Which you may think I know very little about.
A note from BSM.
Until comparatively recent historical times, there were no quick and easy ways of adjusting the gearing of the oarsman's equipment.
There weren't (m)any female rowers either, so this is an ancient mariner's tale, and a mildly sexist one, too.
The most often needed and most often applied method of trying to accommodate mechanically to adverse conditions was to call on the crew to adjust themselves and their technique into the wind: "Shorten up! Rate up!". And more or less conversely when fair sailing.
But if your crew was sufficiently important and competent to merit such fine tuning - as was clearly the case of Proud Grandparent Michael Lapage's 1948 Olympic VIII - he notes ".......the Leander (pencil) blades were shaved down because of a very strong headwind." "Pencils" and other weapons of rowing need a separate article, but for the benefit of those less familiar with the 1950s and earlier, here is a brief explanation of "shaving down the blades" to make rowing easier when faced by unforgiving headwinds.
Prior to an important race in conditions such that the coach was uncertain whether the crew's strength would match the gearing, and/or, its stamina survive the course, he would persaude (another word for JMB's speeling B, q.v.) the boatman to shave some 1/8" to 1/4" off both the long edges of the blades (=spoons). These were constructed of wood, about 2'(=2 feet)long and some 6" (=6 inches), a fraction, wide at the tip; probably, sitka spruce + mahogany or other hardwood were used so the "shaving down" was done with a wood-plane or indeed with a 'spokeshave' to remove the bulk of the offcut first.
Thus "shaved down" the blade was able to slip in the water during the 'pulling' phase and so ease the gearing - the rate of striking could be kept up or at least seemingly higher than normal to allow the boat to be slowed down less during the 'run' phase.
The boatman used to remonstrate over this violation of "his" equipment - not least because he would find himself invited afterwards to splice and fair in new strips of timber onto the sides of the blades to return them to their standard dimensions, overnight even! I have to say that the rowers very seldom appreciated this sort of dedication of the backstage crew - likewise many other niceties of the day such as re-leathering of fixed-pin collars to the looms, fitting new copper-foil tips to the blades, and so on. You had to be a very "heavy" and hippopotamusical coach to get away with it.
Relatively feeble rowers were often routinely given shorter blades and/or oars, in addition to rowing with narrower blades. This was a privilege quite often accorded to the 'stroke' of crews so that as a normal rule he enjoyed a less taxing sport, not perhaps too exhausted even in a hard fought race to be able to lead by example, smiling at the cameras, looking his best, with immaculate unpressurised rowing technique to match; and he could raise the rate at will keeping the "engine room" on its toes and crying out for mercy.
The less well physically endowed members of crews might have rowed routinely with narrower and shorter blades.
These days such extempore adjustments to the blades themselves are seldom resorted to - partly because of the difficulty and comparative non-reversibility of altering the width of plastic blades, and partly because there are so many other easier and immediately effective ways of adjusting the gearing. I was perhaps amongst the last of a dying breed to use this technique quite generally while coaching at Monkton. And I did have to rectify the damage myself, at least. But it is of course still true that younger men's and boys' crews and women's crews will usually row with suitably sized oars and blades and riggers to match their physiques, more or less.
But there is not much shaving these days.