80100 Duct for Safety

As I said Jezza, the graph wuld have to be correct. Nothing else had to be “accurate”.

My original post was to Felix and you included yourself in the discussion which I am fine with but you are overlooking two major points:

  1. In canada we CANNOT have an open propeller and his post resonated for that reason…
  2. Safety with 2-4 hp motor has to be the SPORTS number one concern

While I admire your ingenuity and everyone else’s on the forum, water in a control box that turns one of these prototypes into a blender with a propeller set loose among swimmers will create lots of fresh new laws for the sport…NOT A GOOD OUTCOME

THe us military uses them so for them it is the best for a composite of reasons

low speed is precisely what we are interested in compared to speed boats…that was my piont exactly…thank you for making it for me

again thank you showing me where the disconect is…

By reducing propeller blade tip losses, the ducted fan is more efficient in producing thrust than a conventional propeller of similar diameter, especially at low speed and high static thrust level (airships, hovercraft). … Ducted fans offer enhanced safety on the ground.

fluid dynamics is fluid dynamics. i Know at high speed it is the opposite but i dont consider 20 km/h high spped…

The additional shrouding adds drag, however, and Kort nozzles lose their advantage over propellers at about ten knots (18.5 km/h). (LUCKY GUESS BUT OUT BY 1.5 KM?HOUR not bad for a retired guy :stuck_out_tongue:

I NEVER ONCE SAID HIGH SPPEDD>>>we are interested in more than a 25 minute ride

and lastly, a durajet configuration with the much larger impeller at half the speed of a normal jet ski because I dont believe they use gear reduction and I doubt durajets pull out the lower end gears and replace them for 1:1 gearing…so I strongly suspect my application of a durajet design will comply with the canadian ana american laws and once a few ppl with your design philosophty donate parts of their bodies to science, it will be a universal almost darwinian type of law because honestly open propellers for foiling seems like the ultimate high risk design compromise…but I digress…

so a much larger impeller than a jetski, at a slower RPM will make this far more efficient than the super tiny super high speed jet drives like the lyft or efoil…would an open torqueedo ultra high efficiency propeller be better yes of course…put that on your boat NOT UR EFOIL!!! unless you like meeting nurses at the ER…

anyway Jezza you do you, my goal is the sport be safer

If you think 10% efficiency is worth people being maimed then I cannot convince you something LIKE the durajet is an option and would not require royalties as it is experied IP

And if you want to as efficient as possible for the last (extra) 5 km;hour t at the cost of people being maimed keep up the good work!

Where has the idea that you can’t use a prop come from? Others are using both lift and FR systems in Canada. There are plenty of boats in Canada with open props as well. I’d love to see the regulations that specifically prohibit the use of a prop on a pleasurecraft in Canada.

*EDIT. I see that the regulations would be similar to those required by kayaks with tolling motors (open prop). Therefore I imagine all you need is to carry your Pleasure craft operator card.

it applies to powered surfboards and foils

It is coast guard mandated.

our government wont stop you from doing it . They will just fine you if or when they catch you.

THe exact same thing happened to chinese made dirtbikes, pocket bikes and s on

All the vendors knew there was no legal place or way to use them but sold them anyway took the money and disappeared

The Kort nozzle is MORE efficient at the speeds used MOST of the time…

For the higher speeds, more power is needed and I think we need two options:

  1. durajet clone (proven to work, proven to be marginally more or less efficient if they really did put hte wrong propeller on the boat deliberatedly I dont disbelieve you but it would answer my own confusion

  2. a very low speed ultra high efficiency torqueedo prop with a rounded non cutting edge…less efficiency but a damn sight safer

I think overall turbines in a battery powered device are idiotic BUT the above solution is far safer than people putting stainless steel EVEN THINNER but YAY more efficient convential propellers

anyway I am a retired windsurfer and Jezza if you want to donate parts of your body or run that risk for an extra 20 minutes of run time GO AHEAD but I will no longer condone it when soeone says “oh by the way my PARENTS” think i need a shroud…for a piece of metal that can cut off a finger, wrist or ankle… not how I roll

we all became role models from someone’s child that day and I need people saying ya we can fix this not “ya takes your chances and ya pays the price”

not responsible to the sport, to society or to common sense

Lastly I notice the technical side of the arguments you have totally ignored as I would if they completely proved I was wrong but wanted to be right at all costs even if those costs were someone’s kid being maimed for life

so to recap:

  1. wrong anyway
  2. willing to encourage someone to get maimed for a stupid reason

I let this play out partly to make a point partly to test a pet theory

anyway…i will no longer be replying as this has become utterly pointless and my ultimate design was to use a very low speed torqueedo propeller with blunted leading edges and a durajet for mass production with some complicated lock out features,…again IP so not disclosing here and I have patents all over the workd but i was an employee so no royalties

the foil market is too small but the IP applies to more consumer oriented products but not my area of expertise

I was going to help the vefoil startup but for reasons I cannot get into I opted out

IMHO myself included, we have become to complacent about open propellers by virtue of it being the norm here…

one short circuit, stuck remote, or bad luck and someone is getting hurt real bad

You have to take prop guard off on the fliteboard to reach decent speed. That’s a fact tested in water, seems to be the same for FR

Open propeller is dangerous yes , but seriously there are a lot more things dangerous on efoil , I use a propeller duct this year ( less efficient for sure ) and I think last year I hit every parts on my efoil when falling , catch fire … but not the propeller ! Which seems pretty hard to hit finally

1 Like

Just wanted to say that @Mat has a rounded leading edge version of your prop. This is the intermediate safety step before scimitar-like winglet blades which bent and thinned down could avoid vortices and cuts at the same time.

The ultimate prop for Christmas 2019: :upside_down_face::wink:
1- harmless propeller with round dulled winglets
2- 5USD but rigid though because casted from recycled beer/soda cans in sand then polished to save long CNC hours. Credit: @svtlakovas

1 Like

Im totally impressed which discussion started here but guys calm down we are here for a solution and I think I found something very very simple I will show you my idea tomorrow and I will be fooling tomorrow as my batteries arrive also tomorrow so which me luck and if anyone can help me out while building that battery that would be awesome :blush:.
Just dm me.

Thanks guys

1 Like

My duct

Works well :smile:

1 Like

Nice ! Did you notice a lot of extra drag ?

Haven’t tasted it yet

Great idea having the mount on the shaft. Interested to see how it performs. I had the same prop and it was a total pig, killed my battery in minutes and pulled so many amps I could fry an egg on it. Good luck, standing by for the good news.

I have 3 or 4 of those alu props from china, 5 and 8 pitch 7 1/4 and 7 1/2 diameter. Are those so bad ? I have no reference with other props and I am about to foil for the first time ever. What would you suggest ? c80100 130kv at 14s

If you have to choose one of yours, go for the smaller pitch and smaller diameter.
If you can print/finish it: that one from @foiledagain slightly modified: https://a360.co/2PgkxiY
It performed much better than my solas 7-1/4 x 6. i’m using a 80kv with 12s though…

1 Like

Hi Felix :slight_smile:

That is me calm. I design equipment for use in explosive environments, and one electrical fault and people burn to death.

Having said that donating a toe to science is no less noble.

What worries me is the risk of water entering and causing an unpredictable short, combine that with the likelyhood of the rider being IN THE WATER with their feet near the prop at the SAME TIME

A guy in England had a youtbue video demonstrating that and I believe it had rounded leading edges…they appeared rubberized like how they do toothbrush handles with hard plastic and a moulded in leading edge for us, for the toothbrush a section for superior grip or brushing the tongue

3D printers can do this now :slight_smile:

To be perfectly honest I think (MYSELF INCLUDED) are so damn accustomed to seeing these open props with SO FAR no griveious bodilyharm we all stopped thinking they should only be A TEMPORARY solution

SO Felix, a large torqueedo prop at 1200 RPM, I TRIED THIS AT HOME WITH A HANDDRILL and it just PUSHES my hand away

I live in freaking Canada so we cannot get anything like what you guys buy here…well we can but dam it is so so expensive

I am in discussions with the durajet guy or I was and he was very helpful

I need to buy a single unit then downsize it and three d print a smaller version

I think but am not sure if he uses a completely conventional just very low RPM impeller

**I think for example a dead mans mechanical lock out that PHYSICALLY KEEPS the battery disconnected until the rider is ABOVE THE DAMN WATER and disconnects if the rider falls all is patentable but as of now I am the official inventor inspired by you so thank you as is the oversize propeller My company is Made2Order Safety/Security Solutions and we normally work on royalties but I would make this public domain if it means no one gets hurt in our nascent sport **

I took an arduous road to make the point and my idea or invention is not obvious to someone skilled in the trade because when I suggested it i got all the reasons why it was stupid this actually helps to secure a patent :slight_smile:

I have prototyped this two ways, one using mate while wet desing connectors (not a fan to be honest) and the other a reed relay but mechanical to me is the way to go…so imagine the connection all cordless drills use but instead of connecting the batteries and motor it completes a circuit…I have one I ll take a pic if it not totally obvious?

Felix it took real guts to say I would prefer not to lose a toe, or finger any ideas guys…

it was irresponsible to say “you ll be good , my own kids do it all the time” that is like saying i drive drunk all the time and SO FAR SO GOOD :stuck_out_tongue:

I had tone but I was never angry just very frustrated that anyonew ould even think of seriously compromising safety, the sport and our image for a 5-30% boost in run time if something like an even larger oversize prop will completly eliminate anything but BRUISES, not exactly immune to bruizing in this sport…

P Kay

Is this some type of joke? Patentable? This solution has existed here for just about as long as the forum has been around! Magnetic kill switches have been used by a couple of guys already.

The durajet is just a ducted fan running under the water. There really is no complexity involved in building one. Here is the impeller https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcRTYPH7thh_wR7VqZy22Mz_PliTtjVS04D_kjjIshyRexYlcPGU
If you google around you can find a complete teardown of the unit.


Looks great but I destroyed my spot welder :smile::neutral_face:
First step back :face_with_raised_eyebrow: but I think that’s normal

Thanks guys


I second you on safety but what does “oversize” really mean ?
The flattering specifications come along with oversized prop:
From Torqueedo catalog: Motor power, prop diameter
2 blades, 1 HP, 200mm
2 blades, 1.5 to 3HP, 269 to 292mm
3 blades > 3HP, from 300mm

Looking forward to see this Torqueedo 300mm prop reduced to 170-180mm. You will note that the hub (boss ?) is flush with the motor for best efficiency. This model, if it was designed with accentuated winglets, should not be that dangerous since repelling approaching objects.

1 Like

I will try to print it with www.3dhubs.com
If we want this prop CNC in aluminium, we can get it for 73 euro per piece if we order 10 pcs.

https://www.3dhubs.com/manufacture/ You can get an online quote.

And you have missed the point yet again


SoEFoil, thank you so much for understanding I want what is good for the sport and safety.

It is sincerely appreciated.

Thank you again,
P Kay