Is the head of navigation same for sailing and motorboats?

Question

Rivers are often described as having a 'head of navigation', the furthest upstream point you can reach in a ship coming from the sea. Does this equally apply, regardless of propulsion method?

In particular, thinking about sailing boats, even small ones, it seems to me they might need more width on a river to be able to tack, or just generally respond to changing wind conditions?

I have seen it claimed that one of the reasons for the historical shift from ocean transport by sailing to steamship was because sailing ships had difficulty in the Suez Canal for that reason. Though that was large ships, and here I'm just thinking about small boats, suitable for operation by one or two people.

Do small sailing boats actually have more difficulty going upriver, than motorboats of the same size?

Answer 1

The head of navigation is entirely subjective.

It depends on the type and the size of boats, which have different requirements. The river Thames in UK, for example, has several locations that limit navigation.

• London Bridge was the traditional limit for tall ships due to their mast height

• Richmond lock marks another limit, restricting the width of vessels

• Further upstream Osney Bridge at Oxford has the lowest headroom on the Thames

• Above St John's Lock at Lechlade the river is only suitable for very small boats

A sailing boat has more restrictions than a motor boat

• It has a deeper keel so needs greater river depth

• It has a taller mast limiting the bridges it can pass under

• It needs width to tack, so cannot sail far on a narrow river

So a motor boat can definitely navigate further upstream than a sailing boat.

It is possible for boats to navigate between features they can't actually pass: a boat may have been delivered by road on a trailer and launched on the river. The general limit though, is when there is a change of level such as a wier or natural waterfall, and there is no lock to raise or lower the boat past it. Even where there is a lock, there is a width restriction, for example the lock at Richmond is only 2m wide.

Answer 2

It is the motorboat. Definitiely

Draft
Any sailing vessel needs a mechanism to withstand sideways drift and heel. A yacht with an ordinary fixed keel will require at minimum 1.5-2m of depth but we are not limited to this. Draft is not only a problem in rivers but also in tidal areas so people have been creative by developing sailboats with retractable keels, twin keels and daggerboards mounted on the side which can reduce the draft to around 1m for sailboats carrying reasonable loads. Probably the most efficient hull with regard to draft can be found at beach cats which can sail in knee deep water if necessary.
By contrast, a motorboat does not require any keel, fins, etc. If is just limited by the depth of the screw and even that can be removed, for example in the swamp boats

Tacking
The draft of a swamp boat can already be considered full victory for motorboats but let us elaborate further on the topic of maneuvering. A sailboat can only sail at certain angles against the wind. Even a wider river will be a problem when the wind is blowing against you. Tacking may be possible but the VMG is considerably smaller than your speed through water. Additionally, on every tack the current will push one down, reducing the effectuve VMG even further. So already a rather wide river of 100m navigatable width will be a real problem for sail boats