss crossing oceans - quite successfully.

Amazingly - old is new technology once again....
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Old 07-30-2014
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Wink Re: Fixed or swing keel, which is better?

Freighters use water ballast all the time. How do you think we got zebra mussels in the Great Lakes. I like my shoal keel. But I also like full keels to as they maybe slower they are more comfortable in larger sea (25-35 ft) or more.
Sailors die when they use regular ballast type or water type.
You have rules for your boats performance. So do not blame the ballast. If you have too much sail up and you get knocked down (micro burst are what I call a exception) then you were not paying attention to the conditions, wind or the tell tail wind over water bursts and cloud conditions. Like I told a friend that bought a water ballast boat ...go slow and learn what the boat tells you.
I have run aground a few times because of my mistakes (a unmarked channel btw while gunk holing). I missed a channel by a few meters. Plain and simple and go slow and learn about your boat and what she tells you. When in doubt come about 180 degs if you have the room and can. Or fire up the iron sail and drop sail or the rear hook to stop you going forward. Yes I have two winches on the aft deck and two small Danforth anchor for when I do beach myself on purpose to do some work on the undersides on a soft bottom ( zinks / paint / thru hull fittings ) as the tide goes out (cheaper than a haul out) or to use in tight gunk holes tied off to trees. And no it is not a small boat...Maple leaf 48. Well may be small to some of you.
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Old 07-30-2014
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Re: Fixed or swing keel, which is better?

Wow. Talk about the zombie thread that won't die. First post 13 years ago. Then revived seven years later only to go dormant again. Now revived yet another six years later. Perhaps this thread will still be getting posts in 2020. I'll have to check back then to see.
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