DIY eFoil Build – From a Block of Foam to a Flying Board

[crivenco]

Hi everyone!

After spending countless hours reading build logs here, I finally decided it’s time to share my own project.

This is my first DIY eFoil, and instead of buying a complete kit, I wanted to build as much as possible myself. The goal wasn’t just to save money—it was to understand every single part of the system and learn along the way.

This thread will document the entire build from start to finish.

So far I’ve already completed (or nearly completed) most of the major components, and I’ll be posting the whole journey with lots of photos and technical details.

Here’s what you can expect:

• Choosing and buying all the components
• Designing the board in CAD
• CNC cutting the EPS foam core
• Laminating multiple layers of fiberglass and carbon fiber
• 🪽 Designing and building my own front wing
• Building a custom 15S16P battery pack (BEAST!)
• Installing the BMS and waterproof electrical system
• VESC configuration and tuning
• Bench testing the motor and battery before the first ride
• (Hopefully…) successful water testing

Project Specs

Board

• Custom CNC-cut EPS core
• Carbon fiber + fiberglass composite construction
• Approx. 168 cm × 60 cm
• Custom designed from scratch

Battery

• 15S16P
• LG M50LT 21700 cells
• Around 80 Ah capacity
• JK Smart BMS with active balancing

Electronics

• Flipsky FSESC 75200 Pro V2
• Flipsky VX3 Pro remote
• Flipsky 65161 120KV motor

Propulsion

• Folding propeller
• Custom waterproof wiring and connectors

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One thing I wanted from the beginning was reliability.

I know many DIY projects focus on making the lightest or cheapest possible board, but my priority has always been building something robust that I can trust on the water.

That meant spending a lot of time thinking about waterproofing, battery safety, connector reliability, cooling, and serviceability—not just performance.

I’m sure I’ve made mistakes already (and probably many more are coming ), so I really appreciate any suggestions, criticism, or ideas from experienced builders.

I’ll keep updating this thread as I organize the photos from each stage of the build.

Next posts will cover:

1. CAD design
2. CNC machining
3. Lamination process
4. Wing manufacturing
5. Battery build
6. Electronics installation
7. VESC setup
8. Bench tests
9. First ride

Hopefully this build log will also help someone else who’s thinking about building their own eFoil.

Thanks for reading, and let’s see if this thing actually flies!

[crivenco]

Part 1 – CAD Design

Before cutting any foam, I spent quite a bit of time designing the board in CAD.

Since this is my first eFoil, I wasn’t trying to build the smallest or lightest board. My priorities were stability, enough internal space for the battery and electronics, and a design that I could actually manufacture myself.

Final dimensions:

• 1680 × 600 × 130 mm
• ~71.7 L volume

After a lot of small adjustments, I finally had a model I was happy with.

Next step: turning the CAD model into a real board on the CNC machine.
V1 that was ugly and I refused to build it almost from the start:

V2 my actual board design:

Battery, controller, motor, wing, stabilizer …

[crivenco]

Part 2 – CNC Cutting and 3D printing

Time to make some filament foam dust.

The board was cut from an EPS foam block on a CNC machine. Seeing the CAD model turn into a real board was definitely one of the most satisfying moments of the project.

The machining came out better than I expected, with only a little hand finishing needed before lamination:

- YouTube

- YouTube

- YouTube

Wing, battery case and motor holder on 3D printer:

- YouTube

[HOF]

Nice!

Noticed you have an absolutely huge battery, whats the thinking behind it? i have 1/3 of yours and im satisfied with almost 1h run time.

[Foilguy]

A few things since you asked😉

Why a folding prop?
Why that size of battery? - larger than most.
I would suggest a VX5 remote - a bit more expensive than VX3 but proven reliable.
You don’t list what foil setup you are using.

[crivenco]

I made a first test, I tried to get up on this board for an hour, and I spent 15-20% of the battery

[crivenco]

1. I bought few different props and I’ll test them all
2. I knew that my board will be heavy, and I have a lot of friends that want to use it when we will go somwhere to swim. And I decided to make a battery for all of us and that’s mean that everyone can take his time and enjoy the ride for >20-30min
3. I bought a kit where VX3 was already included 1 year ago, and VX5 appears just now. Be sure that on next season I’ll buy VX5

[elnillo]

I would also advise to half the battery. 2x 15S8P instead of 1x 15S16P
Less weight on board → more sporty foiling.
If you build your smaller second board, you will have less space for the 15S16P.

[crivenco]

Part 3 – Fiberglass & Carbon Fiber Lamination

After CNC machining and final shaping, it was time to turn the foam core into a real composite board.

I used a combination of 2x fiberglass and 1x carbon fiber layers to reinforce the structure.

The main goals were:

• Keep the board strong and stiff
• Protect the foam core
• Create a durable surface for everyday use

The lamination process was probably one of the most important and challenging parts of the build. A lot of preparation, sanding, and patience went into getting everything right.

Still learning with composites, so this was a big step for me.

there you can see that I installed mast holder made of steel reinforced with carbon:

then the battery hole reinforced with carbon:

- YouTube

- YouTube

[crivenco]

I think you are right, and I’ll made one smaller battery

[crivenco]

Part 4 – Battery Pack & First Motor Test

The heart of the project — the battery.

I built a custom 15S16P battery pack using LG INR21700-M50LT cells.

Battery specs:

• 15S16P configuration
• 80 Ah capacity
• ~54V nominal voltage
• JK Smart BMS with active balancing (JK-B2A20S20P-HC)
• 40A charging capability
• 22kg weight 22 KARL!((

For the ESC I chose:

• Flipsky FSESC 75200 Pro V2

Motor:

• Flipsky 65161 120KV

Before installing everything into the board, I wanted to make sure the battery, BMS, controller, and motor were working correctly.

First power-up test was successful — the motor started smoothly and the system responded as expected.

- YouTube

Next step: waterproofing, final assembly, and preparing for the first water test.

[S_Roger]

Wow, nice work @crivenco! That board looks very nice and well done so far.

I do agree with other comments about the battery being big, over 4kwh is massive! I have the same LG cells is a 10S11P configuration. That is around 2kwh and less than half the number of cells you have. I already think that battery is too heavy and I cannot imagine trying to handle your battery.
It should be capable of flying, but the swing weight of the battery will affect the handling and the feel of the board on your feet. Turning may be difficult, if you lean to far it will tip right over if you don’t have sufficient speed/lift.

[Windigo]

Very nice work! I agrree with others the battery unnecessarily big and heavy. I use a 10S 55 A/H and I have gotten 1.5 hours out of it but usually after an hour I have had enough. You battery could last like 3 hours but you will need superhuman strength for your legs to last that long efoiling.

[ludwig_bre]

@Windigo

you will need superhuman strength for you legs to last that long efoiling

And superhuman strength carrying this big battery to the water

But it looks very nicely built!

[crivenco]

thanks guys for the feedback, as I said previously, I’ll make one more battery, and it will be twice smaller

[newguy]

I am not sure about your wing construction. From copilot - I came accross a guy making a hydrofoil wing with two layers of carbon and fiberglass with no vaccuum bagging. Please provide a short assessment

See my thinking

That build is very marginal structurally for a hydrofoil wing.

• Two layers of carbon + fiberglass, no vacuum bagging usually means:
  • Low fiber volume fraction → too much resin, weak and brittle.
  • Poor consolidation → air pockets, voids, and uneven bond between layers.
  • High risk of delamination under bending and torsion.

For:

• Slow, low‑load use (hand‑towed, small waves) → it might survive, but still not ideal.
• eFoil / powered / heavier rider → I would not trust it. The wing sees high cyclic loads and torsion; this layup is likely underbuilt and poorly consolidated.

Short verdict: okay as a learning experiment, not okay as a serious, load‑bearing hydrofoil wing.

Please add a statement about compatibolity of fiberglass and carbon in the way they handle loads

Here’s the tightened assessment with the added point about carbon vs fiberglass load behavior — this is the part most people overlook, and it matters a lot for hydrofoil wings.

Short assessment with load‑compatibility note

A hydrofoil wing built with only two layers of carbon and fiberglass, without vacuum bagging, is structurally very weak. The layup will have low fiber volume, excess resin, poor consolidation, and a high chance of voids or delamination. It might survive slow, low‑load riding, but it’s not appropriate for eFoil or any high‑load foiling.

Carbon and fiberglass also handle loads very differently. Carbon is stiff and carries load immediately, while fiberglass is more elastic and deflects under load. When you combine them in a thin, poorly consolidated layup, carbon takes almost all the stress while fiberglass contributes very little. This mismatch causes:

• shear stress between layers,
• early delamination,
• loss of torsional rigidity,
• and fatigue failure under cyclic bending.

In a properly engineered foil, these materials can complement each other — but only with correct thickness, fiber orientation, and vacuum consolidation. In a thin, hand‑laminated wing, they are not compatible enough to share loads safely.

Bottom line: acceptable as a learning experiment, not acceptable as a real hydrofoil wing.

[newguy]

Copilot can guide you on how many layers of carbon you need and types of carbon (unidirectional, ets) to use.

[crivenco]

Thanks for the analysis. I have to admit, it’s quite impressive how AI can already write such confident engineering reviews

Just to clarify the actual build: the wing has 4 layers of fiberglass and 1 layer of carbon , not only two layers as assumed. After lamination I also applied a UV-protective coating.

I have already tested this wing in flight and had no structural issues. My main concern was actually the wing angle and performance, not the strength. A 90 kg rider tested it without any problems, which was a very nice surprise. I’m 75 kg, so for my riding style this wing is more than sufficient.

I agree that vacuum bagging and optimized layups are better for production-level foils, but real-world testing also gives some useful data

[crivenco]

by the way, my first ride

first ride efoil

[newguy]

Congrats!!! It works.