Power Trimarans?

[CatBuilder]

You don't see so many power trimarans. Does anyone know of some example power trimarans that are either:

a) Built to plane with more efficiency

or...

b) Built as extremely efficient trawlers

If there are none that fit these descriptions, what is it about trimarans that prevent one from making them behaving something like a power cat?

Also, in the same general theme, can anyone describe the differences between a power trimaran and a very narrow beam long waterline monohull? Could the long waterline narrow beam mono be used as an efficient trawler?


Sorry... I'm new to power boats and new to the area of designing boats. I come from a background of sailing monos and cats.

[apex1]

very narrow beam long waterline monohull? Could the long waterline narrow beam mono be used as an efficient trawler?


http://dashewoffshore.com/fpb_first.asp

when you´re through with it, you´ll likely convert to the motor community (like me). 38 years ago

Regards
Richard

[CatBuilder]

Thanks, Richard. I was already a fan of that one. I feel a conversion coming on and have found more than enough reading in the long skinny boat threads on here. I'll just keep on doing the reading until I can ask some better questions.

[Doug Lord]

Here are a few--Ilan Voyager and a couple others:

[Rick Willoughby]

You don't see so many power trimarans. Does anyone know of some example power trimarans that are either:

.

Attached images show the best known power tri. Currently holds the fastest round-the-world power boat record. Only a few days slower than the big sailing tris although it took a slightly shorter route and avoided the really heavy weather.

Rick W

[FAST FRED]

Once again the real question is the actual USE the boat will be called on to perform.

For someone wishing to do a FAST efficient long cruise the skinny monohull, with or without "training wheels (tri) would be first choice.

BUT as a living , entertaining platform, mere area is a plus , so a big box cat, regardless of the efficiency or deep ocean hassles is usually selected.

Mental Masterbation is great fun , but a boat to be USED , needs to know realistically, HOW it will be used.

FF

[CatBuilder]

Thanks, Fast Fred. I saw all of your posts in the narrow boat thread.

I'm looking to use the boat coastal (near shore) only. I'm also using it as a liveaboard/coastal cruiser for two people.

If I might make a comparison to RVs, I would be looking for a Road Trek RV instead of a Class A motorhome.

(Road Trek is a van all tricked out to be an RV. Not much space, but fits anywhere, great on gas, etc...)

Once again the real question is the actual USE the boat will be called on to perform.

For someone wishing to do a FAST efficient long cruise the skinny monohull, with or without "training wheels (tri) would be first choice.

BUT as a living , entertaining platform, mere area is a plus , so a big box cat, regardless of the efficiency or deep ocean hassles is usually selected.

Mental Masterbation is great fun , but a boat to be USED , needs to know realistically, HOW it will be used.

FF

[marshmat]

Hi CatBuilder,

Looking at the ideas you started off with at the top of the thread:

"a) Built to plane with more efficiency"

Well, there have certainly been some interesting trimaran-like power boats that do "plane", in a manner of speaking. There are those "gull wing" or "cathedral" hulls you see on some '60s and '70s bowriders, and which survives, in spirit, in today's Boston Whalers. But there's a strong argument that the shape is just a deep-V with a really huge reverse chine, not a trimaran. Also on the radar would be larger surface-effect craft (M-ship, etc.) although these aren't "planing" hulls in the sense we normally think of.

Really, though, the power trimaran's advantages- notably its low drag and its ability to slice through waves without much of a fuss- are largely a function of the fact that its main hull is much longer and narrower than a monohull boat of the same weight. That long, narrow shape isn't really conducive to the low bottom loading and flat running surface that leads to efficient planing. And once on plane, dynamic forces take over that would likely relegate trimaran outriggers to a role somewhere between "questionable" and "redundant". (Of course, this is talking about something that actually looks like a trimaran, 3-point hydros are a different matter).

And the next idea,
"b) Built as extremely efficient trawlers"

Well, as Fred has pointed out, we really need to take a close look at how the boat will be used. When we're looking at powerboats, we don't need the enormous initial stability that is so desirable in a sailboat. Thus, the sailor's main rationale for having outriggers is missing from the powerboat realm.

So, we need to consider what other characteristics would lead us to a tri-hull configuration for a power yacht. Perhaps we want a long, narrow hull for efficiency and to slice through waves without pounding. We want a decent turn of speed, substantially more than most monohulls can do with a given engine and fuel burn rate. And let's say we also want a fair chunk of deck space, with easy access to the water, places to dump kayaks and water toys, etc. A tri configuration might start to look appealing here. The price that is paid is a more complex structure- an extra two hulls, plus crossbeams- and a package that, unless it folds somehow, will cost you dearly if you need to rent slip space.

Now, if we don't intend to be goosing the throttle to well past the so-called "hull speed", and the huge trampoline/side deck area of a tri isn't a "must have" feature, and a roomy interior is more of a concern- perhaps sticking with a single hull makes more sense.

But what it really comes down to is this: What characteristics do you need for the way you plan to use the boat?

(As an aside, I've been going through the power tri vs. planing mono debate myself over the last few months, albeit for a somewhat different use profile- " http://www.boatdesign.net/forums/projects-proposals/trailer-cruiser-revisited-trimaran-27032.html ." The tri's lower power requirements, resulting longer range, and huge usable side-deck area were the deciding factors there. But, ultimately, you have to weigh the trade-offs for your own project.)

[CatBuilder]

Thanks, Marshmat.

The more I've been reading, the more I've realized "planing" was the incorrect word. Also, the more I read the more I realize that yes... why does this have to be a trimaran?

Coming from the sailing world, my gut (not math) tells me that I need a lot of lateral stability. I'm very weak in understanding powering stability for trawler-like displacement hulls.

So could a 40 foot power boat with a 7 foot beam be built in such a way as to be stable at sea? I'm not sure if that hull form (with a sharp, plumb bow) would even qualify as something you could use as the center of a tri as it might be too beamy?

Would that type of hull make sense as a mono rather than a tri?

Lastly, although I have no end to my questions in sight, I'd like to answer the ones you asked about usage. You were very close!:

1) I'm looking at long, slender boats for efficiency. Speed (to someone coming from sailing) is 8 knots. 10 knots would be incredible! Most of all, I'd like to be able to use low horsepower to achieve fuel efficiency by reaching 8 knots using the minimum of fuel consumption.

2) I'm presently sailing a catamaran. I sure love the catamaran, but it's an enormous build cost and complexity as a build project. I've refit enough boats to understand what it takes to build an interior and put together systems. However, I absolutely love the initial stability of a catamaran over a mono due to its beam. This is comfortable while underway but even more comfortable at anchor, which is where a boat I come up with will be 90+% of the time. I am another idiot who is thinking about a mono with "training wheels" rather than a real trimaran, I think. :D I see "trimaran" as a way to take a mono and get the stability of a cat. Am I far off?

3) I'd like to design the boat to be able to cross oceans at 8 knots, but the main requirement is size for portability, access to EU canal systems, etc... If I could develop a boat that could both be an ocean crosser *and* a narrow boat of 40 foot length and 7 foot beam, that is what I'm after, ultimately.

4) Lastly, as an add on, I'd sure like to have a kite sail to fly to save on power when going downwind in conditions that warrant it.

Those are the intended uses. Coastal cruising a must, ocean crossing a "nice to have." If I can achieve both, great! If it's just a mono, great! I'm a complete design novice, but a very experienced sailor/liveaboard.

I know exactly what I *need* out here, but I don't know if it's commercially available, if the hull or a design is available, or if I should design it myself, which I am strongly considering.

I was to build a cat, but my wife had a change of heart, so I will follow her change of heart and come up with a boat that fits those above criteria. Any help or advice would be welcome. Also, my screen name doesn't fit my situation! ha ha

Hi CatBuilder,

Looking at the ideas you started off with at the top of the thread:

"a) Built to plane with more efficiency"

Well, there have certainly been some interesting trimaran-like power boats that do "plane", in a manner of speaking. There are those "gull wing" or "cathedral" hulls you see on some '60s and '70s bowriders, and which survives, in spirit, in today's Boston Whalers. But there's a strong argument that the shape is just a deep-V with a really huge reverse chine, not a trimaran. Also on the radar would be larger surface-effect craft (M-ship, etc.) although these aren't "planing" hulls in the sense we normally think of.

Really, though, the power trimaran's advantages- notably its low drag and its ability to slice through waves without much of a fuss- are largely a function of the fact that its main hull is much longer and narrower than a monohull boat of the same weight. That long, narrow shape isn't really conducive to the low bottom loading and flat running surface that leads to efficient planing. And once on plane, dynamic forces take over that would likely relegate trimaran outriggers to a role somewhere between "questionable" and "redundant". (Of course, this is talking about something that actually looks like a trimaran, 3-point hydros are a different matter).

And the next idea,
"b) Built as extremely efficient trawlers"

Well, as Fred has pointed out, we really need to take a close look at how the boat will be used. When we're looking at powerboats, we don't need the enormous initial stability that is so desirable in a sailboat. Thus, the sailor's main rationale for having outriggers is missing from the powerboat realm.

So, we need to consider what other characteristics would lead us to a tri-hull configuration for a power yacht. Perhaps we want a long, narrow hull for efficiency and to slice through waves without pounding. We want a decent turn of speed, substantially more than most monohulls can do with a given engine and fuel burn rate. And let's say we also want a fair chunk of deck space, with easy access to the water, places to dump kayaks and water toys, etc. A tri configuration might start to look appealing here. The price that is paid is a more complex structure- an extra two hulls, plus crossbeams- and a package that, unless it folds somehow, will cost you dearly if you need to rent slip space.

Now, if we don't intend to be goosing the throttle to well past the so-called "hull speed", and the huge trampoline/side deck area of a tri isn't a "must have" feature, and a roomy interior is more of a concern- perhaps sticking with a single hull makes more sense.

But what it really comes down to is this: What characteristics do you need for the way you plan to use the boat?

(As an aside, I've been going through the power tri vs. planing mono debate myself over the last few months, albeit for a somewhat different use profile- " http://www.boatdesign.net/forums/projects-proposals/trailer-cruiser-revisited-trimaran-27032.html ." The tri's lower power requirements, resulting longer range, and huge usable side-deck area were the deciding factors there. But, ultimately, you have to weigh the trade-offs for your own project.)

[apex1]

Have a look here:

http://www.kastenmarine.com/coaster40.htm

go down to "ocean trawler"

If affordable choose this one:

http://www.kastenmarine.com/monsoon46.htm


Both are capable cruisers and fit in even the smaller French canals.

To get a better understanding about the long and slender philosophy go here:

http://dashewoffshore.com/dashew215.asp


Regards
Richard

[Rick Willoughby]

So could a 40 foot power boat with a 7 foot beam be built in such a way as to be stable at sea? I'm not sure if that hull form (with a sharp, plumb bow) would even qualify as something you could use as the center of a tri as it might be too beamy?



I have been playing around with similar ideas to you. My object is coastal and river cruising. I want something trailerable so I am not going to 40ft. I did go through a phase of looking at a 3-part hull to get length.

Anyhow someone gave me the idea of what I call a faux-tri. The boat is a long slender monohull underwater, a trimaran on the waterplane and a monohull above the water. See attached image.

My aim is to do 8kts with less than 1kW. This requires an ambitious weight target but not impossible. The boat is intended to have both solar and wind energy collection, battery energy storage and electric motor propulsion.

This hull form will achieve the best form stability you can get for a 7ft beam. It is easy to make self-right by placement of the heavy components like batteries.

Whether it works for you depends on what you want to cram into it. A 40ft boat could be made quite comfortable but the 7ft beam is a serious constraint for getting nice spaces. Much better than the hull of a cat but 10ft would be nice.

The idea is not new. This link shows something bigger but of similar concept:
http://www.royalnavy.mod.uk/triton/*/changeNav/3533/noRedirect/1

Rick W

[Crag Cay.]

Both are capable cruisers and fit in even the smaller French canals.
Apart from being too deep and too tall. Hopefully you'll run aground before getting stuck under a bridge. Slightly less embarrassing that way round.

[apex1]

Apart from being too deep and too tall. Hopefully you'll run aground before getting stuck under a bridge. Slightly less embarrassing that way round.

These boats are neither nor, you should keep your mouth shut when you do´nt know what you´re talking about! And obviously you do´nt k now European canal sizes!

[Crag Cay.]

And obviously you do´nt k now European canal sizes!
Please then, enlighten us as the the draught and air draught you can carry through the Canal du Nivernais or Villaine, as these are amongst the smaller French canals.

[apex1]

Please then, enlighten us as the the draught and air draught you can carry through the Canal du Nivernais or Villaine, as these are amongst the smaller French canals.

Maybe you are just joking (or are you going to split hairs?)
My statement referred to the fact that the boat is capable of cruising the (Freycinet size) French canals as well as the (much wider) other European ones! It was´nt meant every damp meadow.
The Nivernais btw is 2,90m air, 1,2m water

[Chris Ostlind]

Richard...

Why do you do this; Throw-out broad statements of fact and then later get incensed to the point of tossing insults when someone suggests that you define the issues more distinctly?

Crag merely suggested that from his experience, you had missed the mark with your post. You come back with the "you should keep your mouth shut when you don't know what you're talking about!" routine.

Disagreements are fine as long as you keep them civil. This comment you posted should not be a part of your expressed lexicon if you want to remain well-regarded. It sounds very much like a bully who wishes to shout-down the opposition.

[apex1]

Richard...

[QUOTE]Why do you do this; Throw-out broad statements of fact

There was no " broad" statement. The boats I pointed towards are capable open water cruisers and able to cruise the European canal system and >> even the narrower French canals<<

And "access to European canal system" was what the questioner wanted.

you had missed the mark with your post.

Do´nt see that sorry.

Disagreements are fine as long as you keep them civil.

Ok that was´nt polite I agree. But what is that worth to make childish statements about too tall and too much draught? When the vessel in question is capable of cruising more than 30.000km of European waterways but not 170km of ONE French canal, thats worth to mention? Sorry I call that idiotic.
I am not polite, I´m frank.

Regards
Richard

[FAST FRED]

"So could a 40 foot power boat with a 7 foot beam be built in such a way as to be stable at sea? I'm not sure if that hull form (with a sharp, plumb bow) would even qualify as something you could use as the center of a tri as it might be too beamy?"

WE are still looking to build a similar boat 39ft LOA 7.6 BOA with an Atkin Box keel and reverse deadrise.Shippable in a container and easily trailerable.

One huge advantage is the boat would be beachable , or can run aground with no damage. We like it for the ability to stand in a shipping container and the claimed efficiency at SL below3.

18K would be a fine cruise speed , and with a simple interior should go in under the EU 8,800 lb weight .

With much help from Rick W we believe great COASTAL CRUISING COULD BE DONE , yet the boat would be safe to make an offshore passage.

There are threads BOX BOAT , and others that discuss this perhaps modest (Below SL3) speed efficient concept.

WE hope for 5nm/gal at cruise, with Ivecio mechanical injection 6 cyl diesel

FF

[marshmat]

5 nm/gal at 18 knots would be quite an impressive achievement in a four-tonne boat, Fred. The concept certainly sounds like it's worth exploring.

As to CatBuilder's requirements. Given the European canal-cruising use profile, long and slim would seem to be the order of the day. (I should note that in the Canadian canal systems I cruise, lockage is charged by length, but beam is not penalized so long as you can fit through the gates. Thus, a beamy multi has an advantage here that it does not have in many European systems.)

But then there's the issue of ocean crossing. A 40' x 7-8' power cruiser is not a large or heavy boat. Ocean crossing under power requires substantial fuel reserves; if a large portion of your displacement is gas tanks, it may be hard to fit enough room to live comfortably while underway.

A kite sail rig applies fairly simple (although often rather large) forces to the hull, at an attachment point much closer to the waterline than any masted rig. As a result, the heeling moments would likely be much lower than for a conventional rig. I think it should be feasible to design a powerboat that could have a kite rig added at a later date, without compromising any of its powerboat characteristics.

If you look at most of the big ocean-going power tris (Earthrace, any of the big Nigel Irens record-hunters), it becomes evident that most of them are really just skinny monohulls with little "training wheels" as outriggers to keep them upright. They end up being extremely long for their weight and usable volume. In smaller sizes, I think there's something to be said for proportionally larger outriggers, especially when you're trying to get a lot of usable deck space in a given length. But if container shipping and really narrow canals are in the picture, sticking with just a single self-righting hull might make more sense. It sounds like a 40', 5 tonne version of the 83', 40 tonne Dashew FPB is an appealing concept?

[apex1]

It sounds like a 40', 5 tonne version of the 83', 40 tonne Dashew FPB is an appealing concept?

Look at posts #2 #3 Matt, he is exactly at that point.


Here is another interesting concept of a power tri

http://www.trybrid.org/trimaran/about/the-long-thin-hull/

[CatBuilder]

You guys are great at keeping a man thinking! :)

I have been reading this forum like I have a wire going straight in to my brain. I have learned so much in only a week or so here. Thank you for all the insight.

I think I am after a Dashew style boat, but was thinking trimaran (or maybe some flopper stoppers) more for anchoring comfort than anything else.

There are a lot of outside (not boat related) factors here I am trying to consider as well:

*Low build cost
*Longevity (lasting many years both in terms of hull and machinery)
*Canals
*Portability
*Comfort

[apex1]

Just some thoughts.
You have to give up the idea of a too narrow hull and a too lightweight vessel, IMHO. 40´by 7´something is just not sensible, where would you live in? A deckhouse will be impossible and the hull will be so narrow, thats close to living in a telefon box (European style). The windhorse concept cannot be scaled down to a 40ft boat I think.
But the designs I already pointed to, are very, very economical vessels and able to fit your needs in my opinion. Though much heavier than the original idea you had.
Give this a look too:
http://www.kastenmarine.com/greatheart36.htm

No, I do´nt get a commission. They are just nice and well designed.

And maybe I have missed that, but, why portable?

Regards
Richard

[CatBuilder]

Richard, a very similar boat (although it is a sailboat) is this one:

https://www.yachtworld.com/core/listing/boatFullDetails.jsp?boat_id=1867201&ybw=&units=Feet&currency=USD&access=Public&listing_id=1852&url=

She shares the same features and dimensions, with the exception of needing a heavy power plant. The interior is liveable enough if it allows me to come back to see the world on a budget. I already live aboard a 34' boat right now, yet she's a catamaran, so it's plenty of room.

I think you're right at 40' x 7', we are no longer talking about a Windhorse because the L/B ratio is growing much fatter.

I am looking to portability (shipping containers) to help facilitate an economic way to travel the world. Crossing an ocean on your own bottom is prohibitively expensive unless you build a Wharram style catamaran with all the low tech gear you can find. Container was to help offset costs.




Just some thoughts.
You have to give up the idea of a too narrow hull and a too lightweight vessel, IMHO. 40´by 7´something is just not sensible, where would you live in? A deckhouse will be impossible and the hull will be so narrow, thats close to living in a telefon box (European style). The windhorse concept cannot be scaled down to a 40ft boat I think.
But the designs I already pointed to, are very, very economical vessels and able to fit your needs in my opinion. Though much heavier than the original idea you had.
Give this a look too:
http://www.kastenmarine.com/greatheart36.htm

No, I do´nt get a commission. They are just nice and well designed.

And maybe I have missed that, but, why portable?

Regards
Richard

[apex1]

>>>She shares the same features and dimensions, with the exception of needing a heavy power plant.<<<

and not to forget she has a heavy keel to keep her upright! A powerboat of that size would better not need that!?

[CatBuilder]

>>>She shares the same features and dimensions, with the exception of needing a heavy power plant.<<<

and not to forget she has a heavy keel to keep her upright! A powerboat of that size would better not need that!?

Of course. I didn't say that because I figured it was obvious. ;)

[RAKY0311]

What about this?
http://www.multihulldesigns.com/designs_stock/38tri.html

[FAST FRED]

"But then there's the issue of ocean crossing. A 40' x 7-8' power cruiser is not a large or heavy boat. Ocean crossing under power requires substantial fuel reserves;"


Ocean CRUISING would be fine for a boat of these dimensions,
a CROSSING would be done snug as a bug inside a 40ft steel container.

I would only hope the vessel she is being transported on has enough fuel.

Once a more modest coastal range is accepted 500mi? 750 mi? 1000,mi?

The weight and volume of the fuel are mostly a concern if the fuel is used as ballast , and the boat more dangerous in Light Ship condition .

Although these days with no discharge rules , a dual bladder tank might compensate .

Fuel out , waste water in.



FF

[CatBuilder]

What about this?
http://www.multihulldesigns.com/designs_stock/38tri.html

Exactly!

That's the type of boat I was picturing and I recently did take a look at Kurt's site. Looks like this has (mostly) been designed already.

[RAKY0311]

I'm just receive the study plans for the tri trawler last week,I just love the comcept of this boat, like the idea of "trailerable"(a folding system would be perfect) but I dont kow if is good for an ocacional tripp to the Bahamas,I'm in florida.

[apex1]

Exactly!

That's the type of boat I was picturing and I recently did take a look at Kurt's site. Looks like this has (mostly) been designed already.

It just has one serious disadvantage! (if not more) It will not fit in a 40´container! And just one centimeter too large for a standard container and you add a zero to your freight rate! Thats not much but we live in a metric world you know?

[FAST FRED]

"but I dont kow if is good for an ocacional tripp to the Bahamas,I'm in florida."

The usual cruiser gang going to the Bahamas waits and waits for a good weather window , so the vessels offshore ability requirement can be (and usually is ) very limited .

The fish killers are happier to attempt a 2 hour passage in most weather , but 100GPH fuel flow , $6500 Stidd seats to keep their spines intact , and mere size helps them greatly.

FF

[TollyWally]

LOL,
a 100 gph fuel burn makes for expensive fish !