Minnesota Classic Glastron Forum
General Category => General Discussion => Topic started by: dorelse on October 22, 2019, 11:32:42 AM
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Looks like a new design...180% more fuel efficient...quicker to plane and higher top end. Its called a 'loop prop'. Boat Test did a decent side by side comparison video:
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That looks like a $2500 prop...
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Has this company or anyone actually built this prop or even a prototype and run it in water? All I see are a few computer renderings and no actual pictures of a propeller on a boat or even on a tabletop.
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Ya .. Would guess price might be a issue .. New Laser II's are $600 ..
That prop would cost more the my boat !
Be cool if it really works !
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Has this company or anyone actually built this prop or even a prototype and run it in water? All I see are a few computer renderings and no actual pictures of a propeller on a boat or even on a tabletop.
Did you watch the video where they actually put it on the boat and did real world testing?
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Found that last night. Looks like all 3 props were not suited for the engine-boat combination particularly that the engine runs into the rev limiter. That alone throws off any truth about top end performance.
Then it looks like they selected a boat engine combination that is a pig to get on plane. There are much better conventional props available for under powered barges than the two they selected.
If this test actually took 5-7 days to perform I question how consistent the weather was and why only one hull-motor combination was run.
For most of us with our Glastrons that simply levitate onto plane I see no value to this prop. For others with barges like that Bayliner, simply drive it though its inefficient range where it resists getting on plane. To me the fuel efficiency at idle speed is meaningless. So little fuel is consumed at that speed it really does not matter.
Now lets say it truly is more efficient at idle, friends of mine that troll, they want to run between 1½ to 2½mph. Will that prop allow that? During their testing, did they alter the idle speed settings as some modern engines allow from the helm?
Just some thoughts, this tech might have millions worth of effect on ocean going vessels, then again maybe not. And maybe the watered loaded wake boats might find this the bee's knees.
For me with my CVX that levitates onto plane by 2200 revs, no interest. I doubt my Superboat would find need for it either.
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Really have not thought about how the design could improve the speed, but it must be that it takes some of the wake created by the lower portion of the prop and directs it backwards as it hits the upper portion of the prop blade. Similar to a boat hull that turns downward on the side, deflecting the water down, causing boat lift.
Then to repair the prop after it hits something would be to put back the whole configuration and shape of the loop, not just the lower part of the prop.
We might be at the point where it is a good idea, but too expensive.
The two speed prop, shifting gears at a certain point is a good idea also.
Why not a continuous variable pitch prop, giving the most ideal pitch under any load and at any speed?
I can only imagine the cost of training a propeller shop man and the cost of the prop blocks.
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That prop would go back to the manufacturer for most repairs.
Their video of the two props would have been quite different had they been under heavy load rather then free running in a test tank.
Either 3 blade would have been a swarm of turbulence as it was cavitating trying to lift a heavy boat.
Clearly this somewhat new prop controls the flow separation much better under load.
As I think back in time I have seen this style of prop decades ago, never made it then. Probably now with CFD it can be optimized to work.
I will add a remark for large vessels, they are pretty damn well optimized at running speed. This prop might get a large ship moving better but like our small boats, a large vessel does not spend much time accelerating or running below their efficient speed.
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You can see the part number on prop number 1 …
Michigan Wheel Apollo 14-3/8" x 15 RH 993042
Can't see any numbers on prop number 2 ..
From there FB page .. Oct. 12th 2019
"Sharrow Engineering .. We will announce release dates and pricing at the International Miami Boat Show in 2020."
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The real world test results are pretty clear...sure it'll cost more. All new technologies are...R&D costs have to be recouped.
If your argument against it is the cost of repairs, then you should be using a composite prop where replacement blades are $20 and you only lose 1 mph on the top end and a repair is a simple as sliding a new blade into the hub.
For someone who's boat does almost 100% water sports duty, I'm interested, but I expect this to be pricey. I am curious how durable it is for sure.
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Cost for a 22P Laser II Lab finish prop is over $1000 ..
The Sharrow Engineering prop would have to be more .. Maybe ..
Check out some of the other props .. $5000 plus !
https://bblades.com/
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Looks interesting, but as is the case with emerging technologies, it will take some time as people adopt it, results are reported, and cost to produce is lowered by higher production. I guess one fear I would have is the single source vendor and repair. Thanks for sharing.
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What is misleading in the comparison of the speed at various RPM's of the three props is that the loop prop is faster than the others at all RPM's, but that could be because it has a higher pitch or because of its design, the water slippage is less.
But what is the WOT of each of the props? Maybe the non loop props can achieve a much higher RPM and go faster than the loop prop which may be at WOT at 5,800 RPM. Maybe the prop pitch chosen for the non loop props is too low and a pitch higher would result in better results. I would rather trust the prop testing in the hands of independent testers, not the manufacturer, as they can manipulate the results in their favor by selecting less than the best prop for the others.
What market are they going after? Racing, high performance, utility, tec.
After they are in production, it would be interesting to read the results of a head to head comparison by independent testers of one of the loop props against the best stainless steel props produced by Honda, Yamaha, Evinrude, Mercury on the same boat, where each prop manufacturer is free to select their best prop for the real life water test.
Presently, the Raker 22" pitch and SRX 23" pitch are the fastest for my Glastron/Carlson CVX-16. Should I expect a loop prop to go faster? I have my doubts.
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Sharrow is currently using 5-axis cutters to mill away everything that does not look like the propeller out of a large block of aluminum to make prototypes and suggests that may eventually be the mode of manufacture.
Mach prop company (Out of business) welded their blades onto the hub, claiming the advantage was quicker time from design to production.
But Sharrow might consider doing the same thing. Now they use a solid block of aluminum to machine the prop, and to do the same with a solid block of stainless steel is out of the question.
Much easier to weld the loops onto the hub if they can withstand the shock of hitting objects and the strain of high speed forces on the blades pushing water backwards.
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The real world test results are pretty clear...sure it'll cost more. All new technologies are...R&D costs have to be recouped.
If your argument against it is the cost of repairs, then you should be using a composite prop where replacement blades are $20 and you only lose 1 mph on the top end and a repair is a simple as sliding a new blade into the hub.
For someone who's boat does almost 100% water sports duty, I'm interested, but I expect this to be pricey. I am curious how durable it is for sure.
Well said. I'd love to try out as well.
I am sure the 5-axis machined version won't be for production manufacturing. Easy way to make a prototype propeller without investing in tooling.
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This is a tread on the Hull Truth discussing the Sharrow prop. Interesting points to consider.
https://www.thehulltruth.com/boating-forum/1041543-sharrow-prop-testing-results-3.html