Catamaran tacking angles , really that bad???

[double u]

who said "can't be done"?
& your boats performance would be WAY better than the average cruisers!

[double u]

...& you are not meaning to deny the existence of tradewind-currents, do you?
(btw: "beating" to me means straight upwind, straight.

[charliehows]

the good old 'how long is a piece of string' question; some cats (and tri's) have truly awful upwind sailing characteristics (I know, i had a tri that could barely manage 85* on a header, easier to anchor up and wait for a windchange...) I test drove a neighbours cat and it was even worse. The problem is; how do you know if a specific boat has been well designed and fitted for good sailing characteristics? Well, when I was younger, you wouldnt buy a boat without a test sail beforehand and I dont think theres an app to replace that process. Basically the same old caveat emptor applies.
generally catamarans can be designed to carve up very close to dead ahead but only if that is their only design criterion; as soon as you start adding comfort that goes out the window very quickly and you end up with the puddleducks commonly seen floundering around the harbour most days.

[wingssail]

Originally Posted by fxykty

Well, we beat into E and ENE trade winds for a couple of days from South Minerva Reef to Tongatapu, anchoring off Big Mama’s Yacht Club (and snuck ashore that night before clearing in the next day for well-earned beers and burgers). It was pretty much straight upwind in 15-20 knots of trade wind with underlying 4m swell. Had the first reef in most of the time and both daggerboards down to deck level (3/4 deployed)

According to our log, 421 miles sailed vs 285 miles straight line in just under 2.5 days. We made two tacks and had an average boat speed of 7.5 knots and average VMG 5.1 knots. No “trade wind current” in evidence.

Cooked, exercised, slept, (made love), chatted, relaxed, stood watches, steered for fun, routine chores = life as usual, regardless of wind angle.

Can’t be done, yeah, right.

Attachment 225151

And our log pages for those interested in the underlying stats.

Attachment 225152
Attachment 225153
Attachment 225154

Pretty nice conditions (15-20kts, some nice shifts to play...) and good sailing. Your tacking angles don't look too bad (for a cat). Congrats for a nice job.

Anyone who can acquire a 55ft performance catamaran, and has the money to maintain and operate it, and the skills to sail it like that, could expect similar results in perfect conditions.

Some things to consider for the OP who is asking what kind of tacking angles he can expect.

[fxykty]

Originally Posted by wingssail

Pretty nice conditions (15-20kts, some nice shifts to play...) and good sailing. Your tacking angles don't look too bad (for a cat). Congrats for a nice job.



Anyone who can acquire a 55ft performance catamaran, and has the money to maintain and operate it, and the skills to sail it like that, could expect similar results in perfect conditions.



Some things to consider for the OP who is asking what kind of tacking angles he can expect.

Regarding tacking on shifts during long upwind routes, is it worth it?

The tacking itself is trivial, but the paying attention to the wind direction layered with watches and multiple crew (we had three for that passage) is not so easy.

Certainly reviewing the log, there were shifts of up to 30*. If we were racing, 5* is plenty. But cruising, when it’s oscillating fairly quickly?

[belizesailor]

Originally Posted by fxykty

Regarding tacking on shifts during long upwind routes, is it worth it?

The tacking itself is trivial, but the paying attention to the wind direction layered with watches and multiple crew (we had three for that passage) is not so easy.

Certainly reviewing the log, there were shifts of up to 30*. If we were racing, 5* is plenty. But cruising, when it’s oscillating fairly quickly?

Racing maybe, cruising no. I would not tack on a shift cruising unless it proved to be a significant and long lasting shift.

The typical cruising cat is not very nimble under sail and looses a LOT of way when tacking. Plus wide tacking angle. Not likely worth it.

By contrast if racing my Hobie 33 I might tack on even small/short duration shifts. Radically different boat.

[Joli]

Originally Posted by fxykty

Regarding tacking on shifts during long upwind routes, is it worth it?

The tacking itself is trivial, but the paying attention to the wind direction layered with watches and multiple crew (we had three for that passage) is not so easy.

Certainly reviewing the log, there were shifts of up to 30*. If we were racing, 5* is plenty. But cruising, when it’s oscillating fairly quickly?

When sailing distance you are much better off sailing the favored board rather then chasing shifts. The goal changes from seeking max vmg to sailing a favorable vmc while trying to making the best time up the ladder. It has to be understood that you will probably be lifted prior to the mark and fetch or you will be headed enough to allow you to change boards and be further up the ladder then being on the non favored board.

[wingssail]

Originally Posted by double u

...& you are not meaning to deny the existence of tradewind-currents, do you?
(btw: "beating" to me means straight upwind, straight.

I don't get this statement? Beating is tacking back and forth. Tack on tack, both boards, whatever. Sailing close hauled on one tack towards a destination is a "fetch". The only way a boat can sail straight upwind is motoring. It isn't beating, it isn't even sailing even if you have a mainsail up.

A lot of people motor upwind. Many will even motor when the course is a fetch. I've seen plenty motor down wind.

Then there are sailors.

[thinwater]

Originally Posted by double u

...(btw: "beating" to me means straight upwind, straight.

From OED:
To beat, as relating to sailing:

no object, with adverbial of direction Sail into the wind, following a zigzag course with repeated tacking.

‘we beat southward all that first day’

Nope, it does not imply "upwind, straight." Just wrong.

[wingssail]

Originally Posted by fxykty

Regarding tacking on shifts during long upwind routes, is it worth it?

The tacking itself is trivial, but the paying attention to the wind direction layered with watches and multiple crew (we had three for that passage) is not so easy.

Certainly reviewing the log, there were shifts of up to 30*. If we were racing, 5* is plenty. But cruising, when it’s oscillating fairly quickly?

In an oscillating breeze tacking on every shift maybe isn't worth it unless your crew are hard core racers who just do it out of habit.

Tacking on a persistent shift is very much worth it.

I noticed on your log that the shifts came pretty frequently and were, in fact oscillations. Sailing a close winded monohull with a #4 jib we might have tacked on them, at night, with only two on board, probably not.

Detecting the shifts is another matter. On our boat we sail by the numbers. We actually live by them, and every crew member soon learns to watch the big displays and note any significant wind shift (the owners expect it). So we rarely miss a shift.

One final thing I would mention. I wonder if the wind changes which were synchronized with your tacks on day 2 & 3 weren't really instrumentation artifacts? Your track doesn't seem to indicate any shifts. On our boat when the instruments are not calibrated well the instruments might say TWA60 on one tack and TWA90 on the other (or maybe a little less dramatic, but you get the idea.) As I am sure you know, accurate boat speed and wind speed is essential for accurate TWD calculations.

We are in the process of upgrading our B&G Hercules 390 to a Hercules 2000. Still not state of the art but much better calibration tools.

[fxykty]

Originally Posted by wingssail

In an oscillating breeze tacking on every shift maybe isn't worth it unless your crew are hard core racers who just do it out of habit.

Tacking on a persistent shift is very much worth it.

I noticed on your log that the shifts came pretty frequently and were, in fact oscillations. Sailing a close winded monohull with a #4 jib we might have tacked on them, at night, with only two on board, probably not.

Detecting the shifts is another matter. On our boat we sail by the numbers. We actually live by them, and every crew member soon learns to watch the big displays and note any significant wind shift (the owners expect it). So we rarely miss a shift.

One final thing I would mention. I wonder if the wind changes which were synchronized with your tacks on day 2 & 3 weren't really instrumentation artifacts? Your track doesn't seem to indicate any shifts. On our boat when the instruments are not calibrated well the instruments might say TWA60 on one tack and TWA90 on the other (or maybe a little less dramatic, but you get the idea.) As I am sure you know, accurate boat speed and wind speed is essential for accurate TWD calculations.

We are in the process of upgrading our B&G Hercules 390 to a Hercules 2000. Still not state of the art but much better calibration tools.

The track is zoomed out so doesn’t show the detail. If you check the logbook entries you can see our COG changes generally together with the shifts (2 hour interval of entries), between the tacks.

We have calibrated the wind instrument and it’s within about 3* apparent wind angle from one tack to the other. For apparent wind speed we’ve not done anything (is it even possible to calibrate apparent wind speed?). We have Raymarine instruments.

But true wind direction varies by a bunch of factors, including boat speed, whose calibration is rougher, and leeway, which isn’t captured by Heading (I believe TWS/TWD are calculated by STW/AWS/AWA and ignore COG/SOG). All those factors result in the true wind direction changes from tack to tack of 20-30*. That’s not enough of a big deal for us to bother getting anymore accurate, as long as the true wind speed calculation is close (and it seems to be).

[arsenelupiga]

Originally Posted by double u

...& you are not meaning to deny the existence of tradewind-currents, do you?
(btw: "beating" to me means straight upwind, straight.

yeah, we are not discussing wind shifts. this is directly against wind, calculated from COG on a second by second basis in excel inclusive of drift and current that is present in TW conditions based on literature and also i have measured it.

3 kn VMG and happy crew and boat going upwind - i am ok with it given the conditions.

With wind shifts we managed later above 5 kn, once i learned couple tricks. Will use 3 kn direct against wind as a planning number for passage making.

[wingssail]

Originally Posted by fxykty

The track is zoomed out so doesn’t show the detail. If you check the logbook entries you can see our COG changes generally together with the shifts (2 hour interval of entries), between the tacks.

We have calibrated the wind instrument and it’s within about 3* apparent wind angle from one tack to the other. For apparent wind speed we’ve not done anything (is it even possible to calibrate apparent wind speed?). We have Raymarine instruments.

But true wind direction varies by a bunch of factors, including boat speed, whose calibration is rougher, and leeway, which isn’t captured by Heading (I believe TWS/TWD are calculated by STW/AWS/AWA and ignore COG/SOG). All those factors result in the true wind direction changes from tack to tack of 20-30*. That’s not enough of a big deal for us to bother getting anymore accurate, as long as the true wind speed calculation is close (and it seems to be).

My experience is limited to B&G systems on various boats. Our own B&G 390 system is about 30 years old now, but still works pretty good. It does allow adjustments to apparent wind speed, but of course it is hard to obtain a base value to test against. We can, of course, do two direction motoring with minimum wind and get a sense that way of the accuracy of the apparent wind speed however it might not be linear in the upper wind ranges.

However, seeing a 20-30 degree shift in true wind direction on tacking would not be acceptable to me. Maybe we have some terminology confusion, my system does not refer to STW. But I have done some vector analysis of my boat trying to nail down the reason for a 5-10 TWD shift on tacking and I find it is very sensitive to boat and speed and wind speed, especially in the lower wind ranges. Over 15kts of wind it seems to work better.

But anyhow, that is why I want to upgrade my system to newer stuff, the accuracy and self calibration is better than on my old system.

None of this matters too much while cruising, in that case we have enough time to assess the actual wind direction and ignore the instrument artifacts and we are mostly interested in lifts and headers while on a tack, which is generally accurate. But in racing it would be nice to have accurate data.

[earthbm]

Here are real world monohull (towing a dinghy) tacking angles through a fjord, from

this video

.

[Tupaia]

Achieving 13NM by sailing 30NM approximates to a tacking angle of 64º or 128º between tacks.