Electric Surf Board

some progress.

turns out, custom building a carbon fiber surfboard from eps is pretty difficult.

making batteries next!
 

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That's an amazing work!
Looks like you have choosen a really big volume for your board. Did you run some calculations for that or did you just follow your feeling?
 
Frizzo said:
That's an amazing work!
Looks like you have choosen a really big volume for your board. Did you run some calculations for that or did you just follow your feeling?

thanks frizzo.

its a little rough in places. i may sand it down smooth, and apply a final hot coat of resin. but for now, the planing surface is smooth, and its water tight, i hope!

yeah its big. about 140 liters of volume, 2.2 meters long, 600mm wide at the middle. i used to windsurf and standup surf a lot, so i kinda drew from those experiences. 140l should be pretty buoyant, and the 600mm wide should mean i get a slower planing speed, so im hoping it will give the board the best chance of getting on the plane.

i guess i'll find out soon, maybe this weekend if everything comes together i can test it on a lake
 
Well, let's hope for the best!

It also seems to me that your jet unit is kinda going underwater. Doesn't that lead to thrust losses?

Cheers
 
Did someone add this one already?

https://newatlas.com/radinn-g2x-electric-wakeboard/53160/

radinn-g2x-electric-wakeboard-8.jpg
 
Frizzo said:
Well, let's hope for the best!

It also seems to me that your jet unit is kinda going underwater. Doesn't that lead to thrust losses?

Cheers
I think the same.
 
water seperation happens below the body of the jet. so the actual jet outlet will be out of the water.
this way water doesn't have to be sucked upwards into the jet, and it reduces the inertia at the inlet sucking the board down, and preventing it from planing.

well, ill see if it works tomorrow.

seems like onean had the same idea
 

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Good job dude!
That look's AWSOME!! :D
So I'm thinking to sell my Lehner and buy your same motor.. cheaper and work well too apparently... :)
 
thanks frizzo. tbh, i didnt really expect it to work so well. i mean i expected it would move forward, but it was faster than i thought, happy surprise!

i think the lehner torquestar is probably a much better motor, but this one works also.

ill have a few more full charges and try outs before i fully recommend the motor i bought, see if it burns out or not. unfortunately i got kicked of the lake i was on today after about 5 mins so didnt get to fully hammer it for a full charge.

just out of interest. does anyone know of a good explanation on rewinding a motor? im curious to learn more about getting more power or torque out of a motor. thanks
 
https://www.youtube.com/watch?v=-sIVpOLYoqg

maybe this?

Also, how do you think about using this: https://www.amazon.com/gp/product/B01HI1LG2Y/ref=s9_acsd_zwish_hd_bw_bB8qPGN_c_x_w/144-0767002-5635359?pf_rd_m=ATVPDKIKX0DER&pf_rd_s=merchandised-search-8&pf_rd_r=QEVC17JK31065RJVXB8R&pf_rd_t=101&pf_rd_p=4800edfe-6800-5d8d-b02d-0063057f8665&pf_rd_i=10208162011

for your slippery board?

Would maybe be cheaper than pads...
 
perfect thanks

as it happens, i ordered exactly that pad material just last week! the carbon is real slippery. especially when your feet are numb from the 2 degree water
 
Yeah... can imagine that.
Did you take measurements of the ESC temperature and Ampere? Would be interesting to know if the ESC can really handle the 300 A.
And also see if nothink burns out :D
 
i measured current when testing the jet drive in a 50 gallon drum. it was drawing about 150 amps at full load.

i didnt measure temperature of the esc or motor. but after testing it in the lake for about 5 mins on full throttle, the esc was, i would say about 45 deg c, and the motor outside was prob about 35 deg c. although the motor being an outrunner, i guess thats not really an indication of the temp of the copper windings. also the esc has a pretty chunky aluminium body/case, so i dont really know what the temps were inside.

like i said, let me thrash it on a couple full charges and ill see how it does.
 
this looks like a good source of info for the how and why of rewinding motors https://www.rcgroups.com/forums/showthread.php?240993-(Re)winding-and-building-motors-tips-tricks-checks-tests
 
chris_kline said:
well, it worked!

first test https://youtu.be/QXQUv2pck1Y

Hello Chris,
congratulations, it looks really good.
But be honest, I think you increased the video speed ? The waves are moving fast .. :wink:
Anyways it is visible that the board is driving fast and has good gliding ability.
 
thanks

although that really is the actual video speed.

ill post another one of me waving on the board, maybe that will help show the speed more clearly
 
ok, so heres the very first test so you can see the film isnt sped up.
the first run i was too far back on the board so it would plane, but the last two, i got into a better position to get the board planing. once it hits the plane, it just goes!

excuse my floundering on the board like a sea otter trying to stay out of the freezing water :roll:
https://youtu.be/RKrlz6btq0E
 
Frizzo said:
Chris, how is it going? Did you push the motor to its limits already?

yeah i pushed it, and the windings burned out after about 10 mins. i should have monitored the current and temps while using the board.

oh well. i contacted the company who makes the motor, and they are very helpful. they say they can produce a motor with more copper to keep the temps under control. but its chinese new years, and they wont be able to start production again until the 24th, then it will be probably about 2 weeks to arrive in romania. then probably a month in romanian customs office. anyway, im feeling impatient, so i just ordered a "lehner torqstar 3 7050"

i think the chinese motor would probably be fine. but my 79mm prop and 70mm pitch are a little aggressive for it. i have now redesigned the prop to be 79mm dia and 55mm pitch, and that coupled with a custom chinese motor would probably have been great. but unfortuately, thats not how it worked out for me.

for now the chinese esc is still working, and it has some kind of protection on it which is good!
 
srn said:
I want to use the same motor. How long do you have to wait for it ?

which one the lehner or the chinese?

the lehner wait is 10 days after payment. plus shipping time.

the chinese motor was about the same, 10 days plus shipping. but its chinese new year, so there is a delay currently. and romanian international customs is a freaking nightmare of procrastination and apathy.

honestly i think the chinese motor is pretty good, and for 150 dollars, its well worth it. i think i just gave it a little too much of a hard time with my big prop. i think your 60mm prop would be perfect with it.
 
I wanted to buy the Torqstar but was also oftentimes thinking about Alienpowersystems 83110 with 7kw.

Maybe 7kw is enough to start with ..

just dont want to buy twice.
 
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