Powercat Trawlers

Maltese52 · Dec 14, 2013

Thanks Many,
The Reverse Bow is a growing trend and makes the standard or plumb bow designs look dated. Lots of manufacturers are spending big $$ to update their bow shapes these days to match the trend. Of course like all things, it has its lovers and haters.
That T you speak of is the Forward Crossbeam & Longeron I assume and will be under the Fwd Trampoline area, its actually built of Carbon Fiber and is much lighter than an Aluminum Version. The Striker part sticking up is a perfect place to fly your yacht club pendant or burgee.

Maltese52 · Dec 14, 2013

Ouch.. N47..

Happy to explain though. This Striker could be removed without compromising the strength of crossbeam in the MP52-Trawler and like I said makes a great place for burgee and or searchlight? Check out what the Dashews do on their forward mast for reference...

As for the Windlass actually mounts on the Foredeck area Fwd of Cabin house as is common for almost all catamarans. The anchor and rode can either be deployed and hung off the front of crossbeam or aft just at the Bridgedeck between the hulls. The drawback of having it fwd is the chain and rode runs across the trampoline area and is messy. The Drawback of having it back by Bridgdeck is that you sometimes need a bridle from each bow to keep anchor line in center.

123 · Dec 14, 2013

Maltese52

I don't understand why you call it a Trawler? Why not what it is, a MotorCat.

Cees

Maltese52 · Dec 14, 2013

Cees,
We call it a Trawler Cat because of the cruising speeds its designed for 10-12 knot average cruise and top speed of 15-18 knot depending of power options (75HP to 120HP) all while achieving fuel efficiency better than similar size displacement trawlers.

Most motorcats are high speed 20knot plus and overpowered HP with only slightly better fuel burn then their monohull cousins.

BruceK · Dec 14, 2013

manyboats said:
... that "T" shaped thing dosn't do your boat any favors. I thought at first it was a construction brace of some sort but it's looking more like it's actually part of the boat....

I had a rally car with McPherson slut, sorry, strut, front suspension. We fitted a tubular cross bar, welded to towers mounted on the securing bolts through the inner fenders, to keep the two sides where they were intended. This looks similar, to stop flexing. There is a lot of hull(s) fwd of where they attach to the center section.

Peter B · Dec 15, 2013

Maltese52 said:
Cees,
We call it a Trawler Cat because of the cruising speeds its designed for 10-12 knot average cruise and top speed of 15-18 knot depending of power options (75HP to 120HP) all while achieving fuel efficiency better than similar size displacement trawlers.

Most motorcats are high speed 20knot plus and overpowered HP with only slightly better fuel burn then their monohull cousins.

I reckon you should call it a Crawler Cat, then.

Parmenter · Dec 15, 2013

Peter B said:
I reckon you should call it a Crawler Cat, then.

I reckon they should call it what it is, a sailing boat without a mast.

Its not as if the hull shape had been modified to prevent squat under power or the prop has been protected by a keel.
It still has the carbon front beam and proder for screacher, like a performance sailing cat.

Tidahapah · Dec 15, 2013

Parmenter,
As stated earlier, my sentiments exactly.
It doesn't appear to really be a motor boat except that the mast has been left at home.
Cheers
Benn

Northern Spy · Dec 15, 2013

Off Duty said:
I find something rather ruggedly beautiful about "Sharp Shooter" pictured above. Then again, I drive an old FJ62 Landcruiser and love the 80-90's Suburban's, so maybe that's it?

Same here. But I've got a 77 FJ40 and an 88 HJ61 Land Cruiser.

Daddyo · Dec 15, 2013

Other then the bimini that is one of the prettiest boats ever!

motion30 · Dec 15, 2013

what was learned about the offshore race cats mostly in the 80's is that these boats require different building techniques and materials. the stresses are much different than on v hull. these boats of course are extreme examples , and are capable of well over 150 miles an hour offshore. The advent of Kevlar,'epoxy resins ,new coreing materials and carbon fiber allow these boats to be strong fast and durable.I'm not sure how this relates to the boats that we would be interested in except that new construction techniques must be understood

Off Duty · Dec 15, 2013

Northern Spy said:
Same here. But I've got a 77 FJ40 and an 88 HJ61 Land Cruiser.

Mine is an '89 (US/non-diesel

).
Had a 40 28 years ago. Wish I'd have kept it.

brian eiland · Dec 15, 2013

Daddyo said:
Other then the bimini that is one of the prettiest boats ever!

I'll have to agree with you on that observation.

One thing I noticed is the rather tallish deckhouse in proportion to the hull's topsides, but that was also similarly done with the classic Bertram 31 in a very pleasing manner.
http://www.bertram31.com/

Bertram 31 images

Nomad Willy · Dec 15, 2013

Brian,
The B31 cabin dosn't look tall to me.
Even the prettiest boats often have undesirable details that aren't in good taste. That strip of bright wood on the white cabin side does more harm than good and could even be fixed by just painting it white but there it is. It's hard to believe a designer would create all those beautiful lines and shapes and then do something like that.

I know I know who is going to be the first to say "beauty is in the eye of the beholder"?

However after making that criticism I can see how the strip and the line it makes does help to make the boat look longer and lower. But it could do that even better if it was raised up to the bottom of the window. Still the white part of the cabin is a beautiful shape and the straight strip of bright wood breaks up and does great damage to the white shape. It could have been made to follow the sheer line aft of the break too.

Brian the tall "deck house" seems to work well w the rest of the boat. You probably like the Mathews boats .. I do.

pilothouse king · Dec 15, 2013

Mare's built some nice Power Cats, but slow they were not! I had the 50' Express running 50 mph, and the 54' flybridge pictured doing 30 mph in heavy sea's. 800hp MANS, which were rather fuel efficient as at low speeds they only ran on 4 cylinders, and more opened up as you trottled up, until they would use all eight. The biggest issue on the flybridge model at speed was if you opened up a front panel on the enclosure-ALL the cushions and your hats would suck out the back. Lot's of air is shoved up high when going that fast. Hard to find any on the market now.

Maltese52 · Dec 15, 2013

Peter, Parameter, Tida,
I was out on water yesterday as you should all have been as well

I will try and respond quickly to the remarks about the Maltese MP52-Trawler Cat. The concept of incorporating design elements of sailing cat in trawler cat like the carbon fiber crossbeam and longeron are in fact very practical as they allow weight savings and enjoyable elements from crossover. I have never had any catamaran customers not like the trampoline up forward. With a high bridge deck clearance and trawler speeds of 10-12 knots spray issues are also not an issue. Sure you could fit a composite floor up there but why? nothing beats watching the sea life swim under the bows from the tramps.
As for the hull design comments, if pushing the boat to 15-18 knot max speeds, the squat issues mentioned are non existent. If trying to power the boat for 20+ knot speeds then slight modifications of transom would be needed, but that is not at all what the design parameters were for the Maltese MP52 and you would need a lot more power than the planned 75-120HP and lose all your fuel efficiencies at trawler speeds dragging your planing hull transom around. BTW, Shuttleworth actually used trim tabs to sort this out on his earlier 20+ knot powercats... but I guess you would comment that he doesn't know what he is doing :banghead:

Enjoy some other images I am sharing of other power/crawler/trawler cats. Have to run, its nearly 80 degrees and sunny in december here in California, going out boating!!

Look forward to some intelligent discourse upon my return... :popcorn:

hollywood8118 · Dec 15, 2013

Maltese52 said:
Peter, Parameter, Tida,
I was out on water yesterday as you should all have been as well
I will try and respond quickly to the remarks about the Maltese MP52-Trawler Cat. The concept of incorporating design elements of sailing cat in trawler cat like the carbon fiber crossbeam and longeron are in fact very practical as they allow weight savings and enjoyable elements from crossover. I have never had any catamaran customers not like the trampoline up forward. With a high bridge deck clearance and trawler speeds of 10-12 knots spray issues are also not an issue. Sure you could fit a composite floor up there but why? nothing beats watching the sea life swim under the bows from the tramps.
As for the hull design comments, if pushing the boat to 15-18 knot max speeds, the squat issues mentioned are non existent. If trying to power the boat for 20+ knot speeds then slight modifications of transom would be needed, but that is not at all what the design parameters were for the Maltese MP52 and you would need a lot more power than the planned 75-120HP and lose all your fuel efficiencies at trawler speeds dragging your planing hull transom around. BTW, Shuttleworth actually used trim tabs to sort this out on his earlier 20+ knot powercats... but I guess you would comment that he doesn't know what he is doing

Enjoy some other images I am sharing of other power/crawler/trawler cats. Have to run, its nearly 80 degrees and sunny in december here in California, going out boating!! Look forward to some intelligent discourse upon my return...

View attachment 25702

View attachment 25700

View attachment 25701

View attachment 25706

View attachment 25705

View attachment 25703

View attachment 25704

the first three are fugly....
the next three not bad....
the last has some interesting looks...most likely good/bad depending on the viewing angle

HOLLYWOOD

Parmenter · Dec 15, 2013

Maltese52 said:
As for the hull design comments, if pushing the boat to 15-18 knot max speeds, the squat issues mentioned are non existent.

Almost every other design starts getting it as you push past theoretical hull speed.
I have been on numerous sailing cats in the 30 to 44 ft range that started getting it between 7 and 10 knots depending on boat length.
And how do you know? This is as yet an unproven/untested boat isnt it?

Maltese52 said:
BTW, Shuttleworth actually used trim tabs to sort this out on his earlier 20+ knot powercats... but I guess you would comment that he doesn't know what he is doing

I would actually
He made a design, it was found to have issues.
They added trim tabs after the fact in an attempt to alleviate these issues.
What did he do with his latter designs?

Just about every other designer has aft sections that are a flat or bustle, even on trawler speed designs.
Malcolm Tennant wrote much about this and had many proven powercat designs proving his points.
All of them had double canoe hulls and flat bustle aft.
Most modern power catamarans from other designers use this hullform.
None that are a displacement powercat, have kept a pure sailing cat hullform, at the very least they have reversed the hull rocker into a gradual flat run aft.
I wonder why?

From the late great Malcolm Tennant about this very issue.

So what characterises the displacement hull form? Like monohulls it is usually a round bilge form of minimum wetted surface that depends on its length to achieve high speeds. Unlike the monohulled displacement craft the hull speed of the displacement catamaran is not restricted by the familiar 1.34 times the square root of the waterline length of Froudes Law. I have displacement catamaran designs capable of more than 30 knots with quite minimal horsepower and the more extreme high speed catamaran ferries are achieving 60 knots from very long thin displacement hulls. Like the planning hull cats there are a number of different design approaches to the shape of displacement hulls. When many of the French catamaran companies decided to get into power cats they just fitted larger engines into their sailing hulls, probably because being production boats they had the moulds handy. This is fine as long as you are not going to exceed around 15 knots. Beyond this speed the hulls start squatting and assuming a bow out attitude. The sailing boat hull form is not really suitable for a displacement power cat with any performance or long range aspirations. They are essentially trying to go up hill and require increasingly large amounts of horsepower to move. A number of designers, take a somewhat different approach. They took the traditional trawler displacement hull with its buttock lines sweeping up to a flat surface at the stern, made it much narrower so it had a higher hull speed and then joined two of them together. When in 1979 our design office started looking at power catamaran design we started with the sailing cat hull shape because we knew how fast we could make them go from some twenty years experience of designing sailing catamarans. However to prevent the squatting normally associated with this hull form under power [*] we increased the buoyancy down aft by fitting a bustle with a vertical trailing edge. This worked well but when the first of this type was built in 1983 it proved to be a difficult hull shape to construct as a one off and so the buttock lines were straightened in profile. Instead of kicking the hull lines up toward the surface down aft, as with the traditional displacement hull shape, we drew them in to a canoe stern beneath the water surface. We then placed a large amount of buoyancy above this in the form of a flat section to prevent squatting. Since then this form has been refined by the addition of a concave surface above the propeller complete with some kick down toward the aft end. The distribution of the buoyancy has changed slightly, and the entry has been fined up even further and very early on a “knuckle” was added. Now that this particular form that we developed has proven to be so successful it has become the preferred shape for an increasing number of the worlds displacement catamaran designers [ Including the “wave piercing” designs of Craig Loomes and Roger Hatfield of Gold Coast Yachts]

rjtrane · Dec 15, 2013

P. Are any lines published to illustrate Tennants developments?

Parmenter · Dec 15, 2013

rjtrane said:
P. Are any lines published to illustrate Tennants developments?

Hull lines?

Tenannt went with this and a multitude of other designers followed with similar shapes and now, proven designs

Others, using the hulls based on their proven sailing cat hulls, have made slight changes to the stern as seen, albeit subtle, here

Sailing hull shape from same designer for comparison

Mark Pescott Multihulls : Power Cats

Nomad Willy · Dec 15, 2013

Those look more like 2 torpedos than two hulls. Must have a lot of power as the blade area as well as the dia is maximized.

Those lifting straps are putting a lot of side load on the hulls.

Parmenter · Dec 15, 2013

manyboats said:
Those look more like 2 torpedos than two hulls.

Catamarans are like that

Must have a lot of power as the blade area as well as the dia is maximized.

JD 6081 300hp x 2 for a 20 meter vessel

Finally, is the economy due to DOMINO’s highly performing John Deere 6081 engines? Possibly. Do we always cruise at 10 knots? Most of the time, we do so because we are trolling. Sometimes, we troll at 7 knots on 1 engine only (900 rpm, 7.3nm, 1.8 gph, 12,000 NM range.) At times, and DOMINO much prefers this, we cruise at 20 knots (2,000 rpm, 23 gph, 2,200 NM range) as we did to escape Hurricane Tomas , cross the Gulf Stream , or even to please our pilot on the Panama Canal. Bottom line, in our 19,000 NM of travels we have averaged 10.5 knots, 2.5 mpg. DOMINO 20: VOYAGING UNDER POWER

Those lifting straps are putting a lot of side load on the hulls.

No they're not
Certainly no more than any other vessel
Look at the load path of the straps for further clues.

Maltese52 · Dec 15, 2013

Parmenter,
The topic of squat has been discussed quite a bit on other design forums and as you suggest, some designs experience it more than the other. The topic of wrongly designed power cats has been written about by Kurt Hughes and worth a read as it point out a lot of the problems of non-multihull designer designed power cats. From the start the Maltese hull was designed by a former member of one of the leading multihull design firms in the US and we factored in lots of buoyancy aft due to the decision to make the trawler cat version as well as sailing version using one male plug. We even discussed the necessary modifications needed to modify the hull plug to suit a 20knot plus power cat build.

This was never our intention as we see the fuel efficient trawler cat market as the true growth area in near future. I'd be happy to share how I know that info but let's just say for now that it has to do with my involvement with several of the production cat companies and their dealer network. You don't think a young guy like me goes and develops a boat like the Maltese without a little glimpse of future trend.

So suffice to say, a design like the MP52- trawler whose hull speed "should be close to" 11 knots, will not have squat issues unless someone tries to overpower the boat with bigger heavier engines or try and power over 18knots.
Of course she could easily surf waves at higher speeds and that wouldn't factor into squat scenario.

Would love to see some pics and info on your build one day and share some design differences. That PDF about mistakes of power cats even the 20knot plus ones
http://multihulldesigns.com/pdf/powercatslt.pdf

rjtrane · Dec 15, 2013

P. That pix in the straps illustrates what you've described. A canoe stern leading into the prop. Semicircular sections. And a flat surface to keep from squatting at speed.

We used a similar design on Sunshine except that the flat run aft was designed to be a Cooke of inches above the waterline. The extra surface area would not add drag at slower speeds (6 knots ) but as greater speeds were reached would become immersed and provide a bearing surface to keep from squatting. We never installed enough HP to properly test this idea though tank tests did confirm our thought process.

It's great to see how Tennant did this.

Parmenter · Dec 15, 2013

rjtrane said:
It's great to see how Tennant did this.

Like I said, most seem to be going that way now
While not as obvious in this picture,
Compucraft, which are pretty succesful in Oz and have pleasing, bay cruiser lines.

Waller

More pics here Mike Waller Yacht Design - Waller PC46 Power Catamaran - plywood/timber composite sports fishing cat for amateur builders

Chamberlain designs on this

and its bigger sister

Schionning

More here Alaskan 52

The first pic that the OP put up above,

is a Gold Coaat catamaran from St Croix - line drawing of smaller sister vessels clearly show it as having a similar hullshape as well

Parmenter · Dec 15, 2013

Maltese52 said:
Would love to see some pics and info on your build one day and share some design differences. [/url]

Its been discussed before.
Its a mix of styling from this Brady

and this compucraft

with a generous splash of me thrown into the mix
Built from WRC, polycore, gaboon and epoxy.
with a pair of 80hp Perkins - 55hp Isuzu's would have sufficed, but the Perkies were basically free, so to good a deal to knockback.

Maltese52 · Dec 15, 2013

Looks like nice design... Not all too familiar with the two brands you mentioned out herE on west coast USA but will do some reading upon them. Quick questions: are you sticking with the express (non flybridge) look and whats intended use of boat? Coastal cruising, retirement, live aboard, world circumnavigating, or just trawlering for the ladies...

And lastly what are you expecting speed wise with the 80hp Perkins

Parmenter · Dec 16, 2013

Maltese52 said:
Quick questions: are you sticking with the express (non flybridge) look

At this stage yes, though I may add a low flybridge later if needed.
Or I may add nothing more than an alloy tube frame to stand in, in front of the radio/radar mast with a set of engine controls and sounder for sneaking into a shallow entranced lagoon.
I'll see after I have used her for a bit.

and whats intended use of boat? Coastal cruising, retirement, live aboard, world circumnavigating, or just trawlering for the ladies...

Liveaboard , top half of Australia and into Asian waters

And lastly what are you expecting speed wise with the 80hp Perkins

I would guess high 12's at full noise , maybe even into the teens on the perfect clean bottom, empty, flat calm day
At around 1600 both engines I would hope for high 8's
and freewheeling at 1600 on one possibly 6.

Prop guys seem to think it'll be better, but I doubt it.

Peter B · Dec 16, 2013

Parmenter that craft looks a bit like the new Integrity 440 side on…I like it. The Integrity is my new lust after vessel. Yeah, I know…in my dreams…

440 Sedan - Integrity Motor Yachts

Tidahapah · Dec 16, 2013

Parmenter,
Kevin Dick built some nice cats of a similar design.
he was originally a timber boat builder , one of the last of the old school.
I think I posted a photo of one of his that is based in Gladstone in an earlier post.
Will be nice to see some photos of yours when it comes out from under wraps.
Must be hard not being able to spend all your spare time on it.

I have a mate (he is a builder) building his second cat (sailing , Mike Waller design) and he complains that his work is getting in the way of boat building.
All the best for Xmas and the New year.
Cheers
Benn

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