Catboat across the Atlantic? (16')

As an exercise, I am thinking about designing a series of boats using free-standing rigs. They will have modern hull forms and fully-battened sails. They are being designed for building in strip-plank/cold molded.
8' pram that will be a yacht tender (to the 24/32/40).
16' catboat daysailor/minicruiser.
24' catboat single-handed cruiser.
32 cat-ketch single/double-handed cruiser.
40' cat-ketch family cruiser.

I'm currently thinking about the 16' catboat. You see, the "kicker" is that I'd like this to be something a competant sailor could cross the Atlantic in. Not something he should cross in, but could. As in, if I build this model I'd sail it across the Atlantic to show the seaworthiness of the design, even though it's intended for coastal use.

This brings me to a few questions:
What was it about traditional catboats that caused the severe weather helm once the wind picked up? Was it soley the large, unbalanced, low-aspect rudder, partly a function of the rig, or partly a function of the wide hull shape when heeled?
Is 8' too wide? Most other catboats I see in this size range have an 8' beam. I could likely go with a 7' beam, but would it help? Should the maximum beam be located at the middle of the boat, or a little further aft as is typical on other modern boats for a better turn of speed?
Ballast? I know the wide beam helps with a shallow draft and stability, but would some ballast be a wise idea? Perhaps water-ballast or a ballasted center/dagger board?
Do you think a cat-rigged boat has any specific disadvantages over other rig?
Do you think a relatively wide, shallow hull has any specific disadvantages over other hull designs in this size?

I'm sure I'll think of other questions, or perhaps you'll think of them for me?

 

Traditional catboats have a very long boom. On a reach or run the sail area will be far out to the lee side. With two sails you can split the sail area when running.

 

Catboats are a joy to behold and very pleasant to use. They are pleasant to use only in good weather and entirely unsuited for big water and big weather.

Catboats have very long booms that will become a disaster in rough seas. The boat heels, the end of the boom goes in the water, the boat trips, the occupants drown, etc..

There are some good arguments against wide boats at sea.

Going to sea with a huge monorig is flirting with destiny. You need to have sails that are divided into smaller pieces to make them manageable and to allow some freedom to balance the rig to the weather at hand.

As soon as I write this, some catboat afficianados will protest and regale us with tales of catboat safety and seaworthiness. O.K. they can survive some weather in Casco Bay, but the North Atlantic is a whole other ball game. On a good day you could sail from Miami across the gulf strem to Bimini. On a bad day with a northeaster; pray fervently.

Gene

 

Swing the cat rig

I posted a reply in this old thread about the "swing rig" a kind of cat rig.

http://boatdesign.net/forums/showthread.php?t=6493

 

Gene, I agree with you regarding traditional catboats.
A cat rig on another kind of hull is something else.
But, then it's not a catboat, is it?

 

I'm thinking more along the lines of the Nonsuch style boats. They have a cat rig, however using a wishbone keeps the boom up high and out of the water. The ballasted keel helps keep the boat upright. They do still have a wide hull shape and wide transom, and are considered coastal cruisers, I believe.

There are a few reasons I'd like to keep it single-masted:
1) Simplicity. Half as many lines to pull, half as much hardware to maintain.
2) Accomodations. Nothing like another mast sticking through the cabin (or middle of the cockpit) to complicate arrangements.
3) It is intended to be a coastal-sailing dayboat/weekender. Just a seaworthy one. There have been a few daysailers in this size range that have crossed the Atlantic before the record books stopped accepting new attempts after a 6' boat made the crossing....

I'm currently leaning towards a dagger-board design with a bulb on the end of the board for ballast...

 

That may work

 

For inspiration you might look at the Freedom 25. Compared to traditional catboats, it has a higher aspect ratio rig with a shorter boom, a less forward mast position, and a more conventional hull shape. This should make it more balanced, especially under shortened sail.

 

As Seaspark said earlier. You need to check out the Van de Stadt swing rig. It's only a subtle modification, but eliminates the problems with cat rig whilst keeping all it's advantages.

www.stadtdesign.com/products/SwingRigIntro.htm

 

SF 24:

I happen to have a copy of Chappell's 'American Small Sailing Craft' and I just got done reading what it had about 'Cat boats'. It also has a lines drawing of what chappell considered to be a typical example of the type. As far as I can scale, it is twenty feet long, eight feet wide and displaces roughly 4,000 lbs.
Its sail plan has approximately 370 square feet.

This gives it a D/L of about 331 and an S/D of about 23.

The main reason for a cat boats heavy helm is its relatively wide beam combined with its asymetrical plan form. As the boat heels, the bow is forced downward, causing a bigger bow wave which is, of course bigger on the leeward side than on the windward side, which pushes the bow up wind.

The cure for this is early reefing.

The big problem with a boat type such as this on a long voyage is that it has poor course keeping charactaristics. Instead of a few hour commute to the fishing grounds, with somebody always at the helm, it has to sail many hours a day with the helm unattended. Joshua Slocum's famous 'Spray' was able to do this despite the fact that it had a similer beam length ratio to a typical cat boat (0.40). 'Spray's' secret was her very full bows, her long keel, which sloped upward, and her 'sloop' rig. Nothing like a cat boat.

Your short, deep, bulbed, keel is a step in the right direction. With a rudder of similar proportions, it should be much easier to steer. Even when pressed. You might be able to get an electric auto pilot to work on it for this reason.
I would suggest a beam more in the neighborhood of 6 ft and an S/D more in the neighborhood of 15. That way, the boom can be shortened so it doesn't go the usual 20% of its length past the transom. I would stick with the gaff rig, though. Or, failing that, go with a ballanced lug rig. With both rigs, the horizontal Center of Area does not change much as the sail is reefed. Much unlike a 'jib headed' (triangular) rig. This is crucial for maintaining reasonable ballance under most conditions with just one sail.

My guestimation is that your boat will displace, all up, around 2100 lbs and have a sail area of around 160 sf. With the bulbed keel, the ballast ration can be cut quite drasticly. You may be able to get away with as little as 500 lbs and still have good stability. Just make sure the keel foil is strong enough.

Best of luck.

Bob

 

I suppose I should have mentioned that I intend to use a freestanding spar with wishbone (or at least half-wishbone) and a square-top sail.

or...

Another idea I just had, is use of a rig like an Escape dingy. A rotating mast that is essentially a giant roller-furler with a seperate deck-mounted boom. This would require the use of an unbattened hollow-leech sail (just like the Escape uses). However, that would be acceptable if it was only for use on the "offshore" boat, and the "coastal" version got the afore-mentioned wishbone & square-top.

 

G'day,

I have grave doubts about crossing oceans in little boats, and even graver ones about the ocean being the North Atlantic. However, do a bunch of stormy miles before you leave, fix any problems that arise and you will have no trouble.

I have no doubt at all about unstayed rigs. They are safer, lighter, less weight aloft, easier to use and can be cheaper than stayed alloy ones. I would not recommend reefing around the mast for weight and windage aloft reasons. Wishbone booms are great, but the end is usually the same height as a conventional boom, so they still drag in the water. A boom vang, a short boom or a boom angled upwards are the solutions.

If sail balance is a problem (not sure it will be), you could look at a ketch or yawl configuration. You could also use a jib if the rig was designed for it.

regards,

Rob

 

Usually I consider such endevours to fit into the stunt catagory. I feel you should have the finances lined up to pay for your own rescue (if in range). That said, my neighbor Robert Manry, when I was a child in the Cleveland, OH area, made a crossing of the N. Atlantic in a 13 foot Old Town sailboat that he had fitted a cuddy cabin to.

But if we do not want national & these days, international, goverments dictateing what we can, and cannot do on the water, we should carefully consider how such attempts effect our fellow boaters.

Just my two cents.

Tim

 

Might be time to re-think Uni-rig 'catboats.' Wyliecats are regularly raced off shore. Simple, reliable, user-friendly and fast...

 

Hansen, those are gorgeous boats. Thanks for the reply.