Very slow build from France

thank you for the advise @agniusm, i tried a few set up and yes this one is the best:

  • positive on the tab with foam , inserting first, push it forward when sliding the negative down
  • put cells on the side then in the middle in the module

my built has been put aside for a couple week, i needed time to figure out my board: i will make my own to fit my specifications instead of trying to mod this one …

and the main reason is that for the moment i am more buying PAMPERS (again) then Efoils parts :slight_smile:

i took me sometimes to understand how a brushless motor works, probably due to my combustion engine background building and mapping

i was missing the right part of a dyno chart for a brushless:


so back to my post : rpm drop…

from :

About the torque of electric motors:
Brushless dc motors have constant torque (after the initial startup rpm has been reached so the ESC knows the rotor position). With rotational speed the voltage produced by the turning motor rises, if this generated voltage gets close to your battery voltage you can not drive the motor any faster. Thats why there is the trick called field weakening. Field weakening changes the timing of the current through your motor phase wires. Now not all current is used in the moment for optimal torque. Some of the current is used to weaken the field of the permanent magnets on your motor‘s rotor. This reduces the voltage produced by your turning motor. So your battery voltage is higher again and you can accelerate your motor further. This comes at the cost of less torque. You could also look at this as if the motors KV number was higher in this area. I think for most uses here you sould not need the field weakening/constant power area. So basically bldc motors have constant torque and therefore power rises with rpm :wink: I‘m not even sure if most ESCs implement field weakening, except maybe for the timing parameters.
I found this graph with a quick image search:

Of course the numbers differ for every motor, but the form should always be the same. I would argue that your efoils design point should not be in the field weakening area.


Very nice build ! Thank you for all the informations you give :slight_smile:

Having a some fun … :wink: i will try to post a update soon


Dear Alexandre,

Did you size down your SOLAS propeller ? From what diameter to what diameter ?

I need to size down a SOLAS alu prop from 190mm, not sure until how many mm …

Have a great day,


@EXOGLIDE i sized down the plastic solas prop to 145mm not the alu one , my guess is max 25% off the original after you are lossing the pitch…

better check your solders on the sss motor
this is from a brand new tfl sss motor after 3 unplug :

Here my SOLAS propeller diameter 196 mm that i plan to reduce to 150 mm.

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Starting the battery pack

Oups i have done something wrong …


How much you paid for the cells an equipment in total?

Around 1000€ , for 6s8p x 4 with 30q
It is worth it for safety , high discharge and second built ( after the cells are dead)

So that means 12S and 48Ah? And how much you spend for the cells and how much for the rest?

Yes , I have to Check but cells are 3€ now so around 600€ and 400€ for nese modules

Cells on nkon
Modules 1s8p : 24x14€

And 500gr x 24 : 12kg for 12s 48a


getting ready for first test: same board ,Foil and gearbox as last year.
2019 running FOC
I updated esc: vesc trampa 75/300 air cooled, battery 18650 ,12s 24A (30q) , and motor 56104 480kv
First test : no propeller no seal :130w

Still battery box on top of the board and only 1/2 of it ( planning 12s48A ) , will see how it goes before building the new board …

The funny thing : the vesc advise me to run max 65A for the motor after setting up … But of course i put 90A :smile:


Nice job Alexandre on the box, can you share us dimensions and supplier info, i m looking now to put all in box then avoid waterproof hatch in the board, i have trouble to make my hatch waterproof so on the new board, I plan to just make a hole in the board to receive the box. I have only 110mm high so may be the box will be a bit too high on the board, but not really a problem.

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got my module , took me forever to connect it … finally switch tx and rx pins on the cable…
Update iOS on my iPhone (at least ios11 so for iphone 5 at least…)
Update fw on the vesc (fw3.57 without buged it )
Switch baudrate then back to original via usb …
And finally got data display on my phone :triumph:
Can read and set vesc config live without Pc as well, very nice


Hello Alexandre,
i also have the vesc 75/300 but it has an intern bluetooth Modul so you didn’t need an external modul, your vesc didnt have an intern modul?

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well i didn’t know about THAT ! and i ordered as well the bluetooth modul from trampa at the time !!!

that explains a lot since i was seeing a bluetooth connection from my vesc with my pc… but i was enable to connect with window on the vesc (probably needed android ? for vesctool)
since i wanted to use my iphone (don’t have android 8+ on anything) for data logging, i needed to buy the metr at module in order to use the app with the pin code

from trampa web page :

" Beautiful! All you need is a Bluetooth module to interchange the data with your phone, computer or tablet. Even firmware updates and configuration can be done wirless now."


From memory the VESC Bluetooth is only available under ANDROID… so for IPhone holders who have to use