Power Cats - interesting article

[klee wyck]

Peter again,
In addition, look at my post#10.
The top photo is the PC52 sitting in the water and third one down is DOMINO sitting in the water. The difference in motion comes perhaps less from the part of the boat in the water so much as from when that rising sea will impact the bridge deck. The bottom of the bridge deck (very low and close to the water) on the PC52 is the source of the suddenness of the motion both side to side and fore and aft. It will also be true that the hull form itself is not near as steep as the Tennant, but it would need to be out of the water to show that.

 

[Hippocampus]

KW excellent explanations. Pretty much what I’ve been saying.

 

[mvweebles]

Klee Wyck- I cannot speak to Domino specially. I have no doubt she's a much, much different animal than all but a select few other boats - a "Super-Passagemaker" as McArthur coined. Her length and heft alone make her much different than smaller cats of any style. The only reason I mentioned I wish I could find the pic of the PC52 on the hard is for comparisons sake. What that would look like I do not know, but they are both catamarans so there are bound to be some similarities.

While Domino figured prominently in the cited article, there were other PowerCats, and thr followup articles posted by McArthur cited a dozen or more coastal cruising PCs. A continuum from Super-Passafemaker Domino at the extreme to a readily available mix of several brands suitable for coastal passages. Note that Domino is the only boat mentioned by name (ifbibremeber correctly) - certainly an indicator that she is unique vs the array of production runs of PDQ, Horizon, Jenneau, Leopard, etc.

One item. I have not been in seas heavy enough to hit the bridge deck. The jerkiness I noted was purely from beam seas and the inherent form stability of a catamaran.

Regardless, nice boat. Good topic.

Peter

 

[Hippocampus]

Peter wish you were with me last evening as the admiral and I went for our after dinner walk. On the hard where multiple multihulls. It was real obvious which were built for sea and which for coastal comfort.
Several 60-70’ monsters in CF with wave piercing reverse stems(bows), super fine hulls. No structure more the 6’ in front of the mast except netting and a narrow walkway to get to the roller furlers or foils. Escape hatches below which would be dry if turned turtle. Bridge deck under the house and aft a good 6-9’ above waterline. Daggerboards and on some beyond folding or feathering props retracting. Then several cruisers in the 50-65’ range. Bridgedecks extended further forward and lower, hulls with much more beam, saildrives with engine access only from above. Fixed keels. A totally different thing . I did Bermuda races on a wood epoxy tri and have had the sails up on Gunboats, Outremer and Catana. Have watched the French charter cats struggle in Xmas winds and kite season. Most of the production offerings in power are derivative of those charter cats. Although some are A rated imho they are not voyaging boats. The closest that’s used for charter would be the LEEN power tri. If I was considering RTW on a multihull it would be a Rapido tri. Can be run by one person, constant double digit SOG and seaworthy. In power would prefer a tri with small thin amas over a cat. More easily driven, better behavior in a seaway, less risk of pitchpoling. The South Pacific Islanders knew something. Both cats and tris have much to offer. If you can put up with the decrease in space believe a tri is better choice in power for a sea boat.
Think of it this way. The center bow encounters a wave first then the floats if going into the wave train. Usually regardless of the direction of the wave train it’s one at a time. Given design there’s no increase in parasitic drag between a tri and a cat if judged by displacement. No increase in wetted surface nor frontal plane. Given the tri has a better ride going to windward would choose that. Believe that’s true in power as well. Probably even more so as a righting arm to resist the forces of a sailing rig aren’t required so floats can be quite small.

 

[mvweebles]

I have spent a bit of time on one (1) power cat, the PC52 my friend owns. I've done about 500 nms on her plus a bunch of day/weekend trips. If I were still in the delivery business and someone asked me to deliver one to a destination that didn't involve crossing an ocean - even Florida to California, I'd gladly take the job. But the time I've spent on the uber-posh PC52 taught me one thing, and reinforced another thing: I like old-school displacement monohulls running a jogging speed. And I'm not a fancy-schmancy guy who likes to run a boat off an iPad, SubZero fridges, and lift-mechanism TVs. I still think there's a place for ultra-insulated fridges with water-cooled refrigeration, and a stateroom with lots of opening ports that face forward. That said, there is a LOT to be said about a boat that can cover 200+ nms in a 24-hour period as Domino can (somewhat rare amongst monohulls, though the Nordhavn 57 is a bit of a speedster and will easily average 220nm/day burning 6 gph).

I'm impressed by boats built to cross oceans, but for me, it's more of an academic exercise. I do not aspire to go to places that require an ocean crossing. I have no Gauguin-esque Polynesian fantasy. One of the few places Hippocampus and I really differ is weather forecasting risk. Might be hubris on my part or overly cautious on his part (likely somewhere in between). I view life in rolling 3-day tranches and believe weather risk can be managed accordingly, especially since there is almost always a 24-hour bail-out option, especially if you are willing to reverse course. That philosophy opens a LOT of options for a boat, including my Willard 36, and Kevin Sander's Bayliner 4788. Certainly the PC52.

If I wanted to circumnavigate, my dream boat would be an FPB (or the like such as Mobius, as if I could afford either....). If in a multi, would be Domino or the like, though I don't know much about her but given her achievements, I'll rely on prior opinions. EIther of them would do fine on coastal passages of course, but going through the expense, effort, and time to aquire/build and fit-out for coastal passages is simply not needed for safety in my opinion. Sure, their size and construction would make them more comfortable and yes, more safe, than my Willard, but there's a point where the benefits are marginal, especially compared to the costs.

Long winded way of saying the PC52 and Domino are not the same or even similar except for the obvious. But I am saying the likes of a Horizon PC52 (and I'd imagine the Leopards et al) are perfectly acceptable for the vast majority of cruising most people do - it rarely exceeds mild coastal cruising.

Peter

 

[Hippocampus]

Well said Peter and agree. Even agree about the 3 day windows being adequate in a coastal setting. Only difference is to note all weather is local. Only time we were called overdue was coastal (Maine to Mass). NOAA mislead us. Only time for a knock down with damage was coastal as well (Block island sound at the Long Island sound/Conn side). Both NOAA and the commercial girb products mislead us). Have yet (knock on wood) gotten into troubles ocean.

 

[Hippocampus]

Peter, as an aside, the one thing I think we are totally on the same page is KISS. Like mechanical NA engines, stand alone electronics, redundancy based on mechanical elements not even hydraulics. My current boat doesn’t even have a emergency tiller that bypasses all other ways to steer. Every thing simple and fixable by the owner without outside assistance. Things you can look at and have a good chance to figure out how it works and how to maintain or fix it. But I find more and more that’s no longer true. Wife likes the current boat. It’s truly comfortable and convenient. It performs quite well. Sure ain’t camping but at the cost of complexity. We’re doing cosmetic things today listening to music with the central heat running. On breaks we are both on the internet. No different then a yard work day at the dirt dwelling. But at a cost.

 

[mvweebles]

Hippocampus - take heart on not having an emergency tiller. I remember Chuck Hawley giving a demo at a Safety at Sea prep for a TransPac saying how they were almost always useless when called upon unless they had been prepped and trialed. Too short so lacked meaningful leverage in anything but calm conditions, poor attachment to rudder post, etc.

I struggle with keeping it simple. Easier said than done. Was easier to keep it simple when I was making $5.75/hour and my only means of transportation was a motorcycle (circa 1978).

Peter

 

[Simi 60]

The one thing I never liked about tenants CS hull hull shape was excessive draft.

I spoke to Malcolm when he was in Australia one year as at the time I was nutting out a 55ft powercat to build ourselves along the lines of the cat currently for sale below, but one that had better bed layout and more shade.
This was only meant to be a Pacific Island vessel, passages out there generally no more than 1000nm

https://www.boatsonline.com.au/boats-for-sale/used/power-boats/coral-seas-54-catamaran/271348

It was only going to be a 10 knot boat but needed to draw no more than 850mm, near 3ft as a lot of the coral lagoons we had visited in a previous cat had shallow entries on the right day.

Malcolm agreed that CS was out but said that the earlier variant of cruising powercats were sailing cat hulls and they worked fine.
The next lot had modified the last run aft to flatten and square up the waterline to prevent squatting at speed
But, these hull forms were pretty much restricted to around 14 knots.

Added bonus of the more traditional hull form was much more space in the hull.
Wetted surface area was similar, CS skinny and deep vs traditional wide and shallow

One clearly knifed through the water better but as mentioned above, there are tradeoffs and there are still many commercial and pleasure designers who haven't gone the CS route for various reasons

Kurt Hughes an American designer is one example, this 50fter below is clearly a modified sailing hull
https://www.multihulldesigns.com/designs_stock/50pwrcruisingcat.htm

 

[Hippocampus]

Excellent design. Have absolutely nothing against using sailboat hulls for power. But please note it has virtually all the features of a voyaging sailing cat.

 

[mvweebles]

The one thing I never liked about tenants CS hull hull shape was excessive draft.

I spoke to Malcolm when he was in Australia one year as at the time I was nutting out a 55ft powercat to build ourselves along the lines of the cat currently for sale below, but one that had better bed layout and more shade.
This was only meant to be a Pacific Island vessel, passages out there generally no more than 1000nm

https://www.boatsonline.com.au/boats-for-sale/used/power-boats/coral-seas-54-catamaran/271348

It was only going to be a 10 knot boat but needed to draw no more than 850mm, near 3ft as a lot of the coral lagoons we had visited in a previous cat had shallow entries on the right day.

Malcolm agreed that CS was out but said that the earlier variant of cruising powercats were sailing cat hulls and they worked fine.
The next lot had modified the last run aft to flatten and square up the waterline to prevent squatting at speed
But, these hull forms were pretty much restricted to around 14 knots.

Added bonus of the more traditional hull form was much more space in the hull.
Wetted surface area was similar, CS skinny and deep vs traditional wide and shallow

One clearly knifed through the water better but as mentioned above, there are tradeoffs and there are still many commercial and pleasure designers who haven't gone the CS route for various reasons

Kurt Hughes an American designer is one example, this 50fter below is clearly a modified sailing hull
https://www.multihulldesigns.com/designs_stock/50pwrcruisingcat.htm

The used 2006 boat in Oz - has folding props. Any idea why? Maybe to run one engine at a time to save fuel?

Interesting layout on the Hughes concept boat. Not sure how I'd feel about walking into a hallway from the back deck, but interesting to have the staterooms up higher.

Peter

 

[darkside]

The ride on a thin hulled powercat has to be experienced. KW has covered the lack of heave with the cat compared to a full bodied displacement vessel but I think the lack of deceleration is just as remarkable.
I've never really noticed the snappy motion some describe, perhaps you just get used to it.
One issue is they are hard to turn. Some Tennant designs more or less ignore the rudders until you have some speed. Anything slow and you are on the motors unless you have a lot of space.
The other issue is looks. They can easily look like an apartment block or a wedding cake. Check out most charter cats. To my eye Tennant, Hill and Brady look the best but each to their own.

 

[Hippocampus]

Friend owned a 56’ CF cat. Truly a machine 200+ days work and occasionally nearly 300. Things he didn’t like were regardless of wind direction because apparent wind moves forward as you go faster everything was a beat. But he sold the boat after just 2 years because of docking. As stated above rudders are worthless at low speed. You steer with the engines. Boat will pivot in its own footprint but is very responsive to wind. Any component of wind on the beam made docking extremely difficult. He was usually placed on the T so had room. But for fuel and if placed in a slip he had great difficulty. Often didn’t go out due to concern about getting back in. Guy is a boat broker and does deliveries as well. Very experienced. Cruises him and his bride. Use to never needing a dockhand to catch a line and help. Found he did with this boat. Said even if you pivot you still are drifting down wind. Need to get a line off bow or stern as quickly as possible to power against it to bring the boat in. Said he loved the boat on passage or anchor but not docking. Admittedly this is in the Caribbean trades where docking in 20kts is common.

 

[long-cours.62]

What I don't understand

It is why near all catamarans need more liter than a monohull at "trawler " speed than a mono-hull designed for low consumption

When I discuss with Nigel Irens concerning one project of power trimaran he said to us : " not sure than the drag of 3 hull will be better than 2"
May be also we could thinking than not sure than the drag of 2 will be better than 1 .


When we was in the project phase of "Long-cours 62" we thinking also power catamaran, we visited "Prometa" boatyard to see his Santorini 65 who was in the stage of building the hull.
Unfortunately the alloy hull of 65 feet was to expensive for us, he show to us the "Ligure 50" who was built as a project boat but we want something with a longer wl. We ask to Mr Fèvre for a "smaller "Santorini" at 60'...
Finally we don't find an accord on the hull price , but in my point of view the Santorini 65' it is one of the few who can challenge the consumption of a good monohull.

When I look at the graph posted by "Blue Ligure" forget the name
it seam very rare the catamaran who use 1lt per nm as the Santorini


I have a "croquis" of a longer and more basic "Ligure 50' " somewhere I will post as soon as found it


https://www.hisse-et-oh.com/sailing/santorini-65-catamaran-a-moteur




Santorini 11 kts and 1.65lt nm or 18.15 lt per hour or 4.79 ul gallon per hour at 11kts

 

[Hippocampus]

https://shuttleworthdesign.com/trimaran-32m.html

May want to read this thread

https://www.boatdesign.net/threads/power-trimarans.28511/

Wetted surface is a function displacement. At least for canoe body/bodies. True for one, two or three hulls. Know for sailboats tris are faster upwind and cats downwind. Believe how easily driven is dependent upon multiple factors. Had discussion about the Plymouth 400. This is an autonomous powerboat that made the trip from Plymouth England to Plymouth MA. We have a house in Plymouth MA so talked with a receiving tech there knowledgeable about the boat. Boat powered entirely by solar panels. Was told tri rather than cat was chosen due to greater efficiency at the same payload in open ocean passage making. Not a NA so have no opinion but have heard this from other sources as well.

 

[darkside]

Docking Ahi is ridiculously easy. Well set up with easy access stern quarter cleats. One line on and you are done.
She really sticks to the water, a decent breeze is of no concern.
When we crossed the Atlantic there was one trimaran in the ARC and others like us crossing at the same time. There are really good reasons for that ratio. Spoke to the owner in Trinidad. He said every wave hits you three times.
Ocean cruising isn't all about speed. Plenty of times we chose 8 or 9kn when we could have been going 12. Now the carbon cats cruise at 12kn +, not sure how relaxing that would be.

 

[long-cours.62]

https://www.aluship.com/news/the-mayflower-autonomous-ship-has-reached-north-america/

 

[Hippocampus]

Well said Darkside. Friend said once one line was on -done. Problem was getting that one line on and tight enough to be able to bring the boat along side in available space. Defer to your real world experience. He said getting in between two boats at a fuel dock in a beam wind was difficult. Would use the outside engine to do it once a line was secured. Perhaps his brain never transferred from monohull skill set to multi. Just relaying his feelings.

 

[Hippocampus]

The diversion to Halifax was a diversion from what I understand. Was planned as Plymouth to Plymouth. Plymouth 400 as it honors 400y anniversary of Plymouth MA. Of interest the US doesn’t allow unmanned vessels in coastal waters. So the last little bit into Plymouth was a tow.

 

[Gordon J]

Med mooring

And I imagine they aren’t popular in the Med as they would be charged mooring fees like a super yacht given the beam!

For our 37-foot, 16-8 be m boat we are charged double compared to a similar length monohull.

Gordon

 

[rslifkin]

Well said Darkside. Friend said once one line was on -done. Problem was getting that one line on and tight enough to be able to bring the boat along side in available space. Defer to your real world experience. He said getting in between two boats at a fuel dock in a beam wind was difficult. Would use the outside engine to do it once a line was secured. Perhaps his brain never transferred from monohull skill set to multi. Just relaying his feelings.

I find that many people adapting to twin engines over use the ability to pivot in place. I once saw it described as being like driving 2 singles with massive prop walk tied together.

In many cases, if the boat blows sideways easily in wind, correct maneuvering on approach will get it to pretty much slide sideways to the dock at the end. Just don't go too fast or the arrival gets rather firm. If you can get that part right, it's usually easy enough to drop a person on the dock with a long spring line. Once that's cleated you can pull the boat back in with power and hold it.

In most cases (such as moving to the other side of a guest dock when the wind suddenly changed and picked way up the other night leading to 25 kts and a foot off chop pressing us into the dock) I'm more worried about getting the boat off a dock with wind pinning it than I am about getting onto a dock.

 

[long-cours.62]

Interresting to compare

Here is some data from the most recent of three T

By the numbers:
Distance: 2,661 NM
Time: 10 days, 18 hours
Average speed: 10.3 kts
Fuel used: 2,000 Gal.
Reserve: 600 Gal.

With our former LC62 or Dashew 64


64' 9.7kts , 18.9lt per hour , 1.95lt per nm. lwl 19.4m full 40.8t

Domino 10.3kts , 29.3lt per hour , 2.85lt per nm ? ?


How much your displacement full load ? LW ?
On old advertising I found 22T is right ?



Thanks

 

[Simi 60]

Below are the numbers on the composite cat I listed above
Interesting that the stated fuel burn of 2 litres/NM on a 7.5 tonne vessel is what we get on a 65 tonne vessel admittedly going slower, but same burn per nm with a hell of a lot more comfort, range and autonomy.

Length 54' 0" - 16.46m
Beam 8.14m / 26' 8"
Draft 0.60m / 2' 0"
Displacement 7.5 Tonnes
Horse Power 67 Hp
Fuel Consumption 2 L / NM
Max Speed 12 Knots
Cruise Speed 10 Knots

 

[Simi 60]

The used 2006 boat in Oz - has folding props. Any idea why? Maybe to run one engine at a time to save fuel?

I'd suggest so
We planned on shutting down one on passage on the powercat we started building but were sticking with fixed props.
4 blade fixed props had better efficiency and the saving in dollars over folding bought a lot of extra fuel
The only issue was the freewheeling prop.

Gearbox manufacturer ZF said no dramas for 8 hrs on 8 hrs off shift
Bearing in shaft being water lubricated could have been sorted with a small aquarium pump if required.

Interesting layout on the Hughes concept boat. Not sure how I'd feel about walking into a hallway from the back deck, but interesting to have the staterooms up higher

.

Not a pretty boat, just showing for hull shape
But that style could work for us on 60 ft hulls, with layout like we have now
Living area on bridgedeck panel level
Helm, large king sized cabin and private sun deck on top level
Angled sliding swimstep/davits to get swim platform below water and large tender above first level

 

[long-cours.62]

Yes

Below are the numbers on the composite cat I listed above
Interesting that the stated fuel burn of 2 litres/NM on a 7.5 tonne vessel is what we get on a 65 tonne vessel admittedly going slower, but same burn per nm with a hell of a lot more comfort, range and autonomy.

2lt per nm it is what we need with our actual boat at 7.5kts for 19.30 wl and 59T
With our former Long-cours 62 it was 1.8lt per nm at 9.8kts for 18.25 wl and 32T

 

[long-cours.62]

forr the lubrification

I'd suggest so


Gearbox manufacturer ZF said no dramas for 8 hrs on 8 hrs off shift
Bearing in shaft being water lubricated could have been sorted with a small aquarium pump if required.

For lubricate the shaft not in service we fit at T with a valve and two no return valves

 

[klee wyck]

With our former LC62 or Dashew 64


64' 9.7kts , 18.9lt per hour , 1.95lt per nm. lwl 19.4m full 40.8t

Domino 10.3kts , 29.3lt per hour , 2.85lt per nm ? ?


How much your displacement full load ? LW ?
On old advertising I found 22T is right ?



Thanks

Easy LC, everything depends upon conditions and speed. It also pays to treat published numbers with some skepticism in my experience.

The set of numbers in the post you are referring to was the third Transpac for DOMINO. If you look at the dates, you will find it corresponds in time to hurricane Willa travelling in the region. The trip was uphill and stretches of it were run faster than anyone would normally run due to weather avoidance.

Below are corresponding numbers from her first Transpac and in the other direction. Galapagos to Marquesas(French Polynesia).


By the numbers:
Distance: 2,885 Nautical Miles
Duration: 13 days, 3 hours
Speed: 9 knots
Fuel burn: 1,200 gallons


That is 1.57 l/nm LWL is 20 meters
She is about 34 T reasonably laden.
And....when you get there she has a back porch to die for, lounging in your tropical destination.

 

[long-cours.62]

Thanks for the info

Easy LC, everything depends upon conditions



Below are corresponding numbers from her first Transpac and in the other direction. Galapagos to Marquesas(French Polynesia).


By the numbers:
Distance: 2,885 Nautical Miles
Duration: 13 days, 3 hours
Speed: 9 knots
Fuel burn: 1,200 gallons

That is 1.57 l/nm LWL is 20 meters
She is about 34 T reasonably laden.

It means she is lot of heavier than said on the advertising


And is consumption in the "right" way

9kts 1.57lt per nm lwl 20m 34T Domino

9.8kts 1.78lt per nm lwl 18.25m 32T Long-cours 62



It means similar consumption for a mono-hull and a catamaran.
And probably our could be better if one engine.

May be Domino is over loaded for her original drawing ?
Because the Santorini had a better consumption ( it is one of the reason we look at her 25 year ago) but his weight was only around 20t for 65'.

 

[klee wyck]

It means she is lot of heavier than said on the advertising


May be Domino is over loaded for her original drawing ?
Because the Santorini had a better consumption ( it is one of the reason we look at her 25 year ago) but his weight was only around 20t for 65'.

Domino could well have weighed 22T coming out of the yard-likely did.
But autonomy, as required for passage, required fuel, provisions, and spare parts. Domino carries 12 tons of fuel alone which will drop her waterline by a full foot.

There is no free lunch here due to laws of physics. Your Long-course takes advantage of high LB ratio and low LDLin its hull form, And, it is made of a great light weight material.

However there is really no way a monohull with an LB around 4 is going to compete with one with an LB of 12 in terms of ease through the water. Beyond that, energy lost is also a function of wave making and weight will play a major role there. The 'stuff' you need for passage making adds up to considerable weight even where build materials have been considered carefully.

You could think of DOMINO as a 65-foot boat. The reality in terms of volume and weight is that she is a 52-foot boat on 130 feet of hull. That is what result in fast and efficient in my view.

If this link below works, it is worth a read. It is the design brief around an alloy monohull that I really lust after. But, I do not expect it would be as efficient as DOMINO.

https://www.google.com/url?sa=t&rct...4-pdf.98440/&usg=AOvVaw2R4Tux1CRE_GFkSJjHr6Y6

YMMV

 

[bowball]

Interesting boat, Ned 70.

With that little draft and weight, how would it be in a difficult sea?

And where do they place a reasonable sized tender? Or any tender.

Be a good European canal or river boat?