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Old 01-02-2015, 08:28   #31
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Re: Nautitech Open 40

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Originally Posted by 2Hulls View Post

(...) Cats in general are resistant to broaching, but take away the permanent keels and it becomes just about impossible.

2 Hulls Dave
Dave,

Can you PLS tell us a bit more on this aspect?

Is the meaning that cats without permanent keels will not broach running before the storm? Or did I read your sentence upside down and just the opposite is the case?

THX,
barnakiel
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Old 01-02-2015, 09:34   #32
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Re: Nautitech Open 40

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Is the meaning that cats without permanent keels will not broach running before the storm?
Well, I don't think there are many, if any, absolutes. And I have never had to run before a Storm and I predict it's not likely I will ever have to.

So, IMO, saying board cats can avoid broaching altogether in a Storm is a stretch, if not a very foolish assumption. But I think it's a safe statement that they'll avoid broaching better than LAR keel cats.

In non-Storm conditions, my experience (because I don't have Storm experience) is that board boats (boards up, of course) surf better and autopilots are happier than on keel cats. "Better" means less tendency to meander requiring rudder counteraction to keep them going down hill. As soon as the keels get some angle and develop some lift - they grab - the boat will follow them unless something counteracts the lift. There's a reason surfboards don't have additional skegs half way forward. It's a good thing that LAR keels aren't more efficient, otherwise the broaching tendency, however minor, might be worse. I imagine in extreme conditions dragging warps or a drogue would be a big benefit here in that the boat will not surf as fast and prevent the keels to be more effective grabbers. The higher the speed, the more lift.

2 Hulls Dave
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Old 01-02-2015, 10:08   #33
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Re: Nautitech Open 40

Yes we have felt that effect with mini keels and yes the likelyhood of broaching is pretty small. A few months ago we we surfing at 15K in 30+ K of breeze and after each surf we would round up slightly, only maybe 10 degrees but enough to be concerned about the possibility of a broach, which could be disastrous on a cat. However after several hours/days in these conditions we came to realise that the boat was very comfortable and tracking very well with minimal AP input, either under parasailor or main and jib.
There's definitely a lot of swings and roundabouts with yacht design and boards or no boards have too many variables to say one is better than another on any particular design.
I did see a couple of the open40s in la Rochelle. They looked neat but not something I'd consider for what we want. Video was impressive. 25 K on the beam in flat water is pretty a pretty rare occurrence so I wouldn't be basing my purchase on those conditions unless most of my sailing was from the marina, out for the day and back to the marina, but in that situation I probably couldn't care less what the boat speed was each way...
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Old 01-02-2015, 14:10   #34
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Re: Nautitech Open 40

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Yes we have felt that effect with mini keels and yes the likelyhood of broaching is pretty small. A few months ago we we surfing at 15K in 30+ K of breeze and after each surf we would round up slightly, only maybe 10 degrees but enough to be concerned about the possibility of a broach...
Hi Monte - that may not have been a "keel grabbing" effect as much as it was a typical sail plan/hull imbalance. Because you described it as "after each surf" suggests it was when the boat had already passed its highest speed and was slowing down and apparent wind was returning to what it had been - creating an imbalance that the boat reacted to and headed up just like a puff in flat water? The broach, if it's gonna happen, will come during/after acceleration to a much higher speed than previous and before de-celeration, it seems to me.

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Old 01-02-2015, 14:58   #35
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Re: Nautitech Open 40

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(...) after each surf we would round up slightly, only maybe 10 degrees but enough to be concerned about the possibility of a broach (...)
Possibly too this is something related to change in hull dynamics as you go from planing back to displacement?

I had the same just more pronounced when racing International 420. Except the dinghy would bear off, no matter what we did with the helm.

I think a keen skiff racer could let us know more on this point.

b.
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Old 03-02-2015, 11:15   #36
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Re: Nautitech Open 40

Do see attached the Stubs or Boards discussion - as in the attached jpeg .... indeed not very scientific but there are some valid points
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Old 03-02-2015, 11:31   #37
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Re: Nautitech Open 40

Well, I don't see any valid points. But I could make at least two that he didn't mention: boards cost more and take up some interior room.

If you'd like to discuss any "valid" points he attempts to make, I'd be glad to participate.

Dave
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Old 03-02-2015, 17:17   #38
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Likewise this seems an odd "article" to me too. No valid points in it.

The weight issue is false. My wife can raise our boards one handed - no need for "4 strapping lads" as claimed.

This is just marketing puffery to justify this brands choice

Boards point better, are faster on all points of sail ( not just ddw as claimed) offer greater flexibility in trim, have less draft, can be repaired without a haul etc etc

Biggest negative is initial cost. Another is forgetting to raise them if you a charter skipper :-)
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Old 03-02-2015, 17:48   #39
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Re: Nautitech Open 40

Per the article, boards are "dangerous"?

Again, there can be good reasons for a particular cat buyer not to choose a boats with boards, depending on his/her preferences. brainmaker, just be sure you rely on legitimate reasons. Aside from the indirect reference to higher cost of boards, and the misleading argument of higher weight, there are no legit reasons in that article, and several boldface untruths.

Dave
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Old 03-02-2015, 18:13   #40
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Re: Nautitech Open 40

This is a long debate; the brands that are using it (Catana, Swisscat, Outremer, etc)are doing it because they believe in it.
The ones who make the cat with a fixed keel (FP,Lagoon, Nautitech and many others) are obviously saying the opposite..
Like many other things on boat design (fixed vs. rotatif mast, alu mast vs. carbon, etc..)there are cons and pros.
I've sailed with both of them (Catana 581, O 51, GB 62) with dagger board and almost full range of FP and some Lagoons without.
The pointing ability with dagger board is superior but the difference is not huge. Most of these cats are already better upwind anyway because of their hull shapes, weight, sail plans, etc. If you add a dagger to Lagoon 450, her pointing ability would only improve marginally, if at all..Vice versae, we tried on O 51 to not the use the dagger boards at all upwind and we couldn't feel the difference. But again, Outremer had a beautiful laminated sails, rotatif mast and slim hulls...
To me, the biggest advantage of dagger boards are in giving much less leeway; that makes a lot of difference, more on choppy seas and or lighter winds.. Everybody is talking about the upwind performance but as Barra said, they are clearly faster downwind as well. (less friction, less wetted surface when the boards are pulled off)

The biggest downside is initial cost and the loss of payload (app 500-600 kg fo 45-47 ft cat). It's also true that the galley becomes significantly narrower. Hitting something when the board is lowered can also be more dangereous compared to a sacrificial fixed keel.
Dagger boards are something that I would definately consider if I plan to sail in high lattitudes; with the boards up such cat can skid away with big waves from the beam whilst the cat with a fixed keel can be tripped over. Also higher mileages on long passages would make a lot of difference.

I know Mr Voisard and we discussed this high lattitude issue with him, he also disagree with this scenario.

Back to Nauthitecs, they are beautiful catamarans, slightly overpriced but they are faster than FP or Lagoon . I have heard that they are now preparing a new 46 footer.

Cheers

Yeloya
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Old 03-02-2015, 18:33   #41
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Re: Nautitech Open 40

Yeola, all good points.

I hope Nautitech offer an alternative to the back porch steering on the 46.

Many designers offer a choice of daggerboards or minikeels.

On a small vessel such as a 40ft there will be some space lost in the support structure in the hulls and the bouyancy translated to load capacity which can be an issue with a 40ft vessel.

I am sure these issues were in the designers mind although unstated in his article. some designers thesedays are going with only one daggerboard (Suttleworth) and one can always use a motor to get closer to the wind on the ocassion you would have used a board.
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Old 03-02-2015, 19:11   #42
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Re: Nautitech Open 40

On a daggerboard boat the rudders are vulnerable to damage as they have a deeper draft than the hull. On a cat with mini keels, the keels protect the rudders.
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Old 03-02-2015, 19:28   #43
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Re: Nautitech Open 40

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On a daggerboard boat the rudders are vulnerable to damage as they have a deeper draft than the hull. On a cat with mini keels, the keels protect the rudders.
Thats why alot of board cats have skegs ahead of the props and rudders. Some are sacrificial but the really clever ones have a little foot that can take the stern weight for beaching too. These are in the cruisers version of board cats.

Looks like this is going to turn into a board vs keel thread so im gonna head this off at the pass - they both have there pros and cons (again) but the ones in the article are not the valid ones.

Ok im outa this thread in case someone brings up lifting keel monos or something
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Old 03-02-2015, 20:32   #44
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Re: Nautitech Open 40

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Thats why alot of board cats have skegs ahead of the props and rudders. Some are sacrificial but the really clever ones have a little foot that can take the stern weight for beaching too. These are in the cruisers version of board cats.



Looks like this is going to turn into a board vs keel thread so im gonna head this off at the pass - they both have there pros and cons (again) but the ones in the article are not the valid ones.



Ok im outa this thread in case someone brings up lifting keel monos or something

Don't get me wrong, I like daggerboard cats but neither the Catana or Outremer seem to have any form of protection for the rudders or saildriives in the event of a grounding. And I would say they make up the majority of the daggerboard cats.
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Old 03-02-2015, 23:10   #45
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Re: Nautitech Open 40

Small beaching keel on a daggerboard vessel to protect prop and rudders.
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