I tried to write in FINS ,but it worked not.
I tried to work for Mv.Meurs a asymm.fin for Speed. How they do it now. But I saw on my board with Acrylbottum,
that the mixture of water and air goes in an angle of sometimes 40? behind the fin from leeward to the other side.
I tried it with a concave leewards,behind the thickest point of profile. That was better and faster. The concave
makes,that the water cannot go in such an angle to the other side. If you work on both sides concaves,it dont work.
So I worked left and right fins. I was surfing 3-4km,and was 20m in front.Retour slowlier. The half of 20m are 10m.
I was always the first,with 20m or 10m. So I worked the concaves diagonal on a 22cm fin on both sides always 11cm
long. That worked good tour and retour. Always with 10m in front. But what happend?The concave on leeward,so thought I, must do all the work. But the concave,who shall work on the way back,reduce on the vacuum side a little
of the vacuum. So ,not only 10m, no,20m tour and retour.The fins are 12mm thick, the nose is not sharp,she is rounded.Thomas made with such a fin 50 knots topspeed. Why cut out at the base. ? And what now for L?deritz.?
On a other day. Wolfgang

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Lessacher said..

. Why cut out at the base. ? And what now for L?deritz.?

wolfgang thanks for replying, to make a fin that does 50nts is unbelievable, i'm very much a back yarder without a lot of technical skills but the more I see other production fins the more I see concaves, its interesting you say symmetric concaves on both sides don't work as well as asymmetric
I'm still working on translating your message and slowly getting the idea, wolfgang I wasn't referring to the cutout at the base(back of fin), I was referring to the concave at the base on the leading(front of fin)

I got a homepage from a friend of my fins,please look:www.cameraid.com/Lessacher/tech.html
There can you something see. www.designlessacher.eu The concaves are on both sides always behind the thickest point of profil.
Diagonal is between the left and the right side. One point why I work cut out at the base is: Wide base is in 100% carbon very stiff. When I work the blade smaller,3-5cm, thats one way to get lift and flex. That works very good with rake 30? and Weedfins . Wolfgang

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Lessacher said..

I got a homepage from a friend of my fins,please look:www.cameraid.com/Lessacher/tech.html
There can you something see. www.designlessacher.eu

thanks for sending your home page, www.cameraid.com/Lessacher/tech.html in English, I have got a lot from www.designlessacher.eu, my fins are a different profile but need a tune up with some Lessacher technology , I pumped out a 33+on my 22cm with a 7.2 n/p rsr , felt the fin was way too big, I have 3 molds so ill lay some carbon fins up then put some concaves in, that way I still have the old fins to compare
i have been working with various cord thickness so now some concaves should sort them out ,wolfgang thanks for your help