True Average Speed

[Bobc]

You're always better off under-estimating rather than over-estimating your average speed when planning.

If you have a tidal gate to make, you can always slow down, but you can't speed up.

And you get the benefit of getting there sonner than you thought, rather than if becoming a slog.

 

[ex-Gladys]

Surely this is an empirical number -i.e. you "guess" (or ask the PO) when you buy the boat, and then, in the light of experience, you adjust that number up or down, and maybe even have a range of different STW's for a range of conditions

 

[LittleSister]

A typical passage plan
Set of after lunch
Hope to arrive somewhere in time for last orders.

Yes, that's the sort of detailed analysis I usually do.

 

[Sybarite]

Planing, I'd say 10 knots,







Sorry.!

Are you planning on planing?

 

[john_morris_uk]

Or a little less on ocean crossings, interesting how close 100Nm days average out to reality over long crossings with a some good days then maybe a day or 2 becalmed. Not just me either, have a few beers in the major cruising crossroads bars and you'll hear similar averages, but not from those with monster fuel tanks and in a mad rush

When the first Transglobe Round the World (RTW) race between the services was planned using Nicholson 55's (no slouches in the right conditions) it was all done using 5 knots passage planning speed. It turned out to be very close to perfect for the whole RTW trip.

 

[Sybarite]

When the first Transglobe Round the World (RTW) race between the services was planned using Nicholson 55's (no slouches in the right conditions) it was all done using 5 knots passage planning speed. It turned out to be very close to perfect for the whole RTW trip.

I use 5 knts in my passage planning. If speed drops significantly on goes the Volvo.

 

[john_morris_uk]

I use 5 knts in my passage planning. If speed drops significantly on goes the Volvo.

The plan is just a guide. If the speed drops I consider all the options. One of them is changing the plan. :encouragement:

 

[Uricanejack]

I use 5 knots as a rough guide with my current boat which is a 35ft boat.
I used 5 knots on my old boat which was 24ft.
My next boat will have to be a whole heck of a lot longer for me to up my guestimate speed.
Its a rough guide. 20 miles 2 go. It will take me about 4 hours. I might get lucky and get there sooner. Or the odds are it might take longer. But if I want to get there at particular time I best give myself 4 hours.
Murphys law, tells me this is likely to be a bit optimistic.
So If getting there by a particular time is actually important for some reason. I best allow a bit of leeway.
How much leeway? Depends on how important.
I might give myself 20 or 25 % JIK Murphy is giving me a hard time. So 5 hours.
90% of my passage planning would be remarkably unimpressive. To a casual observer.
Just my opinion.
There is nothing worse for enjoyment and poor decision making than watching a clock tick away a little bit to quickly.

 

[Uricanejack]

The plan is just a guide. If the speed drops I consider all the options. One of them is changing the plan. :encouragement:

Absolutely :encouragement:

 

[Sybarite]

The plan is just a guide. If the speed drops I consider all the options. One of them is changing the plan. :encouragement:

Depends. Often I'm heading off to reach a certain destination. I sail while I can but unless I'm just out for the pleasure of being on the water - which often happens - I don't enjoy the prospect of arriving somewhere in the middle of the night just to be a purist.

 

[Babylon]

The plan is just a guide. If the speed drops I consider all the options. One of them is changing the plan. :encouragement:

Of course the OP's boat has no engine, so his options are narrower than the vast majority of us.

Not only can he not motorsail to maintain a minimum passage speed, he's also limited as to places he can manoeuvre into under sail to moor or berth.

Does he have a sculling-oar?