Hydroplaning Rowboat

[Skip Johnson]

Anybody remember elliptical drive sprockets? But it doesn't work with oars AFAIK,,,

They do work for pedal powered paddles.

 

[gonzo]

sliding riggers (oarlock frame slides back and forth instead of the rower) are both superior but not allowed.

Have you found data on side by side races? I would be interested on reading on it.

Anyway intermittent higher power output is significantly harder than constant lower. Lifting 10kg 10 times at decent pace is way easier than lifting 100kg once in a while (1/10th frequency)

A power lifter may generate more power at a lower rate of lifting. It depends on the person and what the goal is. Intermittent power may have a higher average but not be adequate for the application. Do you have any data to back the claim as to the amount of generated power? As an engineer I question these kind of claims, but I'm also curious to find out if someone actually performed some tests or is only an opinion. Also , as Kerosene pointed out, power and force are different units. They often get consider the same colloqially.

 

[kerosene]

not seen side by side races but when they were allowed all top athletes used them until banned. It seems pretty reasonable that such boat performs better. There is far less pitching motion, less effort to change mass direction (rigger weighs fraction of the rower) and the speed variance during the stroke as a result is smaller. As resistance is exponential to speed average speed with less variation is more efficient.

looks kind of neat

And bikes, UCI has dictated frame needs to be traditional triangle. Not much room for innovation there.

as far as rowing and cycling wattage differences - didn't carefully look for scientific data but anecdotes are plenty - it's common knowledge. Why exactly it is might not be so clear.

"How about those of you who do both (Goblin maybe?) How do your values compare? Someone has suggested a 25w difference but for me it is WAY more than that. Now, granted, I am much less fit when it comes to rowing than I was for cycling, but my differences are huge. For 7 min erging i do 258 vs 330-350 for cycling. I do 210w for 40 min yet I used to do 310-330 for an hour cycling."
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Above is from C2 forum but you find similar anecdotes both by people who are primarily cyclists and primarily rowers. The lifting case is pretty clear. I can do set of 15 with 100 kg but can't do set of 5 with 300kg (or even one). Now the latter is bit different case as it has nothing to do with aerobic or even anaerobic effort but max strength.
Different sports also have different heart rate values for aerobic and anaerobic thresholds. IIRC it i at least partially to do with how the movement helps blood flow - cycling movement itself assist in the pumping of blood more than some other sports.

 

[gonzo]

I can do set of 15 with 100 kg but can't do set of 5 with 300kg (or even one).

The equivalent power of 15 reps with 100Kg would be say 150 with 10 or 1,500 with 1. However, because the body is always moving the same, there is a loss that can't be reduced. There is a point where the efficiency maximizes. As far as cyclists vs rowers, the first is an endurance sport and the second a sprint.

 

[kerosene]

While rowers don't row typically hours on end (when competing) the most profilic distance, 2000m is not a sprint.

It's takes 5:30ish for the elite, and elite train mostly (80-90% of training time) steady state low heart rate endurance. Also the same guys who have 2k indoor records also have records in longer distances. Take Joel Naukkarinen who has 100k WR and had (possibly still does) marathon distance record. He competes on beach sprint and other coastal rowing background in classical Olympic.

And the numbers above were for 1 hour or 40 minute efforts.

 

[Horton HCCI]

intermittent higher power output is significantly harder than constant lower.

Hi, Kerosene! Thanks for weighing in.

Well, a few things--

First, do you mean harder as in more draining, or more difficult to get the same average power output? On power output, I'm going on the graph I posted earlier (p. 7 of this thread) comparing sliding and fixed seat, free and constrained rowing, and pedaling. Average power from fixed-seat constrained rowing was highest over all durations measured, up to 5 minutes. Granted, that's one data point. I know from watching pro cycling that a champion athlete can maintain ~400 watts over about 20 minutes, and a specialist can generate 1500-2000 watts over a 10-second sprint. I don't know whether or how that translates to pedaling in water.

Let's see if I can find some published data on rowing power...450-550 watts over 2000m, per this: Olympic Rowing – Maximum Capacity over 2000 Meters https://www.germanjournalsportsmedicine.com/archive/archive-2021/issue-4/olympic-rowing-maximum-capacity-over-2000-meters/. Here's another, also ~550: https://worldrowing.com/wp-content/uploads/2020/12/3Chapter10_English_Neutral-1.pdf. Comparable? Rowers don't tend to do 100m sprints, true, but there's this (start around 0:23): youtube.com/watch?v=kUTzDAu0O48&time_continue=28&source_ve_path=NzY3NTg&embeds_referring_euri=https%3A%2F%2Fwww.boatdesign.net%2F. No erg. But fast. 60 spm.

Then, I don't think I agree that pedaling an exercise bike is an example of generating "constant" lower power. Pedaling is converting oscillating, thus intermittent, input from repetitive muscle contractions in the legs into rotary power by means of cranks, correct? So it's not exactly constant, particularly in water, unless a flywheel is used, and even then. It's pulsing. Pulsing at a higher frequency than rowing, but pulsing nonetheless. And the conversion from oscillating to rotary has the very significant downside of having dead zones at the top and bottom of the pedal circle, where the cranks have no leverage. No leverage, no torque, no power at those points. And pedaling in water, where there is no "coasting" through the dead zones, is extremely fatiguing, I think most will agree. I sure hate paddleboats. They make me feel like more of a wimp than I already am.

My take is that human physiology is actually better suited to long, slow, high-leverage, powerful strokes with long rest periods rather than short pulses with almost no rest. But this may be wishful thinking. There is the consideration that a pedal circle is around 350mm (35 cm), while a row stroke (pull length on ergometer) can be anywhere from 100 cm to even 150 cm for really big, rangy specimens. A row stroke can also generate a lot of swinging momentum.

flapping drive will do complex mechanical tricks to get the blade to run at the optimum angle of attack. At best it will do it "quite large portion of time". A propeller will do this all the time.

Well, a propeller won't run at a constant optimal angle of attack between low and high boatspeeds, unless it uses variable pitch. Decaviator was fixed pitch. The only variable pitch HPV I'm aware of was Super Phoenix, the current tandem record-holder at 18.65 knots. They had around a 9" diameter counter-rotating prop with a "gap" (slot) that I think was opened at low speeds to direct flow into the blades at an angle, thus simulating finer pitch.

(start about 1:56).

But you're right, getting optimal AoA with an oscillating foil is a trick. Especially when you consider that not only does boatspeed shift apparent flow forward, but speed and force vary over the course of a single pull (and return). I have an idea how to accomplish this, but I haven't tested it. It's not mechanically complicated, and is in fact very simple. But folks seem to find it very difficult to get their heads around, so I'll refrain from trying to explain unless anyone really wants me to.

 

[Horton HCCI]

Newton is not a unit of power. It is unit of force. My deadlift max is in the 150kg range ie. 1500N range. With levers I can go past that. But that is not how you measure what you need. You need to measure power which is work done in certain time. 500m record indoor rower Phil Clapp can hit above 2hp ~1500W+ which is very formidable. over the 500m record the average is around 1050W. About as elite as it gets for rowing. He does weigh well above 100kg though.

But my point weas to measure what that flying boat needs you need to know speed. P=FV (power=Force*speed), at low speed high forcer is not an impressive achievement (think the lowest of low gears).

Hmmm...I'm aware that Newtons are a measure of force not power, so what might I have been thinking of? I guess that thrust is force, and that's what the video specified. I apparently tried to equate that with max force on a footplate, but that doesn't seem like a very relevant comparison at all. Yah, scratch that.

Aha--1050W, you say. Over 500m, so say 1:30? 1:30 might be around 1500m on a track bike. Looking up: Relative importance of pacing strategy and mean power output in 1500-m self-paced cycling - PubMed https://pubmed.ncbi.nlm.nih.gov/19850573/437.8W average, 828.8W peak. "Regionally competitive cyclists." All this says to me without going into it too deeply that rowing output can pretty easily meet or exceed cycling output, at least for short-ish distances.

Also, bear in mind I'm not really interested in comparing land cycling to rowing, I'm (not) considering water pedaling as an alternative to rowing. AI is giving me stuff from boatdesign.net, saying 400-600 watts to get on foil, 150-250 watts to stay on foil. I have a fairly strong sense that 400-600 watts won't be enough to get on PLANE, which is what I'm interested in. Big (currently planning around 5" chord x 15" span) dual foils at near-maximum pitch (~13-14 deg) over a 1500-2000W, 3-sec burst, is the current plan. Nevermind watts, what I think we really want here is massive low-speed force with a large (huge) foil/water interaction area. Around 16 times a water prop, or maybe 12--I've been revising my foil area downwards of late for various reasons.

 

[gonzo]

While rowers don't row typically hours on end (when competing) the most profilic distance, 2000m is not a sprint.

Probably a sprint was not the most accurate description, I used to crew. My comparison was the 6 minutes of rowing with the hours of cycling. Maybe stating the duration goal would be important for the discussion.

 

[kerosene]

Indoor rower numbers
500m, 1:09, ~1000W
1000m, 2:38.1 ~700W
2000m, 5,33.4 ~600W

these are world records so don’t expect even very fit person to get very near these numbers.
On my 100m record, 16.x seconds, I had 2 strokes where I got just over 1hp =736W

i dont know how these compare to bikes, I think on the short stuff rower might have advantage from using more muscles. But as you transition to endurance, on a bike a person can output more watts.

 

[gonzo]

Indoor rowing machines do not measure the forward thrust of the stroke recovery. At the end of the stroke you body is leaning backwards, the fast recovery to a sitting position pushes the boat forward. However, for the purpose of this thread I believe a steady pace for a longer time is the power to consider.

 

[Horton HCCI]

Indoor rower numbers
500m, 1:09, ~1000W
1000m, 2:38.1 ~700W
2000m, 5,33.4 ~600W

these are world records so don’t expect even very fit person to get very near these numbers.
On my 100m record, 16.x seconds, I had 2 strokes where I got just over 1hp =736W

i dont know how these compare to bikes, I think on the short stuff rower might have advantage from using more muscles. But as you transition to endurance, on a bike a person can output more watts.

Useful data, thanks!

Hey, would you like to volunteer to pilot my silly boat, should I ever get it built? You sound like a pretty serious athlete. I'm certainly not fit enough to generate enough power to get any results worth analyzing. If you accept, maybe that'll give me the impetus I need to get off my butt and start really digging in to building. Will be a bit of a trick to get it shipped to Finland, though.

PS--It's a sliding rigger, or sliding rigger-inspired, if that's an incentive. You'd be guaranteed to get stares.

 

[kerosene]

I am not a serious athlete.
I recreational 48 yo hobbyist who follows the elite folks to inspire myself.

 

[Horton HCCI]

I am not a serious athlete.
I recreational 48 yo hobbyist who follows the elite folks to inspire myself.

Ahhh....bummer! Well, worth a try. But don't sell yourself short. 736W is nothing to sneeze at.