Efoil stuctrural mast (Batteries and electronics inside the mast)

Hello fellow foilers!

I’ve been working on something exciting in the efoil world, and I’d love to get your thoughts. We’ve developed a unique alternative solution compatible with multiple brand wings (Gong, Sabfoil, Axis and others) with adapters. Our prototype is up and running!

Our concept involves a specially designed efoil mast with all the electronics seamlessly integrated – motor, batteries, and remote receiver, all in one. Plus, it boasts a 1.1kWh battery and a powerful 6kw motor. When cruising, it sips around 700w, giving you approximately 1.2 hours of ride time.

I’m curious to hear your feedback. What are your current foiling needs, and what pain points do you experience? Your insights could help shape the future of foiling!


Our instagram Ray Foil: https://www.instagram.com/rayfoil.surf/

Great concept

How do you fit 1.1kWh in the mast?

Rough calcs would be 14S5P molicel P42a pack putting the mast about 1000mm long?

An assist with batteries in a mast would be cool. Hmmmm

Their mast is thicker and has a chord almost double the length of a normal mast.

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Great work, just what im looking for. Takuma is also suposed to be releasing some thing similar in summer 2023. .

The mast fits 11 to 12 rows depending on the length you like. Each row can fit 5 elements parallel. One of the highest capacity and still decent IR elements is the Samsung 50S (35A max discharge, 4900mAh).

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Too bad you arrive only now with a novelty shown in boots since May 2023.
Great concept anyway. What will be the price tag not present on https://www.rayfoil.surf/ yet ?
In case you don’t reach the waterproofness you expect inside a mast, will you go the nano VORTEX route again as shown November 2022 based on a 2021 PWRfoil concept ? The late Canadian Vortex was announced in April 2022 .


Hey! We haven’t yet decided on the price.

The new Ray mast version is designed to be 100% waterproof.

Last year’s alu box prototype (on the screenshot above) was also a great concept. However, this approach had some problems: Heavy, and difficult to set up (need to motor cables to the box).

We try to make the Ray product as simple to use as possible and lightweight, transport, and travel-friendly.


I would like it like foil-assist - less than 500wh, mast height 85cm


The ratings are very dependant on conditions and Samsung actually rates the cells at 25A Max current.

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700w is the cruising consumption. It’s about 30A from the battery. So about 6A constant per cell constant. Bat current is limited to 90A. You will need it for a ~5sec to accelerate. Max current per cell is about 18A.

The mast has imposing size…

I wonder whether the drag increase is significant when you double the mast thickness on a short submerged length L that is not that much once the foil is flying (L = propeller diameter + 5cm [or 2"]).

Homework for monday :wink: :
→ - Chord length and thickness of a scaled up V2 Gong mast able to welcome such a pack of five 21700 cells ? Could be hollow…
→ Does the wall thickness need to vary linearly with the mast thickness to resist to the load (moment of inertia ?)

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I propose 1899€ -USD for the launch price :wink: Bremote compatible to decrease the costs

For air travel, I propose a 10s5p battery in the mast splittable in 10 sets of 5 cells stackable in series to go below the 100WH limit allowed per passenger by air transport companies. Each set would be 1S5P that is (4.0x1s) x (5Ax5P) = 100WH.
A passenger could carry 2 of them. For the whole battery, one would need 4 travelling friends.

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Some airlines allow 2 x packs at 160Wh to account for larger laptop batteries etc.

Then 20 x batteries less than 100Wh to account for everything else - smart watches, ear pods and cases, ereaders etc.

So you could have 20x99Wh packs and still fly which I’m sure is not the intention of the rule.

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Are there any people that boarded a flight with a DYI battery?
Have probably to prove the capacity and type of cells…

This flat battery is esK8 based.
How to make a “Flat” 10s4p “Flex” battery: ESK8 “Flex” technology. Disclaimer: it is not waterproof “as-is” but perfect to go inside a 28+mm thick mast (the 21mm diametre of a 21700 cell + two 3mm mast walls + rackable waterproofing case still to be designed).

Prices range:

From 45usd:

To 130usd:
From 'Duck Battery Systems - 12S4P FlexPCB Build Guide - #21 by rusins - How-Tos & Esk8 mechanics - esk8.news: DIY Electric Skateboard Forums

Does the PCB limit the available output current out of the pack?

No, because the PCB copper isn’t supposed to carry any of the main current; it’s mostly for structural + balance cable organization. Nickel is overlapped so that it carries the current directly between P-groups.

The building guide: click on each of the 9 steps in the first post:


I would like very much the same thing, with a remote attachable to a wing handle

regarding the concept itself
if the bottom is not flat and something sticks out from the bottom of the board, it will cling to the water and slow you down. when you riding at high speed over the water, at some point you touch the water with the part protruding from the bottom of the board, this creates an additional tilt of the nose of the board and you are already completely in the water