Cruising cat - sub 90 degrees tack upwind

[arsenelupiga]

Originally Posted by Factor

High aspect ration daggers will always work better to windward than low aspect ration minikeels. An interesting comparison is the Seawind 1160/1190, same hulls, same engines etc. The 1190 has a slightly taller rig and has a bit more carbon, but the actual hull shapes are identical, the 1160 has LAR keels and the 1190 has Daggerboards. In the actual real world, boat on boat, the 1160 on 1190, the 1190 will point 3-5 degrees higher in all conditions and go slightly faster doing it.

thanks for interesting data point. Are we talking 3-5 degrees apparent or actual ?

Originally Posted by Factor

LAR will never get as high as HAR Daggers, never. Everyone of them I have sailed near in the same conditions actually struggles to make any VMG to windward,

ok, how do you explain Django numbers, mine are still in verification stage ?

https://www.cruisersforum.com/forums...ml#post3333350

Originally Posted by Factor

Seriously?

I dont see any reason to discharge this fact, assuming it has been proven before. VPLP seem using this technique on Lagoons and now Outremer. Will be interesting watching new O 55 vs older models that have narrower hulls.

[fxykty]

Originally Posted by arsenelupiga

thanks for interesting data point. Are we talking 3-5 degrees apparent or actual ?









ok, how do you explain Django numbers, mine are still in verification stage ?



https://www.cruisersforum.com/forums...ml#post3333350







I dont see any reason to discharge this fact, assuming it has been proven before. VPLP seem using this technique on Lagoons and now Outremer. Will be interesting watching new O 55 vs older models that have narrower hulls.

There is no comparison between the old and new O55 - as I pointed out before the new one is almost 50% higher displacement and 15% wider, with much greater sail area to match. It is a completely different boat. I would not trade our slim easily driven hulls for anything that requires more power to keep it moving, and that’s even including the Standard near-sister ship of our Light.

Each to their own.

[arsenelupiga]

Originally Posted by fxykty

There is no comparison between the old and new O55 - as I pointed out before the new one is almost 50% higher displacement and 15% wider, with much greater sail area to match. It is a completely different boat. I would not trade our slim easily driven hulls for anything that requires more power to keep it moving, and that’s even including the Standard near-sister ship of our Light.

Each to their own.

looked at the pics - see what you mean. Different school designers - comparing these 2 boats. Still performance wise they claiming matching wind speed up to 12 kn.
And also claim 15 degress better pointing due to daggers !! Seem bit over the top. Meaning boat will do 20 app or even below?!?!

Open cockpit - not worried about wave filling cockpit and then hulls and then next wave flips.

[BigBeakie]

If Arsen thinks a Lagoon with "saggy sails", of equal LWL to an Oram 44 that is at full cruising displacement, will outperform the Oram upwind, well then there is some seriously powerful Kool-Aid being consumed on a certain Lagoon....

[arsenelupiga]

Originally Posted by BigBeakie

If Arsen thinks a Lagoon with "saggy sails", of equal LWL to an Oram 44 that is at full cruising displacement, will outperform the Oram upwind, well then there is some seriously powerful Kool-Aid being consumed on a certain Lagoon....

yup, sorry i forgot to add exclusions in tiny print. Not to worry, Oram 44 is on that list.

[smj]

An opinion from another multihull designer.

https://www.sailingcatamarans.com/in...-pros-and-cons

[44'cruisingcat]

Originally Posted by arsenelupiga

i mentioned lagoon with crappy sails. My sails are in quite good condition, so I meant generic lagoon and not mine.

going back to hull shape, this slow mode would happen when hulls sink beyond hull curved shape and bow wave increases at much faster rate than when in 'curved hull' area. As speed does not increase, rigging would have to take all the beating.

Condo cats have more curved area - fatter - and therefore tolerate overload better. But that 'fatness' comes at a cost in othere conditions.

You do make some strange claims. Now you're saying a Laggon with "crappy" sails will perform better than one with good sails?

To say "condo" cats tolerate load better is kind of like saying a semi trailer tolerates load bettet than a sports car. Yes, the semi can carry more and lose less of it's performance, but even completely empty it's much slower than the fully loaded sports car.

[44'cruisingcat]

Originally Posted by arsenelupiga

not interested in racing . But I am sure you are faster, so there is nothing to prove.

This thread has improved knowledge about the subject for me. Hope other dont see it as only pissing competition.

ALthough this topic was intended for bigger space fixed keel cruising cats as some call them condomarans, most interest from owners of faster boats.

this are my thoughts at present
Daggerboard cats - they are made to go fast on expense of space and daggerboards used as flexible keels. Work better than fixed keel where running seas as can grab deeper unlike fixed that can go down only say 1.3m. Speed first and optimum tack angle around 110.

fixed keel - condomarans - use fixed keel to climb steep upwind when conditions allow and optimal tacking angles are likely less than 110, possibly 90. This is very different than what is official knowledge of these cats - suggesting 50 apparent angle is the best and anything below 45 apparent is waste of time as one will get 20 degrees leeway. In saying that there was no other condomaran than 2 x lagoons able to provide any evidence of this behaviour. Does not mean only certain lagoons can do that. It can also mean that owners of other condos do not sail optimally upwind following 50 app wisdom.

Hull width and ratio - Django provided some facts about hull speed that are quite against mainstream. As he is naval architect one should take it seriously. basically wider hulls perform better because create lesser bow wave. I observed today wave when doing 7-8 kn and indeed less hull is in water than when not moving. So this physical law is helping condomarans to perform better than one would think and again clashes with accepted wisdom.

As keel cats can do sub 90 tacks, that actually means leeway of keel cats must be small. Again countering collective wisdom.

I plan to go Lake Macquaire - guaranteed no current - and do another upwind test to see if 90 tacks are reality on L 400 or was just string of luck that boat was in favourable current every time my tacks below 90 deg.

Has Django carried out tank testing?

Edmund Bruce performed tank testing and found that slimmer hull produce LESS bow wave. In fact that's why most multihulls are not constrained by theoretical hull speed. As LWL : BWL gets higher bow wave creation reduces.

As for Django's tacking angles, as I said before, go slow enough and it gets easy. The slower you go, the smaller the difference between TWA and AWA.

ROAM demonstrated this by doing sub 90' tacks in their performance cat, by furling the headsail and sailing slower.

As an example, in 12 knots true, sailing at 30' apparent, 8 knots boatspeed, you tack through 100 degrees. At 5 knots you tack through 84. But VMG drops from over 5 to around 3.

[arsenelupiga]

Originally Posted by 44'cruisingcat

Has Django carried out tank testing?

Edmund Bruce performed tank testing and found that slimmer hull produce LESS bow wave. In fact that's why most multihulls are not constrained by theoretical hull speed. As LWL : BWL gets higher bow wave creation reduces.

As for Django's tacking angles, as I said before, go slow enough and it gets easy. The slower you go, the smaller the difference between TWA and AWA.

ROAM demonstrated this by doing sub 90' tacks in their performance cat, by furling the headsail and sailing slower.

As an example, in 12 knots true, sailing at 30' apparent, 8 knots boatspeed, you tack through 100 degrees. At 5 knots you tack through 84. But VMG drops from over 5 to around 3.

at 8kn VMG is 5.14 , at 5 kn VMG is 3.71. Although you go 60 % faster, VMG is only 38% faster.

Now imagine I would use common visdom to go upwind at 50 apparent. No matter how fast, the best VMG is achieved at around 5 kn and is 1.82 kn.

So with using new technique i have improved VMG for nearly 2 kn ! That is what i call improvement

[cwjohm]

Originally Posted by 44'cruisingcat

Has Django carried out tank testing?

Edmund Bruce performed tank testing and found that slimmer hull produce LESS bow wave. In fact that's why most multihulls are not constrained by theoretical hull speed. As LWL : BWL gets higher bow wave creation reduces.

As for Django's tacking angles, as I said before, go slow enough and it gets easy. The slower you go, the smaller the difference between TWA and AWA.

ROAM demonstrated this by doing sub 90' tacks in their performance cat, by furling the headsail and sailing slower.

As an example, in 12 knots true, sailing at 30' apparent, 8 knots boatspeed, you tack through 100 degrees. At 5 knots you tack through 84. But VMG drops from over 5 to around 3.

I think this nails it. IMO this whole thread is based on a false premise that achievable minimum tacking angle is of any consequence. This is probably promulgated by youtube videos showing instruments demonstrating that such and such a boat has achieved a minimum tacking angle, as if this really demonstrates anything tangible for a cruiser as against a racer.

Arsen demonstrates that a cruising cat can tack 90 degrees upwind but so what?

He states that he is not interested in racing so he is not laying for a mark.

He simply wants to get from point A to point B, so VMG is the only metric to be used, and for most if not all sailing cats VMG is not optimised at the closest wind angles.

In regard to his examples of sailing between land obstacles such as islands, it is true that he can minimise the number of tacks in doing so but he will be much slower. A fast cat with a self tacking main will make short work of the greater number of tacks a larger wind angles and significantly better VMG.

In regard to general cruising in which most cruisers have a preference not to be hard on the wind, a performance cat will outperform the lagoon simply on the basis of physics. The "lesser bow wave statement" of a broader hull defies the standard laws of physics and is false.

Your lagoon 400 is a nice comfortable boat and has a good carrying capacity for enjoyment of the owner. It will take you from point A to point B in safety and comfort. It will not in any way outperform a lighter, finer hulled boat built for performance.

[44'cruisingcat]

Originally Posted by arsenelupiga

at 8kn VMG is 5.14 , at 5 kn VMG is 3.71. Although you go 60 % faster, VMG is only 38% faster.

Now imagine I would use common visdom to go upwind at 50 apparent. No matter how fast, the best VMG is achieved at around 5 kn and is 1.82 kn.

So with using new technique i have improved VMG for nearly 2 kn ! That is what i call improvement

Who tells you you should sail upwind at 50 apparent? On my boat that would be sailing DOWNWIND. The Laggon 38 I once sailed on did around 35 apparent for best VMG. Does Laggon suggest 50 apparent?

[Apollo19.5]

arsenelupiga, so I have been following this with interest and trying to understand the logic of all points put forward by all contributers. If I understand what you are saying, it can be summarized by that because wider hulled cats are more displacement style and increased drag (due to hull and mini keels), that once they get towards their theoritical hull speed, there is decreasing returns for chasing extra speed by footing and therefore you are better to feather a bit more and put increased height into the equation whilst staying close to your theorical hull speed. The result would be a closer apparent wind angle and reduced apparent wind speed as you would be if footing through the water. Is this a reasonable summary? This is the theory in some yachts I have raced over the years, but I havent spent enough time in wider hulled cats to test it there.



Conversely, a narrow hull with daggerboards would be more towards a semi displacement shape and have lower drag, so the returns for speed of footing a little more are much higher making this tactic much more applicable. This is what I have done in my cats over the years. I guess the AC cats of previous years were the extreme example of this. The Kiwis footed and foiled whilst the others initially pointed and were off the foils going to windward. Once it was obvious the VMG gains were greater for the Kiwi approach, the rest followed and it became the normal.

[Dave_S]

Originally Posted by cwjohm

I think this nails it. IMO this whole thread is based on a false premise that achievable minimum tacking angle is of any consequence. This is probably promulgated by youtube videos showing instruments demonstrating that such and such a boat has achieved a minimum tacking angle, as if this really demonstrates anything tangible for a cruiser as against a racer.

Arsen demonstrates that a cruising cat can tack 90 degrees upwind but so what?

He states that he is not interested in racing so he is not laying for a mark.

He simply wants to get from point A to point B, so VMG is the only metric to be used, and for most if not all sailing cats VMG is not optimised at the closest wind angles.

In regard to his examples of sailing between land obstacles such as islands, it is true that he can minimise the number of tacks in doing so but he will be much slower. A fast cat with a self tacking main will make short work of the greater number of tacks a larger wind angles and significantly better VMG.

In regard to general cruising in which most cruisers have a preference not to be hard on the wind, a performance cat will outperform the lagoon simply on the basis of physics. The "lesser bow wave statement" of a broader hull defies the standard laws of physics and is false.

Your lagoon 400 is a nice comfortable boat and has a good carrying capacity for enjoyment of the owner. It will take you from point A to point B in safety and comfort. It will not in any way outperform a lighter, finer hulled boat built for performance.

I agree completely that tacking angles are irrelevant. However I have always been a bit perplexed about the bear away for best VMG theory and would be interested to know if it works for others. I have seen this a few times - cats will improve VMG if you bear away a few degrees upwind.

Unless you can bear away and keep your AWA I haven't found this to be true, sure it goes faster but less VMG upwind.

I wrote this back a bit and it's a bit of a surprise but true unless windage improves but I don't see much/any windage change from when the boat is hooked up to bearing away a couple of degrees.

Originally Posted by Dave_S

If you can sail at 30° apparent at 70% true wind speed there is no speed (real or imaginary) you can sail at 32° apparent that can get you upwind as fast.

I think people know when the sails are stalling and the power just falls in a hole, so I'm assuming we are not talking about a starting point of unrealistic pinching. My boat sails nicely at 30 with good power and the air flow remains attached but at 26 it is very obvious we are going nowhere. So 30 is my go to AWA, maybe a bit better if the sea state is particularly good.

[Factor]

The thought that wider hulls and min keels will be better to windward is at odds with the OMR (Offshore Multihull Rule) and the texel rating system. The rating systems penalise (i.e. presume they are "faster".

[arsenelupiga]

Originally Posted by 44'cruisingcat

Who tells you you should sail upwind at 50 apparent? On my boat that would be sailing DOWNWIND. The Laggon 38 I once sailed on did around 35 apparent for best VMG. Does Laggon suggest 50 apparent?

https://www.katamarans.com/lagoon-400/

". Just like any keel cat, she’ll sail up to 45 degrees apparent, but you are best off bearing away 5 degrees or so to keep your speed up and minimise the leeway. If you head too close to the wind, you might see the leeway build up to 20°."