Passage Planning for a 20 foot sailing boat

[dom]

We are assuming (reading between the lines a bit!) a trip along the coast. Mostly that involves tides turning every 6 and a bit hours with a bit of local variation.
Obviously need to check the almanac, pilot and/or tide stream atlas to make it work.

Aha, got it!

 

[jac]

Sounds poor to me.

Depends on speed and tacking angle of course but assuming no tide VMG = speed x cos ( tacking angle)
so 5 knots @ 50 degrees ( including leeway) = 5*0.64279 ( to 5 decimal places!) which equals 3.21 knots
5.5 knots @ 55 degrees ( including leeway) = 5.5 * 0.57358 ( to 5 decimal places!) which equals 3.15 knots

Heeled over, excessive leeway occasional waves stopping the boat and something more like 2 knots becomes a very real prospect.

 

[EdWingfield]

Sounds poor to me.

I measured mine in still fresh water - Ijsselmeer. I was a little disappointed. But It is realistic for my boat.

I'd be interested to know yours, and others VMGs

 

[Judders]

What boat and what ports?

There are 20'ers and 20'ers, especially to windward.

 

[dom]

What boat and what ports?

There are 20'ers and 20'ers, especially to windward.

Nope, that's the beauty of this thread -- you've got to infer those two parameters (see lw395 above)

Quite cryptic really

 

[Topcat47]

Snark has a LWL of 20' (ish) on a 26' hull. She's capable of 6.5knots under the right conditions but I'd never passage plan on that. My best ever channel crossing was 10.5 hours, Cherbourg - Portsmouth; my worst 28 hours although I did end up going via the Needles that time. I generally reckon on 4knots average when passage planning. With the prevailing SW winds along the South Coast, I allow 16 hours to get to Cherbourg as a rule of thumb. working along the coast, tides have a much bigger effect on Snark's SOG. With the right wind and tide, I can do a return trip to Yarmouth in a day, or not make Cowes & back, if the conditions are really bad.

 

[Triassic]

I'd be interested to know yours, and others VMGs

Mine usually works out around 7 knots to windward. It can be higher in smooth water where I can pinch more but in any sea state I have to bear away to keep the power up and then it simply becomes a question of how uncomfortable you want to be..... I usually passage plan based on this figure, however with a favourable wind I can easily double that...!

 

[Lucky Duck]

Nope, that's the beauty of this thread -- you've got to infer those two parameters (see lw395 above)

Quite cryptic really

Coastal passages but I don't really know the area well and haven't yet researched to see if there any local conditions that mean the tide is anything but six hours each way (such as the greater Thames estuary or from Brighton to Dover) but the tidal strengths didn't seem particularly strong.

However I was after feedback as to whether my estimated speeds were realistic or not rather than looking advice for specific passages.

 

[Triassic]

This is one of those areas where nothing will really replace your experience with that particular vessel. You will very quickly get a feel for how she performs in certain conditions and perhaps more importantly, how you want to sail her. My advice would be to stay on the conservative side to start with, build in alternative plans should you need them, and go out and enjoy yourself.

 

[Fantasie 19]

I'm looking at two passages, one just over 40 miles and a longer journey which may need to be split up into similar distances - both more likely than not, given the prevailing winds, with the wind on the nose for the entire trip.

Its been a while since I had any experience of sailing this type of boat but I was working on a passage planning speed in the region of three or four knots (ignoring tide which if fair would be four or five knots I suppose)

Does this seem right or am I being overly cautious or optimistic?

Boat is typical 1970s design with masthead rig, fin keel and an outboard rather than a lightweight flyer.

On my 20 footer I passage plan to 3 Knts - if I get there quicker then all to the good...

 

[Judders]

However I was after feedback as to whether my estimated speeds were realistic or not rather than looking advice for specific passages.

If you're sailing an SB20 they're pessimistic, if it's a Vivacity 20 they're optimistic.

Not all 20'ers go at the same speed.

 

[Lucky Duck]

If you're sailing an SB20 they're pessimistic, if it's a Vivacity 20 they're optimistic.

Not all 20'ers go at the same speed.

Boat is typical 1970s design with masthead rig, fin keel and an outboard rather than a lightweight flyer.

So not a SB20 but I'd expect it to be better than the Vivacity

 

[LadyInBed]

If it were me, I would wait till the wind turned, unless you are a sucker for punishment!

 

[jakeroyd]

This thread illustrates very well the dilemma I often have , to motorsail or not.
I have a Hunter Ranger 245 and usually plan on 4kts.

However the difference is that whilst say 30 footers sailing with me are doing 4kts under sail I will be doing 4kts motorsailing.

Perhaps I don't have enough patience but when my sailing boatspeed gets under 3kts I reach for the iron sail.

This is in part down to the boat , being undercanvassed in light airs.

I need to use it's scooper or light weather cruising chute much more (note for the coming season)

If a long way to go upwind i will motorsail anyway.

 

[Lucky Duck]

I used to have its larger sister, as you say the self taking jib did make the boat under canvased if the wind was too far forward of the beam to use the "scooper"

Otherwise there was a lot to recommend it :encouragement: