45' (or so) Performance Cruising Catamaran

[arsenelupiga]

Originally Posted by StuM

Again. Link please.

Sorry, that was many moons ago and Lerouge and his page seem to be retired now. His keels are shallow and long so it is 1.1m low point.

Fixed keel also has around 500 kg more payload which is nontrivial for such sporty design.

[Factor]

Originally Posted by StuM

Have you got a link to that article?

Here is what Grainger said'

I generally recommend that daggerboards are a worthwhile investment if the owner has a preference for sailing to windward rather than motoring or waiting for a favourable breeze, and if the boat is going to be kept light enough to have a power to weight ratio that will do justice to the dagger board configuration.
As a rough guide I would suggest that a 40’ cat which had a sailing weight of six tonnes or less would benefit from dagger boards, while a relatively heavy cruising cat would gain very little benefit from the more efficient foils. On a 50’ cat the cut off point is probably about 10.5 to 11 tonnes.

[StuM]

Originally Posted by Factor

Here is what Grainger said'

Quote:
I generally recommend that daggerboards are a worthwhile investment if the owner has a preference for sailing to windward rather than motoring or waiting for a favourable breeze, and if the boat is going to be kept light enough to have a power to weight ratio that will do justice to the dagger board configuration.
As a rough guide I would suggest that a 40’ cat which had a sailing weight of six tonnes or less would benefit from dagger boards, while a relatively heavy cruising cat would gain very little benefit from the more efficient foils. On a 50’ cat the cut off point is probably about 10.5 to 11 tonnes.
__________________

Do you have a link?

As you have illustrated; it's easy to quote-mine to support any own viewpoint.

I have learnt to put little weight on any quote which doesn't include a link to the source.

[Seaslug Caravan]

Or you could try this SAIL interview with Chris White where he states....

Likewise with daggerboards: “I spent the first 15 years of my career trying to convince people they need efficient foils. And now I’ve spent the last 10 years telling them the foils don’t need to be daggerboards. There’s this mindset now that a performance cruiser without daggerboards must be a disaster, but it’s really not true.”

See Different Strokes: A profile of multihull designer Chris White - Sail Magazine

[arsenelupiga]

Originally Posted by StuM

Do you have a link?

As you have illustrated; it's easy to quote-mine to support any own viewpoint.

I have learnt to put little weight on any quote which doesn't include a link to the source.

you can as well see some race results, better than anything. This is old spreadsheet that measures performance of cats MULTI2000. Appendages like catana factor 1.048, lagoon 41 1.016, so difference in overall performance across all conditions is 3-4 % draggerboard vs fixed.

[StuM]

Originally Posted by Seaslug Caravan

Or you could try this SAIL interview with Chris White where he states....

Likewise with daggerboards: “I spent the first 15 years of my career trying to convince people they need efficient foils. And now I’ve spent the last 10 years telling them the foils don’t need to be daggerboards. There’s this mindset now that a performance cruiser without daggerboards must be a disaster, but it’s really not true.”

See Different Strokes: A profile of multihull designer Chris White - Sail Magazine

You see, that's the advantage of a link to the original quote. You missed out the next bit:

Though Chris has put daggerboards in several boats he has designed for clients, as a cruiser he doesn’t like their vulnerability when grounding and prefers to have centerboards on his own boat.

So it's because of fragility, not comparable performance. I feel the same way and wouldn't have daggerboards for the same reason.


He’s also beginning to play with another idea. To complement the new MastFoil rig on his latest Atlantic 47 design, he has put on a pair of generous fixed keels, also with trailing flaps.
“The jury is out on the new keel’s performance,” he concedes. “We haven’t really had a chance to test it yet, but I’m convinced with the flaps it will do as well as a daggerboard.”


So generous fixed keels, with trailing flaps may do as well as daggerboards, but there is no evidence as yet.

That's along way from:

I find it difficult to understand with all the information now available, that people can still believe there is a performance differential between Daggerboard and mini keel boats that could be considered significant for a cruiser.

I'm still waiting for someone to link to information showing that the performance difference between daggerboards and mini keel boats is insignificant.

[StuM]

Originally Posted by arsenelupiga

you can as well see some race results, better than anything. This is old spreadsheet that measures performance of cats MULTI2000. Appendages like catana factor 1.048, lagoon 41 1.016, so difference in overall performance across all conditions is 3-4 % draggerboard vs fixed.

There's a lot more to the "Correction d'appendices" figure than just daggerboard v fixed keel:

"IF(R7>0,1.048,IF(Q7>0,1.048,IF(P7>0,1.036,0.907+1 .55*(O7/M7)-4.449*(O7/M7)^2)))"

Daggerboards get 1.048.
Fixed Keels get a variable figure based primarily on draft/LOA. It can be as low as 0.974

So in "overall performance across all conditions" for some boats, daggerboards can be 7.5% better than fixed keels.

But when discussing daggerboards v mini keels, the question is not so much about "overall performance", it's about such things as pointing higher and making less leeway when beating into the wind. In those conditions, you will frequently see much more than that 7.5% overall improvement in VMG.

Edit: And just to clarify, that spreadsheet doesn't "measure performance" or show any results. It is purely a mechanical rating formula and anyone who has raced extensively is well aware of the problems with any individual measurement rating system.

[arsenelupiga]

Originally Posted by StuM

There's a lot more to the "Correction d'appendices" figure than just daggerboard v fixed keel:

"IF(R7>0,1.048,IF(Q7>0,1.048,IF(P7>0,1.036,0.907+1 .55*(O7/M7)-4.449*(O7/M7)^2)))"

Daggerboards get 1.048.
Fixed Keels get a variable figure based primarily on draft/LOA. It can be as low as 0.974

So in "overall performance across all conditions" for some boats, daggerboards can be 7.5% better than fixed keels.

But when discussing daggerboards v mini keels, the question is not so much about "overall performance", it's about such things as pointing higher and making less leeway when beating into the wind. In those conditions, you will frequently see much more than that 7.5% overall improvement in VMG.

Edit: And just to clarify, that spreadsheet doesn't "measure performance" or show any results. It is purely a mechanical rating formula and anyone who has raced extensively is well aware of the problems with any individual measurement rating system.

not saying differenece is small 1 deg app makes 10% diff in VMG against wind.
verified by race results, else these factors got amended.

However on average 3-4% faster in all conditions, if you do analysis. This is
same contribution as folding props.

Conditions where draggerboards have large edge is not common else that contribution would be larger.

Justy look at latest ARC results. L38 vs Catana, both sailed well. Differnece should be larger if your theory right.

[Factor]

Originally Posted by Seaslug Caravan

Considering most cruisers motor in the light stuff, including our beloved 44c, who has motored past us on a couple of occasions ( possibly due to his unwillingness to fly a spinnaker / carry a spinnaker?) Its hard to understand where this great difference lies.

Still waiting to see when it was that 44C was motoring.

[StuM]

Originally Posted by arsenelupiga

Designer of the boat has excellent articles regarding fixed keel vs draggerboard. Difference is indeed minimal. 1 degree or so.

Originally Posted by arsenelupiga

not saying differenece is small 1 deg app makes 10% diff in VMG against wind.

Minimal, small? What's the difference.

Still waiting for all this information showing that the difference between daggerboards and mini keels is insignificant.

[arsenelupiga]

Originally Posted by StuM

Minimal, small? What's the difference.

Still waiting for all this information showing that the difference between daggerboards and mini keels is insignificant.

you may just need to take it easy and maybe will come to you one day.

[Seaslug Caravan]

Originally Posted by StuM

Minimal, small? What's the difference.

Still waiting for all this information showing that the difference between daggerboards and mini keels is insignificant.

Yes, I'm still waiting for all this information showing that the difference between daggerboards and mini keels is SIGNIFICANT

[Factor]

So Mr Slug

I take it your suggestion that 44C had passed you many times whilst motoring was a furphy? A load of codswallop, rubbish and just basically internet trolling?

[SVNeko]

The Chris White quotes are not supportive of the idea that keels are just as good. First, he said he preferred centerboards to daggerboards, nothing about keels. Second, at the time of that interview he is selling his 47, which has keels with little flaps. So he would of course argue the benefits of keels.

[StuM]

Originally Posted by Seaslug Caravan

Yes, I'm still waiting for all this information showing that the difference between daggerboards and mini keels is SIGNIFICANT

You're the one that claimed that there was lots of information showing that it was insignificant. So let's see some.