Hi everyone, Kyle with Project Cedrus here. There are two entries on my blog which are relevant to this discussion, so I wanted to share.
1)
projectcedrus.com/cedrus-updates/adapter-shimming/Regarding mast/fuselage interface/fit, there's no one to blame. It can be manufacturing, simple wear and tear, even environmental. To be honest it hast not been an issue with Cedrus, at least as reported to me, and I am in personal communication with nearly every one of my clients. I was on a kite trip in Baja when I noticed my Lift wings were starting to feel a little loose on my mast, and I started to get really nervous that I was going to have to recall 200+ lift adapters from around the world at this point which would probably put me out of business

. I called Josh at the Foil Shop and he explained that all setups, even full OEM, can experience some "slop" at the connection. He recommended shimming with tape, and I've been good ever since. Only recently have other clients started coming forward, 1 in particular in Australia who was unhappy with the fit of his mast in Axis and Unifoil. I tried to help, but he was not happy with the need to shim. I respect his decision. I have another client in SoCal with 4 masts and I don't even know how many adapters and he's constantly sanding/grinding them to get a perfect fit. I get that some feel a $1,200-$1,300 mast should be a perfect fit every time, but I can tell you from a design/engineering/manufacturing standpoint, it's simply not possible without controlling the whole system and having much tighter tolerances/QC which is obviously going to increase cost. Most brands manufacture in Asia, at higher production rates, so variability is much higher than Cedrus. Many of my adapters are actually designed from CAD supplied directly from the brand, so in theory they should fit exactly the same. But in some cases, they don't... which is obvious evidence that OEM CAD (design data) does not match their manufacturing.
2)
projectcedrus.com/cedrus-development/aero/Ventilation is even more complex and can be caused by a number of things. Of course mast profile is highly impactful, with shorter chord lengths/thicker masts being more prone. However there's a lot more than that, as structural performance can play a big role. A thin mast may ventilate under high torsional loads because the profile can twist causing flow separation. Surface finish is also critical, anything from a pinhole in paint to a damaged trailing edge can cause it. Water surface conditions matter, as small chop can trap air against the mast. In short, ventilation is a lot like a car skidding around a tight corner. Sure a Porsche 911 will perform better than a Land Rover, but all cars will skid when pushed to a limit. And that same Porsche that can turn at a higher speed may not be as fun to drive at slow speeds over rough (wavy) terrain. Much like the above, expecting there to be a perfect foil setup (mast, etc) that will never ventilate is a tall order.