OK, So I just found the diy efoil to be really interesting. Here’s where I’m at:
I’m in Colorado, but planning to be out on the east coast with my ebike and camper after mid may.
That means a 30 day build.
Battery - I have 120 Molicel P42A’s on my bench. I also have a spot welder. I picked these up to make a new/spare for my used ebike but I was able to bring the ebike pack back to life. I have some BMS options, I’m more likely to limit BMS to charge and then wide open discharge.
Motor/Controller - I think I can get these quick enough. I’m still considering what controller/esc to use and if I want water cooling with ocean water. Definitely open to ideas here.
3d printing - I have an ender 6, it’s doing well I can print whatever.
Board - This is the long pole. I think I need to build it to make this go. I’d need to route out the battery and esc spots and add a decent bolt position for a foil. I don’t mind buying but I’m not dropping a grand on a board either.
Foil - I’ve seen several deals, I think I can get something decent for like $400 and not stress.
So. How do I pull this off? I can bring along whatever tools, but the board needs to be done before I travel. Thoughts?
battery - I skipped the whole spot welding thing and BMS and use two 6S lipo in series. this lets me charge them with a normal RC charger, fast - both charge at 500w. I had to buy a crimping tool because I used 8awg wire everywhere. It’s generally protected by a slow-blow 200A breaker.
when you connect the battery to the charger you can analyze it for a cell failing etc, really not that big of a deal. look for internal resistance
motor/controller use flipsky. hand controller Maytech. both ship via DHL, delivery within 3 days. I got the one with water cooling. also the bluetooth adapter. Need to buy the VESC app on phone for $2.50
If you can print PETG that’s the most durable - but some parts you will want TPU. for example the clamp I used to fasten the motor to the mast is TPU, but the motor mount/bracket itself is PETG.
board - if you are good at composites that’s great. I found a used carbon kitesurfing board for $200.
foil - I used Naish Thrust foil and mast combo with the delta wing. I don’t think they have it for sale anymore, but the parts are on discount right now and you can piece together a kit. Just need a mast, fuse, delta wing(WS 1) and back wing (WS 2). lucky I got the kit for $500
in total I think I spent under $3k, not really tracking budget… i know it’s a lot less than $12k LOL
Windsurf board, pelican battery case strapped to the board, or routed down into it and fiberglassed if you want to get fancy. ESC was in a waterproof metal box with the bottom exposed to the water - seemed to work well enough. I would put the pelican toward the front of the board instead of back, it got in the way of my feet depending on what foil I was using.
Ended up doing a lid which worked pretty meh. Then hit a sandbar on boyd and ripped off the foil… And built a new one from scratch out of foam and carbon fiber.
OOh, I found a place that sells blocks of polystyrene foam in 1,2,3lb density and cheap shipping. Little slow due to covid, but I think I can work with it, and if they fail to deliver I can go get foam at home depot as a backup plan.
Allrighty, I’m committed. I just ordered a naish foil to build this thing. I opted for a 2019 Thrust kite foil, with the hope that it’ll be a bit more stable for the efoil. It has the Abracadabra mount, but I don’t think that running wiring ouside the top of the foil will cause much in the way of drag, especially if I add a 3d printed cover for that connection.
I’m considering the idea of epoxy coating the battery pack. It could be very interesting to minimize the dry box requirements. Either way, I’m definitely building a custom pack for this thing.
I’m a bit torn on water cooling. I want to use this in salt and fresh water - I don’t want to deal with corrosion. I could see a closed loop cooler as an option, maybe with a custom heat sink that’s in the water. Biggest pain here will be disconnecting the foil from the board for travel.
More parts are on the way. I’ve decided that this is getting the 100v/250a trampa vesc that was gonna go on my ebike. It should be plenty and doesn’t require water cooling - so it’ll be good for salt water.
Motor is on the way, picked up a flipsky 120kv from @nickrandy
I also ordered a flipsky vx3 remote - seemed like the only readily available waterproof remote.
I suppose I need to start playing with pack dimensions. I’m a little different here, the P43A cells I have are 4200mah 21700s. I have 120 on hand.
Max size would just be 20s6p - 72v nominal pack, 84v full charge 6p putting me at 25.2Ah if I use them all.
Most people are doing 12s 14s, and a few 16s. The worry at higher voltages it a shock hazard in the water. I got a 12s12p 30q and currently building a 14p10s pack.
Foil and motor, ESC, battery cells and a 100a BMS are here.
The foil is a nice piece. I’m impressed with the niash quality.
I eyeballed foam at lowes this weekend, wasn’t happy. I’ll give the concrete shops a shot today but otherwise I’m grabbing the pink extruded to get this going.
There’s just no way I can get the board built in 3-4 weeks unless I start shaping this week.
I’m doing a test print of this clamp right now.
Half is almost done, I’m optimisitic that it may just fit without mods.
For motivation, I’ve got the Naish mast in my office space to taunt me daily.
Foam hunt continues. Slowed down from friggin food poisoning. bleh.
Anyhow, I got to thinking about water and batteries.
I’m seriously considering a Pelican 1495 laptop case to hold my cells.
I kinda like the idea of making a diy case using aluminum sides and glass or carbon sheet, but in the spirit of the quick build I’m digging the pelican case approach.
I admit, I am liking the idea of being able to easily lug the battery pack separately from the board too…
buy some cheap aluminums to mod and mess with (gonna drill out a yamaha prop)
Today I picked up a new planer, so I should be able to shape something decent. I am having a hard time getting a good quantity of polyurethane glue, so I finally just ordered it online. Seems like a bit of a shortage is happening there.
So the plan this weekend is to slice and glue up a 4 inch blank, then shape it down and get glass on it early next week. Biggest questions are down to how much to cutout for the battery and esc installs.
