Swiss Student Team

EFOIL.builders Builds
1

Hello,

After many hours spent on this forum, I am finally opening a topic.
We are a team of 4 students from Swiss University (EPFL) studying mechanical engineering in differents topics : fluid, control system and material science. We are doing a project where we want to design a e-foil with the particularity of having a retractable mast ( I know it’s quite ambitious but we are in the Laboratory of Applied Mechanical Design).

We are choosing the motor, ESC and battery.

We are going to command the piece, and it would be interesting to have your opinion about it.

Motor : In Stock Maytech IP68 Waterproof MTI85165 200KV Inrunner Brushless Sen – Maytech.cn--Maytech official website We have decided to oversize the motor because we will have a lot of drag due to our mast the mast that will not be as profiled as a commercial mast.

Battery : We do not have time to make our own battery with 16065 Li-Ion Cell, for that case I have decided to make a Li-Po assembly with this Li-Po 6000mAh 6S 12C : https://hobbyking.com/en_us/turnigy-high-capacity-16000mah-6s-12c-multi-rotor-lipo-pack-w-xt90.html?queryID=5e38ec7c05e74343d64cf3ab1a34fd16&objectID=80206&indexName=hbk_live_products_analytics
It will be assembled in 2S2P, so it will have 32 000 mAh and 44,4V

ESC probably this one Maytech Waterproof 300A 14S 60V Watercooled ESC for Efoil Electric Sur – Maytech.cn--Maytech official website

I have multiple questions

  • First about sizing the battery, we would like to have around 30-45 min of autonomy, how can I predict that my capacity is big enough ? The Constant Discharge is 12C and Peak Discharge (10sec): 24C, therefore with a capacity of 32Ah it will give 12*32 = 384 A, is it ok with our motor and ESC?

It’s already late in the noon, I will give more information tomorrow with other questions like dimension of the board, of the foil…

Thank you and do not hesitate to give your opinion, I will try to answer as quickly as possible, but I have a lot of work haha

Ulysse

2

First of all, what is the idea behind a retractable mast?
Like foiling for a bit and then going back to a regular surfboard?
Or do you want to change like the length of the mast?

At the moment I don’t really know what to expect from the retractable mast.

3

that prop you will use?
that wings you will use?
you energy consuption depend on that prop and wings you are use.
rider weigh and riding speed also depend on energy consumption.
cheap build can reach 120 Wh/km
good build you can reach 55 Wh/km

on my first build with LiPo battery 12S 12Ah I can ride about 15-30 minutes. 30 min because I often drop from board and swim to board

4

Would you consider trying this motor?The motor KV value can be customised to 120 KV.
The thrusters we have developed with this motor can reach a maximum thrust of 44KG at 56V.
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5

Can you give more detailed figueres? At 44Kg thrust, what is rpm, what is pitch of propeller and what is batterycurrent?

6

hi ulysse,

my name is thomas and im currently working on a the same type of project for Fontus university of applied sciences. would you have time to talk about your project, my projectteam and i are very intrested in hearing what problems u faced during your project.