One we discussed foam selection, and helped to delineate the
differences between Polyurethane foam and EPS foam, as well as the differences
between Block-Cut EPS and Superfused (molded) EPS. In Part Two we’ll discuss
the various densities (sometimes referred to as “weight”) available for each
foam type. As surfboard design and surfing styles have developed, US Blanks has engineered different foam
densities to accommodate each need.
for a given space (the blank’s dimensions).
Clark and Hobie Alter began producing polyurethane foam surfboard blanks in the
mid 50s, they designed their foam for be a similar weight to the wood logs that
surfers were accustomed to riding. The heavy foam boards were very sturdy and
stable, but difficult to maneuver. As surfer’s skills developed, Clark provided lighter foam, which surfers
were able to turn more easily. This trend towards lighter-weight foam continued
up until the late 90s, where Kelly Slater, et al., ushered in very thin,
narrow, highly-rockered shortboards. These boards allowed for the
emergence of aerials, fin-releases, and 360s, but also saw a much greater
incidence of board breakage, due partially to the lighter foam, but also the
higher impact maneuvers. Since the late 90s, foam density trends have diverged
into a wide range of needs. The
current “ride anything” ethos requires that shortboards are available in either
lightweight or Tow-weight, longboards to be built for high-performance or as
throwback logs, as well as any manner of single-fin, kneeboard, asym, funboard,
SUP, Gun, and even multi-foam constructions (PU & EPS).
with any aspect of board building, what you gain in one area, you will lose in
another. Lighter weight foam will offer more maneuverability, but
inherently less strength. The loss of strength can be mitigated by other
construction materials like stronger stringers, carbon fiber, thicker glassing,
and stronger resin, etc.
exact right foam for any build, US Blanks offers (6) density options for PU
blanks, as well as (2) density options for EPS blanks. For PU, the weight is
identified by the color on the nose of the blank. Due to a few variables in the
manufacturing process (mold compaction, skin-to-core ratio), exact PCF (pounds
per cubic foot) for PU foam is not given. Rather, a stock weight (Blue) is
designated and then all other densities are referenced from that weight, as a
percentage of either more dense or less dense.
Lightest to Heaviest:
Weight) is approximately 12% to 13% lighter than Blue. This would
be most commonly used for elite level professional shortboards.
approximately 6% to 7% lighter than Blue. This is a common selection for a
surfer who wants more performance from their shortboard, midlength, or longboard.
for comparison. Blue is the perfect combination of weight to strength ratio;
light enough to maneuver, yet strong enough to provide extended use.
approximately 9% to 10% heavier than Blue. This is a common selection for
classic longboard and funboard designs.
(Classic Weight) is approximately 30% to 32% heavier than Blue. This is a
common selection for traditional log-style longboards.
approximately 205% heavier than Blue. This is almost exclusively used in
shortboards designed for tow-in surfing.
(both Block-Cut and Superfused) are available in two densities; 1.5 pcf & 2.0 pcf.