Electric Hydrofoil/E-Foil

[Jezza]

how/where can I find an "efficient" jet drive?
and how much less efficient are they compared to impellers?

edit:
for an impeller, would it make sense to rewind a motor to have less RPM?

https://www.mhz-watercraft.com/jets/504 ... teil?c=109
or
https://www.mhz-watercraft.com/jets/503 ... teil?c=109

Both will definitely handle 16k rpm and I'd think they would be fine to 20k rpm
A jet is a lot less efficient than prop, but for this application would work fine.
You just need more power because of the inefficiency. I think a 3-4KW jet drive might be able to get you up, but that is just a thumbsuck...

[nanni]

Hi anbat8, have you seen this? http://alienpowersystem.com/shop/brushl ... 0kv-3200w/
or this? http://alienpowersystem.com/shop/brushl ... 0kv-6000w/

No, did you tried one of these? Is it reliable?

Thanks

Bruno is now closed until July 19, and he told me he ordered the 6374 60kv. After this date I will buy it .

[parabellum]

Hi anbat8, have you seen this? http://alienpowersystem.com/shop/brushl ... 0kv-3200w/
or this? http://alienpowersystem.com/shop/brushl ... 0kv-6000w/

No, did you tried one of these? Is it reliable?

Thanks

Bruno is now closed until July 19, and he told me he ordered the 6374 60kv. After this date I will buy it .

How do you want to cool an out runner under water?

[Clarin]

Here are some high rpm gearbox:
http://www.acpd.co.uk/ple-planetary-gearboxes.html

[dirty_d]

I like the idea of using something like this https://www.mhz-watercraft.com/shop/en/ ... 6104?c=110 direct drive to something like one of those 52mm impellers https://www.mhz-watercraft.com/shop/en/ ... part?c=110. Cooling an in-runner is simple, and there's no gears to wear out. The pump housing could be molded in carbon fiber like this https://www.youtube.com/watch?v=JXzw8iymV5I

I think you'd definitely want some kind of bearing support right by the impeller on the intake side of the pump so it's not impeding flow too much. That could just be a simple piece of aluminum machined and epoxied into the housing.

[notafraidtotry]

A friend and I have decided to jump on the Electric surfboard bandwagon and the foil idea seems to be the best in terms of efficiency and probably simpler to build (famous last words).

I have a 3D printer so have made a start on both a Jet Pump similar to those from Mhz Watercraft and also a 3D printed Hydrofoil (that would then be laminated in carbon).

The Jet pump is quite nice with a 65mm propeller, you can see the plans here and can download them for $12.

https://cults3d.com/en/various/water-jet-pump


I am waiting on the drive shaft and some bearings to arrive before I can test.

The Hydrofoil is shaping up nicely. I downloaded some plans that were available on Grabcad, sliced them so I could then print on my i3 Prusa Mk2. I started documenting the build here,

http://nealedesigns.co.uk/3d-printed-hydrofoil/

I'm happy to share the foil .stl files or gcodes if you have a similar printer. The Jet pump files you will have to purchase yourself from Cult3D. So far I have printed the rear and front wings and the printer is in the middle of printing the fuselage.

I am going to have to modify the mast design as I would like to have a tube running down the centre to take the power cables for the motor. I have no idea how to design or edit anything in OpenSCAD so please jump in if you think you can help. The foil has been built by the designer and he shares his photos on GrabCad.

https://grabcad.com/library/kitefoil-hy ... id=2902073

The motor is proving more of a challenge. Pacificmeister seems to have got a bargain with his Gerarbox for $60 as they seem to be over $300. A gearbox is also less than ideal. However there may be a bit of good news from Bruno at Alien Power System. I got in touch to ask about low Kv in runners and he mentioned that they are developing a 58mm 80Kv inrunner motor. No detail yet on specs or pricing. He just responded this morning to say wait a few weeks for more info. Sounds very promising though. Most other motors that will run at around 3,000 RPM and have sufficient power are either out runners or just too big.

Enclosing an out runner is plan B although there do seem too be a lot of ROV builders who just run out-runners in sea water without short term issues. I can't see it lasting all that long before corrosion eats away something important but it might be good enough to test other parts of the construction.

The board is likely to be a recycled surfboard. My friend Nick is begging a board or two from a contact of his. Hope to share more soon, especially on the 3D printed foil.

[Hiorth]

Hello fellow makers!

Me and my brother are also building a e-hydrofoil. Will post more updates as we go. Thanks to pacificmeister for awesome instructions on youtube!!! Though about building this when we saw the efoil the first time. He made the process a whole lot easier!

Brief summary of our progress so far:

Motor: Check (480 KV SSS 56104)
ESC: Check (seaking V3 130A)
Controller: RC controller first (will build a bluetooth-arduino controller later)
Battery: 4x 6 cell LiPo
Shaft seal: 2x with different diameter to ensure no leaks. http://uk.rs-online.com/web/p/seals-o-rings/8289223/
Aluminium housing: Check (60x57mm)

Foil mount, propeller and other custom parts: We are drawing them now (will order in SLS 3d printet Nylon and mill some aluminium parts ourself)

Hydrofoil: Being designed from scratch, A bit uncertain on what profile etc we should use. But will use a large front wing to get early lift.

Gearbox: Really difficult to find something Cheap and Usable. Found a used PARKER BAYSIDE PV40TN-005 5:1 on EBAY for 99$, so will use this. The rated RPM is max 8500. But I think the main problem with higher speeds are heat generated inside the gearbox, so we will add cooling aluminium ribs that touches the gearbox and the aluminium casing. We might also change the lubricant to an lubricant made for high speeds. Hopefully this will increase the lifetime of the gearbox to some degree.

Good luck to all builders!

[nanni]

How do you want to cool an out runner under water?

If you want there's a water cooled version of the 80100 http://alienpowersystem.com/shop/brushl ... tercooled/ , i don't know for the 6374 . Remember that Bruno can supply different motors, with custom power and KV.

[NolaDoogie]

I cant believe I didn't think about this earlier!
From the mockup of the battery for the lift e-foil, one can see that there are 196 cells.
They have also stated that they can achieve around 1hr ride time depending on rider weight.
Therefore they can only be running 7S or 14S
If we then assume a cell capacity of 3400mAh.

In 7S config:
total capacity - 95200mAh
average current draw (for an hour) - 95.2A
average power (using max cell voltage) - 2798.88W

In 14S:
total capacity - 47600mAh
average current draw (for an hour) - 47.6A
average power (using max cell voltage) - 2798.88W

So we can see that the average power draw to keep a rider up on the foil for an hour would be +-2.8kW.

From this it should make it a bit easier to select a motor and then an ESC that will do the job!

I love this kind of analysis. Great job Jezza, I think this is some of the most useful information we have to tackle this problem. One thing I want to ask. Is it not standard to only discharge li-ion to 20% capacity which, in a 14s setup, would allow only 38,000mAh of useful capacity? I feel like a dog chasing its tail thinking about this but would this 20% margin reduce or increase the power requirement of the motor for the hour?

Also, I agree with others that a direct drive (no gearbox) setup would be ideal and have read that alienpower may be producing an in-runner just for this purpose. One question we don't hear much is in regard to the torque requirement for an electric hydrofoil. Water is 800x denser than air and the convention in multirotors is that to produce high torque you equip with "pancake" motors having large diameters and if you want high rpm you choose motors with narrow diameters. Of course this is solved with planetary gearing which trades rpm for torque. What is the opinion of the community on this? Can a narrow diameter inrunner produce enough torque to drive our propellers at the necessary RPM without the use of gearing?

[ropower86]

many times they put (non-exiting) products online to see the customer feedback.
even show it ready to order. but will just produce it when enough people buy it.

2000-3000$
an other supplier
https://m.alibaba.com/product/606682766 ... .20.DSyqg2

It's surprising that Chinese factories cannot produce a reliable jet board or e- hydrofoil. Yet they are using other people images as their own product. A guy had purchased a knockoff gas powered jetsurf, it was twice as heavy compared to the original. That thing broke down in the middle of the deep blue sea and had to be towed with a jetski. THat knock off jetsruf that he paid $7000 for never even started again. Takes 3 to 4 guys to get the board in the truck. Anyways how Chinese advertise is always a dead giveaway there pictures/info is never consistent. lol

[ropower86]

I cant believe I didn't think about this earlier!
From the mockup of the battery for the lift e-foil, one can see that there are 196 cells.
They have also stated that they can achieve around 1hr ride time depending on rider weight.
Therefore they can only be running 7S or 14S
If we then assume a cell capacity of 3400mAh.

In 7S config:
total capacity - 95200mAh
average current draw (for an hour) - 95.2A
average power (using max cell voltage) - 2798.88W

In 14S:
total capacity - 47600mAh
average current draw (for an hour) - 47.6A
average power (using max cell voltage) - 2798.88W

So we can see that the average power draw to keep a rider up on the foil for an hour would be +-2.8kW.

From this it should make it a bit easier to select a motor and then an ESC that will do the job!

I love this kind of analysis. Great job Jezza, I think this is some of the most useful information we have to tackle this problem. One thing I want to ask. Is it not standard to only discharge li-ion to 20% capacity which, in a 14s setup, would allow only 38,000mAh of useful capacity? I feel like a dog chasing its tail thinking about this but would this 20% margin reduce or increase the power requirement of the motor for the hour?

Also, I agree with others that a direct drive (no gearbox) setup would be ideal and have read that alienpower may be producing an in-runner just for this purpose. One question we don't hear much is in regard to the torque requirement for an electric hydrofoil. Water is 800x denser than air and the convention in multirotors is that to produce high torque you equip with "pancake" motors having large diameters and if you want high rpm you choose motors with narrow diameters. Of course this is solved with planetary gearing which trades rpm for torque. What is the opinion of the community on this? Can a narrow diameter inrunner produce enough torque to drive our propellers at the necessary RPM without the use of gearing?

There is a very variable to consider in the bldc motors for direct drive. One of the variables is the pole count, stator, wind thickness/strands. Running a motor on a direct shaft is a major load, for in runners they tend to get hot a lot faster unless there is a cooling system setup. Having a gearbox reduce the amp draw drastically, a motor can pull 40a then 200a. Still, we don't know until we test it. I am using a KDE 295kv motor for my jet board with a homemade jet drive. Getting close to done and test it after everything looks promising then I will convert it to a jetfoil.

[Gege2000]

Do you saw the orange propeller finally used by pacificmeister? (vid 12) A lot of pitch. Any idea of the reference?

[bbq870]

@notafraidtotry
your project looks cool! pls post some results here.
one thing though... I think your 3D printed wings should have not been split like that.
they should have an overlap of 10-15cm (otherwise its too much stress in the split area)

curious about the progress
(especially the 3D printed jet

[NolaDoogie]

Does anyone know if the liftfoil or jetfoil systems use a gearbox?

[dirty_d]

NolaDoogie, they almost certainly do based on the size of the propeller compared to the size of the motor housing. I really think the best way of doing this is the same as pacificmiester did. An inrunner and inline gearbox gives you a slender drive that minimizes drag, and it lets you use a larger more efficient propeller. A jet drive lets you go direct drive, but I have a feeling the efficiency you lose using a jet drive is higher than what you lose through a gearbox. The gearboxes look pretty pricey though, and it would be ideal to be able to have an input speed well over 20,000rpm to be able to take advantage of the power available out of those in-runners. That SSS 56104 motor is spec'ed at 14,000W, but that is probably at around 40,000 - 50,000rpm.

[notafraidtotry]

@notafraidtotry
your project looks cool! pls post some results here.
one thing though... I think your 3D printed wings should have not been split like that.
they should have an overlap of 10-15cm (otherwise its too much stress in the split area)

curious about the progress
(especially the 3D printed jet

Hi, I am getting along with the 3D printed parts fairly well. I had to wait for some more filament to arrive. You can se the latest progress on the blog here, http://nealedesigns.co.uk/electric-surf ... il-update/

@Hiorth from this forum suggested I use Onshape to add the wiring run through the centre of there mast. It took me a while but I managed to get this to work. The test piece came out well so I am printing the rest now.

https://i1.wp.com/nealedesigns.co.uk/wp ... 553571.jpg

You can't see it on the test piece but the mast is at 20% infill using a very strong cubic infill. Takes ages but it gives a lot of strength and won't allow water to travel far if there is damage.

https://i2.wp.com/nealedesigns.co.uk/wp ... G_4833.jpg

You are right about the parts not being strong enough. I didn't try to do anything clever with the joins as 1. I am useless at CAD but 2. I am planning on laminating in carbon. I'd love to use as-is but suspect it will break. PLA is quite brittle. The fuselage especially is quite thin in places and will likely have heavy loads placed on it.

Here is a link to the separate .STL files I put together for the kitefoil based on the GrabCad design from Michele Fiorentino https://grabcad.com/library/kitefoil-hydrofoil-1.

https://app.box.com/s/m4xb1eznj440zme59y47phijdajm4xae

Note, you will need to cut the parts to fit your printer and there are two masts in there. The original with no hole and the modified one with a hole running down the centre (not all the way though). See my blog for more details on this.

[toto44]

Hello,
I am the designer of the waterjet from Cults. As I am working on the foil too, I designed a special jet for it.Here are 2 pics. I printed all parts, and received the motor (5692/ 540KV) it should run on 12s battery, and can be fittet to the fin / mast.

jet1.jpg (223.99 KiB) Viewed 1055 times

jet2.jpg (151.77 KiB) Viewed 1055 times

To Notafraidtotry:

do you think the foil will work? As I found out, there are basically 2 types. The ones for kites have the rear wing mounted inverted, so that it creates a downforce. This is to counterweight the force from the kite, which goes into the other direction. The others have the rear wing like a plane, no force or even upforce. I think, as the jet or propdrive mounted on the mast, will give a rotating moment to the oppsite direction of the kite, the rear wing should give no or better upforce.

Greetings
Toto

[Gege2000]

Hello,
I am the designer of the waterjet from Cults. As I am working on the foil too, I designed a special jet for it.Here are 2 pics. I printed all parts, and received the motor (5692/ 540KV) it should run on 12s battery, and can be fittet to the fin / mast.

Hello, had you think about optimising the water entrance flow? It seems that there is a lot of loss in your design (same problem with the tests made here : https://www.youtube.com/user/vayrus7/videos).

My 2 cents.

[toto44]

I already designed another version, but as the first one is printed, I am going to test this one first.

jet3.jpg (159.67 KiB) Viewed 1055 times

[notafraidtotry]

Hello,
I am the designer of the waterjet from Cults. As I am working on the foil too, I designed a special jet for it.Here are 2 pics. I printed all parts, and received the motor (5692/ 540KV) it should run on 12s battery, and can be fittet to the fin / mast.

jet1.jpg

jet2.jpg

To Notafraidtotry:

do you think the foil will work? As I found out, there are basically 2 types. The ones for kites have the rear wing mounted inverted, so that it creates a downforce. This is to counterweight the force from the kite, which goes into the other direction. The others have the rear wing like a plane, no force or even upforce. I think, as the jet or propdrive mounted on the mast, will give a rotating moment to the oppsite direction of the kite, the rear wing should give no or better upforce.

Greetings
Toto

Hi Toto.

I just got the drive shaft and bearings through in the post for your Cult3D jet design so looking forward to testing it. I'll probably make a big RC boat for the children.

I like the look of your new jet a lot. My friend Nick and I have been struggling like many others to find a good drive system for the efoil.

Regarding the rear wing on the foil. I wasn't sure if it would work or not so both the front and rear wings will be removable. The rear actually has relatively little curvature.

[NolaDoogie]

NolaDoogie, they almost certainly do based on the size of the propeller compared to the size of the motor housing. I really think the best way of doing this is the same as pacificmiester did. An inrunner and inline gearbox gives you a slender drive that minimizes drag, and it lets you use a larger more efficient propeller. A jet drive lets you go direct drive, but I have a feeling the efficiency you lose using a jet drive is higher than what you lose through a gearbox. The gearboxes look pretty pricey though, and it would be ideal to be able to have an input speed well over 20,000rpm to be able to take advantage of the power available out of those in-runners. That SSS 56104 motor is spec'ed at 14,000W, but that is probably at around 40,000 - 50,000rpm.

Yea, I'm starting to come around to the idea of a gearbox. Ideally I'd like to eliminate it but....... physics. The gearbox is such a catch 22. We'll get great power from 20k RPM motors but finding a gearbox that can handle that kind of input speed is difficult and costly at best. Do we know the specs/limitations of the Torqeedo gearbox? (http://www.torqeedo.com/us/en-us/produc ... 00005.html)

I'd buy it if I knew it's limitations; input speed, torque limitation etc. I guess if it works for them it should work for us.

[toto44]

https://www.neugart.com/en/products/pla ... ple/#PLE40

PLE 40 should be strong enough.

[Gege2000]

Some pictures of the jetfoiler prototype : https://eyeforce.nl/video/citysurfer/ (at 00:20).

@ toto44, your new version looks better!

[Jezza]

Yea, I'm starting to come around to the idea of a gearbox. Ideally I'd like to eliminate it but....... physics. The gearbox is such a catch 22. We'll get great power from 20k RPM motors but finding a gearbox that can handle that kind of input speed is difficult and costly at best. Do we know the specs/limitations of the Torqeedo gearbox? (http://www.torqeedo.com/us/en-us/produc ... 00005.html)

I'd buy it if I knew it's limitations; input speed, torque limitation etc. I guess if it works for them it should work for us.

The torqeedo 1003 gearbox is by far the most substantial gearbox available on the market. I have one and it seems pretty solid! Will handle 20k input speed (I'm going to be throwing 37k rpm at it).

Some pictures of the jetfoiler prototype : https://eyeforce.nl/video/citysurfer/ (at 00:20).

So not a jetfoiler at all...

[FROGMANGEEK]

This prototype use a regular APC epropeller , seams good, need more info about it ! Perhaps he didn t used any gearbox .