Minimum TWA for cats

[django37]

Of course such keels perform different on the wind.

[Chuck Hawley]

My only experience has been with chartered (Moorings) 46' and 48' cats in the BVI and Croatia. In relatively flat water, our tacking angle appeared to be around 110 to 120 degrees on the chartplotter, so this included leeway. Since I generally sail relatively efficient monohulls, I was horrified that I was tacking through such a large angle on the cat.

Until I read this thread, that is!

Chuck

[HBrew]

My preference is to sail about 50 degrees TWA. If I go higher than this I lose a lot of speed and leeway becomes significant. I have daggerboards.

It’s not a great point of sail especially if there are significant waves slowing you down, but sometimes it’s the only option other than motoring.

[SailingSisu]

Our Leopard 45 sails about 40% of true wind speed at 50 TWA. the problem is the cross swell. If the cross swell in the first quarter is choppy and matches the boat length, then it gets unpleasant. We often goes as close as 38 TWA when the wind is 25 or higher and still do around 4-6kts,depending on that dreadful cross swell. In flat waters close to the coast, we are very comfy, it is the long 14 day voyages where the ocean gets confused with a wind shift, which is our nemesis.
The 3m waves from the 25kts wind would not bother us because of our relative TWA, but it depends on that 1m cross swell. We have a 0.8m bridge clearance, which with the stepped hull design, helps to minimize slamming. So, our TWA depends very much on the cross swell rather than the close as possible point of sail.
It is just not a happy place for a very buoyant cat to sail into the waves bow on. Monohulls kind of pierce through the waves, very wet experience, while bouncy cats rarely have water over the bow.
Agree, cats do not point well, but buoyant cats do not want to go fast into big swells....it is bouncy as hell😅

[Montanan]

Originally Posted by mikedefieslife

Here’s an example of an old mini keel cat with low windage. Upwind AWA of 60 will result in best speed, about 7knts in 20knts of wind. TWA is more like 80 sometimes 90. In a recent sail going into 30knts of true wind my crew was shocked to find that tacking was actually resulting in us going backwards.

Aftwards is a form of progress.

Albeit, always rather worrisome when trying to move away from a lee shore, kind of like an odd form of lying hove to. On the upside one doesn't have to worry much about arriving early at your destination, or perhaps to arrive at all.

[Dave_S]

Originally Posted by Sand crab

44CC and Dave S, do your boats have keels?
And Django, how did you get more sail area? Also could you tell us the price on that carbon sail?



I sure would like to see some stats from the daggerboard cats like Outremer and Catana. And Maine Cat, too.

No keels, dagger boards and outboards that lift clear of the water flow.

[sailingchiro]

Have a big roach kevlar mainsail that points much better than dacron. WE can get pretty close to wind but find we fall off speed pretty quick and a monohull will fall off less. We can point in the apparent in the 30's but slow. If less than 45 degrees, we start the engines. Yes, we are lazy.
Now, broad reaching from 18-25 knots. We are having fun.
Polar diagrams with standard sails are good comparisons.

[44'cruisingcat]

Originally Posted by Chuck Hawley

My only experience has been with chartered (Moorings) 46' and 48' cats in the BVI and Croatia. In relatively flat water, our tacking angle appeared to be around 110 to 120 degrees on the chartplotter, so this included leeway. Since I generally sail relatively efficient monohulls, I was horrified that I was tacking through such a large angle on the cat.

Until I read this thread, that is!

Chuck

Even the AC 72s tacked through around 100 degrees. And NOTHING sails to windward faster, in VMG terms. Boatspeed increases the difference between AWA and TWA.

[mikedefieslife]

Originally Posted by Montanan

Aftwards is a form of progress.



Albeit, always rather worrisome when trying to move away from a lee shore, kind of like an odd form of lying hove to. On the upside one doesn't have to worry much about arriving early at your destination, or perhaps to arrive at all.

To be fair the genoa was deeply reefed and so had no shape for upwind work. The main is obviously stretched out as it luffs on anything approaching 55-60twa.

New sails on the way should hopefully improve things.

[billyehh]

I must admit my sails are old on my Voyage 380, but they still have reasonable shape. I noticed that everyone is talking about sailing or motoring. I have found that motor sailing provides 3 advantages when going upwind. This is usually using one engine at 1600 to 1900 rpm.
1. It increases the speed by 1 to 2 knots.
2. It increases the angle into the wind by 5 to 10 degrees.
3. It decreases the motion in heavier seas and stronger winds.
This give a more comfortable ride allows you to get to your destination faster. I would prefer to sail, but it has worked out to be a reasonable compromise, especially in the breezy Eastern Caribbean.

[3cdad]

Originally Posted by SailingSisu

Our Leopard 45 sails about 40% of true wind speed at 50 TWA. the problem is the cross swell. If the cross swell in the first quarter is choppy and matches the boat length, then it gets unpleasant. We often goes as close as 38 TWA when the wind is 25 or higher and still do around 4-6kts,depending on that dreadful cross swell. In flat waters close to the coast, we are very comfy, it is the long 14 day voyages where the ocean gets confused with a wind shift, which is our nemesis.
The 3m waves from the 25kts wind would not bother us because of our relative TWA, but it depends on that 1m cross swell. We have a 0.8m bridge clearance, which with the stepped hull design, helps to minimize slamming. So, our TWA depends very much on the cross swell rather than the close as possible point of sail.
It is just not a happy place for a very buoyant cat to sail into the waves bow on. Monohulls kind of pierce through the waves, very wet experience, while bouncy cats rarely have water over the bow.
Agree, cats do not point well, but buoyant cats do not want to go fast into big swells....it is bouncy as hell😅

So, in with 15 knots of TWS, your Leopard 45 can sail at 6 knots at a 50 TWA? That calculates out to a 36 degree AWA. And at 25 knots of TWS, you can do 5 knots at a 38 TWA? That calculates out to 32 degree AWA. That's impressive for a production cat. I wasn't able to come anywhere close to that on a 45' charter Lagoon.

[Perfect Ride]

On our 44' cat we normally run 30-40 AWA depending on sea state, wind speed and if hand steering or on auto pilot. Of course TWA changes with SOG.

[fxykty]

Our first generation Outremer 55L with 10 year old hydranet sails (cloth still in great condition, but definitely stretched out) sails upwind 32-36 degrees AWA for best VMG, with tacking angle around 100-105 degrees true. We’re fully powered up at around 12 knots true, so up to that point we use both daggerboards to minimise leeway; after that we’re 8 knots plus boat speed and are fine with just one board.

In flat water we can squeeze up a bit, but for the same VMG I’d rather head off and have more boatspeed - that just feels more fun.

Thin hulls mean that we slice through waves, so wind waves and swells do not slow us down or knock us about very much. Length is definitely your friend going upwind in not flat water.

Recently we sailed from South Minerva Reef to Tongatapu - 411 nm in 55 hours almost directly upwind into 13-22 knots of trade winds and 2-3m short period swells. The straight line distance is 286 nm. Boat speed average 7.5 knots, VMG (based on the straight line distance) 5.2 knots. Full jib and single or double reefed main. We spent 60% of our time on starboard tack. Our crew, who were all catamaran novices, were thrilled with the smooth ride and ability to leave glasses and mugs on tables.

I’d love new sails, but there’s no real reason to get rid of the current sails until the sail material deteriorates such that they risk ripping. We are getting them restitched later this year and will evaluate their remaining life then. The hydranet fabric is incredibly long lasting, albeit stretched.

[Factor]

Originally Posted by Soma

On a Gunboat we can sail up to about 27-28 AWA. Best polar performance is somewhere between 29-32 AWA. That translates to about 44-48 TWA. Add in 2-3 degrees of leeway and it's hard to achieve 90 degree tacking angle. In light to medium you'll tack through about 100 degrees (max). Angles close up as wind speed increases. Boat speed is 11-14, maxing out at about while 15 hull flying upwind.

On my F40 we sail a little faster and lower. 14-16 for boat speed and 105 degree tacking angle.

On an ORMA I've sailed about 16-18 upwind, tacking angles are about 105-110.

In my experience, no mini keel boat can sail upwind faster than they can motor (VMG).

You need to get more experience. There are some mini keel boats that will certainly sail to windward faster than they motor. The so called big three are not amongst them.

[shipofools]

I typically tack through 80 degrees at maximum Vmg in most conditions. Single daggerboard. Shuttlecat 32. cheers