Still learning new things in fusion 360 regularly...

[TorontoBuilder]

Beats me. I've not seen this before. If the prop increases lift or thrust with less input torque required, (ie more efficient) it should reduce torque on the hull for the same performance. However, most applications seek to increase performance to take advantage of the improved efficiency so I wouldn't really expect any improvement.

Are those things available for conventional outboard engines?

Yes, they are now for sale for larger outboards, and some inboard engines.

caveat being they cost an arm, leg and both testicles... or in monetary terms $4999 USD each... hate to have twin outboards.

okay yes there should be less torque, but I want to eliminate it almost entirely since turning a canoe with a rear mounted motor presents a significant capsize danger due to the torque, the hull shape and the pivot point

 

[140mower]

Yes, they are now for sale for larger outboards, and some inboard engines.

caveat being they cost an arm, leg and both testicles... or in monetary terms $4999 USD each... hate to have twin outboards.

okay yes there should be less torque, but I want to eliminate it almost entirely since turning a canoe with a rear mounted motor presents a significant capsize danger due to the torque, the hull shape and the pivot point

Unless I am missing something, but if torque is that big of a concern, you have a load distribution issue..... I grew up with a rear engine mounted canoe and put hundreds of hours on several engine combos. Even paddling around, I had a pile of rocks on a piece of plywood at the bow. The faster you wanted to go the bigger the pile....

 

[PeterT]

I'll have to read up on that. I know that a simple ring shroud can as much as double the thrust of a propeller for a given input power by mitigating tip losses (subject to a bunch of variables, not all within control). Its impractical for many airborne applications but I would think reasonable for many boat/fluid applications. And you get a bit of protection out of the deal. Probably many tradeoffs on the opposite side of scale.

Ducted propeller - Wikipedia

en.wikipedia.org

shrouded propeller vs nonshrouded opeller

Dear all, need help with regards to the difference between using a shrouded propeller and a nonshrouded propeller (of similar blade pitch and diameter...

www.boatdesign.net

Whatever happened to 'tubercle' propellers? They were all the hot rage for a while.

 

[TorontoBuilder]

I'll have to read up on that. I know that a simple ring shroud can as much as double the thrust of a propeller for a given input power by mitigating tip losses (subject to a bunch of variables, not all within control). Its impractical for many airborne applications but I would think reasonable for many boat/fluid applications. And you get a bit of protection out of the deal. Probably many tradeoffs on the opposite side of scale.

Ducted propeller - Wikipedia

en.wikipedia.org

shrouded propeller vs nonshrouded opeller

Dear all, need help with regards to the difference between using a shrouded propeller and a nonshrouded propeller (of similar blade pitch and diameter...

www.boatdesign.net

Whatever happened to 'tubercle' propellers? They were all the hot rage for a while.
View attachment 30093

ah yeah, the biomimicry ones... not enough gain for the more difficult and expensive production

and the introduction of rim driven propellers gained more interest. They have the same long leverage advantage as axial flux motors because the longer radius of the magnet arrays driving them

 

[PeterT]

I didn't run them myself but my buddies told me at a WC event, the tubercle's had a distinctly different sound (quieter) and they didn't acoustically bark in certain flight conditions where normal blades stalled. Supposedly they drew slightly less power for equivalent thrust which was the main objective. Whether true is hard to say. This was back ~2010 & pretty much last I saw of it. But what is remarkable is the gap time between CAD model 'crazy idea' & finished carbon prop is mere days, just in the hands of dedicated hobbyists. (CNC milled aluminum molds). But those loop blades you show would be very complex molds.

 

[TorontoBuilder]

I didn't run them myself but my buddies told me at a WC event, the tubercle's had a distinctly different sound (quieter) and they didn't acoustically bark in certain flight conditions where normal blades stalled. Supposedly they drew slightly less power for equivalent thrust which was the main objective. Whether true is hard to say. This was back ~2010 & pretty much last I saw of it. But what is remarkable is the gap time between CAD model 'crazy idea' & finished carbon prop is mere days, just in the hands of dedicated hobbyists. (CNC milled aluminum molds). But those loop blades you show would be very complex molds.

the sharrow props were machined from a large stainless steel billet on a 5 axis cnc mill in Michigan. Now they are supposedly using a lost wax investment casting process

 

[Susquatch]

Very cool but waaaaay over priced for my needs.

A bigger outboard motor would cost much less than the difference in the propeller cost and gives a much bigger performance boost in the bargain.

I confess that I am totally intrigued by the concept though.

 

[PeterT]

I'm still concerned by potential prop strikes to endangered aquatic species. I would rather invest in a surface mount propulsion, LOL.

 

[TorontoBuilder]

I'm still concerned by potential prop strikes to endangered aquatic species. I would rather invest in a surface mount propulsion, LOL.

Yeah that's cool but I bet it is a real bitch on a long portage.

I really just want a safe and light assist to be able to access some places I haven't been in a couple of decades. I have serious arthritis in my shoulders which means some long lake and upstream stretches are now a huge burden

 

[TorontoBuilder]

There is a fellow offering design services whom I'd ask to model something for me but it would violate US and CDN intellectual property laws. From what I understand I can copy the design for personal non-commercial use but others can't provide commercial services that relate to manufacturing designs covered by IP rights.

To model what I want requires lofting skills that are currently beyond me.

I don't know if anyone else has seen the marine propellers developed Sharrow marine, but they are revolutionary, and me being me, I just want to manufacture some to use on model boats and an electric drive for a kayak.

Now MIT's Lincoln lab has created and patented a similar type of propeller for aviation use, specifically in their case drones. They call them torroid props. There is a huge reduction in noise due to minimises tip vortices. Also greater efficiency by about 20% without any design work to optimize efficiency being done yet.

These new props are a wet dream for those who use micro drones for urban peeping. I think I can model these far simpler props but not the marine ones that I have been looking at the past few years

I had some time where I felt well enough to figure out how to model a toroidal propeller. I had done something similar a few years back but forgot the steps needed to create 3D lines that curves on multiple planes. I had to figure out how make a curved surface from one a curve along one plane in order to project a curve on a plane 90 degrees to the first onto the curved plane in order to create rails to constrain the loft of the propeller blades.

The image below illustrates the two complex curves that comprise the upper rails for the two leading edges of the propeller on one side of the prop. The flat plain in light blue has the two 2D curves that form the rails for the trailing edges of the props.

The image below is 13 different sketches, showing the same elements as above and the individual profile sketches for the propeller on their 11 different planes from a more tilted angle for better clarity of the base sketch

This and the opposite CW prop will be 3D printed so it has a flat on the bottom to attain enough adhesion to the bed. I'll test against a standard 5040 propeller to see if it has better thrust and sound characteristics before doing small production run for further testing.

It will be printed at a very fine setting, then receive post printing heat treatment, sanding and primer and paint coating. Then I'll make a multipart silicone mould in order to make small production runs with different plastics and hard two part urethanes.

I added carbon fiber for a few renderings but 5 inch props are too small for me to make from CF

 

[Susquatch]

I had some time where I felt well enough to figure out how to model a toroidal propeller.

That's AMAZING!

It makes me wonder if Fusion include a hydraulics module where you could test the propeller in a virtual fluid environment?

 

[TorontoBuilder]

That's AMAZING!

It makes me wonder if Fusion include a hydraulics module where you could test the propeller in a virtual fluid environment?

I am pretty sure that they dont in the basic fusion....

I am making a better test rig with 3 load cells to test both thrust and torque. No need for hydraulics module in software.

I'm working on contra-rotating motor and props to use in a model paramotor where eliminating torque is very beneficial

 

[TorontoBuilder]

next up the sharrow propeller for model boats.

I'm thinking investment casting in bronze would be cool. SLA print to make silicone mould to make wax models for investment casting...

 

[Susquatch]

I am making a better test rig with 3 load cells to test both thrust and torque. No need for hydraulics module in software.

Well actually, the reason I suggested testing in software is to reduce the need to make prototypes for physical testing. I know some will still be required. But with something so unique you could end up making hundreds of prototypes before you get something you are happy with. If you can test in a model and then validate with a prototype, it might eliminate hundreds of prototype iterations. Of course, if it works the way you want first crack then the simulation is not needed.

I pretty much figured it wouldn't be standard. But maybe you can buy it for just a few months......

 

[PeterT]

Nice CAD work. That is a pretty mind bending shape.

Molds looks very challenging, likely varying parting plane surfaces & probably sub structure elements. I've seen some 3DP promotional videos where guys are direct printing casting ready wax material, thus leaving only the trivial task of investment & casting haha (that's a joke, I don't even qualify as bystander status). But maybe you can go straight from CAD file to 3DP nickel or bronze, no middle man. I'm guessing their shrinkage & other dimensional issues might be a factor to contend with, but I mean fluid dynamics is complex sh*t. The chances of getting the first iteration 100% right is probably zero even if it were cast perfect. Attached an old Tom Lipton video where he outsourced the handle & did some post finishing. Check the vid but I seem to recall ~75 USD but those prices are probably outdated & not sure if name drop discount although that's not his style. Anyways, easy to upload a file & get a quote. I would think since that time even more services avilable & better quality.

 

[Matt-Aburg]

Nice CAD work. That is a pretty mind bending shape.

Molds looks very challenging, likely varying parting plane surfaces & probably sub structure elements. I've seen some 3DP promotional videos where guys are direct printing casting ready wax material, thus leaving only the trivial task of investment & casting haha (that's a joke, I don't even qualify as bystander status). But maybe you can go straight from CAD file to 3DP nickel or bronze, no middle man. I'm guessing their shrinkage & other dimensional issues might be a factor to contend with, but I mean fluid dynamics is complex sh*t. The chances of getting the first iteration 100% right is probably zero even if it were cast perfect. Attached an old Tom Lipton video where he outsourced the handle & did some post finishing. Check the vid but I seem to recall ~75 USD but those prices are probably outdated & not sure if name drop discount although that's not his style. Anyways, easy to upload a file & get a quote. I would think since that time even more services avilable & better quality.

I agree, molding fans are a @#$%^&**. The transition MUST not be undercut. Make sure you can get at least 5-7 degrees between upper and lower at the hub.. @TorontoBuilder needs to draw this DFMA.. or it cannot be mass produced.

 

[PeterT]

Now what I really want to know is does the new style propeller reduce the torque on the hull? I don't think it would....

I would think this prop would have similar reaction forces as a regular prop, because its still making thrust along the shaft axis & fixed rotation direction. Which probably means induced yaw & some P-effect.
For more axial thrust you want a contra prop setup like my buddy Chad. Well, it was in vogue until it wasn't LOL. Personally I think you should go variable pitch. Fixed blades seem so... limiting haha. That might have some direct benefits to your power efficiency.

 

[TorontoBuilder]

I would think this prop would have similar reaction forces as a regular prop, because its still making thrust along the shaft axis & fixed rotation direction. Which probably means induced yaw & some P-effect.
For more axial thrust you want a contra prop setup like my buddy Chad. Well, it was in vogue until it wasn't LOL. Personally I think you should go variable pitch. Fixed blades seem so... limiting haha. That might have some direct benefits to your power efficiency.

I don't know how to implement variable pitch on a paramotor...

I do like Chad's model but I want an rpm range of 1700 - 2300 for full scale. I want the lightest possible motor so wont be going gearbox route but rather one shaft running thru the other like my old motor and like the RCTwins use. Much simpler and allows better cooling without the gearbox in the air path.

Eliminating the torque on single motor type planes makes learning to pilot them much easier since no trim settings to deal with minimize torque.

2220 size would be easier to make a mould for to make carbon fiber. It is a size that a cnc router may be able to produce the prop, if you can flip the stock over and reposition it accurately

 

[TorontoBuilder]

I agree, molding fans are a @#$%^&**. The transition MUST not be undercut. Make sure you can get at least 5-7 degrees between upper and lower at the hub.. @TorontoBuilder needs to draw this DFMA.. or it cannot be mass produced.

I've made a few complex mould in the past, especially for casting ceramic slip so I feel fairly confident there. If I had a small cnc mill I'd make a mould with that out of a hard material so i'd have more options when it comes to casting materials

 

[PeterT]

I don't know how to implement variable pitch on a paramotor...

You got me there. I've only seen them from the sidelines. You want to put in 'R' & back into the hangar do you LOL?
This one is for electric outrunner style, 26" prop, maybe scalable?