A major improvement in efficiency? the new 'Sharrow propellor'

[BruceK]

I think that you have to give some credibility to Captain Steve. I’ve been following his video and written reviews for years and if he says it’s good then it probably is good. Let’s face it, he is on a lot more boats than we are (and he hasn’t gone all Clarkson, if it’s not a Ferrari then it’s a useless piece of sh1t$)

I'm always suspect of a reviewer that works for a company that gets paid by clients to do the review. That seems to hint at a bias.

 

[MapisM]

So, you don't fly on any Boeing airplanes, I suppose...?

 

[MapisM]

If you ignore the silly comparisons where one was on the plane and the other was not - it does seem real.

+1. The u/w videos showing the different trails are also intriguing.
And I agree with Elessar when he said that a 5 to 10% improvement would already be a big deal.

 

[Bouba]

+1. The u/w videos showing the different trails are also intriguing.
And I agree with Elessar when he said that a 5 to 10% improvement would already be a big deal.

And improved handling. I wonder if that applies to ships?
They should have pulled a few skiers as well

 

[BruceK]

So, you don't fly on any Boeing airplanes, I suppose...?

I avoid aeroplanes wherever I can. I'm not afraid of flying as such, Im terrified of heights. Just watching the telly of space flights in the ISS looking back down on earth give me such a horrid sense of vertigo I have to take a nap to sleep it off

EDIT. Never used to be this way. Jumping out of a perfectly good plane on a static line to impress a bird when I was in my mid 20's did it. :disgust:

 

[longjohnsilver]

Googling for the correct name would have been appropriate, too!

Bloody spellchecker:encouragement:

 

[kashurst]

If you ignore the silly comparisons where one was on the plane and the other was not - it does seem real.

yes, either side of the "hump" the sharrow prop was markedly better. Be interesting to see the effect on a shaft drive planing boat. The hyperbole around the 116% improvement etc was just silly.

 

[TheOrs]

If you ignore the silly comparisons where one was on the plane and the other was not - it does seem real.

+1. The u/w videos showing the different trails are also intriguing.
And I agree with Elessar when he said that a 5 to 10% improvement would already be a big deal.

I agree. It would have been interesting for them to have done some timed acceleration tests - Hole-shot to planing & hole-shot to 45mph. Or maybe even pull out a fat guy on a mono ski!

If the Sharrow was also quicker/better for that then it really would be worth a lot of money.

(Putting my money on QBhoy for the first forumite to buy & try one )

 

[peterjaw]

From Sharrow's web site, the new props are available in Commercial/Military vessels.

http://www.sharrowengineering.com/#sales-section

If there is any real-world story I think Sharrow would love to put it on their web site. Unfortunately, not yet. But that doesn't mean No story.

I also curious about how much it will be when it comes to retail price. I believe the prop that Steve tested was just a prototype and they
don't know the cost for mass-production yet.

The under water video is really impressed.

 

[Bouba]

I would imagine that the manufacture of these blades would be very expensive. Also, there are so many different sizes and hubs that it could take a long time before they all reach the market.
If Sharrow is reading (and they should be) I would suggest that, if possible, could they first make them out of alloy. This would be cheaper and easier for boaters to try before the expensive stainless ones. Just a thought

 

[MapisM]

In the test they said that the prop was indeed made of alloy, even if compared with traditional stainless steel props.
I can see why you didn't realize that, though: based on the images alone, it looked like a stainless prop, just un-polished.

 

[Bouba]

In the test they said that the prop was indeed made of alloy, even if compared with traditional stainless steel props.
I can see why you didn't realize that, though: based on the images alone, it looked like a stainless prop, just un-polished.

No, I completely missed that !
I guess that with the comparison props all being ss I just assumed.

 

[Deleted User YDKXO]

That was a very impressive video. Personally, I would sacrifice speed and fuel efficiency for slow speed maneuvering (especially on a single engine boat).

J have you got both a bow and sternthruster on your boat?

 

[Montemar]

The video pointed out the bubble flow from the tips of the blades.
Many passenger jets have a small vertical section at the end of the wing to stop air flowing off the end causing loss of lift.
Could a lip or something be put on the end of the blade to reduce this apparently efficiency reducing effect?

 

[BruceK]

The video pointed out the bubble flow from the tips of the blades.
Many passenger jets have a small vertical section at the end of the wing to stop air flowing off the end causing loss of lift.
Could a lip or something be put on the end of the blade to reduce this apparently efficiency reducing effect?

If we were talking hydrofoils, sure, most have them anyway. But your analogy would be more plausible if you saw them on prop driven aircraft, on the prop. Whereas many prop types do have an elongation at the tip and a good example would be helicopter blades, their primary reason is not to stop tip vortices as prop tip winglets would operate in a region of high dynamic pressure and generate more friction drag without contributing to the prop's efficiency. And so the same is true of a boat propeller.

EDIT. Interestingly, in certain racing / speed RC model aircraft especially handline models a single larger blade with a counterbalance instead of second blade is preferred. And on some light aircraft to increase thrust As the single blade can be larger and more efficient and suffer less overall drag boosting performance significantly. However I suspect the medium of water would introduce serious vibration, instability and stresses.

 

[QBhoy]

Being overly obsessed with props...
I have a real issue with this test.
The wot figures were taken on the rpm limiter and at a speed a fair bit lower than what would be expected of such a set up....all telling me that the 15” props were vastly under propped. Only reason for this would be to give the featured prop an advantage to its better characteristics.
Would love to see them do it with the proper pitched props. No way that would stand up to a 19” smaller diameter prop like an enertia. Not a chance.

 

[MrB]

If we were talking hydrofoils, sure, most have them anyway. But your analogy would be more plausible if you saw them on prop driven aircraft, on the prop. Whereas many prop types do have an elongation at the tip and a good example would be helicopter blades, their primary reason is not to stop tip vortices as prop tip winglets would operate in a region of high dynamic pressure and generate more friction drag without contributing to the prop's efficiency. And so the same is true of a boat propeller.

EDIT. Interestingly, in certain racing / speed RC model aircraft especially handline models a single larger blade with a counterbalance instead of second blade is preferred. And on some light aircraft to increase thrust As the single blade can be larger and more efficient and suffer less overall drag boosting performance significantly. However I suspect the medium of water would introduce serious vibration, instability and stresses.
View attachment 81027

No, don't mix boat props and helo/plane props.....two very different things. Plane props can have a small curved type tip aft but that is to do with sound as the prop could be rotating at the speed of sound at it's tips. (cuts it out) Helicopter rotor winglets are the same as an aircraft wing winglet and just increase the volume of air on which the wing can act.(a rotor is just a wing) Extending the the wing would be better but when span is restricted or the maximum wing bending moment is limited, winglets bring a small improvement in efficiency at high lift coefficients.

On propellers, however, the winglets would run through air which is already affected by the tips of the propeller. No additional air will be involved, so no efficiency increase will be possible. (on a plane)

 

[peterjaw]

I wonder how do engineers in Sharrow make a fair comparison with traditional props?

With traditional props, we know the diameter and pitch; but for the Sharrow props, how do they define their specifications?
How will the Sharrow prop specifications match up the traditional props?

This will be a very complicated game for their engineers to play and they have to have some data for consumers.

 

[QBhoy]

I wonder how do engineers in Sharrow make a fair comparison with traditional props?

With traditional props, we know the diameter and pitch; but for the Sharrow props, how do they define their specifications?
How will the Sharrow prop specifications match up the traditional props?

This will be a very complicated game for their engineers to play and they have to have some data for consumers.

It’s clearly a game they have played to an advantage. Using the wrong pitch props an all ! Very disappointed

 

[Bouba]

If we were talking hydrofoils, sure, most have them anyway. But your analogy would be more plausible if you saw them on prop driven aircraft, on the prop. Whereas many prop types do have an elongation at the tip and a good example would be helicopter blades, their primary reason is not to stop tip vortices as prop tip winglets would operate in a region of high dynamic pressure and generate more friction drag without contributing to the prop's efficiency. And so the same is true of a boat propeller.

EDIT. Interestingly, in certain racing / speed RC model aircraft especially handline models a single larger blade with a counterbalance instead of second blade is preferred. And on some light aircraft to increase thrust As the single blade can be larger and more efficient and suffer less overall drag boosting performance significantly. However I suspect the medium of water would introduce serious vibration, instability and stresses.
View attachment 81027

I have never seen a single blade propeller before! The whole history of boat prop development was to reduce the number of blades (didn’t Robert Fulton (or someone else) hit the ground with his newly invented prop, lost some blades and realized he was going faster?).
Where you see this now is on small electric outboards, where there are only two blades. So a one bladed prop should be best!