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Old 27-06-2008, 00:29   #1
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pirate Fast is fun

Let's talk about fast cruising cats. What makes them fast, but still good to cruise on? I'll ante up with
a fast version of BigCat, which will make everybody happy by having a more conventional looking rig than my usual:

http://www.dunnanddunnrealtors.com/catamaran88.jpg
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Old 27-06-2008, 10:52   #2
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Let's talk about fast cruising cats. What makes them fast, but still good to cruise on? ...
Needs to be long for speed, comfort, and scalable to fit the human form. Some examples:
Gunboat 66
Schionning Waterline 1750
Chris White Concept 63
any of Dashew's designs sail or power
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Old 27-06-2008, 11:40   #3
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Compromises are inevitable in yacht design.

Hi, Gosstyla - Yacht design is a series of trade-offs. As Tom Follet, Cheers' designer, famously said, You can have accommodations, low price, or speed. Pick two, because you can't have all three. A Conser 47 has a light displacement DL ratio of about 57, and my BigCat Sport has a light displacement DL ratio of about 55. (Loaded for voyaging - ocean crossing with 8 to 10 people, the BigCat Sport DL is 70.)

As I posted on the 'why so many cabins and heads' thread, I prioritize ease of building and low price more that the designers of the fastest cruising cats do. So, medium price, pretty good accommodations, and pretty good speed are my choices. Add in that heavier cats are harder to capsize, too. So, my "Sport" design has narrow hulls for a high Robert's K factor, (35 knot theoretical hull speed on a 65' cat,) somewhat less tankage, somewhat more cramped accommodations, and is otherwise like my BigCat 65.

There is no more off-wind sail area on this design than on the wind on this design, as on all my designs. A boat this fast will usually be going to windward, though, due to the high apparent wind, so that shouldn't affect the speed potential very much. As with all my designs, ease of handling and ease of reefing are of paramount importance. The rig is self-tacking, no sail changing is possible, and the sails can be reefed on any point of sail.

Dollar per knot, I don't think it can be surpassed for speed potential. At at voyaging trim of 41,000#, it has a righting moment of 645,000 foot pounds, and a righting moment of 488,250 foot pounds at a light local cruising displacement of 31,000#. That's a lot of safety for a boat with a center of effort 40' above the waterline and 2,300 feet of sail.

The speed potential of an upside down catamaran is maybe .5 knots, only in the dirrection of the wind and current, which is something to think about. The design's wide overall beam and long waterline make it possible, oddly enough, to get a really good knot per dollar ratio. This is why I like big catamarans.
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Old 27-06-2008, 14:11   #4
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The speed potential of an upside down catamaran is maybe .5 knots.
that's a good one.

Quote:
I prioritize ease of building and low price
Don't want to put you on the spot, but what would you see a BigCat 65, outfitted for a family to go cruising, costing?
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Old 27-06-2008, 15:17   #5
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Don't want to put you on the spot, but what would you see a BigCat 65, outfitted for a family to go cruising, costing?[/quote]

Hi, Lodesman - No problem - I am building a BigCat 65 right now, so my prices are current. $300,000 USD if you build it yourself, at today's prices using vinylester/ quad e-glass, and balsa. My current price for flame retardant vinylester and quad e-glass glass is $2.80 USD per pound, and balsa is $5 to $6.50 a foot. The $6.50 a foot we don't use much of-it's just for bulkheads - 1.5" thick - the light (more expensive,) grade. The deck is 1" light, and the hull topsides is 1.25" of the heavy (standard,) grade. The masts will use $30,000 USD worth of carbon fiber-a special vacuum infusion-friendly carbon fiber material.

My cost includes a high school kid I pay $10.50 USD an hour, and a 35' x 70' tarp shed / blacktop to build with, as well as a laminating table. It doesn't include rent or stuff I have at my shop for Metal Art Sculpture, Steel Sculpture by Tim Dunn, like a forklift, pickup truck, or compressor.

If I have to buy something for the job, it is considered to be in the boatbuilding cost. So, a Hutchins longboard air-powered sander and a Vaccon VP 20-150H-As vacuum generator is in the boat cost, as is a 14' high x 20' wide gantry crane with 2 chain hoists and trolleys, laminating table materials, etc.

I will post technical stuff about building the boat on my website pretty soon. Also, laminating specific info will be on my yahoo group at http://www.groups.yahoo.com/group/ResinInfuse/ . (It doesn't actually have www. in the URL, but this board won't render it as html without the www., and your browser will compensate for the unneeded www.)
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Old 27-06-2008, 18:02   #6
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........, pick two.

I might be mistaken here, but wasn't it Dick Newick who designed Cheers and coined ".................., pick two" ?

Go well,
Kit.
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.....and when the leeward ama takes water over the deck, you should have reefed already.....jim brown.
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Old 27-06-2008, 18:09   #7
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Tom & Dick - no Harry

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I might be mistaken here, but wasn't it Dick Newick who designed Cheers and coined ".................., pick two" ?

Go well,
Kit.
Oh, right - I confused the owner with the designer!
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Old 27-06-2008, 18:24   #8
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Hey Tim,

I just took a gander at your metal art and I think you've got some very nice stuff coming out of your studio. The lines of the silhouettes are quite nice.

Kit.
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Old 27-06-2008, 18:48   #9
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Metal art

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Hey Tim,

I just took a gander at your metal art and I think you've got some very nice stuff coming out of your studio. The lines of the silhouettes are quite nice.

Kit.
Thanks for the kind thoughts, Kit -I'd love to do more marine art, but there isn't much of a market, especially for something that won't do well on a boat due to rust.
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Old 27-06-2008, 23:47   #10
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Being pedantic, Tom Follet was the sailor. I think it was Jim Morris who was the owner

Richard Woods of Woods Designs

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Old 28-06-2008, 03:30   #11
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When you talk fast and comfortable catamarans you look at a Brazapi. After having developped and builded 15 prototypes, it is installed now in new premises (over 10000 sq meter) to be able to build 10 catamarans from each model a year. (they have 410, a new 460 , a500 and a 520. They are working on a 660 now.
They build with an epoxy infusion system with a corecell core.
I visited the premises and sailed the boat. Waw.
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Old 01-07-2008, 23:05   #12
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Chart showing hull beam / speed effect

Terho has posted a couple of very interesting charts on boatdesign.net showing the effects of hull depth, width, and length on speed. Well, on resistance, which limits speed. See

Multi speed/length relationship? - Page 3 - Boat Design Forums

http://www.boatdesign.net/forums/att...2&d=1214403564
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Old 01-07-2008, 23:46   #13
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I wonder if you could convert a day charter cat into a fast comfortable cruising boat and live on the bridge deck instead of in the hulls.

(a) some (not all) are built to commercial standards, so the rigging and systems might be a bit more basic and durable.
(b) they are built to carry load 40,60, 70 people.
(c) they have long thin hulls for speed.
(d) I've read about a number being delivered with impressive speed e.g. a gold coast from St Croix to Hawaii.
(e) could the cost be controlled using a minimalist or used hull, rigging, engines, and fit the interior to suit.

The idea would be to convert the open bridge deck into a large living space with either one stateroom for the owners (guests and/or kids in bunks in the hulls) or perhaps two staterooms on the bridge deck, still leaving lots of room for a great-room, galley, inside helm, etc. I'm not sure what the weight of the interior would be, but if they are designed for say 60 people at 150-175 ave that's 9-10.5 thousand pounds to work with. You would keep the mechanics, storage, etc in the hulls with easy access. Again, if you could control weight of the furnishings, it would luxurious to have a couple pieces of real furniture and lots of elbow room in the saloon.

It's not going to be a super cheap boat, but I'd bet the space and speed would compare with much more expensive cats.

A couple potential platforms:
Gold Coast 57D
2008 Fountaine Pajot Taiti 60 Boat For Sale
1998 Fountaine Pajot Tahiti 75 Boat For Sale
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