RIWI’s third build


My third build. Building board from scratch. Eps 300 core. Prefab electric box and carbon fiber+epoxy shell.

Maytech Vesc 200A.
Flipsky antispark
Water cooling(no pump)
12s NMC 42Ah.


Foil and propulsion:
Gong mast 65cm
Hiorth design propulsion
Moses wing and stab




Regarding water cooling of the esc and the anti spark.

The anti spark from flipsky (v.2 280A) comes with wires the size of spaghetti. I changed the to 8awg on the battery side and used the 10 awg from the esc on the other side.

I used chain saw file, approx 5mm, to create grooves in which the 6mm copper break pipe could be soldered. In order to solder copper to aluminum I used a special flux and solder. You need an open flame to join the two materials.

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Would you have pictures of box + lid fabrication ?

For the box I made a mold in wood which a sanded with 400 grit, painted and waxed before laying up the fabric. I don’t have time for two part molds so I made small holes, three per side, through which I blow air in order to release the finished box from the mold. Works like a charm. This is the mold, you can see the first layer of peel ply.


After the box is released and fitted to the board it looks like this:

The lid is another story. I always do the lid after the board is almost complete, this will give the best fit.

I make a “plug” in eps that fills the box. I don’t make the plug flat, it’s stronger if it’s a bit curved.

The eps is covers with vinyl, epoxy does not stick to it.

After this I apply epoxy, fabric, core material and so on. I used vacuum to extract any extra epoxy and air.
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How far is the middle of your mast plate to the back of the board?

Approx 16cm


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It is way back! So I’m assuming you are standing further back on the board? Any pics of you riding it?

Same as my two earlier boards. Works perfect.
This one has not been in the water yet but you can see pics and videos of the other two at instagram.com/wildtech.eu

I also think that it is good to have it so far at the back. I always have to stand so much at the front.

Mast as far back as possible is the best solution :+1:

First run last night. Current was to low, set to default 80A by Vesc motor wizard. Did another test this morning, setting the current to 120A. Still not enough power to get it planning.

Have now loaded the “no limit firmware” and set current to 150A.

The board is small, only 53L, so it will require a lot of power to rake of. Hopefully I can test later today.

Setting current via metr work fine.


Back in the water again after the maytech failure.

Now running the yep 120 modified with a larger cap bank and heat sink. Works great!

I got a “problem” in speeds over 27kmh. I sound, and feels like air is being sucked down trough the mast and interfering with the prop. The faster I go the more it sound/feels.

Could also be disturbances from the nut pockets in the prints?

Has anyone seen this? what did you do to fix it?



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The fastest way to see if its the nuts is to put tape over them and take a ride. Another option would be to remove the duct and see if it’s causing issues…

I started by putting tape over the bolts that hold the fuselage to the mast, I have 2 extra holes now since I use the mosses fuselage on the gong mast, didn’t do much.

I’m thinking air is being sucked down trough the mast at high speed. I will try to make the mast airtight at the top, that would be easier then trying to seal all holes down below.

Yes seal the top of the mast, that will solve it. Air will get sucked down at higher speeds which makes this strange sucking sound.

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What about facilitating the phenomenon with an air intake to see where it takes you? I have in mind the skwal torpedoes :thinking: :blush:

what temps were you seeing? I’m running the same ESC and have had a hard time keeping it cool. Ended up adding a water jacket to the bottom of the AL box I’ve got it in, but still had to raise temp limits in VESC tool to make it ridable.

Up to 85, I used water cooling as well.

I think it’s poor design, riding my yep 120A now and it works like a charm.