Could you give an estimate of the force on your legs when on the foil ? or your Arms?
In a good, stiff breeze and when held steady, the kite does not provide nearly enough force to lift a person in the air -- my guess would be 1/4 of a person's weight, so maybe 25 kgf.
The force is not born by the arms, rather by a belt around the rider's waist.
To do a water start, it is necessary to make the kite dive, then swoop back up. The force exerted by the kite turning up increases quite dramatically, lifting you clear out of the water.
cessna438:
From this picture of liftfoils.com we can count 196 Li-Ion cells. Assuming a 14S14P arrangement and a modest cell capacity of 3000mAh, we can assume a capacity of 42000mAh, a voltage of 51.8 (nominal) and a power of 2.175kW
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Purely from the weight that would indicate LI Polymer batteries.
If they were LiPO4 batteries there would only be about 1.6 KWh.
EDIT that assumes of course a weightless case and electronics.
so i think your power of 2.175 Kw is a little high.
LiPO4 batteries are also physically larger.
Looking at one of the linked forums many seem to be contemplating outboard propellors, they are large and will require gearing.
Does anyone know the diameter of the efoil prop ?
My apologies, i just realised i was using an older set of tables.
With modern LiOn batteries having a density of approx1 KW per 5KG it could be up to 2.5 KW for the pack.
cessna438:
So if I used my Mega, and attached a GPS and Datalogging shield, would the code get too complicated if I tried to manage those inputs and outputs while monitoring the voltage/amperage, sending PWM to the motor, and perhaps lighting up a few LEDs? For the sake of argument lets say I abandon the bluetooth for the immediate future.
For further discussion on the mechanics of this DIY project check out Endless Sphere Forum
Also, there is a great guy documenting his attempt at this same project Here
I loved the videos! "I just want to plug it all together and turn it on!" ... "Actually, this is quite dangerous" Just like me:)
The radio controlled ESC are controlled by a timing pulse, which is quite a low rate and very easy to generate with a Mega (you can use the servo library). Monitoring the voltage is quite easy, monitoring current would need a suitable current transducer. Assuming that the values were sampled and logged every second, I think that would be well within capability of a Mega. I guess GPS could also be sampled around that rate.