Currently in a masters level Composites Design class at a local university.
I have chosen to design a two-piece collapsible surfboard for travel purposes.
I have seen the Pope version, and have drooled over Schwuz’s. Trying to keep
the thing 2-piece, which will limit the board length to 6 feet. Also trying to
make it functional for me… at 190lbs. So dimensions will be in the range of
6’ x 19.5" x 2.5". Once complete it must fit in a container (i.e.
suitcase) with dimensions L+W+H of no more than 62".
My design will not employ any carbon tubes. Currently, I plan on using two
fasteners located along the boards neutral axis near the rails. These fasteners
will create a friction joint between two facing plates butted against each
other. This friction joint will restrict any shear movement of the board.
Bending along the stringer of the board will create a compressive force on the
top or bottom skin, and a tensile force in the fasteners.
My design goal is to create a joint design that efficiently transfers the loads
across the joint and into the skins, while minimizing the effect of the joint on overall board performance.
I am having some trouble with approximating the maximum forces that will be
encountered in surf of up 8 ft. I reason that the worst case scenario would
probably be a top to bottom wave breaking directly on the joint, with the board
only supported by the nose and tail. This situation is highly unlikely. It is
more practical to assume the board is supported in the middle each section.
Thus the moment arm is one-half of the section, or one-fourth of the board. By taking the amount of water, and its
velocity (acceleration?), one can derive the total force or pressure exerted
per unit area. Worst case scenario would be this entire force being transferred
entirely through the joint.
Anyone have any input here? I need to establish a maximum, so that I can
determine the cross-sectional area (diameter) of fastener needed.From there I can figure out the how much laminate i need to transfer out to the skins.