Most efficent propulsion?

j mantzel on youtube has been playing with solar and paddle wheels, old converted outboards and dd electric motors. he is worth a look. the latest is a solar sail paddle wheeler.
wouldn't the most efficient propulsion need to produce the energy/thrust required to get the hull upto the speed of one wave length? wouldn't a catamaran or trimaran that slices through water be more efficient than a monohull
 
For the same length no. More or less for displacement hull the rule is the longer, the lighter prevail.
Check human powered races legislation (like rowing), what they use as restrictions are the parameters that influence the 300-500W power-field :)
Solar boar are often cats because you can increase the size of pannel area keeping the thing stable :)
 
dept of def im curious on your thought, 4 boats with a 10 hp kicker all 4 boats are the average of their class all boats are 40 ft long. an off the line race between a trimaran , catamaran, monohull keeled sail boat and trawler whos fastest off the line and after 24hrs whos the leader. I have no clue
 
Hillhater said:
dodjob said:
For the same length no. More or less for displacement hull the rule is the longer, the lighter prevail. ...
Click to expand...
Assuming a common displacement , for any given length, a multihull will be faster (or need less power) than a mono.
Click to expand...

trimaran or catamaran?
 
Assuming you just want to power it, then either trimaran or catamaran, with keelboat third and trawler last.

But if you don't want to sail it, no point to a heavy keelboat, and if you're not going shrimping, same for a trawler, so just driving around, no solar panels, some variant of something like these has proven hard to beat.
 
Hillhater said:
https://www.boatingmag.com/catamaran-versus-deep-v-monohull/
Not a perfect comparason, however check the fuel consumption at 20kt.
Cat is half the Monohull !
Click to expand...

These are planing hulls, it's a different story :) again, in displacement, only length and weight ratio prevail (with some minor tweaks with hull geometry) :)
 
Hillhater said:
dodjob said:
For the same length no. More or less for displacement hull the rule is the longer, the lighter prevail. ...
Click to expand...
Assuming a common displacement , for any given length, a multihull will be faster (or need less power) than a mono.
Click to expand...

Cats can halve the weight/hull indeed, but again, pretty sure I've seen lots of comparison on displacement hulls giving close to no difference seeing that weight/length ratio is maintened . That said, as soon as it's brainfucking area, I would be glad to be shown wrong 😅☝️
 
Here's some boat nerding out... There's the prismatic ratio, which is pretty much the length over the width, and you keep getting significant drag reduction as you get towards 20/1, i.e. a 40 ft boat with a 2 ft beam, which is hard to achieve stability wise unless you go multihull, or hydrofoil stabilized. Over 20/1ish sees reducing gains.
 
I have a chance to pickup a 40ft epoxy over ply trimaran and the person has an older 10hp gas ob that's being converted to electric, it still needs something probably a controller. im really tempted. ive been playing around with ebikes and batteries. any thoughts on what amps and volts to use, 48v 40 amp?
 
goatman said:
I have a chance to pickup a 40ft epoxy over ply trimaran and the person has an older 10hp gas ob that's being converted to electric, it still needs something probably a controller. im really tempted. ive been playing around with ebikes and batteries. any thoughts on what amps and volts to use, 48v 40 amp?
Click to expand...

I had many a wonderful electric cruise on my 31 Piver glass over wood tri. The awesomeness of silently cruising around the harbor picking up friends, then heading out for a moonlight cruise, wind or not, can't be overstated. But depending on the condition, be ready to get good at dry rot and glass delam repairs... Smith's 2 part penetrating epoxy will become your best friend 😉
 
Hillhater said:
My comment was,....Same displacement,(weight), same length, ...multihul will be faster for the same power.
displacement hull, or planing hull.
but if you are not convinced, do a little reserch to satisfy yourself.
Click to expand...

Mate! I get satisfaction in being less stupid than a day before 😅🙈. I did this the last month by showing myself how wrong all my "common sense" was as soon as it had something to do with hull efficiency 😅
So please don't take my mentions as granted 🙈.
From what I've read (and searched) you have some different conditions in planning and displacement hulls.
I'm building a small electric inflatable dinghy right now. And because I need to circonvolute "foucking" french legislation, it had to be less than 2,5m (8') and less than 3,6kW.
I searched all I can to get something as efficient as possible without being stucked at hull speed (which is really not much for 2,5m 😅) but if you have some good source explaining how I can get better than a flat rig to plan earlier and use the brushless torque. I will hear this very very attentively 😬.
Have a merry Christmas! And I hope you didn't take my last posts as granted 🙈, really 😬
Gruß from Germany!
Hadrien
 
A flat bottom inflateable is probably the worst possible design for efficiency at low speeds
If you can use some rigid hull components a simple catamaran arrangement that keeps that flat bottom out of the water below any planing speeds, will hugely increase the speed you can achieve.
Think like a Hobi cat design ...but i dont know what limitations you have with an inflatable .
Seasons greetings :bigthumb:
 
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