Catboats...up and downsides?

[dancrane]

This is only a theory-query...nothing even on paper yet.

I know little about catboats, by which I mean cat-rigged boats, but I like their style and apparent simplicity.

I don't really know what defines them. Is a catboat's mast typically unstayed? (EDIT: I just noticed the forestay in the photo). Is that very difficult to engineer? How can an unstayed mast in a 20ft boat, be strong enough to carry 200+sq ft of sail?

My impression is that catboats are often wood, with wood masts...so the engineering that makes them possible, isn't new, and new materials might make retrofitting this pleasing rig to an old glassfibre boat, easier than crafting a new one from wood. Or, not.

To be honest I've been looking at a little old 19ft motorboat, with long shallow ballast keels and a tiny mast and sails for fun. It occurred to me that gaff rig might allow a much bigger sail area, kept low-aspect to match the shallow draft.

But I'd like to avoid increasing the length, such as a bowsprit would require to provide steering balance from headsails...so could a gaff catboat rig be drawn to keep the sail area low, and within the length on deck, as well as over the centre of lateral resistance?

If it influences anyone's answer, I had it in mind that the boat wouldn't be expected to make much (if any) upwind progress...

...she's basically a displacement motorboat anyway.

Thanks for any tips and thoughts.

 

[DownWest]

Cat rigs are called so because the mast is right up front in the 'Cats' Usually unstayed mast, though as in the photo, some have a stay or the halyard tied off forward.
I am in the finishing stages of a little cat yawl, with 'leg of mutton' rigs
I will see if a photo gets up of a similar boat.

The hull on mine is a bit longer and more flared. Rig is the same.

A very E coast US rig. The hulls are typicaly very beamy at half the length and usually big centreboards and barn door rudders with lots of weather helm.
Some are rigged with a jib, but not common.

There is a nice wooden one here, but made in Germany. Only 21ft but huge inside. Fixed shallow keel and inboard diesel. 10ft beam..

 

[DownWest]

To add: the US classic ones sound a bit of a handfull and need reefing early, otherwise the helm gets too heavy to handle.
Often the placing of the mast well forward was to keep the boat clear for working, but I don't know if that was the influence on the New England ones. Their Sharpies often had rigs with raked back masts for that reason. Bit like the Scottish Luggers.

To get your center of lateral resistance, cut out a cardboard pattern of the underwater profile of your intended boat. Ballance it on a ruler in the vertical plane i.e. perpendicular to the water line. When balanced the center is on that line. The centre of sail area should be about 10% ahead of that. Could be easier to keep to two short masts (gaff)and low centres of sail area to allow for the lack of roll resistance of the typical mobo?

 

[dancrane]

Lots of helpful stuff there, thanks DW. I like the style of the yawl you're completing.

It hadn't occurred to me that a cat-rigged boat might need a mizzen for steering balance, but it's a very pretty solution.

But did you mean that catboats are prone to weather helm, or lee helm? I would have expected a Bermudan-rigged catboat to turn off the wind rather than into it, given that most of its area is so far forward...isn't that the reason for adding a mizzen?

If so, I guess I needn't be concerned about a cat-rigged boat needing a bowsprit and headsails for balance, quite the opposite; although it might be different for a gaffer with the peak well aft.

Is there a danger of cat-rigged boats getting caught between stays when tacking, with no headsail to 'back', to bring her round?

I'll do some drawings to try to begin a plan...I'm still a bit in the dark. In truth I needn't worry much about weatherliness, because the hull-shape and keels of the boat I have in mind, won't reward subtle shaping of the sailplan - it'd be largely an offwind rig.

Thanks!

 

[DownWest]

With only a main and those big centre/boards and wide beam, they suffer from weather helm. If it was lee helm in a big gust, likely they would go over. Local friend built a gaffer and asked me to sail with him and give a bit of advice. It suffered from lee helm and it was a bit alarming. So I got the pencil and envelope out and did some rough maths. Then moved the mast back a bit. Now sails with a light helm with a bit of weather in a gust. You actually need some to 'feel' the effects of the wind. Long skinny boats, like the metre boats don't have much problem with this, but short fat ones do.
Don't forget that a lot of New England sailing is in relatively shallow water. I know a bit of the Chesapeak and running aground is very easy.. Less so further north, but c/boards are very popular.

The lack of a jib on catboats tends to limit their closewinded ability apart from the general design and gaff.

And, a comment on motor boats. Their rudders, esp if running in propwash, tend to be a bit small compared to a sailing boat of similar size. The restoration of a naval fast planing tender a while back on these pages was a case. Fine at speed, but very feeble at river speeds. Since it didn't have one when aquired as a wreck, I made a new one. Original was a flat plate on a 1" bronze stock. New one was 50% bigger and I wrapped SS sheet round the new SS stock to get a nice foil section. On the river tests, it was effective at docking speeds (ok at speed too, on a quiet bit of the river.. )

 

[Laminar Flow]

Re rudders: planing powerboats have relatively small rudders; a displacement MoBo will have one of about 5% of lateral plane (see Colvic Watson and one reason they do not sail well), a long keel sailing boat will have on of 8-9%, according to older sources (Skene's) up to and over 11%. Modern designs, keen to reduce wetted area, have proportionately less.

The original cat boat was designed for inshore fishing and, as many traditional fishing craft, were evolved for a particular type of fishing and to meet the conditions for a very specific area. That may or may not transfer well to other locations, see Dutch barge types. They became popular in New England as pleasure craft, because they were already there when the area was discovered for recreational activities. Sharpies were more common to the Southern States, the Gulf Coast and Florida.

Traditional cat boats are form stable and often have a length/beam ratio of 2 or, in smaller sizes, even more. The beam was carried all the way aft to a wide and often slightly submerged transom ( a bit like contemporary designs one could say). They can and do capsize and their wide beam causes impressive weather helm and huge rudder loads, not helped by a very long and shallow rudder. The off-centre leverage of the low aspect, single and large sail can induce a strong a inclination to broach when pressed hard on a run or broad reach. The masts were unstayed, as much for the simple reason that shrouds would have been rather useless with the mast up in the eye of the bows. However, they often would have had a headstay to support the weight of the long booms and gaff. A cat rig used on a hull not specifically designed for it, i.e. with sufficient buoyancy in the bows to absorb the significant pitching moment of a mast placed that far forward is a bad idea. This will cause the bows to dangerously undercut and be very wet and have a significantly negative impact on performance; Freedom Yachts managed to produce a couple of lemons in this respect.
During the freestanding mast craze we designed a schooner rig with unstayed profiled masts for a large boat. After talking to a number of mast builders and sail makers about the negative experiences with this type of mast placement we abandoned this in favour af a cutter rig.

 

[dancrane]

Cripes! That's fair warning, I think.

They certainly are very pretty, but I doubt I'd be smart to switch the shortcomings of the stumpy Bermudan rig aboard the boat I have in mind, for such wayward characteristics, in a hull that was never designed to be challenged by them.

Taking a long step back, I daresay I could cope with a standard bowsprit/gaff cutter instead, unless there's a better low-aspect rig?

Sadly that may be all there is to say about catboats, on this occasion. Many thanks for the pointers.

Time for a few good pics, and one really bad definition I found...

 

[Laminar Flow]

Cripes! That's fair warning, I think.

They certainly are very pretty, but I doubt I'd be smart to switch the shortcomings of the stumpy Bermudan rig aboard the boat I have in mind, for such wayward characteristics, in a hull that was never designed to be challenged by them.

Taking a long step back, I daresay I could cope with a standard bowsprit/gaff cutter instead, unless there's a better low-aspect rig?

Sadly that may be all there is to say about catboats, on this occasion. Many thanks for the pointers.

Time for a few good pics, and one really bad definition I found...

They are an inshore type of boat and as all your pictures show, there very little in the way of waves to cause much pitching. I have a book by the New England Cat Boat Association on the history of the type, relevant designers and some 70's interpretations. While there are lots of pictures in the book, there are none showing any kind of seas , just sayin'.

 

[Bajansailor]

A cat rig used on a hull not specifically designed for it, i.e. with sufficient buoyancy in the bows to absorb the significant pitching moment of a mast placed that far forward is a bad idea. This will cause the bows to dangerously undercut and be very wet and have a significantly negative impact on performance; Freedom Yachts managed to produce a couple of lemons in this respect.
During the freestanding mast craze we designed a schooner rig with unstayed profiled masts for a large boat. After talking to a number of mast builders and sail makers about the negative experiences with this type of mast placement we abandoned this in favour af a cutter rig.

Your post above reminded me of this article by Eric Sponberg where he describes the modifications he made to a 36' Freedom cat ketch.
You have to scroll down a bit, past the Wilbur sportsfishing boat.
https://www.ericwsponberg.com/wp-content/uploads/case-studies-in-redesign.pdf

 

[Laminar Flow]

Your post above reminded me of this article by Eric Sponberg where he describes the modifications he made to a 36' Freedom cat ketch.
You have to scroll down a bit, past the Wilbur sportsfishing boat.
https://www.ericwsponberg.com/wp-content/uploads/case-studies-in-redesign.pdf

Thank you, yes, I have read that article. It retrospectively confirmed our fears of placing a mast that far forward.

 

[DownWest]

Not seen that article, thanks.
When I used to do some stuff for a shipping company, the owner asked me to be their agent in the purchase of a Freedom 65/70, so I got chatting with them. But after the first one experienced some problems with the formast in a transat race, My lot went off the idea.

 

[Blueboatman]

Nigel Irens put the rig right up in the bow too, with a pointy top and battens, lovely sail shape . Possibly a bit lighter than a trad cat boat ?

Roxane & Romilly

Good lookers too ?

 

[Laminar Flow]

Nigel Irens put the rig right up in the bow too, with a pointy top and battens, lovely sail shape . Possibly a bit lighter than a trad cat boat ?

Roxane & Romilly

Good lookers too ?

Estuary and coastal boat of traditional design with a buoyant bow. and yes, very pretty.

I used to think that the Nonsuch cat boats, 26' to 36' were super too. Tons of space, modern underwater shape, easily handled rig, until I talked to a couple of owners who told me about their nasty broaching habits when pressed. The early aluminium masts had a high failure rate and nearly bankrupted the company.

 

[dunedin]

Ages back I was a sailing instructor at a US summer camp in the mid west. Sometimes I used to have to take kids out in a large cat rigged scow. It was quite impressive to look at, about 24 feet long with a huge mainsail. It was also a complete pig to sail, with twin heavy lee/centre boards to swap each tack, very heavy main sheet loads, running backstays to manage, and a skull cracking low boom.
Just the perfect boat to take 6-8 young children whose Dad’s mostly seemed to be lawyers.
It was kept on a mooring in a bay, and this was the big nightmare. Getting off the mooring was tricky, as no jib to back to get underway. Needed to heave mooring buoy from bow, round the mast and back along the side to get going.
Coming back when wind onshore was near Darwinism territory. Run downwind past buoy almost onto rocks, firm gybe (heaving the massive boom in to centreline, swapping running back stays, gybing then releasing mainsheet again) - then have one shot at shooting to windward to stop at the buoy. Too much speed and cant stop this very heavy beast - too little speed and get caught in irons, again with no jib to back to get sailing - so would drift back onto the rocks. All with learner children crew.

interesting, characterful, pretty - yes. Sensible sailing rig - NO !

PS. these barn door rudders are another nightmare of poor design - heavy loads and lose grip easily when heeled.

 

[Laminar Flow]

Ages back I was a sailing instructor at a US summer camp in the mid west. Sometimes I used to have to take kids out in a large cat rigged scow. It was quite impressive to look at, about 24 feet long with a huge mainsail. It was also a complete pig to sail, with twin heavy lee/centre boards to swap each tack, very heavy main sheet loads, running backstays to manage, and a skull cracking low boom.
Just the perfect boat to take 6-8 young children whose Dad’s mostly seemed to be lawyers.
It was kept on a mooring in a bay, and this was the big nightmare. Getting off the mooring was tricky, as no jib to back to get underway. Needed to heave mooring buoy from bow, round the mast and back along the side to get going.
Coming back when wind onshore was near Darwinism territory. Run downwind past buoy almost onto rocks, firm gybe (heaving the massive boom in to centreline, swapping running back stays, gybing then releasing mainsheet again) - then have one shot at shooting to windward to stop at the buoy. Too much speed and cant stop this very heavy beast - too little speed and get caught in irons, again with no jib to back to get sailing - so would drift back onto the rocks. All with learner children crew.

interesting, characterful, pretty - yes. Sensible sailing rig - NO !

PS. these barn door rudders are another nightmare of poor design - heavy loads and lose grip easily when heeled.

Thank you for that contribution.

Back in the day it was considered character building and (probably) an appropriate method for weeding out the weak. This was after all the era when (upper class) youngsters where sent off to sail around the world on a brigantine to test their mettle, such as on Cpt. Irvin Johnston's fine ship. I recently read about a reunion of these kids, now all in their golden years and captains of industry - best time of their lives, they said! I would have given a kidney and sold my Grandmothers into slavery, on both sides, if necessary, for that!

I'm sure, all your charges, unaware of your trials and tribulations with the beast, have fond memories as well.

 

[SkipperGW]

here's some more information about catboats…:

• > more about catboats
• https://www.catboats.org