What Is 'Light Wind Performance' Really?

[FSMike]

I got a few seconds of a boat under sail and a bunch of apparently unrelated stuff. Anyway, insamuch as a GPS does not give you speed through the water but rather speed over the ground I trust you compensated for the difference?
And also, we are talking about true wind not apparent wind, right?

[barnakiel]

Originally Posted by Paul L

By going for speed you are probably actually increasing your VMG, especially in light airs.

Paul L

Well, it depends. Basically, yes. Particularly though, we sail by the VMG in normal conditions. In light winds we still try to sail clear of laylines (buhahaha) but we turn the VMG thingy off and just try to sail comfortably towards the location where we hope to get better winds. So any VMG improvement is sort of like a by-product in the process of keeping her going, comfortably, towards a more windy spot.

b.

[dcstrng]

Originally Posted by Stillraining

Here ya go...Iv already learned the no pictures didn't happen gig...

I lived aboard an Irwin 42 Ketch for some years and although I don’t recall ever actually seeing 8kts (our gauges were inop most of the time), I do recall bumping up against it several times on time-distance with a stopwatch and wondered because that was a tenth or so above theoretical maximum – which is, I suppose, only theoretical… My conclusion was that the longish stern immersed under a good press of sail on a beam reach and then the LWL acted beyond its measured length of 35-feet or so, so I’m not terribly surprised… I recall one beautiful sail down the Bay with about 15-17kts of wind right on the beam – jenny up and the stern wave just boiling up behind… two-blocked the dinghy in the davits and it was still hitting the stern wave so we rigged a guy under it up to the mizzen runners… Those big ol’ Irwins might not point with the flyweights, but free `em up a bit and they were like a freight-train... theory or no theory…

[bobfnbw]

I think that when it comes to "light wind" you are talking about winds of 6 knots or less. Where most boats just won't move well without some specialized sails.
For me, that is just a good time to motor and charge my batteries!! Not to say that she won't move in that with a spiniker.. just that I haven't tried.

I used to live on Tampa bay with out Nor'sea 27 and almost every day was a light wind day. Just not good sailing wind there for us. We motored a lot.
Here on Corpus Christi bay, winds are seldom below 10 knots, and frequently over 15. So what one guy in a light air area worries about, here we don't have to think about it much.
But from what I have read, if you want to world cruise, be prepared for more light air days than heavy... so thats why I am increasing my fuel capacity !

Bob

[Roaring Girl]

For us, light airs definitely relates to whether we can keep moving at all without the engine. If we're moving at 1 knot we'll keep the engine off (unless trying to make a tide or something). That's why it once took us 47 hours to do the 140-odd miles from Mellila to Cartagena, but we saw some great wildlife!)

The main weapon is a 1000ft cruising chute, which goes up fairly easily and during the height of the season lives on the foredeck, so we're not lugging it up and down.

But it is very susceptible to swell, so if there's too much running we have to hand it and that's really when we end up with the engine on. Neither of us have ever raced under sail, and we have no particular inclination to, so we haven't any derring-do comparisons to make.

[Stillraining]

Originally Posted by FSMike

I got a few seconds of a boat under sail and a bunch of apparently unrelated stuff. Anyway, insamuch as a GPS does not give you speed through the water but rather speed over the ground I trust you compensated for the difference?
And also, we are talking about true wind not apparent wind, right?

If you mean compensate for current it was slack tide..but regardless we made hull speed both directions so it would make no difference..Right?

Am I missing something using the GPS as an accurate measure in that circumstance? I have no operable knot meter yet.

[s/v Jedi]

Okay, we normally have plenty wind here but I do recall one sail from Grenada to the Testigos in 2005. We were on a broad reach with 7 knots of wind and averaged 5 knots boat speed under working sails alone. That is the sail plan that can be used up to 25 knots without reefing.

A friend had a trimaran that would do more than 10 knots on a reach with only 7 knots of wind, now that is what I call light weather performance ;-)
I doubt that we could ever do hull speed with 7 knots wind, not even with both spinnakers up.

cheers,
Nick.

[FSMike]

Stillraining -
Nope, you're not missing anything. Sounds like you've got a fast boat.
Enjoy,
Mike

[DaveOnCudjoe]

StillRaining, My F-31 tri will do windspeed down to about 2knts. I carry a 1000sqft screecher that I can carry up to a nearly close reach and a 1000sqft asy spin up to about a beam reach. Might be able to coax boat speed below 2knts but it isn't worth the trouble. Boom must be held down to keep the main flat or you spill too much drive in light puffy conditions. Dave

[Joli]

You really learn a lot about sail trim if you race. The fact that you are stuck out there is a big motivator to learn how to make the boat move when the breeze is light and of course the desire to win.

Light air and chop: sag off the rig, draft forward, twist, deeper.

Light air flat water: tighter rig, draft aft, close leach, flatter.

Speed is: flatter, draft aft, closed leach. Power is: deeper fuller, draft forward, twist.

[Stillraining]

Nice concise breakdown Joli...Thanks.

[Stillraining]

Originally Posted by FSMike

Stillraining -
Nope, you're not missing anything. Sounds like you've got a fast boat.
Enjoy,
Mike

Well I don't know about that..she seems powerful enough and easily driven like I said in 10 to 12..and also carries a lot of momentum. But I have little to compare her to... she is the largest blow boat I have ever been on and I jumped from 20' to 40' with a 35 year sail less gap in between to boot...so what do I know..

[swagman]

For me light airs are anything under 8 knots true, medium up to 18, strong above that.

The reason we chose a cruiser with good light air perrformance is because most of the wind we find following regular routes are light airs.

With a 200% code 0 can make 7 knots to windward in 7 knots of true wnd. On flat water suspect we would go faster.

Hope this helps.

JOHN

[Stillraining]

Dang..a code 0... that sounds like fun in 20 knots..

Planning on buying a cheap Symmetrical at some point.. so we will see what she will do in those 3 to 4 knot zephyrs you all are talking about..I'm not expecting great performance but I am also in the camp of if were moving forward the engine stays off crowd.

A code 0 might just be a good sail to have around here as well for upwind dead air days which we have allot of in the summer around here.

[swagman]

Originally Posted by Stillraining

Dang..a code 0... that sounds like fun in 20 knots..

Planning on buying a cheap Symmetrical at some point.. so we will see what she will do in those 3 to 4 knot zephyrs you all are talking about..I'm not expecting great performance but I am also in the camp of if were moving forward the engine stays off crowd.

A code 0 might just be a good sail to have around here as well for upwind dead air days which we have allot of in the summer around here.

Above 10 from forward and the sail would blow out as we reached same speeds and apparent became 20.

Played with it once poled out in 25 knots from behind - and felt lucky we got it down in one piece. Treated it with respect ever since.

Re you considering a spinnnaker. Always good to have one in the bag but if you've got 3 to 4 kots true off wind then the reality is a regular set of white sails shaped up correctly will probably work better than a spinnaker. If the true wind from behind nudges you to 2 knots, the wind will swing to your front and if the sails are not set to use it - you'll stop - and it all starts over once more. Hard yakka.

Set your white sails as if you are reaching (despite light wind from behind), ease every adjustment you can lay a hand on, take weight from the boom, set all weight to leeward to allow sails to shape up etc, and once any wind from behind nudges you forward the wind goes forward - and whilst it will be be apparent and less than true, it will continue to work driving you forward consistently.

Enjoy.

JOHN