launching a shallow draft keel vs. waterballast - SailNet Community
 
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post #1 of 7 Old 12-29-2006 Thread Starter
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Question launching a shallow draft keel vs. waterballast

Ok, so the general concencus is the Hunter 26 will be ok with it's water ballast system.
I guess the best word to use would be I "ADMIRE" a clean classic looking sailboat like the Oday 23, the Hunter 23, and the Paceship 23, I even think the Paceship 23 is a neat looking boat, what I've noticed is the displacement jumps up considerably when you move to a 25-26 foot boat.
I will have to look into the Catalina 25 again, I thought that was a heavy boat for trailering.
Is the tongue extension required to launch most shallow draft boats on a regular boat ramp like the Hunter 23.
I would like to keep the weight of the boat below 5,000 as to not stress out the Tahoe pulling around the state.
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post #2 of 7 Old 12-29-2006
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Also take a look at the Precision 23. It's a far more traditional look in a trailerable format, lead keel with 850lbs down below and a 22" draft with CB up. I've had mine in winds of about 35kts (not incredibly comfortable, but it worked). I wouldn't do that with a water ballast boat. Weight on a P23 is around 4000lbs loaded with gear. We usually use the tongue extension just to keep our wheels from getting too wet.

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post #3 of 7 Old 12-29-2006
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This answers a couple of things inherent in your quest. There is a trailer sailor mag, which would probably be the best choice for you, along with Good Old Boat. If you plan on towing a lot, and any distance, you should probably add a transmission cooler to your rig if it doesn't have one.

You will find ramps vary from lake to lake, and even on the same lake. A tongue extension would be a worthwhile investment.

The Precision is a very nice boat, but might be above the budget you mentioned.

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post #4 of 7 Old 12-30-2006
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I had a Catalina 22 with swing keel that I trailered and launched several times (mostly kept it in a slip). I did not need to use the tongue extension but having it is a good idea. I agree on the Precision 23. Great looking boats that are set up very nicely. I looked very closely at the Precision 28 a few years ago. I have no experience with water-ballasted boats but the conventional wisdom on this site seems to be against them. I would not buy one myself, preferring good old fixed lead instead.

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post #5 of 7 Old 12-30-2006
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I wonder why water ballast has such a bad reputation. After all when you calculate stability you don’t care what the ballast is made of because you only look at the weight, position of the center of gravity and center of buoyancy. Selecting different materials as ballast only changes the weight and how low the center of gravity can be. Water is weight and makes good ballast if the overall design is correct. After all a lot of things have been used to change a boats stability ranging from rocks to air so why not water? If you want to able to reduce the weight on a trailer water is a lot easer to add and subtract compared to rocks.
All the best,
Robert Gainer

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post #6 of 7 Old 12-30-2006
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34,
You answered your own question. For x amount of ballast the CG in a keel boat will be lower than the CG of a water ballasted boat with x amount of water ballast.
This of course does not even touch upon the possibility of operator error in the use of water ballast. Unless the ballast tanks are either topped off or empty a free surface condition will exist and result in a virtual rise of G and possibly making the boat dynamically unstable. The same effect could occur by holing the tank, although much less likely. ANY amount of water between empty and 98% full (topped off) with cause almost exactly the same free surface effect on GM.
Of course the lead keel will be more substantial in cross section than a centerboard with it's attendent benefit in lateral resistance.
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post #7 of 7 Old 12-30-2006
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Sailaway21,
Good point about free surface and it’s not often I hear someone discussing free surface and metacentric height. But my point is that if in the early design phase you select water as the ballast and make the necessary choices about hull shape and sail plan you can have a fine boat that is water ballasted. After all we are discussing a boat designed to be trailerable and some trailerable boats have no ballast at all and they just depend on hull form and crew weight for stability. If unballasted boats represent one end of the spectrum and a lead ballasted boat is the other end of the spectrum then what’s wrong with a properly designed boat midway that uses water ballast?

Your point about operator error is also well taken but because you can find someone who will mishandle any boat I wouldn’t rule out a boat type just because it can be mishandled. If operator error was a reason to rule out boat types you would find all boats removed from service because all boats can be mishandled by either poorly trained operators or idiots.

On the question of centerboards and keels I think a well designed centerboard is more efficient per square foot of lateral plane then a well designed keel on a small trailerable boat. And because the question of lateral plane is entirely separate from the question of stability and both problems have different requirements and limitations they should be discussed as separate issues.
All the best,
Robert Gainer
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