Oh yes a BMS cut can kill a VESC… but it depends on the quality. I feel like Flipsky controllers can vary enough that one will die while another survives. My first 75100 was killed by a BMS cutout. I am running a Spintend 100a right now that has had BMS cutout many times without issue. It really just depends on your ESC.
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good to know, I thought that the capacitors would protect the mosfets…
I have a built in BMS because i want to charge with a dumb charger and at the same time i thought to use it for discharge as well, i might use a fuse for discharge in future batteries…
i mean for what it costs it is definitely a good prop, and it definitely works, but for my conditions the efficiency is close to 20% a good prop should be somewhere between 60 and 70%
for your conditions seems to work a bit better, what do you ride a barracuda? and what speeds do you ride on 20-25 km/h?
I am not sure how you would measure those numbers or even what they represent.
Which actual prop are you taking as a reference?
I am using this as foil assist.
When I went from the Flipsky prop to FD 3 blade, the range I got out of a set of batteries stayed about the same, as did the max power required to get on foil.
The FD is just much more user-friendly when piercing the water, which makes it easier to ride.
it comes to say from the power delivered by your battery how much does it finally end up as propulsion. The drag in your foil at a given speed is constant, so if you assume the xover xxl with 85kg has a power draw of 600w (drag in newtons * speed in m/s)
with an efficiency of 25% you will be drawing 2400w. A more efficient propeller, lets say a 40% would only draw 1500w for the same outcomes.
interesting, i would have thought that tie FD props are much more efficient than flipsky…
I’m curious where that number comes from? Is it just your assumption or something that Gong published?
It is an estimation based on my foilcalculator:
here the results for turbulent and laminar for a overall weight of 100Kg and 10°C of water
the foil calculator is itself based in a good aerodynamic foundation although some estimations had to be done as well, since the airfoil shape used in foils is not public. I am hoping to validate the tool with the telemetry of my foil, but therefore i have to figure out how to stop burning mosfets… 
the foil calculator says that at 20 km/h the front wing is somewhere around 275 W, so to account for the whole foil, the pod and so on i just doubled the drag and rounded up.
OK thanks. I have never seen Gong publish specific data (as you have confirmed) so I thought perhaps you had found a source.
I have modified the BMS/VESC parameters to the following, for reference i have a 12s2p reliance rl50 pack (150A max continuous) and a 75200 from makerbase:
VESC:
cuttoff start 36v - end 35v
Battery current max 100 A
Motor current max 120 A
Absolute maximum current 180 A
The BMS config looks like this
so 31.5v cutoff start and 30v cutoff end (2,5v per cell end)
I am hoping to never get to this voltage with the VESC cutoff although i did some test with my power supply and no load, and if i was under the cutoff the VESC would not start from still but if the voltage dropped to 35 while running it was not stopping. Although this might have happened because the motor had no load
any suggestions would be much appreciated!
Between cuttof start and cuttof end, the vesc reduces the current but you can still use the motor as long as the voltage stays above cuttof end. This can help getting back to shore without discharging the battery too low. Depends on the discharge curve of the batteries, if it is going down steep towards the end, you won’t get far.
Why don’t you use the default values for VESC cutoff?
Your 36V for start of cutoff is 0% SoC.
There is basically no room between 36v and 35V.
Even with minimal load, you can expect your BMS to cutoff at the same moment.
(Or even before, depending on how accurate the voltage reading is)
If you want to avoid damage, make the VESC start to cut off at minimum 3.25V cell voltage.
To be safe make it 3.5v so you can still get to land.
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good point,
i thought that the VESC defaults are too conservative, since most people say start cutoff at 3.0v per cell and finish at 2.5v
VESCs is 3.4v cutoff start and 3,1 end.
I will give it a try 
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Looking at some output of your foilcal app my own it underestimates the power by a lot.
In my case using a gong curve v2 L and my 90kg I can foil@25kmh at 1000w. Thats using the flight prop which is know to be near if not the most efficient prop available. I have also the curve xl and xxl and the power is only marginally lower but thats also lower speeds The L is much more fun for me and I think I will get an M size coming up.
Those small wings are sadly not yet built in as I started working on the foil calculator when i was doing dockstarts and efoil was not yet a project. But when a soon as i can i want to add them.
Keep in mind while reviewing the results that the values are only the front wing, in order to calculate the overall power I assume the foil drag to be twice as the front wing alone. I have not found any Source which provides a better way to calculate this value.
a somehow close wing to your curve L is the Xover XL v3 ( slightly more surface, very close AR and thicker profile) for that wing and 90Kg at 10°C of water i get at 23.7 Km/h 213W if the wing is polished (Laminar) and 314W if the wing is completely scratched (usually a real wing is somewhere in between)
For that case the whole foil should be somewhere between 426W and 628W, if your foil is pulling 1000W, when considering the efficiency of the prop, I think they are somewhere where i would the results to be expected.
I am looking forward to measure with my efoil totally different wings (like for example a x over XXL and sirus XXL) and to provide better references than to say from the predicted 213W you are actually pulling 1000W but that will take time…
if you have VESC telemetry for the wings you have and you where prepared to share them i could used them as a reference to improve the foil calculator 
I dont think I saved any vesc files but possibly some others have. Another quite big source of drag is wind resistance of your body. Very noticeable on a breezy day when you change from an upwind to downwind course.
You calculations are probably really good but the total power seems not to be dominated by the wing. Its not even 50% typically. My friend rides an xover v2 L and his result is almost the same as mine on a given day.
No matter how good the wings are I think you will find 1000w at 25kmh is about as good as it gets unless you reduce total weight.
Propeller efficiency is really an interesting area. I have printed and tested a ton of props last summer. Now I have a design as good as the flite prop after a lot of iterations. For ease of printing and finishing a 2 blade prop works well.
Keep on playing!
Just to give some examples:
With a Curve M V2 setup I do roughly 1000-1200W to stay on foil with a Flite prop and 65161 motor.
With a Curve L with a FR 3 blade and 70175 I do roughly the same.
If you can get below 60wh/km you are very efficient.
This season I’ll test my new Veloce H V2 setup.
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Can confirm, my setup is very efficient with a north sonar ha 950 / 750 and a small stab, 14S, FR Motor and a Flite prop. Best I got was 53.3Wh/km @25km/h average speed, 95min, 2 starts.
In my experience, the size and efficiency of the foil comes into play if you run faster, like 30km/h average or more. I still get 60Wh/km @30km/h average. If I run 45km/h consumption goes up to 110Wh/km.
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yeah that’s a good point at 20-30 Km/h you can not ignore wind resistance anymore
I have been playing around with XROTOR, and i designed a prop which was supposed to be 60% efficient, althogh my flow conditions were totally wrong, i thought i would be flying at 15 km/h with a sirus XXL and a power draw around 600W. I still have to water test it, i will post my results…
i will definitely do 
I am starting to get quite curious about this flite prop… is this the one you are all talking about? prop
thank you all for your input!
Btw, i did yesterday my third test, whit the default VESC settings for cutoff and went amazing. the power draw gets also lower after the acceleration. the feeling was amazing and after 3 batteries i was already doing a few turns. to the date my record for pump foil is 22 seconds… I am looking forward to improve my pumping technique!
Yes, it is the one from your link. It has id 11mm, needs to be drilled or reamed out to 12mm.
See here: Fliteboard prop alternative to FR? - #13 by superlefax
To attach it to an outrunner like 63xx you need some sort of an adapter, this is how I mounted it: Daniels (un)geared inflatable (slowly built) - #55 by sat_be