I’m going to address a few comments that have been made, and then any additional analysis re: this topic will be dealt with on my blog.
@Matt your interpretation of my graph is correct. The line I drew is constant drag FORCE of the mast. Lines parallel and to the left are less draggy, and to the right is more draggy. It is based on a DOE (design of experiment) that I had conducted by Tom Speer, the lead designer for Oracle Racing’s hydrofoils and airfoil (they were the first to launch a solid wing sail). I posted the details of my work with him over 5 years ago here: Aero - Project Cedrus In short, we looked at drag and separation angle (which is indirectly related to ventilation characteristics) for a matrix of masts 16-20mm and 100-140mm chord length. Note I did not go below 16mm for a reason: stiffness falls off a cliff. A 16mm mast is 50% stiffer than a 14mm mast. No amount of modulus can make up for that. Anyway Tom’s CFD incorporates non-linearities like piercing drag, parasitic drag, lift-induced drag… it’s all a lot more complicated than the equation that @NoLimitz posted. I have spent 20 years refining my skills in Finite Element Analysis (FEA) and spent $40,000 in software. I won’t pretend to be capable of teaching myself the same tools for CFD, nor can I afford them at this point, which is why I paid Tom. The analysis confirmed that drag is affected more by wetted area than thickness. Which kind of makes sense, because if you add 10mm of cord length to a 100mm mast, that adds more area on both sides of the mast. My statement about increasing chord length 10% causing drag to go up 20% was based on this analysis. Adding 10% in thickness only caused drag to go up 8%, because the wetted area did not change… you just slightly increased the Cd, which as @NoLimitz points out, is the smallest term in the whole equation! One assumption I am making in my statement is that the shape/profile is relatively constant. Obviously there are infinite ways to shape a streamlined body, and Tom designed one for me that works well at the speeds and Reynolds number that our foils operate at. But there could be some subtle differences in shape that make a longer chord length mast equivalent (or even less than) in drag to a similar mast with a shorter chord length, but again the trend is still valid. That miraculously slippery mast could still be faster with a shorter chord length.
@NoLimitz in my 7 years designing and offering masts, I never said mast profile thickness doesn’t impact drag. I simply said it doesn’t have as big of an impact as chord length (wetted area). Those are two very different statements. A direct quote from your V2 product launch: “Now, some folks on the internet talk about chord having a bigger impact on drag than thickness and that is simply not true.” Considering my blog post on this very topic, that statement felt like a direct attack on me and Project Cedrus. Further compounded by the fact that Steve’s analysis is completely wrong, I felt inclined to finally address this callout. As I’ve leaked, Evolution Cedrus is 16mm thick-obviously I know there are benefits to a thinner mast. I am simply trying to educate the community on the fluid dynamics, and you are hampering that effort by publicly criticizing my work on your website. I don’t know what the shape was of your Navy surface piercing struts, and if they were anything but a streamlined body, using frontal area could be applicable. The two links I posted previously show the use of frontal area as the reference area in the case of sphere moving through the air. But if we are analyzing a streamlined body flowing through fluid, with an order of magnitude longer chord length than thickness, the majority of the drag comes from skin friction and therefore wetted area will be used for the reference area. You can “continue to stand by your statement” but I suggest you actually talk to professionals because they will all agree that using frontal area is incorrect.
Finally, I have said nothing about ventilation in my posts. All of my statements have been related to drag, and only drag. I know all about ventilation. I wrote about ventilation in that same blog posting above back in 2018. I have another post on it here: https://projectcedrus.com/cedrus-development/notes-on-ventilation/ Yes my 6 year old Project Cedrus design suffers from ventilation at higher speeds with modern foils. I’m honest and open about that. It was a gamble I took making the stiffest mast in the industry (even to this day!), and honestly I have no regrets. But I have focused heavily on addressing ventilation with Evolution Cedrus, and can assure you that it will feature the most ventilation-proof design concept the industry has ever seen.
In closing, I didn’t mean to hijack this post and only chimed in because my name was used and people seem to be questioning my methods, assumptions, and analyses. I hope I’ve cleared them up, and if I haven’t, you can head to my blog for more info, or contact me through my site. Thanks to those who have supported me on this journey, it really means a lot.