Monday, May 16, 2011

Conceptual Surfboard Design

Conceptual Surfboard Design.

Using a thermoformed Hexaflex matrix as the core material, it is possible to make an extremely strong, yet lightweight, surfboard. The core matrix is an open hexagonal cell based design which has the benefit of a high surface area for secure bonding of finished skins combined with the ability to be easily vented. The core matrix is a monocoque construction which allows the stresses that the board is subjected to be instantly absorbed throughout the board. This allows for a more responsive flexible board.

Vacuum Forming mold

A vacuum forming mold made of ¾” plywood approximate size of 8’-0”x 2’-6” which has a multiple array of approx 3½” hexagonal, cross sectioned plugs glued to its surface.
A mold of the bottom rocker surface is slipped over the hexagonal plugs to provide the bottom surface of the board.
The height of the wooden plugs are chosen to approximate the given curvature of the upper surface of the surfboard.
The end surfaces of the protruding hexagonal plugs are shaped and faired by hand.
A 40 thou thick (0.040”) plastic sheet (polypropylene?) is vacuum molded to form a complete surfboard blank.
The blank then has rails, stringers and outer skins attached by vacuum forming, resin infusion or standard lay-up techniques.

Cross section of matrix panel

Double stringer placement.

The Handling Characteristics.
The matrix can be tuned  by selectively separating  cell walls within the matrix to varying depths which will allow control of the degrees of flexure in prescribed  board areas.

This shows the bottom side architecture of a thermoformed hexaflex matrix panel.
  This shows the upper side of the thermoformed panel of the Hexaflex matrix. Note the venting channels running from top to bottom. The hexagons are hollow which add to the final buoyancy and handling. Stringers can be located within the venting channels depending on which part of the matrix you center the board profile.

This concept will be applicable to double skinned composite boat hulls.

Another method of  using the hexaflex matrix in the surfboard was suggested by Oneula:

"I can see vacuuming a sheet of this stuff between two 1" sheets of blue XPS on a rocker table
then cut out the outline along the standard inset perimeter rail outilne
then glue on using the same rocker table a solid rail band of either more blue dow xps or precision board or corecell
then final shape the board by hand.
with the 1" top and bottom xps sheets you can shape in bottom contours and thin out the profile as needed
as the thickness of the xps is reduced it should indice more flex in that area (tail/nose)
kind of like a reverse design of a surflight blank or a solomon-like blank with a plastic versus xps core 
just an idea"

I replied with;
"where do you get the stuff from and how thick is it?"

This is still a conceptual design so as yet there is no supply.

However by using the technique that you propose:

"a (flat) sheet of this stuff between two 1" sheets of blue XPS"  you may well have opened up the supply lines as this is a much simpler system than the one I was proposing.

The geometry of Hexaflex allows it to be bent into any multiple curvature.

There is a material called Delrin2 that has been developed by Dupont having the properties of sprung steel yet is lightweight. It should be perfect even though the price is high at $70 per sq ft.

So the final depths (thicknesses)  available would be in a range of 1/2" up to 1-1/2" with variable sizes of hexagons.

Props to you Bro'


This is a  more satisfactory solution as it gives the power back to the shapers within whom the true skill of board design resides.