Do much Motorsailing ?

LONG_KEELER

LONG_KEELER

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Just wondering how much folks do, and any figures available with regard to VMG compared direct to target fuel savings etc.

Reckon I do about 25% of miles travelled . Largely estuary sailing.
 
When we were in the Solent, we were not using the engine too much, perhaps 5% of the time. However, we are now sailing in the Bristol channel, North Devon and S. Wales and we seem to use the engine much more, perhaps as much as 30% of the time. The big tidal ranges of the Bristol channel is the reason for using the engine a lot; getting to a harbour or somewhere before it dries out requires to keep the speed up by using the engine. In the Bristol channel you can go very fast with the tide and very slow or even backwards when it turns. Local knowledge of the back eddies helps a lot.
 
Although there was one memorable cruise when we sailed virtually without tacking from the East Coast to the CIs and back, since then and my retirement we have covered greater distances more often. This has meant that in order to retain enough energy to enjoy ourselves we have needed to limit journey times. I think that we sailed across the Channel more often than not but often ended up motoring or m/sailing in the North Sea, especially if there was a tidal gate at the other end. This was compounded by the need to choose settled weather as we got older, and night sailing when the wind would drop. In all, we probably had the engine on about 50% of the time.
 
We have a motorsailer, but we have made every effort to turn her into a sailing boat and, consequently, we try to sail her whenever we can. Since the sailing upgrades we tend to motor 75% less than we did previously, which is somewhat ironic as we also put in a new engine.

Since we increased our SA we begin to make satisfactory progress in the bottom end of a F2 and we will augment this with a cruising chute whenever feasible and in 8kts true we are already traveling at our normal cruising speed under power.

While we can go to weather, we like to avoid long windward trips, especially in rough conditions, other than if we can reach our destination on, or near enough so, a single tack. When we have to, we can make progress to weather and into the teeth of a F8 and heavy seas under power alone as we have on a few occasions.

Unless the boat is equipped with a feathering prop, motorsailing is a very inefficient means of propulsion, as fixed props are really only designed to function in quite a narrow range of load and RPM. PBO published an article on the subject and it rather illustrates my point. Other than to control the boats motion (somewhat) there was little gain in speed to be had. Much of this is also limited by an engine's ability to function beyond certain angles of heel. Consequently we do not bother much with motorsailing, other than to hoist the main or mizzen to keep things steady. As soon as there is enough wind to cause concern in that regard we are sailing anyway.

We sail in waters with much tidal activity, with locks and gates and also do a fair bit of river navigation. Still, we try to sail when we can, as we did on the Dutch canals. We don't bother short tacking up the Trieux, mind, just as much as that is not a recommended activity for the Prinzess Margriet Kanal either.
 
With a reasonably efficient sailing boat, almost never in the past two seasons and 5,000 miles.
In very light winds will furl jib and motor - can’t motor sail with jib filling as if wind less than 6 knots the apparent wind is dead ahead so the jib battens would bash on the mast.
Any strong per winds then sail.
Motor sailing is more of a concept for heavier and under canvassed boats, IMHO
 
dunedin said:
With a reasonably efficient sailing boat, almost never in the past two seasons and 5,000 miles.
In very light winds will furl jib and motor - can’t motor sail with jib filling as if wind less than 6 knots the apparent wind is dead ahead so the jib battens would bash on the mast.
Any strong per winds then sail.
Motor sailing is more of a concept for heavier and under canvassed boats, IMHO
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If you can keep up six knots with a following wind of less than ten knots, good luck to you. Although we don’t carry a spinnaker or cruising chute, we can make good progress in most conditions and are not ‘under canvassed’ for our purposes, and certainly not when compared with boats of the ‘70s and ‘80s. I would rather have a boat that copes well with stronger winds and capable of good speed in moderate winds than a boat that is a flyer in the marginal conditions between next to no wind and barely enough. Motor-sailing is sound seamanship also when a passage to windward would take too long or the desired course can’t quite be maintained.
 
If it’s light airs and not directly fore or aft then I can nearly always squeeze a little extra speed by motor sailing. When on a serious passage I reckon I am motor sailing about 30 percent of the time to get max speed. When not worried about the next tidal gate or getting into a drying harbour I spend less time motor sailing.
 
Yes more often than I probably should (too little, wrong direction etc) and it seems to work reaching, but I have a variprop and a motorsailor.
 
Laminar Flow said:
Unless the boat is equipped with a feathering prop, motorsailing is a very inefficient means of propulsion, as fixed props are really only designed to function in quite a narrow range of load and RPM. PBO published an article on the subject and it rather illustrates my point.
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Think you mean a variable pitch prop - a feathering prop (at least most except for the Gori "overdrive" ) are just fixed pitch props where the blades feather when not being powered. Bruntons is the only prop commonly available that is variable pitch (there are others, but not suitable for yachts) and is indeed popular for those who spend a lot of time motorsailing.
 
Tranona said:
Think you mean a variable pitch prop - a feathering prop (at least most except for the Gori "overdrive" ) are just fixed pitch props where the blades feather when not being powered. Bruntons is the only prop commonly available that is variable pitch (there are others, but not suitable for yachts) and is indeed popular for those who spend a lot of time motorsailing.
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Sorry, yes, I miss-wrote, you are of course correct. I meant to say variable pitch as in a Hundested, or the old Saabs, or as you mentioned, the Brunton, which of course is not quite the same as the former, but costs a couple of kidneys less.
 
dunedin said:
Motor sailing is more of a concept for heavier and under canvassed boats, IMHO
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I think(or rather I know) it is a misconception to assume that a heavier boat is slow or slower than a light displacement one in light wind conditions. In fact, if both boats had the same SA/D ratio and everything else were more or less equal, the heavier boat would outsail the lighter. Their average speeds would also be much the same with only occasional faster bursts for the lighter boat at higher speeds.
In this context the heavier boat, even if it had a little bit lower SA/D ratio than the lighter one may well be able to hold it's own in light going.
Much is made of the supposedly superior ability of lighter boats; light air performance isn't necessarily one of them.
 
Laminar Flow said:
he heavier boat, even if it had a little bit lower SA/D ratio than the lighter one may well be able to hold it's own in light going.
Much is made of the supposedly superior ability of lighter boats; light air performance isn't necessarily one of them.
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Heaviness can be taken to extremes of course but in the last few years I have often sailed past 38' boats of an often admired modern design with my '90s 34 in lightish winds. I got the impression that their wetted surface was working against them.
 
johnalison said:
Heaviness can be taken to extremes of course but in the last few years I have often sailed past 38' boats of an often admired modern design with my '90s 34 in lightish winds. I got the impression that their wetted surface was working against them.
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Exactly.
The reason is precisely the difference between frictional and form resistance. The amount of frictional resistance obviously depends on a hull's surface area, however it only fairly gradually and linearly increases with speed and it has nothing to do with displacement. In fact a deep, narrow hull can have a smaller wetted area than a beamy lighter one.
Form resistance, on the other hand, is directly related to displacement as this represents the real bulk that needs to be pushed through the water. The crux is that form or wavemaking resistance rises exponentially with speed.
Up to a relative speed of 0.7 form and frictional resistance share the same gentle rise, after which form resistance basically goes through the roof.

For a 10m DWL heavy displacement classical hull resistance at a relative speed of 0.7 (4kts) is an bout 40kg, at hull speed 1.34 relative speed (7.7kts) it is ten times that or 400kg.

Now, as most boats are designed to reach hull speed at the end of a F4 to beginning F5, boats with a similar SA/D ratio will reach hull speed at the same time. By making SA a factor of displacement and hence form resistance (the one that rises exponentially), the heavier boat has considerably more power (SA) to overcome the predominant and lower frictional resistance at lower speeds in lighter winds. Consequently, it will be faster.

The practical speed differences between lighter and heavier boats are marginal in as much as the accepted average relative speed for displacement sailing craft is about 0.9 and most boats rarely travel at hull speed.
The ability to increase SA is limited by a boat's stability; form resistance is exponential, stability isn't.

Lighter boats are capable, in particular because they tend to have a shallower run, to reach short bursts of speed above what is considered hull speed and are more likely to surf on waves. (We are still talking displacement hulls here).

The above also explains why our tub of 8.5t (see avatar) was able to pass a Pogo 30 (2.8t), both under genny only, in light winds. We were doing 4.5 kts at the time, relative speed of 0.85. Our genoa is 33 sqm compared to the Pogo's at 26 sqm, which would still give the Pogo a higher SA/D ratio. Yet it was enough of a margin for us to sail faster, in spite of a long keel, a three bladed prop, any potentially greater wetted area we may have and irrespective of the Pogo's longer waterline.
YM called the Pogo "A performer with cruising aspirations", conversely, that must make us a cruiser, not to say a motorsailer, with performance aspirations, right?
Physics can be down right awkward in light airs.
 
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LONG_KEELER said:
If it's good enough for Pete Goss it's good enough for me. :)

I have a rather long trek to the open sea. Sail when possible but otherwise I find motor sailing an excellent compromise.

Why motor sailing is good seamanship - Yachting Monthly
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Pete is of course welcome to do as he wishes.
Even though we own a motorsailer, we are not overly fond of motoring and tend to view it as a necessary nuisance and a safety option. In as much as a liferaft costs money and takes up valuable space, we try not to use our engine frivolously or unnecessarily either. It smells, is noisy and requires a good deal of money and effort to keep it happy. In and of itself it does not contribute to our enjoyment and which seems to increase considerably when we shut the thing off.
This has nothing to do with a purist attitude and I'm not about to faff around when our safety is at stake, but, in as much as a steadying sail on a fishing boat is not there to improve progress, motorsailing is just not an efficient means of propulsion, at least not in boats that do not have a variable pitch drive system.
To be sure, we do motor with (some) sail up, not to somehow increase speed, but to render ship movement more benign and to ween my crew off excessive drug use.
 
On one cruise from Bradwell to Camaret via the French coast ie Boulogne. Le Havre, Cherbourge-- Channel Islands etc. I actually managed 14 house of true sailing with no engine whatsoever. Much of it was engine only.
The following year I did the same cruise & quite by fluke I noted that I actually used the engine for 14 hours including entry to port etc. It just depends on conditions.
On my 2 round UK trips I used the engine for approx 20% of the time. This included going in & out of port ( which takes quite a lot of time) plus the Calledonian canal, which makes up a fair proportion. My average speed overall for both trips was 5.9 kts first time & 6.1kts second time. It would be noted that motoring speed was normally 5.9 kts at sea but much slower when entering port. ( I never anchor) Obviously I worked the tides, but 6 legs each time were over 100 miles, so tides cancelled out for those anyway.
I have just had a 2 week cruise in company with some friends round the east coast & sailed for 90 of the total 200 miles.
 
If anybody on here is keen on motorsailers, and is not (yet) a member of the Facebook Motorsailer group, please do apply to join - we currently have over 3,000 members, and everybody always plays very nicely and gets on well. (I am the deputy Moderator, and I never have anything to do, other than to approve new comers).
Facebook Groups
 
Bajansailor said:
If anybody on here is keen on motorsailers, and is not (yet) a member of the Facebook Motorsailer group, please do apply to join - we currently have over 3,000 members, and everybody always plays very nicely and gets on well. (I am the deputy Moderator, and I never have anything to do, other than to approve new comers).
Facebook Groups
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I agree that the FB motorsailer group is very informative and civil in it's interactions and I would recommend anyone interested in the subject matter to join.

Alas, for various reasons we are no longer on FB.

That is more than I can say about the site concerning our brand where, unfortunately, the narrative has been shaped by certain participants who have a history of ridiculing and dismissing the efforts or proposals of others to modify their boats to improve performance or meet their individual needs.
 
When i was in Bristol Channel we motored maybe 40% of time as arrival times were very critical. Now having moved to S Cornwall and got bigger genoa for our semi motor sailer we can keep it down to 25% or less once we escape from upper Tamar
 
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