Small Boat NAvigation
The High Speed Navigation Plan
Most small powerboats do not have chart tables and can often be wet and windy places. If we don't want our expensive charts to turn rapidly to papier mache, we need to do a bit of preparation. The following technique, plagiarised from several sources and very similar to that used by rally navigators and motorcyclists, is simple, works well and can be executed in a few minutes. Don't believe me? Ask any of my recent PB2 students who have all been pleasantly surprised how easy it was to become a 'high-speed' navigator!
Step One. Select the route. Clearly we start by checking Notices to Mariners, the Weather/Tides and other passage planning appraisal items - common to all voyages. We can then start planning. Pick a good start point just outside your start harbour, one that is easy to find and one that you can arrive at already at cruising speed. Aim to finish the high speed portion at an obvious feature close to the entrance of your destination harbour that gives you time to slow down and sort yourself out start your pilotage plan. I will discuss pilotage plans...i.e. how to get from dock to start point, and finish point to dock... on a separate page. Then pick a few good nav features along the route. We will plan a trip for a RIB cruising at 20kts, so features every couple of minutes are good. On the chart below is a short route from Cowes to Newtown via 3 buoys - in reality you probably don't need as many waypoints but this is just for illustrative purposes
Step Two. Draw a simple diagram of the route.... the boat will always be going forward from our perspective so a straight line will suffice (more later)
Step Three. Measure the Headings from each point to the next. Don't forget magnetic variation if there is any. we can then transfer the headings to our sketch plan
Step Three. As you can see above, I have already started working out how long it takes to get from each waypoint to the next. To do this we must first measure the distance using dividers, as below, and then work out how long it will take to do that distance. We are travelling at 20kts so, as explained on a previous 'top tip' we multiply the distance by three to get time. i.e. for our first leg below, 0.7 nm takes 2.1 minutes or, as watches usually read minutes and seconds, 2 minutes and 6 secs... 2:10 is close enough for our purposes. We need to do this for each navigation leg and update our sketch plan accordingly:
Step Four. Once we have all the headings and times on our plan we can add a few other helpful details to orient ourselves... no need to be too detailed. In this case we note that there is shallow water, and the IOW, to our left and, if we are on track, the final waypoint should be roughly in line with the far headland by Hamstead.
Step Five. Pop your plan in a water resistant cover, grab your stop watch and you are ready to go! We will discuss each end of your journey - the pilotage plan - in a later 'top tip'
Step Six. Have fun!!
