Originally Posted by Pablo
I'm a bit confused. I read that a yacht that takes 18 hours to cross the channel following a set compass direction will be closer to its destination than a RIB that only takes 3 hours. Apparently the yacht does not get blown off course (wind or current) as much as a RIB.
Can somebody explain this phenomena to me please?
Completely depends on the wind direction and conditions. For a RIB and yacht going in the same direction and same speed with wind beam on a RIB would probably be blown more sideways simply because the yacht has a keel to prevent this. Wind just off the nose (45 degrees) the RIB will prob be less affected because of the windage of the yacht. This is assuming the yacht is motoring. If yacht is sailing and RIB is doing 25 knts, the effect of the wind on the RIB will be proportionally less because of the speed - I do not imagine a RIB "in the groove" will have much sideward motion due to wind. With a yacht beating, the CTS is much harder to calculate unless they are beating directly on course (and therfore a RIB has much higher chance of hitting a tgt)
Tide is compeltely different and again it's down to speed. Cross tide, the faster the boat, the less effect. Tide in front of you and you have a massive advantage in a RIB.. Tide just off the bow on a yacht and it'll get shifted a fair bit (I've been racing in the clyde with spinnaker up going backwards)
So - true CTS I would say a RIB has a much higher chance of hitting the target, mainly based on the speed it goes at.
As mentioned before, it all comes down to good navigation - knowing the effects of the tide and likely drift for your boat. GPS is of course very good at confirming an estimate on tidal effect and it's nice to see when they are spot on. A couple of years back I passage planned a 60 mile course in a yacht on the west cost to get us to a very tidal set of narrows at slack water - I was 10 mins out which is realy satisfying when you've done all the sums with tidal flow etc :-)