Average speed to calculate a long trip

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pcatterall

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From Sardinia to Menorca is a long trip ( for us) being around 300 nm.
In order to plan nights at sea, arrival in daylight etc. I am assuming we can make around 4 knots in our 33 foot Neptunian ketch. With a 6am start and 3 nights at sea this would put our arrival off Menorca at around 8am so having the rest of the day to get into a suitable marina.
Below 4 knots sailing we can switch on the trusty 4108 and motor or motor sail (on motor alone we cruise at 5 to 6 knots).
Does 4 knots seem like a reasonable average?
 
In relatively calm seas that is probably an underestimate. Do you not have records of previous passage times to give you a guide? If you are prepared to use your motor then you should be able to achieve closer to 120 miles a day. - ie near 5 knots average.
 
Thanks. Yes we do keep a log ( though not with me here) however that records speed on the set course ( which may not be the direct line) and average speed for the day which includes slow passage into moorings and messing about. The figures are usually for day sails and some overnight rather than for 3 days of sailing.
Depending on wind direction and changes the distance will increase so at the moment I will work on 4knots.
 
Planning against an unrealistically slow speed can also lead to problems - when we delivered our new-to-us yacht from ipswich to the solent I planned too conservatively and we ended up at Selsey Bill far too early and we ended up going round the Owers due to the foul tide. I would have thought 5 kts would have been more realistic for a 33' yacht?
 
At least there are no tides or tidal gates to worry about. I wouldn't worry about maintaining a particular speed by using your engine, if you have to take an extra day, it's no great shakes, you've got all summer and there are plenty of beautiful anchorages around. Just make sure you don't let all your rode run out!!!!!!
 
Regarding underestimating. If on day one we are ahead of schedule then we can relax a bit on our speed perhaps easing off over the night watches, we should be able to ensure that by the end of day 2 we are about on target. The forecast winds when we leave may mean we are able to assume a slightly faster average and there is always heaving too for lunch !!
As said tides and currents are not an issue, one consideration for us is that we could push for a 2 night trip but that would mean arriving at our destination late in the day or go for 3 nights and arrive in the morning.
Thanks all
 
ghostlymoron said:
At least there are no tides or tidal gates to worry about. I wouldn't worry about maintaining a particular speed by using your engine, if you have to take an extra day, it's no great shakes, you've got all summer and there are plenty of beautiful anchorages around. Just make sure you don't let all your rode run out!!!!!!
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I thought we had a gentleman's agreement about running out of rode!! Wind direction is, of course, an issue, I seem to recall an ETA being 2 hours away and then 1 1/2 hours later still being 2 hours due to wind on nose?!
 
The way I do it is to calculate for two numbers, likely slow and likely fast, which for us is 5 to 6.5 kts, although of course in any hour we may do only 2.5 or as much as 8.5.

I use these two numbers in a few ways, eg:

1. to calculate time to set off so we arrive on the flood, or in daylight etc.
2. to have a set of 'rules' for the passage such as if the speed drops below 4kts then put engine on.

These two speeds are derived from a number of passages in our boat, eg it's always 70 hours Falmouth - Troon or Troon - Falmouth, about 390 miles, so 5.6 kts. We've just done 2100 miles, incl doldrums/ITCZ and it was 15 days, so 5.7. We did Falmouth - Azores, 1250 miles in 7.75 days, so 6.7, but this was a fast passage.

Thus using these numbers, were we to be doing it, it would be between 46 and 60 hours. I will assume you want to arrive in the daylight, and I will further assume that days are a little more than 12 hrs long. So set off as soon as light. If the passage is fast you'll only have to stand-off for an hour or two on the morning of arrival: no prob. If the passage is slow then you'll arrive with an hour or more of daylight left, still no prob. But these are for my boat not yours.

Assuming 4 - 5.5 kts as the two figures: 55 - 75hrs (2 days 7hrs to 3 days 3 hrs). This is a range of 20 hrs so rather more than one period of daylight. Hence I'd take the time to set off as evening minus about 76 hrs = around 2pm say. No prob. Now what if fast? This means that you'd arrive at 9pm at the earliest and probably in the middle of the night. So you might investigate an anchorage or somewhere just near your destination which you can enter with confidence in the dark.
 
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pcatterall said:
From Sardinia to Menorca is a long trip ( for us) being around 300 nm.
In order to plan nights at sea, arrival in daylight etc. I am assuming we can make around 4 knots in our 33 foot Neptunian ketch. With a 6am start and 3 nights at sea this would put our arrival off Menorca at around 8am so having the rest of the day to get into a suitable marina.
Below 4 knots sailing we can switch on the trusty 4108 and motor or motor sail (on motor alone we cruise at 5 to 6 knots).
Does 4 knots seem like a reasonable average?
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As others have said, it's not a precise science and the distance you sail will probably more than you expect as the wind in the Med is never where you want it.

4 knots average is as good as anything but I usually do the calculation to arrive at say 10:00am. Depending upon the time of year, but assuming it's light at 5:00 am, this gives you 5 hours leeway at the fast end (but it's not critical 'cos you can always hang about for an hour or two) and around double that leeway at the slow end (where it is more critical as you don't want to commit to an extra night bobbing around if you can avoid it) :)

Richard
 
We've done the crossing a number of times now in both directions, usually takes us about two and a half days or so. We usually set out at dusk on day one to arrive at dawn two days later. Going east, we usually go into Porto Conte and drop the hook to catch up on sleep. Then carry on to Algehro for a few nights, getting an Italian SIM card sorted and all of the sort of stuff.

The advantage of Porto Conte is that the entrance is vast and there's good holding in the central lagoon which is enormous and usually pretty empty. So it doesn't matter too much if you arrive in darkness: just head for the middle of the bay and drop the hook. Nothing there ashore apart from some holiday complexes, so make sure you've got provisions for your stay.
 
On our two long legs westward across the Med from NW sicily to Cagliari and from there to Majorca we averaged well over 5 knots motorsailing into the wind. pretty boring, so just put on the donk, set the autopilot and relax. You get there when you get there. Remember 4 knots takes 15 hours longer than 5 knots so unless enjoyable sailing is on offer press on as fast as is comfortable (assuming you have enough fuel - you will need well over 120l for 300 miles at 5 knots.
 
pcatterall said:
Does 4 knots seem like a reasonable average?
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As said, 4 knots seems unrealistically slow, assuming you pick a weather window with sailable winds. Of course it's unpredictable, but surely your log book should tell you your typical cruising speed? From there, pick a realistic high and low extreme the median of which which will bring you to your destination in the middle of the day. But if you're happy entering that particular harbour in darkness, leave when you like.
 
As others have said, it's not a precise business. However, on the trip from Greenock to Titchmarsh, I did my initial planning on the basis of 5 knots and found this an underestimate. 6 knots was a bit over, but was closer than 5 knots. We used engine whenever the speed dropped, though, as the emphasis was on covering miles, not sailing! Objectively, we did about 100 nm in 16 hours, and 156 nm in 27 hours; both work out close to 6 knots. That was at economical revs for a Moody 31; a longer boat should do better. Although we did attempt to work the tides, it tended to even out on the longer passages.
 
ghostlymoron said:
At least there are no tides or tidal gates to worry about. I wouldn't worry about maintaining a particular speed by using your engine, if you have to take an extra day, it's no great shakes, you've got all summer and there are plenty of beautiful anchorages around. Just make sure you don't let all your rode run out!!!!!!
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Not sure about the beautiful anchorages between Sardinia and Menorca? It's not like you've got a lot of bolt holes - quick look at Google Maps suggests it's Mahon or bust unless you want an unscheduled visit to Algeria although I may well have mi-understood or missed something. Otherwise I agree I totally - what's the hurry and why the need to be so precise when you have no tidal gates to time?

I'd turn the question around and ask what's the longest time you can afford to take and see if that gives you an acceptable speed. I'd guess for a passage like that I'd want to be sure I could comfortably spend 5 days at sea as a safety margin (rationing drinking water maybe or that sort of thing).

Even at 3 days a weather window should be fairly easy to pick and then you can adjust your passage speed so as to arrive in daylight - though I think that's very overrated after a passage personally. I'm just as comfortable and sometimes more comfortable at night unless there's a lobster pot issue or similar.
 
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