Steel or Aluminum

[scoobert]

Originally Posted by nimblemotors

So really, you have it figured out and don't need any input from CF.
To answer your OP question, use steel, you can hire cheap welders for it,
rather than Al, which requires highly skilled welding.
Be sure to put up a Blog and tell everyone how you got it done, how much it costs, and how long it takes, etc. We want to know.

yes, i will.
i am a professional photographer, and will be taking thousands of photos and a time lapse.
i plan to do a e-book after its all done as well.
and yes, i will be using steel.

[44'cruisingcat]

Originally Posted by scoobert

http://www.elcomotoryachts.com/pdf/E...zing-Chart.pdf

That table says 100hp is equivalent to 42.5kW, which is about 57 hp, so not triple the power. Add in a bit of salesemanship, and you'll likely find one diesel horsepower is pretty much the same as an electric one.

[scoobert]

its not the first place i have read it.
many years ago i had a job that required me to drive 42 miles a day, i was going to make an electric car at that time, as they did not even have a mass produced car.
i soon learned that all i would need to replace a 250HP mill was an 80HP electric motor, and it would roast the tires from the car.
electric motors have boat loads(pun intended) of torque.

that is not the company i will be buying from.
i will be buying from an electric engine builder.
much cheaper. and liquid cooled.

i don't know anyone who goes full power either.
my boat has 200HP, besides getting onto plane, it rarely goes full throttle.
once on plane i can back it to 1/4 throttle.
now take a displacement design.
how many times do you go full throttle?
do you ever?

i believe the 2-3 times the power refers to diesel as 2 times, gasoline as 3 times.

[noelex 77]

Scoobert I do admire your optimism and enthusiasm, but just for quick reality check. Lets suppose you manage you build your cat on time and on budget even then you will cruising on a vessel that by my rough calculations is:

5x bigger (by volume) than the average cruising boat
10-20X the battery bank of the average cruising boat
7-8X times the sized diesel engines than the average cruising boat + 2 electric engines.

What is cruising budget going to be?
Can you afford 5x the budget of the average cruising boat?
Have you the time for at least 5x the maintenance and repairs?

[transmitterdan]

Originally Posted by scoobert

its a common knowledge that an electric engine is 2-3 times the power of a diesel or gasoline.

how many times do you run your engines at full throttle? as in wide open?
well, that is your maximum power. for an electric engine maximum power is at 0 rpm. so i can run huge slow props at full power.

I have not followed this thread much since it borders on nutsville. But could not resist commenting on this whopper.

Power and torque are completely different units of measure. Any motor not turning is producing exactly zero power by definition. A locked rotor of an electric motor can generate torque but not power. Mechanical power produces motion by definition.

If you find yourself in force 8/9 winds near a lee shore you will push the throttle all the way forward. And most likely will wish for more thrust no matter how much or little you have. But in your case I am not too worried that will ever be an issue.

You may also want to look at a few propeller power vs. RPM curves before you get too far into the design.

Dan

[scoobert]

Originally Posted by noelex 77

Scoobert I do admire your optimism and enthusiasm, but just for quick reality check. Lets suppose you manage you build your cat on time and on budget even then you will cruising on a vessel that by my rough calculations is:

5x bigger (by volume) than the average cruising boat
10-20X the battery bank of the average cruising boat
7-8X times the sized diesel engines than the average cruising boat + 2 electric engines.

What is cruising budget going to be?
Can you afford 5x the budget of the average cruising boat?
Have you the time for at least 5x the maintenance and repairs?

The engines will be small and smaller. And rarely used.
I keep hearing about maintenance, i budget for 40 hours a week.
I have no idea what maintenance will be required on a new boat kept in mostly fresh water? But i believe i will have some.
Time will be limitless. I would like to keep two people on anchor for less then 1000 a month.

[scoobert]

Originally Posted by transmitterdan

I have not followed this thread much since it borders on nutsville. But could not resist commenting on this whopper.

Power and torque are completely different units of measure. Any motor not turning is producing exactly zero power by definition. A locked rotor of an electric motor can generate torque but not power. Mechanical power produces motion by definition.

If you find yourself in force 8/9 winds near a lee shore you will push the throttle all the way forward. And most likely will wish for more thrust no matter how much or little you have. But in your case I am not too worried that will ever be an issue.

You may also want to look at a few propeller power vs. RPM curves before you get too far into the design.

Dan

Its ok belief is not required, nor is percipatation.
You are 100% correct. An electric motor has maxium torque at 0 rpm and that does not calculate to hp rating. I am not here to give an engeneering class.

When the steel cat does run into rocks or whatever, it will take a lot of force to penetrate 1/4" steel.

Sent from my iPhone

[noelex 77]

Originally Posted by scoobert

The engines will be small and smaller. And rarely used.
.

Your engine A at 40HP is about the average size for a typical cruising yacht. Your engine B is extra and at 300 HP is considerably larger.

Originally Posted by scoobert

I keep hearing about maintenance, i budget for 40 hours a week.
I have no idea what maintenance will be required on a new boat kept in mostly fresh water? But i believe i will have some.
Time will be limitless.

Even if you are correct 40Hrs is a full time job for one person.

Originally Posted by scoobert

I would like to keep two people on anchor for less then 1000 a month.

This is not realistic for a 65 foot catamaran.
Have a look at the cost of haul out, time on the hard, and anti fouling paint as an indication of just some the sort of costs you will be starting to encounter.

I am trying not to be negative, but it better to confront he realities now rather than later.

[scoobert]

Sorry for being brief, i am away on business.
The plan for the anti-filing pain and to keep myself from having hull outs, Is to simply beach the boat on sandbars during low tide and work on it then. One small Spot at a time I can apply The anti-fowling paint. I'm not sure if I will ever even have to haul the boat out. Perhaps every 10 years or so for new shaft seals.
But I can only speculate on maintenance and upkeep. It's completely unknown.

Keep in mind I'll be keeping it mostly in freshwater. The bottom paint you last a very long time in those conditions.

[Mr B]

This Multihull was painted with anti foul paint in one tide change, There were 3 people painting it,

One of the Multihull advantages, No haulouts for maintenance.
Even thru hulls can be repaired or replaced during tide changes,

[noelex 77]

Originally Posted by Mr B

This Multihull was painted with anti foul paint in one tide change, There were 3 people painting it,

One of the Multihull advantages, No haulouts for maintenance.
Even thru hulls can be repaired or replaced during tide changes,

Ahhh those 3m Queensland tides a real nuisance, but they can be helpful as well.
Not many places worldwide have these sort of tides, however.
Even fewer in freshwater

[Mr B]

Originally Posted by noelex 77

Ahhh those 3m Queensland tides a real nuisance, but they can be helpful as well.
Not many places worldwide have these sort of tides, however.
Even fewer in freshwater

Hahahahahaha, That was Muscat Cove in Fiji, Less than 2 metre tide, He would have just scraaaaaaaaped on there at high tide,

I wouldnt take my Gemini across there At full tide,
I missed my boat in the dark one night and ran aground on there with my dinghy, Hahahahahaha

They have a 10 metre tide in the Kimberlys, With a 3 metre tidal wave going in and out of the gorges, You have to be on the ball up there,

[44'cruisingcat]

Originally Posted by scoobert

Its ok belief is not required, nor is percipatation.
You are 100% correct. An electric motor has maxium torque at 0 rpm and that does not calculate to hp rating. I am not here to give an engeneering class.

When the steel cat does run into rocks or whatever, it will take a lot of force to penetrate 1/4" steel.

Sent from my iPhone

When the steel cat runs onto rocks it's weight and momentum will generate a lot of force.

[hpeer]

Here's a great site about home building a 65' mono. Not as big a job as a 65' cat, but will give you an idea of what is involved.


Fascinating stuff, great videos

http://www.submarineboat.com/sailboat.htm

[scoobert]

Originally Posted by Mr B

Hahahahahaha, That was Muscat Cove in Fiji, Less than 2 metre tide, He would have just scraaaaaaaaped on there at high tide,

I wouldnt take my Gemini across there At full tide,
I missed my boat in the dark one night and ran aground on there with my dinghy, Hahahahahaha

They have a 10 metre tide in the Kimberlys, With a 3 metre tidal wave going in and out of the gorges, You have to be on the ball up there,

up here on the Hudson we may not have a huge tide, but it is fresh water, mind the sewage, and its enough time to make progress on the hull paint.