Gong V3 DIY Build

[HOF]

DIY E-Foil Build – Custom Board + Budget Performance Setup

I finally decided it was time to try e-foiling, so naturally I turned it into a full DIY project. My goal was to build something reasonably affordable but still performant. As with most DIY projects… things evolved along the way

For the foil itself, after recommendations from a couple of good friends, I decided to go with Gong.

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Build Overview

This is what the setup currently consists of:

• Custom board
• Gong Curve H v3 FG XXL front wing
• Gong Curve v3 FG XL stabilizer
• **Gong Alu Mast 19mm 85CM
• Flipsky 65220 motor (watch for AliExpress discounts )
• Samsung 50S battery – custom 14s5p pack
• Flipsky VX5 TX/RX remote (also worth watching for discounts)
• Daly Blue BMS with reed key switch (acts as a kill switch if needed)

The target budget was under €1800, but reality hit a bit:

• Upgraded remote
• Had to CNC the adapters twice

So right now the build is just above €2000.

Worth mentioning:
I already had most of the tools and some spare glass fiber and epoxy, which definitely helped keep the cost down.

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The Board

Initially, my plan was to build the board from a fully 3D printed shell.

The idea:

• Print the shell in 18 separate sections
• Glue them together
• Fill the inside with PU foam

I ran quite a few tests using different materials:

• PLA
• LW PLA
• ASA

But every option had some drawback:

• Warping
• Poor layer adhesion
• Low heat deflection
• Too heavy
• Too expensive
• Or simply too much work for the result

After fighting with this for a while, a friend stepped in and CNC-cut the board core.

Honestly… total lifesaver.

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Board Design

The board design is my own.
I initially tried to roughly copy the Fliteboard shape, but as usual the design evolved during the process because of structural constraints:

• battery case size
• component placement
• mounting structure

Final dimensions:

• Length: 149 cm
• Thickness: 11 cm
• Volume: ~90 L

I already have the itch to build something much smaller for summer, but since I’ve never actually e-foiled before, I figured starting with something more stable is the smarter choice. Hopefully I’ll get the hang of it quickly.

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Board Inserts

The board contains two main inserts:

1. Battery compartment
2. Mast mounting aluminium plate

The battery compartment is 3D printed from PCCF.

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Waterproofing

I experimented with several different designs to seal the battery compartment, but none of them worked reliably enough.

In the end I decided to keep things simple:

Stainless screws + gasket sealing.

Important detail:

• The battery is inserted from the bottom of the board.
• The battery pack itself is fully waterproof, so even if some water gets inside the compartment it shouldn’t be a problem.

For the mast adapter plate, I machined a groove and installed an O-ring seal, which should keep water out from that interface.

Structural Reinforcement

I also paid special attention to how the mast loads transfer into the board.

The forces from the aluminium mast insert are distributed into two longitudinal ribs running along the board.

Each rib is made from:

• 10 mm Airex foam
• Laminated with 80 g/m² fiberglass

This should help spread the load and avoid localized stress around the mast mount. Anddd - totally unnecessary I believe. I just bumped up the weight too much but its all good - a note for next build.

This is how the PCCF battery compartment looks like and also the aluminium board mast insert. Note that both of them mate in a specifict way between eachother and the two ribs - i know overcomplicated.

[HOF]

Foil & Motor Setup

Moving on to the foil and motor setup.

For the Gong V3 lineup, I couldn’t find a suitable motor mount for the new 19mm V3 aluminum mast, so I ended up designing and building one myself. The mount is very simple and was machined out via JLCPCB and over it I printed a simple motor front drag cone from ASA+.
During my thinking I wanted to push the motor as much in the mast as possible since the motor is extremely long and in the end just eyeballed everything Also the vertical separation from the stab is eyeballed or well the thinking behind it was: 1-2cm from the stab till the propeller and then approximately 160mm is the propeller diameter.

The motor mount fits the mast extremely well when the mast cut-out is CNC machined. After the CNC cut, I still had to do a bit of manual finishing on the edges to ensure proper perpendicularity so the motor sits perfectly aligned.

In addition to the main cut-out, I also drilled three holes in the mast for:

• Motor positive
• Motor negative
• Signal wire

The motor motor mount looks like:

The wires enter the mast at the motor mount and run internally through the mast. They exit through the original mast plate, where I machined matching holes along with an O-ring groove for sealing.

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Waterproofing

Waterproofing this section required a bit of creativity.

At the motor mount entry point, the wires are glued in place, but I also decided to silicone-seal everything for extra safety:

• Motor wires at the entry point
• Motor mount screws (2x)
• Motor mount nuts

Gong also provides silicone rubber inserts inside the mast, so combined with the sealing I did, I’m fairly confident that the mast interior should stay dry.

Just to be extra safe, I also applied silicone around the mast plate and the itself.

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Wire Protection

Where the wires exit at the mast plate, I printed a small TPU stress-relief component.

The silicone wires from Flipsky feel a bit fragile, and I had a feeling they could eventually tear from vibration or tension, so the TPU piece helps support them and reduce strain.

The stress-relief part is slightly smaller than the hole in the board, which allows it to sit neatly inside the opening without interfering with the mast installation.

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Electrical Connections

For the wiring connections I used:

• Amphenol connectors
• CnLinko 9-pin waterproof connectors (from AliExpress)

During final assembly, the connectors will be fed through the board opening one by one, and the mast plate will then be secured using 4× M6 bolts.

The mast plate seals against the board using an O-ring, and the board surface around the mounting area is completely smooth, so this should provide reliable waterproof sealing.

Propeller

The propeller setup is still a work in progress.

At the moment I’m still looking for the right prop, but a friend of mine has been designing a custom one, and I’m currently waiting for him to finish it. Once I get it, I’ll be able to test how well it matches the motor and overall setup.

I’ll update this section as soon as the prop arrives and I can start water testing the full drivetrain.

[HOF]

Battery & Control Box

This section is essentially the heart of the whole setup, since the enclosure contains:

• Battery pack
• BMS
• Receiver (VX5 RX)

This layout is possible because the motor I’m using has an integrated ESC. On paper this seemed like a great solution since it simplifies the wiring and reduces the number of components inside the board.

That said, it’s also a bit of a risk. If the integrated ESC doesn’t behave the way I want, there isn’t much flexibility compared to a standalone VESC setup. What also surprised me is that the motor has been on the market for about a year now, yet there are almost no real-world reviews of it so far.

So… I guess I’ll find out soon enough how well it works

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Enclosure

The battery box is fully waterproof and was 3D printed from PCCF in a single piece.

The main reason for making the battery completely sealed was simple:
if the main board compartment seal ever leaks, the battery will still stay protected. Also… why not add another layer of safety.

The enclosure was specifically designed around a 14S5P pack using Samsung 50S cells, with 22.7 mm spacing between cells.

Inside the enclosure, the cells are held by a custom battery bracket which serves both as a cell holder and structural support. The bracket is 3D printed from ASA, mainly to handle higher temperatures better than PLA or similar materials.

Features of the battery bracket:

• Holds the 21700 cells in precise alignment
• Includes two holes for temperature sensors
• Structurally locks into the enclosure so the entire pack cannot move once assembled

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21700 Pack

The cells were spot welded using my trusted welder with 0.15 mm pure nickel strip.

Final pack configuration:

• 14S5P
• Samsung 50S 21700 cells Super cheap on Nkon.nl

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BMS & Safety

For the BMS I chose the new DALY Blue BMS, which has worked reliably for me in several other projects.

One feature I really like is the “Key” switch function. Instead of using a traditional switch, I connected a normally-open reed switch to it.

How it works:

• Magnet away → Key disabled → Discharge MOSFETs OFF
• Magnet near → Key enabled → MOSFETs ON

So essentially the battery only becomes active when the magnet is brought close to the switch.

My plan is to use this mainly as a safety feature, preventing accidental throttle activation before I’m in the water and ready.

In theory it could also serve as a kill switch, but I’m aware that cutting power while the system is drawing a lot of current could potentially damage the VESC.

That said, I’ve used the same setup in other projects and haven’t killed a VESC yet.

Oh and also, there is a 200A fuse inside. Got it from Mauser Electronics.

Reed on the lid. This is also a place where vx5 Receiver comes and antenna, just enough space for it.

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Waterproofing

To further ensure water resistance, the entire enclosure was impregnated with Dichtol, which is a very low-viscosity sealing resin commonly used for 3D printed parts.

This process was done after installing the electrical connectors, allowing the sealant to penetrate any micro-gaps in the print and improve overall watertightness.

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Chargers

Alibaba connection supplied me with 20A 14S Charger for around 100 EUR but i also have a cheap one for 25 EUR, both work good.
Around the fast charger I printed TPU orange protections and did some cable “Y” splitting plastics. Oh and Amphenol connectors, well I had to crimp them but since the wires are to small i had to fold them twice to create enough “meat” to crimp strong.

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Final Battery Assembly

The finished battery pack looks like this:

14S5P Samsung 50S – 21700 cells
Total weight: 6.4 kg

Compact, fully sealed - already ran few benchmarks on my custom discharger and everything looks fine!

This is it until I start laminating the board

[DutchFoiler]

Amazing work! It looks very nicely engineered. Great mount design @Kian

The only thing I’d be careful with is the vesc and battery. I’ve heard 2 stories of the vesc dying (and one dead on arrival), also, the integrated 75100 vesc cannot withstand a lot. The wires are relatively thin (10awg) which s very thin for all the current it needs to withstand. So I’m simply wondering that with all the engineering you have put in the board, why did you not go for a stand alone vesc?

Also, one thing that I noted on your battery is how your main positive wire is connected. It seems to be soldered to a single tab of nickel, so all current, will be flowing through that single 10mm wide 0.15mm thick piece of nickel, which I doubt is enough for the current requirements on startup.

[HOF]

I went with higher Voltage to reduce the Amperage.

It is 2x 7mm x 0,2 mm - indeed might be a tad to little?

The thing that has me worried is the VESC. I went with this because I find it new, neat and untested Currently i left motor max at 120A and we will see if this is enough.

[Kian]

My dad and I love your motormount design!

The best compliment someone could give you is to copy you

[DutchFoiler]

Well, all current will be flowing through that single piece sinds you soldered the wire at only the end of the tab. Best would be to solder the wire over the whole cross section length.
Like this:

[HOF]

I needed this part flat, so that it sits nicely in the box. I might put on additional 0.3mm copper strip but first i want to test it out in the water. Any suggestion on how to see if this Nickel strip that i have atm is causing any issues?

I can measure heat when riding via BMS temperature probes. On my bench 20A discharge there was no significant heating.

[Windigo]

Nice work but your battery is a bit on the small side you are probably looking at 30 to 45 minutes if you go fast unless you can ride waves and not use the motor much!

[DutchFoiler]

I’d meaasure at the exact spot where th battery is soldered since this is the smallest cross section.
Maybe stick a BMS probe on there? 20A is fine since it’s a double stack. But for starts you’ll probably need 80 amps+.

[HOF]

Board Build

The board core itself was CNC cut from foam, and an PVC foam insert was added where the aluminium mast adapter plate sits.

After cutting, the edges needed some finishing. Surprisingly, this foam is extremely easy to sand, and it sands very nicely, so shaping and smoothing the board outline didn’t take long.

Once I verified the fit with the battery compartment, I started the assembly process.

First, I glued in the structural ribs, followed by the battery compartment insert. For bonding I used Mitopur E20, lightly spraying the surfaces with a water mist to activate the expanding polyurethane glue.

One important thing here was not using too much glue. When this adhesive expands, the forces can be quite strong, which could easily bend the 3D-printed insert or deform the foam core.

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Mast Plate Installation

After the inserts were secured, I sanded the EVA foam area for the aluminium mast plate, which contains 4 × M6 × 14 mm mounting holes.

The aluminium plate was then rough-sanded to improve adhesion and bonded to the EVA foam using epoxy.

Since not everything was perfectly cut and I also made a few mistakes during machining, there were several small gaps and imperfections. These were filled with a mixture of:

• Epoxy
• Glass bubbles
• Cotton fibers
• Thixotropic agent

This created a strong filler that also sands well.

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Laminating

And then came the lamination stage.

Here I made what was probably the biggest mistake of the build: vacuum bagging.

Even though I only pulled about -300 mbar, it still distorted the surface and created quite a mess. Combined with a release film that was too thick, this produced deep surface creases that were extremely annoying to sand out.

In some areas, when sanding the creases away, I actually ended up removing too much material and exposing the foam core.

So technically, I had to repair parts of the board before it even touched the water

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Final Layup

The final laminate ended up being:

Bottom:

• 4 layers of 280 g/m² twill fiberglass

Top:

• 3 layers of 280 g/m² twill fiberglass

In hindsight, this feels just barely sufficient. If I were to build it again, I would probably add one additional layer on both sides for extra stiffness.

Carbon fiber was briefly considered, but the cost difference was too large for this project.

The on/off TPU magnet switch was placed on top to form a perfect fit while poexy cures.

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Finishing

After laminating both sides, the board went through the usual long process:

1. Full sanding
2. Hot coat
3. More sanding
4. Automotive lightweight filler to close remaining gaps
5. Even more sanding

Once the surface was finally smooth, I applied spray filler primer, followed by the base color and clear coat.

Unfortunately I got a few runs in the clear coat, so that’s something I’ll need to fix in the coming days.

The final step was installing:

• EVA deck pad
• Battery compartment sealing

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Final Result & First Runs

And that’s the final result.

Overall, I’m really happy with how the project turned out. There were no major mistakes and nothing critical showed up during the first two battery runs.

Performance so far looks very promising:

• Takeoff power: ~3600 W
• Cruising / foiling: ~1100 W
• Rider weight: 100 kg

The foil setup feels like a perfect match, and the motor also seems to perform well.

Right now I’m still learning — I’m mostly riding on my knees, but in that position the board flies perfectly.

The setup also feels very agile. I can lean into turns and apply full power, and you can really feel the G-forces building.

Next step is to start doing the same while standing

I’ll update the thread in the coming weeks once I gather more real-world riding data and battery statistics.

For now what i can say is that the VESC stays around the water temperature which is very good news and that the battery goes up to 50 degrees (at the end of a drive). For battery I am waiting on a copper busbar that will fix my mistake of too little busbar Hopefully this will decrease temperatures by a bit.

The VX5 also works like a charm. My receiver is in the battery so it has to go through PCCF (this should not be an issue at all) and then some glass fibers and foam. Plus since this board is like 90L and me being 100kg+ im most of the time underwater And the signal holds just like i imagined.

Note on watertightness:

• no leaks, but very boring to screw so many screws

[Thom]

Amazing work, well done !
Is your battery waterproof by itself or do you rely on the composite door with gasket and screws ? Do you have to remove all screws all the time ?

[HOF]

Thanks! @Thom

The battery is waterproof by itself. I achieved this with 3d printing and solution like Dichtol by: Link

Yes, all the screws But its okey, I can ride for almost an hour so im tired already and wont be needing to replace the battery fast.

[HOF]

So, I managed to weight all things and it is on the lighter side of my expectations.

Gong 85cm mast + adapter plate + motor + propeller: 6,4kg
Gong foil setup (curve xxl, stab xl and the alu adapter in between + screws): 2,5kg
Battery: 6,5kg
Board with the cover: 8,1kg

Total ready to ride setup: 23,5 kg

Im already making a new board which will be a bit smaller, so if anyone is interested in this one let me know!

[DutchFoiler]

Woah, those are some nice figures. 23.5KG is really neat!
For your next build, will you redo all the electronics, or re-use them?
Maybe a stand alone vesc with a 65161? Will give you the full 6kW in power with the right battery and vesc

[HOF]

Ill stay with exactly the same electronics, Im done with this project, way to many hours spent and i"m happy with the performance. Once i get out of water everything is fine. 3500W is sufficient for me.

The board on the other hand is easy to make, nothing too complicated and i have verified so that everything works as intended. If not sold ill use it for teaching othger and keep the new, smaller one to myself.

[Foilguy]

@HOF

Im already making a new board which will be a bit smaller, so if anyone is interested in this one let me know!

If I understand correctly you are foiling on your knees. You might want to hold onto the higher volume board until you have experience standing up.

[DutchFoiler]

By the time that second board is finished, I can guarantee he will manage to stand up

[HOF]

One from yesterday, can manage a kilometer without falling in the waves. Excited for new tryouts in the upcoming month.

[HOF]

Fixed the busbar and also decided to make a smaller (in height) battery case so that it will fit new board that is going to be approx 118 mm thick.