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Old 03-07-2016, 11:02 AM   #3101
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Rustybarge,
All the cats seem to have a bull dog ready for action look about them. And I just don't like cats. There are exceptions though. And of course they are often a PITA to tie up at a marina.

Are they the ultimate "stiff" boat? Jerk this way and that depending on the water under them? I don't think I've ever been on a cat. It's common knowledge that cats don't roll but being abeam to a short steep sea I certianly can imagine it.

I Designed and built a cathedral hull that was more than a distant cousin to a trimaran. So my head isn't totally void of multi-hulls and it wasn't exactly a swan. I liked it but I was the creator. That has an interesting ring to it.

One place I would'nt want to be in a cat is broadside near the top of a big breaking wave. No option to slide sideways toward the trough. If one can trip on a chine then I sopze it's possible to trip on a half-hull.
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Old 03-07-2016, 11:04 AM   #3102
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I'm investigating the idea of a steel cat as a home build project . ( yes I know that's an oxymoron; steel and catamaran should never appear in the same sentence)
I think you underestimate. Certainly there are an almost infinite supply of plans for aluminum cats, but there are steel workboat catamaran designs as well. If you limit your speed to moderate or slow (basically trawler speed) then you'd find them to be efficient, heavy (in a good way), stable and with great load capability.

But you most likely would be limited to no shorter than the 40+ ft size range. Perhaps check out the boatdesign.net forum for designer feedback.
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Old 03-07-2016, 01:00 PM   #3103
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Looks like Bruce Roberts likes either Fiberglass or Aluminum for his cat kits...

https://www.bruceroberts.com/CATAMAR..._BOAT_KITS.htm

For a work or explorer style boat, I wouldn't mind steel.
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Old 03-07-2016, 01:25 PM   #3104
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Rustybarge,
All the cats seem to have a bull dog ready for action look about them. And I just don't like cats. There are exceptions though. And of course they are often a PITA to tie up at a marina.

Are they the ultimate "stiff" boat? Jerk this way and that depending on the water under them? I don't think I've ever been on a cat. It's common knowledge that cats don't roll but being abeam to a short steep sea I certianly can imagine it.

I Designed and built a cathedral hull that was more than a distant cousin to a trimaran. So my head isn't totally void of multi-hulls and it wasn't exactly a swan. I liked it but I was the creator. That has an interesting ring to it.

One place I would'nt want to be in a cat is broadside near the top of a big breaking wave. No option to slide sideways toward the trough. If one can trip on a chine then I sopze it's possible to trip on a half-hull.
This FP 55' is quite pretty...?






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Old 03-07-2016, 01:27 PM   #3105
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I think you underestimate. Certainly there are an almost infinite supply of plans for aluminum cats, but there are steel workboat catamaran designs as well. If you limit your speed to moderate or slow (basically trawler speed) then you'd find them to be efficient, heavy (in a good way), stable and with great load capability.

But you most likely would be limited to no shorter than the 40+ ft size range. Perhaps check out the boatdesign.net forum for designer feedback.
Have a look at this beast ... Steel Catamaran, Fife - FAFB
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Old 03-07-2016, 01:30 PM   #3106
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I'm not too keen on that waterline window. I am sure it's well braced or even multi-pane but still too big near rough water. I've also seen egress windows on the inner hulls where it can be better protected. Also would prefer a hard top rather than canvas over the fly(ing) bridge.
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Old 03-07-2016, 01:33 PM   #3107
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Looks like Bruce Roberts likes either Fiberglass or Aluminum for his cat kits...

https://www.bruceroberts.com/CATAMAR..._BOAT_KITS.htm

For a work or explorer style boat, I wouldn't mind steel.
That's a nice cat. The big advantage of steel is its dead easy to weld, whereas alloy is a job for a professional.

The big disadvantage is the weigh: 2mm steel plate = 6mm alloy! I believe 3.5mm is the thinest plate that doesn't distort with the heat of welding.
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Old 03-07-2016, 01:34 PM   #3108
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Have a look at this beast ... Steel Catamaran, Fife - FAFB
That is definitely in the BAB class. It is purpose built for work and little else.

What's the black line on the port quarter?
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Old 03-07-2016, 01:38 PM   #3109
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I'm not too keen on that waterline window. I am sure it's well braced or even multi-pane but still too big near rough water. I've also seen egress windows on the inner hulls where it can be better protected. Also would prefer a hard top rather than canvas over the fly(ing) bridge.
Low windows in the topsides seem to be the height of fashion at the moment; everything from small 25' planing boats to superyachts have them....

....nice for daytrippers going out for a picnick on a calm summers day.
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Old 03-07-2016, 01:41 PM   #3110
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That is definitely in the BAB class. It is purpose built for work and little else.

What's the black line on the port quarter?
I think its to keep the beam trawl from hitting the hull when its dumped onto the deck.
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Old 03-07-2016, 01:45 PM   #3111
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I think its to keep the beam trawl from hitting the hull when its dumped onto the deck.
Why would the trawl be on the forward port quarter? I would have assumed the trawl comes in astern.

On the starboard the dry stack exhaust goes out of the hull and up above the house. Looks like retrofit plumbing...
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Old 03-07-2016, 01:52 PM   #3112
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Why would the trawl be on the forward port quarter? I would have assumed the trawl comes in astern.

On the starboard the dry stack exhaust goes out of the hull and up above the house. Looks like retrofit plumbing...
It states that the alloy hard top was recently added to give shelter; diy is the norm on all these commercial trawlers , they can't afford to pay professional fabricators.
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Old 03-07-2016, 02:04 PM   #3113
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Greetings,
Mr. R. I like cats either recreational or commercial BUT the main gripe I have about them is lack of space to work around the engines. IF one could replace that dinghy storage (2nd picture, post #3104) with a single engine coupled to, say hydraulic or electric drives I just might take out a mortgage on the farm.
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Old 03-07-2016, 02:30 PM   #3114
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Greetings,
Mr. R. I like cats either recreational or commercial BUT the main gripe I have about them is lack of space to work around the engines. IF one could replace that dinghy storage (2nd picture, post #3104) with a single engine coupled to, say hydraulic or electric drives I just might take out a mortgage on the farm.
Dual electric drives would be a great idea, and simply have a genset (or two) aboard for propulsion and everything else. The nice thing is that no transmission would be needed, and reverse would be simply reversing polarity on the motors.

Many cats have prop tunnels or pockets so they can sit on their bottoms without harming the props...
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Old 03-07-2016, 02:40 PM   #3115
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Greetings,
Mr. R. I like cats either recreational or commercial BUT the main gripe I have about them is lack of space to work around the engines. IF one could replace that dinghy storage (2nd picture, post #3104) with a single engine coupled to, say hydraulic or electric drives I just might take out a mortgage on the farm.
Another plus point is the privacy of the two cabins on opposite sides of the hulls.

One engine would work well, but would need an underwater pod to stop the prop sucking air ( ventilation) , which would cause extra drag; twins might be more efficient.

A general rule of thumb is a cat on outboards has about the same mpg as a monohull on diesels; cats have about 40% less drag.

Hmmm....
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Old 03-07-2016, 03:04 PM   #3116
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Local Army Corps of Engineers catamaran work boat:



Seen last month at the northern end of Carquinez Bridge while the photo was taken several years ago off Richmond. Used to collect flotsam?
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Old 03-07-2016, 03:09 PM   #3117
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Greetings,
THREAD DRIFT ALERT!!!! Mr. R. "...an underwater pod to stop the prop sucking air ( ventilation)" Not if, as I suggested, an electric or hydraulic "motor" (much smaller physical dimensions and much less need for service access) was put in each pod in lieu of the diesel engines that are usually shoehorned in. The main, single engine could be amidships on the aft deck allowing 360* access for service purposes.

One would still enjoy the separate cabin areas, massive saloon and have all the advantages of a diesel cat without the contortions for performing simple maintenance at the aft most end of each hull whilst standing on your head and potentially soiling the bedsheets...
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Old 03-07-2016, 03:43 PM   #3118
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Local Army Corps of Engineers catamaran work boat:



Seen last month at the northern end of Carquinez Bridge while the photo was taken several years ago off Richmond. Used to collect flotsam?
Serious piece of kit, looks the business !
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Old 03-07-2016, 03:44 PM   #3119
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QUOTE=Rustybarge;421921]This FP 55' is quite pretty...?

Well sir if you could get rid of the black spots on the hull sides (windows?) and the cover over the FB. Indeed quite pretty then. Bottom pics no chance.

Interesting though that the hulls seen in the bottom pic are so beamy. Must be a very capable boat.

Mark even less pretty that one. As you say though "looks the business".






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Old 03-07-2016, 03:48 PM   #3120
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Greetings,
THREAD DRIFT ALERT!!!! Mr. R. "...an underwater pod to stop the prop sucking air ( ventilation)" Not if, as I suggested, an electric or hydraulic "motor" (much smaller physical dimensions and much less need for service access) was put in each pod in lieu of the diesel engines that are usually shoehorned in. The main, single engine could be amidships on the aft deck allowing 360* access for service purposes.

One would still enjoy the separate cabin areas, massive saloon and have all the advantages of a diesel cat without the contortions for performing simple maintenance at the aft most end of each hull whilst standing on your head and potentially soiling the bedsheets...
Aha, 3 engines. Van de valk in Holland make large 24mtr alloy monohull's with this arrangement and say it is as efficient as a similar twin.

How about a super7 550hp outboard midships instead of a diesel; light, tilts, easy to service.
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