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Old 10-08-2011, 06:15   #1
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Weight Questions

Kind of a novice question here:

How does weight both displacement and ballast weight affect the overall design and sailing performance of a monohull sailboat?

I am now looking for a true coastal or maybe even a blue water cruising boat, and while reading the specifications of some boats that interest me. I have noticed a wide range of weights for boats in the 30 to 35 foot range. It seems like even in boats of the same length weights vary a fair amount.

My first sailboat was a 1200 lb daysailer. In some ways this was a nice handling little boat. But in other ways it was a bit difficult to sail well. So I guess my question is this: How will a larger heavier boat handle vs a smaller lighter vessel? I used to get "stuck in irons" (I think thats the term I am looking for) a lot in the little daysailer.
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Old 10-08-2011, 14:47   #2
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Re: Weight Questions

Heavier boats tend to have an easier motion in a seaway; are slower to accelerate; will carry more weight without adversely affecting performance; take more sail area to move especially in light air; if long keel, will be more directional stable and easier to steer but slower to answer helm and more likely to end up in irons.

Light displacement are faster to surf so better running DDW in a seaway; with low mass, accelerate more quickly in light air; not faster to weather as they may compromise ballast and form stability for light displacement; not necessarily faster over all in light air; almost guaranteed to be fin keel; less carrying capacity; may require crew weight on the rail to carry optimum sail area with wind forward of the beam.

There are degrees of displacemnt to length ratios. ULDBs are virtually useless for cruising under 40' in length because they sacrifice most everything to the god of light weight. Heavy displacement without commensurate increased sail area tend to be slow in light air. Full keel boats are slower in light air because of wetted surface, not necessarily displacement. Full keel boats may be faster in moderate to heavy conditions because they tend to be more directionally stable.

Sure others will come up with a ton of differences. Personally, I appreciate the heavier end of the spectrum. Find them to have an easier motion and easier on this old body. Usually can create a sail configuration that will make up for most of the light air penalty.
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Old 10-08-2011, 15:16   #3
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Re: Weight Questions

More weight equals slower for a given length. More keel weight means more righting moment which means better ability to sail to weather. Longer keels mean more directional stability. Longer keels also man more surface area per amount of displacement which is less efficiant. Fin keels mean more efficient to weather yet more yawing off the wind.

There are plenty more variables, those are just some of the basics.
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Old 10-08-2011, 15:33   #4
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Re: Weight Questions

There's piles of info out there (all of it better than what I'm about to type), but my $0.02:

- Heavier displacement / bigger keels tend to tack easier because once they swing, they keep going.
- Lighter displacement boats are generally easier to maneuver and don't fall victim to prop walk as much. Most of the boats that *will not* back to starboard are full keel (or power boats with smaller rudders).
- More people are puking on lighter displacement boats.

It's very similar to a Porsche vs. a Lincoln Town Car. One is a lot more fun to drive than the other, but you might change your mind if you had to drive across the country.
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Old 10-08-2011, 16:22   #5
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Re: Weight Questions

Andrew Simpson on light displacement is not as bad as cruisers think:
Light Displacement - lighter means faster says Andrew Simpson

Pick up any book by Marchaj for reasons why heavier is better
Seaworthiness the forgotten Factor
Amazon.com: Seaworthiness: The Forgotten Factor (9780877422273): C. A. Marchaj: Books

Ted Brewer on stability:
Good Old Boat - Is your boat stable? article


Ted Brewer on keels:
Good Old Boat - Keel design: What's best? article
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Old 10-08-2011, 16:48   #6
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Re: Weight Questions

That's kind of what I thought about tacking, heavier means more momentum. But also more energy to get it moving. I'm not really very interested in racing, so the Porsche of the water is not really what I am seeking., Thanks for the simple feedback.
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Old 10-08-2011, 16:52   #7
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Re: Weight Questions

So a full keel will stay on a set course better tan a fin keel or a shoal draft keel?
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Old 10-08-2011, 17:00   #8
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Re: Weight Questions

on lighter boats loosen the main sheet when tacking and you will find the boat a lot less prone to getting into "irons",as this allows a lighter boat to bear off when way is lost after tacking.
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Old 10-08-2011, 17:03   #9
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Re: Weight Questions

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Originally Posted by kcmarcet View Post
That's kind of what I thought about tacking, heavier means more momentum. But also more energy to get it moving. I'm not really very interested in racing, so the Porsche of the water is not really what I am seeking., Thanks for the simple feedback.
The Olson 30, Hobie 33 and J-33 I've sailed on tacked as quick and easy as dinghies, but I've never been out in 30 knots on them to see how it works in those conditions.

On the other end the Morgan OutIsland 41 that I've sailed I've never had a problem tacking, but I've read on the web by more than one owner that they sometimes have to start their engines and use the prop to help them through a tack.

Hard to generalize with sailboats. So many factors add up to the sailing qualities, not just one thing.

John
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Old 10-08-2011, 17:06   #10
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Re: Weight Questions

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Originally Posted by cal40john View Post
Hard to generalize with sailboats. So many factors add up to the sailing qualities, not just one thing.

John
Very sound words
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Old 10-08-2011, 17:24   #11
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Re: Weight Questions

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Originally Posted by kcmarcet View Post
So a full keel will stay on a set course better tan a fin keel or a shoal draft keel?
First of all, both fin keels and full keels can be shoal draft. That only means it doesn't draw is much as a deep keel.

A full keel resists turning more than a fin keel. This means it takes more energy to tack it, but once it's on course up to speed it will probably need less rudder to maintain that course, especially when going to weather. A rudder not only turns a boat, but also slows it down.

Think in terms of inertia. A heavier boat will not accelerate as fast out of a tack, but it wall also carry its momentum through a tack better than a lighter boat. I'm faculty advisor to a university sailing team, and I sometimes take team members out for a sail on my keelboat, which displaces 15 tons. They do a terrible job tacking it because they turn too quickly. On the CFJs they normally race, they roll-tack, which means they virtually stop the boat while turning but then snap it back to help it accelerate on the new course. Can't do that with a 15 ton boat.

My current boat has never been in irons. When I turn it into the wind to furl the sails, they are often both put away before the boats has stopped its forward motion.
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Old 10-08-2011, 17:24   #12
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Re: Weight Questions

In your search, look at the heavy weight boats and their weight, check out the lite weight boats and note the weight..
then have a good look at those that fall somewhere in the middle..
you'll find good performance, great stability, ease of handeling, and comfortable ride..
a good middle weight performance offshore boat will work a lot like a gyro.. the faster the boat, the more comfortable the ride...........
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Old 10-08-2011, 18:10   #13
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Re: Weight Questions

*Heavier boats are just as fast as light ones... meaning... with enough sail area up, or with decent wind, all displacement sailboats are only limited by the LWL (load waterline length) to reach their "hull speed" *Light boats will accelerate to that hull speed faster if they have enough sail area up, and are likely faster in light wind. (due to sail size restrictions by the skipper or sail inventory on the heavy boat). * Sailboats are often designed with a ballast amount that is highly dependent on their beam; wider boat less ballast, narrower boat more ballast. Of course it's not a set rule. *My experience with longer keel boats (HC38, WS32, Baba 30) is that they can have trouble tacking , especially in lighter winds. It can take a specific technique to get them to come around, if your timing was wrong, you get to sail a little further and try again! * long keels tend to track better requiring less work at the helm and for your autopilot. *Although heavier boats theorhetically do have a little more momentum to pound through chop, My experience is that lighter goes through even better. Case in point: I was working my way down the Chesapeake once in my Passport 47. 35 knots of wind and pretty ugly 6+ footers rolling down the bay. I was making decent progress under sail without tacking, but the waves would slow me down on a regular basis. Between wave I would get to hull speed. I noticed a boat gradually coming up from behind, when it passed me motoring, it was a hunter 40! He was riding the top of the waves... I was plowing through with water running down both sidedecks...
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Old 10-08-2011, 18:22   #14
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Re: Weight Questions

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Originally Posted by Cheechako View Post
Heavier boats are just as fast as light ones... meaning... with enough sail area up all displacement sailboats are only limited by the LWL (load waterline length)

True, all FULL DISPLACEMENT sailboats are limmited to LWL.. (heavy weights)
BUT, all sailboats ARE NOT Full displacement.and ARE NOT limmited to LWL..
Many fall into a catagory somewhere in the middle........

AND FALSE, heavy weight sailboats are not as fast as light boats..
If they were, all PHRF ratings would be the same for any detremaned size, which they are not........
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Old 10-08-2011, 18:36   #15
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Quote:
Originally Posted by Randyonr3

True, all FULL DISPLACEMENT sailboats are limmited to LWL.. (heavy weights)
BUT, all sailboats ARE NOT Full displacement.and ARE NOT limmited to LWL..
Many fall into a catagory somewhere in the middle........

AND FALSE, heavy weight sailboats are not as fast as light boats..
If they were, all PHRF ratings would be the same for any detremaned size, which they are not........
It's a blanket statement. That leaves out all sorts of factors Sometimes when it's blowing 15 up I'll stomp new lighter go fast fin keels. In light air they will usually pass me by. If there's a chop running I have an advantage and am more comfortable. Comparable fin keel is probably running with a mast height of 55' I'm 65' so I'm carrying more canvas. The boc boats or open 60swould kick most tail so yes they are faster then a full keel boat. That is a different class of boat then o cruising boat. Light racers with water ballast and triple spreader rigs and hydrodynamic decks are a different deal so everyone is right kumbayaaa
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