Open eSurf (Request for Comments)

DIY motorised Surfboard
1

Hi, I’m building a DIY electric surfboard, and I thought I’d open up the components and design for feedback from others. Potentially this could turn into a DIY kit or something.

I’m calling it Open eSurf (link). This link contains a spreadsheet of parts, suppliers, and the board design.

Open eSurf is a work in progress. While I have some experience building drones and other motorized electric vehicles - this is my first jetboard design, so I’m looking for advice on:

  1. comments/suggestions on the selected parts.
  2. suggestions on suppliers.
  3. comments/suggestions on the board design (CAD will be available after I clean I build it)
  4. am I missing anything?

Thanks!

Open eSurf 2025
Open eSurf 20251789×1764 165 KB

1 Like
2

you are missing handles, good luck with your project.

3

I do have handles listed on row 16 of the linked spreadsheet, however I haven’t selected a specific part yet, so it’s not in the CAD atm.

Do you have any suggestions for good handles to use? And recommendations for placement on the board based on riding experience?

4

Usually two on the sides and one in front and one on the back, your board looks like Radinn Carve so check where they had it…

5

Hi, I think the hull shape could be improved to match the latest findings in hydrodynamics. Similarly for the water nozzle. I could give you some advice on how to do that, as I have all the necessary prerequisites. I wouldn’t bother with the grips at all right now, it’s the easiest thing to do in such a very complex project.

6

Yes any tips, advice or analysis on the shape would be greatly appreciated.

The images I posted above are from a couple iterations ago, the latest design is smaller now that I have the parts picked out, but I’m still just winging the shape so lmk how to make it better.

IMG_0354
IMG_03542142×2856 1.85 MB

IMG_0355
IMG_03551639×2148 1.57 MB

8

From the pictures, I assume that the location of the battery will allow easy and quick replacement with another battery (freshly charged). But I have some doubts if this is even necessary. If the board and jet drive get very high hydrodynamic efficiency with my help, one battery should be enough for one great ride during a day at the water. So the ability to easily and quickly swap out the battery for another battery (freshly charged) is more likely to be useful only for rentals, or somewhere on a yacht in the middle of the ocean so that more people can take turns.

I’ve been riding a high quality e-bike and e-scooter almost every day for many years, and have never had the need to take the battery out and replace it with a freshly charged one in all those years. Now in winter (in the EU) I ride a little less, depending on the weather, of course.

I think that all DIY builds are faced with problems that arise and water seepage just because the builders felt it was important to ensure easy and quick replacement of a dead battery. However, easy and quick replacement while near water is not necessary, which will make it very easy and cheaper to make the board. So the battery needs to be placed much more cleverly, but more on that another time. This saved time and cost can be used on much more significant parts of the board. For example, to make the jet-powered plug-in module at the back of the board watertight.

9

It’s a great point. If it’s a DIY build and not meant for sale, one built-in battery is more than enough for personal use not intended for rentals. I ride Onewheel every day and never needed to switch battery

10

The main reasons I want the battery removable are:

  1. weight - unlike a onewheel/e-bike, you have to carry this bulky thing to/from the water and removing the battery makes it significantly lighter (~50lbs) and more manageable.
  2. safety - charging on the water seems like a bad idea, and storing the battery in a fireproof box is good practice.
  3. maintenance - I need a way to access the electronics, so what becomes easier/cheaper by making the battery non-replaceable? I still need a water tight lit of some kind, no?

How would it work, specifically? Are you suggesting the battery is permanently fiberglass’ed into the board?

11

  1. Yes, the weight of the complete board is obviously a big issue. Especially for people who have little muscle mass, low weight (I’m only 62 kg), … This video https://www.youtube.com/watch?v=b2FUcuKrjHw shows a practical solution to easily transport a complete board not only close to the water, but actually straight in and out of the water. Transport is so easy, such a two-wheeled transport device is not difficult to make. It would be very easy for me to design it, model it in 3D Cad, manufacture it and test it with loads.

  2. Charging would be done either on shore (not directly in the water) or preferably at home. Also the board can be placed in an area where not too much damage will occur in the event of a fire.

  3. Maintenance is very necessary, for example to check the condition of the individual electrical cells of the battery, check the watertightness around the shaft or motor, etc. Similarly, I need to carry out maintenance on the e-bike and e-scooter, so again, preferably at home. And how the battery could be positioned, instead of a thousand words it can be understood from this video https://www.youtube.com/shorts/uCSbK30Myx4 First the battery module would be inserted and finally the jet drive module. This has two main advantages:

  • the centre of gravity of the board is at the lowest possible level, which gives more stability when there are waves on the surface
  • the jet-powered plug-in module is much easier to keep watertight than a long and wide lid
12

Thanks for the positive feedback. In the post in question I forgot to mention that probably nobody buys a spare battery for an e-bike. e-scooter (even onewheel), but also for a mobile phone, laptop etc. While having much more use throughout the year than an e-board only in summer. Perhaps 2 hours of riding on an e-board in one day should satisfy everyone to be able to pursue other hobbies.

13

A phone battery lasts all day. Based on the estimated power usage and battery size, this eSurf will only run for 20-30min on a full charge, and take 3-4hr to recharge. If your phone only ran for 30min you’d demand a replaceable battery, no?

14

WNT, I don’t understand two things about what you’re saying:

  1. it sounds like you are saying the battery doesn’t need to be removable, but then you agreed it needs to be accessible for maintenance, so it’s not clear how you’re proposing it actually be designed, and how that would be easier/cheaper than what I’m planning.

  2. it sounds like you’re saying the motor/jet should be removable for some reason, like the video you posted, but I can’t think of why? the video you linked shows how the same jet system can be used for multiple vehicles, but that doesn’t sounds like something I’d ever do. The motor is already waterproof, so it just needs to be bolted on the board, right?

What I’m proposing for the battery is actually exactly what is shown in the video you sent, a water resistant lid/container in the board for access, and then an inner water-proof battery case that is bolted together similar to a Fliteboard Pro.

15

Yes, the point is that the battery (of normal capacity, like a commercial battery) of the eboard should last at least 2 hours of riding and the eboard should turn great. This can only be achieved under these conditions:

  • the board must have the best possible hydrodynamic shape (this must be designed by a hydrodynamic expert)
  • the board and battery must be as light as possible (this does not apply to a 62 kg rider like me)
  • the shape of the nozzle and impeller must have the best possible hydrodynamic shape (this must be designed by a hydrodynamics expert)
  • the right engine will have to be chosen

It follows logically that a rear plug-in will allow for a possible upgrade if the motor or nozzle is not optimal. The rear plug-in module is therefore ideal for making the first prototype eboard.

16

We’re talking about an eSurf here, there is a lot of friction on the water so I’m skeptical of your claimed 2hr battery life no matter how well you design the hydrodynamics.

Commercial batteries can’t perform magic, they are typically using the same, or worse cells than I’m planning on using. Specifically, the Molicel P45B cells are among the best on the market today, and no commercial battery has secret battery technology that vastly surpasses it.

There is a nice spreadsheet floating around called ‘eFoil battery calculator’ that I’ve used to estimate a realistic runtime. The nice thing about it is that it provides an estimate in terms of how much energy is required, so it’s independent of how you get there (hydrodynamic improvement, motor improvements, etc).

battery_calc

This is a screenshot of my current estimates. There are really only two variables to play with that make a difference in runtime, the target capacity and the estimated continuous current required (which is affected by hydrodynamics and other factors).

For size/weight reasons, a 18s10p pack of 21700’s is about as big as you can go on an eSurf. The 180 cells alone will weight ~30lbs and much more once you add the bus bars, BMS, wiring, case, etc. So if you try to achieve 2hr by increasing capacity, you would need ~18s36p, which would be completely impractical from a size/weight perspective (well over 100lbs for the complete battery).

So that leaves continuous current as the only viable parameter to increase runtime. I’m currently estimating ~5kW of battery power (75A at 18s) required for continuous operation (on average). A typical commercial eSurf has between a 10-20kW motor, so this seems reasonable, but feel free to provide justification for why it’s not a good estimate. I admittedly just spitballed it, but for reference, to get to 2hr runtime we’d have to achieve ~1.3kW continuous power, which wouldn’t justify the large motors typically found in eSurfboards, so I don’t think it’s realistic.

TLDR, I agree my board shape and motor setup aren’t expertly optimized. However, putting in a lot of effort on optimizing the shape/motor/nozzle/impeller is never going to give a 4x reduction in required power (10-20% improvement is more realistic).

In conclusion, if I’ve made some incorrect assumptions or mistakes, by all means point them out, however it’s not helpful to make wild assertions without providing any details to back it up. If you are in fact an expert in hydrodynamics or impeller design, please provide specific suggestions, simulation results, detailed calculations, etc. Otherwise, please keep the baseless assertions to a minimum.