Max Cruise 42

[ozolli]

Originally Posted by smj

Why do long distance cats need diesels and not outboards

I see one main reason; Charging the batteries may be hard with outboards.

[Tupaia]

Originally Posted by ozolli

I see one main reason; Charging the batteries may be hard with outboards.

Never used or relayed on my engines to charge. They are useful however to keep up the voltage when running the windlass.

[smj]

Originally Posted by ozolli

I see one main reason; Charging the batteries may be hard with outboards.

Shouldn’t be a problem on most cats as they have enough acreage to fit many watts of solar.

[ozolli]

Originally Posted by smj

Shouldn’t be a problem on most cats as they have enough acreage to fit many watts of solar.

It's not uncommon to have weeks without enough sun on some areas and seasons...

[smj]

Originally Posted by ozolli

It's not uncommon to have weeks without enough sun on some areas and seasons...

Other options? Wind generator? Small gas powered generator running an AC battery charger? Not having so much stuff that draws so much power?
Having owned a few different cats with both diesel powered and outboard engines I’ve never run across a problem keeping my batteries charged.

[Matt Johnson]

Originally Posted by smj

Why do long distance cats need diesels and not outboards, unless they are slow enough to be considered predominately motorsailors? Obviously she sailed from Vietnam to Florida?

It's too much boat for outboards.

It's not the ocean crossing that's the necessarily the issue, it's going into foreign harbors/ports without the local knowledge of what to expect. Florida and the Bahamas are well mapped and the cuts/current are well known, so it is pretty easy to work. Not so for a lot of the off the beaten path locations we've been.

I wanted to like outboard drives. I purposely looked for designs that offered them - the bridgedeck mold for this Max Cruise was ours first before we swapped last minute - but having been out in a smaller Dazcat 10m, Schionning 1100 and a Seawind 1160 with outboards, it became apparent that they wouldn't be enough for this boat in a lot of the conditions we've been in while cruising.

And what pushed me over the edge was hearing the collective response from owners, delivery crew and marine architects about wanting to go with outboards for our new build. Darren the designer for Dazcat, Tony Grainger of Grainger cats and Terry from Max Cruise (Julian from CM) all tried talking me out of going with them on a catamaran this size for a long distance cruising boat. Theirs was mostly concerns with safety - being able to motor long distances in emergencies and have enough power for close quarters maneuvering. But also reliability and noise/vibration/harshness.

*To be fair, both Bob Oram and Jeff Schionning pushed for outboards, and a few Seawind owners loved them.

My reasons for wanting outboards was weight and drag. Outboard's weight is phenomenal - no question here. But after observing the cats with nacelles/pods for their outboards while sailing heeled from a beam reach up, they all dragged their leeward nacelle through any waves, negating the drag benefit by having basically another hull in the water 50% of the time. The Schionning had wells in the hulls which was better, but that boat struggled with ventilation and moisture issues from always being wet.

This Max Cruise replaced its first set of outboards in South Africa after sailing across the Indian Ocean. I believe the second set were rebuilt in Florida on arrival. Large ocean cross swell swamped the outboards in their pods regularly. Not much you can do about that with fixed pods and needing the motors to articulate while having proper ventilation. Fine if you're able to wash them off after a day of sailing, but not great when it's weeks of salt water getting blasted all around the motor.

Besides the 13m Stealth Asia cats - which are extremely light weight and low windage (similar to a Shuttleworth and TRT), do you know of any production catamarans built over 38' with outboards? I think there is a reason for that.

Matt

[dougaljackson]

Originally Posted by Matt Johnson

It's too much boat for outboards.

Besides the 13m Stealth Asia cats - which are extremely light weight and low windage (similar to a Shuttleworth and TRT), do you know of any production catamarans built over 38' with outboards? I think there is a reason for that.

Matt

Makes sense.

We have a 13m Stealth with 30hp outboards. It works brilliantly on this boat for 2 reasons:

1. The outboards drop into 3D plugs like big sail drives, positioned well forward. They rarely cavitate compared to boats with them mounted on the nacelles or transoms.
   
2. The boat is extremely light (3.7 ton). We sail at least windspeed, sometimes a knot or two over in anything over 3 knots TWS, so we rarely motor. When we do, the low weight means we can cruise at 7 knots and do 14 knots at max revs. A heavier boat would struggle, or you’d need huge outboards.

Pros:

• No drag under sail. We see a difference of up to 2 knots boat speed with them lifted. They are bigger than sail drives and the props don’t feather though, so you’d expect more drag.
• Easier to source petrol than diesel in SE Asia. Can source from any servo using removable 25L tanks. This would be less of a concern in Aus, Europe or US.
• Very economical at 2,000 rpm.
• Lighter than diesels, means earlier sailing, means less motoring.
• Easy to lift to remove any ropes or nets tangled around props.
• Cheaper and easier to service, and replace if needed.
• No growth or corrosion.
• No risk of damage to fragile sail drives, or leaking around seals. Less of a concern with shaft drives.

Cons:

• Much smaller alternators. They do kick in a bit (16 amps vs 60+), and we have no problems running entirely on 1.3 kW solar in the tropics. But on a more complex boat at higher latitudes, it could be a problem. I guess you could solve this with a small petrol genset or hydro.
• Takes more time to deploy engines if the proverbial really hits the fan. This is less of a concern when the system becomes second nature. But we still act early, and leave them down at night if we’re worried about getting out of a sketchy anchorage quickly.
• Manouevering requires giving it more on the throttles. Takes a bit of getting used to if you’ve spent a lot of time on diesels or electrics.

Neutral:

• We haven’t noticed any difference in vibration or noise with 3-cylinder outboards compared to diesels. Apparently, the smaller 2-cylinder outboards were a different story.

TLDR; Needs to be a light boat, the right outboard system and fills a fairly specific niche. Not sure it makes as much sense for the majority of boats and use cases.

[smj]

Originally Posted by Matt Johnson

It's too much boat for outboards.

It's not the ocean crossing that's the necessarily the issue, it's going into foreign harbors/ports without the local knowledge of what to expect. Florida and the Bahamas are well mapped and the cuts/current are well known, so it is pretty easy to work. Not so for a lot of the off the beaten path locations we've been.

I wanted to like outboard drives. I purposely looked for designs that offered them - the bridgedeck mold for this Max Cruise was ours first before we swapped last minute - but having been out in a smaller Dazcat 10m, Schionning 1100 and a Seawind 1160 with outboards, it became apparent that they wouldn't be enough for this boat in a lot of the conditions we've been in while cruising.

And what pushed me over the edge was hearing the collective response from owners, delivery crew and marine architects about wanting to go with outboards for our new build. Darren the designer for Dazcat, Tony Grainger of Grainger cats and Terry from Max Cruise (Julian from CM) all tried talking me out of going with them on a catamaran this size for a long distance cruising boat. Theirs was mostly concerns with safety - being able to motor long distances in emergencies and have enough power for close quarters maneuvering. But also reliability and noise/vibration/harshness.

*To be fair, both Bob Oram and Jeff Schionning pushed for outboards, and a few Seawind owners loved them.

My reasons for wanting outboards was weight and drag. Outboard's weight is phenomenal - no question here. But after observing the cats with nacelles/pods for their outboards while sailing heeled from a beam reach up, they all dragged their leeward nacelle through any waves, negating the drag benefit by having basically another hull in the water 50% of the time. The Schionning had wells in the hulls which was better, but that boat struggled with ventilation and moisture issues from always being wet.

This Max Cruise replaced its first set of outboards in South Africa after sailing across the Indian Ocean. I believe the second set were rebuilt in Florida on arrival. Large ocean cross swell swamped the outboards in their pods regularly. Not much you can do about that with fixed pods and needing the motors to articulate while having proper ventilation. Fine if you're able to wash them off after a day of sailing, but not great when it's weeks of salt water getting blasted all around the motor.

Besides the 13m Stealth Asia cats - which are extremely light weight and low windage (similar to a Shuttleworth and TRT), do you know of any production catamarans built over 38' with outboards? I think there is a reason for that.

Matt

I think you’ve made the case, outboards work fine in a cat that is specifically well designed for outboards.
Our TRT would do 8kts with 2-9.9’s, 10kts with 2-15hp and 15kts with a single 50hp, so absolutely no problems with currents and probably better speeds than a standard 40’ cat with twin diesels. The TRT has pivoting pods that would put pod and outboard almost flush with the bottom of the bridgedeck, so 2.5’ out of the water, no problem with interference causing drag.
We’ve also owned a couple of Seawind 1000’s with outboards. 2-9.9’s would give about 7.5kts and no interference with those pods causing drag, not sure where you get this from.
Some benefits of outboards:
Weight
No drag under sail
No metal underwater to corrode when not motoring
No fouling on the prop, ever
If you pick up a line in your prop no diving over board to clear it
No through hulls or holes in hull to maintain. Cutlass bearing for straight shaft or the huge hole in the hull for the sail drive installation
Can pull motor to change lower unit oil, or pull lower unit in the dinghy, no haulout needed like a sail drive
Can pull motor and take it to a mechanic, no paying one for a house call.
Cost. For the price of a feathering prop which is a must on a diesel driven performance cat I can replace the entire motor
Negatives:
Uses more fuel
Uses gas instead of diesel but if well designed absolutely no issue
If badly designed they can have cavitation or ventilation issues
Reason why you don’t find many production cats with outboards? Because it goes against the mindset of most sailors and wouldn’t be a popular sale.

On edit: looks like I almost copy and paste Dougaljackson post
:-)

[Matt Johnson]

Originally Posted by dougaljackson

Makes sense.

We have a 13m Stealth with 30hp outboards. It works brilliantly on this boat for 2 reasons:

1. The outboards drop into 3D plugs like big sail drives, positioned well forward. They rarely cavitate compared to boats with them mounted on the nacelles or transoms.
   
2. The boat is extremely light (3.7 ton). We sail at least windspeed, sometimes a knot or two over in anything over 3 knots TWS, so we rarely motor. When we do, the low weight means we can cruise at 7 knots and do 14 knots at max revs. A heavier boat would struggle, or you’d need huge outboards.

Pros:

• No drag under sail. We see a difference of up to 2 knots boat speed with them lifted. They are bigger than sail drives and the props don’t feather though, so you’d expect more drag.
• Easier to source petrol than diesel in SE Asia. Can source from any servo using removable 25L tanks. This would be less of a concern in Aus, Europe or US.
• Very economical at 2,000 rpm.
• Lighter than diesels, means earlier sailing, means less motoring.
• Easy to lift to remove any ropes or nets tangled around props.
• Cheaper and easier to service, and replace if needed.
• No growth or corrosion.
• No risk of damage to fragile sail drives, or leaking around seals. Less of a concern with shaft drives.

Cons:

• Much smaller alternators. They do kick in a bit (16 amps vs 60+), and we have no problems running entirely on 1.3 kW solar in the tropics. But on a more complex boat at higher latitudes, it could be a problem. I guess you could solve this with a small petrol genset or hydro.
• Takes more time to deploy engines if the proverbial really hits the fan. This is less of a concern when the system becomes second nature. But we still act early, and leave them down at night if we’re worried about getting out of a sketchy anchorage quickly.
• Manouevering requires giving it more on the throttles. Takes a bit of getting used to if you’ve spent a lot of time on diesels or electrics.

Neutral:

• We haven’t noticed any difference in vibration or noise with 3-cylinder outboards compared to diesels. Apparently, the smaller 2-cylinder outboards were a different story.

TLDR; Needs to be a light boat, the right outboard system and fills a fairly specific niche. Not sure it makes as much sense for the majority of boats and use cases.

Sounds like a great solution for the outboard "plug". I thought the sleds on the other Stealth's was neat, but being so far aft, figured they'd lift clear of the water way to often to motor in anything but super calm seas.