Light air performance of different multihulls?

[chris mac]

Wow this went off the rails right from the get go!
To answer the actual question... our cat is the older model lagoon42 tpi. 1993.
With white sails we do about 1/2 wind speed in light winds (pretty much any reach)
When we use the asymmetrical, we jump up closer to 3/4 wind speed.
12 knots of apparent wind is where she seems to power up. The feeling is much like riding a horse, You can actually feel the boat getting excited and want to run!

[joelhemington]

Originally Posted by Sand crab

I don't follow RR. What's the affiliated version about?

Basically, it's just a semi custom boat they've added some gizmos to sorted from their cat reviews in Annapolis. Otherwise it's the same hull/bulkhead set up as the standard Seawind. This is not a completely custom boat Seawind designed just for them as the new 1370 was already on the drawing board when they approached Seawind.

[mikereed100]

I don't follow Youtubers and I can only speak for myself and my preferences, but, after over 30,000 miles on our cat I find that being able to maintain 5-7 knots is a lot more important to me than sailing in double digits. I love to go fast and, when conditions are right, I like to push the boat for a short time, but I find that cruising in double digits is just not comfortable. There is a lot more noise for one thing. More importantly, I am not relaxed, I am working. I am constantly scanning the ocean in front of me for obstacles and the horizon for squalls. I am not taking care of important things like reading my book, napping or strumming my guitar.

When the wind is up, any boat will go fast, no matter how many hulls. To me it is far more important to be able to sail when the wind is light. Our boat will do 4 knots in 4 knots of wind on the beam. I think that's pretty cool. Far cooler that surfing at 20 knots, although we have done that too. Our "good enough" speeds are very close to those mentioned by mglonnro in his original post, although our boat speed will be a bit higher in the winds he mentions.

[joelhemington]

Originally Posted by NaClyDog

I would agree with that IF they didn't do reviews of other models. What they did was disingenuous and a underhanded.

Yep, they made it clear from the get go that they were in the market for a new cat. Their problem was all the Mfgs. are trending toward 50' and up which was bigger than they wanted or needed. The new Seawind 1370 met their size criterion perfectly (which is why they chose it).

Back on topic. The best performance of any multihull will lie in it's sail inventory rather than specific hull design. A good Code O, with staysail and medium weight asymmetric are all popular choices.

[smj]

I’ll leave the RR speculation up to the YouTube naysayers, in my opinion they chose an outstanding catamaran built by a very reputable company.
The cat we own now will sail at wind speed up to about 15 kts. Of wind/boat speed if kept light and with a good crew onboard.
We have her loaded for cruising and are not good crew but usually sail at or close to wind speed in winds at or below 7-8 kts. And still see double digits in 10-12 kts of wind.
The top speed isn’t our goal, it’s the ability to sail at a decent speed with light winds which we easily achieve.
It’s also easy to achieve good average speeds in moderate winds way reefed down which means less stress on the crew and boat.

[Pillroller]

Light wind performance in a small multihull can be seriously affected by overloading weightwise. Not so apparent with stronger winds.

[malbert73]

Originally Posted by mikereed100

I don't follow Youtubers and I can only speak for myself and my preferences, but, after over 30,000 miles on our cat I find that being able to maintain 5-7 knots is a lot more important to me than sailing in double digits. I love to go fast and, when conditions are right, I like to push the boat for a short time, but I find that cruising in double digits is just not comfortable. There is a lot more noise for one thing. More importantly, I am not relaxed, I am working. I am constantly scanning the ocean in front of me for obstacles and the horizon for squalls. I am not taking care of important things like reading my book, napping or strumming my guitar.

When the wind is up, any boat will go fast, no matter how many hulls. To me it is far more important to be able to sail when the wind is light. Our boat will do 4 knots in 4 knots of wind on the beam. I think that's pretty cool. Far cooler that surfing at 20 knots, although we have done that too. Our "good enough" speeds are very close to those mentioned by mglonnro in his original post, although our boat speed will be a bit higher in the winds he mentions.

Yup, this exactly. I’ve surfed mid teens on my boat and I’m more impressed that it can sail wind speed generally when wind is single digits, assuming not DDW

[sailjumanji]

Frankly, I think Ruby Rose can spin whatever yarn they want about how much influence they had in the design. Listen to the Seawind video on it, listen to the vid interview of Shane Grover - who is head of Seawind marketing - talk about what went into the design. I don't even hear any mention of RR. They seem like a nice couple, but to say they influenced Seawind's design is probably a huge stretch. Seawind has a Facebook group especially for owners, that they monitor as well. If they want to know what owners want, what they feel is missing, etc., there are some owners who have serious sea miles cruising their Seawinds. And for RR, how many catamarans have they owned?

We are on our second Seawind. We really loved our Seawind 1000, would like more waterline, but had no interest in a cat with diesel engines, generator, heavy, etc. Seawind listened to owners like me (not me), and in 2015 introduced the Seawind 1160 Lite to target owners like me who wanted a lighter boat, outboard motors, more solar and no gen. So last year we became Lite owners. It was a new build. And it was customized just for us - including the stainless BBQ pit off of the 1260, custom bow seats via the 1260, galley cubby for our liquor and spice storage, and a cabinetry mod. If you contact them and tell them you want the Kailani version of the Lite, they can probably pull our spec sheet and build you one identical! We even have Dimension Polyant GPL Lite Skin sails, the same as offered in the 1370 performance package. (Again, I think a change that Seawind made based on the fact that several of us have used an external loft to make those sails, had excellent performance with them in both racing and cruising applications, and decided it would be smart to offer as a performance option for the new boat.)
My guess is that what's going to happen when you order a Ruby Rose - it just says you want that spec sheet. That said, again, you are relying on a couple - nice and pleasant as they are - to make your option decision for you, that have never even owned a catamaran before.

Finally, we've purchased two new Corsairs, a used Seawind cat, and now this new Seawind. I know most of the dealers, having been active in the Class Associations for years. All of that got me probably a few extra Seawind caps, and certainly no discount. If RR got a significant discount, I would be shocked. Even so, I think Seawind had commitments for around 40 Seawind 1370 builds in the 2-3 weeks after announcement. I don't think that was a bunch of RR followers waiting to sign up, based on what they chose as their next boat. It may be the "new Ruby Rose", but to most of us, it's "the Seawind 1370."

[sailjumanji]

Originally Posted by Dave_S

I agree with you that light airs is more important than other times. I have a meeting on Thursday to discuss this with a sail maker. I would be happy to reef earlier even to the point of 1st reef being the new normal and using no reef would be reserved for light air providing it will improve low speed significantly, remembering a big improvement like 20% might only be 0.5kn.

I think good enough speed is subjective, I enjoy playing with the sail set up in light air almost as much as at other times. If you have 30nm to go, 2kn SOG isn't going to do it for me but at other times it can be ok. I spoke to a guy who circumnavigated Australia and 3kn was his threshold for turning on the motors.

You got it, exactly. In our home waters, typical wind is probably 15-18 knots. But some places that we cruise, it's lighter. So we pushed the mainsail area by adding a bit more roach to the square top, and extended the jib foot as much as possible but still staying with the self tacking. Overall we moved the CE higher by about a foot, but kept the same position front-to-back. (Didn't introduce any weather helm.) So we have to reef a bit earlier than a standard-sail Lite, but in light wind we stay powered up. Its easy to deal with, especially with a single reef line and an electric winch.

But those guys that say "speed isn't important because I am a cruiser", aren't being honest. We had a 7 knot boat, and if you wanted to get to the next island 100 nm miles away and anchor down before dark, you better leave before daybreak. Make that a solid 8.5 knot boat, and you leave after daybreak and still have 2.5 hours of sunlight when you arrive. Less stress being able to navigate and anchor in sunlight.

[wingssail]

Originally Posted by mglonnro

Watching all of the Ruby Rose multihull reviews, I found myself constantly thinking that I care less about how fast (ie 20+ knots) the boat optimally can go, more about how little wind it optimally needs to have at least some speed.

The two are connected, of course, but anyway, if anyone would care to offer some real-life experiences of what you consider "good enough" sailing speed and in what conditions you expect to achieve that?

We don't have a multihull, but with our monohull, here's how it roughly goes with us atm:

- Good enough speed: at least 4.5 knots. Closer to 5 than 4. If there's an occasional 5, it feels like good going.
- Reaching, we need about 6-7 knots of true wind for this. Upwind 8-10 knots. Running (without spinnaker) maybe 7-9 knots (maybe a bit more).
- Boat packed with a moderate amount of stuff. Two adults, four children, one dog.

Maybe I missed something but I thought you were asking about what other monohull owners think.

And anyhow, in the case of monohull sailboats light air performance does not correlate to maximum speed potential.

For light air performance you need less wetted surface and big sail area.

For maximum speed you need a hull shape that basically planes and big enough sail area.

These two (less wetted surface and planning capability) are somewhat mutually exclusive.

For us good enough speed depends on the day and how we feel. Some days we hold out as the speed drops as low as under 4, upwind. Other days we get impatient at under 5 knots. At six knots, the boat is sailing great, seven feels fast, eight is awesome and nine is loud. When we get over 10 knots it goes in the log book. Of course speeds over seven are offwind speeds. The highest ever we've seen is 14knots, for a few seconds, surfing in big waves with a large spinnaker. Modern, flat underbody, boats often exceed 20knots.

We have very good light air performance. With racing sails we can hit 6.5 knots in 8-9 true wind speed, upwind. Downwind we need over 10 knots of wind to really get going unless we reach hard. We usually use a spinnaker downwind.

[mglonnro]

Originally Posted by sailjumanji

You got it, exactly. In our home waters, typical wind is probably 15-18 knots. But some places that we cruise, it's lighter. So we pushed the mainsail area by adding a bit more roach to the square top, and extended the jib foot as much as possible but still staying with the self tacking. Overall we moved the CE higher by about a foot, but kept the same position front-to-back. (Didn't introduce any weather helm.) So we have to reef a bit earlier than a standard-sail Lite, but in light wind we stay powered up. Its easy to deal with, especially with a single reef line and an electric winch.

And in the spirit of my original question: what kind of wind do you need to get the boat moving 4.. 5.. 6.. knots?

[mglonnro]

Originally Posted by wingssail

Maybe I missed something but I thought you were asking about what other monohull owners think.

No, I was just offering my own "stats", and we have a monohull. Actually I was more interested in knowing how the different multihulls fare, since we're maybe perhaps looking at one as our next boat (somewhere down the road).

But monohulls are certainly very interesting as well, so thank you for that!

[Tupaia]

Sail Area / Displacement Ratio will give a reasonable indication of light wind performance. Anything that relates to length is less informative for multis because they are not so restricted wave making drag.
Do the SA/D calculation for light displacement, loaded for upwind and downwind sails and the performance envelope becomes obvious. It also highlights performance hit suffered by overloading multis as the payload represents a much bigger percentage of the overall displacement.

[mglonnro]

Originally Posted by Tupaia

Sail Area / Displacement Ratio will give a reasonable indication of light wind performance. Anything that relates to length is less informative for multis because they are not so restricted wave making drag.
Do the SA/D calculation for light displacement, loaded for upwind and downwind sails and the performance envelope becomes obvious. It also highlights performance hit suffered by overloading multis as the payload represents a much bigger percentage of the overall displacement.

Here's a great post also using that calculation for "rough" estimation:
https://sailpuffin.com/2019/05/18/chasing-performance/

With regard to absolute numbers:

We want to maximize the amount of sailing we can do in light winds. It’s super annoying to be sailing at speeds less than we can comfortably motor. For us, that’s about 5-6 knots on a single engine. I’m sure everyone is different, but I’ll sail all day at 4-5 knots, rather than turn on an engine. So if our goal is to sail in winds at 5 and above, we have to be able to sail at or very close to the wind speed.

I know that a minimally loaded Schionning can sail at or slightly above the true wind speed in 5-12 knot winds.

As a reality check, our 5X would reliably get within 0.5 knots of true wind speed upwind in light winds. We sailed against a 4X in France and they were always a bit faster upwind than Wildling, so that indicates that for boats around 48-50 feet with these hull shapes and weight distribution, a performance number around 15.5 should be a good goal for a true wind speed capable boat.

The Outremer 51 and Balance 526 have significantly lower ratios, though. So, at 5-6 knots of true wind, what might one expect?

[arsenelupiga]

Originally Posted by mglonnro

And in the spirit of my original question: what kind of wind do you need to get the boat moving 4.. 5.. 6.. knots?

ok, as we are sailing tropics and playing seabreeze and landbreeze all the time right now, here are our experiences on lagoon 400, loaded for full time liveaboars. Should note that we are less loaded than average L 400.

Upwind 3 kn VMg you are lookng at 9 kn true. 4 kn vmg need 12 kn. 5 kn vmg, i dont do it as I like my rigging and my wife complains.

Reaching 4 kn you need 6 kn, 5 kn you need 7, 6kn you will need 9kn.

Downwind, we make with symetrical from 120 -180 true around 80 % apparent wind speed on average.

I tend to depower at 10 kn boat speed.