Sail Drives..Like em?

[44'cruisingcat]

Originally Posted by tamicatana

SMJ,

What I have been curious to know in regards OB is, if you wanted to do trips beyond something like a coastal cruise, wouldn't the amount of fuel you'd have to carry be fairly substantial, as compared to diesel, even with a 4-stroke OB?

The other concerns I'd have: comparative flammability of gasoline; OB reliability (yes, one can easily just swap out an OB but I'm not into conspicuous consumption).

Our 20 hp Hondas use around 2l/hour. We can run at around 5.5 knots on one motor at 2 l/hour. Probably a bit more than a similar diesel setup, but then we'll be sailing when the diesel powered boat is motoring. Most people use 4 strokes. (Honda don't make 2 strokes)

Petrol is definitely more flammable. That's why you use an outboard motor, not a petrol inboard. Fuel tanks are in self draining lockers above the waterline. As are all fuel lines and filters. Any leaks go directly overboard, so you don't end up with bilges full of fuel and fumes.

Fact is, the vast majority of cruisers will be carrying some petrol anyway. For their dinghy. And propane too. I worry about the propane far more than the petrol, as the system is inside the boat, and leaks CAN accumulate onboard. Have sniffers and cutoffs to hopefully minimise the risks.

[DotDun]

Originally Posted by 44'cruisingcat

No stuffing around with funny antifouls that supposedly don't corrode aluminium. And don't work. No barnacle encrusted props. Ever. How good do you motor in heavy weather with an inch of barnacles on your props?

More bogeyman!

11 years, 2400 hours, no corrosion. Oh yeah, the props get cleaned along with the bottom.

[44'cruisingcat]

And of course everyone slips their boat as often as they should...

Not bogeyman, just facts. You DO have to use non-copper antifouls around saildrives. These antifouls do NOT work as well as the copper-based ones. You ARE far more likely to get growth on saildrive or shaftdrive propellers than you are to get any on outboard motor props, which are out of the water 99% of the time, and are only in the water when you're actually using them. Facts.

[Jimbo485]

In 2012 we fuelled up in Panama and then re-fuelled again in Australia. No diesels, no generator - just twin OBs, 970W of solar panels and 250 litres of petrol.

The trick for the OBs is to not put them on the stern where the vertical movements are exaggerated.

The topic of sail drive vs shaft drive is like listening to a couple of Amish farmers compare a mule to a donkey.

http://youtu.be/bc0REld-MAs

[thomm225]

Originally Posted by DotDun

Wow, is your outboard as loud as it appears in the video?

No, that's just the camera. Check this, you'd think these 20 knot winds were gale force going by the sound:

003 - YouTube

[DotDun]

Originally Posted by 44'cruisingcat

And of course everyone slips their boat as often as they should...

Not bogeyman, just facts. You DO have to use non-copper antifouls around saildrives. These antifouls do NOT work as well as the copper-based ones. You ARE far more likely to get growth on saildrive or shaftdrive propellers than you are to get any on outboard motor props, which are out of the water 99% of the time, and are only in the water when you're actually using them. Facts.

While bottom cleaning, I notice no more growth on the saildrives than the rest of the hull.

So your argument is perfectly maintained outboards vs. poorly maintained saildrives? :roll eyes:

[Jimbo485]

Hmmm.

OBs are great for maintenance, no drag, easy replacement, easy prop disentanglement, no antifoul, no smelly engines inside the hulls and no concerns about through hulls, seals, stuffing boxes etc.

The downsides are they cop a bit more salt spray due to their exposed location.

OBs were on our list of "would really like to have" when looking at boats.

[DotDun]

Originally Posted by Jimbo485

Hmmm.

OBs are great for maintenance, no drag, easy replacement, easy prop disentanglement, no antifoul, no smelly engines inside the hulls and no concerns about through hulls, seals, stuffing boxes etc.

The downsides are they cop a bit more salt spray due to their exposed location.

OBs were on our list of "would really like to have" when looking at boats.

Lots of choices when buying a boat, you make your choices and live with 'em.

More downsides in comparison (yes, there is a solution for each one):

- Noise (earplugs?)
- Storage of more volatile fuel (tanks must be in well vented storage locker)
- Longevity (95+% of outboards in junkyards have <1000 hours on them)
- Electricity production (noisy Honda generator?)

[Jimbo485]

Originally Posted by DotDun

Lots of choices when buying a boat, you make your choices and live with 'em.
So true!



More downsides in comparison (yes, there is a solution for each one):



- Noise (earplugs?)
Not a problem with the OBs in a closed locker (beneath cockpit seats). Never should be in the open and never should be on the stern.


- Storage of more volatile fuel (tanks must be in well vented storage locker)
Yes, this is easy on a cat with the fuel stored in stern cockpit lockers (or somewhere on the bridge deck) which drain by gravity into the tunnel not the bilge beneath the living spaces.


- Longevity (95+% of outboards in junkyards have <1000 hours on them)
THIS is the negative. Now do some maths and see if it is really that bad.


- Electricity production (noisy Honda generator?)
Who needs petroleum based electricity production on a cat??? We have lived aboard continually since 2010 without generators or alternators. Solar is cheap and cats have plenty of real estate for panels.

But then again, YMMV!

[Cotemar]

I can motor at 7.5 knots using one 30hp diesel engine using 1/2 gallon per hour at 2400 rpm.
We always motor with one engine only. Two engines would give me 10 knots, but it’s not worth the fuel burn

With sail drives the propeller is deeper in the water and the thrust is in line with the water flow giving you better efficiency and no prop walk.

My batteries will be fully charger as the engine has a 115 amp alternator.

I will have enough hot water for two days at anchor after running the engine for 30 minutes.

My diesel engines are not under the beds. They are in dedicated engine rooms that have plenty of room all around the for maintenance

My sail drives and props are always clean and I have never had a barnacle on them in the five years of owning the boat. Never had any corrosion issues.

We have folding props with 17" Dia. X 12" Pitch which give minimum drag while sailing.

[rjtrane]

As a designer/builder of both sail and power yachts, I'd like to add my 2 cents worth:

1. All my sail boats had outboards - most in wells just forward of the rudder. Intended to be used for maneuvering or when the wind dropped.
2. My power boats have used virtually all the varieties of delivering power to the water - straight shaft - stern drives - IPS steerable pods - sail drives.
3. The choice of drive depended on design choices both to the allocation of spaces and performance.
4. Of all the power trains, slant shafts tend to be the least efficient and least costly to install.
5. The counter-rotating dual prop, IPS and dual prop stern drive, are the most efficient delivering both more speed and less fuel consumption.
6. A well placed outboard or sail drive fall in between - more efficient than slant shafts and less than dual prop drives.

In choosing the appropriate power train for a new design, after engineering and design decisions, marketing plays a part. Based on this thread, we can easily see the number of prejudices out there that inform a buyer's choice. Seldom will a builder offer different drive trains in the same model - other than small shops building one at a time for custom buyers.

The reason, IMO, for comparing sail drives to stern drives is that their legs are made of the same stuff and both are Z drives with, typically, 90 degree gear boxes at the top. Both share similar maintenance issues with corrosion, seals and gear boxes. The stern drive adds to the complexity with steering and tilting. Most steerable pods are built of hardier alloys (other than the 2500 ZF) and of course, have their own maintenance issues.

In the electric-drive arena we are seeing some developments in both steerable pods and steerable sail drives - not much interest to a sailor, but with great potential for e-boats (my current line if interest).

BTW, my last personal cruising sailboat was a Phil Bolger sharpie cat yawl with a sculling oar to get me home went the wind dropped. With wind, I sailed.

[Jimbo485]

We motor at 4 knots with an 8 HP OB. 6 knots with both. We sail between zero and 20 knots. This is a 40' cat which displaces 6 t, fully loaded for long distance cruising.

The OBs have the props directly in line with the longitudinal axis of the boat.

I can lift out the engine with a huge burst of strength or use the preventer and boom to hoist it and then lower it to the cockpit floor for super easy maintenance.

When I chat with the Amish farmers, I can appreciate the various advantages they enjoy with their farm animals. However, we generally (but not always) prefer to use alternatives which have better advantages.

We move with the times and use the most convenient technology, just like Captain Cook. 15 years ago we would have had inboard diesels with shafts. Since then, OBs have come a long way.

But we still carry a sextant.....!

[a64pilot]

Way back in the day, outboards came into fashion because they were inexpensive, easy to maintain and didn't take up any room in the boat and replacing one wasn't a big deal.

What's changed?

[tamicatana]

Originally Posted by 44'cruisingcat

You DO have to use non-copper antifouls around saildrives.

well… not exactly.ish. the way to do it is to apply barrier coat on the SD and then you can apply whatever bottom paint you like.

I am not finding that I can't sail in light airs. I have Gori folding props, and since I just got my new laundry, the boat is going pretty dang well in light air. I would suggest that inability for cats to sail in light airs is largely a function of sailplan and weight. How clean is the bottom overall? There are other factors than propulsion drag.

I'm not convinced that my SD and diesels are much, if any, heavier than a couple of OB, especially when one considers the installation of some sort of lowering rig/frame and fairing for the OB which would need to be substantial.

I admit being a diesel geek. Husband turned me on to diesel cars and now I'm absolutely convinced that diesel is the way to go for any combustion engine. I just love the simplicity, efficiency and durability (and the ability to run 'em on 'alternative' fuels, 'cause you know the world's end is coming nigh.)

On the subject of corrosion, I have seen less corrosion in my SD than I did on my Honda 5 on my F-27GS and that boat was trailered, and we're Nazis about flushing and care. Honestly I was surprised how fast the paint bubbled on that little OB, I guess they don't make 'em like they used to

oh… and when bringing my boat home, we crossed the GOM from Sarasota to Pensacola. During the crossing, a front passed and the wind went dead ahead. (wind and barges, they all come to Tami.) We needed to get there, so rather than tacking, we engined it directly into the 30kts/8ft short-period GOM waves. I'd be surprised if OB would have done aught but cavitate (BTW ventilation is what happens to rudders/foils when air is pulled down from the surface along their leading edges; cavitation is pressure drop at propeller edges, bubbling air right out of the water)

[Jimbo485]

Originally Posted by a64pilot

Way back in the day, outboards came into fashion because they were inexpensive, easy to maintain and didn't take up any room in the boat and replacing one wasn't a big deal.

What's changed?

1. Power / weight.
2. Reliability.