Foam core
The core was made from foam intended for thermal insolation of hot-water pipes in buildings. They were available in multiple diameters and wall thicknesses. And of course the are round.Single problem that remained was that they didn't get thiner to one end, but we wanted a conical shape for the horn.
After some experimenting with the material (C) we decided to cut a dent along the axis an reglue the faces together in order to reduce the diameter (B). We went zigzag to increase the surface as you can see in the photos above and merged three sections of decreasing diameter to the final horn.
Next step: we cut two helical grooves about halfway through the hull (A). This is the earlier discussed resemblance to the narwhal's horn. (Ok, we didn't work in that order. The widest, longest part (A) was already cut and laminated, when we added the two shorter, thinner ones (B))
Lamiation
Don't expect some fancy high tech. We only hat limited experience and tools. So no molds, vacuum infusion or similar shenanigans.
We used a 160g/cm^2 twill fabric as a base layer, cut to cover the whole surface.
Then we added a 4cm wide strip of 250g/cm^2 roving tape that had sewed edges over each of the cut out grooves and forced them into the groove winding a thread around, which was attached to either ends of the construction. This way the fabric was forced to follow the topology of the underlying foam core.
And after adding the second strip and thread.
In the last step we impregnated the whole thing with epoxy resin until the fabric was fully transparent and one could see the core again.
Of course it would have been more optimal to lay the fabric wet on wet, but with this rather complex geometry this wasn't possible (tested that. won't try that again).
After the structure had cured, we added the upper half, laminated it and reinforced the junction.
Then we added a 4cm wide strip of 250g/cm^2 roving tape that had sewed edges over each of the cut out grooves and forced them into the groove winding a thread around, which was attached to either ends of the construction. This way the fabric was forced to follow the topology of the underlying foam core.
And after adding the second strip and thread.
In the last step we impregnated the whole thing with epoxy resin until the fabric was fully transparent and one could see the core again.
Of course it would have been more optimal to lay the fabric wet on wet, but with this rather complex geometry this wasn't possible (tested that. won't try that again).
We could put up a time-lapse video of that process. Leave a comment if interested.
Richtig gut!
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