My attempt at breaking the speed record! Adapting wingset to LF mast

Hello all,

I recently stumbled upon a very low priced Spotz Tuna foil online and I decided to pull the trigger and buy it. After doing some research, I found that this wingset is known for its very high top speed and since I already have a FR motor on 14S, I figured this might allow me to break the speed record or at least make an honest attempt. Here is what it looks like compared to my lift 170 classic wingset.

As you can see, it is very tiny. The full carbon construction is great and I am able to adjust the angle of the back wing. However, my liquid force mast is too big to fit in that slot.

Therefore, I was thinking to fill in the current slot with a piece of coosa board or foam, router an insert in the shape of the mast profile and add carbon fiber to solidify the insert. That way, the liquid force mast will be able to fit in the fuselage for added strength (versus just sitting on top of it). What do you guys think? What would be the best way to adapt this wingset to my LF mast? Would filling up the slot and attaching the mast on top of it work fine?

I’m curious to hear what people think the speed record is currently at?

I heard 58km/h! This was done by @Flying_Rodeo!

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I’d do an aluminium adaptor that both goes I to the mast and fuselage. I’ve done it for another unifoil wingset I have and it works great!!!

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The problem is that the slot is 10cm long and the LF mast is 12.5cm…

Just read my previous post. The mast can shift forward or backward on the adaptor. The difficulty is how much to accommodate the 2 pairs of screws.
In the US, once you have validated a STL file, send it to this guy who is used to make mast adaptors: Precision - Lichen Mfg
Here is the 3D printing step checking prior to aluminium routing.

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Yeah something like that would work! The screws are close together (58mm for LF and 70mm for Spotz). Unfortunately, I don’t have access to any drawing software nor do I have a 3D printer. Any generous souls out there looking for a cool design project lol? I’ll let you ride it if you ever come to Miami :joy:

Do you happen to know how much this guy charges to get an adaptor like that in aluminum?

58 and 70mm are really close.
You might have to drill a third hole in your fuselage if they interfere (paper step) or reuse the front hole of the new mast above the front hole of the Spotz fuse if they are same diameter.
With a calliper measure your mast bottom slot dimensions and post them here with the screw diameters of both old and new mast. Then a “generous soul” might help you.

Unsure I would say less than 80usd. The best is to send him a mail.

Here are the dimensions for the adaptor.

  • Length and width at bottom of mast insert: 97mm x 10mm
  • Length and width at top of mast insert: 100mm x 13mm
  • Distance from front of insert to the mid-first hole: 14mm
  • Distance from back of insert to the mid-back hole: 14mm
  • Any asymmetrical aspects: the back has a bit of an angle, so the height of the back edge is 30mm, while it is 28mm at the front. (Front is on bottom side on photos)


The Spotz fuselage uses M6 bolts and are spaced 70mm apart while the LF mast uses M8 bolts and are spaced 58mm apart. The LF mast dimensions are the following:

Any generous soul willing to draw an adaptor will be blessed by the efoil gods for life guaranteed lol. Plus, if you ever come to Miami, I’ll take you out on my board! :wink:

What are the dimensions of the slot in the LF mast?

So from the front tip to the middle of the first screw, there is 30mm. Then, you have 58mm between the center of the first screw and second screw. Finally, there is 44mm between the middle of the second screw and the back tip. After measuring twice, it seems like the mast profile is 132mm long and not 124. However the width seems to be fairly constant (I’m measuring 14mm instead of the stated 13.5mm). The inner dimensions of the center slots are 43mm x 9mm (shaped like a stretch out oval).

do you have a 3D printer to test the adaptor?

I don’t personally have one but I know people who do so I’ll be able to print a test run!

Are those measures taken with a calliper ? If not, the trapezoidal section might have some play…

I’d do the adaptor like this:

It will mean you need to drill out one of the holes in the fuselage to 8mm and then do a second hole at 8mm so that bolts can pass through into the mast…

Ok so there will be only 2 long M8 screws going through the fuselage into the mast directly using the newly drilled fuselage holes. Will the adaptor be threaded as well? Will I get water into the mast from this protrusion going into the mast slot? I just bought a new mast so I could have a perfectly sealed bottom lol. That’s not a big deal tho I can make it removable like on the mast I currently have!

The protrusion going into the mast slot is there to stiffen up the connection. It completely eliminates any wiggle you’d find without it.
One of the existing holes will need to be drilled out and then another new hole will need to be made.
The holes won’t be threaded as the bolts need to wedge the adaptor between the fuselage and mast.
For an efoil I wouldn’t ever have a perfectly sealed bottom. I’d rather have it open so that every last drop of water will drain out…

I see! That could work! What length bolts would you recommend? If you have the drawing ready, let me know so I can ask around to have it printed! Thanks for contributing by the way! I really appreciate it :blush:

You’d need to measure it out with the fuselage in place, but I would guess that countersunk M8 60mm should do the trick.
I’ll drop you a PM shortly…

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I’m not sure if you have the same mast as me but the dimensions from my liquid force are different. Maybe you do not have the best tools to measure it? The mast width is 132.8mm and the hole spacing is 57mm. The thickest part of the mast is 14.6mm. Front hole is 31.5mm from the front edge.