After seeing Bert’s boards I think that I came away with a better
understanding of whats going on with his boards and why they way
outperform surftechs. I did not ask Bert if any of my guesses
were correct, and its completely possible that I am completely wrong so
take from this long ramble whatever you think has merit and forget the
rest. I have come to the conclusion that building technique is
much less important than the philosophy that goes into building the
board. I think that this is why Bert once said that its easier
for him to train somebody from scratch than it is to take an
experienced builder get him up to speed. This is why Harbor can
make a great urethane board, but the shape does not transfer to
composite style building. When Bert says that his boards flex he
is not talking microscopic flex. I tried moving the nose of one
of his boards with my bare hands and had little problem. My son
(55 lbs) was able to stand on one of his boards and flex it to the
ground. I told Bert that I wasn’t sure that my boards flexed that
much so how could he be sure that his board actually flexed differently
because of the diagonal timbers amplifying the board’s flex pattern and
he looked at me like I smoked crack. His reply was that a lot of
things happen when you make the board thinner. When you see his
boards it is obvious that a lot of structure has been removed (light
glass, super thin rails, concaved deck). All these things help to
remove strength (rigidity) and encourages bending. A standard
looking board that is built in a vac bag system is too strong.
When a board flexes as much as Bert’s it has to store energy or it
would be a lifeless slug (thing bogey boards). For example, a
concaved board greatly increases the boards ability to bend along its
center axis. However, there is very little structure to store
energy when the board bends this way (think about the way we’ev all
been laying our balsa). Bert uses diagonal timbers to help the
board store energy when it flexes and then quickly return to shape (see
daddio’s picture). I have been spending a lot of energy trying to
get my rails looking perfect. I’ve been CA gluing the ends
together so they have tight joints with the longest pieces of wood
possible (in effect making them 1 long piece of balsa). My goal
what to make the strongest possible rail. Bert’s looks to be the
complete opposite. He used short pieces (1 - 2.5 feet) with
little gaps between the joins. I think that his would make the
rails more flexible. Since Bert’s boards are able to move you need to
change the shape in order to accentuate the movement. A
traditional board has very little flex movement and their shape
reflects this (narrow and comparatively boxy rails). Imagine
trying to bend a metal coat hanger. Put your fingers so they are
very close together and try to bend the hanger. Now put your
fingers 8-10 inches apart and try to bend the hanger. Its a lot
easier! I think this is one of the reasons Bert’s boards are wide
(the wider board encourages flex) compared to the traditional
board. The second reason is because we all need a little
flotation and the wide board gives us the foam we lost in the
concave. Once the board became wide the rails needed to become
skinny so that you could sink the rails (and it turn load up the
flex). Finally, the 1:1 resin ratio has more to do that just make
the board light. On my workbench I had some dried puddles of
resin and some dried 1:1 ratio glass. When I tried to bend the
resin only it always broke but the glass was able to move all
day. I think that a high resin content would encourage
brittleness in the board (which is the opposite of flex). I think
the answer to the question of where flex is important is: evenly along
the length of the board (this is why you can jump on the board) and in
the width of the last third of the board (this is where the twang comes
from). Equally important to flex is the board quickly returning
to shape. Yes, Bert does have some specialized construction
techniques that make his boards outstanding but they are not necessary
to make a really nice board. What I think really needs to be
experimented with is different glass schedules to see how little you
can use until the implode (Bert has said that his best boards only last
a year or two). This is what I’m going to start working on.
?