Power Trimaran vs Power Catamaran efficiency

[baeckmo]

This thread is really remarkable. OP asks which boat cat or tri? ...okay mono.....

Post no 7 gives a basic comparison values for mono, cat and tri, for pedagogic purposes. It illustrates the principal trade-offs occurring when splitting a load in different steps. A sound comparison goes back to basics. What is it you find remarkable?

 

[fallguy]

Post no 7 gives a basic comparison values for mono, cat and tri, for pedagogic purposes. It illustrates the principal trade-offs occurring when splitting a load in different steps. A sound comparison goes back to basics. What is it you find remarkable?

Just that the OP really has no idea what they want and we ought to help and you have highlighted as much.

 

[rxcomposite]

The OP stated as in the title of the thread, Power Trimaran.

He is contemplating between a cat and a tri but somewhere digressed back to monohull.

Others:
Fully covered deck (NOT a naked beam) as in Neel trimar "deck extends to all 3 hulls" .
" this will be a solar/generator hybrid liveaboard trawler moving at displacement speeds"

He is looking for:
"simpler overall build"
Efficiency defined= "I'm referring to fuel efficiency. Im wondering if a boat with 3 light hulls requires less power to move at hull speed than 2 thick hulls"

But due to inexperience in design, he got confused.
"The trimaran can have less wetted area than a catamaran. The reason for this is that the outer hulls (amas) can be made to do little more than act as training wheels, to keep the narrow main hull from tipping over. Double outriggers work on this principle, as do most modern sailing trimarans."

"With "low buoyancy" amas, the amas are still usually a high fraction of the length of the main hull. But their enclosed volume is a lot less."
No, this configuration is for a sailing tri, not a powercat.

 

[latestarter]

As this will be a solar/generator hybrid liveaboard trawler moving at displacement speeds,

The multi-hulls will have greater deck area for panels so may more than offset an increase in hull resistance.

 

[BlueBell]

Im interested in building a power aluminum yacht, and I'm curious about the efficiency of 3 thin hulls (trimaran) vs 2 wider hulls (catamaran).

Saltfinch,
Are you planning to design this build as well or will you be going with a proven design?

 

[bajansailor]

Re power trimarans, you might get some good inspiration from the vessels designed by John Shuttleworth -
Shuttleworth Design - Projects https://shuttleworthdesign.com/designs.html

And Nigel Irens -
Power - Nigel Irens Design https://nigelirens.com/boat-category/power/

And the controversial Earthrace, designed by Craig Loomis -
https://www.lomocean.com/projects/earthrace

 

[BlueBell]

I am a huge fan of the stabilized monohull concept of Earthrace.
And it ticks-the-box of the OP's "lowest drag" priority.

EDIT: Correction, "efficiency" priority, not "lowest drag" priority.

 

[Alan Cattelliot]

Etoile Express by Patrick Balta, a bit longer, but still a very efficient boat, used for offshore sailing race tracking.

Balta Patrick, architecture navale, yacht design, catamaran http://www.balta.fr/etoile%20express%20photos%20en%20mer.html
Fuel consumption ridiculously small...

 

[rxcomposite]

With "low buoyancy" amas, the amas are still usually a high fraction of the length of the main hull. But their enclosed volume is a lot less. With a powered trimaran there is very little downside to this, as far as I can see. The low buoyancy amas will be both lighter and will impose far less loads on the connecting beams.

I was thrown off for a moment. I thought you were referring to Nigel Irens design. A LOW fraction of the sidehull (to the central hull). It is barely touching the water but has a large reserve buoyancy, Deck is fully covered though. Fuel consumption very low.

Throw in some numbers so we can come up with a decent answer. What is your estimated displacement? Nu. of PAX/crew?

If your requirement is a full superstructure all the way to the beam and you have a lot of people (live load) walking or congregating on the edge of the deck, you will need a wide beam and high displacement ratio of the sidehull, most probably the length will almost equal the length of the Central hull. Tri's have deck about 3/4 of a cat, but with this configuration, the design will be approaching that of the cat. The characteristic will be likely a cat. Higher fuel consumption, heavy and complicated crossbeams, plus all the unwanted seakeeping behavior of a cat like corkscrewing and pitching.

 

[BlueBell]

Ah, the allure of efficiency.

What's the point if it doesn't meet the need (SOR).

 

[rxcomposite]

Ah, the allure of efficiency.

What's the point if it doesn't meet the need (SOR).

Forget the SOR. I like it. My friends can drink from a barstool and take turns sleeping.

 

[saltifinch]

Sorry for not updating a reply, I stopped getting email notifications at some point.
The purpose of this post was to understand a bit more about how vessels move through water based on actual data and observation, rather than just some sales pitch. I can read a hundred sales magazines telling me how great a design is, but I'd rather understand why it actually works so that I can continue to modify my wants and needs.

I absolutely would work with a professional designer. I can build a vessel, as I am a certified welder, but naval architecture is to be respected.

I appreciate the feedback. It seems like the possible gains in a power trimaran are easily offset by all the design, build, and weight offsets of the Amas if the intended purpose is not clearly followed.

Stability and fuel efficiency are my primary interests, as I want to spend a long time onboard. I think a trimaran interested me due to its better theoretical handling in rough weather, but Im not sure this is really enough of a reason. If a catamaran has improved deck space and stability and is more fuel efficient for a given weight than a monohull yacht, than the answer is pretty clear to me. Trimarans are probably too much trouble.