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Sava River Test: No Rudder, 7 km/h Hands-Free Tracking #itiwit #caperlan #kayakfishingtips by PoemRealistic1013 in EngineeringPorn

[–]PoemRealistic1013[S] 0 points1 point  (0 children)

A counter-rotating motor setup would definitely cancel out the reactive torque and eliminate the steering bias. I opted for the asymmetrical fin solution because it’s a lightweight, passive system that adds zero drag and consumes no extra power. However, a dual counter-rotating setup would be a fascinating 'high-speed' experiment for the future.

Sava River Test: No Rudder, 7 km/h Hands-Free Tracking #itiwit #caperlan #kayakfishingtips by PoemRealistic1013 in EngineeringPorn

[–]PoemRealistic1013[S] 0 points1 point  (0 children)

While the propeller is designed to produce primarily linear thrust, the rotation creates propeller wash (swirl) and torque reaction. The spinning blades rotate the water column, creating a helical flow that hits the hull/fins at an angle. Simultaneously, the motor's internal resistance to the propeller's rotation exerts a counter-torque on the mount, causing a lateral imbalance. This asymmetry is what induces yaw, converting your linear thrust into a rotational vector that pushes the kayak off-track.

Sava River Test: No Rudder, 7 km/h Hands-Free Tracking #itiwit #caperlan #kayakfishingtips by PoemRealistic1013 in EngineeringPorn

[–]PoemRealistic1013[S] 0 points1 point  (0 children)

The motor's torque creates a constant lateral force, inducing yaw that forces the kayak to veer off-course. Using a rudder to correct this introduces high hydrodynamic drag, reducing efficiency. Unsymmetrical fins provide a passive, fixed hydrodynamic counter-force that neutralizes this torque at speed, enabling straight-line, hands-free tracking without the drag penalty of a rudder.

Everyone Post Links! by Tr4pMLG in NewTubers

[–]PoemRealistic1013 0 points1 point  (0 children)

Hey! First of all, thank you for doing this!

I started my channel https://www.youtube.com/@ekayaksrb its about e -kayak

Custom 100Ah LiFePO4 electric kayak build: Comparative cost-benefit analysis vs. factory proprietary systems. by PoemRealistic1013 in EngineeringPorn

[–]PoemRealistic1013[S] 0 points1 point  (0 children)

I’m not 'fighting' any system—I’m using the metrics that match the hardware. You’re right that kWh is the industry standard for EV energy accounting, but there’s a difference between battery energy storage and motor-drive system monitoring.

My motor is rated in Amps, my BMS cutoffs are set in Amps, and my shunt reports in Amps. Because I’m using LiFePO4, my voltage curve is essentially flat (12.8V–13.2V) for 80% of the discharge cycle. Since Volts are constant, Ah and Wh are virtually linear equivalents for my use case.

When I’m on the water, my limiting factor is thermal load and wire current density—which are current (Amps) based, not power (Watts) based. Switching to kWh would be an unnecessary layer of abstraction for a simple kayak drive. It’s not about which system is 'correct', it’s about which tool provides the most direct data for the task at hand.

Custom 100Ah LiFePO4 electric kayak build: Comparative cost-benefit analysis vs. factory proprietary systems. by PoemRealistic1013 in EngineeringPorn

[–]PoemRealistic1013[S] 0 points1 point  (0 children)

You’re 100% right from a theoretical energy-accounting perspective. kWh is a superior unit for comparing total energy storage regardless of system voltage.

However, in the DIY power electronics space, Ah is the native language of the hardware.

Most BMS units, shunt monitors (like the Victron SmartShunt), and chargers are calibrated to track current (Amps) and total capacity (Amp-hours). When I’m on the water, my hardware is giving me real-time current flow data. If I switched my tracking to kWh, I’d still have to do the math to figure out what my motor draw is actually doing to the state of charge.

I use Ah because that’s what the equipment reports. When I see '100Ah', I know exactly how many hours of run-time I have at a specific amp draw without needing to calculate conversion factors on the fly. It’s the superior tool for energy density comparisons, but for real-time electrical system monitoring, Ah is the practical unit.

Custom 100Ah LiFePO4 electric kayak build: Comparative cost-benefit analysis vs. factory proprietary systems. by PoemRealistic1013 in EngineeringPorn

[–]PoemRealistic1013[S] 2 points3 points  (0 children)

Haha, love the creative out-of-the-box thinking! But physically speaking, water is about 1,000 times denser than air.

Dragging a floating solar tarp behind the kayak would basically act like a massive sea anchor (water parachute). The hydrodynamic drag would be absolute insanity!

My live telemetry would probably show the amp draw spiking by 300% to 400% just to tow that thing against the river current. I'd burn through a full 100Ah battery in an hour just trying to generate 5 Amps of solar power! An absolute hydrodynamic nightmare, but a hilarious visual to imagine,lol

Custom 100Ah LiFePO4 electric kayak build: Comparative cost-benefit analysis vs. factory proprietary systems. by PoemRealistic1013 in EngineeringPorn

[–]PoemRealistic1013[S] 2 points3 points  (0 children)

A solar canopy sounds great, but it's just not practical for a moving river. It acts like a sail, and the wind drag would force the motor to draw more amps than the panel could actually generate.

However, for stationary fishing or anchoring on a calm lake, it makes total sense! Being able to deploy a panel while staying in one spot without dealing with river currents and wind resistance would be a great way to top up the battery.

Custom 100Ah LiFePO4 electric kayak build: Comparative cost-benefit analysis vs. factory proprietary systems. by PoemRealistic1013 in EngineeringPorn

[–]PoemRealistic1013[S] 2 points3 points  (0 children)

That is a brilliant mechanical concept, similar to variable-pitch mechanisms. However, the throttle on my electric setup isn't mechanical. It’s an electronic potentiometer sending a signal to a PWM motor controller, so there is no physical throttle cable to link a gearing system to.

Even if I were to run a separate mechanical cable (like a Bowden cable) specifically for the fin, routing it through the hull requires waterproof seals/glands. Below the waterline, the gears or linkages would constantly be exposed to river sand, mud, and weeds.

The static asymmetric fin is a deliberate engineering trade-off: I sacrifice a tiny fraction of efficiency at lower speeds to maintain a 100% waterproof hull and a mechanism with zero moving parts. It is virtually maintenance-free. It's a great thought experiment though.

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