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Old 27-11-2015, 09:57   #31
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Prout's weren't failures, New Multihull idea for JBuffett

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Originally Posted by SVNeko View Post
Thanks for digging these up. Clearly you have thought about these issues in the past, as have others along the lines of the O Yachts solution. The O Yachts design seems to have adequately addressed the structural issues of having this "third" hull, and even taken advantage of it by designing in a mast aft rig supported by the nacelle and a carbon bulkhead (moving the rig aft is another design departure catching on slowly). The wave "attacking" nacelle seems to exist and work in powercat design. I wonder how it will function on a sailboat. Part of the problem is getting a guinea pig to part with $1m to possibly end up owning a failed experiment. Would be nice to have some real world data on wave piercing nacelles on sailboats (as well as moving the rig slightly aft).
Could a 'failed experiment' be any worst than an older Prout design? These had a mast aft and a nacelle, neither of which I consider state of the art. Yet a lot of owners are happy with them, and they still sell in the market place.

I'm working on a smaller (AND CHEAPER) vessel idea with perhaps a few such features as I've mentioned,...as an alternative to that monohull they sold to Jimmy Buffett recently. I think he bought the wrong boat for what he likes to do in primarily shallow waters. How about a 44 foot multihull rather than that mono?

Jimmy Buffett just bought a New Sail/Gamefishing Boat,

How about a 'defanged' SIG 45 concept?,...or something like that?
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Old 27-11-2015, 10:19   #32
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more Center Nacelle/Wave Splitter

How about the maintenance factor, particularly in remote cruising areas. No need to haul-out the vessel to repair kick-up CB problems, or even bottom painting problems, or gravel in the trunks, etc.

Everything, including the cables, bearings, and boards is all above the load waterline. The initial building cost should be less by eliminating the trunks in two hulls, and the watertight integrity is much better. The twin boards might have to be made a little bit longer as they operate with a 'free-surface' end, but then they are asymmetric so they can be correspondingly shorter.

I would further suggest that surplus helicopter blades are prime candidate sources for both CB blades and rudder blades....high tech, extremely strong carbon fiber fabrications that have a prescribed limited life span aboard aircraft, but are perfectly happy for our use


And we might even incorporate a propulsion system into our center nacelle, particularly if we are utilizing a relatively small power plant, principally for auxiliary purposes, as opposed to a more heavy duty application such as motorsailing. If I were looking to use my auxiliary engine in a strictly aux manner, rather than in a motor/sailing demand, I would seriously consider a single engine installation. This engine would be conveniently mounted in an enclosure on the cockpit deck and would belt drive a steerable out-drive leg that would be incorporated into the rear portion of the central nacelle structure.

Maybe this rear nacelle might appear as on "Earthling's pod" .

This saves the cost and weight of the second engine, transmission, shafting, prop, etc, and opens up the rears of the hulls for a nice master bath, or whatever.

A couple of quick notes in reference to the early Prouts that were some of the earliest users of a significant central nacelle. These vessels carried a full bridgedeck all way to the bow which really made them susceptible to wave interference. In contrast to their very small little V shape nacelle in their bow area, they would have faired much better with a nacelle bow shape as found on the TriCat ferry designs.

And the rear shape of their nacelle was far too beamy & voluminous in shape so as to accommodate their outdrive unit. This largeness of the nacelle at the rear forced even more compression upon the water flowing down between the hulls, and thus peaked the water into the bridgedeck bottom, SLAM. Their nacelles were after the right idea, they were just incorrectly designed.


Finally, it is not impossible to think of retro-fitting a wave nacelle concept to an older boat design. Such a project might even be accomplished in stages, a flat plate nacelle first, and then adding the fairing at some later date. And this 'staged' project might be reasonable in cost.
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Old 27-11-2015, 11:23   #33
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Re: Performance 50-55' Cats: Outremer vs Catana vs Swiss Catamaran

Here's another interesting option.

BoatSmith Ariki 48********** BoatSmith
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Old 27-11-2015, 13:00   #34
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Re: Performance 50-55' Cats: Outremer vs Catana vs Swiss Catamaran

We owned a 50' Dutch built custom cat and had the opportunity to "borrow" a friend's Catana 471 for 3 months back in 2008 (good friend to have!). I'll only speak to the helm topic.

In our experience (all over Caribbean, trans Pacific and all around NZ/Fiji/Tonga) I would say the percentage of time actually holding the wheel was less than 2%. I used to joke that the only time I wanted to touch the thing was leaving the slip or mooring and returning. I'd be curious to know what other folks experience is.

We enjoy sailing and those times when it is fun to play around and "work" the boat are fantastic, stacked up against the day to day cruising however a small slice in our experience. The Catana's helm set up was excellent for maneuvering, what I didn't like was it lack of a proper rub rail. This is another topic I'd love to dig into.

The other issue I had with the Catana was the size of the heads but that may be more of "me" issue than a "design" issue or the French are very small :-)

Great problems to have and enjoy whichever you decide.

Other dirty little secret, they all bang at some point or another :-)
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Old 27-11-2015, 13:11   #35
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Re: Performance 50-55' Cats: Outremer vs Catana vs Swiss Catamaran

Hi,

To state the obvious - performance depends on the power to weight ratio. In my experience of 200+ designs of all kinds, for cats it is not quite that simple, and the range of weights for the same length may surprise. Add the weight of all those home comforts and then adding Sail Area does not get you back to the joy of true light weight sailing.

Several of my Suncat 40's have circumnavigated. " Lady Jane " was re-launched here half way after anti fouling. Fully loaded for the next leg she logged in at 5.5 tonnes. She has twin diesels and perhaps not the lightest. "Lagoon 39", light, is given as 12 tonnes. Lagoon 52 is given as 26 tonnes against 54 "Cool Change" on charter at 14 tonnes. these are the standard Kelsall spec which has stood the test of time over the past 5 decades.

Production methods are rarely least weight. Solid below wl, Balsa core (avoid) , double moldings and the typical heavy 3 stay cat rig do not help. There is a lot to be said for arranging a custom build and you might be surprised at how competitive it can be.

To those planning solo sailing - there is nothing like the confidence from knowing every detail of your boat.

Happy boating,

Derek
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Old 27-11-2015, 14:04   #36
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Re: Performance 50-55' Cats: Outremer vs Catana vs Swiss Catamaran

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Originally Posted by akprb View Post
SNIP

In our experience (all over Caribbean, trans Pacific and all around NZ/Fiji/Tonga) I would say the percentage of time actually holding the wheel was less than 2%. I used to joke that the only time I wanted to touch the thing was leaving the slip or mooring and returning. I'd be curious to know what other folks experience is.

SNIP
The OP mentioned he was looking for a boat that would not be falling apart all the time. I have an older AP on my Seawind and I have not had problems with it but have several friends who seem to be not so lucky.

My sailing is somewhat limited to the Florida Keys and one thing I notice is that even with the remote at my finger tips I often have to turn off the AP and hand steer to most easily avoid the lobster pots which often seem so close you could jump from one to the other. I also spend time at one of the two wheels when navigating by eye ball through coral heads and shallows.

Not saying I don't use the AP on passages I know will be a straight shot and free of lobster pots. I suspect a lot of how much you use the AP depends on where you plan to sail. Another comment is that I normally can set a course and trim the sails to the extent that the boat is sailing itself on a course and the AP is hardly working at all. This is a function of a well designed boat (at least in my opinion).

I would be curious as to others experience in how well their boat is balanced so it can be sailed with a neutral helm by trimming the sails. This is one of the things that would be a deal breaker for me.
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Old 27-11-2015, 14:41   #37
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Re: Performance 50-55' Cats: Outremer vs Catana vs Swiss Catamaran

Saw Swiss at a boatshow and in detail work they are not as online. So for me the outremer 51 is to prefere. Or catana 47 and up.
The 47 was better than I thought...

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Old 27-11-2015, 18:07   #38
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Re: Performance 50-55' Cats: Outremer vs Catana vs Swiss Catamaran

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Originally Posted by 2Hulls View Post
Beats me why flying fish fly higher at night. Everybody finds them on deck in the mornings, but you never see them flying that high in daylight.
Dave
One of my friends was hit on his temple by a 30cm (1') flying fish while on watch at night.
The helm of my Salina is around 3m from the water, his face would have been 3.8m from the surface, luckily it hit him on the temple as we were in the middle of the Atlantic...
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Old 28-11-2015, 08:45   #39
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Aft Mast Rig Testing

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Originally Posted by SVNeko View Post
Part of the problem is getting a guinea pig to part with $1m to possibly end up owning a failed experiment. Would be nice to have some real world data on wave piercing nacelles on sailboats (as well as moving the rig slightly aft).
Addressing your concerns about data in support of an aft placed rig, I would call your attention to several postings I made not long ago on this forum:

Aft Mast Ketch Rig
Quote:
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Just posted a summary of some testing that verifies some of the aerodynamic claims I have been making about my aft mast rig.

The Ketch-Rigged Cat
Wind tunnel and CFD investigation of unconventional aftmast rigs

.....CONCLUSIONS
In the present paper an unconventional rig has been investigated in comparison with a standard sloop rig by means of wind tunnel tests. The traditional sloop yacht rig used as a reference is a Comet 51’a Vallicelli Yacht Design & Co 51 feet IMS cruiser-racer. Several unconventional configurations have been tested, all characterized by an “A” shaped stern mast without mainsail in single-jib and double-jib configurations. Aerodynamic data available from experiments have been used to perform some performance prediction at full scale by means of a VPP code.

Both experimental tests and VPP calculation show that the double jib
configuration with overlap gives the best performance and also the same configuration without overlap gives better results in comparison with the standard sloop solution.

Numerical investigation have been carried out using RANS simulation in order to better understand the aerodynamic differences resulting from the experimental tests. Simulation results put in evidence a slat effect in the overlapping jibs configuration leading to more attached flow on the aft jib allowing for an higher pressure drop on the sailplan.
You might pay a visit to that link referenced in the quote above for a description of this test and some photos of the rig configurations tested. With this data, and the Prout example I mentioned before (and a few other examples I could bring up), I think my rig design represents MUCH LESS of a 'failed experiment' possibility. Rather I think it will surprise a lot of folks.

BTW, I'm NOT claiming any 'race wonders', it will be a good cruising rig for older sailors
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Old 28-11-2015, 17:27   #40
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Re: Central Nacelle & Wave Splitter

Beiland, thanks for your time to post. It was interesting.
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Old 28-11-2015, 18:10   #41
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Re: Performance 50-55' Cats: Outremer vs Catana vs Swiss Catamaran

Thanks Derek K., have loved your designs for years. There is so much confusion when you see these fancy condos on hulls at the boat shows. To the original poster...weight....weight....weight...it just kills the performance of multihulls. Trying to get the right setup is critical. Personally, I would never buy one of these boats...not about the money...okay...I lied a little bit...but the performance is everything to me. I can not afford a Gunboat or a large cat like you are looking at. But there are many excellent boats to be had that are used and well designed.

One of the manufacturers you did not mention in your reviews was Chris White's Atlantic 55 cat. Look at the design features on this boat. I hope you are a man of great patience and strong will to even think about buying a French boat. Many threads about how much frustration and near legal actions to get the product you see at a boat show done to specs. D. Kelsell is correct in what he stated about one offs. Good luck to you in your journey.
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Old 29-11-2015, 01:29   #42
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Re: Performance 50-55' Cats: Outremer vs Catana vs Swiss Catamaran

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Thanks Derek K., have loved your designs for years. There is so much confusion when you see these fancy condos on hulls at the boat shows. To the original poster...weight....weight....weight...it just kills the performance of multihulls. Trying to get the right setup is critical. Personally, I would never buy one of these boats...not about the money...okay...I lied a little bit...but the performance is everything to me. I can not afford a Gunboat or a large cat like you are looking at. But there are many excellent boats to be had that are used and well designed.

One of the manufacturers you did not mention in your reviews was Chris White's Atlantic 55 cat. Look at the design features on this boat. I hope you are a man of great patience and strong will to even think about buying a French boat. Many threads about how much frustration and near legal actions to get the product you see at a boat show done to specs. D. Kelsell is correct in what he stated about one offs. Good luck to you in your journey.
You can't lump all the French boats together like that, just as you can't lump together all South African boats whichn the Atlantic 55 is. Now it is an Atlantic 57 produced in Chile.

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Old 29-11-2015, 10:43   #43
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Re: Performance 50-55' Cats: Outremer vs Catana vs Swiss Catamaran

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From the Swiss Cat website;

Design : Sebastien Schmidt
Length of the hulls : 17,0 m
Width : 7,65 m
Construction : Sandwich glass-epoxy carbon reinforcements
Airdraft : 24,3 m
Under water clearance
[Dagger-boards down] : 1,1 m
Under water clearance [
Dagger-boards down] : 3,2 m
(Poids a vide) : 14,0 t
Light displacement : 16,45 t
Total displacement : 17,5 t
NAVIGATION
Double steerind station
Navigation Furuno
Fittings : Harken
Engines : 2x Yanmar turbo diesel
saildrive 75 cv.
Generator : 10 kW
Fuel: 2x 400 L
RIG
Grand – voile : 90 m2
Genois : 75 m2
Trinquette : 31 m2
Gennaker : 95 m2
Carbon mast and boom, kevlar rig
COMFORT
Interior : Comfortable lounge with
two, three or fours on-suite bedrooms
with showers Table seating
8 people
Chart table
U shape Kitchen
Oven with four gas cookers
Refrigerator 190 L
Freezer 90 L
Cold-warm air conditioning
Water : 2 x 250 L
Light displacement 16.45 with a laden displacement of 17.5...bloody heavy for a performance boat of that size. And only just over a ton of payload? The numbers seem odd....
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Old 29-11-2015, 23:42   #44
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Re: more Center Nacelle/Wave Splitter

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Originally Posted by beiland View Post
How about..........

Finally, it is not impossible to think of retro-fitting a wave nacelle concept to an older boat design. Such a project might even be accomplished in stages, a flat plate nacelle first, and then adding the fairing at some later date. And this 'staged' project might be reasonable in cost.
Brian,

this is a very interesting topic and I might even be interested in the retrofit idea and be the 'Guinea pig'.

However, are we not off thread subject?
Would you open a new thread and transfer the most relevant topics?
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Old 30-11-2015, 16:53   #45
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Re: Central Nacelle & Wave Splitter

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Thanks for digging these up. Clearly you have thought about these issues in the past, as have others along the lines of the O Yachts solution. The O Yachts design seems to have adequately addressed the structural issues of having this "third" hull, and even taken advantage of it by designing in a mast aft rig supported by the nacelle and a carbon bulkhead (moving the rig aft is another design departure catching on slowly). The wave "attacking" nacelle seems to exist and work in powercat design. I wonder how it will function on a sailboat. Part of the problem is getting a guinea pig to part with $1m to possibly end up owning a failed experiment. Would be nice to have some real world data on wave piercing nacelles on sailboats (as well as moving the rig slightly aft).
The "guinea pig" has already stepped up to the plate, and a home run was hit back in 2010 when the FreeFlow 46 "Keshi" was launched. The FreeFlow 46 fulfilled all sailing performance, sea keeping and sail handling expectations with the wave piercing bows, nacelle progressive buoyancy and anti slamming, low parasitic drag hull design, central weight disrtibution, and aft mast with wishbone rig. It just all works beautifully and is a testament to Nathan Stanton's design skills.

Keshi has circumnavigated Australia and is sailed mostly every week off Western Australia, often in the Doctor, the strong sea breeze that fills in over there. It has been bashed by very unfriendly seas on all points of sail and came through with a soft ride and very satisfying numbers in all wind speeds.

Helluva design. The best liveaboard bluewater cat I've experienced, so we ordered one.
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