While the jury is still out on whether time trials are an acceptable substitute for (or as some propose are better than) heats for determining advancement, time trials have proved an efficient way to take care of preliminary races, probably more than you might think-- many high school races, the Youth Nationals, the Dad Vails, the US National Team Trials and even World Cup races use time trials as part of the progression.
However, a time trial, where crews race against the clock and have only limited racing interactions with other crews, comes with its own challenges and quirks. Here are a few things to keep in mind as you prep your crews for time trial racing.
Tweak Your Race Plan, Know Your Numbers
With the addition of a starting chute, time trials cut about 100 meters off the race course, so crews are now racing 1900 meters, or 1400 meters at some scholastic events. Some coaches will keep their race-opening high stroke sequences the same, and have their crews stride for a shorter distance before executing the last portion of their overall race plan the same.
Other coaches, cognizant of the fact that the race will be approximately 18-25 seconds shorter (at a 1:30 split, 100 meters is 18 seconds; at a 2:00, 100 meters is 24 seconds), will have their crews up the intensity midrace, or earlier in the closing sprint.
If you are used to tracking your time for each 500 meters, it can often help to use the math just above to calculate a "first 400 meters" split so you know if you crossed the first course marker on pace.
So for example, if you typically row a 1:30 first 500, subtract the 18 seconds as noted above, and you should get to the 500 meter buoy about 1:12 (1:30 - 18 seconds) after you cross the start line.
International time trialling
Since crews are doing a rolling start into the time trial as opposed to a standing start, it's worth making sure your crew is getting up to speed efficiently, and not spending valuable time on the course, and as such "on the clock," getting to full speed. As the build is called, a crew will want to take a solid series of strokes aimed at getting the boat up to top speed, and aim to hit the course at speed. As most elite coaches (or evidence from a stroke coach or GPS) would tell you, it takes 8-10 strokes to hit top speed, even in experienced crews.
It's Not Your Usual "Sit Ready"
Even with most regattas having established procedures for time trials, every time trial will be officiated a little differently. Especially in large events, where the crews will queue for some time before actually getting on the course, lining up for a time trial will feature a lot of "behind the pontoons" action as crews get lined up, drift due to current and/or wind, fall out of order, and such like, while all the time the officials will be working to keep the proceedings on track, not least out of a concern over fairness.
Know where you need to be
It's not possible to game out every scenario that might happen, but every crew launching for a time trial should have a solid idea of their race time, what their number and start position are in the race order, who is ahead of & behind them, as well as the necessary cool-headedness to ask an official or referee for instruction if things on the water start to go haywire.
In essence, it's a lot like lining up for a head race, but with a couple critical differences.
First, you will typically be going into a single race lane, as opposed to through a chute and then onto a wider course, so having a good point and getting yourself straight in your lane is essential.
Second, you'll often be going through the start at a much higher rating and speed than at most head races - it's just a more intense and wild way to get going than the typical "three to build, you're on the course"
Be Your Own Backup Timer
Even with bow numbers and automated timing and finish line cameras, there's no guarantee that the timing will be accurate. With this in mind, it's usually a good idea for coxswains or scullers to keep their own on-board time for a time trial, their bow numbers (if provided) as well as being aware of any other crews around them that may have been rowing out of order. In the event of a timing inconsistency, being able to provide as much context as possible to regatta officials will be hugely helpful.
It Might Be More Than a Heat
In most cases, time trials are intended only to advance crews from the preliminaries to heats, semifinals, and finals. But as anyone who has attended a few multi-day regattas knows very well, weather can sometimes change suddenly, and sometimes so much for the worse that later rounds of racing, finals, or indeed entire regattas have been cancelled due to weather. In these cases, regattas that run a time trial as part of the schedule have used the results from the time trials to seed finals, directly award medals, or even qualify crews for the Youth National Championships.
In other words, your time trial may end up meaning a whole lot more than which lane you have in the semi or final. If the stakes are high, coaches and crews may be best served by ditching any sort of conditional race plan and going for the full pull in the time trial; if you've done your training, going for it in the time trial probably won't hurt you.
Don't depend on other crews to push you