How Far is Far?
by David R Getchell
(Excerpted from Small Boat Journal-September, 1990)

Accustomed as we are to the mile-eating comfort of the automobile, distance on the water is deceptive. From the waterlevel deck of a sea kayak, a destination seen 10 miles away over open water may look 10 times that figure; if a headwind is blowing, that destination may be unreachable.

If one owns a motorboat capable of 25 mph, a point 50 miles away may appear on the chart to be only a couple of hours or so away; on the water it may require the better part of a day to reach that point.

A sailboat skipper, who rarely travels in a straight line, may be more realistic in judging the distance his boat can cover in a day, but as he well knows, "if the wind don't blow, he don't go."

Given the fickleness of water travel, are there any figures one can use in planning a cruise? The answer is yes, but with the understanding that as conservative as they are, even they may be optimistic. Over the period of a few days, however, they will probably even out.

The formula for cruising distance is deceptively simple: D(istance) = t(ime) x s(peed). Reality is more like this: D(istance) = t(ime) x s(peed) ± w(ind) ± c(urrent) ± p(hysical condition) ± h(ull type) ± l(oad) + c(arries) ± a(nything else) that will affect your getting from start to finish. Nevertheless, I have found the following numbers fairly reliable:

  • For self-propelled boats, 10-20 miles a day, with 15 miles an average.
  • For small sailboats, 20-40 miles a day, with 30 miles an average.
  • For motorboats (not speedboats), 40-60 miles a day, with 50 miles an average.

Water distances are never what they seem to be

These figures are based on conservative speeds over 5-6 hours of actual travel time, with much of this compiled before noon. Why quit so early? Normally, the nighttime temperature of water and land nearly evens out, resulting in little or no wind. The rising sun reheats the land, causing air movement from the cooler water to the warmer land. Convection currents may also occur over land alone, thus raising wind speeds. By noon, these breezes frequently build to where they can seriously interfere with small boat travel. On the other hand, the sailboat may have been becalmed through much of the morning and is now able to make up for lost time.

Of course, there are those fine summer days when a big high pressure system sits directly overhead and winds are light all day. Count these as bonus days, the ones that offset gloomy rain and snarling headwinds.

In planning a long trip, one may be tempted to give the factors that work in one's favor greater weight than those that hinder progress. The sad truth is that many of these factors work both ways.

Current is a good example. A swift river may move a loaded canoe along with exhilarating speed, but steep rapids or falls may force a difficult portage that cuts the average day's travel time in half. Favorable tidal currents can give a big boost to a kayaker, but if that same current beats against a stiff headwind, the breeze and steep waves it creates may stop you cold.

Frequently overlooked in the excitement of charting an extended voyage is one's physical condition, especially if the trip is to be made in self-propelled boats. Rowing and paddling are Mistering work for unconditioned hands. Even standing or sitting for hours in a moving motorboat can be tiring. If you are traveling in company with others, differences in condition can force major changes in the trip plan.

Another consideration easy to forget is the boat itself. Hulls vary greatly, and incompatible hulls can slow progress. Length is the critical factor here, both in displacement and planing boats. In a displacement hull (sea kayak, canoe, rowboat, most sailboats), speed is a factor of length: the longer the hull, the faster it will go, other factors being equal. In planing boats, length is important in spanning the distance between wave crests: A planing boat rides on top of the water and will stay flat as long as its bow can bridge the gap between crests. When it can no longer do this, it begins to pitch, and one must slow down to displacement speed or speed up to the point where the boat is literally jumping between crests. A prudent cruiser slows down.

The sea is not an unvarying paved highway, but rather a "living" thing capable of sudden change. The smallboat cruiser must understand these changes and be ready to compensate for them.