I'd look for a Tanzer 22. There are a bunch out there in decent condition for good prices. Relatively big cabin and great cockpit for a 22 footer. Medium weight and good performance. Old, but loved, so a lot have been well maintained or upgraded.
Pocket cruiser recommendations for family of 3
- Thread starter Joe the Sailor
- Start date
The density of seawater is about 1000 kg/m^3 where, for example, the density of aluminum is 2,710 kg/m^3. I know of no boat that boasts, "keel made of heavy aluminum for improved ballast when reaching." Water ballast is not the favored way to ballast in terms of straight ballast. It is hard to concentrate the weight low in the boat. It takes up more interior space and can even be harder to move from one side to the other when tacking than, say, a sandbagger. The only advantage, I can see, is for trailerability. I know big, ocean racers were sometimes built with water ballast, but a lead weight on a rail, to move back and forth with an electric motor, would work better. Maybe there are racing rules that favor water ballast over movable solid weights.
However, water is heavy, compared to fuel, for example, and if you have to carry a big tank of it, put it low in the boat and in the center. Weight is weight inside the hull and will serve to either help ballast the boat or unballast the boat, depending on where you put it.
As for performance of a water ballasted boat, the same number of pounds of water will displace just as much as lead in your hull. You just may not need as much lead because you can concentrate its location more efficiently.
-Will (Dragonfly)
However, water is heavy, compared to fuel, for example, and if you have to carry a big tank of it, put it low in the boat and in the center. Weight is weight inside the hull and will serve to either help ballast the boat or unballast the boat, depending on where you put it.
As for performance of a water ballasted boat, the same number of pounds of water will displace just as much as lead in your hull. You just may not need as much lead because you can concentrate its location more efficiently.
-Will (Dragonfly)
Only two things matter for ballast. It needs to be heavier than the rest of the boat in a fixed location. Thats it.
Take a water bottle and fill it halfway with water and place in water. It will bob nicely upwrite, but not perfect since the water ballast is not fixed.
Different bottle, fill with plaster. When plaster hardens float bottle. It will bob same way, however it will be the most stable bottle you have ever seen. It is stable because the space above the plaster is less dense than the plaster.
If the weight of the water in a water ballested boat is in a fixed location below the less dense part above, then you have some nice stability.
The addition of the ballast moves the center of mass towards the ballast.
Ocean racers continue to use water as MOVABLE ballast to take the place of crew on the rail. The Figaro 2 does, as does the brand new J/121. The common link between most of these boats is they are designed to be sailed shorthanded, and its easier to find 128 gallons of water to put on the rail than it is to find 5 extra crew. Tack? just pump it to the other side.
Interestingly, the new Figaro 3 uses its foils not to 'foil' out of the water, but to supply righting moment. Basically the opposite approach to water ballast. That trick adds 5% speed increase to the new boat.
http://precisionboatworks.com/customer_support/company.php
Cast Lead per cubic foot weighs 708 pounds
Cast Iron per cubic foot weighs 450 pounds
Concrete per cubic foot weighs 140pounds
Salt water per cubic foot weighs 64 pounds
Fresh Water per cubic foot weighs 62 pounds
Cast Lead per cubic foot weighs 708 pounds
Cast Iron per cubic foot weighs 450 pounds
Concrete per cubic foot weighs 140pounds
Salt water per cubic foot weighs 64 pounds
Fresh Water per cubic foot weighs 62 pounds
So, why not do that with a much smaller block of lead moved along rails? It would take less energy to move and provide lower CG. Is this so you can blow the ballast tanks when on a down wind run? Make the boat lighter? That has to only work well for longer races. Pumping a hundred plus gallons of water in and out of a tank isn't fast. The other option I can envision is using your on-board fresh water supply, since you have to carry water anyhow, but by the end of an ocean race, you may be short on ballast unless you can replace the lost fresh water with seawater without mixing them.
The Old Man's last couple of ocean racers had water ballast. I never talked to him much about that aspect of his boats.
-Will (Dragonfly)
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Water doesn't move when you yell at it, unless of course youre Jesus
It would not be easy moving 1000 lbs of lead from side to side. And you have to secure it. The water pumps from tank to tank in a bit less than 10 minutes. You drain it if the breeze is light. You always use seawater. Would be crazy to use up fresh water.
Ah! Now that is the real benefit. For a long down wind leg, being 1000 lbs lighter can really pay off.
-Will (Dragonfly)
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Plaster and water... not exactly the same density, but I'll play along. I also know this thread has gotten way off topic
, but this is an interesting discussion.For those who've made it this far in the thread and aren't beating their head against the wall, check this out: (ripped from http://kobernus.com/hunter260/water_ballast/water_ballast_paper2.html)
My argument is that the water "ballast" does nothing here to right the boat in illustration 4... it's only the hull of the boat (the air inside the hull), that's contributing to the righting force. CB shifts to the right, and represents the center of mass of the water displaced. Same thing happens in a centerboard dinghy; as she heels, more hull is pressed under water, displacing more water than when sitting upright. This newly displaced water is what's forcing the boat to right itself. You know, Archimedes principle, stability curves, all that jazz (http://marine.marsh-design.com/content/understanding-monohull-sailboat-stability-curves).
Illustration 4 shows a water ballasted hull with its tank below the water line. Now remove the water ballast and hull (tank) that surrounds it. She'd look like a catamaran, right? The righting moment would still be the same, with or without the water ballast. (We're neglecting the weight of the water tank walls here, so that the CG is the same in both examples.)
If water ballast beneath the surface added any righting force, we'd all have sailboats with hollow keels that get filled with water once launched. Make it a huge keel relative to the boat's displacement - 5,000 lbs of water? 10,000 lbs? It wouldn't matter. Except for the weight of the fiberglass (or whatever material) forming this keel (i.e. water tank), this water filled keel adds nothing to the force of keeping the boat upright. If it did, why do all these silly boat manufacturers keep insisting on making boats with lead keels? Water sure is a lot cheaper.....
Again, this is all valid until that huge keel is brought above the surface, like during a knockdown. Then you have a huge weight working in your favor. Once that water keel is submerged again, the boat of course will continue to right itself, but not any more so than if that keel wasn't there at all.
Well all I can do is add first hand experience.
I sail an H26
The boat is ginger in a very light breeze and will heel in a 5mph breeze like most boats do in a 10 mph breeze.
But once she heels about 5 deg it feels stiff and stops being tipsy
On the TRAILER she is a lot less intimidating to haul than my Balboa 26 was
I sail an H26
The boat is ginger in a very light breeze and will heel in a 5mph breeze like most boats do in a 10 mph breeze.
But once she heels about 5 deg it feels stiff and stops being tipsy
On the TRAILER she is a lot less intimidating to haul than my Balboa 26 was
Joe,
If you remove the water ballast, center of gravity moves up, righting moment (gz) decreases, so the water ballast does help right the boat. With a deeper, heavier lead keel, center of gravity moves down, righting moment increases even more. That's why a boat with a lower heavier keel would be less tender than the water ballasted boat.
As rgranger has noticed with his boat, hunter's water ballast system works fine. We used to have a hunter 23.5, and I can tell you from experience, if you forget to fill the ballast tank, and go out and raise the sails in 20 knot winds, you get flattened by the first gust and wonder what the heck just happened
(Though to be fair, I seem to remember forgetting to drop the centerboard, as well that time. Regardless, it was a memorable occasion).
If you remove the water ballast, center of gravity moves up, righting moment (gz) decreases, so the water ballast does help right the boat. With a deeper, heavier lead keel, center of gravity moves down, righting moment increases even more. That's why a boat with a lower heavier keel would be less tender than the water ballasted boat.
As rgranger has noticed with his boat, hunter's water ballast system works fine. We used to have a hunter 23.5, and I can tell you from experience, if you forget to fill the ballast tank, and go out and raise the sails in 20 knot winds, you get flattened by the first gust and wonder what the heck just happened
(Though to be fair, I seem to remember forgetting to drop the centerboard, as well that time. Regardless, it was a memorable occasion).
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jssailem
SBO Weather and Forecasting Forum Jim & John
- Oct 22, 2014
- 22,884
There is a theory.
If God wanted your boat to use pressureized water ballast he would give you a submarine.
If God wanted your boat to use pressureized water ballast he would give you a submarine.
Concerning the water ballasted hunters... In a post on the 3rd page, Serenity on the Hudson summed up out experience with our hunter 23.5 when he said it was a handful in heavy air. That was totally true. It kept us on our toes. It was also hard to make progress up wind when conditions picked up with wind and waves. The boat did sail well most of the time however, just easily over-powered. The first thing we noticed when we got our Seaward was that it just accelerated when it got gusted. It just wasn't as "exciting" as the hunter was, but was way more suitable for overnight cruising for us.
Of course, but...
That's not exactly what Joe is saying. Although, I think his point is difficult to defend because of how we think a boat should look.
Joe is saying, especially in the case of his illustration, that if you simply built your boat without the area of the water ballast tank on the inside, just open up the bottom so your cross sectional shape followed the outline of the tank without a bottom, you would get a shape reminiscent of a catamaran or a tunnel hull. In that case, joe is right, the righting moment wouldn't be any different.
However, ballast tanks don't run the length of a boat, normally, and to remove the boat bottom just where the ballast tank was, would cause issues like drag and cavitation (the capturing of cavities of air) from wave action and heeling. You could design the area with the bottom but to fill automatically with thru-hulls and an air escape at the top. It would be essentially the same as water ballast tanks, only you wouldn't be able to empty it for faster down wind sailing.
Here is a water ballast system concept drawing that illustrates another advantage. Instead of using a centered tank, the water is pumped, as Jackdaw referenced, to the windward side. The result would mean that less weight would have greater righting moment due to the increased lever arm length, up to a certain angle of heel. After that, it would work against you because it would cross over the center of buoyancy before the midship line did.
They do use water ballast in catamarans too.
-Will (Dragonfly)
Attachments
Put the weed down. Thats like saying if im drowning all i have to do is roll over and ill float higher. If an iceberg flips over it will displace less water. BS. Thats the same false garbage that heeling reduces wetted surface, nope. Thats only for multihulls
Now wait a minute, I'm not sure I'm buying that. He's then going on to say since the water ballast is under the water it isn't doing anything and proof is if you cut out the ballast tank and ballast the righting moment is the same? Not an apples to apples comparison, the way I see it.
Thinking of it another way, if you added ballast below the water line in the form of lead, wood, or gold bullion, for that matter, and it weighed the same as your ballast tank of water, are you then saying ballast of lead below the water line makes no difference in righting moment because it's under the water, and if you cut out the ballast and the hull form it sat in, it would make no difference? Weight is weight whether it's an equivalent amount of water or lead. Show me the light
Thinking of it another way, if you added ballast below the water line in the form of lead, wood, or gold bullion, for that matter, and it weighed the same as your ballast tank of water, are you then saying ballast of lead below the water line makes no difference in righting moment because it's under the water, and if you cut out the ballast and the hull form it sat in, it would make no difference? Weight is weight whether it's an equivalent amount of water or lead. Show me the light
Well, there is less ice on top of an iceberg than on the bottom
You are right, of course, but I think your are not seeing his point. The heeling force pushes the boat forward and downward to the lee side. This increases displacement (volume of water) and that means more weight (downward force) is countered by the increased buoyant force of more hull volume. The real issue is where that buoyant force is centered. As you heel, the center of buoyancy moves leeward and counters the heeling force. To heel more, the heeling force needs to increase, which, for most designs, moves the center of buoyancy out even more and increases the buoyant force until the rail is actually underwater. The more round your bilge is (like a log) the less the CB will move to counter the heeling force. Flat bottoms are the best. High topsides are great too. The most stable form is actually a half log. A half round shape will always roll over until the flat face is down. This is in the case of evenly distributed density across the cross section. The CG is closest to the flat surface and the center of buoyancy moves the farthest out from center as it tips. Note how full designs have changed in the last couple of decades. Bottoms are being flatter and flatter. Like a surf board.
-Will (Dragonfly)
Yes, weight is weight is weight. (Which weighs more, a pound of lead or a pound of feathers?)Thinking of it another way, if you added ballast below the water line in the form of lead, wood, or gold bullion, for that matter, and it weighed the same as your ballast tank of water, are you then saying ballast of lead below the water line makes no difference in righting moment because it's under the water, and if you cut out the ballast and the hull form it sat in, it would make no difference? Weight is weight whether it's an equivalent amount of water or lead. Show me the light
However, in terms of buoyancy, it's weight relative to the water it's displacing. Density.
I owned a HyFly 175 sailboard. The board alone weighed about 10 lbs. The "175" in the model was the amount of water it displaced. Of course, this board floats. Although it weighs 10 lbs (on land!) its shape displaces 175 liters of water when fully submerged, which works out to about 386 lbs. This is the amount of force the body of water is exerting on the board to keep it above the surface.
I have a 10 lb mushroom anchor. Maybe its shape displaces 1 L of water. It sinks (in water).
If we're trying to keep our boat upright, which would we rather have attached under the water line, say on the keel? They're both 10 lbs. But they displace differing amounts of water.
Pool season's over here, but next spring, take a 55 gallon trash bag to the pool. Fill it up and tie it, underwater. 55 gallons is 625 lbs of water! It can't be lifted above the surface! But underwater, it's close to neutral buoyancy. It won't pull you to the bottom of the pool. The medium inside the bag (water) equals the density of the surrounding medium (the pool), so it's about neutral buoyancy.
Humans are ~70% water. I weigh 170 lbs. Do I shoot to the bottom of the pool when I get in? Nope, actually, depending on the amount of air in my lungs, I can sink, float, or be relatively neutral. When I'm neutral in the water, I'm displacing exactly the amount of water to equal my weight (or more appropriately, mass).
My point is that with ballast tanks filled with water, which equal the density of the surrounding medium, don't serve to keep the boat upright. Again, make a keel filled with 10,000 lbs of water, and attach it to a dinghy. Would it be instantly pulled to Davy Jones' locker? What if the keel was filled with 10,000 lbs of lead?
I've so far continued posting to this thread because there's so much B.S. out there on the internet, and the info I found on water ballast was suspect. It just struck a chord with me I suppose.
This stuff seems so obvious to me. Maybe I'm not explaining things clearly. Anyhow, time to get the kid ready for school. I have nothing to prove here, and if I'm not helping anyone out with all this, I've got a boat I should be working on.
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