I'm a relatively fit hobby cyclist and want to set myself a challenge for (mid) 2024, competing in a 6-hour TT challenge. It's a relatively flat to moderately hilly 18 km loop (1% average gradient, 185 m) and only paved roads, as you would expect. I am not planning to use any specific gear like skinsuits, aero bars due, I'm just going to do this on my endurance road bike in the best fitting kit I have and the result/rank isn't the main focus.
Here's the course profile:
I know that I can finish because it did comparable-length rides on my own, both indoors on Zwift and outdoors but since the indoor season is coming up soon, I want to do the majority of structured training over winter and on the trainer. Workouts on the road are not my thing because it is hard to find roads for steady efforts and keep focused.
"Relatively fit" means I'm doing endurance sports (running, cycling) for the past 10 years, current at ~3,8W/kg FTP at 37 years of age and I know can sustain about 2,5W/kg for 5-6 hours - I'm for sure not winning my age class but I want to take it seriously and not just show up with whatever form I'm in at the day of the event.
Based on these numbers and using bikecalculator.com, I'd be happy if I can do about 8-9 laps (~150-160 km). Judging by this year's results, I'd be somewhere solid on top of the bottom third but anything beyond dead last and riding the full six hours with good feeling counts as success. I am aware that my bike will be a limiting factor in this scenario. At least I know that being in the saddle for so long shouldn't be a problem position-wise, especially because a climb and descent loosen things up lap-per-lap, the course has a long straight, hills and there are a few technical bits due to the countryside location of the race.
That's the bike I am using (2018 Ridley Fenix SL, size S):
As I learned, it is not per se a lazy endurance frame and its STR ration of 1,41 rather sporty, even though I feel more upright and not really aero on it, but that's not the point of the bike, anyway. I had two bike fits and the position works well for me on long rides (the worst being 6+ hours on the trainer). I think, the fitter has somewhat compensated the geometry by keeping spacers on the stem but I have ridden about 10-15k+ over the last 3 years with this fit and wouldn't really want to change anything about it. There were observations that the saddle is tilted forwards but that was also a result of the fit since I seem to be a bit tail-heavy on the bike and even wheelied off trying to get back on the bike on ascents - and actually ride quite a lot of hills.
Here's my current power curve, nothing extraordinary, just as an indication where I'm at:
So, my ambition is just to be prepared and focus my indoor training rides on getting the best possible result with 2-3 workouts per week - I also commute approx. 2 hours per week. I'm not really keen on subscribing to any paid service (other than Zwift), so I'm asking for some general advice on what I should focus on.
Quite honestly, I don't have the biggest experience with structured training, last year I did a 2-hour hillclimb and mostly did 60/90-minute sweetspot units with occasional higher-intensity workouts and simulated climbs. That worked out pretty well because it was close to the actual challenge.
Is that something I could continue with or do I need to put in longer units at moderate intensity to avoid falling off the cliff half into the race?
(Of course, fueling will be yet another topic but I think that's something we can ignore here for now)