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the_original_Retro t1_j3l5suy wrote

Pro tip: the legend detracts from a good graph when it's simple and already labelled.

But interesting graph though. Here's how I'd break it down from my armchair.

  • Rowing is about pure raw strength and medium-term endurance. Makes sense that it's the heaviest. The separate bulges are likely men vs women, with a light person being the one that doesn't row but calls the strokes.
  • Taekwondo, I'm assuming, has competitive weight classes, explaining the distributions?
  • Triathlon people are all wiry, stringy muscle and little body fat so they don't have to carry a lot of personal weight for the many miles/kilometers of the competition.
  • Fencing's somewhere in the middle - some fitness, but strength is important.
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Curious_Jellyfish_37 t1_j3l6pbd wrote

Good points except maybe the first - it looks like the chart is male athletes only? Just did a quick search... it's more likely that it's the difference between the unweighted and lightweight rowing (lightweight = weight-limited to 72.5kg for men). You can also see a blip for the coxswain (who tend to be about 55kg).

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RowBull t1_j3lgbbh wrote

On the rowing data, rowing has a light weight class that’s 72.5kg for men which explained the bulge in the middle. The minimum coxes weight is 55kg which explains the small bulge at the bottom as there is only one boat class that has coxes at the olympics.

The heavier you are the more power you need to produce to offset the extra weight (and therefore drag) you bring to the boat, where weight v height/power output can be accounted for. As Coaches evaluate weight v power for athlete selection, there is a wider distribution of weights for the heavier athletes.

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tomvorlostriddle t1_j3lle6z wrote

>The heavier you are the more power you need to produce to offset the extra weight (and therefore drag) you bring to the boat

Yes , but it's water and it's flat, not cycling uphill etc., this is easily compensated by how much easier it is to be powerful when you're heavier.

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RowBull t1_j3lopev wrote

I think weight has a bigger impact than you might think. Unlike cycling as rowing is in water. Water will generate a significant amount of drag which constantly effects the boat and the heavier your boat is the more drag you will generate. Secondly unlike cycling rowing does not have constant power application, each stroke will have approx 1s of power application and 1s of recovery as the rower takes the next stroke. This means that while oars out of the water the boat is relying on momentum, so minimising drag is key to reducing the boat slowing in the period. Additionally more force will be required to accelerate the boat at the start of each stroke with more weight. Finally a rowers weight will significantly move within the boat on each stroke against the direction of travel of the boat. This will cause the boat to slow with more weight.

Some coaches will weight adjust everyone’s times off the water for their crew selection because of these factors.

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MeatierShowa t1_j3malqs wrote

>heavier your boat is the more drag you will generate

Not according to this. https://www.rowinginmotion.com/drag-efficiency-rowing/

"the drag force attacking the hull is proportional to the square of boat velocity and a hull-specific drag constant ."

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Fossafossa t1_j3md04j wrote

More weight = sitting lower in the water = more wetted surface.

The more wetted surface of the boat the more drag it creates.

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pitooey123 t1_j3nbn9g wrote

Not necessarily, the boats are rated for certain weight classes so they have different buoyancy

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Coomb t1_j3o1j3f wrote

It is absolutely true that any particular boat will sit lower in the water if it's carrying more weight.

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Deto t1_j3ov4y5 wrote

Yep, if you take a boat and add weight the boat will sink until the additional water it has displaced equals the additional weight.

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oak_pine_maple_ash t1_j3p29qa wrote

in rowing the boats are designed around athlete's weights. So my boat is designed for a 130lb person, and my bf's is designed for a 180lb person. It's both longer and wider. We end up sitting around the same height off the water.

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SomethingMoreToSay t1_j3qa7hh wrote

Yes, but his has more wetted surface because it's longer and wider, hence more drag.

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Korvensuu t1_j3qqt1w wrote

as a simple example, you and your bf now swap boats

the lw boat your bf is in will be deeper in the water than when you were in it >> more drag

his boat that you're in now sits higher in the water >> less drag

the boats are designed for different weights but thats not really what we're looking at here, we want to know how much water is displaced as that determines the amount of water-boat surface contact surface area and hence the drag.

A scull rated to a heavier weight does this by being wider and/or longer, increasing the water-shell contact area [which is the key thing as by spreading your bfs weight over a larger area the boat 'sinks' less and has the right water clearance] and increasing the drag

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Coomb t1_j3sac93 wrote

You sure do, or at least I believe that you do. That doesn't change the fact that in order for the boat not sink, it has to displace slightly more than the weight of water equivalent to the weight of the boat plus all of its occupants. For any given boat, if you put more weight in it, it must displace more water (or be able to provide additional dynamic lift, but that's irrelevant for rowing sculls). Your boat and your boyfriend's boat have approximately the same freeboard, but his boat absolutely must have additional volume displaced below the waterline, and that necessarily induces additional drag.

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KrzysziekZ t1_j3p8hdn wrote

More wetted area or cross section must result in more drag. However, some if not more drag is wave-making drag (which is harder to model) and this is primarily dependent on length of the hull, which doesn't change with displacement.

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MeatierShowa t1_j3r37a4 wrote

The length of the hull doesn't change, but the waterline might, depending on hull shape. I think it's known in sailboats that if you load it down to increase the waterline you might get a little higher hull speed.

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CarpetbaggerForPeace t1_j3lnlqh wrote

I thought strength increases as r^2 and weight increases as r^3 so someone has to gain a lot of weight for harder and harder strength increases.

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tomvorlostriddle t1_j3m54cj wrote

yes, but you are not vertically climbing there, you are not linearly penalized for your weight

and rowing is also about amplitude

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KrzysziekZ t1_j3pbe75 wrote

Force increase as r^2, but energy or power available as r^3. That's why all animals jump (from being still) the same height, be it a flea, a mouse or a human. Cats are better, elephants can't jump at all due to their ankle.

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Adventurous-Text-680 t1_j3n3ro7 wrote

Easily compensated?

https://eodg.atm.ox.ac.uk/user/dudhia/rowing/physics/weight.html

Check section 8.

> So if a 85 kg oarsman pulls a 5 km erg in 19 minutes (=1140s), and a 70 kg oarsman takes 19.5 minutes (=1170s), their equivalent 'boat speeds', normalised for a 75 kg oarsman, would be:

> (8.8) (85kg): TB = 1140 / ( (90/100)0.167 ) = 1160s = 19m 20s > (8.9) (70kg): TB = 1170 / ( (90/85)0.167 ) = 1159s = 19m 19s

> i.e. a bit of a nightmare for the person who has to select between the two. (Using the 0.222 power would give times 1167s and 1155s respectively, so the lighter rower would win).

Now this is using accepted formulas for estimating rower performance on water based on an erg (indoor rower). So it's not perfect, but it's a great example of why not being bigger didn't mean faster. Remember drag is constant for all movement including coasting.

So in this example the 15kg heavier person would be about the same speed as the 70kg person. You can't assume that the extra weight will always be just muscle. Fat, bones, etc count as well. You are unlikely to increase just muscle (at best you will have a body fat percentage of around 5-8% for an elite athlete). So any increase in weight will carry dead weight as well.

Physics dictates that you need to increase displacement in order to float a heavier weight on water. The more water you displace the more water will be in your way when you try to move. Drag is drag and it affects you. People can only gain so much strength improvements with weight.

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pitooey123 t1_j3lh7ev wrote

Rowing for men is separated into two categories: heavyweight and lightweight. Lightweight is when the average weight of the people in a boat is 70kg with a maximum of 72.5kg, anything above that is heavyweight.

You're at an advantage when you're big and tall in rowing but there is some variety, depending on the type of boat and the person's position in the boat. This can lead to some difference in weight within the heavyweight category. For example, in an 8 person boat ("an eight") you can have someone at the front of the boat ("bow") who can be relatively small and light compared to the group in the centre of the boat (positions 3, 4, 5, and 6). It wouldn't be unusual for men in these positions to be >100kg.

Rowing is definitely not about raw strength. Like any sport, there's plenty of nuance and technique. The smaller person you tend to see in films "calling the strokes" is a misrepresentation of the job a coxwain or "cox" does. They are not present in all boat types. When they are, they steer the boat, act like a second coach during training, call strategic pushes and provide encouragement/feedback during races. They don't call strokes, or at least they don't at any level beyond your first day in a boat if they do at all.

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highcharts OP t1_j3l5xvb wrote

Thx for the feedback. You are right, this chart could be better without a legend. Thx again :)

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