[Jeff_H]

I must admit that this has been running through my mind ever since I saw the original post yesterday. Its not simple, but its very doable.

I will start by saying I had never really paid attention to the design of a Cal 21 before. That is a wildly efficient hull, rig, keel and rudder for that day and purpose. I would have to think that it would be a good platform to do what you are proposing but it will take some serious skill to sail that boat if you remove the swing keel since stability from the deep draft with a bulb layout of the swing keel will be hard to replace.

I suggest that reading the comments, that there seems to some misunderstanding about how you would move water ballast on a boat this size. You don't pump it. You use a water tank that is mounted on a trolley that allows the water tank to be pulled across the boat. The tank itself would be moved by a block and tackle system that could be controlled from the cockpit. If the long axis of the tank were oriented fore and aft, I would think that you would roughly need a 25 gallon tank (roughly 200 lbs) to equal the righting moment of the original keel. The tank and trolley could be mounted high enough that it can clear the top of the centerboard trunk. Center-line water ballast tanks do almost nothing useful unless the boat has a huge amount of form stability which this boat does not. I would forget about adding a center-line water tank. I might consider building a deep draft centerboard that had maybe a 100 lb lead shoe, but I am not sure that is even necessary.

To tack, the traveler would be dropped to stand the boat up, and then the tank would be lowered to the center-line of the boat. The boat would then be tacked and settled in. Once settled in the tank would get pulled to windward in much the same way you pull up the traveler after a tack. Lastly the sail plan gets fully loaded up. Its probably a 30 second tack vs a 15 second tack.

A boat this light could be rowed in much the same way that a Dovekie is rowed. The only downside of this particular boat for a raid boat is that the rig is not easy to step and un-step, and also is longer than the boat so does not stow neatly. On the flip side, this is an easy rig to sail short-handed and there is plenty of sail area. I might be tempted to turbo the boat by perhaps rigging running backstays, and go to a square head mainsail and a masthead chute.

Whatever you do, you will probably want to add additional internal framing to offset the strains of increasing the stability of the boat and the spot loads of the water tank trolley and its supports.

Jus' say'n,
Jeff

 

[Jeff_H]

By the way, if properly configured the tank is not filled and emptied with a pump, but by gravity. This takes a little courage and skill since you seriously heel the boat to fill or empty the tank, but the idea is that there is a very large fill (probably 2") and vent on the tank. The fill is at the bottom center of the tank and the vent is at the top. The fill goes to a seacock on the centerline of the hull and has plenty of hose so the tank can be move across the boat with the hose attached. To fill the tank, the tank is lowered to leeward and the boat, the seacock opened and the boat heeled to leeward enough that the tank is below the waterline (i.e. rail almost in the water. As the tank fills the boat will heel more to leeward. Once the tank is full, the seacock and vent is is closed and the boat tacked or the tank pulled to weather.

To empty the tank, the tank is pulled to weather and the seacock and vent opened. As the tank empties the boat will heel more helping it drain.

Jeff

 

[Jeff_H]

Thanks Jeff,

That brought some concepts into focus for me. The pulley and the rail concept reminds me a little bit of a type of boat I have read about but never seen called sandbag schooners, or something like that.

It seems to me, that the tank trolley concept could be used together with the swing keel for even greater stability.

You have given me a starting point for further research. It seems to me, the logical steps, would be pay my dollar and try sailing the boat as is, see how the keel repair stands up, try beaching the boat (possibly with the assistance of a big anchor and 12 volt winch) and see if the weight is manageable with the swing keel.

Then figure out where to go from there.

You are referring to Sandbaggers. Mystic Seaport Museum has the last remaining original sandbagger 'Annie'. https://www.google.com/search?rlz=1....3...2921.5767..6079...0.0..0.100.704.11j1......0....1..gws-wiz-img._-WUp0pt4Is

Sandbaggers were 19th century race boats that were raced by local watermen. They were a big deal in their day. They were not schooners but were sloop rigged and based on the oystering boats of lower New York Harbor. These were very serious race boats in that they were dry sailed and had bottom paint that was graphite rubbed into varnish and then burnished for speed. They carried a scary amount of sail area with their boom and bowsprit extending the overall length of the boat by sometimes as much as 2 or more times the length of the hull. These boats were handled by large crews chosen in large part for their strength. The name 'sandbagger' came from the fact that every time they tacked dozens of 50 lb. bags of sand were physically picked up and moved across the boat to keep the boat on its feet.

In their heyday, sandbag races were widely followed. Working class people would rent livery whitehalls and row out to watch the races. Although they were primarily a New York Harbor phenomena, across the country the results were bet on, and race action and results were literally telegraphed across the country and quickly published in 'extras' (abbreviated copies of newspapers issued to cover breaking news). Major races were followed as closely as the Kentucky Derby or World Series. Its a bit like way that the French follow offshore racing in the Mini Transat, Figaro's and Class 40 race boats today.

Jeff

 

[Jeff_H]

Don't some water ballast boats use gravity to drain the water from one side to another?

The term water ballast applies to two different types of ballasting systems. In one case there is a tank that is located low in the boat on or near the centerline of the boat, and which is filled in seawater and remains filled whenever the boat is in the water. Those are filled by gravity, and some are emptied by pumps and others by allowing the water to drain as the boat is hauled out of the water.

The other type of water ballast is movable. Movable ballast of any type is not permitted under most racing rules but is permitted under a variety if 'open rules' and on some versions of the old VOR rules. That type of water ballast either uses movable tanks or else tanks that are located on either side of the boat with the water being moved from one tank to the other. Early in the days of open class boats with movable water ballast, the water was transferred by having huge pipes and valves and the water was transferred from the windward tank to the leeward tank by gravity before a tack or jibe. It was a pretty slow way to shift the water, but when you are crossing an ocean or going non-stop around the world, who cares about waiting 10 extra minutes to tack. I believe the newer boats use pumps but I do not know whether these use stored energy or are hand cranked.

Movable water ballast is a nice thing to have. My boat was designed to be raced with a crew of 8 to 10 people. It has two 40 gallon water tanks, one on each side of the boat under the settees. They are connected by 2" water pipes that go to a manifold under the cabin sole. A previous owner mentioned only carrying 40 gallons when he was making longer distance passages and transferring the water from one tank to the other when he had a long beat (days not hours). I have tried that at times and its amazing how much it helps flatten the boat to only have the windward tank full.

Jeff

 

[Jeff_H]

It looks like the J 121 uses a gravity feed system to change the ballast during a tack:
Boat Review: J/121

Can you imagine getting caught in a gusty wind shift and doing an accidental tack or jibe and ending up overpowered with 800 lbs of ballast on the wrong side of the boat?!?!?

Typically these systems are designed so that the impact of one tank being full or the other is not extremely noticeable or at least not dangerous. The open class boats have a limit on how much the boat can be heeled when all of the ballast and the canting keel is on one side of the boat.

I often cruise with only one tank full and I hardly notice the 40 gallons except that I point better when that tank is to windward vs leeward in a strong breeze. Of course the J-121 has a lot more water and a lot more sail area.

Jeff

 

[Jeff_H]

It seems to me, the Cal 20 and the Cal 21 are the same boat, with the main difference being, the Cal 20 has a 900 pound fixed keel and the Cal 21 has a 360 pound swing keel.

The Cal 20 is a completely different hull form than the Cal 21. The Cal 21 has a finer bow and flatter sections aft than the Cal 20. The Cal 20 is a close cousin to the ubiquitous Cal 25 and both were designed to the original MORC rule. The Cal 21 was a later design that anticipated some of the changes that were starting to take place at the time.

If the SA/D is correct, and you wanted to 'turbo' the boat, I would minimally want to add a traveler just forward of the tiller, a high purchase cascading vang, and an efficient backstay adjuster run to within reach of the traveler from either side of the boat. If you start buying sails, I would minimally want a mainsail with a large roach (and masthead flicker for the backstay) or better yet a square head, and if the SA/D is correct, (and I am suspicious that it is not correct), I would add a laminate 110% jib with battens made with a full luff (essentially the leading edge of a #1 genoa) when the backstay is eased that can be flattened with halyard and backstay tension when the breeze comes up. If you want to go crazy on this, I would try to find a used J-22 mast and set the boat up with a prod for a masthead assym chute as well as a 'tweener'.

If you decide to do the movable ballast tank I would be glad to suggest details (i.e. use a pre-made poly tank with the long axis fore and aft, skate board wheels for the trolley, aluminum channel for the hold down mechanism, continuous line for the trolley control lines with hexratchet blocks both ways and pieces of old foam mattress material to prevent the tank crashing and so on)

Jeff

 

[Jeff_H]

I see what you mean about the hull shape when I hold images up side by side.

I very likely will have some questions about how to power up the sail plan. Although the current owner has already purchased a new Cal 21 mast for the boat that comes with it, so I may stick with that.

I would suggest using the Cal 21 mast as long as you do not need to obtain any new sails. But if you do need new sails and you you decide to 'turbo' the boat, then it might be prudent to at least do a quick search for a J-22 mast since it is tapered and has a controlled bend pattern. It should also give you a bit more sail area.

Jeff

 

[Jeff_H]

First go, I went off sailboat data.

Then I found a metrics calculator on line and plugged the numbers in, using 1100 lb displacement and sail areas taken off sailrite. It does seem like the SA/D is correct using: SA/Displacement in cubic feet)^2/3.

100 sq ft main + 95 sq ft 117% working job comes out to 29 and change.

100 sq ft main + 115 sq ft 130% genoa 32 and change.

Using zedboys idea of adding my weight and say a weeks worth of rations it does drop to a practical SA/D of 24.9 with working jib.

If I am 2 up with a weeks worth of rations it drops even further to 21.9 with working jib.

At least those are the numbers the calculator are feeding me.

A few quick comments:
I looked over the numbers myself and the SA/D of 29 actually seems to be correct. That is based on a 98 square foot mainsail and a 98 square foot 100% fore triangle.

Its important to understand that properly calculated SA/D is based on the dry weight of the boat (tanks and storage empty but with its normal operating equipment on board), the mainsail triangle without roach, and the 100% foretriangle. You would never calculate an SA/D using the area of the boat's genoas, mainsail roach, or with the full load weight since the idea behind SA/D is to have a non-dimensional apples to apples benchmark. It really is meaningless to compare an SA/D based on the Displacement for a fully loaded boat or the sail area using a value that included the extra area of a huge genoa or the roach on the mainsail since the other boats that you are comparing with are not calculating their SA/D in the same configuration.

Calculated using dry weight and 100% foretriangle, it takes an SA/D that is to around 22 to 24 to have decent light air performance without needing large overlap headsails, but that assumes that you use a spinnaker on deep reaches. With that in mind, building out your Cal 21, your largest jib would probably only be a 110% with a full roach (which would be a great set up if you switched to slightly swept back spreaders and moved the shrouds slightly aft.) This minimally overlapping jib will be easier to handle and also can be reefed and still have a decent shape. On a boat this size, I would think that you could use a hank-on jib and reef with a jib Cunningham.

Similarly from a design standpoint, there is an assumption that a fully loaded a boat will have a cargo carrying capacity for gear, consumables and crew weight that is around 20-30% of its dry weight available. As it turns out, lighter boats for their length (low L/D) tend to tolerate carrying a larger percentage of their dry weight without noticing it than so called heavier displacement boats do. This occurs because lower L/D boats typically have a proportionately larger water plane relative to their displacement.

I suppose that you can also include a bin on the trolley for your heavier groceries, but moving 250 lbs of water is hard enough without adding more weight.

Jeff

 

[Jeff_H]

Eh, agreed it makes the numbers hard to compare apples-to-apples, but I see SA/Ds calculated based on main roach and big headsails all the time - usually of course on the ad copy!. And in fairness a boat meant to sail with a ~135% genny shouldn't either be directly compared to a boat meant to sail with a tiny frac jib.

This is the real point. Of course you should race your big keelboat tanks empty and tools/junk out of lockers. And of course on a boat with a big racing crew the numbers will change. But your fundamental understanding of the boat at (at least) a few tons displacement is much less affected by whether you are aboard or not.

But the SA/D numbers on a half-ton-or-less (maybe much less!) centerboard dinghy or cat are so radically wrong without adding the influence of crew that it's just criminal. There is such an insane difference between 29 empty, and 24 with crew, that only one gives you an accurate picture of what the performance will be like - and much more so on a cat where the number can drop from 60 to 30....

I don't know where you see "SA/Ds calculated based on main roach and big headsails all the time - usually of course on the ad copy!." because most magazines and boat builders use the designers numbers which use the conventions for calculating these things, and with computer aided design, the dry weight displacement numbers are much more accurate these days. The only company that I know of that used an inflated sail areas was Island Packet, and they were routinely criticized in the sailing press for doing that.

But getting back to the issue at hand, any of these non-dimensional surrogate formulas are of limited utility except as a rough thumbnail method of comparing like to like. You would not use these numbers to compare a two man dinghy to an offshore cruiser or even to compare a one man dinghy to a two man dinghy. Trying to distort the numbers by adding other factors makes them useless, because then you need to go through a much more detailed analysis to find meaning in the numbers and frankly it is pretty much a worthless exercise if you are comparing two similar boats which is all that they are intended to do. To explain the reason that I say this consider for example a two person crew comparing a couple of two person dinghies. That would have the same crew weight and gear weight sailing on either of the boats. The conventional manner of calculating the non-dimensional surrogate formulas would provide useful but incomplete information.

The reason that I say that the information is incomplete is that these numbers cannot provide anything beyond a very superficial snapshot. Take SA/D- in that case it does not include any information about the drag of the boat. Displacement is in theory standing in as a surrogate for drag, but displacement alone does not really say much about the stability of the boat and therefore its ability to carry its sail plan in a breeze, or drag due to wetted surface, its air to water interface condition (i.e. induced drag due to wave action), immersion inches, or the boat's ability to plane or operate in semi-displacement mode.

Really evaluating any given boat, requires a more detailed analysis than these kinds of surrogate formulas are able to produce. Distorting them from the norm, may seem like some kind of a more accurate analysis method, but because of the above, doing so does really does not provide any reliable basis for comparison.

Jeff