Annular 3D printed windsurf fin that works

Most think it's not possible to 3D print a windsurf fin due to the extreme loads.  However, 3D prints are almost indestructible if held in compression so uploading a few windsurf fin designs that show how to print a fin that can withstand these forces.  This one is an annular fin that is designed for ultra light wind…sort of like a Formula fin but much less draft.  

Hopefully the design shows how to keep the entire print in compression.  For the annular section I did one layer of glass over the whole thing.  This was mainly to stop bits of trailing edge falling off.

Note: This actual print won't be of much use to anyone as it requires the exact size of circular steel as used here.  I used an old gas bottle and then printed the design around that.   So most likely you would need to design and print your own annular section around whatever circular steel you can find.

The key is having a transfer plate that the tuttle bolt connectors transfer the load down the vertical bolts to the fin.  Both the tuttle bolts (holding the fin to board) and the vertical bolts keep the entire print in compression. 

Have included normal and deep tuttle.  

Don't have a video of this one in action but here is the previous version (differences are 20 dia shown in video but 25cm dia here, not glassed (so easy to break bits off trailing edge) and no triple layer steel on annular to strut interface)

Update: May 25, 2023.   Took it for its first fin today.  Was surprised it was no where near as good as its 20cm predecessor.  The 20cm had a symmetric airfoil where as this 25cm used a cambered airfoil.       Need to remake this size with the symmetrical foil.  Hopefully got some good video so will post here eventually.