the X-profile split is something I´ve been working on for about two years now.
In the beginning there was the question how to built a split-system without milling a groove into the face-sides of the board what has always been a pain for me. After some attempts with asymmetric elements and grooves I decided to add a 3D printed profile element which contains grooves on both sides and called it X-profile (actually it´s more an H, but H-profile sounds a bit lame
). This gave me some benefits: - only contour-milling from above
- All damageable laminate edges of the split are inside the profile and well protected
- possibility to correct split tolerances with the profile without grinding/cutting operations on the board itself, if the X-profile doesn´t fit I´m just gonna correct it in CAD and print a new one
- forces are induced directly into the top and bottom laminates because they directly touch the X-profile
However, in the beginning all prototypes broke into pieces. Mainly because of limited layer-adhesion 3D-printed plastic just isnt´t as stable as casted plastics for example. Printing the profiles in upright direction was much better. And after oversizing the profile out of the top side of the board it just worked. Because of very good layer-adhesion and toughness I´m using polyamide (Nylon) for this at the moment. As the pictures show I´m printing all the edge-elements with ABS but it will also work for example with casted and cotton reinforced epoxy-edges. And if you are able to work precisely with an outline jig it will work without CNC.
To keep this short: I´m using a small press with hydraulic car lifters, lamination process is quite easy: A printed split-dummy is mounted on a dibond-plate 800x500mm with nylon-screws and nuts (they don´t kill your CNC later if you go through them accidently). This is my lamination base. Look at the pictures.
Known issues:
- A too big step from the bottom to the inner face will lead to delamination because of shear forces, see last picture. I´m trying to fix this in the next board by changing the geometry of the cross section from rectangular to conical, this will lead to better stability anyway
- it´s always some extra work to get the whole thing watertight, otherwise there are some funny fountains on top
- As I´m only building one or two boards a year at the moment I was not willing to sacrify boards for breakload-testing. Only thing I can say is that I´m still alive and so it seems to be enough for a rider with 75kg and average kite-skills
So long, Greets
Micha
