Does new ownership imply there is now one prior owner with a lot more money and a lot more time to spend on foiling? I.e. Will the mast part of the business continue as a passion project under another name?
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Most everyone has hobbies. Prior owner being an active foiler, they may have been willing to carve out a piece of the business to support the hobby. All sorts of business and personal reasons to do that. If the new owners don’t care about foiling, there’s simply no reason to keep that side of the business going.
I think that leaves Jacko and One Ocean Sports as the last “passion project” mast on the market (that I know of).
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Can anyone share the economics of a passion project mast or foil? @Maarten88 , KDW and a few others doing very small run batches. I’ve got a few one-off mast protos. Cost doesn’t seem insanely high
That’s a good question, I’d be interested in knowing the same.
I’m not in this hobby for the economics, I’m doing this because I find it interesting and I’m stubborn enough to think that I can make something better than what I can buy.
That said, the economics for me building my own equipment work out about equal to buying high end gear, not counting the time I put in. A good mast has very poor economics, because it uses a lot of expensive UHM carbon. For a mast, my material costs are:
- Mold: around 600 euro
- UHM carbon, epoxy and vacuum consumables per mast: around 650 euro
My molds are very inexpensive compared to professional shops, because I’m not using aluminium or steel molds. My mast mold is made from HPL (high pressure laminate). I think it would last about 25 products. Making a mold for a mast / fuselage costs me some 2 weeks / 80 hours, half of that is CNC time.
Making a mast/fuse combo (I use a zero connection design) costs me some 4 working days / 32 hours, for me these are one-off projects so pretty inefficient. Because I use vacuum infusion, my products usually come out pinhole-free and my post processing time is very good.
These costs are incremental: I purchased and made a lot of tools in the past, such as a large vacuum chamber and pump for infusion, aluminium inserts for my connection system and many other smaller things. I have access to a CNC machine at my makerspace. You’d have to amortize that as well to know the real economics.
My mast is not light btw: UHM (pitch based) carbon has higher specific weight compared to normal (PAN based) carbon and I’m building the mast fully solid. It’s heavy but I prioritize stiffness. I do not use prepreg like some brands do, and I know even higher spec carbon exists, but I do not have access to it.
Foil wings are a much better business case: a mold costs me around 250 euro, building a wing is around 125 in material cost, I build foils from normal (not UHM/HM) carbon and the mold is from infused MDF.
A stabilizer probably has the best economics.
Sometimes a design is not as good as I had hoped and I have to throw it out and start all over. Hopefully I learn from it. But those projects have the worst economics 
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Hi,
Thanks for your post. We at F4 run similar optimization studies and have similar findings for mast profiles. Typically we are solving for Ixx to optimize surface area and stiffness, however managed good torsionally stiff ~11.3mm thick masts with 100mm chord that are in production now. They make a huge difference in downwind.
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11.3mm with 100mm chord sounds stunning. Do you have a link to that mast?
Is under the incorrect category and sold out at the moment, but more stock is on its way - GP Plate mast TE Downwind – F4 Foils
Check out episode #44 on the x-foils podcast!
Br,
Chris
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Thanks Chris! What foil would you pair with that mast for your best surfy downwind experience?
F4 Orca 685 with xs135 stabilizer, it’s a game changer
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That is impressively thin!
So like me, you are optimizing hydrodynamic properties against bending stiffness Ixx, and calculated a 11.3% t/c section. That is similar to kite race masts like Chubanga and Levitaz. Can you share what hydrodynamic properties it has that you can not get out of a thicker (say 12.5% t/c like above) section? My optimizer won’t go below 12% even with extremely narrow high speed settings, so I wonder what I am missing.
Hi,
I don’t think you are missing anything at all and super impressed with your analysis. Structure and hydrodynamic properties are interrelated. The only difference is that we are optimizing the t/c based on the inertial properties of the sections knowing in advance the stiffness we can get with the materials we have access to. Other masts we are making have much shorter chords, but thicker sections relatively to get the stiffness we want, if that makes sense.
Br,
Chris
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This will likely be buried in a few days in the Cedrus Aluminium thread and I thought it would be interesting to have it here.
What to do with the data, your weight, foil, program of use I have no clue. But it’s nice data.
I agree with him mostly:
- For a given design more stiffness always rides better
- Torsional stiffness is more important than bending stiffness in riding
- Mast design is a balance of stiffness against hydrodynamic properties: a thinner/narrower mast is more efficient but results in lower stiffness
In the computer I’m just calculating theoretical bending stiffness but really this is a proxy for torsional stiffness too. In my mast builds I’m putting more than half the carbon layers in 45 degrees to make it stiff in torsion. It’s a lot of work because I can’t buy UHM carbon as 45 degree biax fabric. I suspect professional manufacturers also have this challenge and did not do the work or, worse, use plain carbon biax, which is why those masts score poorly in torsion.
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Please don’t take offense to this, but when I commented that there’s a lot of misinformation being spread in forums, this is an example of what I was referring to.
Bending stiffness, which is increased through the second area moment (Ixx), is not a “proxy” for torsional rigidly, which is calculated using the polar moment of inertia (J). Thickness, chord length, and shear modulus of the material affect these two variables quite differently. So optimizing for bending stiffness and simply aligning half your fibers at 45 degrees is not a good way to guarantee torsional stiffness. To correct an earlier claim, bending stiffness is impacted by thickness^3 (not ^4).
Assuming professional manufactures “did not do the work” is another bad assumption because I can tell you we have. You cannot optimized a composite structure with geometric and material non-linearities using simple scripting tools. We use Abaqus FEA to optimize ply angles and locations to maximize both Ixx and J. When working with anisotropic materials like unidirectional composites, there’s no other way to do it. The process you are using only works for isotropic materials like aluminum. Here’s a case study that I was not involved in, but I am providing as a good example of the tools used to optimize composite structures: https://www.aerospacemanufacturinganddesign.com/article/amd-1209-light-strong-aircraft-dassault-abaqus-isight/
Manufacturing at volume does give us access to materials that you can’t get as a DIY. I wouldn’t assume anything about how other brands are making their masts. Some of us have been doing this type of work for 20 years+
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That link is another cool read. Keep them coming!
I said size, not thickness. When I’m optimizing and comparing sections I always scale the whole section (not just thickness, but also chord) so the hydrodynamic properties do not change, just the reynolds nr. That makes the difference between your ^3 and my ^4. We are both correct.
I’ll add a polar moment of inertia calculation to my optimizer and try using that to optimize against a combination of Ixx and J, you are right that would be more correct. I suspect in practice the result will be almost the same. Thinking about it, it might lead to thinner t/c optimums, and that is the thing I was missing before.
I also know assuming isotropic material is theoretically incorrect, but I think its still valuable as a first approximation, I’m not treating it as an absolute truth. And I need to calculate it quickly, as the computer does this tens of thousands of times in a single optimization run.
Sorry you thought I was implying you, this was aimed at the carbon masts in your chart that are only very stiff in bending but not in torsion. Yours is indeed well balanced so clearly you did the work. Thank you for publishing it!
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I’ve heard of one company that was weaving their own carbon to get the blends they wanted
I looked into this and I think I understand it a bit better now. Just looking at section shape and ignoring an-isotropic material properties and construction at first, J (polar moment of inertia) simply equals Ixx + Iyy. For a typical mast section, Iyy (bending inertia in the forward/backward direction) is almost 2 orders of magnitude higher than Ixx (sideways bending), so the value for J is always slightly higher than Iyy. Iyy is the proxy I should have used.
Ignoring construction, this means chord length is the dominant factor attributing to torsion stiffness. It makes sense, but I did not really understand this simple relation before.
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Hi,
We make ± 45 using two plies on uni on top of each other at 90 deg then cut at 45. Prepreg sticks together or you can use a spray adhesive.
Was trying to say that we have test data for all the masts, so can use that to scale the dimensions based on second moments of inertia and get results that compare well. There is always tuning, since torsional stiffness is at the expense of bending or vice versa.
Br,
Chris
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