Efoil Mast Reinforcement

Hello all,

While overthinking about my efoil build, I’ve realized that not all masts are created equal. I currently have a LF mast and it has been performing great! Never bent and doesn’t seem to flex too much (it does flex a bit tho). Also, its profile is quite thinner than let’s say the axis 19mm mast that’s a lot bigger (LF mast is 13.5 wide). I considered upgrading to the Axis mast but that would mean more drag and I’d have to machine a new mast clamp and adaptors.

So my question is… Would it be possible to stiffen up the LF mast by adding inner reinforcement in the empty parts of the mast. The LF mast comes with a 20cm alu block plug at the top to make it less prone to bending. However, we have to take it out to run the wires in the mast. I do plan to put back as much as I can of it but is there something else I could do? Add carbon fiber rods down the screw holes? Add full length alu block or stainless steel? Throw in your ideas! Also, let me know if I’m too far down the overthinking path lol. :joy:

If you culd put carbon tubes inside, largest diameter that you can safely squeeze in.
When you position them right (maybe using custom made template), then put polyurethane mounting foam inside the mast. It would hold the tubes in place and add to the rigidity.

Just my thinking

The biggest diameter carbon fiber rod would be 8mm. Do you think that’s stiff enough over 30in to add rigidity? I guess anything inserted in the empty space can help to an extent but if I buy carbon fiber rods, I want to make sure that it will make at least a bit of difference.

Hi Victor,
I have done this with a Fanatic mast - two carbon rods and 3 glassfiber tubes to run the cables and filled with low viscosity epoxy - a friend of mine has calculated 15% more stiffness:

Please remember that the connection from the mast to the fuselage must carry a lot of load.


Do you have a link to those glassfiber tubes? Are the rods running full length or do they stop at the motot mounting point?

The rods and the tubes running full length and the tubes are closed with a 3D printed to keep the epoxy from running into the pipe.

Glasfaser-Rohre pultrudiert

I have a gong mast which flexes a lot. I plan a three layer composite overlay:
200 g/m2 glass fibre cloth
+/-45 degrees coaxial carbon for torsion stiffness
100g/m2 UD carbon for bending stiffness

The stuff put inside the mast won’t be as effective, it needs to be as far out as possible from the center for stiffness.

PS don’t get pultruded tubes. They have very low torsion strength and stiffness.
Pullwinded are a lot better: https://shop1.r-g.de/en/art/730806-PW

Are you sure the flex is not at the joint on the fuselage?

Yes, i think i could break the mast easily if i tried.

Interesting, how much do you weigh that you feel it would break easily?

I weigh slightly above 0.1 tons

That’s one way to put it :joy::joy::joy: I’m glad I’m not the only one with the dilemma! Personally, I think I will reinforce the inside of the mast with carbon fiber rods! Adding layers on the outside is a whole other project! You should look into getting a 19mm axis mast instead!

Yes, i probably should, they look stiff!

Carbon overlaying isn’t that hard though.

that’s how the 19mm looks! Massive!

Dang it! Now i want one. If i could get it used but not paying the premium price of a new one. Yeez they charge a lot for a short aluminum extrusion.

Mast plate and mast is less than 250$ so it’s not too bad! But you’ll need a gong adaptor and new mast clamp etc. Which is why I’m looking to reinforce my current LF mast instead.

Any chance you know a supplier in the US? Or another name for pull winding rods! It seems like they are not as commonly available as the pultruded version!

Would something like this be equivalent?

yes, certainly a lot better than pultruded tubes, the only advantage of these is a low price. I wonder if a pullwinding glass fibre tube might even be stronger than a pultruded carbon one…

You need to consider the galvanic corrosion risk if you go with carbon. Tubes must be completely isolated from the aluminum either with resin or glass fibre.

I think you should try break a gong mast… I bet all the flex you are feeling is at the joint there the wing/fuselage meets the mast. All the pump and wing foils guys have reported the same.