I got back from AWSI a couple weeks ago, but I am still processing so many observations and thoughts. I’ve also been really busy on a number of new products, in addition to fulfilling orders for masts and adapters, that I’ve had little time for blog updates even though there’s so much I want to discuss.
First off, at AWSI I was amazed to see how much the industry has changed since I delivered Launch Customer masts in 2018, which was also coincidentally my last visit to AWSI. Back then, it was all kite foiling, Kanaha Shapes pocket boards were the rage, and Moses 633 were the foil wings to have. I think I remember seeing prototype slingwings at the time, and most participants were teasing the nascent sport. Now, there are so many new foil brands, and I bet even the dock start crowd and market is bigger than kite. As a result, wings are massive, some over 1.3m (longer than my longest mast), and boards are getting monstrous too. It is important to note that board size has just as big of an impact on mast loads as wingspan, something foil designers I talked to at the show failed to acknowledge. Masts are getting stiffer, but they are also getting heavier and more expensive, due to higher modulus materials. Interestingly, brands appear to be trading thickness for chord length, which has an equally significant impact on drag… but that’s another post.
I want to take a moment to sympathize with the entire industry when I say that athletes are pushing this sport faster and further than we can design and manufacture, especially in a post-covid world. Warranties are typically in place to protect customers from equipment failures due to quality issues, however the types of failures I am seeing these days are simply due to usage loads exceeding design capability of the equipment. On one hand it’s not our fault that a customer breaks a mast from 2020 using a new set of foil foil wings and high volume board that didn’t even exist back then. On the other hand, brands should not introduce new wings and boards that are not capable of withstanding the forces of aggressive pumping, big boosts, or extreme wind conditions. It’s a difficult balance, because we want the sport to progress too, but we also don’t want to go out of business. I beg all of my clients and those that are not my clients to understand that we are all trying our best to deliver equipment to you that allows you to progress and have fun. This sport is still so new, we are all learning, and limits are constantly being pushed. I am very proud to say that since 2018, with over hundreds of masts sold, I have not had a single structural failure of a mast. But some of these new wings scare me a bit, and at this rate, it is only a matter of time before someone exceeds the design capability of Project Cedrus. So before this happens, I want to discuss the importance of hardware and help mitigate some of the risk I am taking by making a universal foil mast.
First off, M6 hardware is no longer adequate (arguably it never was) for mast/fuselage connections. As far as I know, there have been only 3 lost foils among Project Cedrus clients (<1% failure rate), and all 3 were a result of M6 hardware failures. The failure mode is the same: The aft screw fails in tension, and then the remaining screws do not have enough strength to manage the resulting bending loads. To reiterate: the aft screw is failing in tension, NOT SHEAR. It is not possible to have shear stress in these screws of tuttle-like interfaces at most mast/fuse connections. An M6 has approximately 50% less strength in tension than an M8 screw. More importantly, an M8 has 2.4x more strength in bending than an M6 screw, which is usually how the forward screws fail once the aft has broken. Also screws typically loosen before they break, and when they are loose, they are subject to bending stress. M8 hardware not only gives much higher initial strength, but the failure mode is more ductile which usually gives you the opportunity to stop foiling before your fuselage has sunk to the bottom of the lake/river/ocean.
This 1st Gen adapter (2020) failed when the head popped off (tension failure) the aft M6 screw. The immense amount of lift from the front wing then causes the entire fuselage to pivot around the remaining fasteners, which will either tear out or fail in bending. Adapters have since been redesigned with more meat at the M8 screw heads, in an attempt to prevent fracture of the adapter itself, but the M6 screws will still fail.
Helicoils do not add strength to M6 connections, because it’s usually the hardware itself that’s critical. Helicoils do improve wear and corrosion resistance, but do not solve the fundamental problem of inadequate screw strength. As far as I know, Project Cedrus was the first foil to employ stainless helicoils, and I am well aware of their function, benefits, and limitations. I realize some brands have employed helicoils in their M6 connections, and I have started adding them to remaining M6 adapters, but the do very little to increase overall strength of the connection.
As shown in this photo, the aft screw clearly failed in tension, with the remaining half still engaged in the threads. Unfortunately, the remaining screws did not have enough strength to prevent the foil from detaching from the adapter.
Use Project Cedrus M6 adapters at your own risk. I will not and cannot afford to compensate for your lost foil due to M6 hardware failures. I realize again that there is a risk to making a universal hydrofoil mast that I must accept. If you legitimately break an adapter, or the mast itself, I will obviously make it right. I actually wrote about my first (and only) true adapter failure here: https://projectcedrus.com/cedrus-development/first-failure-lessons-learned/ I recently experienced a very angry client who is adamant that his lost foil was my fault, and it has been an emotionally and financially taxing experience despite the photos clearly matching those available on forums, facebook, and instagram. Most major foil brands have transitioned away from M6 hardware for obvious reasons (SAB, Takuma). While I appreciate brands maintaining their fuselage connections as long as possible as a form of goodwill to their customers, in the case of M6 I believe the risk exceeds the reward. I am not writing this to trash other brands or designs, I am simply offering engineering/technical advice based on data and my 6 years of studying every foil connection on the market. Feel free to ignore my technical advice, but please do not question my intensions or accuse me of trashing other brands. I see all brands as partners, not competitors, and simply want to help them sell more wings and give my clients more freedom and performance.
Replace your hardware frequently. Foil screws are subject to repeated stresses well below strength values, however this can still induce fatigue failures. Mowing the lawn kite foiling is very different from pumping for hours in the surf. All hardware, either M6 or M8, OEM or Project Cedrus, needs to be evaluated and replaced whenever the thread pitch appears to have changed, the shank bent, or it looks corroded. Hardware is so cheap, it is best practice to just replace frequently to reduce risk. You can buy all Cedrus hardware here: https://www.mcmaster.com/screws/socket-head-screws/thread-size~m8/material~stainless-steel/socket-head-profile~low/ and as always email me if you need help.
Read the Owner’s Info section to properly care for and assemble your foil. I know everyone would prefer to leave their setup assembled in their van or on their porch, but there are some tradeoffs to a universal foil mast. I don’t love pumping my tires, lubing my chain, or checking shock pressures when I go mountain biking, but the bike performs better when I do. Tension your adapter bolts before use, dis-assemble and rinse frequently, and let me know if you have any issues that are not resolved when following instructions here: https://projectcedrus.com/owners-info/
I am working on a major standardization of Project Cedrus adapter design and hardware lengths. This is a big effort, but it is the right thing for the business and it is the right thing for clients. Adapter designs have been under so much time pressure, with new interfaces coming out from big brands monthly, I’m often rushed in the design process and don’t take the neccassary time to ensure hardware commonality. As a result, I have 4 different screw lengths from McMaster-Carr, which adds to my costs and your confusion. Because the screws are critical to the adapter strength, I am designing around a customer fastener with 50% more strength and better corrosion resistance than standard A4-70 hardware. Stay tuned for details!
Thanks for reading, Kyle
UPDATE: USE CEDRUS-SUPPLIED ADAPTER HARDWARE ONLY, DO NOT USE TITANIUM FASTENERS.
I have been getting a lot of inquiries about titanium hardware, and recently heard from a client who lost his foil due to failed titanium hardware. It is a common misconception that Titanium is a superior material for hardware; it’s not. Stainless Steel is stronger than the most common form of Titanium alloys. While Titanium may have a higher strength/weight ratio, this property is not important for role of hardware on your foil which contributes a tiny amount to your overall foil weight and performs the most important job of keeping things connected. As I’ve shared many times, McMaster-Carr provides a great learning opportunity to explore hardware. Typical Cedrus hardware is A2 or A4-70 grade stainless steel (700MPa min tensile strength). New adapter hardware is actually A4-80, which has a 50% higher yield strength than A2-70. This $4 Titanium screw with a 350MPa tensile strength isn’t nearly as strong as this $0.50 stainless screw, so there’s absolutely no reason to use it. Furthermore, most titanium hardware coming from overseas has unknown mechanical properties and quality. Use only A2/A4-70-80 Stainless Steel hardware with your foil.