Comments by "justanothercomment" (@justanothercomment416) on "Undecided with Matt Ferrell"
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Most of the comments here don't really understand what's going on here.
This is really about fixed pitch props. This is also true for aircraft. Their highest efficiency occurs when the forward movement matches that of the prop's pitch relative to the RPM setting. Remember a prop is a screw. If the forward movement of the screw does not match that of the pitch/RPM, it is an inefficient use of energy. Accordingly, it's not that this new design is so amazing efficient. It's that fixed pitch props are so amazingly inefficient at all RPM settings outside of their ideal pitch/movement. Accordingly, 105% is easily believable and likely very accurate.
That said, contrary to the video's false assertions, this technology likely has little use outside of tri/quads and small boats. As props get larger and larger they are intended to spin much more slowly, if for no other reason than to avoid super sonic tip speeds (example, helicopters and cargo ships). The larger the prop the less likely they are to have high RPM requirements. Which is in large part why the prop blades become wider. In other words, they get their performance from size, not speed (RPM). This also means the operating RPM window is drastically reduced (1500-6000 RPMs (4500 rpm window) vs for example, 100-250 RPM (150 rpm window), of a large cargo ship). This in turn means a large ship's propeller is much more likely to always operate at or near ideal RPM whereas the smaller boats commonly transition to and fro as their standard operating environments. Accordingly, the inefficiency is much more commonly observed. In turn making the efficiency improvements a much larger percentage of it's overall fuel consumption as it commonly spends more time as it transitions in the less ideal RPM range.
For example, a small craft likely operates around 20% of it's life in transition. Whereas a large ship likely operates 0.0001% of it's life in transition, with a much smaller window for transition. Accordingly, a well optimized fixed pitch is almost always be ideal for large cargo ships. Additionally, for things like wind turbines, most prop aircraft, and so on, they already have variable pitch props, which addresses this inefficiency.
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@KoRntech It's actually not surprising for fixed pitch props. This is also true for aircraft. Their highest efficiency occurs when the forward movement matches that of the prop's pitch relative to the RPM setting. Remember a prop is a screw. If the forward movement of the screw does not match that of the pitch, it is an inefficient use of energy. Accordingly, it's not that this new design is so amazing efficient. It's that fixed pitch props are so amazingly inefficient at all RPM settings outside of their ideal pitch/movement. Accordingly, 105% is easily believable and likely very accurate.
That said, this is also likely why OP's comment is also true. As props get larger and larger they are intended to spin much more slowly, if for no other reason than to avoid super sonic tip speeds. The larger the prop the less likely they are to have high RPM requirements. Which is in large part why the prop blades become wider. In other words, they get their performance from size, not speed (RPM). This also means the operating RPM window is drastically reduced (1500-6000 RPMs (4500 rpm window) vs for example, 100-250 RPM (150 rpm window), of a large cargo ship). This in turn means a large ship's propeller is much more likely to always operate at or near ideal RPM whereas the smaller boats commonly transition to and fro as their standard operating environments. Accordingly, the inefficiency is much more commonly observed. In turn making the efficiency improvements a much larger percentage of it's overall fuel consumption.
For example, a small craft likely operates around 20% of it's life in transition. Whereas a large ship likely operates 0.0001% of it's life in transition with a much smaller window for transition. Accordingly, a well optimized fixed pitch is almost always be ideal for large cargo ships.
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@andrewallen9918 That's exactly right. This is not a universal improvement. The operation of the boat makes a big difference. If the boat is mostly parked fishing and slowly moving around from point to point, then there will be almost no benefit. Ideally this prop helps those who frequently go from idle to plane and back again, with a ton of "on plane" cruising for extended periods. This is because it improves the transition period from idle to on plane and to a much lessor extent, the on plane economy. But if you look, you can see the constant speed prop does eventually catch up once on plane, but at a higher RPM; which is where that fuel savings is really coming from. And the basis of comparison is fuel economy, not speed. Want that fuel savings? Get a normal prop designed to operate at that RPM.
This also implies the prop used for comparison is not ideal of the desired operating RPM. In prop design, they generally design for a single ideal RPM (raising the question if the comparison is really on the up and up). Meaning there is likely a more ideal prop selection, for the ideal torque, for which they should compare. Additionally, to benefit from the smaller prop efficiencies, you need to be at that RPM for extended periods of time. Sure you'll always benefit once on plane and no longer accelerating, but if you don't commonly cruise for extended periods, it represents a tiny overall percentage the engine is running. Which means it represents a tiny overall percentage of fuel economy.
This is one of those topics where the devil is in the detail. And contrary to the video, it's far from anything approaching a generic, general purpose improvement. So yes, absolutely, this is a niche product. Though I expect for those within the niche, it is a good product. Good for the price? Hmmm. If you're outside the niche, not so much.
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Your gains will be determines by how often you transition from stopped to "on plane" travel. If you do this frequently, there is likely some benefit to be found for you. Though the noise benefits will always remain. If, however, you spend most of your time parked or most of your time at a specific RPM, ideal for your existing props, you'll find very little fuel benefit.
It's actually about fixed pitch props and how they operate. This is also true for aircraft. Their highest efficiency occurs when the forward movement matches that of the prop's pitch relative to the RPM setting. Remember a prop is a screw. If the forward movement of the screw does not match that of the pitch, it is an inefficient use of energy. This is why the transition period (how long it takes to match the pitch/rpm/forward speed) is so important. Accordingly, it's not that this new design is so amazing efficient. It's that fixed pitch props are so amazingly inefficient at all RPM settings outside of their ideal pitch/movement. This is why the use case matters. The more time you speed at your prop's ideal RPM the much smaller the benefits are from these props. Notice in the graph the fixed pitch does eventually rise.
For example, a small craft likely operates around 20% of it's life in transition. Whereas a large ship likely operates 0.0001% of it's life in transition with a much smaller window for transition. Accordingly, a well optimized fixed pitch is almost always be ideal for large cargo ships. While there is some benefit from these props, you really need to focus on the ideal RPM differences and how you use your boat.
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