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Old 30-03-2013, 01:18   #1
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Fuel Consumption of 40ft Cat, or Why Buy Sails?

From what I've read, a rough estimate of the fuel consumption to push a 40ft cat at hull speed is about .7-1.0 gallon per hour, at a speed of about 6-8 knots.
This is roughly 8 miles per gallon. This is much better than I'd expect!
It really isn't too bad at all. Looking at taking my boat to La Paz,
from San Franciso, this is about a 1200 mile trip. At 8mpg, this will take 150 gallons of fuel, at $4/gallon, cost of fuel is only $600.

So I'm trying to understand how I can justify buying one or two 40-60ft masts,
all the sails and rigging. If I will mostly make this trip and travel around the sea of cortez, and come back in a year or two or three. I'm really thinking I should just get a couple or three good motors, and forget the sails. Crazy?? Is my math off?

JackB
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Old 30-03-2013, 02:12   #2
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Re: Fuel Consumption of 40ft Cat, or Why Buy Sails?

You are not far off with your estimates and costings.

Sails are nice to have though if you are crossing an ocean. Tough doing 3000 nm on a power boat.
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Old 30-03-2013, 09:07   #3
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Re: Fuel Consumption of 40ft Cat, or Why Buy Sails?

You could be close in your estimates, but when you are heading back north, carrying that 150 gallons of fuel and bashing into the headwinds and seas, your mileage will drop dramatically. There are of course places to stop and refuel, and you should probably wait out the worst of the weather, but this is something to plan for.
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Old 30-03-2013, 10:58   #4
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Re: Fuel Consumption of 40ft Cat, or Why Buy Sails?

You are probably a bit low on your estimates. Better would be 1 gal/hr for one engine pushing the boat 6 kts. In any largish winds or seas, you will need both engines at ~1.5 gal/hr for 6 kts.

But don't you already have accurate burn rates from experience for your boat?

Mark
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Old 30-03-2013, 11:17   #5
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Re: Fuel Consumption of 40ft Cat, or Why Buy Sails?

My Lagoon 42 with two 3GM30's burned less than 1 gal per hour total at 8- 8.5 knots motoring. (maxprops)
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Old 30-03-2013, 12:01   #6
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Re: Fuel Consumption of 40ft Cat, or Why Buy Sails?

My boat is under (re)construction. It has no mast or engines at present.
Towing it with a powerboat, it seemed the hull speed was 6mph, to go any faster required a lot more power, and it only got it to 6.5mph.

I do have a bunch of sails that came with the boat, and a 34ft mast and rigging from another boat, a bit small for this boat. Given the winds of the california and baja area,
it seems I'll get either upwind or downwind. Upwind I'll be using engine power for sure,
downwind, I'm now thinking I can use a kite, something along these lines,
which doesn't need a mast. A mast and rigging is a lot of windage that makes the upwind motoring slow going.

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Old 01-04-2013, 21:31   #7
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Re: Fuel Consumption of 40ft Cat, or Why Buy Sails?

I've had a similar question, but never got a straight answer and did not have enough information to answer it myself.

What is the cost of ownership for a cruising sailboat vs a cruising powerboat?

Take into account equipment cost, wear, maintenance, etc.

Sails wear out, and they are expensive. It does beg the question whether sails are really much more economical than fuel.

There are other benefits to sailing though. The sound, smell, and heat of the engines would ruin it for me. I'd rather sit landside in a condo with a view.
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Old 01-04-2013, 21:48   #8
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Re: Fuel Consumption of 40ft Cat, or Why Buy Sails?

Quote:
Originally Posted by ArtM View Post
I've had a similar question, but never got a straight answer and did not have enough information to answer it myself.

What is the cost of ownership for a cruising sailboat vs a cruising powerboat?

Take into account equipment cost, wear, maintenance, etc.

Sails wear out, and they are expensive. It does beg the question whether sails are really much more economical than fuel.

There are other benefits to sailing though. The sound, smell, and heat of the engines would ruin it for me. I'd rather sit landside in a condo with a view.
Art, did you do a cost analysis of all those shoreside condos with a view at each location you want to visit? Or even a single one.

I will have both electric and liquid fuel propulsion (almost certainly gasoline, I HATE the smell of diesel), and the gas powered engines will be designed to be quiet and isolated from living quarters.

There is no question if you travel significant distances like crossing an ocean, sails are well worth the expense. That is not my plan. At what point the tradeoff occurs is of course highly depend on distance traveled and costs of components. A big diesel engine isn't cheap either.

I love sailing, and will have a smaller sailboat to enjoy local sailing about.

JackB
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Old 01-04-2013, 23:50   #9
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Re: Fuel Consumption of 40ft Cat, or Why Buy Sails?

Condos are money, but bought properly they will hold value better than a boat.

I'll be watching for your conclusions, and would appreciate any good references to information about electric propulsion systems.

Don't forget to account for the cost of engine and prop time! Also, I have heard that heavy motoring can be hard on keels that are not designed for it - but I think that was probably in reference to high speed motoring.
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Old 02-04-2013, 06:21   #10
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Re: Fuel Consumption of 40ft Cat, or Why Buy Sails?

Quote:
Originally Posted by ArtM View Post
...
Don't forget to account for the cost of engine and prop time! Also, I have heard that heavy motoring can be hard on keels that are not designed for it - but I think that was probably in reference to high speed motoring.
I don't understand the reference to keels and motoring and speed. Most catamarans I know of can sail significantly faster than they can motor. We can comfortably and efficiently motor at around 7 knots, while it is not uncommon to be sailing at 9 knots once there is a bit of wind.

Personally I'm a sailor, and like having sails, but for your use converting your sailing catamaran to a power catamaran may be a great choice. Lagoon and others have certainly done so with their power catamarans. You might like to compare some of the Lagoon power cats with their equivalent sail models to see some of the decisions they made when doing so - eg with respect to engine size etc.

Regards,
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Old 02-04-2013, 06:32   #11
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Re: Fuel Consumption of 40ft Cat, or Why Buy Sails?

Since running your engines more frequently, you'll need to factor in not only fuel, but more frequent changes: oil/lubricants, strainers, belts, impellers, coolant, other fluids. Wear and tear on parts and seals. Things like that. It may be a wash...

Also, there is absolutely no reason that the price of fuel will not rise, and likely will rise significantly.
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Old 02-04-2013, 06:39   #12
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Re: Fuel Consumption of 40ft Cat, or Why Buy Sails?

Quote:
Originally Posted by nimblemotors View Post
Art, did you do a cost analysis of all those shoreside condos with a view at each location you want to visit? Or even a single one.

I will have both electric and liquid fuel propulsion (almost certainly gasoline, I HATE the smell of diesel), and the gas powered engines will be designed to be quiet and isolated from living quarters.

There is no question if you travel significant distances like crossing an ocean, sails are well worth the expense. That is not my plan. At what point the tradeoff occurs is of course highly depend on distance traveled and costs of components. A big diesel engine isn't cheap either.

I love sailing, and will have a smaller sailboat to enjoy local sailing about.

JackB
The power cat part of your story makes since, but using gas engines will hose your quoted fuel mileage. Gas engine are higher rpm and burn more fuel. I have a dock mate next to me with a MainCat 30 that uses two 9hp Yamaha gas engines. He is dyeing to get rid of them and get diesels or electric.
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Old 02-04-2013, 07:05   #13
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Both cats we have had would sail 2-4knots faster on average than we could motor, sails really drive the boat.
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Old 02-04-2013, 07:30   #14
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Re: Fuel Consumption of 40ft Cat, or Why Buy Sails?

I find a lot of inspiration from the PlanetSolar Boat, circumnavigated from ONLY solar power. Of course, THAT many solar panels will cost more than sails!

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Old 02-04-2013, 07:33   #15
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Re: Fuel Consumption of 40ft Cat, or Why Buy Sails?

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Originally Posted by Cotemar View Post
The power cat part of your story makes since, but using gas engines will hose your quoted fuel mileage. Gas engine are higher rpm and burn more fuel. I have a dock mate next to me with a MainCat 30 that uses two 9hp Yamaha gas engines. He is dyeing to get rid of them and get diesels or electric.
He needs to get a tune up

I use a litre an hour per engine, and I only run the engines to get in and out of the marina. So even though we use the boat a lot, we still only have 350 hrs on the engines, partly because it sails well and it sails well partly because you can get the props and the associated drag out of the water.
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