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Old 02-05-2022, 08:25 PM   #1
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40' displacement powercat

The concept:
A robust coastal cruiser, comfortable for a week at a time, and longer on occasional expeditions.
The boat is also my apartment when I work in Auckland.
Because of that I head out to the Hauraki Gulf islands to overnight solo, one or two nights a week.

We wanted:
1. Easy to handle solo, even in the 20 to 30kn winds we often get down here
2. Had to fit in our well located 12m marina berth
3. Good cockpit space for fishing and diving
4. Good fuel efficiency, particularly at higher speeds
5. Walk around master and good size guest berth
6. Separated shower and heads
7. Twin helm seats
8. Reverse sheer windscreens to keep the sun out of the boat
9. Good cockpit seating
10. Ability to sit on the beach

We are catamaran fans having circumnavigated a Grainger 46 a few years back.
Since then we have had two Roger Hill planning alloy powercats.
This time we wanted to try displacement for softer ride and better efficiency and range.
We tweaked the accommodation layout on one of Rogerís proven hulls and asked him to develop a GA.
We then engaged Alloycats to do the build.
Alloycats had built our last two powercats (we bought those two used) and are 2 miles from our house.

The main problems for powercats are:
a. you have to be careful with weight
b. engine access is usually bad

Roger added 50mm more draft for our build to cope with the 1000l fuel and 400l water we wanted.
We also went with twin heads and showers.
Itís nice for guests to have separate facilities but mostly it allows an access door in the rear wall of the shower.
That allows easy access to the front of the engine where service items like the alternators and raw water pumps are.
The rest you get to from a deck hatch.

The renders arenít quite where we ended up but we started with this.

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Old 02-05-2022, 09:30 PM   #2
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Wow!! That looks amazing!!
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Old 02-06-2022, 01:43 PM   #3
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A video of one of the earlier models. From the 45s mark there is some nice drone footage of it underway.



That one had twin Hyundai 270hp and this is the fuel burn achieved.

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But this is a builders thread so here we go.
Roughly a year ago now.

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Old 02-06-2022, 02:53 PM   #4
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Quote:
Originally Posted by darkside View Post
A video of one of the earlier models. From the 45s mark there is some nice drone footage of it underway.



That one had twin Hyundai 270hp and this is the fuel burn achieved.

Attachment 125746

But this is a builders thread so here we go.
Roughly a year ago now.

Attachment 125747

Attachment 125748
Wow!!
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Old 02-06-2022, 03:10 PM   #5
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Looks great. Is that video a rendering or real? (Seeing on my iPhone).

What happened if you stretch it to 50í plus? Can you get larger stateroom and better engine access? How much beam does that add?

Looks very efficient and well done for space.
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Old 02-06-2022, 03:41 PM   #6
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Beautiful and inspiring! Can't quite tell whether there is a center nacelle to reduce / deflect pounding beneath the bridge deck.
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Old 02-06-2022, 04:34 PM   #7
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40' displacement powercat

when will the boat be finished? Are you happy with the builder?
Which power plant did you choose the Yanmar 4lv or the Hyundai 270s as I noticed the owner of MAGGIE(another roger hill 12m cat) used the Hyundai V6
The changes you have made to the original design are fantastic, well done.
contemplating one myself
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Old 02-06-2022, 05:18 PM   #8
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Yes Roger designs larger displacement cats, this one around 50'

https://www.powercatsnz.com/index.cf...ull-power-cat/

Yes there is a small nacelle

My guess around 3 months to launch but we will see.
The build is more or less as I expected, better in some areas, not quite there in others.

I really liked the idea of a small 6 cylinder Hyundai for smoothness but the reported superior Yanmar support won the day. This will be my eighth and ninth Yanmars so I'm getting to know them a bit.
We did order 4LVs but couldn't get any.
We ended up with old school mechanical injection Yanmar 4LHA-STP
With the 4LHA we get 25% more capacity for the hp and with that probably better long term reliability.
We loose a bit of efficiency, we don't get instant fuel burn readings and the bigger capacity engines weigh 30kg more (each)

I've seen Maggie anchored out but haven't met the owner.
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Old 02-06-2022, 06:05 PM   #9
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Fantastic thread - great to see what you're doing and why. Love to see how the design matches your needs.
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Old 02-11-2022, 02:46 PM   #10
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More shots of the build.

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Lots and lots of welding.
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Old 02-11-2022, 02:51 PM   #11
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A few more. Hopefully they end up the right way up.

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Old 02-11-2022, 02:55 PM   #12
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Great vessel. Following😁
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Old 02-11-2022, 04:16 PM   #13
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Nice!
You've got to love a well-conceived plan.
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Old 02-11-2022, 04:30 PM   #14
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Fantastic design and build, how long has the build taken so far?
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Old 02-11-2022, 04:32 PM   #15
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How is it that you can install mechanical engines in New Zealand? I would think they would required strict emissions compliance. Perhaps Tier III or IMO 3
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Old 02-11-2022, 05:18 PM   #16
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Just ticking over a year so far.....

No emissions rules for off highway in New Zealand. Same as Australia as it happens.
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Old 02-11-2022, 05:58 PM   #17
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Quote:
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How is it that you can install mechanical engines in New Zealand? I would think they would required strict emissions compliance. Perhaps Tier III or IMO 3
Quote:
Originally Posted by darkside View Post
Just ticking over a year so far.....

No emissions rules for off highway in New Zealand. Same as Australia as it happens.
Glad Mako asked the question and you answered.

I have seen non EPA or IMO engines for sale in Australia and maybe New Zealand which made me wonder if the webpages were correct or just out of date.

Thanks,
Dan
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Old 02-12-2022, 08:07 PM   #18
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Plenty of checking to get the front screens set up correctly.

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Detail starting on the stern step

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Old 02-13-2022, 01:45 AM   #19
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looking good, you must be getting excited as it nears completion!!
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Old 02-13-2022, 10:27 AM   #20
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I realize that the word "displacement" means something entirely difference in the catamaran world. 25 knots with minimal fuel tankage hints at quite a different SOR than most people who buy/build displacement monohulls. Still, it's rather amazing that you can reach that speed with moderate hp.
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