Author Topic: new prop design for efoiling?  (Read 3976 times)

jondrums

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new prop design for efoiling?
« on: January 30, 2023, 10:36:03 AM »
https://newatlas.com/aircraft/toroidal-quiet-propellers/

@admin fire up your advanced CAD software and see if it can model this...
20% efficiency gain is nothing to scoff at!

tarquin

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Re: new prop design for efoiling?
« Reply #1 on: January 30, 2023, 01:26:19 PM »
I was going to post something about this a couple of weeks ago. But thought you guys had enough on your hands. Obviously not.
 Looking for a new prop for a boat and this thing keeps popping up. They must have spent some money on advertising and how to make their prop come up first in a web search. Pono?
 Like most things this has been tried. If they have got it right it could be amazing.
 You are looking at 5000 dollars instead of 500 for a prop for a large outboard. Most boats with that size outboard have 2 or 3.
 I think now with smaller props for electric powered vessels where efficiency makes a huge difference it may work.
 Now sailing boats with electric engines that charge when the prop is spinning WANT the prop to spin when sailing.
 This "new" idea may be well timed.
 As Pono said in another post they have copyrighted the F out of it.
 

jondrums

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Re: new prop design for efoiling?
« Reply #2 on: January 30, 2023, 01:40:52 PM »
with 3D printing, propellers are going to get much more interesting.  I've seen some metal 3D sintered parts with surface finish better than investment casting and cost is coming down fast - so it'll be in play for boats soon.  For e-foiling we can 3D print props in plastic, who cares how complex the design is and their copyright won't slow us down 

tarquin

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Re: new prop design for efoiling?
« Reply #3 on: January 30, 2023, 02:00:55 PM »
From what I understand the tolerances on this are tight.
 It has been tried and if it works it will be awesome.
 Just 3D printing a smaller version won't work for now.
 What pitch and diameter do you go for!

Admin

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Re: new prop design for efoiling?
« Reply #4 on: January 30, 2023, 03:35:03 PM »
Jon, This is awesome.  Bill had posted this https://www.standupzone.com/forum/index.php/topic,38317.msg439235.html#msg439235 and it is really hard to see what exactly is going on.  They show the profiles in the diagrams but it is hard to see if they are all different.  It looks they are, with cambers and dimensions changing. Are the three blades all unique?  Printing that cleanly would be really difficult.  In any orientation you would need support everywhere.  Maybe one of the other additive technologies?  So cool.
« Last Edit: January 30, 2023, 03:40:46 PM by Admin »

PonoBill

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Re: new prop design for efoiling?
« Reply #5 on: January 30, 2023, 05:39:52 PM »
Yeah, I guess we're the only two people reading the Print to Ride topic. Makes sense, it's not very interesting unless you're doing it.

I looked at the drawings fairly carefully. It appears they show two different props, the lower one is 7.8" and looks likely to have an outboard motor spline, while the one on top looks a lot smaller, has a shear pin drive, and seems to be dimensioned in MM. I think it will be a bitch to draw, but not too hard to print. the ghosted drawing that shows foils in distorted by perspective. The top drawing is a bit more telling since the chord and max thickness are spelled out. The upper (towards the bow of the boat) foil in the example prop has a chord of 16.017 (MM??--it appears so. One more bit of evidence that they were modeling these on small motors, probably electric.) and a thickness of .61. It seems fairly clear this drawing is not in inches. After all, who the fuck uses inches other than 'murricans.  The lower (back) foil is 17.33 chord and .682 thickness. That makes sense to me, probably aimed at giving similar thrust to both blades--one in slower moving, less turbulent water (front) and the other in water moving however much faster slip allows, and more turbulent.

I suspect the easiest way to print this would be SLA, or laser sintered. SLA wouldn't require support (printed top down) and sintering doesn't use support either since the powdered metal supports the metal as it cools.

There's an example of drawing a fan blade on one of the youtoober sites and lots of examples on how to do a propellor in Fusion 360. The examples work for a blade with a simple profile. Managing the reversal of the foil will be an interesting challenge. I should be able to knock this right out in a year or two.

Actually, they patented the shit out of it, which means you can't copy these and sell them without getting sued into a coma. But you can make one for your own use. Neither patent nor copyright prevents that. Patents protect commercial use, even copyright permits "fair use".

I think for eFoils and Faux drives this offers two big benefits. The props will be stronger. Currently my prop prints qualify more as blade launchers than props. Having the blade essentially supported at both ends should help that. And second, if the blade hits you it will be more like a dull melon-baller than a ginsu. I like that. A lot.

« Last Edit: January 30, 2023, 05:58:08 PM by PonoBill »
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

PonoBill

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Re: new prop design for efoiling?
« Reply #6 on: January 30, 2023, 06:04:28 PM »
They must have spent some money on advertising and how to make their prop come up first in a web search. Pono?

They certainly could have. If they are aiming at doing props for tankers and cruise ship to increase efficiency by 20% then people are tossing money at them as fast as they can. A 20% gain in efficiency would mean zillions in savings for people who have zillions.

But they're also getting reviewed by everyone who can spell boat. That would cost them a propeller, and I suspect their cost to have these cast and finished would be somewhere in the $100-400 range. Less if they aren't made in the USA. But they probably are, they're probably doing their best to keep these away from Asian manufacturers, especially since they are making the commercial small boat ones out of Aluminum.
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

PonoBill

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Re: new prop design for efoiling?
« Reply #7 on: January 30, 2023, 10:50:22 PM »
I just realized how to do this sketch. The answer came unbidden while I was looking at a fusion 360 for knuckleheads video. The complexity comes from using an asymmetrical foil for the blade cross-section. That's unnecessary except as a refinement. If we made the foil section symmetrical (most propeller foils are) then the drawing becomes a lot simpler. It could probably be lofted or swept through the entire transition of the blade. Lofting it would still be a nightmare, but I can visualize how it would be done. That's 90 percent of the solution. The second 90 percent is getting the drawing to work, and the last 90 percent is printing it.
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

Admin

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Re: new prop design for efoiling?
« Reply #8 on: January 31, 2023, 01:13:56 AM »
This thing is like an Escher painting.  Great to look at and consider but hard to fully grasp.  Because the blade has done a 180 as it returns which inverts the section, and because it is cambered, and because it is  moving through flow in the same direction. the same blade is developing outward lift in opposite directions (with a lot of variation in the transitions).  The sections look like they are most cambered at the root(s) and then become more symmetrical (maybe symmetrical) at the return.  That would make sense but...  I am guessing that the efficiencies are gained in these details and you could go net negative really quickly with a similar looking rig that doesn't manage all of this very intentionally.  Plus those blades are going to be very thin in places and they are curved so that internal supports won't really work. 

To loft this, even using complex sections, would be easy enough.  That part is exactly the same as our foils.  It is controlled by those two 3D paths which widen and twist around to rejoin the hub.  I would really like to feel this thing to better understand it.
« Last Edit: January 31, 2023, 01:22:23 AM by Admin »

PonoBill

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Re: new prop design for efoiling?
« Reply #9 on: January 31, 2023, 06:14:58 AM »
Even flat-bladed props work, consider your basic window fan, it's AOA that makes them move air--essential for a screw. A symmetrical foil can be very efficient at moving air or water. I'm sure the refinements of foil shape and transitions deliver that stunning efficiency. I"m more interested in strength and melon balling.
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

jondrums

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Re: new prop design for efoiling?
« Reply #10 on: January 31, 2023, 08:56:34 AM »
pono, I'm quite handy with CAD and I know I could loft a copycat.  If you can share diameter and pitch that's been working well or better yet an STL, I might take a crack at generating a file one of these days.  I think I would want to know the root pitch and the tip pitch.  I know there are tons of files on FOIL.zone, but I can never figure out which ones are actually good to start with

PonoBill

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Re: new prop design for efoiling?
« Reply #11 on: January 31, 2023, 10:03:55 PM »
Cool, I'll work on that. I wonder if this thing can be made smaller than a conventional prop.
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

 


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