Foil-piercing foil board


Hi All,
Just found your site. What a bloody wonderful idea. Nice job.

Hoping to get some feedback/ input for a new design I’ve been working on over the next few months.

I’m hoping to create an eboard that is easy to use by almost anyone. I’m an old 130Kg fat boy - so if I can fly it - anyone can :slight_smile:

Design parameters are…
Maximum takeoff weight = 175Kgs
Board volume = 325 ltrs
Flying height = 500mm
Wings fly around 250mm below the surface.
Take-off speed = 5mph
Cruising Speed = 15mph
Maximum speed around 20mph
Power requirement at take-off around 6KW
Cruising power requirement 1 - 1.5 KW

As you can see by the sketches below it is a tripod-orientated piercing type foil. Lift is balanced between forward and aft wings. The reasoning behind this kind of design are that it should be ultra stable - Longitudinally the front/ rear wings are spaced around 2m apart and the rider stands/ sits in the middle third portion of the distance. Transversely the wide arms provide additional stability against rolling.

I’m about to start the build. Hoping you guy’s might be able to advise on anything I’ve missed.


that foils going to cost a fortune, great idea all the same. my mate helping me build our foil suggested a similar approach. you could possibly move the curved foil back and attach the rear stablizer to the back with the prop in the middle


Or make the foil out of straight aluminium extrusions that get connected at the corners. I have some expereience with extrusions and all kinds of connectors if you need.


Maybe it would even be possible to bend straight aluminium extrusions into a round shape? would be interesting to try :slight_smile: I suppose it would be possible with the correct bend radiuses and geometry of the extrusion.


Sure, in theory you can bend it with the right parameters for the geometry.


Many thanks for the feedback. my experience - When someone else thinks of the same or similar solution then the indicators are for a sound concept. Hopefully :-):wink:
I think the fundamental differences between this design and pretty much every other foil board design is that it is a piercing design with both front and rear wings are loaded - i.e. there is not a stabiliser wing. The way in which it works is that when the board is at-rest clearly the front wing is massively larger than the rear. As the speed increases the front wing produces more lift than the rear which means the board lifts the front higher and faster than the rear. As the front foil lifts out of the water the wetted area reduces, lift drops and an equilibrium develops to balance out the loads between front and rear. In theory at least there is no balancing that you have to do on a single wing that will make it easier to ride.
Initially we thought of a single mast with a chuffing long body to mount the the front wing well-forward. However the loads were considerable. That said with the use of two arms working mid-ships might give us an advantage if we reduce the distance between the wings to say 1 - 1,5 m.
We intend to use contra-rotating props - The reason is that the ‘kick’ when starting the motor’s off is eliminated. Having the two blades in the middle means we can potentially eliminate the complexity of a gear box and hollow shafts etc by using two motors providing of course we can work the props around a continuous shaft :slight_smile:
Will give that some thought. Thanks again.


Hi MaxMaker & Hiorth,
Many Thanks for the feedback. The front wing is quite a complex 3D curve plus the cross section changes both in size and shape. Actually it has become even more complicated since I’ve introduced more fluid-dynamic details as the design is finalised.

I think it would be possible that someone with fabrication skills could roll an extrusion and/or fabricate the front wing from sheet - however my DIY skills are no where near that capable capable. However with the miracle of Fusion 360, 3D printers and USB milling machines anything seems possible now.

The proposed build is as follows…

The Board.
There needs to be quite a bit of structural integrity in the board since it will need to support around 135Kgs between the arms and the mast. For this reason a skeleton made up of cnc cut 4mm ply is to be created first. Standard foam blanking will be glued into this. The whole board is then wrapped in glass fibre and strengthened in critical areas with carbon fibre and kevlar.

For the front & rear wings, arms & mast
The core of the front foil will be 3D printed in segments (My printer volume is only 200x200x180) which are then assembled in a jig to ensure alignment. The jig will be simple to build out of tubing and 3D parts. Sitting out dimensions will be pulled out of Fusion.
The trick is being able to create the core light enough. The flying RC boys are leading the way on creating light-weight 3D prints… I’m taking a lot of inspiration from those guy’s - - Quite incredible what can be done with 3D printing that has a practical use.

The assemble 3D cores will be wrapped in Carbon fibre and Kevlar.

Drive and motor.
I’ll be using a new 6KW Alien Power inrunner motor. These should be available Jan/ Feb of the new year. Details are sketchy at the moment but I do believe they are based around an 80mm dia body. This single motor will drive contra-rotating props through a gearbox I’ll be designing and building myself. As soon as I have this design I’ll share the details.

Couple of things I have still yet to design/ confirm that maybe you can help me with…

  1. Speed Controller. Other than putting a skateboard unit in a plastic bag… has anyone designed anything else that is a little more refined?

  2. Batteries. I was planning on building my own flush-fitting power pack that is a simple drop-in and lock utilising the carry handle to provide the locking mechanism. Has anyone any experience in sourcing LI-Poly AA-sized cells they can help me source?

  3. Battery & Speed Controller Cooling. I was thinking of using aluminium plating and water cooling them. It would make sense to use the surrounding water to do that. However the only place you can place the intakes are down towards the wings. Which means that there is a considerable head that needs to be overcome by the pump. Has anyone experience in cooling these components and if so - what appears to be the best to use?

Many Thanks for your help