CW,

Actually the FRs have been around a lot longer than 60 years. It was not new
technology during WWII when it was used to build DeHaviland Mosquitos and Elco
PT boats. I believe it was used to assemble the spars of Ranger.

We started converting most of our process from Resorcinol base to epoxy in 1964.
My father (gone many years now) and I were both engineers by education, so we
did a great deal of testing and evaluation. The right epoxy would allow us to
laminate a mast that we could bend without fear of shearing the glue joint and
we started building controlable bend spars for racing just in time to have that
market wiped out by the aluminum extrusion that had all the flexibility of a
telephone pole.

A great deal of the driver was a series of failures of older spars because the
Weldwood FR that everyone had been using was too brittle in when cured. Even
the joints done with cotton layer (strips of old bed sheet saturated and laid in
the joint to both make it more flexible and control the glue thickness) were
still prone to this failure. The hardness of the FR makes it shear way from the
lamination base during high flexural loads.

Epoxy is not epoxy is not epoxy. My father worked with a forgotten supplier to
get a material that was good for laminating, effectively staturated and had a Me
(modulus of elasticity) very much like stika spruce.

I still have the foreplane, but I didn't keep the bin of 2-bolt clamps.

Matt Colie
Lifelong Waterman, Licensed Mariner and Congenital Sailor



Hess cutter 56 wrote:
Hello Ray I have been using Resorcinol from CP Adhesives [ 740]
763-2886 I like the way it mixes compared to the Dap Resorcinol .
Resorcinol has a 60 year history proving longevity and durability. Not
the case with epoxy! Epoxy came on the market in the late 70s.
Resorcinol has better performance in parts that tend to build up alot
of heat [ Like a mast standing in the sun all day] This spar builder
Matt may be old. But how long has he used Epoxy to build spars. Let me
know how you make out CW