Hey guys, this semester I’ll be building an efoil as a college project. As for now I’m just in the investigation phase. We’re a group of 6 and we’ll be building everything from scratch, including the board, mast, hydrofoil, propulsion system, etc… Right now I have the most doubts about the parts required for the propulsion system and water cooling, any tips for a fellow beginner foil builder? 
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Here’s the general idea, I took the mast, propulsion system and hydrofoil cad files from grabcad. But i’ll be required to model them myself in about a week.
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Are you planning on building the motor from scratch or buying a motor?
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Buying the motor, but i’ve read about direct drive motors or geared motors and I’m uncertain what to choose
The giant fish tail in the board is purely aesthetic and will complicate your life when laminating and sanding the board. Use shapes that are nicely rounded as it makes this process a lot easier and faster.
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Thanks for the info! I wasn’t sure if it was going to give the board any type of advantage, but man I thought it looked cool.
I wouldn’t bother with gears at this stage, you may as well get a 100Kv direct drive unit from the likes of Flipsky (best price): https://flipsky.net/collections/e-skateboard/products/brushless-sensored-motor-amphibious-fully-waterproof-motor-65161-195kv-6000w-for-efoil-ejet-boards-ebike?variant=29299334185020
Then you can focus attention on the mast clamp and prop.
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Thanks for the quick responses man! I’m so thankful I found this site as I’m sure it’ll be a great help throughout this project 
For the likes of efoils, a square or squash tail makes the most sense. Easy to glass, board can stand on it easily if stood upright and also harder to ding than anything with a sharp point. Also less likely to stab you or anyone else…
Hi,
I am also Still wondering what is the big drawback for this particular motor, flipsky, except for the demanded 14s. 400 $ seems quite cheap if you can skip gearbox and lots of time as well as sealing material and so on.
You’re absolutely right, might give it another personal touch on the design that won’t give me that much trouble
I’m pretty sure it would spin with a very low voltage battery. However I wouldn’t recommend using it with less than 12S.
@amart1214 go ahead and take a good long read of the thread over at: New Direct Drive Inrunner 65150 - Propulsion System (Motor, Gears) - FOIL.zone to backup what @Jezza is saying. It seems for ease let alone money direct drive is the new way to go. The forums started out following @pacificmeister and all his info in the: Pacificmeister Build Info and CAD Sources - Builds - FOIL.zone but the more you read the more you’ll learn and like everyone on here all our ideas are advancing and the direct drive seems to be the ‘new’ way forward. The 65150 thread also goes into batteries and esc etc. and at this stage nearly has a fully designed setup for all of the electronics. Most of the main contributors on that thread are on their 2nd or 3rd build and all started off with the original build type being motor gearbox etc so a lot of prototyping is done for you.
For the foil there are a million different options - most seem to be buying the foil but others have had good success with home made. All I can suggest is that you go for 90cm mast (stays in the water longer for beginners) with a large front wing (makes it slower to ride but easier for beginners) - make it bolt on so you can replace it as you get better at riding.
Everyone is very friendly and all I can say is - its been done a 100 different ways but a 100 different people - spend a good lot of time reading this forum, it has a section for most items you’ll need and then makeup your own mind. Enjoy it!
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@amart1214 I am going to provide a more conclusive list so that you don’t necessarily need to read the whole forum or re-invent the wheel.
Board: I have already given you some advice in this area around the shape. I think its good to advise a bit on size too. Length: around 5ft to 5ft 6inches, this will make the board easier to handle and a lot more fun as soon as you stand. Width: 63cm, you don’t need wider than that. Thickness: This will be calculated by taking into account the depth of hatch, hatch lid and where you attach the foil. Hatch: make sure your hatch is a decent size, around 745 x 400 and 75mm deep (from bottom of hatch lid to floor of hatch) this allows your mast to link directly to the hatch and also gives you enough space for electronics etc.
Ultimately look at the top commercial companies like Lift, Fliteboard and Flying Rodeo and see if you can improve on any part of their designs. They are the top for a reason.
Foil: Don’t make the mast longer than 80cm. I have cut all my 90cm masts down to 80cm so that they are easier to travel with internationally in a standard luggage bag. I have multiple setups with one mast even as short as 45cm and its easy enough to e-foil. Allow enough space for 8 AWG wires and an 8mm OD cooling pipe to run through the mast. Wings/Fuselage: There are a lot out there but take a look at the Lift wings and see what can be improved. Maybe make them detachable from fuselage in case you want to pack things easily or travel with them.
Batteries: 18650 Li-Ion all the way. 14S would be the best option with enough cells in parallel to allow for max amp draw of about 200A (you shouldn’t hit it, but the overhead means the cells generate less heat). Lift use 14S14P and so do Fliteboard. Make it watertight. Someone posted a nice BMS the other day with bluetooth connectivity that is a very good option. I use BMS for charge only and fuse the output for discharge, but that’s a personal preference as it allows me to use a cheaper BMS.
ESC/Speed controller: I use the ARC200 which I can’t speed highly enough about. It has all the features you need and is quieter than the RC style hobby ESC’s. Freefly also has fantastic customer service. Other good hobby based ESC’s I can recommend are the Castle 160HV. The new 200A VESC could be an option, but I don’t have any experience with them.
Don’t buy a Hifei Swordfish, they are noisy and customer service is a nightmare if you have issues with them.
Motor: I don’t really see a point of not going direct drive like the 65150 motor.
This is a very good thread on builds, I’d say probably the best board build on here: Eduard´s Build from Germany - Builds - FOIL.zone
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