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Comparing Stroke Lengths

On Sunday 9th July, my masters crew were assigned a quad, however we are somewhat overweight for the usual one we are assigned, it notionally has an 85Kg average crew weight (more like 75Kg) and most of us are over 90Kg, so it tends to behave more like a ‘submarine’ (water level is usually around the same height as the boat name) and everyone ends up ‘digging’ their oars too deep.

The coach agreed with us and signed out a more suitable boat with a 95Kg average weight that just happened to have an Nk EmPower Oarlock installed on the stroke side of every seat.

This presented an opportunity for me to pair my NK SpeedCoachGPS with the oarlock for my seat and gather some metrics for when I am not having to concentrate so much on keeping the boat level as there are 3 others who can help in that regard.

After getting used to this boat being way more ‘tippy’ than the ‘submarine’ and finally balancing it, we actually had a good outing.

This is a baseline set of metrics from when I was in my single, going at around 30spm at Gloucester HORR (before I hit the tree) but felt I had reasonable slide use and arm extension, despite the terrible conditions.

My son was down again today, so I decided to take my single out for a quick session 4,251m.

We can see I have about equal catch and finish angles, stroke length of 81 degrees and an effective power stroke of 55 degrees (not exactly great).

Compare this with a ‘race piece’ we did in the quad against the senior men, where I was also doing around 30spm.

Here we can see about the same catch angle, so I had probably shortened up a bit, a higher max force, 447 vs 392, that was achieved much sooner and a greater finish angle resulting in a greater effective stroke length of 61 degrees.

A later piece in the quad, where I was focusing more on technique at 19spm, just before we came in, had the following metrics:

A much better catch angle of 50 degrees, around the same finish angle, but now has an effective stroke length of 65 degrees, which is way better than the 55 degrees in my single.

As an example of how much I shorten up when the confidence goes, this is from my journey to the start at Gloucester into a 25mph gusting headwind at about 24spm:

Here we have an effective stroke length of only 33 degrees, probably using half slide at best.

This is a graph from my single where someone else was rowing it back to the boathouse at Gloucester at 20spm, while I was being returned by road after my ‘swim’.

Here we can see an effective stroke length of 83 degrees, he has a similar finish angle to me at 46 degrees, but a much better catch angle at 53, that I only come close to in a quad.

Looks like I still have a long way to go with regards confidence and increasing my stroke length in the single.

All sessions made use of my C2 Skinny Comp oars, which feel like I have a good connection in my single, however the gearing is almost certainly wrong for a quad as I hardly felt any connection with the water and although I was putting down more power than my single, it felt like I was applying way less.