Graupner mini jet drive - electric surfboard application

[SudorracMechEng]

I am designing an electric surfboard, i wanted to know which electric motor would be suitable to run with the graupner mini jet drive. I have a mechanical engineering background, however i am a little rusty when it comes to selecting appropriate electric motor. I do have a reasonable understanding - however, there is such a varse amount of electric motors i dont know where to begin. I was a brushless motor, that puts out atleast 1000 W - 2000 W, if this isnt putting enough thrust out, i will set up two mini jet drives. I will be using lithium ion batteries, and setting up solar cells on the front end of the board.

Any help would be great ! thankyou... also, are there any Jet Drives that are smaller than the Graupner Mini Jet 2349?

 

[jraef]

I know it's not what you came to hear, but have you thought through the feasibility on this thoroughly? 1kW from solar cells and batteries? How big is this board going to be? The size of a bus?

A quick and dirty thumbnail calc on solar cell output would say that an avearage long board could MAYBE put out 100W of power if the entire surface were covered with solar cells and completely exposed. Oh and solar cells are not exactly known for being rigid enough to stand on by the way.

Then there's the batteries. Best available (if you could afford them) will give you about 1500W/kg @ 20 seconds. So if you want 1000W output for the trip out and it takes 3 minutes, that's roughly 9kg of batteries, for one trip. The solar cell recharge, even if using the entire board surface (I guess by not being on top of it?) would then take hours to recharge after that ONE trip so to be practical you have to carry all of your power in the batteries. So two trips? 18kg of batteries. 10 trips? 90kg. So if you are now increasing the board weight by 90kg, how are you going to compensate for bouyancy? Increase the board size? Get the point?

But as to the motor? Brushless DC is going to be the way to go if you ever overcome these other hurdles. Good luck.


"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
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[itsmoked]

I will suggest the propulsion is only for wave entry. That makes this whole idea eminently more feasible.

Skogs, a big issue is that a lot of places make it illegal to use jet skis to tow surfers into the big waves that REQUIRE higher speeds to enter than a person can provide paddling.

Having the ability to "motor in" would be a boon.

This would reduce the times to occasional 5 second shots.

SudorracMechEng; Don't even worry about the motor type. Really, what do you care? Keep your focus on the mechanical side. Use off-the-shelf proven items set up just the way the R/Cers already do it. Use their battery packs, their speed controllers, and the drives. Look at the big US RC suppliers as they have all the stuff you need.

Do not even consider the solar angle until you've made the propulsion aspect work. Just provide a way to swap out the batteries easily. That allows quick 'refills' and a person could ultimately charge the batteries on that remote Mexican beach with a separate solar charger. One could be charging while the other is in use. That allows off-the-shelf solar chargers to be used. There are even nice ones that roll up.

Also consider folding propellers drives not just jet-drives. They're used on sailboats and model sailboats.

The only other issue you will have is how to control the speed controller in a wet environment. I suspect that will be one of you largest problems.




Keith Cress
kcress -

http://www.flaminsystems.com

 

[itsmoked]

Dang. Why did I think you were Gunnar Jeff? Sorry bout that.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[OperaHouse]

Why not use a little one like the have for snorkelers. Is this going to be tilt up? I'd be concerned about the drag this might have. If you can tolerate drag here is an idea. In the 20's there were some electric boats that you anchored in the water flow of a stream. The turning prop from water flow recharged the batteries. So you could recharge while surfing.