Upwind performance of condomarans

[catsketcher]

Charlie - the tri was a Nicol, probably the 29ft Islander - Demi-Star perhaps or Pelinta? Brown designed Searunners that always had a large pivoting centreboard in the central cockpit. The Nicol would have had rounded hulls and the Searunner sheet ply.

In Tassie there is a pod cat in Kettering built by a nice guy called Steve - damn fast machine. He has keels on it. It probably goes faster than my boat to windward.

There are heaps of things to make a boat go to windward. Getting drag low is paramount - so having a clean bum, having the transom clear or only slightly immersed, having enough power from the rig to get the foils working well in slop, having weight out of the ends in chop, having a tight sheeting angle and more.

But you can't make a purse out of a sows ear. If the hulls and the platform are high drag (heavy and fat) you can't put a low drag/low power rig on it and expect it to point high. If you have high windage and increased drag the only way to cater for this is to point lower - compared to a lower windage/lower drag sistership.

John Shuttleworth goes through the maths in a few articles on his website if you want to know more. The basics are - high windage+ high drag hulls = lower pointing ability and speed upwind. But we need accomodation and something to keep the water out so designers juggle the numbers. These articles were the basis for the cat designs in the 90s and early 2000s - the more performance cruisers often found in Australia. There has been a shift back to more slab sided cats for many since but the physics is still the same.

Article Dogstar 50

Considerations for Seaworthiness

cheers

Phil

[charliehows]

Yeah probably a Nicol - I'll never forget one long day beating tediously and almost pointlessly back towards Auckland, this giant red monster tri that had been built for a round Australia race was doing sea trials, she came past me going almost dead upwind, every bloody wire screeching with pressure, as if I was standing still - which I may as well have been given my tack was pretty close to perpendicular to the bloody wind...I don't remember what they had in the water but it had some serious lateral resistance

[arsenelupiga]

Originally Posted by charliehows

I owned a 30' Jim brown or Hadley Nichol( never did work out the provenance) trimaran in the 80s - she had pissy little minikeels on the outriggers and sailed better sideways than forward upwind, had to back the jib to tack, an all round dog upwind but she could outrun anything off the wind. Since then I've taken a bit of interest in multis - for fear of labouring the point, the single determining factor for upwind performance is whether the boat has good, deep dagger boards, let's call this 1001 times - ROM you may have heard this already in your 2 years experience, I've tested it out a few times in my 5 decades of experience but you may have to hear it a few more times...

the boat i really wanterd to buy was soubise. And architect explained that difference draggerboard vs minikeel is 1 degree apparent which turns into 2.6% better VMG. Big deal for some but for most, not really.

Go back to your books and study again.

[BigBeakie]

Originally Posted by arsenelupiga

the boat i really wanterd to buy was soubise. And architect explained that difference draggerboard vs minikeel is 1 degree apparent which turns into 2.6% better VMG. Big deal for some but for most, not really.

Go back to your books and study again.

I think your NA better go back to his books

[44'cruisingcat]

Originally Posted by arsenelupiga

the boat i really wanterd to buy was soubise. And architect explained that difference draggerboard vs minikeel is 1 degree apparent which turns into 2.6% better VMG. Big deal for some but for most, not really.

Go back to your books and study again.

Designers who draw boats with keels and daggerboards generally say the difference is around 5' in leeway, and a couple of degrees in pointing ability. The VMG difference can be upwards of 10%.

[arsenelupiga]

Originally Posted by 44'cruisingcat

Designers who draw boats with keels and daggerboards generally say the difference is around 5' in leeway, and a couple of degrees in pointing ability. The VMG difference can be upwards of 10%.

they are cherry picking examples.

To be fair, Lerouge said that his design minikeels make 1 degree difference. Other minikeel designs not as efficient.

You get more difference with rotatif mast but this is another chapter for another day.

[rom]

Originally Posted by SailFastTri

Here's a short clip of a Dragonfly

Very nice boat, really I like fast boat too. Yes trimaran are usually faster that condomaran ! Thank you !

I was hoping to restore some truth about what one shall expect going upwind with condomaran. I am afraid this is going nowhere. Hopefully the tracks I posted were helpful to some potential condo buyers out there. Should they decide that such performance is not good enough for them, they may have a look at "fast cruisers" like catana, outremer, TS, etc ...

[44'cruisingcat]

Pity no one else posted tracks from their boats.

Still, you did demonstrate that a lagoon 440 CAN get you to a windward destination.

[SailFastTri]

Originally Posted by rom

Very nice boat, really I like fast boat too. Yes trimaran are usually faster that condomaran ! Thank you !

I was hoping to restore some truth about what one shall expect going upwind with condomaran. I am afraid this is going nowhere. Hopefully the tracks I posted were helpful to some potential condo buyers out there. Should they decide that such performance is not good enough for them, they may have a look at "fast cruisers" like catana, outremer, TS, etc ...

Actually there is no inherent speed advantage of a tri over a cat, and a light cat should in theory have an advantage in speed. 2 hulls are less wetted surface than 3, and could be less complex structurally. Some other posts above discussed what makes good upwind performance: High-aspect deep underwater foils, narrow/close sheeting capability, narrow hulls, high SA/D. You can get these things in multihull boats, but they’re not common in “condomorans”.

The market is defined by demand, and most couples buying cats get their experience and tastes honed on charter boats and by walking the docks at boat shows. Comfort and amenities usually take design precedence over performance. Low cost and low weight with high performance are also conflicting design goals.

[yeloya]

Originally Posted by arsenelupiga

To be fair, Lerouge said that his design minikeels make 1 degree difference. Other minikeel designs not as efficient.

You get more difference with rotatif mast but this is another chapter for another day.

I've sailed cats with mini keels, dagger boards and rotatif mast. Minikeel design doesn't change the overall performance much, the hull shape does. Lerouge design very slim boats and they point well even with mini keel, regardless which minikeel. Vicea versa, if we were to install daggerboats on condomaran, would the upwind performance improve much ?
I've sailed with Outremer 51 with rotatif carbon mast. To be honest, I didn't find any noticeable difference.

Cheers

Yeloya

[MLOI]

Originally Posted by 44'cruisingcat

Designers who draw boats with keels and daggerboards generally say the difference is around 5' in leeway, and a couple of degrees in pointing ability. The VMG difference can be upwards of 10%.

I was lucky enough to get to have drinks and chat with a bunch of multihull owners last year, including the owners of Thor and Slim - who I suspect you know.

As someone who has always sailed monos, I asked a heap of questions, and was humored with some answers.
The message I came away with was that there seemed to be consensus that in a equally laden cat, that dagger boards gave an insignificant advantage upwind, but a substantial one when drawn up going down wind. This is compared to well designed mini keels of course.
Oh. the difference between 50cm and 120cm draft was also considered a big deal.

As might be obvious I have now moved to wanting a 40 ish ft cat from either schionning or Oram design as a cruising boat. I do not see any disadvantages compared to my current mono, except cost.

Monos for racing of course.

Mike

[44'cruisingcat]

I'd be very surprised if Bob Oram would describe the upwind advantage as insignificant. Although I guess your definition of what is significant would depend on how much upwind sailing you do.

Something that's rarely mentioned, is that minikeel boats will pitch more too, due to the extra buoyancy midships. It's effectively like adding more rocker. That will impact on performance also.

But if you don't sail to windward much, + or - 10 to 15% probably wouldn't matter really.

I've always said the real advantage is downwind though. Where you're not dragging foils you don't need through the water.

[django37]

Lagoon 380, squaretop main 7 m2 larger than standard pinhead, flat water, true windspeed in m/s, not knots, 2 blade folding props.

[rom]

Originally Posted by django37

Lagoon 380, squaretop main 7 m2 larger than standard pinhead, flat water, true windspeed in m/s, not knots, 2 blade folding props. Attachment 164355

Hey Django, looks like new electronics, what AP is that, does it help upwind ? (I mean compared to your previous AP, possibly raymarine like mine...)

Squaretop, same question does it help upwind ? Does it have a rather high draft like standard condo sails or did you order it more flat ?

[django37]

Instuments are B&G/Simrad, changed from Raymarine 4 years ago, B&G is especially designed for sailboats. Squaretop is much better - mainly because its bigger area and its up where the wind blows. Genoa is 5 sq,m smaller - just less overlap. Sail are better quality, so they dont get fuller, when the wind gets up. The standard sail from Incidence are much too soft.