There is a way to mitigate the amount of fuel usage cruising on a river and when your cruise is a relatively long one, the savings do add up. This would be what I call (it may go by another name
) " current manipulation".
Principle: a river's current, on a straight section, is fastest in the middle/nearest the channel. This is because the water has no real obstacle to its flow. By the very nature of the flow the opposing bank's flow is slower** and cruising upriver there takes less effort (ie. Less fuel usage than cruising in midstream to travel the same distance).
** traveling this way does take some precautions...
1. You don't want to cruise too close to the shore which could result in potentially running aground on a low sloping sand/silt bar.
2. You need to transition from one side of the river to the other when entering curves in the river (see 'curves' below)
When traveling DOWNRIVER staying in the current provides an extra boost to your mileage/GPH burn rate (you go farther per gallon used)
CURVES -
Curves in a river also can help -
Traveling DOWNRIVER - enter the outside curve to maintain the downriver flow benefit.
Traveling UPRIVER - stay closer to the inside bend - the flow here will be less, and closer to the bank will actually have a flow that flows slightly upriver...
The flow upriver may not be that much but you won't be fighting a downriver current.
** Again, caution and awareness are paramount to avoid snags which will settle in these slack areas or sand/silt areas where sediments have an easier time to settle out of the water.
Bank to bank transitioning - this can be a judgement call...
- is there boat traffic needing to be avoided? If so, how fast is it moving (aka - how much time is there to complete the cross river maneuver before becoming an obstacle to the aforementioned traffic?)
- How fast is the current to be crossed?
If crossing traveling upriver and a direct 90° crossing is done, the current will push the boat back downriver, causing a loss in forward travel (not ideal). Better to take a gradual upriver tack so forward (upriver) movement is maintained.
If transitioning heading downriver and you're attempting to stay in the current in an outside bend, it's less of an issue, just be aware of traffic in both directions. Barge operators stay closer to the main channel but will utilize current flow in something of a similar fashion, when it's feasible to do so. It's handy to have the river help when you've got a large tow whose draft is 7' below the surface and the current flow can help you move along.
Bill
) " current manipulation".