Electric Surf Board

The Lehner 3060/9 has about 778 rpm/V. Or at least that is what Lehner says. That value is in the Triangular configuration. In Star config. it has 1,73 factor less rpm/V = 450 rpm/V and gains 1,73 factor more torque = 240 Ncm/A in triangular = 415,2 Ncm/A in star... of course I have to test it since those are all theoretical numbers...

A 80 mm jet has an rpm of maximum 12.000 rpm. (discovered it only today. Should had done my homework better...) That means that if i take that motor in star config. at 59 V I would get about 26.550 rpm out of it. By adding then a gearbox in factor 2.2 I would get 12.068 rpm and 913,44 Ncm out of it.

But, again, those are all theoretical numbers...

And since I'm still a student, I'm kinda slow in developing my project... If there is someone in Germany building a surfjetboard too, give me a pm. It would be nice to cooperate and join our forces together.
It would be nice to discover if it would be possible to build a jetsurf with a simple gearbox instead of these really costly motors. (Lehner 7040 and Scorpion hk7455-320kv) :)
 
open
 
Frizzo said:
to attach an image go here:

Screenshot from 2017-12-12 21-35-22.png

then, click on place inline

Are you kidding me!?!?!?! All this time I was struggling to add pictures for the longest since Ive been on here. I had never paid attention to the bottom. :lol:
 
That's an amazing job!
Did you seal the edges with epoxy? How thick are the blades?
 
srn said:
chris_kline said:
Finished prop!

great work,
how did you make the screw thread ? Is this ready-to-buy part that you glued in ?

thanks. the thread part is just an m10 stainless nut. the nut bolts into the mould before injecting the resin.

hand on ill take a photo of it
 
Frizzo said:
That's an amazing job!
Did you seal the edges with epoxy? How thick are the blades?
cheers

no, i didnt seal the edges. i didnt really have any need for it. the prop pretty much came out of the mould like that. then i just broke of the thin film excess of epoxy that was kind of like webbing between the blades, and did some light sanding with "wet and dry".

the blades are not really a constant thickness so its hard to say. theyre kinda wedge shaped, with a lot of variable surface geometry. the thickest point near the center is around 4.5 mm, and near the edges the thinest points are around 2.5mm. but thats ignoring the fillets etc on center shaft and blade ends
 
here you go. i just put a nut in the mould prior to injecting epoxy
 

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chris_kline said:
here you go. i just put a nut in the mould prior to injecting epoxy

Our shape is nearly the same, but I think I will mill a new mould with same system of screw & nut.
Have not thought about this before, very good idea
 
Hi everyone, :D

Any suggestions to where and how I can buy lipo batteries via international shipping?


Thanks a lot.
 
shefler said:
Hi everyone, :D

Any suggestions to where and how I can buy lipo batteries via international shipping?


Thanks a lot.

not sure if they will do international shipping, but this is where i got my batteries from. https://www.fogstar.co.uk/
 
happy new years to all!

i need some advice. kinda new to this electric motors thing.

ok so my motor is 8kw, 48v, which i suppose would make it 166 amps peak current.

the battery was about to make, is a 14s8p battery made from panasonic NCR18650B https://www.fogstar.co.uk/collections/batteries/products/panasonic-ncr18650b-br-3400mah-6-4a

apparently their rated at 6.4A continuous current. which would give me 51.2A.

obviously this is nowhere near the 166 amps i need for full torque. im guessing maybe the cells could give 10a for short bursts which puts me at 80A.

so would i need a 14s16p battery to make this work at full rpm and torque? or is there some subtleties to this that im not aware of?

thanks in advance
 
Happy New year!

Chris, You may find some infos in this thread:

https://endless-sphere.com/forums/viewtopic.php?f=14&t=26621

Cheers
 
Frizzo said:
Happy New year!

Chris, You may find some infos in this thread:

https://endless-sphere.com/forums/viewtopic.php?f=14&t=26621

Cheers

thanks

i think to answer my own question, i should have bought these https://www.fogstar.co.uk/collections/batteries/products/samsung-30q-br-3000mah-19a

then i would have a 160A discharge rate
 
Did you think about something like this ?
https://hobbyking.com/en_us/turnigy-nano-tech-8000mah-1c-lipo-battery-xt90.html

with a 2s3p setup you will have more power, less price, less weight and less work compared to 114pcs of small batteries.

just 300$ compared to 725$
 
srn said:
Did you think about something like this ?
https://hobbyking.com/en_us/turnigy-nano-tech-8000mah-1c-lipo-battery-xt90.html

with a 2s3p setup you will have more power, less price, less weight and less work compared to 114pcs of small batteries.

just 300$ compared to 725$

yeah, that would have been a good option. i looked at ready made hobby packs before, but couldnt find anything this cheap with this kind of power.

i ended up buying this https://wholesale.fogstar.co.uk/collections/raw-cells/products/samsung-30q-box-of-100

cost 255 pounds. oh well, at least i get to learn how to make batteries from hundreds of little cells!
 
hello everyone, I'm new on this forum.. I finished to read all 20 pages of that thread.. I write from italy so I apologize in advance for my bad english.

I'm building a jet kayak with the following components:

kayak Ouassou bic sport
jet unit Graupner Jet 5
motor Tp power 5870 400 kv 9 kw at 12 s ( I mesured the rpm unload and I see 24500 rpm..so around 490 kv effective)
Esc Flier 16s 380A
I'm going to use a series/parallel pack of multistar 6s 20000mah by hobbyking.. (the cheapest one..110 eur pack)

I know the jet unit is undersized among the motor but mhz is too expensive and the jet 5 has been a gift..so I bet everything to the best motor possible.
I will post some pics..

thanks
 

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My jet unit is making progress
 

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