DIY EV project: An E-Surfboard to catch waves!

[Mr. Mik]

I am trying to decide on the exact specifications of the components to be used for an electric surfboard.



Some people have taken out patents to cover this sort of project, and it seems to me that they have little understanding of surfing. It looks like they probably just patented an idea which many, many people have had, but did not bother patenting because it is sooo obvious! There is nothing ingenious about the idea, just someone trying to get rich by stopping others from marketing solutions for this application unless they pay the patent holder. The patents I have read did not contain any solutions for the practical problems that need to be solved to realize the project, just all-encompassing descriptions of the general idea that one wants to achieve. The lawyers have turned this idea into many pages, but in plain language it basically just says this:

"The patent covers any attempt to attach a motor (in)to a surfboard so that it does not stick out anywhere, therefore not negatively affecting the surfing performance".

NONE of the real problems have been solved or addressed in the patents which I have read, like how to form the channels through the board, where to place intake and outlets, how to waterproof the motor and the connections to the controller and batteries, how to cut out the power if the surfer falls off, how to prevent injuries from contact with the propeller or "live" parts whilst immersed in salt water etc. etc. etc.
It's the sort of patent that just serves to hinder progress. I'm sure other permutations of the same problem have been discussed at length by smart people for a long time, no need to start again here.

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One patent which I have read is going on and on about using a motor to assist the surfer to paddle out, so that there would be more energy left to catch waves afterward.
Either that was written by someone with no clue about surfing, or it was tailor made to fill a niche that was left open by some other patent granted earlier. Maybe there is another patent that covers the use of a motor that is integrated into a surfboard with the intent to help gain the speed necessary to catch a wave, NOT just to paddle out.

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So just in case this idea has not been covered by some patent somewhere yet: This is what I am proposing to build:

A propulsion system for surfboards, capable of providing strong bursts of acceleration, to allow the surfer to catch large waves or to make it out through the "impact zone" during a short lull in a strong swell.
I'm not too sure about that poor "Ordinary Artisan" that the lawyers seem to keep on stressing at every turn, but I know that any real surfer knows the feeling!

I really hope that this will take the wind out of any further patent applications, or at least open them up to a legal challenge if needed, because the idea is now "out there" in the public domain (as if it had not been there anyway!) and generally known.
If this idea is already patented by someone in some country, who cares, we can build whatever we want for ourselves. And as far as I understand it, one can sell kits that help others to build whatever they want for themselves!
If it is patented to someone who has actually solved some or all of the practical problems, then I'll happily buy one, test it and recommend it to others if it works!


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So, finally, lets get to the fun part: Designing that gizmo and ironing out the bugs......

What I already have is a "Turbochannel" fin and a spare fin box.
(Fin boxes gets epoxied into a surfboard and allow the insertion and removal of a variety of fins. The fins and finboxes appear to be standardized. They are mostly used in longboards. The scale in the photo is metric.)

I hope it will be possible to either install a (RC-type) E-motor into the "Tunnel", or to install one or more propeller(s) into the "Tunnel", driven by the RC-type motor via a flexible drive shaft.

If the motor is mounted inside the "Tunnel", then the propeller needs to be larger than the tunnel diameter and be mounted in front or behind of it, including a protective cage of sorts to stop it from producing minced meat if touched accidentally.

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The Tunnel is about 130mm long:

and 40mm wide at the narrowest part at the rear end:

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What I need:

A) A motor / propeller combination that makes sense.
This question is very tricky, at least for me! I hope that no throttle interface (a la Fechter) or gear reduction (a la Recumpence) is needed if the right combination is used. If the motor is too strong or too fast, then the propeller might spin inside a gas bubble underneath the water without causing much propulsion. If the propeller is too big for the motor, then the motor will be prone to overheating. 500W to 750W would probably be plenty, if reasonably efficiently transformed into propulsion.

B) A safety cutoff switch, activated by pulling on the leg rope (a strong but very stretchy piece of chemical trickery between the board and the rear leg of the surfer.)

C) An on/off switch that can handle about 80A or more without welding itself shut. This switch might also incorporate the safety switch from B), if it is designed to work like the "dead man switch" on trains etc.

D) A remote control for the ON/OFF switch, either via cable or RF.

E) All of the above in "Marine grade quality."

F) or rather: Sub-marine-quality, because the pressures encountered during the inevitable wipe-outs can be equivalent to quite deep submergence. All components need to be able to withstand at least 10m of water pressure (2ATM) for a minute or so. And occasionally a few seconds of much higher pressure when they get hit by the lip of a breaking wave.

G) An "automatic motor controller" which is capable of sensing the drag caused by the propeller and supplies just enough current to the motor to spin the propeller in "Neutral" when the "ON" button is not being pushed. That would use very little battery power, I believe.

H) The battery comes very very last in these considerations, because there are many batteries that can produce the goods once the drive unit etc. is functional: All that is needed is a full power blast for a maximum of 10 seconds.

Of course, if you had a battery that can do this 30 times over,that''l be dandy (and expensive!)
Maybe you could even afford to recharge your ES (Electric Surfboard) whilst bopping up and down on the waves, through some ultra-thin solar panels used during the construction of the board instead of fiber-glass!

Chill out and catch your breath whilst the Sun recharges your batts so you can count on a boost when you try to catch the next wave....

Yeah, yeah, tell' em he's dreamin....

 

[dogman dan]

I'm a flat water windsurfer so I know squat about real surfing, but won't the extra weight make the thing surf like a lead pig? A gallon of water inside a windsurfboard sure makes it sail lousy so this gizmo better be really light!

 

[Jay64]

I think something like this would be good on a longboard, but you wouldn't really be able to do many of the normal moves that are common nowadays with the weight you will be adding. Also, I don't know how well your fin will "cut" the water if you have a prop on the back of it, you might loose some of your steering ability. I'm not saying that it will kill you ride, hell, Kelly Slater ripped the door off the house one day and paddled out with it and actually caught a wave, it just might make you loose some of that free "surf" feeling. I think if you have the prop in the turbo tube, ala a jet turbine on a passenger plane, you would avoid some of that effect. But then you would have to figure out where to put the motor. Maybe have the motor be kind of built into the bottom of the board with an enclosure that slowly turned into the fin with the prop in the turbo. I just don't know if a prop that small would really give you a good enough boost to make it all worth it. I mean, usually when you are trying to charge out between some breaks the water is churned up quite a bit, and I think that would greatly reduce the effectiveness of the prop. Also, you don't really need assistance for dropping in on waves until they get so big that you need a tow in. I can see the draw of not having to have someone tow you into a wave, both guys get to actually ride the wave, not one guy being a water taxi, you could probably build this system for a lot less money then a wave runner, etc. However, there is a major safety advantage to having a buddy on a wave runner right outside of the break zone. If you wipe out on one of those waves, you want someone able to sweep in there and drag you out as soon as possible.
Also, if I remember correctly from my scuba diving days, I think 10 meters is about 33 feet, or about 1 atmosphere of pressure, not 2. But that was some 20 years ago, so I could be wrong on that.

 

[michaelplogue]

What you need is a miniature magnetohydrodynamic drive (like the 'caterpillar drive' in the Hunt for Red October) built into the body of the board, with retractable covers over the intake port for a completely streamlined board.......

http://www.youtube.com/watch?v=-_c0rYAckwI

http://www.evilmadscientist.com/article.php/RCMHD


.

 

[Mr. Mik]

I'm a flat water windsurfer so I know squat about real surfing, but won't the extra weight make the thing surf like a lead pig? A gallon of water inside a windsurfboard sure makes it sail lousy so this gizmo better be really light!

Of course the weight will have an impact, but I'm not into potato-chip high performance boards, anyway.
I prefer Geoff McCoy Nuggets, the best surfboards there are IMHO. They have double 6-oz glass jobs all around and are thick, wide, long and relatively heavy. And they surf wonderfully. Every aspect of these boards is designed to make surfing easier and more enjoyable for the average surfer.
Many surfers are fooled into buying what the pro's ride: Wafer-thin boards that are very light and fragile and very hard to surf. So they miss out on a lot of fun, because they are not going to be able to catch as many waves as they could on a bigger, more buoyant board.

Because of this, the added weight in a big, buoyant board is not going to be all that much. I hope to get away with less than 1.5kg total weight increase, which means about 20% added weight. Most of this weight will be the batteries and if they are mounted in the right spot (probably just forward of the fins) they will not make the board too hard to turn.

Once I have a working motorized fin I will try it out on a big old board with fin box.
Or I'll install fin boxes into suitable boards. If it turns out to be feasible and reliable enough, then I'll try to convince a shaper (hopefully Geoff McCoy himself) to design a board which compensates for the added weight of the batteries etc.

 

[dogman dan]

Yep, the ratio will be better on a boad bigger than a potato chip. On the windsurfers the issue is the time it takes to get up to speed. On a big heavy board, when a gust hits the sail, if the board won't speed up, the sail will, and then you get what we call a mousetrap. The sail flips forward at the speed of the wind, say 35 mph, taking you with it. You can easily land 30 feet in front of the surfboard, and usually it hurts pretty good. So we like the board as light as possible. Thinking about it more, if the weight is not too far forward, the board should still pivot on the fin fine. Nose weight would be bad, but weight under your feet should be no different than weighing a pound or two more.

 

[Mr. Mik]

I think if you have the prop in the turbo tube, ala a jet turbine on a passenger plane, you would avoid some of that effect. But then you would have to figure out where to put the motor. Maybe have the motor be kind of built into the bottom of the board with an enclosure that slowly turned into the fin with the prop in the turbo. I just don't know if a prop that small would really give you a good enough boost to make it all worth it.

Yes, the propeller drag is a big problem.
I have not yet seen any RC model propellers for boats which fold back when not driven by the motor. They do make folding propellers for RC sailplanes and for full size sailing yachts.
Building the motor into the board makes cooling more difficult, especially for outrunners. And the outrunners seem to be the clear winner in regards to power/weight+size ratios. An inrunner motor could possibly be cooled by water or by winding copper wires around it which then radiate out into the bottom of the board close to the water, just covered by the last layer of fibreglass. Ofcourse that would not work for an outrunner.

Another option might be a jet propulsion unit like this one: http://www.cornwallmodelboats.co.uk/acatalog/graupner_2347.html

Also, if I remember correctly from my scuba diving days, I think 10 meters is about 33 feet, or about 1 atmosphere of pressure, not 2. But that was some 20 years ago, so I could be wrong on that.

That depends on how you look at it. Going down 10m under water will add 1ATM to the already present 1ATM at sea level, making a total of 2ATM.

 

[lawsonuw]

A RC sail plane folding propeller might work out if the blades were clipped back to a smaller diameter.

Have you estimated how much thrust will be needed? This should be simple to measure with a spring scale and a person towing you around. How about a top speed? My guess is that something that looks more like a trolling motor might work best.

The water jet linked above looks interesting if it can generate enough thrust.

Marty

 

[Mr. Mik]

A RC sail plane folding propeller might work out if the blades were clipped back to a smaller diameter.

Have you estimated how much thrust will be needed? This should be simple to measure with a spring scale and a person towing you around. How about a top speed? My guess is that something that looks more like a trolling motor might work best.

The water jet linked above looks interesting if it can generate enough thrust.

Marty

I doubt that a propeller designed for use in air will work very well in water. It's all very new to me, but it's clear that the propeller design is complex and important. I found a nice site which I'll read in more detail, here is the page on propellers.

Could thrust be measured by paddling the surfboard in a pool or lake, with a line attached to the back of the board, pivoting around a pulley and lifting a weight if the thrust is equal or greater to this weight? That would then give me an indication of how much thrust I can produce myself without a motor.

Trolling motors are much too heavy and large to allow normal surfing once one is on a wave.

 

[lawsonuw]

"work" and "work well" are two different things A flat strip of metal with the ends twisted in opposite directions "works" as a propeller, not the most efficient prop ever though. So for a start a 18-24 inch folding sailplane prop cut down to 6-8 inches should work. After everything else works it's then much easier go back and make the "right" blades for it.

Paddling against a weighted rope would work for measuring thrust. A spring scale is going to be a lot quicker to setup though.

Again a small trolling motor, while not a final solution, would still help figure out how much thrust power and speed is required. Might even be able to do a bit of surfing with it if the motor was made retractable.

Marty

 

[John in CR]

A patent is a waste of time since it already exists. In fact my son and I built a proof of concept board last June. What all are missing, including your idea, is a properly sized jet drive, which doesn't currently exist. You do the appropriate engineering for a proper jet drive with an impeller in the 50-60mm diameter range, then that would be useful and patentable. All other issues are easily solved with readily available components other than a waterproof remote control switch/throttle that you'd strap on your wrist.

John

 

[Mr. Mik]

A patent is a waste of time since it already exists. In fact my son and I built a proof of concept board last June. What all are missing, including your idea, is a properly sized jet drive, which doesn't currently exist. You do the appropriate engineering for a proper jet drive with an impeller in the 50-60mm diameter range, then that would be useful and patentable. All other issues are easily solved with readily available components other than a waterproof remote control switch/throttle that you'd strap on your wrist.

John

Not sure if you understood my ranting about the patents in the way that I meant it. I do not want to patent anything, I am annoyed about the useless patents being granted to people who have not solved the problems associated with this sort of project. They have not even built a proof of concept vehicle, like you have. They just think they can patent an idea just in case...

Just a few examples, I did not read them all (and I'm sure this list is not exhaustive):

2901757 Motor propelled surfboard September, 1959 Remington 440/85
3262413 Motorized surfboard July, 1966 Douglas et al. 440/46
3324822 Motorized surfboard June, 1967 Carter, III 440/38
4020782 Convertible surfboard May, 1977 Gleason 114/55.58
4274357 Power operated surfboard June, 1981 Dawson 114/55.51
5017166 Power-driven surfboard May, 1991 Chang
6142840 Motor driven surfboard November, 2000 Efthymiou
6192817 Motorized surfboard February, 2001 Dec et al. 114/55.56
6409560 Motorized surfboard device June, 2002 Austin
6702634 Motorized surfboard device March, 2004 Jung 441/74


About the impeller size: Why do you think it needs to be so large? I do not know if you are right or not, just wondering.

I was hoping that I might be able to get away with a 40mm propeller.

Which size did you use in your proof of concept board?


The appropriate part might already exist:

Graupner Jet Propulsion Unit 5 (2347)

http://www.cornwallmodelboats.co.uk/acatalog/graupner_2347.html

Impeller 49mm
The steering nozzle incorporates an integral cooling water nipple. Suitable power plants are internal combustion engines of 15 to 30 cc capacity, and electric motors rated at a minimum of 700 Watts output power.
Length approx. 285mm
Width approx. 78mm
Height approx. 85mm
Flange Diameter: 78mm
Shaft Diameter 7mm
Weight Approx 545g

 

[John in CR]

Mr. Mik,

I assure you that you don't want to try anything with a propeller. You want an impeller so the blades are completely enclosed. Personally I'd want to get close to the power of the 50lb thrust trolling motor that we tried, though something less may prove sufficient. Just like you said something just to assist getting out and to catch any wave you want (ie perfect position isn't necessary, because you can put vastly more thrust to the water than paddling with your arms), not something to just ride around under electric power like the Chinese are already selling.

The RC jet drives may work for a test board, especially with the new much larger Graupner Jet 5 available now. I'd have to see the guts of one to copy and improve it. That stuff really has to be metal all the way thru the nozzle. eg Small nicks on the impellers of jetski drives cause noticeable decreases in performance. I found one example online of a DIY RC jet, that was all stainless and definitely up to the task, but couldn't find any contact info for the builder to get details.

Contact me if you're interested in teaming up, because I would definitely pursue prototyping, testing and production. Thanks for pointing out that Graupner has a new larger model than when I was looking last summer. Just waterproof a lithium pack to go inside the board, add one of these 2kw motors with water jacket cooling http://www.hobbycity.com/hobbycity/...oduct_Name=KB45-17XL_700kv_Brushless_Inrunner , some type of waterproof remote switch, and you're in business. You don't need steering or even throttle, just on/off. If you built the board with epoxy, it may even be possible to keep the weight in the same range as a typical long board.

I talked to a number of board builders down here, and most hated the idea, but one loved it, so I've even got someone with blanks and who knows how to make a proper board.

John

 

[Mr. Mik]

Mr. Mik,

I assure you that you don't want to try anything with a propeller. You want an impeller so the blades are completely enclosed. Personally I'd want to get close to the power of the 50lb thrust trolling motor that we tried, though something less may prove sufficient.

I bought a "fishing scale" and did a test by paddling on a blow-up mattress in the pool:

With the scales attached to the end of a polyurethane leg-rope and held by an assistant, I paddled on the mat, stationary, against the resistance of the leg-rope.

The scales max out at 6kg and I was able to paddle harder than that, but only just. The amount of effort which I could keep up for a few minutes to get out through a difficult lineup is probably around 4-5kg thrust. The maximum burst of thrust I could produce could not be measured due to the 6kg limitation of the scale used; I guess it would have been between 7 and 8kg, sustainable for 10-15 seconds only.

I'm not sure if this can technically be called "thrust", and/or how much the effect of actually moving through the water will influence the amount of thrust created by paddling. I guess that on a normally moving surfboard it becomes harder to create the same amount of thrust because your arms need to move faster than when held in position by the leg-rope in the experimental setup.

But: this "takeoff from standstill position" is a very common and frequent situation during surfing, anyway: After every duck-dive or turtle roll, and each time one swings the board around to paddle for a wave the board starts from a standstill position. And it's at those times when the most thrust is needed.

So as a result of this testing, I believe that an electric propulsion system capable of producing 8kg of thrust for a few seconds at a time would be sufficient to make a massive difference, particularly because during the initial phase of acceleration from zero one can fully contribute thrust by paddling.

If the motor is only used for about 7sec at a time, about once every minute or so, then water cooling might not be needed, and the more powerful outrunners become more feasible.

I do not understand propeller and impeller design sufficiently yet, but fully agree that it needs to be enclosed. I wonder if a propeller (or 2 ??) inside the "Turbo Tunnel" fin would work better than an impeller in the same tunnel. It appears that an impeller and the impeller housing need to be matched very closely to work well. A propeller might be more forgiving. But I am just guessing here so far.

Cavitation might be more or less of a problem for a propeller if it is mounted inside the "Turbo Tunnel" fin.

 

[John in CR]

I can't see your image of the "Turbo Tunnel Fin", but if it's something that protrudes from the bottom of the board, then the item you are looking to copy is a Kort Nozzle, which is a shrouded ducted propeller. These are used on tugboats and other boats to create more thrust, and a slower speeds they are significantly more efficient that only a prop, but at higher speeds the drag of the shroud creates too much flow resistance through the water.

My concerns would be: 1. Things getting into the propeller (fingers, toes, leash), and 2. How that protrusion and propeller would would affect board performance while surfing.

John

 

[Mr. Mik]

I can't see your image of the "Turbo Tunnel Fin",


John

The photos are in the first post in this thread. Can you see them?

 

[John in CR]

No, all I see is the word "Image", but no image. It's probably hosted at photobucket or similar, which for some reason aren't viewable from down here. It's quite common around here, and I miss out on a good 1/3 of the images linked on ES.

BTW, I my son is coming down in April for a month, so we're going to give ElectroSurf v2.0 a shot. I'll have my coast-to-coast on a single charge bike ready by then, so we'll do that first then it's all board work. I'll have him bring 2 or 3 of those new Graupner jet drives, motors, and whatever other RC stuff we'll need, so expect some results in early May.

John

 

[Mr. Mik]

Across the USA on a single charge? Are you putting a plutonium battery in there?

Here is a link to the website for the Turbo Tunnel fin, that should work and might give you some ideas:

http://www.turbotunnel.com/

 

[John in CR]

Across the USA on a single charge? Are you putting a plutonium battery in there?

No, I live in Costa Rica, so it's about 180miles. Distance isn't that big a deal, but the 2 mountains I have to cross complicate things a bit.

John

 

[theyerb]

John, I believe we've chatted about the joy off salvaging used Konions from Makita packs, non? Where in Costa do you live? I backpacked around CR last Summer from Coast to Coast and down to Panama! Gorgeous.

I am STOKED I went out on a limb and checked out out the EV forum this morning rather than my usual visit to the Electric Bike forum! I have been plotting and planning my electric surfboard for months now!, and I'm really surprised to hear others are planning almost my exact same plan! lol. Smart minds think alike...

I like the idea of using a model Graupner jet propulsion unit, or even using a small, bullet-shaped trolling motor pod attached to a long-board fin. My idea involves either of those solutions with a bank of Li-ion batteries and some sort of pressure switch to turn on the power. Good luck! I hope this thread ends up being very, very long!

Cheers,

G

 

[John in CR]

John, I believe we've chatted about the joy off salvaging used Konions from Makita packs, non? Where in Costa do you live? I backpacked around CR last Summer from Coast to Coast and down to Panama! Gorgeous.

I am STOKED I went out on a limb and checked out out the EV forum this morning rather than my usual visit to the Electric Bike forum! I have been plotting and planning my electric surfboard for months now!, and I'm really surprised to hear others are planning almost my exact same plan! lol. Smart minds think alike...

I like the idea of using a model Graupner jet propulsion unit, or even using a small, bullet-shaped trolling motor pod attached to a long-board fin. My idea involves either of those solutions with a bank of Li-ion batteries and some sort of pressure switch to turn on the power. Good luck! I hope this thread ends up being very, very long!

Cheers,

G

G,

Right now I live just northeast of San Jose, but I just found a house west of town that put's us 30-40min closer to the beach, so we're moving in April. Once the new highway opens I'll be in easy big batt pack ebike range of the Pacific with no mountain in the way, just a steady climb back to central valley level on the way home. Get yourself back down here for the month of May and you can help with prototyping and testing, after we finish establishing the coast-to-coast on a single charge world first the last week in April.

John

 

[theyerb]

Thx for the incredible offer John

 

[northernmike]

Ahhhh .. that "Turbo Tunnel" is designed to create DRAG, not thrust.



I do like the idea, though I've never surfed - good luck!

For great performing propellers look to ECO class R/C boats of europe - self righting submerged propeller designs, VERY maneuverable with amazing acelleration!

 

[theyerb]

Has anyone made any progress? I can't afford to build my current ebike while going to school and making a hydro-jet surfboard...

 

[cashflow]

Hi Mr Mik,
Have you produced a motor for a surfboard yet?
I think its a great idea for longboards and all us "older" surfers
Nick