I am trying to draw a fin for my final year project, but I could not fully understand the technical drawing explanations that I marked with red markings.
especially R1.281 DEFINES TANGENCY OF R1.312 WITH FIN SURFACE, I couldn't understand the part.
My goal is to make a "bubble fin holder" like in the last picture.
I'm also wondering how we can draw this part of fin .
high resolution image is here
https://i.imgur.com/OmEKV7J.jpeg