Toroidal Props. Wow!

[Chotu]

Somebody came up with some new toroidal props. Much more efficient. No tip vortices.

Really cool stuff.

https://newatlas.com/aircraft/toroid...et-propellers/

https://youtu.be/QNCbnntCU2k

[Dave_S]

Yamaha and Sharrow? Worked together to come up with props specifically for each of their outboards with incredible claims.

One worry is how do they perform after a bit of a bump.

I think they are about US$2,500ea

[rslifkin]

At this point, the biggest issues seem to be cost and the limited applications they're available for.

[Chotu]

Originally Posted by rslifkin

At this point, the biggest issues seem to be cost and the limited applications they're available for.

Yeah. Because my props under perform, I was getting ready to buy a set of these when I read the article, then I got to the price. Lol

[Phyrcooler]

I’ve been watching this developer for a while. Multiple documented tests showing improved efficiency. However, all that I’ve seen so far have been high speed SD hulls. I’m curious if they’re seeing similar gains in the 7 - 12 kt displacement range.

As a pilot, I’m also interested to see where this may go. Improvements like this in speed, efficiency, and sound reduction will be a significant boon.

Lastly, the one interesting thing I noted was when they were bragging about the sound reduction with triple 300 outboards - was that it was all “propeller noise”. It may be… but I’m dubious. They are reporting comparisons were made at the same SPEED, not the same RPM. I’m guessing that the motors with standard props were turning hundreds of RPM’s faster to achieve the same speed… and a lot of the sound reduction with the Sharrow prop was motor and exhaust noise reduction at lower RPM’s. So, yes… noise reduction BECAUSE of the props. But not so much PROP NOISE….? But that’s just my guess watching the video. YMMV. Others more wise than I may have different opinions.

[rslifkin]

Originally Posted by Chotu

Yeah. Because my props under perform, I was getting ready to buy a set of these when I read the article, then I got to the price. Lol

Did you ever get the block off plates into the bottom of the outboard wells? If so, how much difference did they make?

[Idaho]

Radically quieter than traditional propellers"

Leaked submarine tech. They always cover a military sub's props with a tarp when its in dry dock. Prevents photo snooping.

[JebLostInSpace]

I read this one today too. I really hope we see some analysis on 6-10kts displacement speeds. Looking at the various charts they show on the Sharrow site, it does look like the 3k RPM range is where a lot of the big efficiency gains are. Since that's about where I run my engine to cruise, that seems like a good sign. Hopefully those gains don't all disappear when you take away effects of planing.

My prop drastically underperforms, so I'd think seriously about paying for an expensive one if it's really a lot more efficient.

A regular fixed blade on my boat was about $700 when I replaced it a couple years ago. (I increased to 3 blades and increased pitch, but my new one STILL underperforms. But that's another story)

Folding props look like they're in the $1500-2500 range for my boat.

Best guess looking at the Sharrow information is about $2500 for a theoretical model that would be appropriately sized for my boat. That would be low enough for me to think hard about it. If they got it down to $1500 I'd do it for sure.

[Chotu]

Sitting here a little late in the bunk this morning trying to stay warm because it’s chilly, I am hearing everybody going out for their Saturday run on the planing power boats.

You can definitely hear the tip vortices in the engine noise.

If you are in your boat, the first sound you hear is the tip vortices. It’s that sound you hear of boat propellers when you are underwater. Somewhat high-pitched. Then as you start to hear the motor, you can hear the combination of that sound with the sound of a motor running. You can hear it right through your hull. It’s a perfect place to listen.

I never really thought about separating those two sounds out before. But if you think about it you can. And then you can hear the difference between tip vortices and the motor itself.

Then if you think about what was in those videos, it makes a lot of sense. Nothing is doctored or altered. That’s about the difference in sound.

[ozolli]

My first thought was : Won't cope well with weed.

[rslifkin]

Originally Posted by Chotu

Sitting here a little late in the bunk this morning trying to stay warm because it’s chilly, I am hearing everybody going out for their Saturday run on the planing power boats.

You can definitely hear the tip vortices in the engine noise.

If you are in your boat, the first sound you hear is the tip vortices. It’s that sound you hear of boat propellers when you are underwater. Somewhat high-pitched. Then as you start to hear the motor, you can hear the combination of that sound with the sound of a motor running. You can hear it right through your hull. It’s a perfect place to listen.

I never really thought about separating those two sounds out before. But if you think about it you can. And then you can hear the difference between tip vortices and the motor itself.

Then if you think about what was in those videos, it makes a lot of sense. Nothing is doctored or altered. That’s about the difference in sound.

Tip vortices are definitely noticeable. On my boat the props are sized to pretty much the minimum recommended tip to hull clearance for a planing boat. And because of that, it's not quite as smooth on plane as some boats I've encountered (especially with outboards). In the aft part of the boat you can definitely feel and hear the tip vortices hitting the underside of the hull. It's not enough to blast the paint off the hull in that spot, but the paint does wear slightly faster above the props than in the surrounding area.

[Phyrcooler]

Originally Posted by Chotu

Then if you think about what was in those videos, it makes a lot of sense. Nothing is doctored or altered. That’s about the difference in sound.

No doubt there is some noise from the props. I guess I should have been more clear. I wasn’t insinuating that the videos were altered. But I’m betting the sound difference, while existing, is much less noticeable if both videos were taken with the engines running at the same RPM. There’s no way you can reduce output hundreds of RPM’s on triple outboards and not have a noticeable reduction in engine, transmission, and exhaust sounds. Attributing it all to prop tip noise seems a bit disingenuous no matter how much I like their product.

[rslifkin]

Originally Posted by Phyrcooler

No doubt there is some noise from the props. I guess I should have been more clear. I wasn’t insinuating that the videos were altered. But I’m betting the sound difference, while existing, is much less noticeable if both videos were taken with the engines running at the same RPM. There’s no way you can reduce output hundreds of RPM’s on triple outboards and not have a noticeable reduction in engine, transmission, and exhaust sounds. Attributing it all to prop tip noise seems a bit disingenuous no matter how much I like their product.

I didn't watch the whole video, but assuming some performance (speed vs rpm) differences between the props, were they possibly comparing noise, etc. at the same boat speed, rather than the same engine RPM?

[Cheechako]

"My boat's paid off, but I'll be decades paying off the mortgage on my torroidal props!"

[Corvidae]

Waiting to see how they perform on a 10 to 25hp outboard myself. Honestly I doubt there's enough advantage to really help a displacement hull. The rpm ranges might look great in the charts, but those were made on 300hp outboards running at higher water speeds. Drop those same props behind a dozen tons of displacement hull, then show me the benefits.